JP2021138981A - Austenitic stainless steel sheet having less surface color unevenness, method for manufacturing the same, and exhaust part - Google Patents
Austenitic stainless steel sheet having less surface color unevenness, method for manufacturing the same, and exhaust part Download PDFInfo
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 36
- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims abstract description 29
- 238000000034 method Methods 0.000 title claims abstract description 11
- 238000000137 annealing Methods 0.000 claims abstract description 43
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 32
- 239000010959 steel Substances 0.000 claims abstract description 32
- 238000005097 cold rolling Methods 0.000 claims abstract description 26
- 150000003839 salts Chemical class 0.000 claims abstract description 25
- 230000006866 deterioration Effects 0.000 claims abstract description 17
- 238000005554 pickling Methods 0.000 claims description 23
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- 238000005498 polishing Methods 0.000 abstract description 14
- 229910052751 metal Inorganic materials 0.000 abstract description 5
- 239000002184 metal Substances 0.000 abstract description 5
- 238000000227 grinding Methods 0.000 abstract description 3
- 239000002253 acid Substances 0.000 abstract 3
- 238000004140 cleaning Methods 0.000 abstract 2
- 230000007797 corrosion Effects 0.000 description 42
- 238000005260 corrosion Methods 0.000 description 42
- 239000003921 oil Substances 0.000 description 21
- 238000003466 welding Methods 0.000 description 18
- 230000003647 oxidation Effects 0.000 description 16
- 238000007254 oxidation reaction Methods 0.000 description 16
- 238000007670 refining Methods 0.000 description 11
- 229910001566 austenite Inorganic materials 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 8
- 230000003749 cleanliness Effects 0.000 description 8
- 229910001220 stainless steel Inorganic materials 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 229910052761 rare earth metal Inorganic materials 0.000 description 6
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 5
- 239000010960 cold rolled steel Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 238000005482 strain hardening Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 230000004580 weight loss Effects 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 239000010731 rolling oil Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 238000007517 polishing process Methods 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000012459 cleaning agent Substances 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000005413 snowmelt Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
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Abstract
Description
本発明は、耐熱部品用素材の中でも高Ｓｉ含有であるオーステナイト系ステンレス鋼板に関するものであり、特に、自動車のフレキシブルチューブ、耐熱ばね、ガスケット、温水器等の熱交換機能を有する部品に適用されるものである。またそれらの中でも溶接を必要とする部品に適する材料に関するものである。 The present invention relates to an austenitic stainless steel sheet containing a high amount of Si among materials for heat-resistant parts, and is particularly applied to parts having a heat exchange function such as flexible tubes of automobiles, heat-resistant springs, gaskets, and water heaters. It is a thing. Also, among them, it relates to a material suitable for a part requiring welding.
自動車の各種排気部品には高温の排気ガスを安定的に通気させるために、耐酸化性、高温強度、熱疲労特性等の耐熱性に優れた材料が使用される。また、車体の振動に起因して繰り返し荷重が作用するため、高サイクル疲労特性も重要となる。このような疲労劣化を緩和する目的として自動車にはフレキシブルチューブが多く搭載されている。更に、凝縮水腐食環境および路上の融雪塩からの高温塩害腐食環境でもあることから耐食性に優れることも要求される。排気ガス規制の強化、エンジン性能の向上、車体軽量化等の観点からもこれらの部品にはステンレス鋼が多く使用されている。 Materials with excellent heat resistance such as oxidation resistance, high temperature strength, and thermal fatigue characteristics are used for various exhaust parts of automobiles in order to stably ventilate high temperature exhaust gas. In addition, high cycle fatigue characteristics are also important because repeated loads act due to the vibration of the vehicle body. Many flexible tubes are installed in automobiles for the purpose of alleviating such fatigue deterioration. Further, it is also required to have excellent corrosion resistance because it is also a condensate water corrosion environment and a high temperature salt damage corrosion environment from snowmelt salt on the road. Stainless steel is often used for these parts from the viewpoints of tightening exhaust gas regulations, improving engine performance, and reducing the weight of the vehicle body.
高温塩害腐食環境での耐食性に優れたステンレス鋼は特許文献１〜４に開示されている。いずれも高温塩害腐食の耐食性（以下、高温塩害腐食の耐食性を「耐高温塩害性」ともいう。）の向上に有効な高Ｓｉ、高Ｍｏ含有オーステナイト系ステンレス鋼である。特に特許文献２および４は溶接高温割れ感受性を考慮した成分範囲を規定している。 Stainless steels having excellent corrosion resistance in a high-temperature salt-damaged corrosive environment are disclosed in Patent Documents 1 to 4. Both are high Si and high Mo-containing austenitic stainless steels that are effective in improving the corrosion resistance of high-temperature salt damage corrosion (hereinafter, the corrosion resistance of high temperature salt damage corrosion is also referred to as "high temperature salt damage resistance"). In particular, Patent Documents 2 and 4 define a component range in consideration of welding high temperature cracking susceptibility.
