TWI847039B - Method for manufacturing burring steel - Google Patents
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- 239000011572 manganese Substances 0.000 claims abstract description 20
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 19
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
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- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 abstract 2
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Abstract
Description
本發明是有關於一種擴孔型鋼材與其製造方法。 The present invention relates to an expanded steel material and a manufacturing method thereof.
針對抗拉強度需求在780百萬帕(MPa)以上的熱軋鋼材，一般大多採取多重強化機制才能滿足需求。例如，除了原有的鐵(Fe)晶格強度以及基本的合金固溶強化、細晶強化外，還要額外再利用相變強化、析出強化等，才能達到780百萬帕的水準。 For hot-rolled steel with tensile strength requirements above 780 MPa, multiple strengthening mechanisms are generally used to meet the requirements. For example, in addition to the original iron (Fe) lattice strength and basic alloy solid solution strengthening and fine grain strengthening, additional phase transformation strengthening and precipitation strengthening are also required to reach the 780 MPa level.
相變強化的作法係控制熱軋製程條件，使得最終熱軋鋼材的顯微組織，除了有強度較低的肥粒鐵基地外，亦存有高強的第二相，如此可提升鋼材整體強度。有一些文獻提及，可調整熱軋盤捲溫度，以控制高強第二相呈現為麻田散鐵、波來鐵或變軔鐵。若高強第二相為麻田散鐵或波來鐵，由於其硬度與肥粒鐵基地之間的差異較大，因此加工應用時肥粒鐵/麻田散鐵或肥粒鐵/波來鐵之間的變形協調能力較差，將促使兩相之間的界面處形成微裂縫，最終劣化擴孔率。若高強第二相為變軔鐵，由於其硬度與肥粒鐵基地間的差異較小，因此彼此間的變形協調能力較佳， 將使得擴孔率較佳。因此，在高強度熱軋擴孔鋼材的顯微組織設計上，多以肥粒鐵加變軔鐵為主，另有部分不可避免的雪明碳鐵存在。 Phase transformation strengthening is achieved by controlling the hot rolling process conditions so that the final microstructure of the hot rolled steel has a high-strength second phase in addition to the low-strength ferrous iron base, thereby improving the overall strength of the steel. Some literature mentions that the hot rolling coiling temperature can be adjusted to control the high-strength second phase to appear as ferrous iron, ferrous iron or ferrous iron. If the high-strength second phase is ferrous iron or ferrous iron, due to the large difference in hardness between it and the ferrous iron base, the deformation coordination ability between ferrous iron/ferrous iron or ferrous iron/ferrous iron is poor during processing and application, which will cause microcracks to form at the interface between the two phases, ultimately deteriorating the porosity. If the high-strength second phase is metamorphic iron, the difference between its hardness and the granular iron base is small, so the deformation coordination ability between them is better, which will make the porosity better. Therefore, in the microstructure design of high-strength hot-rolled expanded steel, granular iron plus metamorphic iron is mainly used, and some unavoidable snow-clear carbon iron exists.
提升變軔鐵硬化能的常見做法為提升錳(Mn)的含量，但錳容易在組織中的局部位置聚集形成偏析，而錳與碳(C)的親和力良好，將促使碳原子擴散至錳偏析處。碳原子聚集後容易生成帶狀波來鐵，將不利於擴孔性。此外，錳的添加亦提升麻田散鐵硬化能，因此錳偏析處常生成麻田散鐵，對擴孔率不利。錳含量過高亦促進硫化錳(MnS)介在物生成，經熱軋後硫化錳將呈長條狀，而長條狀的兩端容易成為應力集中位置，形成微裂縫的風險大增，此外微裂縫若形成則容易沿著長條狀硫化錳的界面快速拓展，擴孔性將嚴重劣化。 The common method to improve the hardening energy of metamorphic iron is to increase the content of manganese (Mn), but manganese tends to gather in local locations in the structure to form segregation. Manganese has a good affinity with carbon (C), which will promote the diffusion of carbon atoms to the manganese segregation. After carbon atoms gather, they tend to generate banded wave iron, which will be detrimental to the porosity. In addition, the addition of manganese also increases the hardening energy of the ferrite, so the ferrite is often generated at the manganese segregation, which is detrimental to the porosity. Excessive manganese content also promotes the formation of manganese sulfide (MnS) intermediaries. After hot rolling, manganese sulfide will be in the shape of long strips, and the two ends of the long strips are likely to become stress concentration locations, greatly increasing the risk of forming microcracks. In addition, if microcracks are formed, they are likely to expand rapidly along the interface of the long strip manganese sulfide, and the porosity will be seriously deteriorated.
