TWI510645B

TWI510645B - Ferritic stainless steel

Info

Publication number: TWI510645B
Application number: TW102108795A
Authority: TW
Inventors: Takashi Samukawa; Kunio Fukuda; Masataka Yoshino; Hiroki Ota; Hiroyuki Ogata
Original assignee: Jfe Steel Corp
Priority date: 2012-03-13
Filing date: 2013-03-13
Publication date: 2015-12-01
Also published as: ES2632781T3; TW201348463A; CN104169451A; EP2826878A4; CN104169451B; EP2826878B1; EP2826878A1; JP5376099B1; WO2013136736A1; US20150023832A1; KR20140127862A; JPWO2013136736A1

Description

肥粒鐵系不鏽鋼Fertilizer iron stainless steel

本發明係關於表面性狀、以及與沃斯田鐵系不鏽鋼(austenitic stainless steel)間之熔接部耐蝕性優異的肥粒鐵系不鏽鋼(ferritic stainless steel)。The present invention relates to ferrite stainless steel having excellent surface properties and corrosion resistance to a welded portion between austenitic stainless steel and austenitic stainless steel.

不鏽鋼之中，就利用其優異的耐蝕性而言，有廣泛使用沃斯田鐵系不鏽鋼的SUS304(18%Cr-8%Ni)(日本工業規格、JISG 4305)，但此鋼種含有大量的Ni，因而屬高價位。因此，作為具有相當於SUS304之優異耐蝕性的鋼種，而開發出專利文獻1所記載的不鏽鋼。Among the stainless steels, SUS304 (18%Cr-8%Ni) (Japanese Industrial Standard, JISG 4305), which is widely used in Worthite iron-based stainless steel, is used for its excellent corrosion resistance, but this steel grade contains a large amount of Ni. Therefore, it is a high price. Therefore, the stainless steel described in Patent Document 1 has been developed as a steel grade having excellent corrosion resistance equivalent to SUS304.

專利文獻1所揭示的肥粒鐵系不鏽鋼板，係成分組成依質量%計，含有：C：0.03%以下、Si：1.0%以下、Mn：0.5%以下、P：0.04%以下、S：0.02%以下、Al：0.1%以下、Cr：20.5%以上且22.5%以下、Cu：0.3%以上且0.8%以下、Ni：1.0%以下、Ti：4×(C%+N%)以上、0.35%以下、Nb：0.01%以下、N：0.03%以下、C+N：0.05%以下，且其餘係由Fe及不可避免的雜質構成。The ferrite-based iron-based stainless steel sheet disclosed in Patent Document 1 contains, by mass%, C: 0.03% or less, Si: 1.0% or less, Mn: 0.5% or less, P: 0.04% or less, and S: 0.02. % or less, Al: 0.1% or less, Cr: 20.5% or more and 22.5% or less, Cu: 0.3% or more and 0.8% or less, Ni: 1.0% or less, Ti: 4 × (C% + N%) or more, 0.35% Hereinafter, Nb: 0.01% or less, N: 0.03% or less, and C+N: 0.05% or less, and the balance is composed of Fe and unavoidable impurities.

再者，JIS-SUS444、JIS-SUS430J1L等肥粒鐵系不鏽鋼，相較於沃斯田鐵系不鏽鋼之下，亦是具有應力腐蝕龜裂敏感性(Stress Corrosion Cracking sensitivity)較小、未含有價格變動較大的Ni等特徵，廣泛使用為汽車的排氣系統構件之材料、以及水槽、建築材料。Furthermore, the ferrite-based stainless steel such as JIS-SUS444 and JIS-SUS430J1L has a lower Stress Corrosion Cracking sensitivity and no price than the Worth Iron-based stainless steel. Features such as Ni, which are highly variable, are widely used as materials for exhaust system components of automobiles, as well as sinks and building materials.

但是，因為一般肥粒鐵系不鏽鋼相較於沃斯田鐵系不鏽鋼之下，加工性(特別係延伸)較差，因而針對肥粒鐵系不鏽鋼無法成形的難加工性零件，便採用沃斯田鐵系不鏽鋼。因此，由沃斯田鐵系不鏽鋼與肥粒鐵系不鏽鋼組合形成一個構造物的情況頗多。於該情況下，各構件幾乎均係利用熔接進行結合，而熔接方法主要係使用TIG熔接(Tungsten Inert Gas welding，鎢極鈍氣熔接)，對熔接部(weld zone)亦要求與母材同樣良好的耐蝕性。However, because the general ferrite iron-based stainless steel is stainless compared to the Worthfield iron system. Under steel, the workability (especially extension) is poor, so the Worthfield iron-based stainless steel is used for the difficult-to-machine parts that cannot be formed by the ferrite-based stainless steel. Therefore, there are many cases in which a structure is formed by combining Worthfield iron-based stainless steel and fat-grained iron-based stainless steel. In this case, almost all of the members are joined by welding, and the welding method mainly uses TIG welding (Tungsten Inert Gas welding), and the weld zone is required to be as good as the base material. Corrosion resistance.

[先前技術文獻][Previous Technical Literature] [專利文獻][Patent Literature]

專利文獻1：日本專利特開2007-77496號公報Patent Document 1: Japanese Patent Laid-Open Publication No. 2007-77496

專利文獻2：日本專利特開平8-10823號公報Patent Document 2: Japanese Patent Laid-Open No. Hei 8-10823

專利文獻1所揭示的肥粒鐵系不鏽鋼係、同一鋼種的熔接部具有良好耐蝕性。但是當與SUS304等異種鋼進行TIG熔接時，會有發生熔接部的耐蝕性低於母材情況的問題。The ferrite-based stainless steel system disclosed in Patent Document 1 and the welded portion of the same steel type have good corrosion resistance. However, when TIG welding is performed with a dissimilar steel such as SUS304, there is a problem that the corrosion resistance of the welded portion is lower than that of the base material.

此現象係因為熔接時的熱經歷，導致鋼中的C、N與Cr鍵結而形成Cr碳化物(chromium carbides，例如Cr₂₃ C₆ 等)、或Cr氮化物(chromium nitrides，CrN₂ 等)並析出於晶界，造成在晶界附近出現Cr濃度低於母材的Cr缺乏層(chromium deplation layer)，而引發所謂的敏化(sensitization)，致使耐蝕性劣化的緣故。This phenomenon is caused by the thermal history of welding, which causes C, N and Cr in the steel to bond to form Cr carbides (such as Cr ₂₃ C _{6 ,} etc.) or Cr nitrides (CrN _{2 ,} etc.). The precipitation is caused by the grain boundary, causing a Cr depletion layer having a Cr concentration lower than that of the base material in the vicinity of the grain boundary, thereby causing so-called sensitization, which causes deterioration of corrosion resistance.

一般為防止因敏化造成熔接部出現耐蝕性劣化，便有採取降低鋼中的C、N，且添加適量Ti，使C、N成為Ti碳氮化物並固定，俾防止生成Cr碳化物、Cr氮化物的方法。藉由此種方法，專利文獻1所揭示的肥粒鐵系不鏽鋼板彼此間之TIG熔接部便呈良好耐蝕性。Generally, in order to prevent deterioration of the corrosion resistance of the welded portion due to sensitization, it is necessary to reduce C and N in the steel, and add an appropriate amount of Ti to make C and N become Ti carbonitrides and fix them, thereby preventing the formation of Cr carbides and Cr. Nitride method. By this method, the patent The TIG welded portion between the ferrite-rich iron-based stainless steel sheets disclosed in 1 shows good corrosion resistance.

但是，相對於該肥粒鐵系不鏽鋼板的C含有量係大約0.01%，SUS304等的C含有量較高係0.04~0.05%，因而通常在與SUS304等高度含有C之不鏽鋼的接合處，為能利用同樣的Ti添加而防止敏化，便必需將Ti添加量提高至大約1.0%。However, the C content of the ferrite-based iron-based stainless steel sheet is about 0.01%, and the C content of SUS304 or the like is 0.04 to 0.05%. Therefore, it is usually a joint of stainless steel having a height of C such as SUS304. It is necessary to increase the amount of Ti added to about 1.0% by using the same Ti addition to prevent sensitization.

但是，若在肥粒鐵系不鏽鋼添加Ti至大約1.0%，在凝固中，於溶鋼中的Ti與N產生反應，而形成TiN並析出。該TiN缺乏高溫下的延展性，會成為熱軋步驟中的瑕疵而導致表面性狀惡化。依此所產生的痕跡較深，即便經由熱軋板退火、酸洗、後續的冷軋、冷軋板退火、酸洗等仍不會消除，因而在未利用研磨機研削等對熱軋退火酸洗板的表面施行大量切削處理之前提下，會成為所謂「氮化鈦細脈」(stringer caused by titanium nitrides)的表面瑕疵，導致冷軋退火酸洗板的表面性狀明顯劣化。However, if Ti is added to the ferrite-based stainless steel to about 1.0%, in the solidification, Ti in the molten steel reacts with N to form TiN and precipitate. The TiN lacks ductility at high temperatures and becomes a flaw in the hot rolling step, resulting in deterioration of surface properties. According to this, the traces generated are deep, and even after hot-rolled sheet annealing, pickling, subsequent cold rolling, cold-rolled sheet annealing, pickling, etc., the hot-rolling annealing acid is not removed by grinding without using a grinder. When the surface of the washing plate is lifted before a large amount of cutting treatment, it becomes a surface flaw of the so-called "stringer caused by titanium nitrides", and the surface properties of the cold-rolled annealed pickled sheet are remarkably deteriorated.

