TWI439553B - Medium-carbon steel plate for cold working and producing method thereof - Google Patents

Medium-carbon steel plate for cold working and producing method thereof Download PDF

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TWI439553B
TWI439553B TW100133935A TW100133935A TWI439553B TW I439553 B TWI439553 B TW I439553B TW 100133935 A TW100133935 A TW 100133935A TW 100133935 A TW100133935 A TW 100133935A TW I439553 B TWI439553 B TW I439553B
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steel sheet
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cold working
carbide
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TW201313921A (en
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Kengo Takeda
Masayuki Abe
Yasushi Tsukano
Takashi Aramaki
Shinichi Yamaguchi
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Nippon Steel & Sumitomo Metal Corp
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冷加工用中碳鋼板及其製造方法Medium carbon steel plate for cold working and manufacturing method thereof 發明領域Field of invention

本發明係有關於一種具有良好的冷加工性，並且在由高頻淬火所代表之熱處理時間很短的淬火處理中，亦可提高強度之冷加工用中碳鋼板及其製造方法。The present invention relates to a medium carbon steel sheet for cold working and a method for producing the same, which have good cold workability and can be used for quenching treatment in which the heat treatment time represented by induction hardening is short.

發明背景Background of the invention

中碳鋼板常廣泛使用為鏈、齒輪、離合器、鋸、刀刃等材料。在產品化方面，將材料成形為預定形狀之後，通常會藉由淬火回火之熱處理進行使其硬化之步驟。因此，就中碳鋼板而言，必須加工性及淬火度可同時成立。尤其，由於近年加工技術發達，開始採用可同時施行壓縮加工與拉伸加工及較習知具有更高加工度之成形法，因此對中碳鋼板而言必須可承受嚴密加工的成形性。此外，近年因節能化之需求，有將淬火回火步驟從習知的爐加熱方式變更為高頻加熱方式之趨勢。為因應如上述需求之變化，必須開發一種在冷加工前為軟質且可承受冷加工時之加工，並具有良好的高頻加熱後之淬火度(以下稱為高頻淬火度。又，將高頻加熱後之淬火單稱高頻淬火)之中碳鋼板。Medium carbon steel sheets are often widely used as materials such as chains, gears, clutches, saws, and blades. In terms of productization, after the material is formed into a predetermined shape, the step of hardening is usually performed by heat treatment by quenching and tempering. Therefore, in the case of a medium carbon steel sheet, workability and hardenability must be established at the same time. In particular, in recent years, processing technology has been developed, and a molding method capable of simultaneously performing compression processing and drawing processing and having a higher degree of workability has been used. Therefore, it is necessary for a medium carbon steel sheet to withstand the formability of strict processing. In addition, in recent years, there has been a trend to change the quenching and tempering step from the conventional furnace heating method to the high frequency heating method due to the demand for energy saving. In order to respond to changes in the above requirements, it is necessary to develop a process that is soft before cold working and can withstand cold working, and has good quenching degree after high frequency heating (hereinafter referred to as high frequency hardening degree. Further, high frequency heating After quenching, single-frequency induction hardening) medium carbon steel plate.

先前技術文獻Prior technical literature 專利文獻Patent literature

專利文獻1：日本國特開平11-80884號公報Patent Document 1: Japanese Patent Laid-Open No. 11-80884

專利文獻2：日本國特開平9-268344號公報Patent Document 2: Japanese Patent Publication No. 9-268344

專利文獻3：日本國特開2001-329333號公報Patent Document 3: Japanese Patent Laid-Open Publication No. 2001-329333

專利文獻4：日本國特開2001-355047號公報Patent Document 4: Japanese Patent Laid-Open Publication No. 2001-355047

習知，就中碳鋼板之加工性與高頻淬火度之關係雖已有進行諸多的調查(例如參考專利文獻1~4)，但，尚未有報告指出具有良好的冷加工性且可在100℃/秒以上之加熱速度充分確保淬火度之例。Conventionally, although there have been many investigations on the relationship between the processability of medium carbon steel sheets and the high-frequency quenching degree (for example, refer to Patent Documents 1 to 4), there has not been reported that it has good cold workability and can be used at 100 ° C. The heating rate of /sec or more is sufficient to ensure the degree of hardening.

例如，專利文獻1中有揭示一種由C：0.1~0.8質量%、S：0.01質量%以下之亞共析鋼所構成之中高碳鋼板。在該中高碳鋼板，係以碳化物球化率在90%以上的方式將碳化物分散在肥粒鐵中，且使平均碳化物粒徑為0.4~1.0μm，並視需求將肥粒鐵晶粒徑長調整在20μm以上。但，在該中高碳鋼板，雖可藉由如上述適當地控制碳化物之形態並改善局部延性來改善伸張凸緣性，但壓縮加工與拉伸加工之兩加工特性卻不夠充分。For example, Patent Document 1 discloses a high carbon steel sheet composed of a hypoeutectoid steel of C: 0.1 to 0.8% by mass and S: 0.01% by mass or less. In the medium-high carbon steel sheet, the carbide is dispersed in the ferrite iron in such a manner that the carbide spheroidization ratio is 90% or more, and the average carbide particle diameter is 0.4 to 1.0 μm, and the ferrite core crystal crystal is required as needed. The particle size is adjusted to be longer than 20 μm. However, in the medium-high carbon steel sheet, although the stretch flangeability can be improved by appropriately controlling the form of the carbide and improving the local ductility as described above, the two processing characteristics of the compression processing and the drawing processing are insufficient.

又，專利文獻2中有揭示一種具有良好的冷鍛性且具有良好的靜態強度或彎曲疲勞強度及滾動接觸疲勞強度之高強度高頻淬火用鋼。在該高頻淬火用鋼，並未明確顯示用以獲得鍛造性所需要的具體碳化物形狀，且淬火時之加熱溫度或保持時間等具體條件亦不明確。Further, Patent Document 2 discloses a high-strength induction hardening steel which has good cold forgeability and has good static strength, bending fatigue strength and rolling contact fatigue strength. In the steel for induction hardening, the specific carbide shape required for obtaining forgeability is not clearly shown, and specific conditions such as heating temperature or holding time at the time of quenching are not clear.

又，專利文獻3中雖有揭示一種具有良好的冷鍛性且臨界鍛粗率很高的高頻淬火用鋼，但淬火時之加熱溫度或保持時間等具體條件並未明確顯示，且實際上是否具有良好的淬火度亦不明確。Further, Patent Document 3 discloses a steel for induction hardening which has good cold forgeability and a high critical forging ratio, but specific conditions such as heating temperature or holding time at the time of quenching are not clearly shown, and actually It is also unclear whether it has a good degree of hardening.

此外，專利文獻4中有揭示一種具有良好的冷加工性及高頻淬火度之高碳鋼管。該高碳鋼管係適用在受型鍛或擴管等局部延性所支配之加工法，然而，就本發明之對象之打孔、擠壓、彎曲、凸出成形、鍛粗、引縮、及押出成形等冷鍛性而言不夠充分。Further, Patent Document 4 discloses a high carbon steel pipe having good cold workability and high frequency hardening. The high carbon steel pipe is suitable for processing by local ductility such as swaging or pipe expansion, however, the object of the present invention is perforating, extruding, bending, projecting, forging, shrinking, and extruding. Cold forgeability such as forming is not sufficient.

本發明作為對象之冷加工為打孔、擠壓、彎曲、凸出成形、鍛粗、引縮、及押出成形等各種加工，在該等加工時，會受到嚴密的壓縮及伸張處理。在對中碳鋼板適用前述冷加工時，肥粒鐵相與碳化物之間會產生因界面剝離所造成的龜裂，該龜裂並傳播而生成裂痕。因此，為使在加工時防止該界面剝離，成分之調整及碳化物之形態控制相當重要。The cold working as the object of the present invention is various processes such as punching, pressing, bending, projecting, forging, shrinking, and extrusion forming, and in such processing, it is subjected to strict compression and stretching treatment. When the above-described cold working is applied to the center carbon steel sheet, cracks due to interfacial peeling occur between the ferrite grain iron phase and the carbide, and the crack propagates and propagates to generate cracks. Therefore, in order to prevent peeling of the interface during processing, adjustment of components and control of morphology of carbides are important.

又，經冷加工之材料多施有淬火處理，在熱處理時間很短的高頻淬火處理中，在加熱期間材料中之碳化物無法充分熔解而難以獲得穩定的淬火度。因此，為以高頻淬火使碳化物可充分熔解，材料之碳化物之形態控制相當重要。Further, the cold-worked material is often subjected to a quenching treatment, and in the induction hardening treatment in which the heat treatment time is short, the carbide in the material is not sufficiently melted during heating, and it is difficult to obtain a stable quenching degree. Therefore, in order to sufficiently melt the carbide by high-frequency quenching, it is important to control the form of the carbide of the material.

然而，目前為止，對中碳鋼板適用冷加工並進行高頻淬火之問題點尚不明確。However, the problem of applying cold working and high frequency quenching to medium carbon steel sheets has not been known so far.

而，在本發明中，中碳鋼板係表示C在0.30%以上在且0.60%以下且板厚在1.6mm以上且在20mm以下之鋼板。In the present invention, the medium carbon steel sheet is a steel sheet having a C of 0.30% or more and 0.60% or less and a sheet thickness of 1.6 mm or more and 20 mm or less.

有鑒於上述實際情況，本發明之目的在於提供一種具有良好的冷加工性且在高頻淬火處理中亦具有充分的淬火硬化能之良好高頻淬火度的中碳鋼板及其製造方法。In view of the above circumstances, an object of the present invention is to provide a medium carbon steel sheet which has good cold workability and which has good quench hardenability in a high-frequency quenching treatment, and a method for producing the same.

本發明人等就達成上述目的之手法進行精密的研究。其結果發現可提供一種中碳鋼板，其除了鋼板之成分組成之調整以外，還可藉由滿足預定條件的方式，控制碳化物之平均徑長及碳化物之球化率，使冷加工時之硬度呈低硬度狀態且具有良好的冷加工性，並且在平均加熱速度為100℃/秒以上之高頻淬火處理中亦具有充分的淬火硬化能。The present inventors conducted intensive studies on the method for achieving the above object. As a result, it has been found that a medium carbon steel sheet can be provided which, in addition to the adjustment of the composition of the steel sheet, can control the average diameter of the carbide and the spheroidization rate of the carbide by satisfying predetermined conditions, so that the hardness during cold working can be achieved. It has a low hardness state and good cold workability, and also has sufficient quench hardenability in the induction hardening treatment at an average heating rate of 100 ° C /sec or more.

本發明係依據上述見解所構成者，其主旨如以下所述。The present invention is based on the above findings, and the gist thereof is as follows.

(1)本發明之一態樣之冷加工用中碳鋼板係，當進行以100℃/秒之平均加熱速度升溫後，於1000℃下保持10秒，在以200℃/秒之平均冷卻速度急速冷卻至室溫之高頻淬火時，硬度成為500HV以上且在900HV以下者。前述冷加工用中碳鋼板係以質量%計含有：C：0.30~0.60%、Si：0.06~0.30%、Mn：0.3~2.0%、P：0.030%以下、S：0.0075%以下、Al：0.005~0.10%、N：0.001~0.01%、及Cr：0.001~0.10%，剩餘部分係由Fe及無法避免之雜質所構成。且，碳化物之平均徑長d在0.6μm以下，碳化物之球化率p在70%以上且小於90%，又，前述碳化物之平均徑長dμm與前述碳化物之球化率p%滿足d≦0.04×p-2.6。(1) A medium carbon steel sheet for cold working according to an aspect of the present invention is heated at an average heating rate of 100 ° C / sec, maintained at 1000 ° C for 10 seconds, and rapidly cooled at an average cooling rate of 200 ° C / sec. When the temperature is cooled to room temperature, the hardness is 500 HV or more and 900 HV or less. The medium carbon steel sheet for cold working contains, by mass%, C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.030% or less, S: 0.0075% or less, and Al: 0.005. 0.10%, N: 0.001 to 0.01%, and Cr: 0.001 to 0.10%, and the remainder consists of Fe and unavoidable impurities. Further, the average diameter d of the carbide is 0.6 μm or less, the spheroidization ratio p of the carbide is 70% or more and less than 90%, and the average diameter of the carbide is d μm and the spheroidization ratio of the carbide is p%. Satisfy d≦0.04×p-2.6.

(2)上述(1)中記載之冷加工用中碳鋼板，以質量%計更含有：Ni：0.01~0.5%、Cu：0.05~0.5%、Mo：0.01~0.5%、Nb：0.01~0.5%、Ti：0.001~0.05%、V：0.01~0.5%、Ta：0.01~0.5%、B：0.001~0.01%、W：0.01~0.5%、Sn：0.003~0.03%、Sb：0.003~0.03%、及As：0.003~0.03%之1種以上。(2) The medium carbon steel sheet for cold working described in the above (1) further contains, by mass%, Ni: 0.01 to 0.5%, Cu: 0.05 to 0.5%, Mo: 0.01 to 0.5%, and Nb: 0.01 to 0.5%. Ti: 0.001~0.05%, V: 0.01~0.5%, Ta: 0.01~0.5%, B: 0.001~0.01%, W: 0.01~0.5%, Sn: 0.003~0.03%, Sb: 0.003~0.03%, And As: one or more of 0.003 to 0.03%.

(3)在上述(2)中記載之冷加工用中碳鋼板中，Cr量[Cr]與Mo量[Mo]滿足[Cr]+[Mo]/10<0.10亦可。(3) In the medium carbon steel sheet for cold working described in the above (2), the amount of Cr [Cr] and the amount of Mo [Mo] may satisfy [Cr] + [Mo]/10 < 0.10.

(4)在上述(1)或(2)中記載之冷加工用中碳鋼板中，冷加工前之硬度在120HV以上且小於170HV亦可。(4) In the medium carbon steel sheet for cold working described in the above (1) or (2), the hardness before cold working may be 120 HV or more and less than 170 HV.

(5)上述(1)或(2)中記載之冷加工用中碳鋼板，係於至少一面更具有表面處理皮膜，該表面處理皮膜則包含：起因於以包含金屬成分X之Si-O-X表示之矽醇鍵結之成分、耐熱樹脂、無機酸鹽及潤滑劑之各成分。且，該表面處理皮膜在膜厚方向具有前述各成分之濃度梯度，且在靠近前述表面處理皮膜與前述冷加工用中碳鋼板之界面，依序具有密接層、基底層、及潤滑劑層等3層。前述密接層在前述3層中含有最多量之起因於前述矽醇鍵結之成分，並具有0.1nm以上且100nm以下之厚度。前述基底層在前述3層中含有最多量之前述耐熱樹脂及前述無機酸鹽，且相對於100質量份之前述耐熱樹脂，含有0.01質量份以上且10質量份以下之前述無機酸鹽，並具有0.1μm以上且15μm以下之厚度。前述潤滑劑層在前述3層中含有最多量之前述潤滑劑，並具有0.1μm以上且10μm以下之厚度。前述基底層之厚度相對於前述潤滑劑層之厚度之比值在0.2以上且在10以下亦可。(5) The medium carbon steel sheet for cold working according to (1) or (2) above which has a surface treatment film on at least one side, the surface treatment film comprising: represented by Si-OX containing a metal component X. A component of a sterol bond, a heat resistant resin, a mineral acid salt, and a lubricant. Further, the surface treatment film has a concentration gradient of each of the above components in the film thickness direction, and has an adhesion layer, a base layer, and a lubricant layer in the vicinity of the interface between the surface treatment film and the medium carbon steel sheet for cold working. Floor. The adhesion layer contains a maximum amount of a component derived from the sterol bond in the three layers, and has a thickness of 0.1 nm or more and 100 nm or less. The base layer contains the most the amount of the above-mentioned heat-resistant resin and the above-mentioned inorganic acid salt in the above-mentioned three layers, and contains 0.01 parts by mass or more and 10 parts by mass or less of the above-mentioned inorganic acid salt with respect to 100 parts by mass of the heat resistant resin, and has A thickness of 0.1 μm or more and 15 μm or less. The lubricant layer contains the most amount of the lubricant in the above three layers, and has a thickness of 0.1 μm or more and 10 μm or less. The ratio of the thickness of the underlayer to the thickness of the lubricant layer is 0.2 or more and 10 or less.

(6)在上述(5)中記載之冷加工用中碳鋼板中，前述無機酸鹽可為選自於由磷酸鹽、硼酸鹽、矽酸鹽、鉬酸鹽及鎢酸鹽所構成之群組中之至少1種化合物。(6) The medium carbon steel sheet for cold working according to (5), wherein the inorganic acid salt may be selected from the group consisting of phosphates, borates, citrates, molybdates, and tungstates. At least one compound.

(7)在上述(5)中記載之冷加工用中碳鋼板中，前述耐熱樹脂可為選自於由聚醯亞胺樹脂、聚酯樹脂、環氧樹脂及氟樹脂所構成之群組中之至少1種樹脂。(7) In the medium carbon steel sheet for cold working according to the above (5), the heat resistant resin may be selected from the group consisting of a polyimide resin, a polyester resin, an epoxy resin, and a fluororesin. At least one resin.

(8)在上述(5)中記載之冷加工用中碳鋼板中，前述潤滑劑可為選自於由聚四氟乙烯、二硫化鉬、二硫化鎢、氧化鋅及石墨所構成之群組中之至少1種化合物。(8) In the medium carbon steel sheet for cold working according to (5), the lubricant may be selected from the group consisting of polytetrafluoroethylene, molybdenum disulfide, tungsten disulfide, zinc oxide, and graphite. At least one compound.

(9)本發明之一態樣之冷加工用中碳鋼板之製造方法包含下列步驟：第1步驟，係將具有上述(1)或(2)中記載之成分組成之鑄片保持在1050℃以上且在1300℃以下者；第2步驟，係在該第1步驟後，對前述鑄片進行在750℃以上且1000℃以下結束軋延之熱軋而獲得鋼板者；第3步驟，係在該第2步驟後，以20℃/秒以上且50℃/秒以下之第一平均冷卻速度，將前述鋼板冷卻至500℃以上且700℃以下之第一冷卻結束溫度者；第4步驟，係在該第3步驟後，以5℃/秒以上且30℃/秒以下之第二平均冷卻速度，將將前述鋼板冷卻至400℃以上且較前述第一冷卻結束溫度低50℃之溫度以下之第二冷卻結束溫度，而進行捲取者；第5步驟，係在該第4步驟後，以將400℃以上且前述第二冷卻結束溫度以下之時間限制在30小時以下的方式，保持前述鋼板者；及第6步驟，係在該第5步驟後，將前述鋼板加熱至600℃以上且Ac1 點-10℃以下，並保持5小時以上且小於100小時而進行退火者。(9) A method for producing a medium carbon steel sheet for cold working according to an aspect of the present invention comprises the following steps: the first step of maintaining a cast piece having the composition described in the above (1) or (2) at 1050 ° C or higher In the second step, after the first step, the cast piece is subjected to hot rolling at 750 ° C or higher and 1000 ° C or lower to obtain a steel sheet; and the third step is After the second step, the steel sheet is cooled to a first cooling end temperature of 500 ° C or more and 700 ° C or less at a first average cooling rate of 20 ° C /sec or more and 50 ° C / sec or less; the fourth step is After the third step, the steel sheet is cooled to a temperature lower than 400 ° C and lower than a temperature lower than the first cooling end temperature by 50 ° C at a second average cooling rate of 5 ° C / sec or more and 30 ° C / sec or less. The second step is to perform the winding, and the fifth step is to maintain the steel sheet by limiting the time of 400 ° C or higher and the second cooling end temperature to 30 hours or less after the fourth step. And the sixth step, after the fifth step, the steel sheet is And heated to above 600 ℃ the A c1 point -10 ℃, and 5 hours or more and less than 100 hours were annealed.

(10)在上述(9)中記載之冷加工用中碳鋼板之製造方法中，在前述第6步驟中，在400℃以下之露點低於-20℃，在超過400℃之露點低於-40℃，且氫濃度在95%以上亦可。(10) In the method for producing a medium carbon steel sheet for cold working according to the above (9), in the sixth step, the dew point at 400 ° C or lower is lower than -20 ° C, and the dew point exceeding 400 ° C is lower than -40 °C, and the hydrogen concentration may be 95% or more.

(11)在上述(9)或(10)中記載之冷加工用中碳鋼板之製造方法中，於前述第6步驟之後，將包含水溶性矽烷耦合劑、水溶性無機酸鹽、水溶性耐熱樹脂及潤滑劑之水系表面處理液，塗佈到前述冷加工用中碳鋼板之至少一面，並使前述表面處理液乾燥，而在前述冷加工用中碳鋼板之至少一面形成前述表面處理皮膜亦可。(11) The method for producing a medium carbon steel sheet for cold working according to (9) or (10) above, after the sixth step, comprising a water-soluble decane coupling agent, a water-soluble inorganic acid salt, and a water-soluble heat-resistant resin The water-based surface treatment liquid of the lubricant may be applied to at least one surface of the medium-carbon steel sheet for cold working, and the surface treatment liquid may be dried, and the surface treatment film may be formed on at least one surface of the medium-carbon steel sheet for cold working.

依據本發明，可提供一種冷加工用中碳鋼板及其製造方法，其在冷加工前為低硬度(軟質)且具有良好的壓縮加工與拉伸加工之兩種冷加工特性，並且在冷加工後之平均加熱速度為100℃/秒以上之高頻淬火處理中，亦可具有充分的淬火硬化能，可圖謀同時成立可確保高強度之冷加工性及高頻淬火度。According to the present invention, it is possible to provide a medium carbon steel sheet for cold working and a method for producing the same, which have low hardness (softness) before cold working and have good cold working characteristics of compression processing and drawing processing, and average heating after cold working. In the high-frequency quenching treatment at a speed of 100 ° C /sec or more, sufficient quench hardening energy can be obtained, and cold workability and high-frequency hardenability which can ensure high strength can be simultaneously established.

圖式簡單說明Simple illustration

第1圖係顯示碳化物之平均徑長及碳化物之球化率波及淬火硬度及冷加工性之影響之圖。Fig. 1 is a graph showing the influence of the average diameter of carbides and the spheroidization rate of carbides on quenching hardness and cold workability.

第2圖係顯示Si量與冷加工後之碳化物界面及粒內龜裂數之關係圖。Fig. 2 is a graph showing the relationship between the amount of Si and the number of carbide interfaces and the number of cracks in the grains after cold working.

第3圖係顯示[Cr]+[Mo]/10與淬火硬度之關係圖。Fig. 3 is a graph showing the relationship between [Cr] + [Mo]/10 and quenching hardness.

第4圖係顯示碳化物之球化率與碳化物起點之龜裂數之關係圖。Figure 4 is a graph showing the relationship between the spheroidization rate of carbides and the number of cracks at the carbide starting point.

第5圖係顯示S量與硫化物起點之龜裂數之關係圖。Fig. 5 is a graph showing the relationship between the amount of S and the number of cracks at the starting point of the sulfide.

第6圖係顯示本發明之一實施形態之變形例之冷加工用鋼板構成之示意縱剖面圖。Fig. 6 is a schematic longitudinal cross-sectional view showing the structure of a steel sheet for cold working according to a modification of the embodiment of the present invention.

第7A圖係說明穿刺試驗方法之概略圖。Fig. 7A is a schematic view showing the puncture test method.

第7B圖係說明穿刺試驗片之加工前形狀與加工後形狀之概略圖。Fig. 7B is a schematic view showing the shape before processing and the shape after processing of the puncture test piece.