本發明之實施例提出一種擴孔型鋼材與其製造方法，其係提高鉻(Cr)含量來取代提高錳含量，以減少有危害的帶狀波來鐵與麻田散鐵。另外，提高鉻含量不僅可提高強度，更可使部分長條狀的雪明碳鐵轉變為(或趨近)圓形顆粒狀。非長條狀的雪明碳鐵對於擴孔性的危害將降低。 The embodiment of the present invention proposes a porous steel and a manufacturing method thereof, which increases the chromium (Cr) content instead of increasing the manganese content to reduce harmful band wave iron and mata scattered iron. In addition, increasing the chromium content can not only increase the strength, but also make some long strips of snow-white carbon iron transform into (or approach) round particles. The harm of non-long strips of snow-white carbon iron to the porosity will be reduced.
根據本發明之一實施例，上述擴孔型鋼材為100重量百分比(wt%)計，此擴孔型鋼材包含：0.03重量百分比至0.12重量百分比的碳；1.0重量百分比以下的矽；1.0 重量百分比至2.0重量百分比的錳；0.03重量百分比以下的磷；0.01重量百分比以下的硫；0.01重量百分比至0.1重量百分比的鈮；0.04重量百分比至0.2重量百分比的鈦；0.04重量百分比至0.15重量百分比的釩；0.2重量百分比以上的鉻；0.02重量百分比至0.08重量百分比的鋁；平衡量的鐵；以及不顯著之雜質。其中，擴孔型鋼材之顯微組織包含雪明碳鐵，且雪明碳鐵的長軸/短軸比率為10以下。 According to one embodiment of the present invention, the expanded steel material comprises, based on 100 weight percent (wt%), 0.03 to 0.12 weight percent carbon; 1.0 weight percent or less silicon; 1.0 to 2.0 weight percent manganese; 0.03 weight percent or less phosphorus; 0.01 weight percent or less sulfur; 0.01 to 0.1 weight percent niobium; 0.04 to 0.2 weight percent titanium; 0.04 to 0.15 weight percent vanadium; 0.2 weight percent or more chromium; 0.02 to 0.08 weight percent aluminum; a balance of iron; and insignificant impurities. Among them, the microstructure of the expanded steel includes ferrocarbon, and the major axis/minor axis ratio of ferrocarbon is less than 10.
在一些實施例中，擴孔型鋼材之抗拉強度為797百萬帕(Mpa)以上。 In some embodiments, the tensile strength of the expanded steel is above 797 megapascals (MPa).
在一些實施例中，擴孔型鋼材之顯微組織更包含肥粒鐵以及變韌鐵。 In some embodiments, the microstructure of the expanded steel further includes granular iron and ductile iron.