高Ｓｉ含有ステンレス鋼は、焼鈍によってＳｉの酸化スケールが形成されるため、低Ｓｉ含有ステンレス鋼と比較して酸洗性が悪く、酸洗液の高濃度化や酸洗時間の延長化等の対策が必要であり、これらは製造コストの増加につながる。また、酸洗条件によっては表面が白色化して見える色ムラ（以下、「表面色ムラ」ともいう。）が生じ溶接する際に溶接金属の溶け落ちを引き起こす場合がある。これは白色部に存在するＳｉ酸化物が溶接中に溶融池の酸素濃度上昇を引き起こして対流が変化するためと考えられるが、詳細は不明である。 High-Si-containing stainless steel has poor pickling properties compared to low-Si-containing stainless steel because the oxidation scale of Si is formed by annealing. Measures are needed, which leads to increased manufacturing costs. Further, depending on the pickling conditions, color unevenness (hereinafter, also referred to as “surface color unevenness”) in which the surface appears to be whitened may occur, causing the weld metal to melt off during welding. It is considered that this is because the Si oxide present in the white part causes an increase in the oxygen concentration in the molten pool during welding and the convection changes, but the details are unknown.
特許文献１には２〜１０％Ｓｉ、特許文献２には１〜４％Ｓｉ、特許文献３には２％超〜６％Ｓｉ、特許文献４には２〜４％Ｓｉの成分を有するオーステナイト系ステンレス鋼が開示されている。しかし、いずれにも溶接溶け落ち性についての記載は無く、その製造方法については不明である。 Patent Document 1 contains 2 to 10% Si, Patent Document 2 contains 1 to 4% Si, Patent Document 3 contains more than 2% to 6% Si, and Patent Document 4 contains 2 to 4% Si. Austenitic stainless steel is disclosed. However, there is no description about weld melt-through property in any of them, and its manufacturing method is unknown.
薄い鋼板を製造するためには、通常、冷間圧延−焼鈍・酸洗が複数回実施される。表面色ムラを低減する製造方法として、（ｎ−１）回目までの各冷間圧延（以下、中間冷延ともいう。）−焼鈍・酸洗後に表面研削／研磨（以下、この表面研削／研磨を「中間研磨」ともいう。）し、最終冷延−焼鈍・酸洗する方法が適用されている。中間研磨を施すと研磨ムラが生じることがあり、研磨ムラは表面凹凸起因で加熱時の酸化が促進されて耐高温塩害性を劣化させる。また、工業的な生産をする場合は生産効率向上を狙い工程数を減らすことが望ましい。
In order to produce a thin steel sheet, cold rolling-annealing / pickling is usually performed a plurality of times. As a manufacturing method for reducing surface color unevenness, each cold rolling up to (n-1) times (hereinafter, also referred to as intermediate cold rolling) -surface grinding / polishing after annealing and pickling (hereinafter, this surface grinding / polishing). Is also referred to as "intermediate polishing"), and the final cold rolling-annealing / pickling method is applied. When intermediate polishing is applied, uneven polishing may occur, and the uneven polishing promotes oxidation during heating due to surface irregularities and deteriorates high-temperature salt damage resistance. In addition, in the case of industrial production, it is desirable to reduce the number of processes with the aim of improving production efficiency.
本願の発明が解決しようする課題は、中間冷延−焼鈍・酸洗後の中間研磨工程を省略した場合であっても、表面色ムラを低減できる高Ｓｉ含有オーステナイト系ステンレス鋼板の製造方法を提供することと、その製造方法により製造される、表面色ムラに関連する溶接金属の溶け落ちが抑制され、耐高温塩害性の劣化が抑制される高Ｓｉ含有オーステナイト系ステンレス鋼板を提供することと、その鋼板を溶接した構造を有する部品を提供することにある。 The problem to be solved by the invention of the present application is to provide a method for producing a high Si-containing austenitic stainless steel plate that can reduce surface color unevenness even when the intermediate polishing step after intermediate cold spreading-baking / pickling is omitted. To provide a high-Si-containing austenitic stainless steel sheet produced by the manufacturing method, which suppresses the melt-through of the weld metal related to surface color unevenness and suppresses the deterioration of high-temperature salt damage resistance. It is an object of the present invention to provide a part having a structure in which the steel plate is welded.