第8圖係顯示本發明之冷加工用中碳鋼板之製造方法之概略之流程圖。Fig. 8 is a flow chart showing the outline of a method for producing a medium carbon steel sheet for cold working according to the present invention.

用以實施發明之形態Form for implementing the invention

以下將詳細說明本發。The present invention will be described in detail below.

首先，說明本發明之一實施形態之冷加工用鋼板(以下有時會稱為「本實施形態之鋼板」)之成分組成之限定理由。而，以下，「%」表示「質量%」。First, the reason for limiting the component composition of the steel sheet for cold working (hereinafter referred to as "the steel sheet of the present embodiment") according to an embodiment of the present invention will be described. However, below, "%" means "% by mass".

C：0.30~0.60%C: 0.30~0.60%

C為用以確保鋼板之淬火強度很重要的元素。所以，會在鋼中添加0.30%以上之C以確保所需之強度。當C量小於0.30%，淬火度會降低且無法獲得作為機械結構用之高強度鋼板的強度，因此C量之下限為0.30%。若C量超過0.60%，作為損壞起點而起作用之碳化物的比例將增加且冷加工性降低，因此C量之上限為0.60%。在必須確保更好的淬火度之情況下，C量之下限以0.35%為佳，0.37%較佳，0.40%最佳。又，為使較易控制碳化物之形態，C量之上限以0.55%為佳，0.52%較佳，0.50%最佳。C is an element important for ensuring the quenching strength of the steel sheet. Therefore, 0.30% or more of C is added to the steel to ensure the required strength. When the amount of C is less than 0.30%, the degree of hardening is lowered and the strength of the high-strength steel sheet for mechanical structure cannot be obtained, so the lower limit of the amount of C is 0.30%. When the amount of C exceeds 0.60%, the proportion of the carbide acting as the starting point of the damage increases and the cold workability decreases, so the upper limit of the amount of C is 0.60%. In the case where it is necessary to ensure a better degree of quenching, the lower limit of the amount of C is preferably 0.35%, preferably 0.37%, and most preferably 0.40%. Further, in order to make it easier to control the form of the carbide, the upper limit of the amount of C is preferably 0.55%, more preferably 0.52%, and most preferably 0.50%.

Si：0.06~0.30%Si: 0.06~0.30%

Si係作為脫氧劑起作用，係用以抑制加工時之肥粒鐵與碳化物之間之界面剝離、且有助於淬火度之提升之元素。當Si量小於0.06%將無法獲得該添加效果，因此Si量之下限為0.06%。另一方面，若Si量超過0.30%，由於固溶強化會使肥粒鐵相之龜裂生成頻率(粒內龜裂生成頻率)增加，且熱軋時之鏽皮缺陷會使表面性質狀態劣化，因此Si量之上限為0.30%。為使肥粒鐵與碳化物之間之界面剝離更加減低，Si量之下限以0.10%為佳，0.13%較佳，0.15%最佳。又，為使在肥粒鐵相之龜裂(粒內龜裂)的產生更加減低，Si量之上限以0.26%為佳。The Si system acts as a deoxidizer and is an element for suppressing the interface peeling between the ferrite iron and the carbide during processing and contributing to the improvement of the quenching degree. When the amount of Si is less than 0.06%, the addition effect cannot be obtained, so the lower limit of the amount of Si is 0.06%. On the other hand, if the amount of Si exceeds 0.30%, the crack formation frequency (intragranular crack generation frequency) of the ferrite grain iron phase increases due to solid solution strengthening, and the surface property state deteriorates due to the scale defect during hot rolling. Therefore, the upper limit of the amount of Si is 0.30%. In order to further reduce the interfacial peeling between the ferrite iron and the carbide, the lower limit of the Si amount is preferably 0.10%, preferably 0.13%, and 0.15%. Further, in order to further reduce the occurrence of cracks in the ferrite phase (intragranular crack), the upper limit of the amount of Si is preferably 0.26%.

Mn：0.3~2.0%Mn: 0.3~2.0%

Mn係作為脫氧劑起作用並有助於淬火度之提升之元素。當Mn量小於0.3%將無法獲得該添加效果，因此Mn量之下限為0.3%。若Mn量超過2.0%，則高頻加熱時之碳化物之熔解會延遲且淬火度(淬火硬度)降低，因此Mn量之上限為2.0%。為使更加提高淬火度，Mn量之下限以0.5%為佳，0.55%較佳，0.65%或0.73%最佳。又，若欲更加確保高頻淬火度，Mn量之上限以1.6%為佳，1.4%較佳，1.2%或1.0%最佳。Mn acts as a deoxidizer and contributes to the improvement of hardenability. When the amount of Mn is less than 0.3%, the effect of addition cannot be obtained, and therefore the lower limit of the amount of Mn is 0.3%. When the amount of Mn exceeds 2.0%, the melting of the carbide during high-frequency heating is delayed and the degree of quenching (quenching hardness) is lowered. Therefore, the upper limit of the amount of Mn is 2.0%. In order to further increase the degree of quenching, the lower limit of the amount of Mn is preferably 0.5%, preferably 0.55%, 0.65% or 0.73%. Further, in order to further ensure the induction hardening degree, the upper limit of the amount of Mn is preferably 1.6%, preferably 1.4%, and 1.2% or 1.0%.

P：0.030%以下P: 0.030% or less

P係固溶強化元素，為有助於鋼板強度之元素。一旦鋼中含有過多的P，會使韌性降低，因此P量之上限為0.030%。P為無法避免之雜質。一旦將P量減低至小於0.005%，會使精鍊成本上昇，因此無須將P量減低至小於0.005%。在有需要較良好的韌性之情況下，P量之上限以0.020%為佳。P is a solid solution strengthening element and is an element that contributes to the strength of the steel sheet. Once the steel contains too much P, the toughness is lowered, so the upper limit of the amount of P is 0.030%. P is an unavoidable impurity. Once the amount of P is reduced to less than 0.005%, the refining cost is increased, so that it is not necessary to reduce the amount of P to less than 0.005%. In the case where there is a need for better toughness, the upper limit of the amount of P is preferably 0.020%.

S：0.0075%以下S: 0.0075% or less

S為形成非金屬介在物(硫化物)且使加工性及熱處理後之韌性降低之原因，因此S量之上限在0.0075%以下。第5圖中顯示S量與冷加工時硫化物作為起點起作用之龜裂(硫化物起點之龜裂)數之關係。如從該第5圖可知，一旦S量在0.0075%以下，硫化物起點之龜裂數會大幅降低。又，S為無法避免之雜質。一旦將S量減低至小於0.0001%，會使精鍊成本大幅上昇，因此無須將S量減低至小於0.0001%或0.001%以下。又，在有需要確保較高的加工性及韌性之情況下，S量之上限以0.007%為佳，0.005%較佳。S is a cause of forming a non-metallic intervening substance (sulfide) and reducing workability and toughness after heat treatment. Therefore, the upper limit of the amount of S is 0.0075% or less. Fig. 5 shows the relationship between the amount of S and the number of cracks (cracks of the sulfide starting point) at which the sulfide acts as a starting point during cold working. As can be seen from Fig. 5, when the amount of S is 0.0075% or less, the number of cracks at the sulfide starting point is greatly lowered. Also, S is an unavoidable impurity. Once the amount of S is reduced to less than 0.0001%, the refining cost is greatly increased, so that it is not necessary to reduce the amount of S to less than 0.0001% or less. Further, in the case where it is necessary to ensure high workability and toughness, the upper limit of the amount of S is preferably 0.007%, and 0.005% is preferable.

Al：0.005~0.10%Al: 0.005~0.10%

Al係作為脫氧劑起作用，為有助於N之固定之元素。當Al量小於0.005%，將無法充分獲得該添加效果，因此Al量之下限為0.005%。一旦Al量超過0.10%，上述添加效果會飽和且易產生表面缺陷，因此Al量之上限為0.10%。為使更加充分固定N，Al量之下限以0.01%為佳。又，為使更可確實抑制表面缺陷之產生，將Al量之上限設為0.07%或0.05%亦可。Al acts as a deoxidizer and is an element that contributes to the fixation of N. When the amount of Al is less than 0.005%, the effect of addition cannot be sufficiently obtained, and therefore the lower limit of the amount of Al is 0.005%. When the amount of Al exceeds 0.10%, the above-mentioned addition effect is saturated and surface defects are liable to occur, so the upper limit of the amount of Al is 0.10%. In order to more sufficiently fix N, the lower limit of the amount of Al is preferably 0.01%. Further, in order to more reliably suppress the occurrence of surface defects, the upper limit of the amount of Al may be 0.07% or 0.05%.

N：0.001~0.01%N: 0.001~0.01%

N為形成氮化物之元素。一旦在彎曲型連續鑄造之鑄片彎曲矯正時析出氮化物，鑄片有可能會產生裂痕，因此N量之上限為0.01%。N為無法避免之雜質。鋼中之N量愈少愈好，然而，一旦將N量減低至小於0.0010%，精鍊成本將會增加，因此N量之下限為0.0010%。為使精鍊成本更加減低，N量之下限以0.002%為佳。在必需進一步抑制氮化物之產生或粗大化的情況下，N量之上限以0.008%為佳，0.006%較佳。N is an element forming a nitride. Once the nitride is precipitated during the bending correction of the curved continuous casting, the cast piece may be cracked, so the upper limit of the amount of N is 0.01%. N is an unavoidable impurity. The smaller the amount of N in the steel, the better. However, once the amount of N is reduced to less than 0.0010%, the refining cost will increase, so the lower limit of the amount of N is 0.0010%. In order to further reduce the refining cost, the lower limit of the amount of N is preferably 0.002%. In the case where it is necessary to further suppress the generation or coarsening of the nitride, the upper limit of the amount of N is preferably 0.008%, preferably 0.006%.

Cr：0.001~0.10%Cr: 0.001~0.10%

Cr為提高高頻加熱時之碳化物穩定性之元素。若因對鋼中添加Cr而使Cr量超過0.10%，會大幅提高碳化物之穩定性並抑制高頻加熱時之碳化物之熔解而使淬火度降低。所以，Cr量之上限為0.10%。雖然鋼中之Cr量愈少愈可提高高頻淬火度，但若將Cr量減低至0.001%以下，精鍊成本會大幅增加，因此Cr量之下限為0.001%。為使進一步增加高頻加熱時之碳化物之熔解速度，Cr量之上限以0.080%為佳，0.070%較佳。又，為使進一步減低精鍊成本，Cr量之下限以0.010%為佳。Cr is an element that improves the stability of carbides during high-frequency heating. When the amount of Cr is more than 0.10% by adding Cr to the steel, the stability of the carbide is greatly improved, and the melting of the carbide at the time of high-frequency heating is suppressed, and the degree of hardening is lowered. Therefore, the upper limit of the amount of Cr is 0.10%. Although the amount of Cr in the steel is smaller, the induction hardening degree can be increased. However, if the amount of Cr is reduced to 0.001% or less, the refining cost is greatly increased, so the lower limit of the amount of Cr is 0.001%. In order to further increase the melting rate of the carbide at the time of high-frequency heating, the upper limit of the amount of Cr is preferably 0.080%, and preferably 0.070%. Further, in order to further reduce the refining cost, the lower limit of the amount of Cr is preferably 0.010%.

為強化鋼板之機械特性，亦可在鋼中添加所需量之Ni、Cu、及Mo之1種以上。In order to strengthen the mechanical properties of the steel sheet, one or more of Ni, Cu, and Mo may be added to the steel.

Ni：0.01~0.5%Ni: 0.01~0.5%

Ni為有助於提升韌性及淬火度之元素。當Ni量小於0.01%，將無法獲得該添加效果，因此Ni量之下限為0.01%。一旦Ni量超過0.5%，則上述效果飽和且成本增加，因此Ni量之上限為0.5%。從強度之觀點看來，Ni量之下限以0.05%為佳。又，從成本之觀點看來，Ni量之上限以0.3%為佳，0.2%較佳，0.15%最佳。Ni is an element that contributes to the improvement of toughness and hardenability. When the amount of Ni is less than 0.01%, the addition effect cannot be obtained, and therefore the lower limit of the amount of Ni is 0.01%. When the amount of Ni exceeds 0.5%, the above effect is saturated and the cost is increased, so the upper limit of the amount of Ni is 0.5%. From the viewpoint of strength, the lower limit of the amount of Ni is preferably 0.05%. Further, from the viewpoint of cost, the upper limit of the amount of Ni is preferably 0.3%, more preferably 0.2%, and most preferably 0.15%.

Cu：0.05~0.5%Cu: 0.05~0.5%

Cu係有助於淬火度之確保之元素。當Cu量小於0.05%，該添加效果會不夠充分，因此Cu量之下限為0.05%。一旦Cu量超過0.5%，硬度會過度增加且使冷加工性劣化，因此Cu量之上限為0.5%。從強度之觀點看來，Cu量之下限以0.08%為佳。又，從加工性觀點看來，Cu量之上限以0.3%為佳，0.2%較佳，0.15%最佳。Cu is an element that contributes to the assurance of hardenability. When the amount of Cu is less than 0.05%, the effect of addition may be insufficient, and therefore the lower limit of the amount of Cu is 0.05%. When the amount of Cu exceeds 0.5%, the hardness is excessively increased and the cold workability is deteriorated, so the upper limit of the amount of Cu is 0.5%. From the viewpoint of strength, the lower limit of the amount of Cu is preferably 0.08%. Further, from the viewpoint of workability, the upper limit of the amount of Cu is preferably 0.3%, more preferably 0.2%, and most preferably 0.15%.

Mo：0.01~0.5%Mo: 0.01~0.5%

Mo係有助於淬火度之提升之元素。當Mo量小於0.01%，該添加效果很小，因此Mo量之下限為0.01%。一旦Mo量超過0.5%，會有諸多的Mo系碳化物析出至鋼中。在高頻淬火中，因Mo系碳化物無法充分熔解且材料之淬火度會降低，因此Mo量之上限為0.5%。在需要較高的淬火度之情況下，Mo量之上限以0.3%為佳，0.1%較佳。Mo is an element that contributes to the improvement of hardenability. When the amount of Mo is less than 0.01%, the effect of addition is small, so the lower limit of the amount of Mo is 0.01%. When the amount of Mo exceeds 0.5%, many Mo-based carbides are precipitated into the steel. In the induction hardening, since the Mo-based carbide cannot be sufficiently melted and the quenching degree of the material is lowered, the upper limit of the Mo amount is 0.5%. In the case where a higher degree of quenching is required, the upper limit of the amount of Mo is preferably 0.3%, and 0.1% is preferred.

為進一步強化鋼板之機械特性，可在鋼中添加所需量之Nb、V、Ta、B、及W之1種以上。In order to further strengthen the mechanical properties of the steel sheet, one or more of the required amounts of Nb, V, Ta, B, and W may be added to the steel.

Nb：0.01~0.5%Nb: 0.01~0.5%

Nb係形成碳氮化物且有助於防止晶粒粗大化及改善韌性之元素。當Nb量小於0.01%，該添加效果會無法充分顯現，因此Nb量之下限為0.01%。一旦Nb量超過0.5%，上述添加效果便會飽和，因此Nb量之上限為0.5%。為使有效率地利用上述添加效果，Nb量以0.07~0.4%為佳。視需求，可將Nb量之下限限制在0.09%或0.14%，並將上限限制在0.35%或0.3%。Nb forms an element of carbonitride and contributes to prevention of grain coarsening and improvement of toughness. When the amount of Nb is less than 0.01%, the effect of addition may not be sufficiently exhibited, so the lower limit of the amount of Nb is 0.01%. Once the amount of Nb exceeds 0.5%, the above-mentioned addition effect is saturated, so the upper limit of the amount of Nb is 0.5%. In order to utilize the above additive effect efficiently, the amount of Nb is preferably 0.07 to 0.4%. The lower limit of the amount of Nb can be limited to 0.09% or 0.14%, and the upper limit is limited to 0.35% or 0.3%, depending on the demand.

Ti：0.001~0.05%Ti: 0.001~0.05%

Ti係基於N固定之觀點而添加在鋼中，可貢獻於鑄片之脆化抑制及材質之穩定化。將Ti添加於鋼中，一旦Ti量超過0.05%該效果會飽和，若Ti量在0.001%以下則無法獲得該效果。所以，Ti量之範圍在0.001~0.05%。為有效率地利用上述效果，Ti量之上限以0.20%為佳，0.10%較佳，0.06%最佳。Ti is added to steel from the viewpoint of N fixation, and contributes to suppression of embrittlement of the cast piece and stabilization of the material. When Ti is added to steel, the effect is saturated once the amount of Ti exceeds 0.05%, and this effect cannot be obtained if the amount of Ti is 0.001% or less. Therefore, the amount of Ti ranges from 0.001 to 0.05%. In order to utilize the above effects efficiently, the upper limit of the amount of Ti is preferably 0.20%, more preferably 0.10%, and most preferably 0.06%.

V：0.01~0.5%V: 0.01~0.5%

V同於Nb為形成碳氮化物且有助於防止晶粒粗大化及改善韌性之元素。當V量小於0.01%，該添加效果很小，因此V量之下限為0.01%。一旦V量超過0.5%，會生成碳化物且使淬火硬度降低，因此V量之上限為0.5%。為有效率地利用上述效果，V量以0.07~0.2%為佳。V is the same as Nb as an element which forms a carbonitride and contributes to prevention of grain coarsening and improvement of toughness. When the amount of V is less than 0.01%, the effect of addition is small, so the lower limit of the amount of V is 0.01%. When the amount of V exceeds 0.5%, carbides are formed and the quenching hardness is lowered, so the upper limit of the amount of V is 0.5%. In order to utilize the above effects efficiently, the amount of V is preferably 0.07 to 0.2%.

Ta：0.01~0.5%Ta: 0.01~0.5%

Ta同於Nb與V為形成碳氮化物且有助於防止晶粒粗大化及改善韌性之元素。當Ta量小於0.01%，該添加效果很小，因此Ta量之下限為0.01%。一旦Ta量超過0.5%，會生成碳化物且使淬火硬度降低，因此Ta量之上限為0.5%。為有效率地利用上述效果，Ta量以0.07~0.2%為佳。Ta is the same as Nb and V as elements which form carbonitrides and contribute to prevention of grain coarsening and improvement of toughness. When the amount of Ta is less than 0.01%, the effect of addition is small, so the lower limit of the amount of Ta is 0.01%. When the amount of Ta exceeds 0.5%, carbides are formed and the quenching hardness is lowered, so the upper limit of the amount of Ta is 0.5%. In order to utilize the above effects efficiently, the amount of Ta is preferably 0.07 to 0.2%.

B：0.001~0.01%B: 0.001~0.01%

B為微量添加且有助於提高淬火度之元素。當B量小於0.001%即無該添加效果，因此B量之下限為0.001%。一旦B量超過0.01%，鑄造性會降低且使B系化合物生成而降低韌性，因此B量之上限為0.01%。在需要更高的淬火度之情況下，B量之下限以0.003%為佳。又，在需要抑制B系化合物之生成的情況下，B量之上限以0.007%為佳，0.005%較佳。B is an element that is added in a small amount and contributes to an improvement in the degree of hardening. When the amount of B is less than 0.001%, there is no such addition effect, so the lower limit of the amount of B is 0.001%. When the amount of B exceeds 0.01%, the castability is lowered and the B-based compound is formed to lower the toughness, so the upper limit of the amount of B is 0.01%. In the case where a higher degree of quenching is required, the lower limit of the amount of B is preferably 0.003%. Further, when it is necessary to suppress the formation of the B-based compound, the upper limit of the amount of B is preferably 0.007%, preferably 0.005%.

W：0.01~0.5%W: 0.01~0.5%

W係有助於鋼板強化之元素。當W量小於0.01%，會無法顯現該添加效果，因此W量之下限為0.01%。一旦W量超過0.5%，會使加工性降低，因此W量之上限為0.5%。從強度之觀點看來，W量之下限以0.04%為佳。從加工性之觀點看來，W量之上限以0.2%為佳。The W system contributes to the strengthening of the steel sheet. When the amount of W is less than 0.01%, the effect of addition cannot be exhibited, and therefore the lower limit of the amount of W is 0.01%. When the amount of W exceeds 0.5%, the workability is lowered, so the upper limit of the amount of W is 0.5%. From the viewpoint of strength, the lower limit of the amount of W is preferably 0.04%. From the viewpoint of workability, the upper limit of the amount of W is preferably 0.2%.

若使用廢鋼作為鋼板原料，無法避免地鋼中可能會混入Sn、Sb、及As之1種以上，但，不論其中何種元素，只要其量在0.03%以下，便不會阻礙高頻淬火度及淬火度。所以，鋼中亦可含有Sn：0.03%以下、Sb：0.03%以下、及As：0.03%以下之1種以上。通常，該等成分係分別作為雜質含有0.003%以上，以少量為佳。If scrap steel is used as the steel sheet material, it is unavoidable that more than one of Sn, Sb, and As may be mixed in the steel. However, regardless of any of the elements, as long as the amount is 0.03% or less, the high-frequency hardening degree is not hindered. And quenching degree. Therefore, the steel may contain one or more of Sn: 0.03% or less, Sb: 0.03% or less, and As: 0.03% or less. Usually, these components are contained as an impurity, respectively, in an amount of 0.003% or more, preferably in a small amount.

雖未規定鋼板中之O量，然而一旦氧化物凝聚並粗大化，便會降低冷加工性，因此O量以在0.0025%以下為佳。O量以少量為佳，然而，技術上難以將無法避免而含有之O量減低至小於0.0001%，因此含有0.0001%以上之O亦無妨。Although the amount of O in the steel sheet is not defined, once the oxide is aggregated and coarsened, the cold workability is lowered, so the amount of O is preferably 0.0025% or less. The amount of O is preferably a small amount. However, it is technically difficult to reduce the amount of O contained in the amount to be less than 0.0001%. Therefore, it is also possible to contain 0.0001% or more of O.

在使用廢鋼作為鋼板之熔製原料的情況下，Zn、與Zr等元素會作為無法避免之雜質而混入，只要在未阻礙鋼板特性之範圍內，上述元素混入於鋼中亦可。而，Zn、與Zr以外之元素亦可在未阻礙鋼板特性的範圍內混入鋼中。When scrap steel is used as a melting raw material of a steel sheet, an element such as Zn or Zr may be mixed as an unavoidable impurity, and the element may be mixed in the steel within a range in which the characteristics of the steel sheet are not inhibited. Further, elements other than Zn and Zr may be mixed into the steel within a range that does not impede the characteristics of the steel sheet.

如上述，Cr及Mo皆可抑制高溫時C從碳化物至母相之供給(固溶)並使淬火度降低。即，Cr會固溶於雪明碳鐵中，並在高頻加熱時抑制C從雪明碳鐵至母相之固溶，使淬火度降低。又，一旦鋼中含有過剩的Mo，便會形成Mo系碳化物。此時，可於高頻加熱時抑制C從該Mo系碳化物至母相之固溶，使淬火度降低。因此，當鋼中含有Cr與Mo時，Cr量[Cr]與Mo量[Mo]宜滿足以下(1)式。As described above, both Cr and Mo can suppress the supply (solid solution) of C from the carbide to the parent phase at a high temperature and lower the degree of hardenability. That is, Cr is solid-solubilized in the stellite carbon iron, and inhibits the solid solution of C from the ferritic carbon to the parent phase at the time of high-frequency heating, thereby lowering the quenching degree. Moreover, once the steel contains excess Mo, Mo-based carbides are formed. At this time, solid solution of C from the Mo-based carbide to the parent phase can be suppressed at the time of high-frequency heating, and the degree of hardening can be lowered. Therefore, when Cr and Mo are contained in the steel, the amount of Cr [Cr] and the amount of Mo [Mo] preferably satisfy the following formula (1).