根據本發明之一實施例，上述擴孔型鋼材之製造方法包含：提供一鋼胚，以此鋼胚為100重量百分比(wt%)計，此鋼胚包含：0.03重量百分比至0.12重量百分比的碳；1.0重量百分比以下的矽；1.0重量百分比至2.0重量百分比的錳；0.03重量百分比以下的磷；0.01重量百分比以下的硫；0.01重量百分比至0.1重量百分比的鈮；0.04重量百分比至0.2重量百分比的鈦；0.04重量百分比至0.15重量百分比的釩；0.2重量百分比以上的鉻；0.02重量百分比至0.08重量百分比的鋁；平衡量的鐵；以及不顯著之雜質。對此鋼胚進行一熱軋製程，以獲得一熱軋鋼板，其中此熱軋製程包含：控制一完軋溫度在沃斯田鐵開始轉換成肥粒鐵的溫度以上。對熱軋鋼板進行一層 流冷卻處理。於層流冷卻處理後，對熱軋鋼板進行一盤捲處理，以獲得由一擴孔型鋼材所盤捲而成之一鋼捲，其中進行盤捲處理時包含控制盤捲溫度在肥粒鐵開始轉變成變韌鐵的相變溫度以下，其中擴孔型鋼材之顯微組織包含雪明碳鐵，且雪明碳鐵的長軸/短軸比率為10以下。 According to one embodiment of the present invention, the manufacturing method of the expanded steel material comprises: providing a steel billet, wherein the steel billet comprises, based on 100 weight percent (wt%), 0.03 weight percent to 0.12 weight percent carbon; 1.0 weight percent or less silicon; 1.0 weight percent to 2.0 weight percent manganese; 0.03 weight percent or less phosphorus; 0.01 weight percent or less sulfur; 0.01 weight percent to 0.1 weight percent niobium; 0.04 weight percent to 0.2 weight percent titanium; 0.04 weight percent to 0.15 weight percent vanadium; 0.2 weight percent or more chromium; 0.02 weight percent to 0.08 weight percent aluminum; a balance of iron; and insignificant impurities. The steel blank is subjected to a hot rolling process to obtain a hot rolled steel plate, wherein the hot rolling process includes: controlling a finishing temperature above the temperature at which austenitic iron begins to be converted into granulated iron. The hot rolled steel plate is subjected to a layer flow cooling treatment. After laminar cooling, the hot rolled steel plate is subjected to a coiling process to obtain a steel coil formed by coiling an expanded steel material, wherein the coiling process includes controlling the coiling temperature to be below the phase transition temperature at which granular iron begins to transform into ductile iron, wherein the microstructure of the expanded steel material includes ferrous carbon, and the major axis/minor axis ratio of the ferrous carbon is less than 10.
在一些實施例中，上述之層流冷卻處理包含複數個冷卻階段，這些冷卻階段包含一第一水冷階段，其中此第一水冷階段之冷卻速率為20℃/秒至80℃/秒。 In some embodiments, the laminar cooling process includes a plurality of cooling stages, which include a first water cooling stage, wherein the cooling rate of the first water cooling stage is 20°C/second to 80°C/second.
在一些實施例中，上述之冷卻階段更包含空冷階段，其中此空冷階段接續於第一水冷階段，且空冷階段之溫度為650℃至800℃。 In some embodiments, the cooling stage further includes an air cooling stage, wherein the air cooling stage is subsequent to the first water cooling stage, and the temperature of the air cooling stage is 650°C to 800°C.
在一些實施例中，上述之冷卻階段更包含一第二水冷階段，其中此第二水冷階段接續於空冷階段，且第二水冷階段之冷卻速率為50℃/秒至100℃/秒。 In some embodiments, the above cooling stage further includes a second water cooling stage, wherein the second water cooling stage is subsequent to the air cooling stage, and the cooling rate of the second water cooling stage is 50℃/sec to 100℃/sec.
在一些實施例中，前述之盤捲處理係接續於第二水冷階段。 In some embodiments, the aforementioned coiling process is followed by a second water cooling stage.
在一些實施例中，前述之擴孔型鋼材之抗拉強度為797百萬帕以上。 In some embodiments, the tensile strength of the aforementioned expanded steel is above 797 MPa.
為讓本發明的上述特徵和優點能更明顯易懂，下文特舉實施例，並配合所附圖式作詳細說明如下。 In order to make the above features and advantages of the present invention more clearly understood, the following is a detailed description of the embodiments with the accompanying drawings.
100:擴孔型鋼材之製造方法 100: Manufacturing method of expanded hole steel
110~140:步驟 110~140: Steps
132~136:冷卻階段 132~136: Cooling down phase
圖1係繪示根據本發明一實施例之擴孔型鋼材之製造方法 的流程示意圖。 FIG1 is a schematic diagram showing a process of manufacturing a method for expanded steel according to an embodiment of the present invention.