再者，TIG熔接的情況，一般表、背面均利用惰性氣體遮蔽，並在熔接部盡可能不會形成所謂「回火色」(temper color)的薄氧化皮膜之條件下施行熔接，實際步驟中，該氣體遮蔽並非充足，會有因空氣中的氮混入，而助長前述敏化的問題。In addition, in the case of TIG welding, the general surface and the back surface are shielded by an inert gas, and the welding is performed under the condition that the welded portion does not form a thin oxide film of a temper color as much as possible. In the actual step, This gas shielding is not sufficient, and there is a problem that the above-mentioned sensitization is promoted by the incorporation of nitrogen in the air.

再者，大量添加高價位Ti，亦會有損及未使用高價位Ni的鋼種優點之問題。Furthermore, the high addition of high-priced Ti also impairs the advantages of steels that do not use high-priced Ni.

本發明係有鑑於該等實情而完成，目的在於提供：表面性狀優異，且不僅與肥粒鐵系不鏽鋼，就連與沃斯田鐵系不鏽鋼熔接時，熔接部的耐蝕性仍優異之肥粒鐵系不鏽鋼。The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a fertilizer which is excellent in surface properties and which is excellent in corrosion resistance of a welded portion even when welded to a ferrite-based iron-based stainless steel. Iron-based stainless steel.

本發明者等為達成上述問題，針對鋼之化學成分對母材部與熔接部的耐蝕性之影響、及鋼板的表面性狀(氮化鈦細脈瑕疵)進行細膩調查、檢討，而獲得以下之結果。In order to achieve the above problems, the inventors of the present invention have directed the chemical composition of steel to the base material. The effects of the corrosion resistance of the welded portion and the welded portion and the surface properties of the steel sheet (titanium nitride fine veins) were investigated and reviewed in detail, and the following results were obtained.

(1)若藉由將肥粒鐵相促進元素的濃度予以適當化，而將與沃斯田鐵系不鏽鋼間之熔接部的組織形成麻田散鐵相(martensite phase)，便可防止敏化。理由係麻田散鐵相的C、N固溶限較大之緣故。(1) The sensitization can be prevented by forming the martensite phase of the structure of the welded portion between the Worth and the iron-based stainless steel by appropriately adjusting the concentration of the ferrite-grain-promoting element. The reason is because the C and N solid solution limits of the Matian iron phase are large.

(2)若添加極微量的Nb，在較Ti氮化物析出的溫度更高溫下會析出Nb氮化物。在後續的冷卻過程中，該Nb氮化物會成為Ti碳氮化物的成核位置，而促進因Ti造成的敏化防止效果。(2) If a very small amount of Nb is added, Nb nitride is precipitated at a temperature higher than the temperature at which the Ti nitride is precipitated. During the subsequent cooling process, the Nb nitride becomes a nucleation site of the Ti carbonitride, and the sensitization preventing effect due to Ti is promoted.

(3)一般若有添加Nb，便會導致鋼板的再結晶溫度上昇，但若添加極微量Nb，幾乎不會有提升鋼板再結晶溫度的弊端，可適用於例如專利文獻2所揭示使用碳鋼線的廉價高速酸洗手法。(3) Generally, if Nb is added, the recrystallization temperature of the steel sheet rises. However, if a very small amount of Nb is added, there is almost no disadvantage of raising the recrystallization temperature of the steel sheet, and it is suitable for use, for example, in the use of carbon steel disclosed in Patent Document 2. Cheap high-speed pickling techniques for the line.

(4)即便在熔接時因氣體遮蔽不完全而導致大氣中的N混入於熔接部，但若鋼中含有適量的Al，便會在熔接部生成AlN而可防止敏化。又，若使鋼中含有適量的Sb，在熔接部會生成Sb與N的化合物便可防止敏化。(4) Even if the N in the atmosphere is mixed into the welded portion due to incomplete gas shielding during welding, if an appropriate amount of Al is contained in the steel, AlN is formed in the welded portion to prevent sensitization. Further, if an appropriate amount of Sb is contained in the steel, a compound of Sb and N is formed in the welded portion to prevent sensitization.

(5)氮化鈦細脈瑕疵的主要原因係起因於鋼板的極表層部存在粗大的TiN。藉由將Ti含有量予以最佳化，便可防止氮化鈦細脈瑕疵的發生。(5) The main cause of the titanium nitride fine veins is due to the presence of coarse TiN in the surface layer portion of the steel sheet. By optimizing the Ti content, it is possible to prevent the occurrence of titanium nitride fine veins.

依上述，發現即便熔接部仍具有良好的耐蝕性，在熱軋退火酸洗板未施行表面研削之情況下，可製作良好表面品質的冷軋退火酸洗板，可獲得相較於Ni系的沃斯田鐵系不鏽鋼之下，較廉價的肥粒鐵系不鏽鋼。According to the above, it was found that even if the welded portion has good corrosion resistance, the cold-rolled annealed pickled sheet having good surface quality can be produced in the case where the hot-rolled annealed pickled sheet is not subjected to surface grinding, and can be obtained as compared with the Ni-based one. Under the iron of the Vostian iron system, the cheaper ferrite iron is stainless steel.

本發明係根據以上發現而完成，主旨係如下。The present invention has been completed on the basis of the above findings, and the gist is as follows.

[1]一種肥粒鐵系不鏽鋼，係依質量%計，含有：C： 0.003~0.015%、Si：0.05~0.30%、Mn：0.10~0.35%、P：0.06%以下、S：0.02%以下、Cr：17.0~19.0%、Ni：超過0.10%~0.30%、Ti：0.10~0.40%、Nb：0.005%~未滿0.050%、Mo：未滿0.20%、N：0.005~0.015%、Cu：0.30~0.50%、Mg：未滿0.0005%，其餘則由Fe及不可避免的雜質構成。[1] A fat-grained iron-based stainless steel, based on % by mass, containing: C: 0.003 to 0.015%, Si: 0.05 to 0.30%, Mn: 0.10 to 0.35%, P: 0.06% or less, S: 0.02% or less, Cr: 17.0 to 19.0%, Ni: more than 0.10% to 0.30%, Ti: 0.10 ~0.40%, Nb: 0.005%~ less than 0.050%, Mo: less than 0.20%, N: 0.005~0.015%, Cu: 0.30~0.50%, Mg: less than 0.0005%, and the rest by Fe and inevitable Impurity composition.

[2]如上述[1]所記載的肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Al：0.02~0.50%。[2] The ferrite-based stainless steel according to the above [1], which further contains Al: 0.02 to 0.50% by mass%.

[3]如上述[2]所記載的肥粒鐵系不鏽鋼，其中，依質量%計含有Al：0.10~0.50%。[3] The ferrite-based stainless steel according to the above [2], which contains Al: 0.10 to 0.50% by mass%.

[4]如上述[1]至[3]中任一項所記載的肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Sb：0.005~0.30%。[4] The ferrite-based stainless steel according to any one of the above [1] to [3], further comprising Sb: 0.005 to 0.30% by mass%.

[5]如上述[1]至[4]中任一項所記載的肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Zr：0.05~0.60%、V：0.02~0.50%中之一種或二種。[5] The ferrite-based stainless steel according to any one of the above [1] to [4], further comprising one of Zr: 0.05 to 0.60% and V: 0.02 to 0.50% by mass%. Or two.

本發明的肥粒鐵系不鏽鋼係即便與沃斯田鐵系不鏽鋼熔接，熔接部的耐蝕性及表面性狀仍優異，因而適宜於廚房機器、建築內裝材料、工業機械、汽車零件等。The ferrite-based stainless steel of the present invention is excellent in corrosion resistance and surface properties of the welded portion even if it is welded to the Worthfield iron-based stainless steel, and is suitable for use in kitchen equipment, building interior materials, industrial machinery, automobile parts, and the like.

以下，針對本發明各構成要件的限定理由進行說明。Hereinafter, the reasons for limiting the respective constituent elements of the present invention will be described.

1.相關成分組成1. Composition of related ingredients

首先，針對規定本發明鋼成分組成的理由進行說明。另外，「成分%」均係指「質量%」。First, the reason for specifying the composition of the steel of the present invention will be described. In addition, "% of composition" means "% by mass".