[Cr]+[Mo]/10<0.10　…(1)[Cr]+[Mo]/10<0.10 ...(1)

如以上，本實施形態之中碳鋼板，具有包含上述基本元素、且剩餘部分由Fe及無法避免之雜質所構成之化學組成；或是具有包含上述基本元素及選自於上述選擇元素之至少1種、且剩餘部分由Fe及無法避免之雜質所構成之化學組成。As described above, in the present embodiment, the carbon steel sheet has a chemical composition including the basic element and the remainder consisting of Fe and an unavoidable impurity, or at least one selected from the above basic elements and selected from the above selected elements. The chemical composition of the remaining part consisting of Fe and unavoidable impurities.

此外，在本實施形態中，除上述成分組成以外，還必需控制碳化物之形態。以下將詳細說明碳化物之形態。Further, in the present embodiment, in addition to the above-described component composition, it is necessary to control the form of the carbide. The form of the carbide will be described in detail below.

即，碳化物之平均徑長在0.6μm以下，碳化物之球化率在70%以上且小於90%，且碳化物之平均徑長d(μm)及碳化物之球化率p(%)滿足下述式(2)。That is, the average diameter of the carbide is 0.6 μm or less, the spheroidization ratio of the carbide is 70% or more and less than 90%, and the average diameter d (μm) of the carbide and the spheroidization ratio p (%) of the carbide. The following formula (2) is satisfied.

d≦0.04×p-2.6　…(2)D≦0.04×p-2.6 ...(2)

就組織(碳化物)之觀察而言，宜使用掃描型電子顯微鏡。以3000倍之倍率在組織觀察面上挑選4處以上含有碳化物500個以上之視野(區域)，測定包含於其區域中之各碳化物之面積。在此，為了抑制因雜訊所造成的測定誤差影響，將面積在0.01μm2 以下之碳化物自評估對象中剔除。將以圓形近似所測定之碳化物之平均面積(面積之平均值)時之直徑(圓相當徑長)，定義為平均徑長(平均碳化物徑長)。將各碳化物之長軸長相對於短軸長之比值(長寬比)在3以上之碳化物定義為針狀碳化物，將該比值在1以上且小於3之碳化物定義為球狀碳化物。又，將球狀碳化物之個數除以全部碳化物之個數之值定義為碳化物之球化率。For the observation of the structure (carbide), a scanning electron microscope is preferably used. Four or more fields (regions) containing more than 500 carbides were selected on the tissue observation surface at a magnification of 3000 times, and the area of each carbide contained in the region was measured. Here, in order to suppress a measurement error due to noise caused by the impact, the evaluation target area is removed from the 2 or less of carbides at 0.01μm. The diameter (circle equivalent diameter) when the average area (area of the area) of the carbides measured by the circular approximation is defined as the average diameter (average carbide diameter). A carbide having a ratio of a major axis length of each carbide to a minor axis length (aspect ratio) of 3 or more is defined as a acicular carbide, and a carbide having a ratio of 1 or more and less than 3 is defined as a spheroidal carbide. . Further, the value of the number of spheroidal carbides divided by the number of all carbides is defined as the spheroidization ratio of the carbide.

碳化物之平均徑長必須在0.6μm以下。由於粗大的碳化物在熔解完畢前所需之時間很長，因此易使淬火度降低。尤其，當碳化物之平均徑長大於0.6μm時，平均加熱速度100℃/秒之高頻淬火之淬火硬化能會降低。又，因應高頻淬火之條件及上述成分組成，宜將碳化物之平均徑長控制在0.55μm以下，且以控制在0.5μm以下較佳。而，從上述測定方法，亦可將面積超過0.01μm2 之碳化物之平均徑長規定在超過0.11(=0.2/√π)μm且0.6μm以下。The average diameter of the carbide must be below 0.6 μm. Since the coarse carbides take a long time before the melting is completed, the degree of quenching is easily lowered. In particular, when the average diameter of the carbide is more than 0.6 μm, the quench hardening energy of the induction hardening of the average heating rate of 100 ° C / sec is lowered. Further, in view of the conditions of the induction hardening and the composition of the above components, it is preferred to control the average diameter of the carbides to 0.55 μm or less, and preferably to 0.5 μm or less. Further, from the above measurement method, the average diameter of the carbide having an area of more than 0.01 μm 2 may be more than 0.11 (= 0.2 / √ π) μm and 0.6 μm or less.

碳化物之球化率在70%以上且小於90%。針狀碳化物之周邊在冷加工時容易應力局部化而易成為裂痕之產生起點。尤其，一旦球化率小於70%冷加工性便會惡化，因此碳化物之球化率在70%以上。又，當需要較高的冷加工性時，碳化物之球化率在73%以上為佳，75%以上較佳。另一方面，與針狀碳化物相較之下，在球狀碳化物中，與鋼之母相相接之表面積較小，且碳從碳化物至母相之釋出擴散路徑較狹窄。尤其，當球化率在90%以上時，平均加熱速度100℃/秒之高頻淬火之淬火硬化能會不夠充分。又，因應高頻淬火之條件，宜將碳化物之球化率控制在小於85%。而，自前述測定方法，亦可將面積在超過0.01μm2 之碳化物之球化率規定在70%以上且小於90%。The spheroidization rate of the carbide is 70% or more and less than 90%. The periphery of the acicular carbide is easily localized by stress during cold working and is likely to be a starting point of cracking. In particular, once the spheroidization rate is less than 70%, the cold workability is deteriorated, so that the spheroidization ratio of the carbide is 70% or more. Further, when high cold workability is required, the spheroidization ratio of the carbide is preferably 73% or more, and more preferably 75% or more. On the other hand, in the case of spheroidal carbides, in the spheroidal carbides, the surface area in contact with the mother of the steel is small, and the diffusion path of carbon from the carbide to the parent phase is narrow. In particular, when the spheroidization rate is 90% or more, the quench hardening of the induction hardening of an average heating rate of 100 ° C / sec is insufficient. Moreover, in view of the conditions of high-frequency quenching, it is preferable to control the spheroidization rate of the carbide to be less than 85%. Further, from the above measurement method, the spheroidization ratio of the carbide having an area of more than 0.01 μm 2 may be set to 70% or more and less than 90%.

上述條件(平均徑長及球化率)以外，碳化物之平均徑長d(μm)與碳化物之球化率p(%)必須滿足上述(2)式。即，碳化物之球化率在70%以上且小於80%，當針狀碳化物較多時，由於針狀碳化物之長軸長之絕對值會影響冷加工性，因此碳化物之球化率與碳化物之平均徑長之間必須存有(2)式之關係。以下，將說明該(2)式。In addition to the above conditions (average diameter and spheroidization ratio), the average diameter d (μm) of the carbide and the spheroidization ratio p (%) of the carbide must satisfy the above formula (2). That is, the spheroidization rate of the carbide is 70% or more and less than 80%. When the acicular carbide is large, since the absolute value of the long axis length of the acicular carbide affects the cold workability, the spheroidization rate of the carbide There must be a relationship of (2) between the average diameter of the carbide and the average diameter of the carbide. Hereinafter, the formula (2) will be explained.

冷加工性與冷加工時之龜裂數有深厚的相關，即，龜裂數愈多，冷加工性愈低。冷加工時之龜裂，推測係以空孔(原子空孔)作為核而產生，而該空孔係因加工所導入之排差之交錯或排差之截切所生成。因此，藉由抑制加工應變之集中，可確保冷加工性。The cold workability is strongly related to the number of cracks in cold working, that is, the more the number of cracks, the lower the cold workability. Cracking during cold working is presumed to be caused by voids (atomic voids), which are generated by the interleaving or the interception of the displacement introduced by the processing. Therefore, cold workability can be ensured by suppressing the concentration of the processing strain.

碳化物若為針狀，短軸長與長軸長之間之尺寸差異較大，應力會集中於針狀碳化物之長軸方向之端部(長軸端部)，因此該長軸端部之應力場與短軸方向之端部(短軸端部)之應力場之間的應力差會變大。為了解除該應力場之不均勻性而導入排差(應變)。因此，冷加工時，在針狀碳化物的附近會生成多數的空孔而產生龜裂。另一方面，碳化物若為球狀，短軸長與長軸長之間之尺寸差異較小，應力場之不均勻性較少，因此排差(應變)難以局部化於碳化物附近，進而抑制龜裂之產生。If the carbide is needle-shaped, the difference between the short axis length and the long axis length is large, and the stress concentrates on the end portion of the long axis direction of the acicular carbide (long axis end), so the long axis end The stress difference between the stress field and the stress field at the end of the short-axis direction (the end of the short-axis) becomes large. In order to release the unevenness of the stress field, a displacement (strain) is introduced. Therefore, in cold working, a large number of voids are formed in the vicinity of the acicular carbide to cause cracking. On the other hand, if the carbide is spherical, the difference in size between the short axis length and the long axis length is small, and the unevenness of the stress field is small, so that the displacement (strain) is difficult to localize near the carbide, and thus Inhibit the occurrence of cracks.

又，不僅碳化物之長寬比，針狀碳化物之長軸長度之絕對值亦會影響長軸端部之應力集中。長軸長度愈大，在長軸端部之應力集中愈高，因此易於產生排差(應變)。所以，為了確保冷加工性，當碳化物之球化率不高時(有許多針狀碳化物時)，必須縮小碳化物之平均徑長。即，當碳化物之球化率在70%以上且小於80%時，碳化物之平均徑長d(μm)與碳化物之球化率p(%)必須滿足上述(2)式。Moreover, not only the aspect ratio of the carbide but also the absolute value of the long axis length of the acicular carbide affects the stress concentration at the end of the long axis. The larger the length of the long axis, the higher the stress concentration at the end of the long axis, and thus the displacement (strain) is liable to occur. Therefore, in order to ensure cold workability, when the spheroidization rate of the carbide is not high (when there are many acicular carbides), the average diameter of the carbide must be reduced. That is, when the spheroidization ratio of the carbide is 70% or more and less than 80%, the average diameter d (μm) of the carbide and the spheroidization ratio p (%) of the carbide must satisfy the above formula (2).

如上述，本發明人等發現：藉由使碳化物之平均徑長與碳化物之球化率滿足適當的預定條件，可確保高頻淬火度並提高冷加工性。As described above, the present inventors have found that by satisfying an appropriate predetermined condition by the average diameter of the carbide and the spheroidization ratio of the carbide, the induction hardening degree can be ensured and the cold workability can be improved.

此外，在本實施形態中，上述成分組成及碳化物之形態以外，另宜控制冷加工前之硬度。Further, in the present embodiment, in addition to the above-described component composition and the form of the carbide, it is preferable to control the hardness before cold working.

只要冷加工前之硬度小於170HV，即可獲得充分的延性，因此可在加工時確保充分的成形量。為使確保更大的成形量，冷加工前之硬度以小於165HV為佳，小於160HV更佳，小於155HV最佳。鋼板愈軟愈可改善延性，且鋼板愈可承受住嚴密的加工，但容易在打孔加工時產生下垂。所以，冷加工前之硬度以120HV以上為佳。近年，使打孔、彎曲及擠壓加工等成一體化之冷加工技術亦逐漸普及，因應上述的製造步驟一體化，宜適當控制冷加工前之硬度。As long as the hardness before cold working is less than 170 HV, sufficient ductility can be obtained, so that a sufficient amount of forming can be ensured during processing. In order to ensure a larger forming amount, the hardness before cold working is preferably less than 165 HV, more preferably less than 160 HV, and most preferably less than 155 HV. The softer the steel plate, the better the ductility, and the more the steel plate can withstand the rigorous processing, but it is easy to sag during the drilling process. Therefore, the hardness before cold working is preferably 120 HV or more. In recent years, cold working techniques such as punching, bending, and extrusion processing have become popular, and in order to integrate the above-described manufacturing steps, the hardness before cold working should be appropriately controlled.

本發明人等所發現之新穎見解，係除了成分組成以外，還包含藉由使碳化物之平均徑長與碳化物之球化率滿足適當的上述預定條件，而使鋼板之冷加工性與高頻淬火度同時成立之技術。此外，本發明人等亦發現藉由將冷加工前之硬度控制在小於170HV，可將鋼板適當地使用於冷加工。The novel findings discovered by the present inventors include, in addition to the component composition, the cold workability and high frequency of the steel sheet by making the average diameter of the carbide and the spheroidization rate of the carbide satisfy the above predetermined conditions. A technique in which the degree of hardening is simultaneously established. Further, the inventors have found that the steel sheet can be suitably used for cold working by controlling the hardness before cold working to less than 170 HV.

高頻淬火後之淬火硬度以500HV以上為佳。只要淬火硬度在500HV以上，伴隨著淬火鋼之高強度化，可提升磨損抗性。尤其，在如汽車用零件之離合器板或齒輪等構件中，為了獲得磨損抗性，以500HV以上之硬質化為理想。一旦淬火硬度過高，淬火部之韌性會極度降低而失去作為機械結構用構件之功能。所以，高頻淬火後之淬火硬度以900HV以下為佳，800HV以下較佳，750HV以下最佳。The quenching hardness after induction hardening is preferably 500 HV or more. As long as the quenching hardness is 500 HV or more, the wear resistance is enhanced by the high strength of the quenched steel. In particular, in a member such as a clutch plate or a gear of a component for an automobile, it is preferable to harden 500 HV or more in order to obtain wear resistance. Once the quenching hardness is too high, the toughness of the quenched portion is extremely lowered and the function as a member for mechanical structure is lost. Therefore, the quenching hardness after induction hardening is preferably 900 HV or less, preferably 800 HV or less, and most preferably 750 HV or less.

在此，為了定義零件所需的淬火硬度之基準，而進行高頻淬火，該高頻淬火係以100℃/秒之平均加熱速度從室溫加熱至1000℃後保持10秒，再立刻以200℃/秒以上之平均冷卻速度急速冷卻至室溫。具體而言，本發明之高頻淬火之試驗條件如下，即：將750℃以上以100±15℃/秒之平均加熱速度從室溫升溫至1000±20℃後，以1000±20℃保持10±0.5秒，之後再立刻將800℃至400℃之間以200±10℃/秒之平均冷卻速度急速冷卻至室溫之條件。該條件之高頻淬火後，以維氏硬度在500以上(亦即500HV以上)之鋼板為本發明之對象。Here, in order to define the quenching hardness required for the part, high-frequency quenching is performed, which is heated from room temperature to 1000 ° C at an average heating rate of 100 ° C / sec for 10 seconds, and immediately after 200 The average cooling rate above °C/sec is rapidly cooled to room temperature. Specifically, the test conditions of the induction hardening of the present invention are as follows: after heating at 750 ° C or higher at an average heating rate of 100 ± 15 ° C / sec from room temperature to 1000 ± 20 ° C, the temperature is maintained at 1000 ± 20 ° C. ±0.5 seconds, and then immediately cooled between 800 ° C and 400 ° C at an average cooling rate of 200 ± 10 ° C / sec to room temperature. After the induction hardening under this condition, a steel sheet having a Vickers hardness of 500 or more (that is, 500 HV or more) is the object of the present invention.

又，鋼板之板厚並未有特別限制，從加工性之觀點看來，以20mm以下或16mm以下為佳，14mm以下較佳，12mm以下或9mm以下最佳。又，從強度之觀點看來，以1mm以上或2mm以上為佳，2.5mm以上較佳，3mm以上最佳。Further, the thickness of the steel sheet is not particularly limited, and from the viewpoint of workability, it is preferably 20 mm or less or 16 mm or less, more preferably 14 mm or less, and most preferably 12 mm or less or 9 mm or less. Further, from the viewpoint of strength, it is preferably 1 mm or more or 2 mm or more, more preferably 2.5 mm or more, and most preferably 3 mm or more.

接著，以第1圖~第5圖說明本實施形態之鋼板的重要概念。Next, an important concept of the steel sheet according to the embodiment will be described with reference to Figs. 1 to 5 .

第1圖中顯示碳化物之平均徑長及碳化物之球化率波及淬火硬度及冷加工性之影響。又，使用寬30mm且長100mm之試驗片(平板彎曲試驗片)，藉由平板彎曲試驗評估冷加工性。在該彎曲試驗中，對於已彎曲之試樣(平板彎曲試樣)之內面(內圍面)及外面(外圍面)分別有壓縮應力及伸張應力施加，因此，藉由評估試樣之內面側及外面側之龜裂可同時測定對應於壓縮應力及伸張應力之加工性。在本發明中，將彎曲半徑設定為板厚之1/2，並將彎曲角度設定在90°。如第1圖顯示，在碳化物之平均徑長d在0.6μm以下，碳化物之球化率p在70%以上且小於90%，且碳化物之平均徑長d(μm)與碳化物之球化率p(%)滿足上述式(2)之鋼板(第1圖中之白色圓圈)中，高頻淬火後可獲得500HV以上之淬火硬度且加工時沒有產生裂痕。相對地，碳化物之球化率在70%以上且小於80%，且碳化物之平均徑長d(μm)與碳化物之球化率p(%)未滿足上述式(2)之鋼板或碳化物之球化率小於70%鋼板(第1圖中之黑色方塊)中，作為損壞起點起作用之碳化物之比例不但增加且加工時有產生裂痕。又，在碳化物之平均徑長超過0.6μm且碳化物之球化率在80%以上且小於90%鋼板或碳化物之球化率在90%以上之鋼板(第1圖中之黑色三角)中，淬火硬度不夠充分。Fig. 1 shows the influence of the average diameter of the carbide and the spheroidization rate of the carbide on the quenching hardness and cold workability. Further, a test piece (plate bending test piece) having a width of 30 mm and a length of 100 mm was used, and cold workability was evaluated by a flat plate bending test. In the bending test, compressive stress and tensile stress are applied to the inner surface (inner peripheral surface) and the outer surface (peripheral surface) of the bent sample (plate bending sample), respectively, and therefore, by evaluating the inside of the sample The cracks on the front side and the outer side can simultaneously measure the workability corresponding to the compressive stress and the tensile stress. In the present invention, the bending radius is set to 1/2 of the plate thickness, and the bending angle is set to 90°. As shown in Fig. 1, the average diameter d of the carbide is 0.6 μm or less, the spheroidization ratio p of the carbide is 70% or more and less than 90%, and the average diameter d (μm) of the carbide and the carbide are The spheroidization ratio p (%) satisfies the steel sheet of the above formula (2) (the white circle in Fig. 1), and after quenching at a high frequency, a quenching hardness of 500 HV or more is obtained, and no crack is generated during the processing. In contrast, the spheroidization rate of the carbide is 70% or more and less than 80%, and the average diameter d (μm) of the carbide and the spheroidization ratio p (%) of the carbide do not satisfy the steel sheet of the above formula (2) or In the case where the spheroidization ratio of the carbide is less than 70% (the black square in Fig. 1), the proportion of the carbide acting as the starting point of the damage increases not only, but also cracks during processing. Further, in the case where the average diameter of the carbide exceeds 0.6 μm and the spheroidization ratio of the carbide is 80% or more and less than 90%, the steel plate or the spheroidization ratio of the carbide is 90% or more (the black triangle in Fig. 1) Medium, the quenching hardness is not sufficient.

在此，在未有特別明記的情況下，作為基準而使用之淬火硬度係定義為在以下條件所測定之硬度。即：在頻率78kHz進行將試樣以100℃/秒之平均加熱速度從室溫加熱至1000℃後保持10秒，再立刻以200℃/秒以上之平均冷卻速度急速冷卻至室溫之高頻淬火，並測定維氏硬度。該高頻淬火後之維氏硬度係本實施形態之淬火硬度。球化率降得愈低，碳化物愈易熔解，因此淬火硬度就愈容易升高。同樣地，碳化物之平均徑長降得愈低，碳化物愈容易熔解，因此淬火硬度就愈容易升高。另一方面，球化率愈高，加工性就變得愈大。如此一來，藉由控制碳化物之形態，可使彼此相反之加工性與淬火硬化性之兩因子同時成立。Here, in the case where it is not particularly noted, the quenching hardness used as a standard is defined as the hardness measured under the following conditions. That is, at a frequency of 78 kHz, the sample is heated from room temperature to 1000 ° C at an average heating rate of 100 ° C / sec for 10 seconds, and then rapidly cooled to room temperature at an average cooling rate of 200 ° C / sec or more. Quenching and measuring Vickers hardness. The Vickers hardness after the induction hardening is the quenching hardness of this embodiment. The lower the spheroidization rate is, the more easily the carbide is melted, so the quenching hardness is more likely to increase. Similarly, the lower the average diameter of the carbide is, the easier the carbide is to be melted, and the harder the quenching hardness is. On the other hand, the higher the spheroidization rate, the greater the workability becomes. In this way, by controlling the form of the carbide, the two factors of the opposite workability and the quench hardenability can be simultaneously established.

第2圖中顯示Si量與冷加工性(冷加工後之碳化物界面及粒內之龜裂數)之關係。在平板彎曲試樣之彎曲角部(最大曲率部)之板厚剖面(包含板厚方向及長邊方向之剖面)，以掃描型電子顯微鏡在倍率3000倍測定板厚1/8~3/8、及5/8~7/8之區域之龜裂數。當上述龜裂數在每1mm2 為20個以內時，可判斷為可抑制冷加工時因界面剝離所產生之龜裂生成，因此將冷加工性評估為“良好”。又，當龜裂數超過20個，則將冷加工性評估為“差”。如第2圖顯示，在Si量0.06%以上之鋼板中，冷加工性良好。此外，到0.3%之Si量為止，Si量增加的同時龜裂數亦有減少。此時，因肥粒鐵與碳化物之界面之剝離而有龜裂產生。而且，一旦Si量超過0.3%，Si量增加的同時龜裂數有增加。此時，肥粒鐵相中有龜裂產生。又，一旦Si量從0.06%增加至0.1%，龜裂數之降低比例增大且大幅改善冷加工性。此外，只要Si量在0.15~0.26%，可藉由Si獲得改善冷加工性之效果的最大限度。而，在第2圖中，以680℃將C量0.40~0.45%之試樣退火30hr後，進行後述之冷加工性評估。Fig. 2 shows the relationship between the amount of Si and the cold workability (the carbide interface after cold working and the number of cracks in the grain). The thickness profile (including the thickness direction and the longitudinal direction of the curved corner portion of the flat bending specimen) is measured by a scanning electron microscope at a magnification of 3000 times 1/8 to 3/8. And the number of cracks in the area of 5/8~7/8. When the number of cracks is less than 20 per 1 mm 2 , it can be judged that crack formation due to interfacial peeling during cold working can be suppressed, and therefore cold workability is evaluated as "good". Further, when the number of cracks exceeds 20, the cold workability is evaluated as "poor". As shown in Fig. 2, in the steel sheet having a Si content of 0.06% or more, the cold workability is good. Further, until the amount of Si is 0.3%, the amount of Si increases and the number of cracks also decreases. At this time, cracks occur due to peeling of the interface between the ferrite iron and the carbide. Further, once the amount of Si exceeds 0.3%, the amount of Si increases while the number of cracks increases. At this time, cracks are generated in the ferrite phase. Further, as the amount of Si increases from 0.06% to 0.1%, the proportion of reduction in the number of cracks increases and the cold workability is greatly improved. Further, as long as the amount of Si is from 0.15 to 0.26%, the effect of improving the cold workability can be maximized by Si. On the other hand, in the second drawing, the sample having a C content of 0.40 to 0.45% was annealed at 680 ° C for 30 hr, and then the cold workability evaluation described later was carried out.