本發明之實施例之擴孔型鋼材具有高擴孔性，可應用於各式高擴孔性需求的產品上，例如汽車之底盤、懸架臂、橫樑、與車輪等汽車用鋼。此擴孔型鋼材的合金架構可例如以低(碳、錳)-(極低磷、硫)-(鈦、釩、鉻)為主。在本發明之一些實施例中，擴孔型鋼材可包含碳、矽(Si)、錳、磷(P)、硫(S)、鈮、鈦、釩、鉻、鋁(Al)、平衡量的鐵、以及不顯著之雜質。 The expanded steel of the embodiments of the present invention has high porosity and can be applied to various products requiring high porosity, such as automobile chassis, suspension arms, crossbeams, and wheels. The alloy structure of the expanded steel can be, for example, based on low (carbon, manganese)-(extremely low phosphorus, sulfur)-(titanium, vanadium, chromium). In some embodiments of the present invention, the expanded steel can include carbon, silicon (Si), manganese, phosphorus (P), sulfur (S), niobium, titanium, vanadium, chromium, aluminum (Al), a balanced amount of iron, and insignificant impurities.
碳屬於鋼鐵中的主要強化元素。除了碳原子易落在鐵原子晶間而達到格隙型固溶強化效果外，碳原子亦容易累積於高密度差排位置，而可阻礙差排移動，進而達到強化效果。然而，鋼胚中碳含量過高時易促使波來鐵等碳化物生成，而不利於鋼材之擴孔性。因此，本發明之實施例的合金設計主要並不透過碳來強化鋼材，而係使碳含量處於較低的水準，藉此來確保鋼材的擴孔性。 Carbon is the main strengthening element in steel. In addition to the fact that carbon atoms easily fall between the crystals of iron atoms to achieve interstitial solid solution strengthening effects, carbon atoms are also easily accumulated in high-density dislocation positions, which can hinder the movement of dislocations and thus achieve a strengthening effect. However, when the carbon content in the steel embryo is too high, it is easy to promote the formation of carbides such as beryl, which is not conducive to the porosity of the steel. Therefore, the alloy design of the embodiment of the present invention does not mainly strengthen the steel through carbon, but keeps the carbon content at a relatively low level to ensure the porosity of the steel.
錳的添加除了可增加鋼材中變韌鐵的體積分率外，亦可提升變韌鐵本身的強度，因此可提升變韌鐵的硬化能。然而，錳的添加會促使硫化錳介在物生成，而不利於鋼材的擴孔性。此外，錳亦容易產生偏析，且與碳的親和力良好，因而易使碳原子擴散至錳偏析的位置，而於錳偏析位置處生成帶狀波來鐵，也是不利於鋼材的擴孔性。因此，本發明之實施例的合金設計主要並不透過錳來提升變韌鐵 的硬化能，而係使錳含量於較低的水準，藉此來確保鋼材的擴孔性。 In addition to increasing the volume fraction of varistors in steel, the addition of manganese can also improve the strength of varistors themselves, thereby improving the hardening performance of varistors. However, the addition of manganese will promote the formation of manganese sulfide intermediaries, which is not conducive to the porosity of steel. In addition, manganese is also prone to segregation and has a good affinity with carbon, so it is easy for carbon atoms to diffuse to the location of manganese segregation, and the formation of banded wavy iron at the location of manganese segregation is also not conducive to the porosity of steel. Therefore, the alloy design of the embodiment of the present invention does not mainly improve the hardening performance of varistors through manganese, but keeps the manganese content at a lower level to ensure the porosity of steel.
磷的添加雖然對肥粒鐵有固溶強化的效果，但由於磷易偏析於先前沃斯田鐵晶界，而弱化晶界強度，進而使得最終鋼材產品的加工性劣化。因此，本發明之實施例的合金設計係降低磷的含量。 Although the addition of phosphorus has a solid solution strengthening effect on ferrous iron, phosphorus is easily segregated at the grain boundaries of the previous austenite, which weakens the grain boundary strength and thus deteriorates the workability of the final steel product. Therefore, the alloy design of the embodiment of the present invention is to reduce the phosphorus content.