C：0.003~0.015%C: 0.003~0.015%

C係容易與Cr鍵結形成Cr碳化物，在熔接時若熱影響區(Heat Affected Zone)形成Cr碳化物，便會成為晶界腐蝕的原因，故C越少越好。因此，將C設為0.015%以下。另一方面，即便過少，因為在精煉時需要較多時間，因而將C量設為0.003~0.015%之範圍。就熔接部的耐蝕性觀點而言，較佳係0.003~0.012%之範圍，更佳係0.003~0.010%之範圍。The C system is liable to form Cr carbides with Cr bonds. If Cr carbides are formed in the Heat Affected Zone during welding, they will cause grain boundary corrosion, so the less C, the better. Therefore, C is set to be 0.015% or less. On the other hand, even if it is too small, since it takes much time in refining, the amount of C is set to the range of 0.003 - 0.015%. From the viewpoint of corrosion resistance of the welded portion, it is preferably in the range of 0.003 to 0.012%, more preferably in the range of 0.003 to 0.010%.

Si：0.05~0.30%Si: 0.05~0.30%

Si係作為脫氧劑的有用元素，因而設定為0.05%以上。另一方面，若超過0.30%，在使用碳鋼線的高速酸洗方法中，會導致冷軋板的酸洗性劣化，造成生產性降低。因此，將Si量設為0.05~0.30%之範圍。較佳係0.05~0.20%之範圍。Since Si is a useful element of a deoxidizer, it is set to 0.05% or more. On the other hand, when it exceeds 0.30%, in the high-speed pickling method using a carbon steel wire, the pickling property of the cold-rolled sheet deteriorates, and productivity falls. Therefore, the amount of Si is set to be in the range of 0.05 to 0.30%. It is preferably in the range of 0.05 to 0.20%.

Mn：0.10~0.35%Mn: 0.10~0.35%

Mn係具有脫酸作用，因而含有0.10%以上。又，因為屬於沃斯田鐵相促進元素(austenite former element)，因而促進與沃斯田鐵系不鏽鋼間之熔接部(以下稱「異種鋼熔接部」)的麻田散鐵相形成。但是，當添加過剩時，則與鋼中存在的S鍵結，而形成屬於可溶性硫化物(soluble sulfides)的MnS，導致耐蝕性降低，因而將Mn量設為0.10~0.35%之範圍。較佳係0.10~0.25%之範圍。Since Mn has a deacidification action, it contains 0.10% or more. In addition, since it belongs to the austenite former element, it promotes the formation of the granulated iron phase of the welded joint between the Worthite iron-based stainless steel (hereinafter referred to as "dissimilar steel welded portion"). However, when the addition is excessive, the S is bonded to the S in the steel to form MnS which is soluble sulfides, and the corrosion resistance is lowered. Therefore, the amount of Mn is set to be in the range of 0.10 to 0.35%. It is preferably in the range of 0.10 to 0.25%.

P：0.06%以下P: 0.06% or less

若P超過0.06%，不僅損害到耐蝕性，亦因固溶強化(solid solution strengthening)而導致加工性降低。因此，將P量設為0.06%以下。就耐蝕性的觀點而言，較佳係0.04%以下。When P exceeds 0.06%, not only the corrosion resistance is impaired, but also the workability is lowered due to solid solution strengthening. Therefore, the amount of P is set to 0.06% or less. From the viewpoint of corrosion resistance, it is preferably 0.04% or less.

S：0.02%以下S: 0.02% or less

S係有害於耐蝕性的元素。特別係與Mn同時存在時，形成MnS而成為孔蝕的起點，導致耐蝕性劣化。此種作用係若超過0.02%便會趨於明顯。因此，將S量設為0.02%以下。就耐蝕性的觀點而言，較佳係0.01%以下，更佳係0.006%以下。S is an element that is harmful to corrosion resistance. In particular, when Mn is present at the same time, MnS is formed and becomes a starting point of pitting corrosion, resulting in deterioration of corrosion resistance. This effect will tend to be more pronounced if it exceeds 0.02%. Therefore, the amount of S is made 0.02% or less. From the viewpoint of corrosion resistance, it is preferably 0.01% or less, more preferably 0.006% or less.

Cr：17.0~19.0%Cr: 17.0~19.0%

Cr係使在不鏽鋼表面上形成鈍化膜，而提升母材耐蝕性的不可或缺元素。為能獲得良好的耐蝕性，必需添加達17.0%以上。但是，添加超過19.0%，會導致在與SUS304間之異種鋼熔接部處無法生成麻田散鐵，造成無法防止耐蝕性降低。因此，將Cr量設為17.0~19.0%之範圍。較佳係17.5~18.5%之範圍。The Cr system forms an indispensable element for forming a passivation film on the surface of the stainless steel to improve the corrosion resistance of the base material. In order to obtain good corrosion resistance, it is necessary to add up to 17.0% or more. However, when it is added more than 19.0%, the granulated iron cannot be formed at the dissimilar steel welded portion between the SUS304 and the SUS304, and the corrosion resistance cannot be prevented from being lowered. Therefore, the amount of Cr is set to be in the range of 17.0 to 19.0%. Preferably, it is in the range of 17.5 to 18.5%.

Ni：超過0.10%~0.30%Ni: more than 0.10%~0.30%

Ni係對耐間隙腐蝕性(crevice corrosion resistance)改善具貢獻的元素。又，與Mn同樣的均屬於沃斯田鐵相生成促進元素，因而促進異種鋼熔接部的麻田散鐵相形成。但是，若添加超過0.30%，便會導致SCC敏感性提高，且亦屬於高價位元素。因此，將Ni量設定為超過0.10%~0.30%之範圍。較佳係0.20~0.30%之範圍。Ni is an element contributing to the improvement of crevice corrosion resistance. Further, the same as Mn belongs to the iron phase formation promoting element of the Vostian, and thus the formation of the granulated iron phase of the dissimilar steel welded portion is promoted. However, if it is added more than 0.30%, it will lead to an increase in SCC sensitivity and also a high-priced element. Therefore, the amount of Ni is set to be in the range of more than 0.10% to 0.30%. It is preferably in the range of 0.20 to 0.30%.

Ti：0.10~0.40%Ti: 0.10~0.40%

Ti係如前述，屬於為確保與沃斯田鐵系不鏽鋼間之異種鋼熔接部的耐蝕性，必要不可或缺的元素。但是若添加過剩，便會造成TiN析出量增加，導致氮化鈦細脈瑕疵趨於明顯，若未施行熱軋退火酸洗板的表面研削等，便無法將製品板(冷軋退火酸洗板)的表面性狀保持良好。因此，將Ti量設為0.10~0.40%之範圍。就異種鋼熔接部的耐蝕性觀點而言，較佳係0.20~0.40%之範圍。As described above, the Ti system is an element which is indispensable for ensuring the corrosion resistance of the dissimilar steel welded portion between the Worth and the stainless steel. However, if the addition is excessive, the amount of precipitation of TiN will increase, and the fine veins of titanium nitride tend to be conspicuous. If the surface of the hot-rolled annealing pickling plate is not subjected to grinding, the product sheet cannot be rolled (cold-rolled annealed pickled sheet) The surface properties remain good. Therefore, the amount of Ti is set to be in the range of 0.10 to 0.40%. From the viewpoint of corrosion resistance of the dissimilar steel welded portion, it is preferably in the range of 0.20 to 0.40%.

Nb：0.005%~未滿0.050%Nb: 0.005%~ less than 0.050%

Nb的微量添加亦是本發明相關的重要要件之一。Nb係較Cr、Ti更優先形成碳氮化物。特別係在異種鋼熔接部，於熔融池(weld metal)及熱影響區，在較生成Ti碳氮化物的溫度更高溫下，開始生成Nb碳氮化物。於後續的冷卻過程中，雖理由尚未明朗，但以Nb碳氮化物作為成核位置，生成大量含有Ti的碳氮化物。即，藉由微量的Nb添加，促進Ti碳氮化物的生成，因而相較於未含有Nb的情況下，藉由異種鋼熔接部的熔融池、熱影響區的Ti而強化C、N的固定能力，便能更有效地防止敏化。因此，將本發明Nb量的下限設為0.005%以上。另一方面，若添加Nb過剩，則冷軋板的再結晶溫度(recrystallization temperature)上昇，因而為能獲得充分的機械性質，便必需利用高溫施行退火。因此，相較於無添加Nb的情況下，完工退火(finishing annealing)時所生成的氧化膜會厚厚地成長。因此，前述所使用利用碳鋼線的高速酸洗方法，會導致冷軋板的酸洗性劣化，造成生產性降低。故，將Nb量設為0.005%~未滿0.050%之範圍。就異種鋼熔接部的耐蝕性觀點而言，較佳係0.010%~未滿0.050%之範圍。The micro-addition of Nb is also one of the important requirements related to the present invention. Nb is more preferred than Cr and Ti to form carbonitrides. In particular, in the dissimilar steel welded portion, in the weld metal and the heat-affected zone, Nb carbonitride is formed at a higher temperature than the temperature at which the Ti carbonitride is formed. In the subsequent cooling process, although the reason is not clear, a large amount of carbonitride containing Ti is formed by using Nb carbonitride as a nucleation site. In other words, since the formation of Ti carbonitride is promoted by the addition of a small amount of Nb, the fixation of C and N is enhanced by the molten pool of the dissimilar steel welded portion and the Ti in the heat-affected zone as compared with the case where Nb is not contained. Ability can prevent sensitization more effectively. Therefore, the lower limit of the amount of Nb of the present invention is made 0.005% or more. On the other hand, if the addition of Nb is excessive, the recrystallization temperature of the cold-rolled sheet rises. Therefore, in order to obtain sufficient mechanical properties, it is necessary to perform annealing at a high temperature. Therefore, the oxide film formed during finishing annealing grows thickly compared to the case where no Nb is added. Therefore, the high-speed pickling method using the carbon steel wire as described above causes deterioration of the pickling property of the cold-rolled sheet, resulting in a decrease in productivity. Therefore, the amount of Nb is set to be in the range of 0.005% to less than 0.050%. From the viewpoint of corrosion resistance of the dissimilar steel welded portion, it is preferably in the range of 0.010% to less than 0.050%.