第3圖中顯示[Cr]+[Mo]/10與淬火硬度之關係。如第3圖顯示，只要[Cr]+[Mo]/10小於0.10，即可進一步提升淬火硬度。因此，[Cr]+[Mo]/10小於0.10為佳。而，在第3圖中，以680℃將C量0.40~0.45%之試樣退火30hr後，進行上述高頻淬火並測定淬火硬度。Fig. 3 shows the relationship between [Cr] + [Mo]/10 and quenching hardness. As shown in Fig. 3, as long as [Cr] + [Mo]/10 is less than 0.10, the quenching hardness can be further improved. Therefore, [Cr]+[Mo]/10 is preferably less than 0.10. On the other hand, in Fig. 3, a sample having a C content of 0.40 to 0.45% was annealed at 680 ° C for 30 hr, and then the above-described induction hardening was performed to measure the quenching hardness.

第4圖中顯示碳化物之球化率與冷加工時以碳化物為起點而產生之龜裂(碳化物起點之龜裂)數之關係。如從該第4圖可知，一旦碳化物之球化率小於70%，龜裂數便會急遽增加。Fig. 4 shows the relationship between the spheroidization ratio of the carbide and the number of cracks (cracks of the carbide starting point) which are generated from the carbide at the time of cold working. As can be seen from Fig. 4, once the spheroidization rate of the carbide is less than 70%, the number of cracks increases sharply.

又，第5圖中顯示S量與冷加工時之硫化物起點之龜裂數之關係。如從該第5圖可知，一旦S量在0.0075%以下，硫化物起點之龜裂數便會大幅降低。Further, Fig. 5 shows the relationship between the amount of S and the number of cracks at the starting point of the sulfide at the time of cold working. As can be seen from Fig. 5, when the amount of S is 0.0075% or less, the number of cracks at the starting point of the sulfide is greatly lowered.

而，為了判別源自於硫化物之龜裂及源自於碳化物之龜裂，使用附屬於掃描型電子顯微鏡之能量色散X射線光譜儀(EDS)。Further, in order to discriminate cracks originating from sulfides and cracks derived from carbides, an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope was used.

接下來，說明本發明之一實施形態之冷加工用中碳鋼板之製造方法(以下稱為「本實施形態之製造方法」)。本實施形態之製造方法具有將高溫捲取及低溫退火予以組合之技術思想，以下顯示其具體例。而，以下顯示之製造方法為其一例，只要可獲得所需之組織，亦可使用其他方法製造。Next, a method of producing a medium carbon steel sheet for cold working according to an embodiment of the present invention (hereinafter referred to as "the manufacturing method of the present embodiment") will be described. The manufacturing method of this embodiment has a technical idea of combining high-temperature coiling and low-temperature annealing, and specific examples thereof will be described below. However, the manufacturing method shown below is an example thereof, and other methods can be used as long as the desired structure can be obtained.

首先，加熱上述實施形態之化學成分之連續鑄造鑄片(鑄片)。加熱溫度在1050℃以上且在1300℃以下。又，為了抑制加熱中之脫碳與吸氮，均熱時間在150分鐘以下為佳，90分鐘以下較佳。在此，均熱時間表示鑄片表面之溫度從達及較目標加熱溫度低20℃之溫度之時間起，至鑄片出加熱爐為止之時間。一旦加熱溫度超過1300℃或均熱時間過長，在加熱步驟中鋼胚之表層部之脫C會變得很顯著，且鋼板表面之淬火度會劣化。又，若將鑄片加熱至1050℃以上，可獲得略呈沃斯田鐵單相之組織。從抑制脫C之觀點看來，加熱溫度在1280℃以下為佳，1240℃以下較佳，1200℃以下最佳。同樣地，均熱時間在60分鐘以下更佳。而，均熱時間之下限並未有特別限制。First, a continuous casting slab (cast piece) of the chemical composition of the above embodiment is heated. The heating temperature is 1050 ° C or more and 1300 ° C or less. Further, in order to suppress decarburization and nitrogen absorption during heating, the soaking time is preferably 150 minutes or shorter, and preferably 90 minutes or shorter. Here, the soaking time indicates the time from the time when the temperature of the surface of the cast piece reaches a temperature lower by 20 ° C than the target heating temperature to the time when the cast piece is discharged from the heating furnace. When the heating temperature exceeds 1300 ° C or the soaking time is too long, the removal of C in the surface portion of the steel in the heating step becomes remarkable, and the degree of hardening of the surface of the steel sheet deteriorates. Further, if the cast piece is heated to 1050 ° C or higher, a structure in which a single phase of the Worthite iron is obtained can be obtained. From the viewpoint of suppressing the removal of C, the heating temperature is preferably 1280 ° C or lower, preferably 1240 ° C or lower, and most preferably 1200 ° C or lower. Similarly, the soaking time is preferably 60 minutes or less. However, the lower limit of the soaking time is not particularly limited.

而，可將連續鑄造鑄片直接供於熱軋，亦可於冷卻後再加熱供於熱軋。前者與後者之間，在鋼板特性上並未有太大差別。Alternatively, the continuous casting slab may be directly supplied to hot rolling, or may be heated and then hot rolled for cooling. There is not much difference in the characteristics of the steel sheet between the former and the latter.

在熱軋方面，可任擇採用一般的熱軋及在最後軋延中接合鋼胚之連續化熱軋。熱軋之結束溫度(熱軋結束溫度)係由生產性、板厚精度、異向性改善及表面缺陷抑制之觀點而決定。一旦熱軋結束溫度低於750℃，在最後軋延會產生許多因燒黏所造成之缺陷。又，一旦熱軋結束溫度高於1000℃，源自尺寸缺陷的發生頻率會增高，使產品成品率降低而增加成本。所以，熱軋結束溫度在750~1000℃。In the case of hot rolling, it is optional to use a general hot rolling and a continuous hot rolling in which a steel preform is joined in the final rolling. The end temperature of hot rolling (hot rolling end temperature) is determined from the viewpoints of productivity, thickness accuracy, anisotropy improvement, and surface defect suppression. Once the hot rolling end temperature is below 750 ° C, many defects due to burning will occur during the final rolling. Further, once the hot rolling end temperature is higher than 1000 ° C, the frequency of occurrence of dimensional defects increases, and the product yield is lowered to increase the cost. Therefore, the hot rolling end temperature is 750~1000 °C.

進而，熱軋後立即以20℃/秒以上且50℃/秒以下之平均冷卻速度(第一平均冷卻速度)，將熱軋(最後軋延)後之鋼板冷卻至500℃以上且700℃以下之冷卻溫度(第一冷卻結束溫度)。此時，可限制共析前肥粒鐵之生成及成長，並使生成於鋼板中之波來鐵之層狀間隔減少，將退火後之鋼板中之碳化物予以微細化。只要自熱軋結束溫度起至該冷卻溫度(第一冷卻結束溫度)為止之平均冷卻速度在20℃/秒以下，即不會限制共析前肥粒鐵之生成及成長，因而有時會生成伴隨偏析而成的波來鐵帶。所以，退火後容易形成粗大的碳化物且淬火度可能會降低。又，一旦該平均冷卻速度在50℃/秒以上，便難以進行鋼板之溫度控制。此外，可能會無法充分生成用以確保具有上述球化率之雪明碳鐵所需的波來鐵。如此一來，為了適當進行波來鐵之組織控制，必須顧及波來鐵之變態開始溫度與變態結束溫度，將上述冷卻溫度控制在500℃以上且在700℃。Further, immediately after hot rolling, the steel sheet after hot rolling (final rolling) is cooled to 500 ° C or more and 700 ° C or less at an average cooling rate (first average cooling rate) of 20 ° C / sec or more and 50 ° C / sec or less. Cooling temperature (first cooling end temperature). In this case, the formation and growth of the ferrite iron before the eutectoid precipitation can be restricted, and the lamellar spacing of the ferrite formed in the steel sheet can be reduced, and the carbide in the annealed steel sheet can be made fine. As long as the average cooling rate from the hot rolling end temperature to the cooling temperature (first cooling end temperature) is 20 ° C / sec or less, that is, the generation and growth of the ferrite iron before the eutectoid precipitation are not restricted, and thus may be generated. A wave of iron belts with segregation. Therefore, coarse carbides are easily formed after annealing and the degree of hardening may be lowered. Moreover, once the average cooling rate is 50 ° C /sec or more, it is difficult to control the temperature of the steel sheet. In addition, it may not be possible to sufficiently generate the Borne iron required to secure the spheroidal carbon having the above spheroidization rate. In this way, in order to properly control the structure of the Borne iron, it is necessary to take into consideration the metamorphic start temperature and the metamorphic end temperature of the Borne iron, and control the above-described cooling temperature to 500 ° C or higher and 700 ° C.

之後，以5℃/秒以上且30℃/秒以下之平均冷卻速度(第二平均冷卻速度)，將該鋼板冷卻至400℃以上且較上述第一冷卻結束溫度低至少50℃之溫度(即，第一冷卻結束溫度與第二冷卻結束溫度之差在50℃以上且較第一冷卻結束溫度低50℃之溫度以下)之捲取溫度(第二冷卻結束溫度)，再進行捲取。此時，可確保鋼板中之波來鐵量並使生成於鋼板中之波來鐵之層狀間隔減少，將退火後之鋼板中之碳化物予以微細化。若以從第一冷卻結束溫度起至較第一冷卻結束溫度低50℃之溫度間之溫度區來捲取鋼板，會生成層狀間隔很大的波來鐵，而使退火後碳化物難以球化造成冷加工性惡化，因此，以較第一冷卻結束溫度低至少50℃之溫度進行捲取。又，若從上述冷卻溫度起至捲取溫度為止之平均冷卻速度在5℃/秒以下，可能會生成伴隨著偏析而成之波來鐵帶，或大幅增加波來鐵之層狀間隔。所以，退火後容易形成粗大的碳化物且可能降低鋼板之淬火度。又，一旦該平均冷卻速度在30℃/秒以上，可能會無法充分生成用以確保具有上述球化率之雪明碳鐵所需之波來鐵。Thereafter, the steel sheet is cooled to 400 ° C or higher and at a temperature lower than the first cooling end temperature by at least 50 ° C at an average cooling rate (second average cooling rate) of 5 ° C / sec or more and 30 ° C / sec or less (ie, The coiling temperature (second cooling end temperature) at which the difference between the first cooling end temperature and the second cooling end temperature is 50° C. or higher and 50° C. lower than the first cooling end temperature is further taken up. At this time, the amount of iron in the steel sheet can be ensured, and the lamellar spacing of the ferrite formed in the steel sheet can be reduced, and the carbide in the annealed steel sheet can be made fine. If the steel sheet is taken up in a temperature range from the first cooling end temperature to a temperature lower than the first cooling end temperature by 50 ° C, a layered iron having a large interval is formed, and the carbide is hard to be balled after annealing. The cold workability is deteriorated, so that the coiling is performed at a temperature lower than the first cooling end temperature by at least 50 °C. Further, when the average cooling rate from the cooling temperature to the coiling temperature is 5 ° C / sec or less, a wave band due to segregation may be generated, or a layered interval of the ferritic iron may be greatly increased. Therefore, coarse carbides are easily formed after annealing and the degree of hardening of the steel sheet may be lowered. Moreover, once the average cooling rate is 30 ° C /sec or more, it may not be possible to sufficiently generate the wave iron required to secure the spheroidal carbon having the above spheroidization rate.

又，如上述，冷卻後之鋼板係以從400℃起至較第一冷卻結束溫度低至少50℃之溫度間之捲取溫度進行捲取。一旦捲取溫度低於400℃，可能會使一部分產生麻田散鐵變態而使鋼板強度增高變得難以處理。又，可能會使組織變得不均勻，在冷軋時發生量規尋覓(gauge-hunting)而使成品率降低。另一方面，若以超過較第一冷卻結束溫度低50℃之溫度的溫度來實施捲取，如前述會生成層狀間隔很大的波來鐵使退火後之球化率降低，因而使冷加工性惡化。Further, as described above, the cooled steel sheet is wound up at a coiling temperature between 400 ° C and a temperature lower than the first cooling end temperature by at least 50 ° C. Once the coiling temperature is lower than 400 ° C, it may cause a part of the granulated iron to metamorphose and the steel sheet strength to become difficult to handle. Further, the structure may become uneven, and gauge-hunting occurs during cold rolling to lower the yield. On the other hand, if the coiling is performed at a temperature exceeding the temperature lower than the first cooling end temperature by 50 ° C, as described above, a wave having a large interlayer interval is formed to lower the spheroidization ratio after annealing, thereby causing cold working. Sexual deterioration.

此外，將鋼板保持在400℃以上且在第二冷卻結束溫度以下，以使經捲取之鋼板(旋管)處在400℃以上之時間限制在30小時以下。爾後，將鋼板冷卻至400℃以下之溫度(例如室溫、或可酸洗之溫度)。在此，在同一步驟進行保持與冷卻時，可在冷卻時將鋼板處在400℃以上之時間限制在30小時以下。該等情況可控制脫碳，充分確保表面之C量。一旦鋼板處在400℃以上之時間超過30小時，則氧來源(例如空氣)與碳會在鋼板表面起反應而變得難以確保高頻淬火所需之鋼板表面之碳量。Further, the steel sheet is maintained at 400 ° C or higher and at or below the second cooling end temperature so that the time during which the coiled steel sheet (coil tube) is at 400 ° C or higher is limited to 30 hours or shorter. Thereafter, the steel sheet is cooled to a temperature below 400 ° C (for example, room temperature, or a pickable temperature). Here, when holding and cooling are performed in the same step, the time during which the steel sheet is at 400 ° C or more can be limited to 30 hours or less at the time of cooling. These conditions can control decarburization and fully ensure the amount of C on the surface. When the steel sheet is at a temperature of 400 ° C or more for more than 30 hours, an oxygen source (for example, air) reacts with carbon on the surface of the steel sheet to make it difficult to secure the amount of carbon on the surface of the steel sheet required for induction hardening.

將上述經冷卻之鋼板予以酸洗並將表面加以潔淨化後，對鋼板施加軟化退火。在本實施形態中，係對鋼板施加軟化箱式退火，以提升鋼板之加工性。After the above-mentioned cooled steel sheet is pickled and the surface is cleaned, softening annealing is applied to the steel sheet. In the present embodiment, a soft box annealing is applied to the steel sheet to improve the workability of the steel sheet.

在軟化箱式退火(退火)中，係將鋼板從室溫加熱至600℃以上且Ac1 -10℃以下之退火溫度後，保持5小時以上且小於100小時。藉由該5小時以上且小於100小時之保持，可使肥粒鐵粒粗大化使鋼板軟化，且可以不過度增加碳化物之球化率的方式將鋼板予以退火。若退火溫度在Ac1 -10℃以上(尤其在Ac1 ℃以上)，碳化物會急遽球化，因此在其後之高頻淬火中，會使淬火度降低。另一方面，退火溫度若在600℃以上且在Ac1 -10℃以下，可使鋼板中之元素(尤其是C)之擴散速度最佳化，且可適當控制碳化物之球化率。In the soft box annealing (annealing), the steel sheet is heated from room temperature to 600 ° C or higher and an annealing temperature of A c1 -10 ° C or lower, and is maintained for 5 hours or more and less than 100 hours. By maintaining the granules for 5 hours or more and less than 100 hours, the steel grains can be coarsened to soften the steel sheets, and the steel sheets can be annealed without excessively increasing the spheroidization rate of the carbides. If the annealing temperature is above A c1 -10 ° C (especially above A c1 ° C), the carbide will be spheroidally spheroidized, so that the quenching degree will be lowered in the subsequent high-frequency quenching. On the other hand, when the annealing temperature is 600 ° C or more and A c1 -10 ° C or less, the diffusion rate of the element (especially C) in the steel sheet can be optimized, and the spheroidization ratio of the carbide can be appropriately controlled.

在箱式退火中，以氫濃度在95%以上且在400℃以下之露點低於-20℃、超過400℃之露點低於-40℃為佳。In the box annealing, the dew point of the hydrogen concentration of 95% or more and 400 ° C or less is less than -20 ° C, and the dew point of more than 400 ° C is preferably less than -40 ° C.

若在氫濃度95%以上之環境中進行退火，可較均勻地控制旋管內之溫度分布，且可抑制因氮氣侵入所造成的淬火度之降低。又，若將400℃以下之露點控制在低於-20℃且將超過400℃之露點控制在低於-40℃，即可充分抑制退火中之脫碳。If the annealing is performed in an environment having a hydrogen concentration of 95% or more, the temperature distribution in the coil can be controlled more uniformly, and the decrease in the degree of quenching due to the intrusion of nitrogen can be suppressed. Further, if the dew point of 400 ° C or less is controlled to be lower than -20 ° C and the dew point of more than 400 ° C is controlled to be lower than -40 ° C, decarburization during annealing can be sufficiently suppressed.

有關其他處理，只要鋼板中之碳化物形態滿足上述實施形態之鋼板條件，即未有特別限制。例如，亦可實施冷軋及其後之軟化退火。在此，為便於理解，於第8圖中顯示包含本實施形態及以下變形例之本發明之冷加工用鋼板之製造方法之概略流程圖。Regarding the other treatment, the carbide form in the steel sheet satisfies the steel sheet condition of the above embodiment, that is, it is not particularly limited. For example, cold rolling and subsequent softening annealing can also be performed. Here, in order to facilitate understanding, FIG. 8 is a schematic flow chart showing a method of manufacturing the steel sheet for cold working according to the present invention including the present embodiment and the following modifications.

而，為了進一步使冷加工性提升，從潤滑性之觀點看來，亦可在上述實施形態之鋼板表面形成表面處理皮膜。例如，作為上述實施形態之鋼板之一變形例，宜在上述實施形態之鋼板表面形成以下之表面處理皮膜。Further, in order to further improve the cold workability, a surface treatment film may be formed on the surface of the steel sheet of the above embodiment from the viewpoint of lubricity. For example, as a modification of the steel sheet according to the above embodiment, it is preferable to form the following surface treatment film on the surface of the steel sheet of the above embodiment.

在該變形例中，於鋼板表面設置傾斜型表面處理皮膜，該傾斜型表面處理皮膜係由確保與心材之鋼板之密接性之密接層、保持潤滑劑之基底層、及使潤滑性提升之潤滑劑層所構成，各層之厚度有加以控制。所以，從以簡便的處理步驟保護地球環境之觀點看來，亦可在鋼板表面形成適當的表面處理皮膜。又，可對鋼板賦予良好的潤滑性、防燒黏性能及防擦傷性能。In this modification, an inclined surface treatment film is provided on the surface of the steel sheet, and the inclined surface treatment film is an adhesion layer for ensuring adhesion to the steel sheet of the heart material, a base layer for holding the lubricant, and lubrication for improving lubricity. The layer is composed of layers, and the thickness of each layer is controlled. Therefore, it is also possible to form an appropriate surface treatment film on the surface of the steel sheet from the viewpoint of protecting the global environment with a simple processing step. Moreover, the steel sheet can be imparted with good lubricity, anti-sticking properties and anti-scratch properties.

以下將參考第6圖詳細說明本變形例之冷加工用鋼板(鋼板)。The steel sheet (steel plate) for cold working according to the present modification will be described in detail below with reference to Fig. 6.

而，本說明書及上述圖式中，就實質上具有同一功能構成之構成要素賦予同一符號，以省略重複說明。In the present specification and the drawings, the components that have substantially the same functions are denoted by the same reference numerals, and the description thereof will not be repeated.

[本變形例之鋼板構成][Steel plate configuration of the present modification]

首先，參考第6圖說明本變形例之鋼板(以下稱為「表面處理鋼板」)之構成。第6圖係顯示表面處理鋼板之構成之示意縱剖面圖。First, the configuration of a steel sheet (hereinafter referred to as "surface-treated steel sheet") according to the present modification will be described with reference to Fig. 6 . Fig. 6 is a schematic longitudinal sectional view showing the constitution of a surface-treated steel sheet.

如第6圖顯示，表面處理鋼板1具有心材之鋼板10、及形成在鋼板10之至少一面之表面處理皮膜(皮膜)100。As shown in Fig. 6, the surface-treated steel sheet 1 has a steel sheet 10 having a core material and a surface treatment film (film) 100 formed on at least one surface of the steel sheet 10.

(鋼板10)(steel plate 10)

上述實施形態之鋼板可直接使用在表面處理鋼板1之心材之鋼板10。然而，亦可對上述實施形態之鋼板施加鍍敷。例如，可對上述實施形態之鋼板施加使用鋅、鎳、鐵、鋁、鈦、鎂、鉻、錳、錫之1種以上之金屬之鍍敷。The steel sheet of the above embodiment can be directly used for the steel sheet 10 of the core material of the surface-treated steel sheet 1. However, plating may be applied to the steel sheet of the above embodiment. For example, plating of one or more metals of zinc, nickel, iron, aluminum, titanium, magnesium, chromium, manganese, and tin may be applied to the steel sheet of the above embodiment.

(表面處理皮膜100)(surface treatment film 100)

在表面處理皮膜100，該皮膜中之各成分在膜厚方向具有濃度梯度。所以，可將傾斜型皮膜之表面處理皮膜100區分為3層。即，在該表面處理皮膜100，可從表面處理皮膜100與鋼板10之界面起朝向表面處理皮膜100之表面，以密接層110、基底層120、及潤滑劑層130之順序形成3層。The film 100 is surface-treated, and each component in the film has a concentration gradient in the film thickness direction. Therefore, the surface treatment film 100 of the inclined film can be divided into three layers. That is, in the surface treatment film 100, the surface of the surface treatment film 100 can be formed from the interface between the surface treatment film 100 and the steel sheet 10, and three layers can be formed in the order of the adhesion layer 110, the base layer 120, and the lubricant layer 130.

在此，本變形例之「傾斜型」如上述係表示含於表面處理皮膜100中之成分在皮膜之膜厚方向具有濃度梯度之意。即，作為表面處理皮膜100中之主要成分，因形成於心材之鋼板10之表面金屬間之矽醇鍵結(詳細將於後述)之成分有耐熱樹脂、無機酸鹽及潤滑劑等，該等成分在表面處理皮膜100之膜厚方向具有濃度梯度。較詳細而言，從表面處理皮膜100與鋼板10之界面起朝向表面處理皮膜100之表面，潤滑劑131之濃度會逐漸增加，相反地，耐熱樹脂及無機酸鹽之濃度會逐漸減少。又，隨著靠近表面處理皮膜100與鋼板10之界面，起因於矽醇鍵結之成分會逐漸增加。因此，含於表面處理皮膜100之密接層100、基底層120及潤滑劑層130並非完全分離地形成3層(即某層之成分完全不存於其他層中)。Here, the "inclined type" of the present modification means that the component contained in the surface treatment film 100 has a concentration gradient in the film thickness direction of the film as described above. In other words, as a main component in the surface treatment film 100, a component of a sterol bond between the surface metals of the steel sheet 10 formed of the core material (details will be described later) includes a heat resistant resin, a mineral acid salt, a lubricant, and the like. The composition has a concentration gradient in the film thickness direction of the surface treatment film 100. In more detail, from the interface between the surface treatment film 100 and the steel sheet 10 toward the surface of the surface treatment film 100, the concentration of the lubricant 131 gradually increases, and conversely, the concentration of the heat resistant resin and the inorganic acid salt gradually decreases. Further, as the interface between the surface treatment film 100 and the steel sheet 10 is approached, the component resulting from the sterol bond is gradually increased. Therefore, the adhesion layer 100, the base layer 120, and the lubricant layer 130 contained in the surface treatment film 100 are not completely separated into three layers (that is, the components of one layer are not present in the other layers at all).