硫也易偏析於先前沃斯田鐵晶界而弱化晶界強度，更會促進硫化錳的生成，不利於鋼材的擴孔性。因此，本發明之實施例的合金設計係降低硫的含量。 Sulfur is also easy to segregate at the grain boundaries of the previous austenite and weaken the grain boundary strength, and will promote the formation of manganese sulfide, which is not conducive to the porosity of steel. Therefore, the alloy design of the embodiment of the present invention is to reduce the sulfur content.
矽的添加具有良好固溶強化效果，並可干擾碳原子擴散以抑制波來鐵等碳化物生成，將有利於擴孔性。然而，矽含量過高則容易在熱軋鋼板表面形成紅色氧化物，即所謂“紅銹”之表面缺陷。因此，本發明之實施例的合金設計將矽含量控制在一定範圍內。 The addition of silicon has a good solid solution strengthening effect and can interfere with the diffusion of carbon atoms to inhibit the formation of carbides such as ferrite, which will be beneficial to the porosity. However, if the silicon content is too high, red oxides, the so-called "red rust" surface defects, will easily form on the surface of the hot-rolled steel plate. Therefore, the alloy design of the embodiment of the present invention controls the silicon content within a certain range.
鈦的添加容易與碳、氮原子反應，於一定的高溫範圍內析出尺寸為奈米等級之碳化物或氮化物或碳氮化物，而該奈米析出物可有效抑制差排移動，進而發揮強化效果，因此本發明之實施例將以添加鈦做為強化機制之一。 The addition of titanium easily reacts with carbon and nitrogen atoms, and precipitates carbides, nitrides or carbonitrides of nanometer size within a certain high temperature range. The nano-precipitates can effectively inhibit the displacement movement and thus exert a strengthening effect. Therefore, the embodiment of the present invention will use the addition of titanium as one of the strengthening mechanisms.
釩的添加亦容易與碳、氮原子反應，於一定的高溫範圍內析出尺寸為奈米等級之碳化物或氮化物或碳氮化物，進而發揮強化效果。然而，釩的價格高於鈦，因此仍以鈦作為主要合金添加。但若以鈦-釩複合添加所生成之一複合型鈦-釩奈米析出物，相較於一般鈦奈米析出物，在高溫下尺寸更不易粗化，抑制差排移動的效果將更佳，進而優化 析出強化效果，因此本發明之實施例將以鈦-釩複合添加做為強化機制之一。 The addition of vanadium is also easy to react with carbon and nitrogen atoms, and precipitate carbides, nitrides or carbonitrides with nanometer size within a certain high temperature range, thereby exerting a strengthening effect. However, the price of vanadium is higher than that of titanium, so titanium is still used as the main alloy addition. However, if a composite titanium-vanadium nano-precipitate generated by adding titanium-vanadium composite is less likely to coarsen at high temperature compared to ordinary titanium nano-precipitates, the effect of inhibiting dislocation movement will be better, thereby optimizing the precipitation strengthening effect. Therefore, the embodiment of the present invention will use titanium-vanadium composite addition as one of the strengthening mechanisms.
鈮的添加亦容易與碳、氮原子反應，於一定的高溫範圍內析出尺寸為奈米等級之碳化物或氮化物或碳氮化物，這樣的析出物可抑制先前沃斯田鐵再結晶，而使得先前沃斯田鐵在熱軋過程中被軋得扁平，如此在後續鋼板溫度下降後產生沃斯田鐵至肥粒鐵相變態時，肥粒鐵成長空間受限，尺寸因而細化，進而可達到細晶強化的效果。由於鈮的價格較高，本發明之實施例將鈮添加控制在一定範圍內。 The addition of niobium also easily reacts with carbon and nitrogen atoms, and precipitates carbides, nitrides or carbonitrides of nanometer size within a certain high temperature range. Such precipitates can inhibit the recrystallization of the previous austenite, and make the previous austenite flattened during the hot rolling process. In this way, when the temperature of the subsequent steel plate drops and the austenite to granular iron phase transformation occurs, the granular iron growth space is limited, and the size is thus refined, thereby achieving the effect of fine grain strengthening. Due to the high price of niobium, the embodiment of the present invention controls the addition of niobium within a certain range.