Mo：未滿0.20%Mo: less than 0.20%

Mo係強化鈍化膜(passivation film)，使耐蝕性明顯提升。但是，因屬於肥粒鐵相生成促進元素，即便微量添加，亦會導致與沃斯田鐵系不鏽鋼間之異種鋼熔接部處無法生成麻田散鐵相。因此，異種鋼熔接部會成為肥粒鐵相而發生敏化。故，將Mo量設為未滿0.20%。又，因為Mo會導致熱軋板的韌性降低，因而較佳係未滿0.10%。再者，Mo的下限係設為0。Mo is a passivation film that enhances corrosion resistance. However, because it is a ferrite-grain-producing element, even if it is added in a small amount, it will cause a disproportionate iron phase in the weld of the dissimilar steel between the Worthfield iron-based stainless steel. Therefore, the dissimilar steel welded portion becomes a ferrite-iron phase and is sensitized. Therefore, the amount of Mo is set to less than 0.20%. Further, since Mo causes a decrease in the toughness of the hot rolled sheet, it is preferably less than 0.10%. Furthermore, the lower limit of Mo is set to zero.

N：0.005~0.015%N: 0.005~0.015%

N係容易與Cr相鍵結而形成Cr氮化物。在熔接時，若於異種鋼熔接部及熱影響區形成Cr氮化物，便會成為晶界腐蝕(intergranular corrosion)的原因，故N越少越佳。又，為減少成為氮化鈦細脈瑕疵原因的TiN析出量，最好盡可能減少。但是，即便過少，在精煉時仍較耗時間，因而將N量設為0.005~0.015%之範圍。就異種鋼熔接部的耐蝕性觀點而言，較佳係0.005~0.012%之範圍，更佳係0.005~0.010%之範圍。The N system is easily bonded to the Cr phase to form a Cr nitride. In the case of welding, if it is in dissimilar steel When the Cr nitride is formed in the welded portion and the heat-affected region, it becomes a cause of intergranular corrosion, so the smaller the N, the better. Further, in order to reduce the amount of precipitation of TiN which is a cause of titanium nitride fine veins, it is preferable to reduce as much as possible. However, even if it is too small, it takes time to refine, and therefore the amount of N is set to be in the range of 0.005 to 0.015%. From the viewpoint of corrosion resistance of the dissimilar steel welded portion, it is preferably in the range of 0.005 to 0.012%, more preferably in the range of 0.005 to 0.010%.

Cu：0.30~0.50%Cu: 0.30~0.50%

Cu係提高耐蝕性(特別係在水溶液中、或有附著弱酸性水滴時的耐蝕性)的元素。理由係Cu會先溶解於水溶液或水滴中之後，再度附著於原料生鐵表面上，而抑制原料生鐵的熔解之緣故。但是，若Cu量超過0.50%，除會降低熱軋加工性之外，於熱軋時在熱軋鋼胚上會生成所謂「紅色鏽皮」之因Cu所造成的飴糖狀氧化物，成為表面缺陷的原因。因此，將Cu量設定為0.30~0.50%之範圍。就熱軋加工性的觀點而言，較佳係0.30~0.40%之範圍。Cu is an element which improves corrosion resistance (especially in an aqueous solution or corrosion resistance when a weakly acidic water droplet adheres). The reason is that Cu is first dissolved in an aqueous solution or water droplets, and then adhered to the surface of the raw material pig iron to suppress the melting of the raw material pig iron. However, when the amount of Cu exceeds 0.50%, in addition to lowering the hot-rolling workability, a so-called "red scale" of a so-called "red scale" is formed on the hot-rolled steel sheet during hot rolling to form a surface defect. s reason. Therefore, the amount of Cu is set to a range of 0.30 to 0.50%. From the viewpoint of hot rolling workability, it is preferably in the range of 0.30 to 0.40%.

Mg：未滿0.0005%Mg: less than 0.0005%

Mg係主要從轉爐中的磚而混入的雜質。又，Mg係成為多種多樣介質的起點，亦會成為其他介質的成核位置。又，即便施行退火等仍不易再固溶，因而會導致熱軋退火酸洗板、製品板(冷軋退火酸洗板)的表面性狀劣化。因此，將Mg量設為未滿0.0005%。為保持良好的表面性狀，較佳係設為未滿0.0003%。The Mg system mainly contains impurities mixed from bricks in the converter. Moreover, the Mg system is the starting point for a variety of media, and it also becomes a nucleation site for other media. Further, even if annealing or the like is performed, it is difficult to re-dissolve, and thus the surface properties of the hot-rolled annealed pickled sheet and the product sheet (cold-rolled annealed pickled sheet) are deteriorated. Therefore, the amount of Mg is set to less than 0.0005%. In order to maintain good surface properties, it is preferably set to less than 0.0003%.

以上係本發明的基本化學成分，其餘係由Fe及不可避免的雜質構成，又就TIG熔接的氣體遮蔽、與防止異種鋼熔接部敏化觀點而言，亦可將Al、Sb當作選擇元素添加。又，在提升異種鋼熔接部耐蝕性之目的下，亦可將Zr、V當作選擇元素添加。另外，不可避的雜質係例如可容許Ca：0.0020%以下，但並不侷限於此。The above is the basic chemical composition of the present invention, and the rest is composed of Fe and unavoidable impurities, and Al and Sb can also be selected as a selection element from the viewpoint of gas shielding of TIG welding and sensitization of welding of dissimilar steel. Add to. Further, Zr and V may be added as selection elements for the purpose of improving the corrosion resistance of the dissimilar steel welded portion. In addition, it is inevitable The impurity is, for example, Ca: 0.0020% or less, but is not limited thereto.

Al：0.02~0.50%Al: 0.02~0.50%

Al係當TIG熔接的氣體遮蔽不足時，便成為特別重要的元素。如前述，當TIG熔接時，一般係將背面施行氣體遮蔽再施行熔接。但是，當異種鋼熔接部的形狀較為複雜時，氣體遮蔽便不足，會有大氣中的N混入熔融池中的情況。此情況，若C、N量超過麻田散鐵相的固溶限(solid solubility limit)，僅依靠Ti並無法完全防止敏化。此種情況下，預先添加Al便能有效地防止敏化。理由係Al會將混入熔融池中的N形成AlN並固定之緣故。此項效果係依Al含有達0.02%以上便可獲得。但是，若Al含有超過0.50%，在鋼胚階段會生成非金屬系介質，導致成為熱軋板、冷軋板的表面性狀劣化之原因。因此，當含有Al的情況，Al量較佳係設為0.02~0.50%之範圍。更佳的下限係0.10%、特佳係0.15%。更佳的上限係0.30%。Al is a particularly important element when the gas shielding of TIG welding is insufficient. As described above, when the TIG is welded, the back side is generally shielded by gas and then welded. However, when the shape of the dissimilar steel welded portion is complicated, gas shielding is insufficient, and N in the atmosphere may be mixed into the molten pool. In this case, if the amount of C and N exceeds the solid solubility limit of the methadrite phase, it is impossible to completely prevent sensitization by relying only on Ti. In this case, the addition of Al in advance can effectively prevent sensitization. The reason is that Al will form AlN in the molten pool and fix it. This effect is obtained by containing Al in an amount of 0.02% or more. However, when the content of Al is more than 0.50%, a non-metallic medium is formed in the steel embryo stage, which causes deterioration of the surface properties of the hot-rolled sheet and the cold-rolled sheet. Therefore, when Al is contained, the amount of Al is preferably in the range of 0.02 to 0.50%. A more preferred lower limit is 0.10%, and a particularly preferred ratio is 0.15%. A better upper limit is 0.30%.