高Ｓｉ含有鋼において中間冷延−焼鈍・酸洗後の中間研磨工程を省略した場合に表面色ムラが発生するという問題を解決するために、製造方法に関して、特に冷延ロール（本願明細書において、「ロール」は、特に断りがない限り「ワークロール」を意味する。）および焼鈍スケール形成の見地から詳細な研究を行った。その結果、低粗度の中間冷延ロールを使用して得る高平滑な冷延鋼板は、相対的に表面積が小さいため、中間研磨により除去していたＳｉ酸化スケールの形成が少なくなり、表面色ムラが低減し、溶接金属の溶け落ちが抑制され、耐高温塩害性の劣化が抑制され、また、焼鈍前の油付着量が少なくなり、酸洗性が向上し、油由来の着色ムラも低減することを知見した。 In order to solve the problem that surface color unevenness occurs when the intermediate cold-rolling-annealing / pickling intermediate polishing step is omitted in high Si-containing steel, the manufacturing method is particularly cold-rolled (in the specification of the present application). , "Roll" means "work roll" unless otherwise noted.) And detailed studies were conducted from the standpoint of annealing scale formation. As a result, the highly smooth cold-rolled steel sheet obtained by using a low-roughness intermediate cold-rolled steel sheet has a relatively small surface area, so that the formation of Si oxide scale removed by intermediate polishing is reduced, and the surface color is reduced. Unevenness is reduced, welding metal is suppressed from melting off, deterioration of high temperature salt damage resistance is suppressed, oil adhesion before annealing is reduced, pickling property is improved, and oil-derived coloring unevenness is also reduced. I found out that
本発明の要旨は、次のとおりである。
（１）
質量％で、Ｓｉ：０．５〜４．０％含有するオーステナイト系ステンレス鋼であって、
酸洗された冷延焼鈍鋼板における表面の色差指標L*の最大値と最小値の差ΔL*がΔL*≦０．５０であり、耐高温塩害性の劣化が抑制されることを特徴とするオーステナイト系ステンレス鋼板。
（２）
質量％で、
Ｃ：０．００２〜０．３％、
Ｓｉ：０．５〜４．０％、
Ｍｎ：０．０５〜１０．０％、
Ｐ：０．００１〜０．０５％、
Ｓ：０．０００１〜０．０１％、
Ｎｉ：２〜２５％、
Ｃｒ：１５〜３０％、
Ｎ：０．００２〜０．５％、
Ａｌ：０．００１〜１．０％、
Ｃｕ：０．１〜４．０％、
Ｍｏ：０．０１〜３．０％、
Ｖ：０．０１〜１．０％、
を含有し、残部がＦｅ及び不可避的不純物からなる前記（１）に記載のオーステナイト系ステンレス鋼板。
（３）
さらに、質量％で
Ｎｂ：０．３％以下、
Ｔｉ：０．３％以下、
Ｂ：０．００６０％以下、
Ｃａ：０．０１％以下、
Ｗ：３．０％以下、
Ｚｒ：０．３％以下、
Ｓｎ：０．５％以下、
Ｃｏ：０．３％以下、
Ｍｇ：０．０１％以下、
Ｓｂ：０．５％以下、
ＲＥＭ：０．２％以下、
Ｇａ：０．３％以下、
Ｔａ：１．０％以下、
Ｈｆ：１．０％以下、
から選択される１種または２種以上を含有することを特徴とする前記（２）に記載のオーステナイト系ステンレス鋼板。
（４）
冷間圧延、焼鈍、酸洗をｎ回実施する鋼鈑の製造方法（ただし、ｎは２以上の自然数）において、（ｎ−１）回目までの各冷間圧延の仕上げ冷延に使用するロール粗度をＲａ≦０．５μｍとすることを特徴とする、前記（１）〜（３）のいずれかに記載のオーステナイト系ステンレス鋼板の製造方法。
（５）
前記（４）に記載のオーステナイト系ステンレス鋼板の製造方法であって、中間冷延後焼鈍前（（ｎ−１）回目までの各冷延後焼鈍前）の鋼板表面の油付着量が２００ｍｍ２あたり１５０ｍｇ以下であることを特徴とする前記（１）〜（３）のいずれかに記載のオーステナイト系ステンレス鋼板の製造方法。
（６）
前記（１）〜（３）のいずれかに記載のオーステナイト系ステンレス鋼板の溶接構造体である排気部品。
ここで、色差指標L*の最大値と最小値の差ΔL*は、L*が色空間の明度に相当するから、その差ΔL*が一定値以下と特定することは、明度の差が一定の範囲内にあること、すなわち、着目する表面色ムラが一定値以下と少ないことを意味する。また、「耐高温塩害性の劣化が抑制される」とは、４０ｍｍ(長さ)×２０ｍｍ（幅）×０．６ｍｍ（厚さ）の寸法を有するサンプルの端面を＃６００で湿式研磨した後、７００℃で１１０分間加熱し、室温で２０分間冷却し、５％ＮａＣｌ溶液に２０分間全浸漬し、５０℃で２５分間乾燥することを６０サイクル繰り返し、その後、そのサンプル表面に付着した腐食生成物を除去して、腐食減量（＝試験前のサンプル重量―試験後のサンプル重量）を求めたときに、腐食減量が５０ｍｇ／ｃｍ２以下であることを意味する。
The gist of the present invention is as follows.
(1)
An austenitic stainless steel containing 0.5 to 4.0% of Si in mass%.
The difference ΔL * between the maximum value and the minimum value of the surface color difference index L * of the pickled cold-rolled annealed steel sheet is ΔL * ≦ 0.50, and the deterioration of high-temperature salt damage resistance is suppressed. Austenitic stainless steel plate.
(2)
By mass%
C: 0.002-0.3%,
Si: 0.5-4.0%,
Mn: 0.05 to 10.0%,
P: 0.001 to 0.05%,
S: 0.0001 to 0.01%,
Ni: 2-25%,
Cr: 15-30%,
N: 0.002-0.5%,
Al: 0.001 to 1.0%,
Cu: 0.1-4.0%,
Mo: 0.01-3.0%,
V: 0.01-1.0%,
The austenitic stainless steel sheet according to (1) above, which contains the above-mentioned (1) and the balance is composed of Fe and unavoidable impurities.