鉻的添加除了可增加鋼材中變韌鐵的體積分率外，亦可提升變韌鐵本身的強度，因此可提升變韌鐵的硬化能。此外，鉻可干擾碳原子的擴散，而可促使雪明碳鐵的形狀球化，並可縮小雪明碳鐵的尺寸。然而，變韌鐵內部累積大量差排，在進行拉伸試驗時將影響伸長率，因此本發明之實施例的將鉻添加控制在一定範圍內。 The addition of chromium can not only increase the volume fraction of varistrine in steel, but also improve the strength of varistrine itself, thus improving the hardening ability of varistrine. In addition, chromium can interfere with the diffusion of carbon atoms, which can promote the spheroidization of the shape of varistrine and reduce the size of varistrine. However, a large amount of dislocations accumulate inside varistrine, which will affect the elongation during the tensile test. Therefore, the embodiment of the present invention controls the addition of chromium within a certain range.
請參照圖1，其係繪示依照本發明實施例之擴孔型鋼材之製造方法100的流程圖。在一些實施例中，製造擴孔型鋼材時，可先進行步驟110，以利用例如熔煉與精煉技術來製備鋼胚，並提供所煉製的鋼胚來進行熱軋。在一些例子中，以擴孔型鋼材成分為100重量百分比(wt%)來計，擴孔型鋼材具有0.03重量百分比至0.12重量百分比的碳；1.0重量百分比以下的矽；1.0重量百分比至2.0重量百分比的錳；0.03重量百分比以下的磷；0.01重量
百分比以下的硫；0.01重量百分比至0.1重量百分比的鈮；0.04重量百分比至0.2重量百分比的鈦；0.04重量百分比至0.15重量百分比的釩；0.2重量百分比以上的鉻；0.02重量百分比至0.08重量百分比的鋁；平衡量的鐵；以及不顯著之雜質。在一些例子中，鉻含量為約0.2重量百分比。在另一些例子中，鉻含量為約0.3重量百分比。
Please refer to Fig. 1, which is a flow chart of a
接著，進行步驟120，以對鋼胚進行熱軋製程，而獲得熱軋鋼板。在一些例子中，對鋼胚進行熱軋製程時，可先對鋼胚進行加熱處理。加熱鋼胚時可例如將加熱溫度控制在約1150℃至約1300℃。鋼胚經加熱處理後，可利用熱軋設備熱軋鋼胚。在一些例子中，進行熱軋製程可將完軋溫度控制在沃斯田鐵開始轉換成肥粒鐵的溫度以上。舉例而言，熱軋製程的完軋溫度可為約800℃至約1000℃。
Next,
完成鋼胚的熱軋製程後，可進行步驟130，以對熱軋鋼板進行層流冷卻處理。在本實施例中，層流冷卻處理包含複數個冷卻階段132~136。冷卻階段132為第一水冷階段，其冷卻速率為約20℃/秒至約80℃/秒。例如，朝熱軋鋼板噴灑冷卻水的方式來以約20℃/秒至約80℃/秒的速率來冷卻熱軋鋼板。然後，在第一水冷階段後，接續進行冷卻階段134。冷卻階段134為空冷階段。空冷階段之鋼板表面溫度為約650℃至約800℃，時間為約2至10秒。例如，將熱軋鋼板置於鋼板表面溫度為約650℃至約800℃中約2至10秒，以冷卻熱軋鋼板。接著，在空
冷階段後，接續進行冷卻階段136。冷卻階段136為第二水冷階段，其冷卻速率為約50℃/秒至約100℃/秒。例如，朝熱軋鋼板噴灑冷卻水的方式來以約50℃/秒至約100℃/秒的速率來冷卻熱軋鋼板。
After the hot rolling process of the steel blank is completed,
然後，進行步驟140以對冷卻後之熱軋鋼板進行盤捲處理，而獲得由擴孔型鋼材所盤捲而成的鋼捲。在本實施例中，盤捲處理係接續於第二水冷階段。另外，當行盤捲處理時，可將盤捲溫度控制在肥粒鐵開始轉變成變韌鐵之相變溫度以下。舉例而言，盤捲溫度可為約350℃至約650℃。 Then, step 140 is performed to coil the cooled hot-rolled steel plate to obtain a steel coil formed by coiling the expanded pore steel. In this embodiment, the coiling process is continued after the second water cooling stage. In addition, when the coiling process is performed, the coiling temperature can be controlled below the phase transition temperature at which the granular iron begins to transform into the ductile iron. For example, the coiling temperature can be about 350°C to about 650°C.