以下，詳細說明構成表面處理皮膜100之各層構成。Hereinafter, the structure of each layer constituting the surface treatment film 100 will be described in detail.

<密接層110><Close layer 110>

密接層110具有確保伴隨著冷加工之表面處理皮膜100與心材之鋼板10間之密接性，並防止表面處理鋼板1與模具之燒黏之功能。具體上，密接層110係位在靠近表面處理皮膜100與鋼板10之界面之側，在構成表面處理皮膜100之3層中含有最多量之起因於矽醇鍵結之成分。The adhesion layer 110 has a function of ensuring the adhesion between the surface treatment film 100 and the steel sheet 10 of the core material accompanying the cold working, and preventing the surface-treated steel sheet 1 from sticking to the mold. Specifically, the adhesion layer 110 is located on the side close to the interface between the surface treatment film 100 and the steel sheet 10, and contains the most amount of components derived from sterol bonds in the three layers constituting the surface treatment film 100.

在此，本變形例之矽醇鍵結係以Si-O-X(X為鋼板(心材)之構成成分之金屬)表示，乃形成在表面處理皮膜100與鋼板10之界面附近。該矽醇鍵結推測係對應於用以形成表面處理皮膜100之表面處理液中所含之矽烷耦合劑、與鋼板10表面之金屬(例如，已對鋼板10施加鍍敷時係含於鍍敷中之金屬種(Zn及Al等)，在未對鋼板10施加鍍敷時係Fe)之氧化物間的共價鍵。又，矽醇鍵結之存在可藉由可進行試料在深度方向之元素分析之方法(例如，高頻波輝光放電發射分光分析裝置(高頻波GDS))，依據表面處理皮膜100在膜厚方向中起因於矽醇鍵結之成分(Si、X、O)元素之頻譜強度，定量各元素而加以確認。又，從試料剖面之直接觀察(例如，使用場發射穿透式電子顯微鏡(FE-TEM)之觀察方法)及微小部元素分析(例如，使用能量色散X射線光譜儀(EDS)之分析方法)亦可確認矽醇鍵結之存在。Here, the sterol bond of the present modification is represented by Si-O-X (X is a metal component of a steel sheet (heart material)), and is formed in the vicinity of the interface between the surface treatment film 100 and the steel sheet 10. The sterol bond is estimated to correspond to the decane coupling agent contained in the surface treatment liquid for forming the surface treatment film 100 and the metal on the surface of the steel sheet 10 (for example, when plating is applied to the steel sheet 10, it is contained in plating). Among the metal species (Zn, Al, etc.), a covalent bond between oxides of Fe) is not applied when plating is applied to the steel sheet 10. Further, the presence of the sterol bond can be caused by the elemental analysis of the sample in the depth direction (for example, a high-frequency glow discharge emission spectroscopic analyzer (high-frequency wave GDS)), which is caused by the surface treatment film 100 in the film thickness direction. The spectral intensity of the sterol-bonded component (Si, X, O) elements is quantified by quantifying each element. In addition, direct observation from the sample profile (for example, observation method using field emission transmission electron microscope (FE-TEM)) and micro elemental analysis (for example, analysis method using energy dispersive X-ray spectroscopy (EDS)) The presence of a sterol bond can be confirmed.

又，密接層110之厚度必須在0.1nm以上且在100nm以下。當密接層110之厚度小於0.1nm，矽醇鍵結之形成會不夠充分，因此表面處理皮膜100與鋼板10之間將無法獲得充分的密接度。另一方面，一旦密接層110之厚度超過100nm，矽醇鍵結之數量會變得過多，且在表面處理鋼板1之加工時密接層110內之內部應力會變高且皮膜變脆弱，因而降低表面處理皮膜100與鋼板10之間之密接度。從可進一步確實地確保表面處理皮膜100與鋼板10之間之密接度之觀點看來，密接層110之厚度宜在0.5nm以上且在50nm以下。Further, the thickness of the adhesion layer 110 must be 0.1 nm or more and 100 nm or less. When the thickness of the adhesion layer 110 is less than 0.1 nm, the formation of sterol bond may be insufficient, so that sufficient adhesion between the surface treatment film 100 and the steel sheet 10 will not be obtained. On the other hand, once the thickness of the adhesion layer 110 exceeds 100 nm, the amount of sterol bond becomes excessive, and the internal stress in the adhesion layer 110 becomes high and the film becomes weak during the processing of the surface-treated steel sheet 1, thereby reducing The degree of adhesion between the surface treatment film 100 and the steel sheet 10. The thickness of the adhesion layer 110 is preferably 0.5 nm or more and 50 nm or less from the viewpoint of further ensuring the degree of adhesion between the surface treatment film 100 and the steel sheet 10.

<基底層120><base layer 120>

基底層120可使冷加工時之鋼板跟從性提升，並對表面處理鋼板1賦予與模具之燒黏對應之硬度及強度。又，該基底層120可保持潤滑劑131及潤滑劑層130。具體而言，基底層120係位在密接層110與潤滑劑層130之間作為中間層，在構成表面處理皮膜100之3層中含有最多量之耐熱樹脂及無機酸鹽。The base layer 120 can improve the followability of the steel sheet during cold working, and impart hardness and strength to the surface-treated steel sheet 1 corresponding to the burning of the mold. Further, the base layer 120 can hold the lubricant 131 and the lubricant layer 130. Specifically, the underlayer 120 is interposed between the adhesion layer 110 and the lubricant layer 130 as an intermediate layer, and the third layer constituting the surface treatment film 100 contains the most heat-resistant resin and inorganic acid salt.

若選擇無機酸鹽作為含於基底層120中之成分，可形成如本變形例之傾斜型的3層構造之皮膜，且可充分發揮上述之基底層120之功能。而，在本變形例中，係使用水系表面處理液來形成表面處理皮膜100，因此，慮及該表面處理液之穩定性，本變形例之無機酸鹽以水溶性為佳。但，即便無機酸鹽為不溶或難溶於水之鹽，只要為例如可溶於酸之鹽，便無須考慮表面處理液之穩定性。藉由組合可溶於水之無機酸鹽(如硝酸鋅)與酸(如磷酸)使用，可形成包含不溶或難溶於水之鹽(如磷酸鋅)之皮膜。When the inorganic acid salt is selected as the component contained in the underlying layer 120, the film of the three-layer structure of the inclined type according to the present modification can be formed, and the function of the underlying layer 120 described above can be sufficiently exerted. In the present modification, the surface treatment film 100 is formed using the aqueous surface treatment liquid. Therefore, the inorganic acid salt of the present modification is preferably water-soluble in consideration of the stability of the surface treatment liquid. However, even if the inorganic acid salt is a salt which is insoluble or poorly soluble in water, it is not necessary to consider the stability of the surface treatment liquid as long as it is, for example, an acid-soluble salt. By combining a water-soluble inorganic acid salt such as zinc nitrate with an acid such as phosphoric acid, a film containing an insoluble or poorly water-soluble salt such as zinc phosphate can be formed.

從如以上之功能看來，作為本變形例之無機酸鹽，例如可將磷酸鹽、硼酸鹽、矽酸鹽、硫酸塩、鉬酸鹽、或鎢酸鹽予以單獨或複數組合使用。較具體而言，作為無機酸鹽，例如可使用磷酸鋅、磷酸鈣、硫酸鈉、硫酸鉀、矽酸鉀、硼酸鈉、硼酸鉀、硼酸銨、鉬酸鉀、鉬酸鈉、鎢酸鉀、及鎢酸鈉等。但，該等中，從測定密接層100、基底層120及潤滑劑層130之各層厚度時之方便等理由，無機酸鹽尤以選自於由磷酸鹽、硼酸鹽及矽酸鹽所構成之群組中之至少1種化合物較佳。As the inorganic acid salt of the present modification, for example, phosphate, borate, citrate, barium sulfate, molybdate or tungstate can be used singly or in combination. More specifically, as the inorganic acid salt, for example, zinc phosphate, calcium phosphate, sodium sulfate, potassium sulfate, potassium citrate, sodium borate, potassium borate, ammonium borate, potassium molybdate, sodium molybdate, potassium tungstate, or the like can be used. And sodium tungstate and the like. However, in these cases, the inorganic acid salt is particularly selected from the group consisting of phosphates, borates and silicates for the purpose of measuring the thickness of each of the layers of the adhesion layer 100, the base layer 120 and the lubricant layer 130. At least one compound in the group is preferred.

又，於基底層120含有耐熱樹脂作為主要成分。冷加工時，表面處理鋼板1係藉由材料之表面處理鋼板1與模具之間之摩擦力而變得比較高溫，因此在此種高溫之加工條件下，表面處理皮膜100亦必需維持作為皮膜之形狀。由此觀點看來，本變形例之耐熱樹脂以具有可在超過冷加工時之到達溫度(大概200℃)之溫度內(例如超過200℃且在400℃以下之預定溫度)保持皮膜形狀之耐熱性為佳。而，在本變形例中，係使用水系表面處理液來形成表面處理皮膜100，因此，慮及該表面處理液之穩定性，本變形例之耐熱樹脂以水溶性為佳。Further, the base layer 120 contains a heat resistant resin as a main component. In the cold working, the surface-treated steel sheet 1 is relatively high in temperature by the friction between the surface-treated steel sheet 1 and the mold, so that the surface-treated film 100 must also maintain the shape as a film under such high-temperature processing conditions. . From this point of view, the heat resistant resin of the present modification has heat resistance which maintains the shape of the film in a temperature exceeding the temperature reached at the time of cold working (about 200 ° C) (for example, a predetermined temperature exceeding 200 ° C and below 400 ° C). It is better. In the present modification, the surface treatment film 100 is formed using a water-based surface treatment liquid. Therefore, the heat-resistant resin of the present modification is preferably water-soluble in consideration of the stability of the surface treatment liquid.

由如以上功能看來，作為本變形例之耐熱樹脂，例如可使用聚醯亞胺樹脂、聚酯樹脂、環氧樹脂、及氟樹脂等。為了確保較高的耐熱性及水溶性，作為耐熱樹脂尤以使用選自於由聚醯亞胺樹脂及氟樹脂所構成之群組中之至少1種樹脂為佳。此外，耐熱樹脂以使用聚醯亞胺樹脂較佳。As the heat resistant resin of the present modification, for example, a polyimide resin, a polyester resin, an epoxy resin, a fluororesin or the like can be used. In order to secure high heat resistance and water solubility, it is preferable to use at least one resin selected from the group consisting of a polyimide resin and a fluororesin as the heat resistant resin. Further, the heat resistant resin is preferably a polyimide resin.

又，基底層120之組成亦會對表面處理鋼板1之組成賦予影響。所以，在本變形例中，有對表面處理皮膜100賦予加工跟從性及耐熱性，因此，基底層120含有耐熱樹脂作為主要成分。此外，在基底層120，例如係以磷酸塩、硼酸塩、矽酸鹽、鉬酸鹽、即鎢酸鹽等無機成分之含有量少於耐熱樹脂之含有量的方式進行調整。具體而言，基底層120相對於100質量份之耐熱樹脂含有0.1質量份以上且10質量份以下之無機酸鹽。當無機酸鹽之含有量小於0.1質量份，表面處理皮膜100之摩擦係數會上昇且無法獲得充分的潤滑性。另一方面，一旦無機酸鹽之含有量超過100質量份，將無法充分發揮保持潤滑劑131之基底層120之性能。Further, the composition of the base layer 120 also affects the composition of the surface-treated steel sheet 1. Therefore, in the present modification, the surface treatment film 100 is provided with process followability and heat resistance. Therefore, the base layer 120 contains a heat resistant resin as a main component. In addition, the base layer 120 is adjusted so that the content of the inorganic component such as barium phosphate, barium borate, silicate, molybdate, or tungstate is less than the content of the heat resistant resin. Specifically, the base layer 120 contains 0.1 parts by mass or more and 10 parts by mass or less of the inorganic acid salt with respect to 100 parts by mass of the heat resistant resin. When the content of the inorganic acid salt is less than 0.1 part by mass, the friction coefficient of the surface treatment film 100 rises and sufficient lubricity cannot be obtained. On the other hand, when the content of the inorganic acid salt exceeds 100 parts by mass, the performance of the base layer 120 for holding the lubricant 131 cannot be sufficiently exhibited.

又，基底層120之厚度必須在0.1μm以上且在15μm以下。當基底層120之厚度小於0.1μm，將無法充分發揮保持潤滑劑131之基底層120之性能。另一方面，一旦基底層120之厚度超過15μm，基底層120之厚度會變得過大，因此容易在冷加工時產生壓痕缺陷等。從使保持潤滑劑131之基底層120之性能提升之觀點看來，基底層120之厚度在0.5μm以上為佳。又，從進一步確實防止加工時之壓痕缺陷之觀點看來，基底層120之厚度在3μm以下為佳。Further, the thickness of the underlayer 120 must be 0.1 μm or more and 15 μm or less. When the thickness of the base layer 120 is less than 0.1 μm, the performance of the base layer 120 holding the lubricant 131 will not be sufficiently exerted. On the other hand, once the thickness of the base layer 120 exceeds 15 μm, the thickness of the base layer 120 becomes excessively large, so that indentation defects and the like are easily generated at the time of cold working. The thickness of the base layer 120 is preferably 0.5 μm or more from the viewpoint of improving the performance of the base layer 120 holding the lubricant 131. Further, from the viewpoint of further ensuring prevention of indentation defects during processing, the thickness of the underlayer 120 is preferably 3 μm or less.

<潤滑劑層130><Lubricant layer 130>

潤滑劑層130具有使表面處理皮膜100之潤滑性提升並減低摩擦係數之功能。具體上，潤滑劑層120係位在靠近表面處理皮膜100最表面之側，在構成表面處理皮膜100之3層中含有最多量之潤滑劑131。The lubricant layer 130 has a function of improving the lubricity of the surface treatment film 100 and reducing the friction coefficient. Specifically, the lubricant layer 120 is positioned on the side closest to the outermost surface of the surface treatment film 100, and the maximum amount of the lubricant 131 is contained in the three layers constituting the surface treatment film 100.

在本變形例中，潤滑劑131可形成具有傾斜型3層構造之表面處理皮膜100，且只要可充分使表面處理皮膜100之潤滑性提升，即未有特別限定。例如，作為潤滑劑131，可使用選自於由聚四氟乙烯、二硫化鉬、二硫化鎢、氧化鋅及石墨所構成之群組中之至少1種化合物。In the present modification, the lubricant 131 can form the surface treatment film 100 having the inclined three-layer structure, and is not particularly limited as long as the lubricity of the surface treatment film 100 can be sufficiently improved. For example, as the lubricant 131, at least one compound selected from the group consisting of polytetrafluoroethylene, molybdenum disulfide, tungsten disulfide, zinc oxide, and graphite can be used.

又，潤滑劑層130之厚度必須在0.1μm以上且在10μm以下。當潤滑劑層130之厚度小於0.1μm，將無法獲得充分的潤滑性。另一方面，一旦潤滑劑層130之厚度超過10μm，會產生加工時生成多餘碎屑且該多餘碎屑附著到模具等問題。從進一步使潤滑性提升之觀點看來，潤滑劑層130之厚度在1μm以上為佳。又，從進一步確實防止加工時產生多餘碎屑的觀點看來，潤滑劑層130之厚度在6μm以下為佳。Further, the thickness of the lubricant layer 130 must be 0.1 μm or more and 10 μm or less. When the thickness of the lubricant layer 130 is less than 0.1 μm, sufficient lubricity cannot be obtained. On the other hand, once the thickness of the lubricant layer 130 exceeds 10 μm, there is a problem that excess debris is generated during processing and the excess debris adheres to the mold. From the viewpoint of further improving the lubricity, the thickness of the lubricant layer 130 is preferably 1 μm or more. Further, from the viewpoint of further preventing the occurrence of excess debris during processing, the thickness of the lubricant layer 130 is preferably 6 μm or less.

此外，為了發揮上述之基底層120之功能及潤滑劑層130之功能，潤滑劑層130與基底層120之厚度之比值亦相當重要。具體上，潤滑劑層130之厚度相對於基底層120之厚度之比值-即(潤滑劑層層厚/基底層層厚)-必須在0.2以上且在10以下。當(潤滑劑層層厚/基底層層厚)小於0.2時，表面處理皮膜100(皮膜全體)會變得過硬，因而無法充分獲得潤滑性。另一方面，一旦(潤滑劑層層厚/基底層層厚)超過10，會使潤滑劑131之保持性劣化且使皮膜全體之加工跟從性不足。In addition, in order to exert the functions of the base layer 120 and the function of the lubricant layer 130 described above, the ratio of the thickness of the lubricant layer 130 to the thickness of the base layer 120 is also important. Specifically, the ratio of the thickness of the lubricant layer 130 to the thickness of the base layer 120 - that is, (lubricant layer thickness / base layer thickness) - must be 0.2 or more and 10 or less. When the (lubricant layer thickness/base layer thickness) is less than 0.2, the surface treatment film 100 (the entire film) becomes too hard, and thus the lubricity cannot be sufficiently obtained. On the other hand, when the (lubricant layer thickness/base layer thickness) exceeds 10, the retainability of the lubricant 131 is deteriorated and the processing of the entire film is insufficient.

<層形成之確認方法、各層膜厚之測定方法及決定方法><Method for confirming layer formation, method for measuring film thickness of each layer, and method for determining>

如以上說明，在本變形例之表面處理鋼板1中，靠近鋼板10之側之密接層110、靠近皮膜表面之側之潤滑劑層130、及該等間之基底層120之3層之存在相當重要。該等層中，只要欠缺其中一層，便難以發揮本變形例中所意圖的可承受冷加工之潤滑性。又，若密接層110、基底層120、及潤滑劑層130之各層厚度不在上述範圍內，亦難以發揮本變形例中所意圖的可承受冷加工之潤滑性。因此，在本變形例中，確認是否有形成密接層110、基底層120、及潤滑劑層130之各層之方法，及測定該等各層厚度之方法亦相當重要。As described above, in the surface-treated steel sheet 1 of the present modification, the presence of the adhesion layer 110 on the side close to the steel sheet 10, the lubricant layer 130 on the side close to the surface of the coating film, and the three layers of the base layer 120 between the substrates are equivalent. important. In such a layer, as long as one of the layers is missing, it is difficult to exhibit the lubricity which can withstand cold working as intended in the present modification. Moreover, when the thickness of each layer of the adhesion layer 110, the base layer 120, and the lubricant layer 130 is out of the above range, it is also difficult to exhibit the lubricity which can be subjected to cold working as intended in the present modification. Therefore, in the present modification, it is also important to confirm whether or not the respective layers of the adhesion layer 110, the underlayer 120, and the lubricant layer 130 are formed, and the method of measuring the thickness of each layer.

首先，有關確認密接層110、基底層120、及潤滑劑層130之各層形成之方法，可使用高頻波GDS進行表面處理皮膜100之膜厚方向(深度方向)之元素定量分析來確認各層之形成。即，首先，設定含於表面處理皮膜100之主要成分(起因於矽醇鍵結之成分、無機酸鹽、耐熱樹脂、及潤滑劑)之代表元素(就其成分而言為特徵性之元素)。例如，就起因於矽醇鍵結之成分，理想上可將Si設定為代表元素。又，例如，就潤滑劑而言，理想上當潤滑劑為聚四氟乙烯時可將F設定為代表元素，當潤滑劑為二硫化鉬時可將Mo設定為代表元素。接下來，在高頻波GDS之測定表中，求出相當於該等代表元素之峰值強度，並從所求之峰值強度依膜厚方向之每一位置算出各成分之濃度。First, in order to confirm the formation of each layer of the adhesion layer 110, the underlayer 120, and the lubricant layer 130, elemental quantitative analysis in the film thickness direction (depth direction) of the surface treatment film 100 can be performed using the high-frequency wave GDS to confirm the formation of each layer. In other words, first, a representative element (a component which is characteristic of the component) which is a main component (a component derived from a sterol bond, a mineral acid salt, a heat resistant resin, and a lubricant) contained in the surface treatment film 100 is set. . For example, Si is desirably set as a representative element due to a component derived from a sterol bond. Further, for example, in the case of a lubricant, it is desirable to set F as a representative element when the lubricant is polytetrafluoroethylene, and to set Mo as a representative element when the lubricant is molybdenum disulfide. Next, in the measurement table of the high-frequency wave GDS, the peak intensity corresponding to the representative elements is obtained, and the concentration of each component is calculated from the obtained peak intensity in each of the film thickness directions.

有關本變形例之各層厚度之決定方法規定如下。The method for determining the thickness of each layer in the present modification is defined as follows.

首先，潤滑劑層130之厚度係從表面處理皮膜100之最表面起，到下述膜厚方向之位置(深度)為止之距離：在高頻波GDS之測定表中，具有如上述所設定之潤滑劑之代表元素(例如，F、Mo、W、Zn、C)中峰值強度最大值之1/2之峰值強度。即，潤滑劑層130與基底層120之界面，與潤滑劑之代表元素之峰值強度成為峰值強度之最大值之1/2之膜厚方向之位置一致。First, the thickness of the lubricant layer 130 is a distance from the outermost surface of the surface treatment film 100 to the position (depth) in the film thickness direction: in the measurement table of the high-frequency wave GDS, the lubricant is set as described above. The peak intensity of 1/2 of the peak intensity maximum in the representative elements (for example, F, Mo, W, Zn, C). That is, the interface between the lubricant layer 130 and the base layer 120 coincides with the position in the film thickness direction in which the peak intensity of the representative element of the lubricant becomes 1/2 of the maximum value of the peak intensity.

又，密接層110之厚度係從表面處理皮膜100與鋼板10之界面起，到高頻波GDS之測定表中，具有起因於矽醇鍵結之成分之代表元素(Si)之峰值強度之最大值之1/2之峰值強度的膜厚方向之位置(深度)為止之距離。即，密接層110與基底層120之界面，與起因於矽醇鍵結之成分之代表元素(Si)之峰值強度為峰值強度之最大值之1/2之膜厚方向之位置一致。Further, the thickness of the adhesion layer 110 is the maximum value of the peak intensity of the representative element (Si) of the component derived from the sterol bond from the interface between the surface treatment film 100 and the steel sheet 10 to the measurement table of the high-frequency wave GDS. The distance from the position (depth) in the film thickness direction of the peak intensity of 1/2. That is, the interface between the adhesion layer 110 and the underlayer 120 coincides with the position in the film thickness direction in which the peak intensity of the representative element (Si) due to the sterol-bonded component is 1/2 of the maximum value of the peak intensity.

此外，基底層120之厚度係從具有潤滑劑之代表元素之峰值強度之最大值之1/2之峰值強度的位置起，到具有起因於矽醇鍵結之成分之代表元素(Si)之峰值強度之最大值之1/2之峰值強度的位置為止之距離。而，例如，亦可使用顯微鏡觀察表面處理皮膜100之剖面，求算表面處理皮膜100全體厚度，並從該表面處理皮膜100全體厚度減去上述所求之密接層110及潤滑劑層130之合計厚度，以求算基底層120之厚度。Further, the thickness of the base layer 120 is from the position of the peak intensity of 1/2 of the maximum value of the peak intensity of the representative element of the lubricant to the peak of the representative element (Si) having the component derived from the sterol bond. The distance from the position of the peak intensity of 1/2 of the maximum value of the intensity. For example, the cross section of the surface treatment film 100 may be observed with a microscope, and the total thickness of the surface treatment film 100 may be calculated, and the total thickness of the adhesion layer 110 and the lubricant layer 130 obtained as described above may be subtracted from the total thickness of the surface treatment film 100. The thickness is used to calculate the thickness of the base layer 120.