(3)
Furthermore, in mass%, Nb: 0.3% or less,
Ti: 0.3% or less,
B: 0.0060% or less,
Ca: 0.01% or less,
W: 3.0% or less,
Zr: 0.3% or less,
Sn: 0.5% or less,
Co: 0.3% or less,
Mg: 0.01% or less,
Sb: 0.5% or less,
REM: 0.2% or less,
Ga: 0.3% or less,
Ta: 1.0% or less,
Hf: 1.0% or less,
The austenitic stainless steel sheet according to (2) above, which contains one or more selected from the above.
(4)
In a method for manufacturing a steel sheet in which cold rolling, annealing, and pickling are performed n times (however, n is a natural number of 2 or more), a roll used for finishing cold rolling of each cold rolling up to (n-1) times. The method for producing an austenitic stainless steel sheet according to any one of (1) to (3) above, wherein the roughness is Ra ≦ 0.5 μm.
(5)
In the method for producing an austenitic stainless steel sheet according to (4) above, the amount of oil adhered to the surface of the steel sheet after intermediate cold stretching and before annealing (before each cold rolling and annealing up to (n-1) times) is 200 mm 2. The method for producing an austenitic stainless steel sheet according to any one of (1) to (3) above, wherein the amount is 150 mg or less per amount.
(6)
An exhaust component that is a welded structure of an austenitic stainless steel plate according to any one of (1) to (3) above.
Here, since L * corresponds to the brightness of the color space in the difference ΔL * between the maximum value and the minimum value of the color difference index L *, specifying that the difference ΔL * is less than a certain value means that the difference in brightness is constant. That is, it means that the surface color unevenness of interest is as small as a certain value or less. Further, "deterioration of high temperature salt damage resistance is suppressed" means that after wet polishing the end face of a sample having dimensions of 40 mm (length) x 20 mm (width) x 0.6 mm (thickness) with # 600. , 700 ° C. for 110 minutes, room temperature for 20 minutes, full immersion in 5% NaCl solution for 20 minutes, drying at 50 ° C. for 25 minutes for 60 cycles, followed by corrosion formation adhering to the sample surface. It means that the corrosion weight loss is 50 mg / cm 2 or less when the substance is removed and the corrosion weight loss (= sample weight before the test-sample weight after the test) is obtained.
本発明によれば、低粗度の中間冷延ロールを使用することにより、中間研磨工程を省略した場合であっても、高Ｓｉ含有鋼において冷延鋼板表面を平滑にすることで焼鈍前の油付着量を少なくして焼鈍スケールの厚さおよびＳｉ濃度を低減し表面色ムラを低減したオーステナイト系ステンレス鋼板を提供することが出来る。また、この冷延鋼板は、表面色ムラが低減されるのみならず、溶接金属の溶け落ちが抑制され、耐高温塩害性の劣化が抑制される。 According to the present invention, by using a low-roughness intermediate cold-rolled roll, even when the intermediate polishing step is omitted, the surface of the cold-rolled steel sheet is smoothed in the high Si-containing steel before annealing. It is possible to provide an austenite-based stainless steel sheet in which the amount of oil adhered is reduced, the thickness of the annealing scale and the Si concentration are reduced, and the surface color unevenness is reduced. Further, this cold-rolled steel sheet not only reduces surface color unevenness, but also suppresses melt-through of the weld metal and suppresses deterioration of high-temperature salt damage resistance.
［成分］
次に、成分範囲について説明する。成分含有量に関する％は、特に断りの無い限り質量％を示す。
[component]
Next, the component range will be described. Percentage of component content indicates mass% unless otherwise specified.
Ｃはオーステナイト組織形成および高温強度確保のために０．００２％を下限とする。一方、過度な含有は加工硬化が過大に大きくなる他、Ｃｒ炭化物形成により耐食性、特に溶接部の粒界腐食性が劣化するため上限を０．３％とする。更に、熱間加工性を考慮するとＣの含有量の下限は０．００５％、上限は０．２５％であることが望ましい。更に精錬コスト、耐酸化性を考慮すると下限は０．０１％，上限は０．１５％であることが望ましい。 C has a lower limit of 0.002% for forming an austenite structure and ensuring high-temperature strength. On the other hand, if the content is excessive, work hardening becomes excessively large, and corrosion resistance, particularly intergranular corrosion corrosion of the welded portion, deteriorates due to Cr carbide formation, so the upper limit is set to 0.3%. Further, considering the hot workability, it is desirable that the lower limit of the C content is 0.005% and the upper limit is 0.25%. Further, considering the refining cost and oxidation resistance, it is desirable that the lower limit is 0.01% and the upper limit is 0.15%.
Ｓｉは脱酸元素として含有される場合がある他、Ｓｉの酸化によりスケール剥離性、高温強度および耐高温塩害性の向上に寄与する元素である。そのため下限を０．５％とする。一方、加工硬化による過度な硬質化を避けるため上限を４．０％とした。更に、加工硬化特性や溶接性を考慮し、更に、耐高温塩害性や高温強度、耐酸化性を考慮すると、Ｓｉの下限は１．０％、更には１．５％にすることが望ましく、Ｓｉの上限は３．５％、更に熱間加工性を考慮すると３．０％にすることが望ましい。 Si may be contained as a deoxidizing element, and is an element that contributes to improvement of scale peeling property, high temperature strength and high temperature salt damage resistance by oxidation of Si. Therefore, the lower limit is set to 0.5%. On the other hand, the upper limit was set to 4.0% in order to avoid excessive hardening due to work hardening. Further, considering work hardening characteristics and weldability, and further considering high temperature salt damage resistance, high temperature strength, and oxidation resistance, it is desirable that the lower limit of Si is 1.0%, further 1.5%. The upper limit of Si is 3.5%, and it is desirable to set it to 3.0% in consideration of hot workability.