Sb：0.005~0.30%Sb: 0.005~0.30%

Sb亦係與Al同樣的，當TIG熔接的氣體遮蔽不足時，具有捕捉從大氣中混入的N之效果，屬於當複雜形狀的構造體時，最好添加的良好元素。但是，若Sb添加過剩，在鋼胚階段會生成非金屬系介質，導致成為熱軋板、冷軋板的表面性狀劣化之原因。因此，當有添加Sb的情況，Sb量較佳係設為0.005~0.30%之範圍。就製品板(冷軋退火酸洗板)的表面性狀觀點而言，較佳係0.005~0.10%之範圍。Sb is also the same as Al. When the gas shielding of TIG welding is insufficient, it has the effect of capturing N mixed in the atmosphere, and is a good element to be added when it is a structure having a complicated shape. However, when Sb is excessively added, a non-metallic medium is formed in the steel embryo stage, which causes deterioration of the surface properties of the hot-rolled sheet and the cold-rolled sheet. Therefore, when Sb is added, the amount of Sb is preferably set to be in the range of 0.005 to 0.30%. From the viewpoint of the surface properties of the product sheet (cold rolled annealed pickled sheet), it is preferably in the range of 0.005 to 0.10%.

Zr：0.05~0.60%Zr: 0.05~0.60%

Zr係與Ti同樣，屬於會較Cr更優先地形成碳氮化物，而提升同種鋼、異種鋼熔接部之耐蝕性的元素。但是，Zr的價位較高於Ti，且若Zr添加過剩，便會生成介金屬化合物，導致熱軋板的韌性劣化。因此，當有添加Zr的情況，Zr量較佳係設為0.05~0.60%之範圍，更佳係0.15~0.35%之範圍。Like the Ti, the Zr system is an element which forms a carbonitride more preferentially than Cr and enhances the corrosion resistance of the welded portion of the same steel or dissimilar steel. However, the price of Zr is higher than that of Ti, and if Zr is excessively added, a metal intermetallic compound is formed, resulting in deterioration of toughness of the hot rolled sheet. because Therefore, when Zr is added, the amount of Zr is preferably in the range of 0.05 to 0.60%, more preferably in the range of 0.15 to 0.35%.

V：0.02~0.50%V: 0.02~0.50%

V亦係與Ti同樣的，屬於會較Cr更優先地形成碳氮化物，而提升同種鋼、異種鋼熔接部之耐蝕性的元素。但是，此項效果較小於Ti。且，亦屬於高價位元素。因此，當有添加V的情況，V量較佳係設為0.02~0.50%之範圍，更佳係0.02~0.05%之範圍。V is also the same as Ti, and belongs to an element which forms a carbonitride more preferentially than Cr and enhances the corrosion resistance of the same type of steel and dissimilar steel. However, this effect is smaller than Ti. Also, it is also a high-priced element. Therefore, when V is added, the amount of V is preferably in the range of 0.02 to 0.50%, more preferably in the range of 0.02 to 0.05%.

2.相關製造條件2. Relevant manufacturing conditions

其次，針對本發明鋼的較佳製造方法進行說明。利用轉爐、電爐、真空熔解爐等公知方法熔製上述較佳成分組成的鋼，並利用連續鑄造法或造塊-分塊法形成鋼素材(鋼胚)。該鋼素材後續利用1100~1250℃加熱1~24小時、或在未加熱的情況下直接施行熱軋形成熱軋板。Next, a preferred method of producing the steel of the present invention will be described. The steel of the above preferred composition is melted by a known method such as a converter, an electric furnace, or a vacuum melting furnace, and a steel material (steel blank) is formed by a continuous casting method or a block-blocking method. The steel material is subsequently heated at 1100 to 1250 ° C for 1 to 24 hours, or directly subjected to hot rolling without heating to form a hot rolled sheet.

熱軋板通常係依800~1100℃施行1~10分鐘的熱軋板退火，依照用途亦可省略熱軋板退火。接著，經熱軋板酸洗後，利用冷軋形成冷軋板後，施行完工退火而形成製品板。冷軋係就延伸性、彎曲性、沖壓成形性及形狀矯正的觀點而言，較佳係依50%以上的軋縮率實施。冷軋板的完工退火一般而言，當JIS G0203的表面修整No.2B完工品時，就確保良好的機械性質、及酸洗性的觀點而言，較佳係依800~950℃施行退火。The hot-rolled sheet is usually annealed at 800 to 1100 ° C for 1 to 10 minutes, and the hot-rolled sheet annealing may be omitted depending on the application. Next, after pickling with a hot-rolled sheet, a cold-rolled sheet is formed by cold rolling, and finishing annealing is performed to form a product board. The cold rolling system is preferably carried out at a rolling reduction ratio of 50% or more from the viewpoints of elongation, bendability, press formability, and shape correction. Finishing Annealing of Cold Rolled Sheet Generally, when the surface of JIS G0203 is finished with No. 2B finished product, it is preferable to perform annealing at 800 to 950 ° C from the viewpoint of ensuring good mechanical properties and pickling properties.

但是，當利用冷連軋-CAL(tandem cold rolling and continuous annealing line)施行高生產性冷軋製品時，最佳係採取利用碳鋼線的前述碳鋼退火酸洗線之高速酸洗(參照專利文獻2)廉價製程進行製造，此時的退火溫度較佳係依800~900℃實施。又，就要求光澤地方的構件，利用BA退火施行完工退火亦屬有效。又，雖前有敘述，為能在冷軋後及加工後可獲得更良好的表面性狀，即便施行研磨等亦不會構成任何問題。However, when high-productivity cold-rolled products are used by cold-rolling and continuous annealing line (CAL), it is preferable to adopt high-speed pickling of the aforementioned carbon steel annealing pickling line using carbon steel wires (refer to the patent). Document 2) Manufacturing is carried out in an inexpensive process, and the annealing temperature at this time is preferably carried out at 800 to 900 °C. Moreover, it is also effective to perform the finish annealing by BAR annealing on the components in the gloss place. Also, although there is a description before, It is possible to obtain a better surface property after cold rolling and after processing, and it does not pose any problem even if it is subjected to grinding or the like.

[實施例1][Example 1]

以下根據實施例，針對本發明進行更詳細說明。Hereinafter, the present invention will be described in more detail based on examples.

利用50kg小型真空熔解爐，熔製具有表1所示發明例No.1~8及33、比較例No.9~12之組成的鋼。該等鋼塊在經Ar氣體施行沖洗過的爐內加熱至1150℃後，施行熱軋而形成板厚4.0mm的熱軋板。Steel having the compositions of Inventive Examples Nos. 1 to 8 and 33 and Comparative Examples Nos. 9 to 12 shown in Table 1 was melted by a 50 kg small vacuum melting furnace. These steel blocks were heated to 1,150 ° C in a furnace subjected to Ar gas treatment, and then hot rolled to form a hot rolled sheet having a thickness of 4.0 mm.

接著，對該等熱軋板在大氣中依950℃施行1分鐘的熱軋板退火後，再對表面施行玻璃珠的珠粒噴擊處理後，於溫度80℃的20質量%硫酸溶液中浸漬120秒後，再於由15質量%硝酸及3質量%氟酸構成的溫度55℃混合酸中浸漬60秒而施行酸洗，便施行脫鏽皮。Then, the hot-rolled sheets were annealed in a hot-rolled sheet at 950 ° C for 1 minute in the atmosphere, and then subjected to bead blasting treatment on the surface, and then immersed in a 20 mass% sulfuric acid solution at a temperature of 80 ° C. After 120 seconds, the mixture was immersed in a mixed acid of 15% by mass of nitric acid and 3% by mass of fluoric acid at a temperature of 55 ° C for 60 seconds to carry out pickling, and then derusted.

再者，利用冷軋形成板厚1.0mm的冷軋板，再利用大氣開放爐依900℃施行1分鐘退火，便獲得冷軋退火板。該冷軋退火板在溫度80℃、20質量%NaSO₄ 中，以鋼板為陽極，依3A/dm² 施行10秒鐘的電解酸洗計三次後，於由5質量%硝酸及3質量%氟酸構成的溫度55℃混合酸中浸漬30秒鐘，而施行脫鏽皮，便獲得冷軋退火酸洗板。Further, a cold-rolled sheet having a thickness of 1.0 mm was formed by cold rolling, and then annealed at 900 ° C for 1 minute in an open atmosphere furnace to obtain a cold-rolled annealed sheet. The cold-rolled annealed sheet was subjected to electrolytic pickling for 3 seconds at 3 °/dm ² at a temperature of 80 ° C and 20% by mass of NaSO ₄ , and then subjected to electrolytic cleaning by 3 A/dm ² for 3 times, and then by 5 mass% nitric acid and 3 mass% fluorine. The acid-constituted temperature was immersed in a mixed acid at 55 ° C for 30 seconds, and derusting was performed to obtain a cold-rolled annealed pickled sheet.