但，當使用石墨作為潤滑劑131時，若將碳(C)設定為決定潤滑劑層130與基底層120之界面之代表元素，將難以區別潤滑劑131中之C與來自耐熱樹脂等之C。所以，使用無機酸鹽之代表元素(如：P、B、Si)來求算潤滑劑層130之厚度。此時，潤滑劑層130與基底層120之界面，與無機酸鹽之代表元素之峰值強度為峰值強度之最大值之1/2之膜厚方向之位置一致。However, when graphite is used as the lubricant 131, if carbon (C) is set as a representative element determining the interface between the lubricant layer 130 and the base layer 120, it is difficult to distinguish C in the lubricant 131 from C in the heat resistant resin or the like. . Therefore, the representative elements of the inorganic acid salt (e.g., P, B, Si) are used to calculate the thickness of the lubricant layer 130. At this time, the interface between the lubricant layer 130 and the underlayer 120 coincides with the position in the film thickness direction in which the peak intensity of the representative element of the inorganic acid salt is 1/2 of the maximum value of the peak intensity.

又，當使用矽酸鹽作為基底層120之無機酸鹽時，若將矽(Si)設定為決定基底層120與密接層110之界面之代表元素，將難以區別來自矽酸鹽(無機酸鹽)之Si及來自密接層110之起因於矽醇鍵結之成分之Si。所以，使用來自基底層120之耐熱樹脂成分之碳(C)作為代表元素，以求算密接層110及基底層120之厚度。此外，當使用鉬酸鹽或鎢酸鹽作為基底層120之無機酸鹽時，若將鉬(Mo)或鎢(W)設定為決定潤滑劑層130與基底層120之界面之代表元素，將難以區別來自無機酸鹽之Mo或W、及來自潤滑劑131之Mo或W。所以，使用來自潤滑劑131之硫磺(S)作為代表元素，以求算基底層120及潤滑劑層130之厚度。Further, when niobate is used as the inorganic acid salt of the underlayer 120, if yttrium (Si) is set as a representative element which determines the interface between the underlying layer 120 and the adhesion layer 110, it will be difficult to distinguish from the niobate (mineral acid salt). Si and Si derived from the adhesion layer 110 due to the sterol-bonded component. Therefore, carbon (C) derived from the heat resistant resin component of the base layer 120 is used as a representative element to calculate the thickness of the adhesion layer 110 and the base layer 120. Further, when molybdate or tungstate is used as the inorganic acid salt of the base layer 120, if molybdenum (Mo) or tungsten (W) is set as a representative element determining the interface between the lubricant layer 130 and the base layer 120, It is difficult to distinguish Mo or W from the inorganic acid salt, and Mo or W from the lubricant 131. Therefore, sulfur (S) from the lubricant 131 is used as a representative element to calculate the thickness of the base layer 120 and the lubricant layer 130.

而，就各層厚度之算出方法，可從高頻波GDS之濺鍍時間(本變形例中係以SiO2 之濺鍍速度所換算之時間)，求算具有各成分之代表元素之峰值強度之最大值之1/2之峰值強度的位置，即，表面處理皮膜100之膜厚方向之位置。Further, in the calculation method of the thickness of each layer, the maximum value of the peak intensity of the representative element having each component can be calculated from the sputtering time of the high-frequency wave GDS (the time converted by the sputtering rate of SiO 2 in the present modification). The position of the peak intensity of 1/2, that is, the position of the surface treatment film 100 in the film thickness direction.

此外，在本變形例中，基底層120相對於100質量份之耐熱樹脂，含有0.01質量份以上且10質量份以下之無機酸鹽。測定該基底層120中之耐熱樹脂及無機酸鹽之質量之方法如下。藉由微切片機等將皮膜在厚度方向進行研磨並削出基底層。將該皮膜採取出可分析之量後，再以瑪瑙乳缽進行粉碎。測定粉碎後經回收之皮膜之初始重量後，添加水使無機酸鹽(無機化合物)溶解。使無機酸鹽溶解後讓皮膜充分乾燥。將乾燥後之皮膜重量決定作為耐熱樹脂之質量份，並將初始重量與乾燥後之皮膜重量之差分決定作為無機酸鹽之質量份。In addition, in the present modification, the base layer 120 contains 0.01 parts by mass or more and 10 parts by mass or less of the inorganic acid salt based on 100 parts by mass of the heat resistant resin. The method of measuring the quality of the heat resistant resin and the inorganic acid salt in the base layer 120 is as follows. The film is ground in the thickness direction by a microtome or the like and the base layer is cut. The film was taken out in an analytical amount and then pulverized in an agate mortar. After the initial weight of the recovered film after the pulverization was measured, water was added to dissolve the inorganic acid salt (inorganic compound). After the inorganic acid salt is dissolved, the film is sufficiently dried. The weight of the film after drying is determined as the mass part of the heat resistant resin, and the difference between the initial weight and the weight of the film after drying is determined as the mass part of the inorganic acid salt.

[表面處理鋼板之製造方法][Method of Manufacturing Surface-treated Steel Sheet]

以上，已詳細說明表面處理鋼板之構成。接下來，說明具有此種構成之表面處理鋼板之製造方法。The structure of the surface-treated steel sheet has been described in detail above. Next, a method of manufacturing a surface-treated steel sheet having such a configuration will be described.

在該表面處理鋼板之製造方法中，將包含水溶性矽烷耦合劑、水溶性無機酸鹽、水溶性耐熱樹脂及潤滑劑之水系表面處理液塗佈於鋼板10(上述實施形態之鋼板)之至少一面後使表面處理液乾燥，藉以在鋼板10之至少一面形成表面處理皮膜100。In the method for producing a surface-treated steel sheet, an aqueous surface treatment liquid containing a water-soluble decane coupling agent, a water-soluble inorganic acid salt, a water-soluble heat-resistant resin, and a lubricant is applied to at least the steel sheet 10 (the steel sheet of the above embodiment). The surface treatment liquid is dried after one side, whereby the surface treatment film 100 is formed on at least one side of the steel sheet 10.

(表面處理液)(surface treatment liquid)

用於表面處理鋼板之製造方法之表面處理液包含水溶性矽烷耦合劑、水溶性無機酸鹽、水溶性耐熱樹脂及潤滑劑，因無機酸鹽、耐熱樹脂及潤滑劑之詳細已於上述，故在此省略說明。The surface treatment liquid for the surface treatment steel plate manufacturing method comprises a water-soluble decane coupling agent, a water-soluble inorganic acid salt, a water-soluble heat-resistant resin, and a lubricant. The details of the inorganic acid salt, the heat resistant resin, and the lubricant are as described above. Description is omitted here.

水溶性矽烷耦合劑並未有特別限定，可為公知的矽烷耦合劑。例如，作為該水溶性矽烷耦合劑可使用3-胺基丙基三甲氧矽烷、N-2-(胺基甲基)-3-胺基丙基甲基二甲氧矽烷、3-縮水甘油氧丙基三甲氧矽烷、及3-縮水甘油氧丙基三乙氧矽烷等。The water-soluble decane coupling agent is not particularly limited and may be a known decane coupling agent. For example, as the water-soluble decane coupling agent, 3-aminopropyltrimethoxydecane, N-2-(aminomethyl)-3-aminopropylmethyldimethoxydecane, 3-glycidyloxy can be used. Propyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and the like.

又，於上述表面處理液中亦可添加各種添加劑。Further, various additives may be added to the surface treatment liquid.

用於表面處理鋼板之製造方法之表面處理液，只要在未損傷本變形例之效果的範圍內，可使用使塗敷性提升之調平劑或水溶性溶劑、金屬穩定劑、抗蝕劑及調整劑等。調平劑可使用非離子系或陽離子系之界面活性劑。作為該調平劑，例如有：聚乙烯氧化物、聚丙烯氧化物加成物及乙炔二醇化合物等。水溶性溶劑例如有：乙醇、異丙醇、三級丁醇及丙二醇等醇類；乙二醇一丁基醚、乙二醇一乙基醚等賽珞蘇類；乙酸乙酯、乙酸丁酯等酯類；及丙酮、甲基乙基酮及甲基異丁基酮等酮類等。金屬穩定劑例如有EDTA、DTPA等螯合化合物。抗蝕劑例如有乙二胺、三乙烯五胺、胍及嘧啶等胺化合物類，尤其，由於一分子內含有2個以上之胺基之胺化合物亦具有作為金屬穩定劑之效果，因此，使用此種胺化合物作為抗蝕劑較佳。pH調整劑例如有：乙酸及乳酸等有機酸類、氟酸等無機酸類、及銨鹽或胺類等。As the surface treatment liquid for the method for producing a surface-treated steel sheet, a leveling agent or a water-soluble solvent, a metal stabilizer, a resist, and the like which improve the coating property can be used as long as the effect of the present modification is not impaired. Adjusting agent, etc. As the leveling agent, a nonionic or cationic surfactant can be used. Examples of the leveling agent include a polyethylene oxide, a polypropylene oxide adduct, and an acetylene glycol compound. Examples of the water-soluble solvent include alcohols such as ethanol, isopropanol, tertiary butanol, and propylene glycol; celecoxime such as ethylene glycol monobutyl ether and ethylene glycol monoethyl ether; ethyl acetate and butyl acetate; And other esters; and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone. The metal stabilizer is, for example, a chelate compound such as EDTA or DTPA. The resist is, for example, an amine compound such as ethylenediamine, triethylenepentamine, anthracene or pyrimidine. In particular, since an amine compound containing two or more amine groups in one molecule also has an effect as a metal stabilizer, it is used. Such an amine compound is preferred as the resist. Examples of the pH adjuster include organic acids such as acetic acid and lactic acid, inorganic acids such as hydrofluoric acid, and ammonium salts or amines.

藉由使上述之各成分均勻地溶解或分散至水中，可調製用於表面處理鋼板之製造方法之表面處理液。The surface treatment liquid for the surface-treated steel sheet can be prepared by uniformly dissolving or dispersing the above components in water.

(表面處理液之塗佈及乾燥)(coating and drying of surface treatment liquid)

作為對上述表面處理液之鋼板10之塗佈方法，例如可使用將鋼板10浸泡到表面處理液中之方法等。此時，必須事先將鋼板10加溫到較表面處理液之溫度更高的溫度，或在乾燥際以溫熱風使其乾燥。具體而言，例如，將鋼板10浸泡於80℃左右之熱水中1分鐘左右之後，再浸泡至40℃~60℃溫度之表面處理液中1秒鐘左右，之後以室溫使其乾燥2分鐘左右。藉由此種方法，可形成由密接層110、基底層120及潤滑劑層130所形成之3層構造之傾斜型表面處理皮膜100。As a method of applying the steel sheet 10 to the surface treatment liquid, for example, a method of immersing the steel sheet 10 in the surface treatment liquid or the like can be used. At this time, the steel sheet 10 must be warmed to a temperature higher than the temperature of the surface treatment liquid in advance, or dried by a warm air at the time of drying. Specifically, for example, the steel sheet 10 is immersed in hot water of about 80 ° C for about 1 minute, and then immersed in a surface treatment liquid at a temperature of 40 ° C to 60 ° C for about 1 second, and then dried at room temperature. Minutes or so. By this method, the inclined surface treatment film 100 having a three-layer structure formed of the adhesion layer 110, the base layer 120, and the lubricant layer 130 can be formed.

(各層膜厚之控制方法)(How to control the film thickness of each layer)

構成表面處理皮膜100之各層膜厚可藉由適當控制表面處理液之塗佈量、表面處理液中之各成分濃度、表面處理液與心材之鋼板10之反應性、及表面處理液之親水性/疏水性，而調整在如上述之膜厚範圍內。The thickness of each layer constituting the surface treatment film 100 can be appropriately controlled by the coating amount of the surface treatment liquid, the concentration of each component in the surface treatment liquid, the reactivity of the surface treatment liquid with the steel sheet 10 of the heart material, and the hydrophilicity of the surface treatment liquid. /hydrophobic, and adjusted within the film thickness range as described above.

(形成傾斜型皮膜之理由)(The reason for forming a slanted film)

如以上，有關將水溶性矽烷耦合劑、水溶性無機酸鹽、水溶性耐熱樹脂及潤滑劑溶解或分散於水中之表面處理液，塗佈到鋼板10之後進行乾燥，藉以形成傾斜型表面處理皮膜100之理由，本發明人等推定如下。首先，如上述若事先將鋼板10加溫至較表面處理液之溫度更高的溫度，則鋼板10之溫度會高於表面處理液之溫度，因此，在已將表面處理液塗佈到鋼板10上所形成之薄膜內，固液界面之溫度會很高且氣液界面之溫度很低。所以，薄膜內會產生溫度差，且溶劑之水會揮發而在薄膜內引起微小的對流。又，在藉由溫熱風將已對常溫的鋼板10塗佈常溫的表面處理液所形成之薄膜進行乾燥的情況下，氣液界面之溫度會變高且氣液界面之表面張力會降低而緩和溫度變化與表面張力變化，因而在薄膜內會引起微小的對流。上述中任一塗佈乾燥方法皆會引起對流，且表面處理液會分離成與空氣具有高親和力之成分(如潤滑劑)，及與金屬或水具有高親和力之成分(如無機酸鹽或耐熱樹脂)。之後，水會徐緩地揮發使表面處理液呈膜狀而形成具有各成分之濃度梯度之傾斜型皮膜。As described above, the surface treatment liquid in which the water-soluble decane coupling agent, the water-soluble inorganic acid salt, the water-soluble heat-resistant resin, and the lubricant are dissolved or dispersed in water is applied to the steel sheet 10 and then dried to form an inclined surface treatment film. The reason for the reason of 100 is estimated by the present inventors as follows. First, if the steel sheet 10 is heated to a temperature higher than the temperature of the surface treatment liquid in advance as described above, the temperature of the steel sheet 10 is higher than the temperature of the surface treatment liquid, and therefore, the surface treatment liquid has been applied to the steel sheet 10 In the film formed above, the temperature of the solid-liquid interface is high and the temperature of the gas-liquid interface is very low. Therefore, a temperature difference occurs in the film, and the water of the solvent volatilizes to cause minute convection in the film. When the film formed by applying the surface treatment liquid at normal temperature to the normal temperature steel sheet 10 is dried by warm air, the temperature at the gas-liquid interface is increased and the surface tension at the gas-liquid interface is lowered. It moderates temperature changes and surface tension changes, thus causing slight convection in the film. Any of the above coating drying methods causes convection, and the surface treatment liquid is separated into components having high affinity with air (such as a lubricant), and components having high affinity with metal or water (such as inorganic acid salts or heat resistance). Resin). Thereafter, the water is volatilized slowly so that the surface treatment liquid is in a film form to form an inclined film having a concentration gradient of each component.

又，在本變形例中，由於矽烷耦合劑與鋼板10表面之金屬的親和力很高，因此矽烷耦合劑在薄膜內會往鋼板10附近擴散。之後，到達鋼板10附近的矽烷耦合劑與存於鋼板10表面之金屬氧化物(例如，已對鋼板10施加鋅鍍敷時係氧化鋅)之間形成共價鍵，而形成以Si-O-X表示之矽醇鍵結。如此一來，一旦在鋼板10附近形成矽醇鍵結，便可使表面處理皮膜100與鋼板10之密接性提升許多，因而可防止燒黏及擦傷之生成。Further, in the present modification, since the affinity of the decane coupling agent to the metal on the surface of the steel sheet 10 is high, the decane coupling agent diffuses into the vicinity of the steel sheet 10 in the film. Thereafter, a decane coupling agent reaching the vicinity of the steel sheet 10 forms a covalent bond with a metal oxide deposited on the surface of the steel sheet 10 (for example, zinc oxide is applied when zinc plating is applied to the steel sheet 10), and is formed by Si-OX. The sterol bond. As a result, once the sterol bond is formed in the vicinity of the steel sheet 10, the adhesion between the surface treatment film 100 and the steel sheet 10 can be greatly improved, thereby preventing the formation of sticking and scratching.

[與其他表面處理方法之比較及本變形例之總結][Comparison with other surface treatment methods and summary of this modification]

而，在冷加工中，因鋼板與模具之間之摩擦會使鋼板與模具之接觸部分的溫度變得比較高(大概300℃以上)。所以，若將尚未施加有任何表面處理之鋼板進行冷加工，當鋼板與模具間之潤滑性不夠充分時，鋼板與模具之間容易產生燒黏或擦傷。此時，模具可能會產生局部破損或嚴重的磨損，因而明顯縮短模具之壽命。However, in cold working, the temperature between the steel sheet and the mold becomes relatively high (about 300 ° C or more) due to the friction between the steel sheet and the mold. Therefore, if the steel sheet to which no surface treatment has been applied is subjected to cold working, when the lubricity between the steel sheet and the mold is insufficient, the steel sheet and the mold are likely to be burnt or scratched. At this time, the mold may be partially damaged or severely worn, thereby significantly shortening the life of the mold.

為了防止此種燒黏或擦傷，一般係對鋼板施加一種如冷加工之對進行冷加工之鋼板表面賦予潤滑性之表面處理(以下時而稱為「潤滑處理」)。此種潤滑處理自習知已知有磷酸鹽處理(磷酸鹽防蝕處理)，可在鋼板表面形成由磷酸鹽化合物(磷酸鋅、磷酸錳、磷酸鈣、及磷酸鐵等)所構成之磷酸鹽皮膜。In order to prevent such sticking or scratching, a surface treatment (hereinafter referred to as "lubrication treatment") which imparts lubricity to the surface of the steel sheet which is subjected to cold working, such as cold working, is generally applied to the steel sheet. Such a lubricating treatment is known from the prior art as a phosphate treatment (phosphate anticorrosive treatment), and a phosphate film composed of a phosphate compound (zinc phosphate, manganese phosphate, calcium phosphate, and iron phosphate, etc.) can be formed on the surface of the steel sheet.

經磷酸鹽處理之鋼板在防燒黏性能及防擦傷性能相對較高。然而，以近年環境對策為背景，隨著從熱鍛造及切削加工等形狀變形很大的加工領域進展轉移到冷加工，就冷加工用鋼板而言，必須進行更加嚴密的塑性加工。從此觀點看來，現今，是在磷酸鹽皮膜上廣泛使用積層有由金屬皂(如硬脂酸鈉等)所構成之層之複合皮膜。該複合皮膜在冷加工時之高面壓之擠壓的嚴苛摩擦條件下，亦具有良好的防燒黏性能及防擦傷性能。The phosphate-treated steel sheet has relatively high anti-burning properties and anti-scratch properties. However, in recent years, in the context of environmental measures, it has been necessary to carry out more rigorous plastic working for steel sheets for cold working in accordance with the progress in the field of processing in which shape deformation such as hot forging and cutting is greatly changed to cold working. From this point of view, a composite film in which a layer composed of a metal soap (such as sodium stearate) is laminated on a phosphate film is widely used today. The composite film also has good anti-sticking properties and anti-scratch properties under the severe friction conditions of high surface pressure extrusion during cold working.

若以該潤滑處理形成複合皮膜，金屬皂可藉由與磷酸鹽皮膜起反應而發揮高潤滑性。然而，該潤滑處理需要洗淨步驟，或使金屬皂與磷酸鹽皮膜起反應之反應步驟(亦需要處理液之管理及反應時之溫度管理等步驟管理)等諸多的煩雜處理步驟，又，由於為批次處理，因此有生產性降低之問題。又，在使用複合皮膜之潤滑處理中，亦有處理時所產生之廢棄液處理等問題，因此從環境保護之觀點看來不甚理想。When the composite film is formed by the lubricating treatment, the metal soap can exhibit high lubricity by reacting with the phosphate film. However, the lubrication treatment requires a washing step or a reaction step of reacting the metal soap with the phosphate film (the management of the treatment liquid and the temperature management during the reaction, etc.), and the like, and For batch processing, there is a problem of reduced productivity. Further, in the lubrication treatment using the composite film, there are also problems such as the disposal of the waste liquid generated during the treatment, which is not preferable from the viewpoint of environmental protection.

另一方面，在本變形例中，表面處理鋼板可以簡便的處理步驟製造，且從地球環境保護之觀點看來亦可以適當的方法加以製造，還具有良好的潤滑性。因此，以近年的環境對策為背景，可將加工方法從能量消耗量諸多的熱鍛造、或會產生多量材料損失的切削加工等形狀變形較大的加工領域，轉移到冷加工。再加上，藉由上述使用表面處理鋼板，即使在需要更加嚴密的塑性加工或複雜加工之情況下，亦不會與模具產生燒黏或擦傷而可毫無問題地加工材料(鋼板)。尤其，若在可適當使用於嚴苛的冷加工之上述實施形態之鋼板表面，形成可適當使用於嚴苛的冷加工之表面處理皮膜，即可獲得材料之鋼板之加工性與表面處理皮膜之鋼板跟從性的相乘效果(一體成型的加工性)。因此，即便對鋼板進行冷加工，亦不會使模具壽命降低且可確保充分的加工性。此外，若將本變形例之冷加工用中碳鋼板適用於冷加工及高頻淬火，即可以高成品率製造藉由上述相乘效果而具有良好的機械特性之零件，進而達成節省資源化及節能化。On the other hand, in the present modification, the surface-treated steel sheet can be produced by a simple process, and can be produced by an appropriate method from the viewpoint of global environmental protection, and has good lubricity. Therefore, in the context of environmental measures in recent years, the processing method can be shifted to cold working from a processing field in which the shape of the energy is greatly reduced, such as hot forging or a large amount of material loss. Further, by using the surface-treated steel sheet as described above, even if more complicated plastic working or complicated processing is required, the material (steel sheet) can be processed without any problem of sticking or scratching with the mold. In particular, when the surface of the steel sheet of the above-described embodiment which can be suitably used for severe cold working is formed, a surface treatment film which can be suitably used for severe cold working is formed, and the workability of the steel sheet of the material and the steel sheet of the surface treated film can be obtained. Sexual multiplication effect (integral processability). Therefore, even if the steel sheet is cold worked, the life of the mold is not lowered and sufficient workability can be ensured. Further, when the medium-carbon steel sheet for cold working of the present modification is applied to cold working and high-frequency quenching, it is possible to manufacture a part having excellent mechanical properties by the above-described multiplication effect at a high yield, thereby achieving resource saving and energy saving. .

以上，已參考附加圖式詳細說明本發明之適當實施形態，惟，本發明並非受限於該等例。很明顯地，只要為具有本發明所述之技術領域之一般知識者，便可在專利申請範圍中所記載之技術性思想範疇內，聯想到各種變更例或修正例，想當然耳，有關該等理應亦屬於本發明之技術性範圍內。The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the invention is not limited by the examples. Obviously, as long as it is a general knowledge of the technical field of the invention, it is possible to associate various modifications or corrections within the scope of the technical idea described in the scope of the patent application. It is also within the technical scope of the present invention.