Ｍｎは脱酸元素として利用する他、オーステナイト組織形成およびスケール密着性を確保するために０．０５％以上含有する。一方、１０．０％超の含有によりＭｎＳ等の生成によって介在物清浄度が悪くなり、疲労強度と耐食性が著しく低下するため上限を１０．０％とする。更に、製造コストを考慮するとＭｎ含有量の下限は０．１％が望ましい。更にスケール密着性、加工硬化性を考慮するとＭｎ含有量の上限は５．０％が望ましい。更に、下限は０．５％、上限は１．５％が望ましい。 In addition to being used as a deoxidizing element, Mn is contained in an amount of 0.05% or more in order to ensure austenite structure formation and scale adhesion. On the other hand, if the content exceeds 10.0%, the cleanliness of inclusions deteriorates due to the formation of MnS and the like, and the fatigue strength and corrosion resistance are significantly reduced. Therefore, the upper limit is set to 10.0%. Further, considering the production cost, the lower limit of the Mn content is preferably 0.1%. Further, considering the scale adhesion and work hardening property, the upper limit of the Mn content is preferably 5.0%. Further, the lower limit is preferably 0.5% and the upper limit is preferably 1.5%.
Ｐは製造時の熱間加工性や凝固割れを助長する元素である。また、Ｐ化合物が生成すると疲労起点となり疲労強度が低下するため、上限を０．０５％とする。一方、過度な低減は精錬コストの増加を招くため下限を０．００１％とすることができる。さらに製造コストを考慮すると、Ｐ含有量の上限は０．０４％、下限は０．０１％とすることが望ましい。 P is an element that promotes hot workability and solidification cracking during manufacturing. Further, when the P compound is produced, it becomes a fatigue starting point and the fatigue strength decreases, so the upper limit is set to 0.05%. On the other hand, the lower limit can be set to 0.001% because excessive reduction causes an increase in refining cost. Further, considering the manufacturing cost, it is desirable that the upper limit of the P content is 0.04% and the lower limit is 0.01%.
Ｓは製造時の熱間加工を低下させるほか、耐食性を劣化させる元素である。また、粗大な硫化物（ＭｎＳ）が形成されると介在物清浄度が著しく悪化するため、上限を０．０１とする。一方、過度な低減は精錬コストの増加に繋がることから、下限を０．０００１％とすることができる。更に、製造コストや耐酸化性を考慮すると、Ｓ含有量の上限は０．００５０％、下限は０．０００３％にすることが望ましい。更に上限は０．００２０％、下限は０．０００５％にすることが望ましい。 S is an element that not only reduces hot working during manufacturing but also deteriorates corrosion resistance. Further, since the cleanliness of inclusions is remarkably deteriorated when coarse sulfide (MnS) is formed, the upper limit is set to 0.01. On the other hand, since excessive reduction leads to an increase in refining cost, the lower limit can be set to 0.0001%. Further, considering the manufacturing cost and oxidation resistance, it is desirable that the upper limit of the S content is 0.0050% and the lower limit is 0.0003%. Further, it is desirable that the upper limit is 0.0020% and the lower limit is 0.0005%.
Ｎｉはオーステナイト組織形成元素であるとともに、耐食性や耐酸化性を確保する元素である。また、２％未満ではオーステナイト組織の安定度が低下して高温強度が低下する他、結晶粒の粗大化が顕著に生じてしまうため、２％以上含有する。一方、過度な含有はコスト上昇と硬質化を招くことから上限を２５％とする。更に、製造性、高温強度および耐食性を考慮すると、Ｎｉ含有量の下限は５％、上限は１５％にすることが望ましい。更に、下限は８％、上限は１２％にすることが望ましい。 Ni is an austenite structure-forming element and an element that ensures corrosion resistance and oxidation resistance. Further, if it is less than 2%, the stability of the austenite structure is lowered, the high temperature strength is lowered, and the coarsening of crystal grains is remarkably caused, so that the content is 2% or more. On the other hand, the upper limit is set to 25% because excessive content causes cost increase and hardening. Further, in consideration of manufacturability, high temperature strength and corrosion resistance, it is desirable that the lower limit of the Ni content is 5% and the upper limit is 15%. Further, it is desirable that the lower limit is 8% and the upper limit is 12%.