首先，依目視施行所獲得冷軋退火酸洗板的表面性狀判定。First, the surface properties of the cold-rolled annealed pickled sheets obtained were determined according to the visual observation.

接著，將所獲得冷軋退火酸洗板當作試體材料，而母材耐蝕性評價用的樣品係製作經脫鏽皮後的冷軋退火酸洗板之酸洗狀態材料、與經利用#600號研磨紙研磨表面過的研磨材料之2種樣品。Next, the obtained cold-rolled annealed pickled sheet is used as a test material, and the sample for evaluating the corrosion resistance of the base material is a pickled state material obtained by subjecting the cold-rolled annealed pickled sheet after peeling, and using # The No. 600 abrasive paper was used to grind two samples of the surface of the abrasive material.

進而，針對相同的試體材料，施行同材料的TIG熔接部試驗。此項試驗係從各自試體材料採取的2片板利用TIG熔接施行接合，再將該等的表面利用#600號研磨紙施行研磨，便形成同種鋼熔接部耐蝕性評價樣品。Further, a TIG welded portion test of the same material was carried out for the same test material. In this test, two sheets taken from the respective test materials were joined by TIG welding, and the surfaces were polished by #600 grinding paper to form a corrosion resistance evaluation sample of the same type of steel welded portion.

又，針對各試體材料，施行與SUS304的異種鋼TIG熔接試驗。此項試驗係將從各試體材料所採取的板、與板厚1.0mm之SUS304板利用TIG熔接施行接合，再將該等的表面利用#600號研磨紙施行研磨，便形成異種鋼熔接部耐蝕性評價樣品。同種鋼、異種鋼TIG熔接試驗條件均係如下述，依背面焊珠寬(width of the back bead)成為3mm以上的方式控制熔接電流，評價面係設為背面焊珠面。Further, a dissimilar steel TIG welding test with SUS304 was performed for each sample material. In this test, the plate taken from each sample material and the SUS304 plate having a thickness of 1.0 mm were joined by TIG welding, and the surfaces were polished by #600 grinding paper to form a dissimilar steel welded portion. Corrosion resistance evaluation samples. The TIG welding test conditions of the same steel and dissimilar steel were as follows, and the welding current was controlled so that the width of the back bead was 3 mm or more, and the evaluation surface was set as the back bead surface.

熔接電壓：10VWelding voltage: 10V

熔接電流：90~110AWelding current: 90~110A

熔接速度：600mm/minWelding speed: 600mm/min

電極：1.6mm鎢電極Electrode: 1.6mm tungsten electrode

保護氣體：前面焊珠側(front bead side)Ar 20L/min背面焊珠側(back bead side)Ar 20L/minProtective gas: front bead side Ar 20L/min back bead side Ar 20L/min

使用所獲得母材(酸洗狀態材料、研磨材料)、同種鋼熔接部、異種鋼熔接部樣品，根據JIS H 8502(1999)施行中性鹽霧循環腐蝕試驗(CCT、neutral salt spray cyclic corrosion test)。CCT係將5質量%NaCl溶液噴霧(35℃、2h)→乾燥(60℃、4h、相對濕度20~30%)→濕潤(40℃、2h、相對濕度95%以上)設為1循環，合計實施15循環。所獲得結果如表2所示。Using the obtained base material (pickled state material, abrasive material), the same type of steel welded joint, and the dissimilar steel welded joint sample, a neutral salt spray cyclic corrosion test (CCT, neutral salt spray cyclic corrosion test) is performed according to JIS H 8502 (1999). ). CCT is a 5 mass% NaCl solution spray (35 ° C, 2 h) → dry (60 ° C, 4 h, relative humidity 20 ~ 30%) → wet (40 ° C, 2 h, relative humidity 95% or more) set to 1 cycle, total 15 cycles were implemented. Result obtained As shown in table 2.

再者，各試驗的判定基準係如下。Furthermore, the criteria for the determination of each test are as follows.

(a)冷軋酸洗退火後的外觀：依照具有表面缺陷[結疤(scab)、針孔(pin hole)、線結疤(linear scab)、氮化鈦細脈瑕疵、白條紋(white streak)的色異常]部分的長度相對於板全長的比例進行判斷，缺陷率未滿5%者評為「◎」、缺陷率達5%以上且未滿10%者評為「○」、缺陷率達10%以上且未滿20%者評為「△」、缺陷率達20%以上者評為「×」，◎與○判定屬於合格，而△與×則判定屬於不合格。(a) Appearance after cold rolling pickling annealing: according to surface defects [scab, pin hole, linear scab, titanium nitride fine veins, white streaks (white streak The ratio of the length of the color abnormality portion to the total length of the plate is judged, and the defect rate is less than 5%, and the defect rate is 5% or more, and the defect rate is less than 5%, and the defect rate is evaluated as "○". Those who have reached 10% or more and less than 20% are rated as "△", those whose defect rate is 20% or more are rated as "X", ◎ and ○ are judged to be qualified, and △ and × are judged to be unqualified.

(b)酸洗狀態材料及#600號研磨材料的CCT結果：就經15循環試驗後的生鏽面積，將生鏽率(Rust area ratio)未滿10%者評為「◎」、將生鏽率達10%以上且未滿20%者評為「○」、將生鏽率達20%以上且未滿30%者評為「△」、將生鏽率達30%以上者評為「×」，◎與○判定屬於合格，而△與×則判定屬於不合格。(b) CCT results of pickling material and #600 abrasive material: For the rust area after 15 cycles of testing, the rust rate (Rust area ratio) is less than 10%, and it is rated as "◎". Those with a rust rate of 10% or more and less than 20% are rated as "○", those with a rust rate of 20% or more and those with a rust rate of 30% or less are rated as "△", and those with a rust rate of 30% or more are rated as "". ×", ◎ and ○ are judged to be qualified, and △ and × are judged to be unqualified.

(c)同種鋼熔接部耐蝕性試驗結果：利用同種鋼施行TIG突合熔接，再利用#600號研磨紙去除熔接部的回火色之後，將經CCT計15循環後的熔接部生鏽率未滿10%者評為「◎」、將生鏽率達10%以上且未滿20%者評為「○」、將生鏽率達20%以上且未滿30%者評為「△」、將生鏽率達30%以上者評為「×」，◎與○判定屬於合格，而△與×則判定屬於不合格。(c) Corrosion test results of the same type of steel welded joints: TIG joint welding was performed using the same steel, and the tempering color of the welded portion was removed by using #600 abrasive paper, and the rust rate of the welded portion after 15 cycles of CCT was not 10% of those rated as "◎", those with a rust rate of 10% or more and less than 20% were rated as "○", those with a rust rate of 20% or more and those with less than 30% were rated as "△". Those who have a rust rate of 30% or more are rated as "X", ◎ and ○ are judged to be qualified, and △ and × are judged to be unqualified.

(d)異種鋼熔接部耐蝕性試驗結果：施行SUS304與TIG突合熔接，再利用#600號研磨紙去除熔接部的回火色之後，將經CCT計15循環後的熔接部生鏽率未滿10%者評為「◎」、將生鏽率達10%以上且未滿20%者評為「○」、將生鏽率達20%以上且未滿30%者評為「△」、將生鏽率達30%以上者評為「×」，◎與○判定屬於合格，而△與×則判定屬於不合格。(d) Corrosion resistance test results of dissimilar steel welded joints: SUS304 and TIG were welded, and the tempering color of the welded portion was removed by #600 abrasive paper, and the rust rate of the welded portion after 15 cycles of CCT was not satisfied. 10% were rated as "◎", those with a rust rate of 10% or more and less than 20% were rated as "○", those with a rust rate of 20% or more and those with less than 30% were rated as "△", Those who have a rust rate of 30% or more are rated as "X", ◎ and ○ are judged to be qualified, and △ and × are judged to be unqualified.

屬於發明例的No.1~8及33，成分組成係在本發明範圍內，針對任一評價項目，呈現耐蝕性、表面性狀均優異。另一方面，Cr量為16.2%之偏低的比較例No.9，生鏽面積較多、耐蝕性差。No. 1 to 8 and 33 belonging to the invention examples are within the scope of the present invention, and are excellent in corrosion resistance and surface properties for any of the evaluation items. On the other hand, Comparative Example No. 9 in which the amount of Cr was as low as 16.2% was large in rust area and poor in corrosion resistance.

又，若Cr量為19.4%之偏高的比較例No.10，異種鋼熔接部的生鏽面積較大、耐蝕性差。此現象可認為係因為屬於肥粒鐵生成促進元素的Cr量較高，因而異種鋼熔接部不會麻田散鐵化的原因。Further, in Comparative Example No. 10 in which the amount of Cr was 19.4%, the dissimilar steel welded portion had a large rust area and poor corrosion resistance. This phenomenon is considered to be because the amount of Cr which is a ferrite-producing iron-promoting element is high, and thus the dissimilar steel welded portion does not cause erection.