實施例Example

接下來，說明本發明之實施例，惟，實施例之條件係用以確認本發明之可實施性及效果所採用之一條件例，本發明並非受限於該一條件例。本發明只要未脫離本發明之主旨且可達成本發明之目的，可採用各種條件。Next, the examples of the present invention are described, but the conditions of the examples are examples of conditions for confirming the applicability and effects of the present invention, and the present invention is not limited to the conditions. The present invention can adopt various conditions as long as it does not depart from the gist of the present invention and can achieve the object of the invention.

將具有表1中顯示之成分組成之鋼加以熔解、熱軋及退火，製造硬度、碳化物徑長及碳化物之球化率不同的鋼板，以調查冷加工性與高頻淬火硬度。以下說明該鋼板之製造方法。The steel having the composition shown in Table 1 was melted, hot rolled, and annealed to produce a steel sheet having different hardness, carbide length, and spheroidization rate of carbide to investigate cold workability and high frequency quenching hardness. The method for producing the steel sheet will be described below.

將板厚150mm之鋼塊(鑄片)以1220℃保持2hr後，以軋延結束溫度870℃之條件進行熱軋，而獲得板厚6mm之熱軋鋼板。之後，將該熱軋鋼板以表2~7中顯示之第一平均冷卻速度冷卻至第一冷卻溫度後，以表2~7中顯示之第二平均冷卻速度冷卻至第二冷卻溫度，再進行捲取及空氣冷卻。又，確認從550℃至400℃有在30小時以下。A steel block (casting piece) having a thickness of 150 mm was held at 1220 ° C for 2 hr, and then hot rolled at a rolling end temperature of 870 ° C to obtain a hot rolled steel sheet having a thickness of 6 mm. Thereafter, the hot-rolled steel sheet is cooled to a first cooling temperature at a first average cooling rate shown in Tables 2 to 7, and then cooled to a second cooling temperature at a second average cooling rate shown in Tables 2 to 7, and then performed. Coiling and air cooling. Further, it was confirmed that the temperature was from 550 ° C to 400 ° C for 30 hours or less.

從所製得之各熱軋鋼板，在板厚方向切削表層2.0mm且裏層2.0mm而獲得板厚2mm(對應於鋼No.A、B、C、K、L)之試樣。又，從同樣的製造條件之各熱軋鋼板切削表層0.5mm且裏層0.5mm而獲得板厚5mm(對應於鋼No.D、E、M、N、O、P、Q)之試樣。From the obtained hot-rolled steel sheets, a surface layer of 2.0 mm and an inner layer of 2.0 mm were cut in the thickness direction to obtain a sample having a thickness of 2 mm (corresponding to steel No. A, B, C, K, L). Further, samples of a thickness of 5 mm (corresponding to steel No. D, E, M, N, O, P, Q) were obtained by cutting a surface layer of 0.5 mm and an inner layer of 0.5 mm from each of the hot-rolled steel sheets of the same production conditions.

同樣地，將在真空環境下所熔製之板厚150mm之鋼塊以1240℃保持1.5hr後，以軋延結束溫度920度之條件進行熱軋而製得板厚16mm之熱軋鋼板。之後，將該鋼板以表2~7中顯示之第一平均冷卻速度冷卻至第一冷卻溫度後，以表2~7中顯示之第二平均冷卻速度冷卻至第二冷卻溫度，再進行捲取及空氣冷卻。又，確認從550℃至400℃有在30小時以下。Similarly, a steel block having a thickness of 150 mm which was melted in a vacuum atmosphere was held at 1,240 ° C for 1.5 hr, and then hot rolled at a rolling end temperature of 920 ° to obtain a hot-rolled steel sheet having a thickness of 16 mm. Thereafter, the steel sheet is cooled to a first cooling temperature at a first average cooling rate shown in Tables 2-7, and then cooled to a second cooling temperature at a second average cooling rate shown in Tables 2-7, and then coiled. And air cooling. Further, it was confirmed that the temperature was from 550 ° C to 400 ° C for 30 hours or less.

從上述各熱軋鋼板切削表層3.5mm且裏層3.5mm而獲得板厚9mm(對應於鋼No.F、G、R、U、V)之試樣。又，從同樣製造條件之熱軋鋼板切削表裏層之2.0mm而獲得板厚12mm(對應於鋼No.H、W、X、Y)。此外，亦將未施加切削之板厚16mm(對應於鋼No.I、J、Z、AA、AB)之熱軋鋼板作為試樣使用。A sample having a thickness of 9 mm (corresponding to steel No. F, G, R, U, V) was obtained by cutting 3.5 mm of the surface layer and 3.5 mm of the inner layer of each of the hot-rolled steel sheets. Further, a plate thickness of 12 mm (corresponding to steel No. H, W, X, Y) was obtained by cutting 2.0 mm of the inner layer of the hot-rolled steel sheet of the same production conditions. Further, a hot-rolled steel sheet having a plate thickness of 16 mm (corresponding to steel No. I, J, Z, AA, AB) to which no cutting was applied was also used as a sample.

以熱膨脹試驗測定各試樣之Ac1 溫度。在此，該熱膨脹試驗中係以接近實體機器之箱式退火爐之平均加熱速度30℃/hr進行加熱時，將沃斯田鐵變態開始之溫度決定作為Ac1 溫度。The A c1 temperature of each sample was measured by a thermal expansion test. Here, in the thermal expansion test, when the heating is performed at an average heating rate of 30 ° C / hr in a box annealing furnace close to a physical machine, the temperature at which the Worth iron is metamorphosed is determined as the A c1 temperature.

在氫氣95%環境下將各試樣(對應於鋼No.A~AB)分別以下列6種條件進行退火：680℃/3hr(對應於表2)、680℃/30hr(對應於表3)、700℃/30hr(對應於表4)、740℃/10hr(對應於表5)、700℃/90hr(對應於表6)、及700℃/60hr(對應於表7)。對以680℃及700℃退火之試樣保存(holding)(退火)完畢後，再進行爐內冷卻。對以740℃退火之試樣保存完畢後，以2℃/秒之平均冷卻速度冷卻到700℃再進行爐內冷卻。而，例如，以680℃退火3hr之試樣(鋼板No.A-1~AB-1)係顯示在表2中，鋼板No.A-1~AB-1之試樣分別從具有鋼No.A~AB之化學組成之試樣所製作。Each sample (corresponding to steel No. A to AB) was annealed under the following six conditions in a hydrogen atmosphere of 95%: 680 ° C / 3 hr (corresponding to Table 2), 680 ° C / 30 hr (corresponding to Table 3) 700 ° C / 30 hr (corresponding to Table 4), 740 ° C / 10 hr (corresponding to Table 5), 700 ° C / 90 hr (corresponding to Table 6), and 700 ° C / 60 hr (corresponding to Table 7). After the sample (annealing) of the sample annealed at 680 ° C and 700 ° C is completed, the furnace is cooled. After the sample annealed at 740 ° C was stored, it was cooled to 700 ° C at an average cooling rate of 2 ° C / sec and then cooled in the furnace. For example, a sample annealed at 680 ° C for 3 hr (steel plate No. A-1 to AB-1) is shown in Table 2, and samples of the steel sheets No. A-1 to AB-1 are respectively obtained from steel No. A sample of the chemical composition of A~AB was produced.

在高頻淬火試驗中，在頻率78kHz將各試樣(鋼板No.A-1~AB-6)在750℃以上以100±15℃/秒之平均加熱速度從室溫升溫至1000±20℃後，以1000±20℃保持10±0.5s，再立刻以200±10℃/秒之平均冷卻速度在800℃至400℃之間急速冷卻至室溫，並測定出淬火材之維氏硬度(淬火硬度)。又，從各試樣製作寬30mm且長100mm之平板彎曲試驗片，以將彎曲半徑設為板厚之1/2且將彎曲角度設為90°之條件實施彎曲試驗，並在平板彎曲試樣之彎曲角部(最大曲率部)之板厚剖面，以掃描型電子顯微鏡在倍率3000倍測定板厚1/8~3/8、及5/8~7/8之區域之龜裂數。當上述龜裂數在每1mm2 為20個以內時，可判斷為有抑制住冷加工時因界面剝離所造成的龜裂生成，故而將冷加工性評估為“良好”。又，當龜裂數超過20個時，係將冷加工性評估為“差”。而，將該等龜裂依各種類(雪明碳鐵起點之龜裂、硫化物起點之龜裂、及粒內龜裂)加以分類結算。為了區別雪明碳鐵起點之龜裂與硫化物起點之龜裂，使用附屬於掃描型電子顯微鏡之能量色散X射線光譜儀(EDS)。又，平均碳化物徑長及碳化物之球化率係以上述方法所測定。In the induction hardening test, each sample (steel plate No. A-1 to AB-6) was heated from room temperature to 1000 ± 20 ° C at an average heating rate of 100 ± 15 ° C / sec at 750 ° C or higher at a frequency of 78 kHz. Thereafter, the temperature was maintained at 1000±20° C. for 10±0.5 s, and then immediately cooled to room temperature between 800° C. and 400° C. at an average cooling rate of 200±10° C./second, and the Vickers hardness of the quenched material was measured ( Quenching hardness). Further, a flat bending test piece having a width of 30 mm and a length of 100 mm was produced from each sample, and a bending test was performed under the condition that the bending radius was 1/2 of the thickness of the plate and the bending angle was set to 90°, and the sample was bent on the flat plate. The plate thickness profile of the curved corner portion (maximum curvature portion) was measured by a scanning electron microscope at a magnification of 3000 times in the area of the plate thickness of 1/8 to 3/8 and 5/8 to 7/8. When the number of cracks is less than 20 per 1 mm 2 , it can be judged that crack formation due to interfacial peeling during cold working is suppressed, and cold workability is evaluated as "good". Further, when the number of cracks exceeds 20, the cold workability is evaluated as "poor". However, the cracks are classified according to various types (cracks at the starting point of the Schönming carbon iron, cracks in the starting point of the sulfide, and cracks in the grains). In order to distinguish the crack of the starting point of the Schönming carbon iron from the crack of the sulfide starting point, an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope was used. Further, the average carbide diameter and the spheroidization ratio of the carbide were measured by the above method.

表1Table 1

表2Table 2

表3table 3

表4Table 4

表5table 5

表6Table 6

表7Table 7

在表3、4、6及7中之鋼板No.A-2~D-2、F-2、J-2、A-3、C-3、E-3、G-3~J-3、B-5、C-5、E-5、F-5、H-5、I-5、E-6及G-6~I-6，平均碳化物徑長及碳化物之球化率有經過適當控制，且冷加工性及高頻淬火硬化能(淬火硬度)相當良好。Steel sheets No. A-2 to D-2, F-2, J-2, A-3, C-3, E-3, G-3 to J-3 in Tables 3, 4, 6 and 7. B-5, C-5, E-5, F-5, H-5, I-5, E-6 and G-6~I-6, the average carbide diameter and the spheroidization rate of carbide have passed Properly controlled, and cold workability and high frequency quench hardening energy (quenching hardness) are quite good.

另一方面，在表2中之鋼板No.A-1~AB-1，由於退火時間太短且碳化物之球化小於70%，因此冷加工性不夠充分。又，在表5中之鋼板No.A-4~AB-4，碳化物之球化率超過90%，且高頻淬火硬化能不夠充分。在表4中之鋼板No.D-3、F-3，由於第一平均冷卻速度超過50℃/秒，因而從熱軋鋼板中之變韌鐵生成90%以上之球化率之碳化物，且高頻淬火硬化能不夠充分。此外，在表6及表7中之鋼板No.A-5及B-6，由於第一平均冷卻速度小於20℃/秒，因此平均碳化物徑長超過0.6μm且高頻淬火硬化能不夠充分。在表5及表7中之鋼板No.H-4及A-6，由於第一冷卻結束溫度超過700℃，因而產生因標度所造成之缺陷。在表3及表6中之鋼板No.H-2及G-5，由於第一冷卻結束溫度超過700℃，因此平均碳化物徑長與球化率無法滿足上述(2)式且冷加工性不夠充分。在表3及表7中之鋼板No.G-2及D-6，由於第一冷卻結束溫度低於500℃，因此平均碳化物徑長超過0.6μm且高頻淬火硬化能不夠充分。此時，於熱軋後存有許多賦予加工應變之沃斯田鐵，並且在冷卻時從該等沃斯田鐵已優先生成粗大的波來鐵。在表4及表7中之鋼板No.B-3及F-6，由於第二平均冷卻速度超過30℃/秒，因而生成90%以上之球化率之碳化物且高頻淬火硬化能不夠充分。在表6中之鋼板No.D-5、J-5，由於第二平均冷卻速度小於5℃/秒，因此平均碳化物徑長超過0.6μm且高頻淬火硬化能不夠充分。在表3中之鋼板No.E-2、I-2，由於第二冷卻結束溫度高於較第一冷卻結束溫度低50℃的溫度，因此碳化物之球化小於70%且冷加工性不夠充分。在表7中之鋼板No.C-6，由於第二冷卻結束溫度高於較第一冷卻結束溫度低50℃的溫度，因此平均碳化物徑長與球化率無法滿足上述(2)式且冷加工性不夠充分。在表7中之鋼板No.J-6，由於第二冷卻結束溫度低於400℃，因而生成90%以上之球化率之碳化物且高頻淬火硬化能不夠充分。On the other hand, in the steel sheets No. A-1 to AB-1 in Table 2, since the annealing time was too short and the spheroidization of the carbide was less than 70%, the cold workability was insufficient. Further, in the steel sheets No. A-4 to AB-4 in Table 5, the spheroidization ratio of the carbide was more than 90%, and the induction hardening hardening was insufficient. In the steel sheets No. D-3 and F-3 in Table 4, since the first average cooling rate exceeds 50 ° C / sec, a carbide having a spheroidization ratio of 90% or more is produced from the toughened iron in the hot-rolled steel sheet, And the high frequency quench hardening can not be sufficient. Further, in the steel sheets No. A-5 and B-6 in Tables 6 and 7, since the first average cooling rate is less than 20 ° C / sec, the average carbide diameter is longer than 0.6 μm and the induction hardening hardening is insufficient. . In the steel sheets No. H-4 and A-6 in Tables 5 and 7, since the first cooling end temperature exceeded 700 ° C, defects due to the scale occurred. In the steel sheets No. H-2 and G-5 in Tables 3 and 6, since the first cooling end temperature exceeds 700 ° C, the average carbide diameter and spheroidization rate cannot satisfy the above formula (2) and the cold workability is insufficient. full. In the steel sheets No. G-2 and D-6 in Tables 3 and 7, since the first cooling end temperature was lower than 500 ° C, the average carbide diameter was longer than 0.6 μm and the induction hardening hardening was insufficient. At this time, there are many Worthite irons which impart processing strain after hot rolling, and coarse waved iron is preferentially generated from these Worthite irons upon cooling. In the steel sheets No. B-3 and F-6 in Tables 4 and 7, since the second average cooling rate exceeds 30 ° C / sec, carbides having a spheroidization ratio of 90% or more are generated and the induction hardening hardening is insufficient. full. In the steel sheets No. D-5 and J-5 in Table 6, since the second average cooling rate was less than 5 ° C / sec, the average carbide diameter was longer than 0.6 μm and the induction hardening hardening was insufficient. In the steel sheets No. E-2 and I-2 in Table 3, since the second cooling end temperature is higher than the temperature lower than the first cooling end temperature by 50 ° C, the spheroidization of the carbide is less than 70% and the cold workability is insufficient. . In the steel sheet No. C-6 in Table 7, since the second cooling end temperature is higher than the temperature lower than the first cooling end temperature by 50 ° C, the average carbide diameter and the spheroidization rate cannot satisfy the above formula (2). Cold workability is not sufficient. In the steel sheet No. J-6 in Table 7, since the second cooling end temperature was lower than 400 ° C, carbides having a spheroidization ratio of 90% or more were produced and the induction hardening hardening was insufficient.

在表3、4、6及7中之鋼板No.K-2、K-3、K-5及K-6，由於Mo量超過0.5質量%，因此高頻加熱時碳化物無法充分熔解且高頻淬火硬化能不夠充分。在鋼板No.L-2、L-3、L-5及L-6，由於Mn量小於0.3質量%，因此鋼之淬火度降低且高頻淬火硬化能不夠充分。在鋼板No.M-2、Q-2、M-3、Q-3、M-5、Q-5、M-6及Q-6，由於Si量小於0.06%，因而產生上述之界面剝離且冷加工性不夠充分。在鋼板No.N-2、Y-2、N-3、Y-3、N-5、Y-5、N-6及Y-6，由於C量小於0.3%，因此鋼之淬火度降低且高頻淬火硬化能不夠充分。在鋼板No.O-2、P-2、O-3、P-3、O-5、P-5、O-6及P-6，由於Mn量超過2.0%，因此高頻淬火硬化能不夠充分。在鋼板No.R-2、AA-2、R-3、AA-3、R-5、AA-5、R-6及AA-6，由於Cr量超過0.10%，因此高頻加熱時碳化物無法充分熔解且高頻淬火硬化能不夠充分。在鋼板No.U-2、W-2、U-3、W-3、U-5、W-5、U-6及W-6，由於C量超過0.6%，因此冷加工性降低。在鋼板No.V-2、X-2、V-3、X-3、V-5、X-5、V-6及X-6，由於S量超過0.0075%，因此冷加工性不夠充分。在鋼板No.Z-2、Z-3、Z-5及Z-6，由於Si量超過0.30%且P量超過0.03%，因此冷加工性不夠充分。在鋼板No.AB-2、AB-3、AB-5及AB-6，由於V量超過0.5%，因此高頻淬火硬化能不夠充分。In the steel sheets No. K-2, K-3, K-5, and K-6 in Tables 3, 4, 6, and 7, since the amount of Mo exceeds 0.5% by mass, the carbide cannot be sufficiently melted and high at the time of high-frequency heating. Frequency quenching and hardening can not be sufficient. In the steel sheets No. L-2, L-3, L-5, and L-6, since the amount of Mn is less than 0.3% by mass, the quenching degree of steel is lowered and the induction hardening hardening is insufficient. In the steel sheets No. M-2, Q-2, M-3, Q-3, M-5, Q-5, M-6, and Q-6, since the amount of Si is less than 0.06%, the above-described interfacial peeling occurs. Cold workability is not sufficient. In the steel sheets No. N-2, Y-2, N-3, Y-3, N-5, Y-5, N-6 and Y-6, since the amount of C is less than 0.3%, the quenching degree of steel is lowered and Induction hardening can not be sufficient. In the steel sheets No.O-2, P-2, O-3, P-3, O-5, P-5, O-6 and P-6, since the amount of Mn exceeds 2.0%, the induction hardening is insufficient. full. In the steel sheets No. R-2, AA-2, R-3, AA-3, R-5, AA-5, R-6 and AA-6, since the amount of Cr exceeds 0.10%, carbides are heated at high frequency. Insufficient melting and high-frequency quenching and hardening are not sufficient. In the steel sheets No. U-2, W-2, U-3, W-3, U-5, W-5, U-6, and W-6, since the amount of C exceeds 0.6%, the cold workability is lowered. In the steel sheets No. V-2, X-2, V-3, X-3, V-5, X-5, V-6, and X-6, since the amount of S exceeds 0.0075%, the cold workability is insufficient. In the steel sheets No. Z-2, Z-3, Z-5, and Z-6, since the amount of Si exceeds 0.30% and the amount of P exceeds 0.03%, the cold workability is insufficient. In the steel sheets No. AB-2, AB-3, AB-5, and AB-6, since the amount of V exceeds 0.5%, the induction hardening can be insufficient.

此外，以實施例較具體說明可適當使用於冷加工之表面處理皮膜(具有表面皮膜之冷加工用中碳鋼板)。Further, a surface treatment film (a medium carbon steel sheet for cold working having a surface film) which can be suitably used for cold working can be suitably used as an embodiment.

(表面處理液之調製)(modulation of surface treatment liquid)

首先，調製含有下述表8中顯示之成分之表面處理液(藥劑)a~q。而，表8中，使用硝酸鋅與磷酸之組合作為無機酸鹽之理由在於：磷酸鋅極難溶於水但溶解於酸之故。如此一來，藉由組合可溶於水之硝酸鋅與磷酸，可生成難溶於水之磷酸鋅，使其存於表面處理液中。First, surface treatment liquids (agents) a to q containing the components shown in Table 8 below were prepared. On the other hand, in Table 8, the reason why the combination of zinc nitrate and phosphoric acid is used as the inorganic acid salt is that zinc phosphate is extremely insoluble in water but dissolved in acid. In this way, by combining water-soluble zinc nitrate and phosphoric acid, zinc phosphate which is hardly soluble in water can be formed and stored in the surface treatment liquid.

(表面皮膜鋼板之製造)(Manufacture of surface film steel plate)

接下來，使用如上述方法所調製之表面處理液a~q，藉由以下方法製造出於板之兩面形成有傾斜型3層構造之表面處理皮膜的表面處理鋼板(No.1~29)(參考下述表10)。Next, using the surface treatment liquids a to q prepared by the above method, a surface-treated steel sheet (No. 1 to 29) having a surface treatment film having an inclined three-layer structure formed on both sides of the sheet was produced by the following method (No. 1 to 29) Refer to Table 10) below.

具體說明該等表面處理鋼板之製造方法。藉由一般的轉化爐-真空脫氣處理熔製表9中顯示之成分之鋼，以製作鋼片。此外，將該鑄片以1220℃保持1小時後，以軋延結束溫度870℃之條件進行熱軋而製得板厚8mm之熱軋鋼板。之後，將該熱軋鋼板以30℃/秒之平均冷卻速度冷卻至670℃後，再以15℃/秒冷卻至560℃後進行捲取。另外以20小時將捲取好的熱軋鋼板冷卻至400℃。將所製得之熱軋鋼板在氫氣95%環境下以700℃退火30hr之後再進行爐內冷卻。以塗裝#3棒(塗裝棒)將表面處理液a~q塗佈至經退火之熱軋鋼板(退火鋼板)上。並以表面處理液之濃度來控制表面處理皮膜之膜厚。此外，在300℃之熱風乾燥爐中，以到達板溫度為150℃之條件，將塗佈有表面處理液之退火鋼板予以乾燥。乾燥後進行空氣冷卻，製作出表面處理鋼板。The method of producing the surface-treated steel sheets will be specifically described. The steel of the composition shown in Table 9 was melted by a general reformer-vacuum degassing treatment to produce a steel sheet. Further, the cast piece was held at 1,220 ° C for 1 hour, and then hot rolled at a rolling end temperature of 870 ° C to obtain a hot-rolled steel sheet having a thickness of 8 mm. Thereafter, the hot-rolled steel sheet was cooled to 670 ° C at an average cooling rate of 30 ° C / sec, and then cooled to 560 ° C at 15 ° C / sec, and then wound up. Further, the coiled hot-rolled steel sheet was cooled to 400 ° C in 20 hours. The prepared hot-rolled steel sheet was annealed at 700 ° C for 30 hr in a hydrogen atmosphere at 95%, and then cooled in a furnace. The surface treatment liquids a to q were applied to the annealed hot-rolled steel sheets (annealed steel sheets) by coating #3 rods (coating rods). The film thickness of the surface treatment film is controlled by the concentration of the surface treatment liquid. Further, the annealed steel sheet coated with the surface treatment liquid was dried in a hot air drying oven at 300 ° C under conditions of a plate temperature of 150 ° C. After drying, air cooling was performed to prepare a surface-treated steel sheet.