Ｃｒは耐食性、耐酸化性を向上させる必須元素である。１５％未満の含有では排気ガスによる異常酸化やスケール剥離が生じて高温強度が著しく低下するため１５％以上の含有が必要である。一方、過度な含有は、硬質となる他、コストアップに繋がることから上限を３０％とする。更に製造コスト、鋼板製造性、加工性を考慮すると、Ｃｒ含有量の下限は１６％、上限は２５％にすることが望ましい。更に、下限は１７％、上限は２４％にすることが望ましい。 Cr is an essential element that improves corrosion resistance and oxidation resistance. If the content is less than 15%, abnormal oxidation due to exhaust gas and scale peeling occur, and the high temperature strength is remarkably lowered. Therefore, the content of 15% or more is required. On the other hand, if the content is excessive, the upper limit is set to 30% because it becomes hard and leads to cost increase. Further, considering the manufacturing cost, steel sheet manufacturability, and workability, it is desirable that the lower limit of the Cr content is 16% and the upper limit is 25%. Further, it is desirable that the lower limit is 17% and the upper limit is 24%.
ＮはＣと同様にオーステナイト組織形成、高温強度の確保に有効な元素である。そのため下限を０．００２％とする。一方、０．５％超の含有により常温材質が著しく硬質化し、鋼板製造段階の冷間加工性が悪くなる他、パイプなどの部品製造性が悪くなるため上限を０．５％とする。更に、精錬コスト、溶接時のピンホール抑制、溶接部の粒界腐食抑制の観点から、Ｎ含有量の下限は０．０１％、上限は０．３５％にすることが望ましい。更に、下限は０．０４％、上限は０．２３％にすることが望ましい。 Like C, N is an element effective for forming an austenite structure and ensuring high-temperature strength. Therefore, the lower limit is set to 0.002%. On the other hand, if the content exceeds 0.5%, the normal temperature material becomes extremely hard, the cold workability at the steel sheet manufacturing stage deteriorates, and the manufacturability of parts such as pipes deteriorates, so the upper limit is set to 0.5%. Further, from the viewpoint of refining cost, suppression of pinholes during welding, and suppression of intergranular corrosion of welded parts, it is desirable that the lower limit of the N content is 0.01% and the upper limit is 0.35%. Further, it is desirable that the lower limit is 0.04% and the upper limit is 0.23%.
Ａｌは、脱酸元素として含有し、介在物清浄度を良くするため０．００１％以上含有する。一方、過度の含有は熱間加工性の悪化、酸洗性の低下による表面疵の発生を起こりやすくするためＡｌ含有量の上限は１．０％に規定する。また、製造性やスケール密着性の観点から、下限は０．０１％、上限は０．２％が望ましい。更に、上限は０．２０％が望ましい。 Al is contained as a deoxidizing element, and is contained in an amount of 0.001% or more in order to improve the cleanliness of inclusions. On the other hand, the upper limit of the Al content is set to 1.0% because excessive content tends to cause surface defects due to deterioration of hot workability and deterioration of pickling property. Further, from the viewpoint of manufacturability and scale adhesion, the lower limit is preferably 0.01% and the upper limit is preferably 0.2%. Further, the upper limit is preferably 0.20%.
Ｃｕはオーステナイト組織安定化や耐酸化性向上および耐ＳＣＣ性向上に有効な元素であるため、０．１％以上含有する。一方、過度な含有は耐酸化性の劣化や製造性の悪化に繋がるため上限を４．０％とする。更に、耐食性や製造性を考慮すると、Ｃｕ含有量の下限は０．１５％、上限は２．０％にすることが望ましい。更に、下限は０．２％、上限は１．８％にすることが望ましい。 Since Cu is an element effective for stabilizing the austenite structure, improving the oxidation resistance and improving the SCC resistance, it is contained in an amount of 0.1% or more. On the other hand, excessive content leads to deterioration of oxidation resistance and manufacturability, so the upper limit is set to 4.0%. Further, in consideration of corrosion resistance and manufacturability, it is desirable that the lower limit of the Cu content is 0.15% and the upper limit is 2.0%. Further, it is desirable that the lower limit is 0.2% and the upper limit is 1.8%.
Ｍｏは耐高温塩害性を向上させる元素であるとともに、高温強度の向上に寄与する元素である。そのため下限を０．０１％とする。一方、Ｍｏは高価な元素であるとともに過度な含有は耐酸化性や製造性を劣化させるため、上限を３．０％とする。また、高温強度や熱疲労特性を考慮すると下限は０．５％、製造性やコストを考慮すると上限は１．８％が望ましい。更に、耐高温塩害性や耐食性、熱間加工性を考慮すると０．６〜１．５％が望ましい。 Mo is an element that improves high-temperature salt damage resistance and also contributes to the improvement of high-temperature strength. Therefore, the lower limit is set to 0.01%. On the other hand, Mo is an expensive element and excessive content deteriorates oxidation resistance and manufacturability, so the upper limit is set to 3.0%. Further, the lower limit is preferably 0.5% in consideration of high temperature strength and thermal fatigue characteristics, and the upper limit is preferably 1.8% in consideration of manufacturability and cost. Further, considering high temperature salt damage resistance, corrosion resistance, and hot workability, 0.6 to 1.5% is desirable.