又，Ti量為0.07%之偏少的比較例No.11，異種鋼熔接部的生鏽面積較大、耐蝕性差。Further, in Comparative Example No. 11 in which the amount of Ti was less than 0.07%, the dissimilar steel welded portion had a large rust area and poor corrosion resistance.

進而，Si量與Nb量超越本發明範圍的比較例No.12，於母材表面上確認了若干的鏽皮殘留，冷軋退火酸洗後的耐蝕性差。Further, in Comparative Example No. 12 in which the amount of Si and the amount of Nb exceeded the range of the present invention, a certain amount of scale remained on the surface of the base material, and corrosion resistance after cold rolling annealing and pickling was inferior.

[實施例2][Embodiment 2]

其次，利用150tonVOD(Vacuum Oxygen Decaburization，真空氧氣脫碳)，熔製具有表3所示發明例No.13~18、比較例No.19~22之成分組成的肥粒鐵系不鏽鋼之後，利用連續鑄造進行鑄造成鋼胚。將其加熱至1150℃溫度並施行熱軋，形成板厚4.0mm的熱軋鋼捲。接著，在950℃下、且空氣比1.3的煉焦爐氣燃燒環境中施行1~5分鐘的退火，再對表面施行鐵球珠的珠粒噴擊處理(shot blasting)後，於溫度80℃的20質量%硫酸溶液中浸漬120秒後，再於由15質量%硝酸及3質量%氟酸構成的溫度55℃混合酸中浸漬60秒而施行酸洗，便施行脫鏽皮，形成熱軋退火酸洗鋼捲。進而，利用冷軋形成板厚1.0mm的冷軋板，於900℃下在空氣比1.3的煉焦爐氣燃燒環境中施行2分鐘退火，再於溫度80℃、20質量%NaSO₄ 中，以鋼板為陽極，並依3A/dm² 施行10秒的電解酸洗(electrolytic descaling)計三次後，再於由5質量%硝酸及3質量%氟酸構成的溫度55℃混合酸中浸漬30秒鐘，而施行脫鏽皮，便獲得冷軋退火酸洗板。Next, 150-ton VOD (Vacuum Oxygen Decaburization) was used to melt the ferrite-based iron-based stainless steel having the composition of Inventive Examples No. 13 to 18 and Comparative Examples Nos. 19 to 22 shown in Table 3, and then continuous Casting is cast into steel embryos. This was heated to a temperature of 1,150 ° C and hot rolled to form a hot rolled steel coil having a thickness of 4.0 mm. Next, it is annealed at 950 ° C for 1 to 5 minutes in a coke oven gas combustion environment with an air ratio of 1.3, and after the surface is subjected to shot blasting of the iron ball, the temperature is 80 ° C. After immersing in a 20% by mass sulfuric acid solution for 120 seconds, it is immersed in a mixed acid of 15% by mass of nitric acid and 3% by mass of fluoric acid at a temperature of 55 ° C for 60 seconds to perform pickling, and then subjected to descaling to form hot rolling annealing. Pickled steel coils. Further, a cold-rolled sheet having a thickness of 1.0 mm was formed by cold rolling, and annealed at 900 ° C for 2 minutes in a combustion atmosphere of a coke oven gas having an air ratio of 1.3, and then at a temperature of 80 ° C and 20% by mass of NaSO ₄ as a steel sheet. The anode was subjected to electrolytic descaling for 3 seconds in accordance with 3 A/dm ² for three times, and then immersed in a mixed acid of 55 ° C composed of 5 mass% nitric acid and 3 mass% hydrofluoric acid for 30 seconds. The derusted skin is obtained, and a cold rolled annealed pickled sheet is obtained.

首先，依目視施行依此所獲得冷軋退火酸洗板的表面性狀判定。First, the surface properties of the cold-rolled annealed pickled sheet obtained in this manner were determined according to the visual observation.

接著，與實施例1同樣地製作母材、同種鋼熔接部、異種鋼熔接部樣品，並與實施例1同樣地根據JIS H 8502(1999)施行中性鹽霧循環腐蝕試驗(CCT)，並施行耐蝕性評價試驗。所獲得結果如表4所示。再者，各試驗的判定基準係與實施例1相同。Then, a base material, a steel-type welded portion, and a sample of a dissimilar steel welded portion were produced in the same manner as in Example 1, and a neutral salt spray cyclic corrosion test (CCT) was carried out in accordance with JIS H 8502 (1999) in the same manner as in Example 1. A corrosion resistance evaluation test was performed. The results obtained are shown in Table 4. In addition, the criterion for the determination of each test is the same as that of the first embodiment.

屬於發明例的No.13~18，成分組成係在本發明範圍內，針對任一評價項目，呈現耐蝕性、表面性狀均優異。No. 13 to 18 belonging to the invention examples are within the scope of the present invention, and are excellent in corrosion resistance and surface properties for any of the evaluation items.

另一方面，屬於比較例的No.19，因為Mo量為0.40%較高於本發明範圍，同樣的屬於比較例的No.20，因為Cr量為19.5%較高於本發明範圍，因而異種鋼熔接部的生鏽面積較大、耐蝕性差。此現象可認為係因為屬於肥粒鐵相生成促進元素的Mo量及Cr量偏高，因而異種鋼熔接部不會麻田散鐵化的原因。On the other hand, No. 19 belonging to the comparative example, since the amount of Mo is 0.40% is higher than the range of the present invention, and the same is No. 20 of the comparative example, since the amount of Cr is 19.5% higher than the range of the present invention, and thus heterogeneous The steel welded portion has a large rust area and poor corrosion resistance. This phenomenon is considered to be because the amount of Mo and the amount of Cr which are the promoting elements of the ferrite grain iron phase are relatively high, and thus the dissimilar steel welded portion does not cause the reason for the ironation of the field.

又，比較例No.21係Si量為0.33%、Nb量為0.003%，均偏離本發明範圍，同樣的比較例No.22係Si量為0.45%、Mg量為0.0010%，均逾越本發明範圍，因而確認了若干的鏽皮殘留，冷軋退火酸洗後的耐蝕性差。Further, in Comparative Example No. 21, the amount of Si was 0.33%, and the amount of Nb was 0.003%, which deviated from the range of the present invention. The same Comparative Example No. 22 had a Si amount of 0.45% and a Mg amount of 0.0010%, both exceeding the present invention. As a result, a certain amount of scale residue was confirmed, and the corrosion resistance after cold rolling annealing and pickling was poor.

[實施例3][Example 3]

利用50kg小型真空熔解爐，熔製具有表5所示發明例No.23~28、比較例No.29~32之成分組成的鋼。將該等鋼塊在經Ar氣體施行沖洗過的爐內加熱至1150℃後，施行熱軋，便形成板厚4.0mm的熱軋板。Steel having the composition of Inventive Examples No. 23 to 28 and Comparative Examples Nos. 29 to 32 shown in Table 5 was melted by a 50 kg small vacuum melting furnace. These steel blocks were heated to 1,150 ° C in an oven which was subjected to Ar gas treatment, and then hot rolled to form a hot rolled sheet having a thickness of 4.0 mm.

接著，將該等熱軋板在大氣中於950℃下施行1分鐘的熱軋板退火後，對表面施行玻璃珠的珠粒噴擊處理，再於溫度80℃的20質量%硫酸溶液中浸漬120秒後，於由15質量%硝酸及3質量%氟酸構成的溫度55℃混合酸中浸漬60秒施行酸洗，而施行脫鏽皮。Then, the hot-rolled sheets were annealed in a hot-rolled sheet at 950 ° C for 1 minute in the atmosphere, and then subjected to bead blasting treatment on the surface of the glass beads, followed by immersion in a 20 mass% sulfuric acid solution at a temperature of 80 ° C. After 120 seconds, the mixture was immersed in a mixed acid of 15% by mass of nitric acid and 3% by mass of fluoric acid at a temperature of 55 ° C for 60 seconds to carry out pickling, and derusting was performed.

進而，利用冷軋形成板厚1.0mm的冷軋板，於還原性環境(H₂ ：5vol%、N₂ ：95vol%、露點-40℃)中，依900℃施行1分鐘的退火，獲得冷軋退火板。將該冷軋退火板於溫度50℃、於由15質量%硝酸及0.5質量%鹽酸構成的溶液中，以鋼板為陽極施行電氣分解(10A/dm² 、2秒)計施行2次脫鏽皮，獲得冷軋退火酸洗板。Further, a cold-rolled sheet having a thickness of 1.0 mm was formed by cold rolling, and annealing was performed at 900 ° C for 1 minute in a reducing atmosphere (H ₂ : 5 vol%, N ₂ : 95 vol%, dew point - 40 ° C) to obtain cold. Roll annealed sheets. The cold-rolled annealed sheet was subjected to electrical decomposing (10 A/dm ² , 2 seconds) in a solution of 15% by mass of nitric acid and 0.5% by mass of hydrochloric acid at a temperature of 50° C. , obtaining cold rolled annealed pickled sheets.