而，從施加表面處理前之退火鋼板採取板厚8mm×板寬15mm×板長100mm之淬火試樣，在頻率78kHz以100℃/秒之平均加熱速度從室溫升溫至1000℃後，以1000℃保持10s，再立刻以200℃/秒以上之平均冷卻速度急速冷卻至室溫，以測定淬火材之維氏硬度(淬火硬度)。此外，以上述方法測定退火鋼板之平均碳化物徑長及碳化物之球化率。其結果確認：平均碳化物徑長為0.31μm，球化率為85.7%，且高頻淬火後之硬度為638.7HV。Further, a quenched sample having a thickness of 8 mm × a plate width of 15 mm × a plate length of 100 mm was taken from the annealed steel sheet before the surface treatment was applied, and the temperature was raised from room temperature to 1000 ° C at an average heating rate of 100 ° C / sec at a frequency of 78 kHz, and then 1000. After maintaining at ° C for 10 s, it was rapidly cooled to room temperature at an average cooling rate of 200 ° C /sec or more to measure the Vickers hardness (quenching hardness) of the quenched material. Further, the average carbide diameter of the annealed steel sheet and the spheroidization ratio of the carbide were measured by the above method. As a result, it was confirmed that the average carbide diameter was 0.31 μm, the spheroidization ratio was 85.7%, and the hardness after induction hardening was 638.7 HV.

(膜厚測定)(measurement of film thickness)

使用高頻波GDS對所製得之表面處理鋼板進行膜厚測定。詳細而言，係測定從表面處理皮膜之最表面起，到具有高頻波GDS之測定表中潤滑劑之代表元素(Mo、及C等)之峰值強度之最大值之1/2之峰值強度的膜厚方向之位置(深度)間之距離，來決定潤滑劑層層厚。又，測定從表面處理皮膜與鋼板之界面起，到高頻波GDS之測定表中具有起因於矽醇鍵結之成分之代表元素(Si)之峰值強度之最大值之1/2之峰值強度的膜厚方向之位置(深度)間之距離，來決定密接層層厚。此外，測定(計算)從具有潤滑劑之代表元素(Mo)之峰值強度之最大值之1/2之峰值強度的位置起，到具有起因於矽醇鍵結之成分之代表元素(Si)之峰值強度之最大值之1/2之峰值強度的位置間之距離，來決定基底層層厚。又，使用未重複之其他元素作為代表元素進行測定，以使潤滑劑層(潤滑劑成分)與基底層(無機酸鹽成分)之代表元素、及、基底層(無機酸鹽成分)與密接層(起因於矽醇鍵結之成分)之代表元素不同。The surface-treated steel sheet obtained was subjected to film thickness measurement using a high-frequency wave GDS. Specifically, a film having a peak intensity of 1/2 of the maximum value of the peak intensity of the representative elements (Mo, C, etc.) of the lubricant in the measurement table having the high-frequency wave GDS from the outermost surface of the surface-treated film is measured. The distance between the positions (depths) in the thick direction determines the thickness of the lubricant layer. Further, a film having a peak intensity of 1/2 of the maximum value of the peak intensity of the representative element (Si) of the component of the sterol bond is measured in the measurement table of the high-frequency wave GDS from the interface between the surface-treated film and the steel sheet. The distance between the positions (depths) in the thick direction determines the thickness of the adhesion layer. Further, it is measured (calculated) from a position having a peak intensity of 1/2 of the maximum value of the peak intensity of the representative element (Mo) of the lubricant to a representative element (Si) having a component derived from sterol bonding. The base layer thickness is determined by the distance between the positions of the peak intensities of 1/2 of the maximum value of the peak intensity. Further, the other elements which are not repeated are used as representative elements to measure the lubricant layer (lubricant component) and the base layer (mineral acid salt component), and the base layer (mineral acid salt component) and the adhesion layer. The representative elements (contributing to the components of the sterol bond) are different.

例如，使用石墨作為潤滑劑時，以無機酸鹽之代表元素(P、Si、Mo、W)之峰值強度求算潤滑劑層及基底層層厚。For example, when graphite is used as the lubricant, the thickness of the lubricant layer and the underlayer layer is determined by the peak intensity of the representative elements (P, Si, Mo, W) of the inorganic acid salt.

(評估方法及評估基準)(assessment method and evaluation criteria)

此外，藉由下述顯示之評估方法及評估基準，評估如上述所製造之表面處理鋼板之皮膜密接性及加工性。Further, the film adhesion and workability of the surface-treated steel sheet produced as described above were evaluated by the evaluation methods and evaluation criteria shown below.

<皮膜密接性評估><Evaluation of film adhesion>

以使用平珠模具之拉拔滑動試驗來評估皮膜密接性。在該拉拔滑動試驗中，以尺寸30×200mm從表面處理鋼板採取已除去緣邊之剪切毛邊的試驗片(試樣)使用。而，對試樣進行滑動試驗之前，以X射線螢光分析裝置測定皮膜中主要的構成元素之強度(試驗前強度)。The film adhesion was evaluated by a pull-slip test using a flat bead mold. In the pull-slip test, a test piece (sample) having a shear burr having a rim removed from the surface-treated steel sheet was used in a size of 30 × 200 mm. Before the slide test of the sample, the intensity of the main constituent elements in the film (pre-test strength) was measured by an X-ray fluorescence analyzer.

在平珠模具準備1組長40mm、寬60mm、且厚30mm材質為SKD11且表面經#1000之砂紙研磨過的模具。接下來，以上述模具夾起試樣，在氣壓缸以1000kg擠壓，並於拉力試驗機將試樣加以拉拔。對拉拔後之試樣以X射線螢光分析裝置與上述同樣地測定元素之強度(試驗後強度)，並以(試驗後強度/試驗前強度)×100[%]算出其剩餘比例。In the flat bead mold, a set of molds having a length of 40 mm, a width of 60 mm, and a thickness of 30 mm and having a material of SKD11 and having a surface of #1000 sandpaper was prepared. Next, the sample was taken up with the above mold, extruded at 1000 kg in a pneumatic cylinder, and the sample was drawn on a tensile tester. The strength of the element (strength after test) was measured in the X-ray fluorescence analyzer with the X-ray fluorescence analyzer in the same manner as above, and the remaining ratio was calculated as (post-test strength/pre-test strength) × 100 [%].

就皮膜密接性之評估基準而言，係將剩餘比例小於70%之情況評估為“差”，將剩餘比例在70%以上且小於90%之情況評估為“良”，並將剩餘比例在90%以上之情況評估為“優”。As far as the evaluation criteria of the film adhesion are concerned, the case where the remaining ratio is less than 70% is evaluated as "poor", and the case where the remaining ratio is 70% or more and less than 90% is evaluated as "good", and the remaining ratio is 90. The situation above % is evaluated as "excellent".

<加工性評估><Processability Evaluation>

以穿刺試驗評估加工性。在該穿刺試驗中，首先使從表面處理鋼板所製作之圓柱狀穿刺試驗片1A(第7B圖中顯示之加工前之穿刺試驗片1A)，載置於具有第7A圖中顯示之桿狀內面形狀之模座3上。之後，隔著第7A圖中顯示之平板2，對穿刺試驗片1A施加重負載，將穿刺試驗片1A壓入模座3內，以成型為第7B圖中顯示之加工後之穿刺試驗片1B之形狀。藉由此種方法，可形成依循模座形狀之穿刺物，以此時之穿刺高度(mm)評估潤滑性。因此，穿刺高度愈高潤滑性愈佳。而，穿刺試驗之條件係依據特開平5-7969號公報中所揭示之方法。The processability was evaluated by a puncture test. In the puncture test, the cylindrical puncture test piece 1A (the puncture test piece 1A before processing shown in Fig. 7B) produced from the surface-treated steel sheet is placed in the rod shape shown in Fig. 7A. The mold base 3 of the surface shape. Thereafter, a heavy load is applied to the puncture test piece 1A via the flat plate 2 shown in Fig. 7A, and the puncture test piece 1A is pressed into the mold base 3 to be molded into the processed puncture test piece 1B shown in Fig. 7B. The shape. By this method, a puncture that follows the shape of the mold base can be formed, and the lubricity can be evaluated at the puncture height (mm) at this time. Therefore, the higher the puncture height, the better the lubricity. On the other hand, the conditions of the puncture test are based on the method disclosed in Japanese Laid-Open Patent Publication No. Hei 5-7969.

有關加工性之評估基準，係以該穿刺高度進行評估，將穿刺高度小於12.5mm之情況評估為“差”，穿刺高度在12.5mm以上且在13.5mm以下之情況評估為“良”，並將穿刺高度超過13.5mm超之情況評估為“優”。而，“良”之評估相當於使習知之複合皮膜(化成反應/皂處理)形成在同樣的鋼板所製作之試樣的性能。The evaluation criteria for the processing property are evaluated by the height of the puncture, and the case where the puncture height is less than 12.5 mm is evaluated as "poor", and the puncture height is evaluated as "good" under the condition of 12.5 mm or more and below 13.5 mm, and The case where the puncture height exceeds 13.5 mm is evaluated as "excellent". On the other hand, the evaluation of "good" is equivalent to the performance of a conventionally produced composite film (chemical reaction/soap treatment) formed on the same steel sheet.

將如以上所進行之各層厚度之測定結果、及皮膜密接性及加工性之評估結果顯示於表10。The results of measurement of the thickness of each layer as described above, and the results of evaluation of film adhesion and workability are shown in Table 10.

如上述表10顯示，在No.1~19之表面處理鋼板中，皆具有良好的皮膜密接性及加工性。另一方面，在No.24及25之表面處理鋼板，由於密接層層厚未經最佳化，因此與No.1~19之表面處理鋼板相較之下，皮膜密接性較差。此外，在No.20~29之表面處理鋼板，由於各層之條件有其中一項未經最佳化，因此與No.1~19之表面處理鋼板相較之下，在加工性(潤滑性)都比較差。As shown in the above Table 10, the surface-treated steel sheets of Nos. 1 to 19 all have good film adhesion and workability. On the other hand, in the surface-treated steel sheets of Nos. 24 and 25, since the thickness of the adhesion layer was not optimized, the adhesion of the film was inferior to that of the surface-treated steel sheets of Nos. 1 to 19. In addition, in the surface treated steel sheets of No. 20 to 29, since one of the conditions of each layer is not optimized, the workability (lubricity) is compared with the surface treated steel sheets of Nos. 1 to 19. Both are poor.

產業上之可利用性Industrial availability

如前述，依據本發明可提供一種具良好的高頻淬火度之冷加工用中碳鋼板及其製造方法。因此，本發明在用以大幅擴大利用高頻淬火之中碳鋼板之用途上，可發揮重要的功能，且在鋼製品之製造產業中可利用性很高。As described above, according to the present invention, it is possible to provide a medium carbon steel sheet for cold working having a good induction hardening degree and a method for producing the same. Therefore, the present invention can exert an important function in the application for greatly expanding the use of the medium-frequency quenching medium carbon steel sheet, and is highly usable in the steel product manufacturing industry.

1．．．表面處理鋼板1. . . Surface treated steel

1A．．．加工前之穿刺試驗片1A. . . Puncture test piece before processing

1B．．．加工後之穿刺試驗片1B. . . Puncture test piece after processing

2．．．平板2. . . flat

3．．．模座3. . . Mold base

10．．．鋼板10. . . Steel plate

100．．．表面處理皮膜100. . . Surface treatment film

110．．．密接層110. . . Adhesive layer

120．．．基底層120. . . Base layer

130．．．潤滑劑層130. . . Lubricant layer

131．．．潤滑劑131. . . Lubricant

第1圖係顯示碳化物之平均徑長及碳化物之球化率波及淬火硬度及冷加工性之影響之圖。Fig. 1 is a graph showing the influence of the average diameter of carbides and the spheroidization rate of carbides on quenching hardness and cold workability.

第2圖係顯示Si量與冷加工後之碳化物界面及粒內龜裂數之關係圖。Fig. 2 is a graph showing the relationship between the amount of Si and the number of carbide interfaces and the number of cracks in the grains after cold working.

第3圖係顯示[Cr]+[Mo]/10與淬火硬度之關係圖。Fig. 3 is a graph showing the relationship between [Cr] + [Mo]/10 and quenching hardness.

第4圖係顯示碳化物之球化率與碳化物起點之龜裂數之關係圖。Figure 4 is a graph showing the relationship between the spheroidization rate of carbides and the number of cracks at the carbide starting point.

第5圖係顯示S量與硫化物起點之龜裂數之關係圖。Fig. 5 is a graph showing the relationship between the amount of S and the number of cracks at the starting point of the sulfide.

第6圖係顯示本發明之一實施形態之變形例之冷加工用鋼板構成之示意縱剖面圖。Fig. 6 is a schematic longitudinal cross-sectional view showing the structure of a steel sheet for cold working according to a modification of the embodiment of the present invention.

第7A圖係說明穿刺試驗方法之概略圖。Fig. 7A is a schematic view showing the puncture test method.

第7B圖係說明穿刺試驗片之加工前形狀與加工後形狀之概略圖。Fig. 7B is a schematic view showing the shape before processing and the shape after processing of the puncture test piece.

第8圖係顯示本發明之冷加工用中碳鋼板之製造方法之概略之流程圖。Fig. 8 is a flow chart showing the outline of a method for producing a medium carbon steel sheet for cold working according to the present invention.

Claims (11)

一種冷加工用中碳鋼板，其特徵在於：當進行以100℃/秒之平均加熱速度升溫後，於1000℃保持10秒，再以200℃/秒之平均冷卻速度急速冷卻至室溫之高頻淬火時，硬度成為500HV以上且在900HV以下者，且其以質量%計含有：C：0.30~0.60%、Si：0.06~0.30%、Mn：0.3~2.0%、P：0.030%以下、S：0.0075%以下、Al：0.005~0.10%、N：0.001~0.01%、及Cr：0.001~0.10%，剩餘部分係由Fe及無法避免之雜質所構成；且，碳化物之平均徑長d在0.6μm以下，碳化物之球化率p在70%以上且小於90%，前述碳化物之平均徑長dμm與前述碳化物之球化率p%滿足d≦0.04×p-2.6。A medium carbon steel sheet for cold working, characterized in that, when the temperature is raised at an average heating rate of 100 ° C / sec, the temperature is maintained at 1000 ° C for 10 seconds, and then rapidly cooled to room temperature at an average cooling rate of 200 ° C / sec. In the case of quenching, the hardness is 500 HV or more and 900 HV or less, and it is contained in mass %: C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.030% or less, S: 0.0075% or less, Al: 0.005 to 0.10%, N: 0.001 to 0.01%, and Cr: 0.001 to 0.10%, and the remainder is composed of Fe and unavoidable impurities; and the average diameter d of the carbide is 0.6. Below μm, the spheroidization ratio p of the carbide is 70% or more and less than 90%, and the average diameter dm of the carbide and the spheroidization ratio p% of the carbide satisfy d≦0.04×p-2.6. 如申請專利範圍第1項之冷加工用中碳鋼板，其係以質量%計，更含有：：Ni：0.01~0.5%、Cu：0.05~0.5%、Mo：0.01~0.5%、Nb：0.01~0.5%、Ti：0.001~0.05%、V：0.01~0.5%、Ta：0.01~0.5%、B：0.001~0.01%、W：0.01~0.5%、Sn：0.003~0.03%、Sb：0.003~0.03%、及As：0.003~0.03%之1種以上。For example, the medium carbon steel sheet for cold working in the first application of the patent scope is in mass %, and further includes: Ni: 0.01 to 0.5%, Cu: 0.05 to 0.5%, Mo: 0.01 to 0.5%, and Nb: 0.01 to 0.5%, Ti: 0.001~0.05%, V: 0.01~0.5%, Ta: 0.01~0.5%, B: 0.001~0.01%, W: 0.01~0.5%, Sn: 0.003~0.03%, Sb: 0.003~0.03 %, and As: one or more of 0.003 to 0.03%. 如申請專利範圍第2項之冷加工用中碳鋼板，其係Cr量[Cr]與Mo量[Mo]滿足[Cr]+[Mo]/10<0.10。For example, in the medium carbon steel sheet for cold working in the second application of the patent scope, the amount of Cr [Cr] and the amount of Mo [Mo] satisfy [Cr]+[Mo]/10<0.10. 如申請專利範圍第1或2項之冷加工用中碳鋼板，其係冷加工前之硬度在120HV以上且小於170HV。The medium carbon steel sheet for cold working according to the first or second aspect of the patent application has a hardness before cold working of 120 HV or more and less than 170 HV. 如申請專利範圍第1或2項之冷加工用中碳鋼板，其係於至少一面更具有表面處理皮膜，該表面處理皮膜則包含：起因於以含有金屬成分X之Si-O-X表示之矽醇鍵結之成分、耐熱樹脂、無機酸鹽及潤滑劑之各成分；該表面處理皮膜在膜厚方向具有前述各成分之濃度梯度，且在靠近前述表面處理皮膜與前述冷加工用中碳鋼板之界面，依序具有密接層、基底層及潤滑劑層等3層；前述密接層在前述3層中含有最多量之起因於前述矽醇鍵結之成分，並具有0.1nm以上且100nm以下之厚度；前述基底層在前述3層中含有最多量之前述耐熱樹脂及前述無機酸鹽，且相對於100質量份之前述耐熱樹脂，含有0.01質量份以上且10質量份以下之前述無機酸鹽，並具有0.1μm以上且15μm以下之厚度；前述潤滑劑層在前述3層中含有最多量之前述潤滑劑，並具有0.1μm以上且10μm以下之厚度；前述基底層之厚度相對於前述潤滑劑層之厚度的比值在0.2以上且在10以下。The medium carbon steel sheet for cold working according to claim 1 or 2, which has a surface treatment film on at least one side, the surface treatment film comprising: a sterol bond represented by Si-OX containing a metal component X a component of a knot, a heat-resistant resin, a mineral acid salt, and a lubricant; the surface-treated film has a concentration gradient of each of the components in a film thickness direction, and is close to an interface between the surface-treated film and the medium-carbon steel sheet for cold working. And having three layers of an adhesion layer, a base layer, and a lubricant layer; the adhesion layer contains a maximum amount of the sterol-bonded component in the three layers, and has a thickness of 0.1 nm or more and 100 nm or less; In the above-mentioned three layers, the base layer contains a maximum amount of the above-mentioned heat-resistant resin and the above-mentioned inorganic acid salt, and contains 0.01 parts by mass or more and 10 parts by mass or less of the above-mentioned inorganic acid salt with respect to 100 parts by mass of the above heat-resistant resin, and has 0.1. a thickness of not less than μm and not more than 15 μm; the lubricant layer containing the most amount of the lubricant in the three layers, and having a thickness of 0.1 μm or more and 10 μm or less; The thickness of the underlayer thickness ratio of the lubricant layer with respect to 0.2 or more and 10 or less. 如申請專利範圍第5項之冷加工用中碳鋼板，其中前述無機酸鹽係選自於由磷酸鹽、硼酸鹽、矽酸鹽、鉬酸鹽及鎢酸鹽所構成之群組中之至少1種化合物。The medium carbon steel sheet for cold working according to claim 5, wherein the inorganic acid salt is selected from the group consisting of phosphate, borate, silicate, molybdate and tungstate. Kind of compound. 如申請專利範圍第5項之冷加工用中碳鋼板，其中前述耐熱樹脂係選自於由聚醯亞胺樹脂、聚酯樹脂、環氧樹脂及氟樹脂所構成之群組中之至少1種樹脂。The medium carbon steel sheet for cold working according to claim 5, wherein the heat resistant resin is at least one selected from the group consisting of a polyimide resin, a polyester resin, an epoxy resin, and a fluororesin. . 如申請專利範圍第5項之冷加工用中碳鋼板，其中前述潤滑劑係選自於由聚四氟乙烯、二硫化鉬、二硫化鎢、氧化鋅及石墨所構成之群組中之至少1種化合物。The medium carbon steel sheet for cold working according to claim 5, wherein the lubricant is at least one selected from the group consisting of polytetrafluoroethylene, molybdenum disulfide, tungsten disulfide, zinc oxide, and graphite. Compound. 一種冷加工用中碳鋼板之製造方法，其特徵在於包含以下步驟：第1步驟，係將具有如申請專利範圍第1或2項之成分組成之鑄片，保持在1050℃以上且1300℃以下者；第2步驟，係在該第1步驟後，對前述鑄片進行在750℃以上且1000℃以下結束軋延之熱軋，而獲得鋼板者；第3步驟，係在該第2步驟後，以20℃/秒以上且50℃/秒以下之第一平均冷卻速度，將前述鋼板冷卻至500℃以上且700℃以下之第一冷卻結束溫度者；第4步驟，係在該第3步驟後，以5℃/秒以上且30℃/秒以下之第二平均冷卻速度，將前述鋼板冷卻至400℃以上且較前述第一冷卻結束溫度低50℃之溫度以下之第二冷卻結束溫度，而進行捲取者；第5步驟，係在該第4步驟後，以使在400℃以上且前述第二冷卻結束溫度以下之時間限制在30小時以下的方式，保持前述鋼板者；及第6步驟，係在該第5步驟後，將前述鋼板加熱至600℃以上且Ac1 點-10℃以下，並保持5小時以上且小於100小時，而進行退火。A method for producing a medium carbon steel sheet for cold working, comprising the steps of: the first step of maintaining a cast piece having a composition of the first or second aspect of the patent application at 1050 ° C or higher and 1300 ° C or lower; In the second step, after the first step, the slab is subjected to hot rolling at 750 ° C or higher and 1000 ° C or lower to obtain a steel sheet, and the third step is after the second step. Cooling the steel sheet to a first cooling end temperature of 500 ° C or higher and 700 ° C or lower at a first average cooling rate of 20 ° C /sec or more and 50 ° C / sec or less; the fourth step is after the third step And cooling the steel sheet to a second cooling end temperature of 400 ° C or more and a temperature lower than the first cooling end temperature by 50 ° C or less at a second average cooling rate of 5 ° C / sec or more and 30 ° C / sec or less. The fifth step is to maintain the steel sheet at a temperature of 400 ° C or higher and the second cooling end temperature or lower for 30 hours or less after the fourth step; and the sixth step After the fifth step, the aforementioned The steel sheet is heated to 600 ° C or more and A c1 point - 10 ° C or less, and is kept for 5 hours or more and less than 100 hours, and is annealed. 如申請專利範圍第9項之冷加工用中碳鋼板之製造方法，其中在前述第6步驟中，在400℃以下之露點低於-20℃，在超過400℃之露點低於-40℃，且氫濃度在95%以上。The method for producing a medium carbon steel sheet for cold working according to claim 9, wherein in the sixth step, the dew point below 400 ° C is lower than -20 ° C, and the dew point exceeding 400 ° C is lower than -40 ° C, and The hydrogen concentration is above 95%. 如申請專利範圍第9或10項之冷加工用中碳鋼板之製造方法，其係在前述第6步驟之後，將包含水溶性矽烷耦合劑、水溶性無機酸鹽、水溶性耐熱樹脂及潤滑劑之水系表面處理液塗佈到前述冷加工用中碳鋼板之至少一面，並使前述表面處理液乾燥，而在前述冷加工用中碳鋼板之至少一面形成前述表面處理皮膜。The method for producing a medium carbon steel sheet for cold working according to claim 9 or 10, which comprises a water-soluble decane coupling agent, a water-soluble inorganic acid salt, a water-soluble heat-resistant resin, and a lubricant after the sixth step. The aqueous surface treatment liquid is applied to at least one surface of the medium carbon steel sheet for cold working, and the surface treatment liquid is dried, and the surface treatment film is formed on at least one surface of the medium carbon steel sheet for cold working.
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