Ｖは耐食性を向上させる元素であるとともに、Ｖ炭化物を形成し高温強度を向上させるため０．０１％以上含有する。一方、過度な含有は合金コストの増加や異常酸化限界温度の低下を招くことから、上限を１．０％とする。更に、製造性や介在物清浄度を考慮するとＶ含有量の下限は０．０５％、上限は０．８％にすることが望ましい。更に下限は０．０９％、上限は０．５％にすることが好ましい。 V is an element that improves corrosion resistance, and is contained in an amount of 0.01% or more in order to form V carbides and improve high-temperature strength. On the other hand, since excessive content causes an increase in alloy cost and a decrease in abnormal oxidation limit temperature, the upper limit is set to 1.0%. Further, in consideration of manufacturability and cleanliness of inclusions, it is desirable that the lower limit of the V content is 0.05% and the upper limit is 0.8%. Further, the lower limit is preferably 0.09% and the upper limit is preferably 0.5%.
以上が、主要元素であるが、その他Ｆｅの一部の代替として以下の元素の１種または２種以上を含有することができる。 The above are the main elements, but one or more of the following elements can be contained as a substitute for a part of Fe.
Ｎｂは、Ｃ、Ｎと結合して耐食性、耐粒界腐食性を向上させる他、高温強度向上させる元素である。Ｃ、Ｎ固定作用は０．００５％から発現するため、下限を０．００５％とした。また、０．３％超の含有は、鋼板製造段階での熱間加工性が著しく劣化することから、上限を０．３％とする。更に、高温強度、溶接部の粒界腐食性および合金コストを考慮すると、Ｎｂ含有量の下限は０．０１％、上限は０．１５％未満にすることが望ましい。加えて、Ｎｂは再結晶を鈍化させる元素である。十分な高温疲労強度を得るとともに結晶粒径の調整を短時間で完了させる必要があるため、Ｎｂ含有量の上限は０．０５％未満にすることが望ましい。 Nb is an element that combines with C and N to improve corrosion resistance and intergranular corrosion resistance, as well as to improve high-temperature strength. Since the C and N fixing action is expressed from 0.005%, the lower limit is set to 0.005%. Further, if the content exceeds 0.3%, the hot workability at the steel sheet manufacturing stage is significantly deteriorated, so the upper limit is set to 0.3%. Further, considering the high temperature strength, intergranular corrosion corrosion of the welded portion, and alloy cost, it is desirable that the lower limit of the Nb content is 0.01% and the upper limit is less than 0.15%. In addition, Nb is an element that slows recrystallization. It is desirable that the upper limit of the Nb content is less than 0.05% because it is necessary to obtain sufficient high-temperature fatigue strength and complete the adjustment of the crystal particle size in a short time.
Ｔｉは、Ｎｂと同様にＣ、Ｎと結合して耐食性、耐粒界腐食性を向上させるために含有する元素である。Ｃ、Ｎ固定作用は０．００５％から発現するため、下限を０．００５％とした。また、０．３％超の含有は鋳造段階でのノズル詰まりが生じ易くなり、製造性を著しく劣化させることから、上限を０．３％とする。更に、高温強度、溶接部の粒界腐食性および合金コストを考慮すると、Ｔｉ含有量の下限は０．０１％、上限は０．１％にすることが望ましい。 Like Nb, Ti is an element contained in order to combine with C and N to improve corrosion resistance and intergranular corrosion resistance. Since the C and N fixing action is expressed from 0.005%, the lower limit is set to 0.005%. Further, if the content exceeds 0.3%, nozzle clogging at the casting stage is likely to occur and the manufacturability is significantly deteriorated. Therefore, the upper limit is set to 0.3%. Further, considering the high temperature strength, intergranular corrosion corrosion of the welded portion, and alloy cost, it is desirable that the lower limit of the Ti content is 0.01% and the upper limit is 0.1%.
Ｂは、鋼板製造段階での熱間加工性を向上させる元素であるとともに、常温での加工硬化を抑制する効果があるため、０．０００２％以上とする。０．０００６％以上でより効果的である。但し、過度な含有はホウ炭化物の形成により清浄度の低下、粒界腐食性の劣化をもたらすため、上限を０．００６０％とした。更に、精錬コストや延性低下を考慮すると、Ｂ含有量の下限は０．００１６％、上限は０．００２０％にすることが望ましい。 B is an element that improves hot workability at the steel sheet manufacturing stage and has an effect of suppressing work hardening at room temperature, so it is set to 0.0002% or more. More effective at 0.0006% or higher. However, since excessive content causes a decrease in cleanliness and deterioration of intergranular corrosion due to the formation of boring carbide, the upper limit is set to 0.0060%. Further, considering the refining cost and the decrease in ductility, it is desirable that the lower limit of the B content is 0.0016% and the upper limit is 0.0020%.
Ｃａは、脱硫のために必要に応じて含有される他、介在物の清浄度を向上させて疲労強度が向上する。この作用は０．０００５％未満では発現しないため、下限を０．０００５％とする。また、０．０１％超含有すると水溶性の介在物ＣａＳが生成して清浄度の低下および耐食性の著しい低下を招くため、上限を０．０１％とする。更に、製造性、表面品質の観点から、Ｃａ含有量の下限は０．００４０％、上限は０．００３０％にすることが望ましい。 Ca is contained as needed for desulfurization, and also improves the cleanliness of inclusions to improve fatigue strength. Since this effect does not occur below 0.0005%, the lower limit is set to 0.0005%. Further, if the content exceeds 0.01%, water-soluble inclusions CaS are generated, which causes a decrease in cleanliness and a significant decrease in corrosion resistance. Therefore, the upper limit is set to 0.01%. Further, from the viewpoint of manufacturability and surface quality, it is desirable that the lower limit of the Ca content is 0.0040% and the upper limit is 0.0030%.