藉由將熱軋製程的完軋溫度控制在沃斯田鐵至肥粒鐵相變溫度(一般又稱Ar3溫度)以上，且將盤捲溫度控制在肥粒鐵開始轉變成變韌鐵之相變溫度以下，可避免波來鐵的生成，亦可使擴孔型鋼材的顯微組織為以肥粒鐵和變韌鐵為主，其中此擴孔型鋼材中另有部分不可避免的雪明碳鐵存在。在一些實施例中，擴孔型鋼材中之變韌鐵主要係以變韌肥粒鐵(bainitic ferrite)或針狀肥粒鐵(acicular ferrite)的形式存在。 By controlling the hot rolling process finishing temperature above the austenitic ferrite to ferrite phase transition temperature (generally known as Ar3 temperature) and controlling the coiling temperature below the phase transition temperature at which ferrite begins to transform into tantalum, the formation of ferrite can be avoided, and the microstructure of the expanded steel can be made to be mainly ferrite and tantalum, wherein the expanded steel also has some inevitable ferrite. In some embodiments, the tantalum in the expanded steel mainly exists in the form of bainitic ferrite or acicular ferrite.
以下利用多個試驗例子，來更具體說明利用本發明實施例的技術內容與功效。這些擴孔型鋼材之試驗例子的鉻含量、雪明碳鐵的長軸/短軸比率、擴孔率、變韌鐵之體積分率、抗拉強度、降伏強度、與伸長率列示於下表1中。 The following uses a number of test examples to more specifically illustrate the technical content and efficacy of the embodiments of the present invention. The chromium content, long axis/short axis ratio of carbon steel, porosity, volume fraction of ductile iron, tensile strength, yield strength, and elongation of these test examples of expanded pore steel are listed in Table 1 below.
根據上表1之試驗結果可知，本案實施例1~12利用多階段的層冷冷卻製程輔以較高鉻含量的添加，可具有較高的抗拉強度。例如，以習知製程製作的比較例1~6，其抗拉強度在780百萬帕以下，而本案實施例1~12可具有796百萬帕以上的拉抗強度。再者，雪明碳鐵的長軸/短軸比率可達到10以下，以減少長條狀之雪明碳鐵。透過本案實施例所提出之製程，可減少有危害的帶狀波來鐵與麻田散鐵。另外，提高鉻含量不僅可提高強度，更可使部分長條狀的雪明碳鐵轉變為(或趨近)圓形顆粒狀。非長條狀的雪明碳鐵對於擴孔性的危害將降低。 According to the test results in Table 1 above, embodiments 1 to 12 of the present invention utilize a multi-stage cooling process supplemented by the addition of a higher chromium content to have a higher tensile strength. For example, the tensile strength of comparative examples 1 to 6 made by the known process is below 780 megapascals, while embodiments 1 to 12 of the present invention can have a tensile strength of more than 796 megapascals. Furthermore, the major axis/minor axis ratio of the ferrocarbon can be reduced to less than 10 to reduce the long strips of ferrocarbon. Through the process proposed in the embodiments of the present invention, harmful band wave iron and ferrocarbon can be reduced. In addition, increasing the chromium content can not only increase the strength, but also make some of the elongated ferrocarbons transform into (or approach) round particles. The harm of non-elongated ferrocarbons to porosity will be reduced.
雖然本發明已以實施例揭露如上，然其並非用以限定本發明，任何所屬技術領域中具有通常知識者，在不脫離本發明的精神和範圍內，當可作些許的更動與潤飾，故本發明的保護範圍當視後附的申請專利範圍所界定者為準。 Although the present invention has been disclosed as above by the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the attached patent application.
100:擴孔型鋼材之製造方法 100: Manufacturing method of expanded hole steel
110~140:步驟 110~140: Steps
132~136:冷卻階段 132~136: Cooling down phase
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