接著，將冷軋退火酸洗板當作試體材料，並與實施例1同樣的製作經脫鏽皮後的冷軋退火酸洗板之酸洗狀態材料、與經利用#600號研磨紙研磨表面過的研磨材料之2種母材耐蝕性評價用樣品。Next, the cold-rolled annealed pickled sheet was used as a test material, and the pickled state material of the cold-rolled annealed pickled sheet after derusting was produced in the same manner as in Example 1, and was ground with a #600 grinding paper. Two samples of the base material for corrosion resistance evaluation of the surface-ground abrasive material.

進而，在製作同種鋼、以及與SUS304的異種鋼熔接樣品時，假設於施行TIG熔接時，氣體遮蔽不完全的情況下，前面焊珠側、背面焊珠側均使用Ar+20vol%N₂ 保護氣體施行熔接試驗。Further, when the same type of steel and the dissimilar steel of SUS304 are welded, it is assumed that when the TIG welding is performed, the gas shielding is incomplete, and the front bead side and the back bead side are both protected by Ar+20 vol% N _{2 .} The gas was subjected to a fusion test.

熔接條件係如下述，評價面係設定為背面焊珠面。The welding conditions are as follows, and the evaluation surface is set to the back bead surface.

熔接電壓：10VWelding voltage: 10V

熔接電流：90~110AWelding current: 90~110A

熔接速度：600mm/minWelding speed: 600mm/min

電極：1.6mm鎢電極Electrode: 1.6mm tungsten electrode

保護氣體：前面焊珠側Ar+20vol%N₂ 20L/min背面焊珠側Ar+20vol%N₂ 20L/minProtective gas: front bead side Ar+20vol%N ₂ 20L/min back bead side Ar+20vol%N ₂ 20L/min

使用所獲得母材、同種鋼熔接部、異種鋼熔接部樣品，根據JIS H 8502(1999)施行中性鹽霧循環腐蝕試驗(CCT)。CCT係將5質量%NaCl溶液噴霧(35℃、2h)→乾燥(60℃、4h、相對濕度20~30%)→濕潤(40℃、2h、相對濕度95%以上)設為1循環，合計實施15循環。所獲得結果如表6所示。再者，判定基準係與實施例1同樣。A neutral salt spray cyclic corrosion test (CCT) was carried out in accordance with JIS H 8502 (1999) using the obtained base material, the same type of steel welded portion, and the dissimilar steel welded portion sample. CCT is a 5 mass% NaCl solution spray (35 ° C, 2 h) → dry (60 ° C, 4 h, relative humidity 20 ~ 30%) → wet (40 ° C, 2 h, relative humidity 95% or more) set to 1 cycle, total 15 cycles were implemented. The results obtained are shown in Table 6. Furthermore, the criterion is determined in the same manner as in the first embodiment.

屬於發明例的No.23~28對任一項評價項目均呈現耐蝕性、表面性狀優異。經添加Al、Sb、Zr、V的No.25~28，在與SUS304的異種鋼熔接部處，仍呈現耐蝕性非常優異。No. 23 to 28 belonging to the invention examples were excellent in corrosion resistance and surface properties for any of the evaluation items. No. 25 to 28 in which Al, Sb, Zr, and V were added, and the corrosion resistance of the dissimilar steel welded portion of SUS304 was excellent.

另一方面，屬於比較例的No.29係Cr量為16.7%，因為較低於本發明的範圍，因而生鏽面積較大、耐蝕性差。On the other hand, the amount of No. 29 which is a comparative example is 16.7%, and since it is lower than the range of the present invention, the rust area is large and the corrosion resistance is poor.

又，比較例No.30係Cr量為19.7%，因為較高於本發明的範圍，因而異種鋼熔接部的生鏽面積較大、耐蝕性差。此現象可認為因為係屬於肥粒鐵相生成促進元素的Cr量較高，因而異種鋼熔接部不會麻田散鐵化的原因。Further, in Comparative Example No. 30, the amount of Cr was 19.7%, and since it was higher than the range of the present invention, the dissimilar steel welded portion had a large rust area and poor corrosion resistance. This phenomenon is considered to be because the amount of Cr which is a ferrite-phase iron-phase-promoting element is high, and thus the dissimilar steel welded portion does not cause erection.

又，比較例No.31係Si量為0.36%、Mo量為0.40%，均超越本發明範圍，在母材表面上確認到若干鏽皮殘留，經冷軋退火酸洗後的耐蝕性亦差，且特別係當氣體遮蔽不足時，在與SUS304間之異種鋼熔接部的耐蝕性差。Further, in Comparative Example No. 31, the amount of Si was 0.36%, and the amount of Mo was 0.40%, which exceeded the range of the present invention, and a certain amount of scale remained on the surface of the base material, and the corrosion resistance after pickling by cold rolling annealing was also poor. In particular, when the gas shielding is insufficient, the corrosion resistance of the dissimilar steel welded portion with the SUS 304 is poor.

進而，比較例No.32係Si量為0.50%、Nb量為0.10%，均超過本發明範圍，在母材表面上確認到若干鏽皮殘留，經冷軋退火酸洗後的耐蝕性差。Further, in Comparative Example No. 32, the amount of Si was 0.50%, and the amount of Nb was 0.10%, both of which exceeded the range of the present invention. Some of the scale remained on the surface of the base material, and the corrosion resistance after pickling by cold rolling annealing was inferior.

由以上得知，本發明例係可在未對熱軋退火酸洗板施行研削之前提下，獲得母材耐蝕性、同種鋼熔接部的耐蝕性、以及與SUS304間之異種鋼熔接部的耐蝕性、冷軋退火酸洗板的表面性狀均呈良好的肥粒鐵系不鏽鋼板。From the above, it is known that the present invention can be obtained without performing the grinding on the hot-rolled annealed pickling plate to obtain the corrosion resistance of the base material, the corrosion resistance of the same steel welded portion, and the corrosion resistance of the dissimilar steel welded portion with SUS304. The surface properties of the cold rolled and annealed pickled sheets are all good ferrite iron-based stainless steel sheets.

(產業上之可利用性)(industrial availability)

適宜用為以器物、廚房機器、建築內外建材、施工支架、電梯．自動扶梯內裝材料、家電、汽車零件等為中心之要求耐蝕性的構件。Suitable for use as utensils, kitchen machines, building materials inside and outside, construction brackets, elevators. A member of the escalator interior materials, home appliances, and automobile parts that are required to have corrosion resistance.

Claims

一種肥粒鐵系不鏽鋼，係依質量%計，含有：C：0.003~0.015%、Si：0.05~0.30%、Mn：0.10~0.35%、P：0.06%以下、S：0.02%以下、Cr：17.0~19.0%、Ni：超過0.10%~0.30%、Ti：0.10~0.40%、Nb：0.005%~未滿0.050%、Mo：未滿0.20%、N：0.005~0.015%、Cu：0.30~0.50%、Mg：未滿0.0005%，其餘則由Fe及不可避免的雜質構成。 A ferrite-based iron-based stainless steel containing C: 0.003 to 0.015%, Si: 0.05 to 0.30%, Mn: 0.10 to 0.35%, P: 0.06% or less, S: 0.02% or less, and Cr: 17.0~19.0%, Ni: more than 0.10%~0.30%, Ti: 0.10~0.40%, Nb: 0.005%~ less than 0.050%, Mo: less than 0.20%, N: 0.005~0.015%, Cu: 0.30~0.50 %, Mg: less than 0.0005%, and the rest consists of Fe and unavoidable impurities.

如申請專利範圍第1項之肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Al：0.02~0.50%。 For example, the ferrite-based iron-based stainless steel of the first application of the patent scope includes Al: 0.02 to 0.50% by mass.

如申請專利範圍第2項之肥粒鐵系不鏽鋼，其中，依質量%計含有Al：0.10~0.50%。 For example, the ferrite-based iron-based stainless steel of the second application of the patent scope includes Al: 0.10 to 0.50% by mass%.

如申請專利範圍第1至3項中任一項之肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Sb：0.005~0.300%。 The ferrite-based iron-based stainless steel according to any one of claims 1 to 3, further comprising Sb: 0.005 to 0.300% by mass%.

如申請專利範圍第1至3項中任一項之肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Zr：0.05~0.60%、V：0.02~0.50%中之一種或二種。 The ferrite-based iron-based stainless steel according to any one of claims 1 to 3, further comprising one or two of Zr: 0.05 to 0.60% and V: 0.02 to 0.50% in terms of % by mass.

如申請專利範圍第4項之肥粒鐵系不鏽鋼，其中，更進一步依質量%計含有Zr：0.05~0.60%、V：0.02~0.50%中之一種或二種。 For example, the ferrite-based iron-based stainless steel of the fourth aspect of the patent application includes one or two of Zr: 0.05 to 0.60% and V: 0.02 to 0.50% in terms of % by mass.