Ｗは、耐食性と高温強度の向上に寄与する他、Ｍｏと同様に疲労強度向上に寄与するため、必要に応じて０．０３％以上含有する。３％超の含有により硬質化、鋼板製造時の靭性劣化やコスト増につながるため、上限を３％とする。更に、精錬コストや製造性を考慮すると、Ｗ含有量の下限は０．０５％、上限は２％にすることが望ましい。 W contributes to the improvement of corrosion resistance and high temperature strength, and also contributes to the improvement of fatigue strength like Mo. Therefore, W is contained in an amount of 0.03% or more as necessary. The upper limit is set to 3% because the content of more than 3% leads to hardening, deterioration of toughness during steel sheet manufacturing, and cost increase. Further, considering the refining cost and manufacturability, it is desirable that the lower limit of the W content is 0.05% and the upper limit is 2%.
Ｚｒは、ＣやＮと結合して溶接部の粒界腐食性や耐酸化性を向上させるため、必要に応じて０．００２％以上含有する。但し、０．３％超の含有によりコスト増になる他、製造性を著しく劣化させるため、上限を０．３％とする。更に、精錬コストや製造性を考慮すると、Ｚｒ含有量の下限は０．０５％、上限は０．１％にすることが望ましい。 Zr is contained in an amount of 0.002% or more, if necessary, in order to combine with C and N to improve intergranular corrosion resistance and oxidation resistance of the welded portion. However, the upper limit is set to 0.3% because the content of more than 0.3% increases the cost and significantly deteriorates the manufacturability. Further, considering the refining cost and manufacturability, it is desirable that the lower limit of the Zr content is 0.05% and the upper limit is 0.1%.
Ｓｎは、耐食性と高温強度の向上に寄与するため、必要に応じて０．００８以上含有する。０．０１％以上で効果が顕著になる。０．０５％以上としても良い。０．５％超の含有により鋼板製造時のスラブ割れが生じる場合があるため上限を０．５％とする。更に、精錬コストや製造性を考慮すると、上限は０．３％にすることが望ましい。０．２％以下としても良い。 Sn is contained in an amount of 0.008 or more, if necessary, in order to contribute to the improvement of corrosion resistance and high temperature strength. The effect becomes remarkable at 0.01% or more. It may be 0.05% or more. If the content exceeds 0.5%, slab cracking may occur during steel sheet manufacturing, so the upper limit is set to 0.5%. Further, considering the refining cost and manufacturability, it is desirable that the upper limit is 0.3%. It may be 0.2% or less.
Ｃｏは、高温強度の向上に寄与するため、必要に応じて０．０３％以上含有する。０．３％超の含有により、硬質化、鋼板製造時の靭性劣化やコスト増につながるため、上限を０．３％とする。更に、精錬コストや製造性を考慮すると、Ｃｏ含有量の下限は０．０５％、上限は０．１％にすることが望ましい。 Co is contained in an amount of 0.03% or more, if necessary, in order to contribute to the improvement of high temperature strength. If the content exceeds 0.3%, it will lead to hardening, deterioration of toughness during steel sheet manufacturing, and cost increase, so the upper limit is set to 0.3%. Further, considering the refining cost and manufacturability, it is desirable that the lower limit of the Co content is 0.05% and the upper limit is 0.1%.
Ｍｇは、脱酸元素として含有させる場合がある他、スラブの組織を酸化物の微細化分散化により介在物清浄度の向上や組織微細化に寄与する元素である。これは、０．０００２％以上から発現するため、下限を０．０００２％とした。但し、過度な含有は、溶接性や耐食性の劣化、粗大介在物による部品加工性の低下につながるため、上限を０．０１％とした。精錬コストを考慮すると、Ｍｇ含有量の下限は０．０００３％、上限は０．００５％にすることが望ましい。 Mg may be contained as a deoxidizing element, and is an element that contributes to the improvement of inclusion cleanliness and the microstructure of the slab by finely dispersing the oxide. Since this is expressed from 0.0002% or more, the lower limit is set to 0.0002%. However, since excessive content leads to deterioration of weldability and corrosion resistance, and deterioration of parts workability due to coarse inclusions, the upper limit is set to 0.01%. Considering the refining cost, it is desirable that the lower limit of the Mg content is 0.0003% and the upper limit is 0.005%.
Ｓｂは、粒界に偏析して高温強度を上げる作用をなす元素である。含有効果を得るため、０．００２％以上とする。但し、０．５％を超えると、Ｓｂ偏析が生じて、溶接時に割れが生じるので、上限を０．５％とする。高温特性と製造コスト及び靭性を考慮すると、Ｓｂ含有量の下限は０．０３％、上限は０．３％にすることが望ましい。更に望ましくはＳｂ含有量の下限は０．０５％、上限は０．２％にすることが望ましい。 Sb is an element that segregates at grain boundaries and acts to increase high-temperature strength. In order to obtain the content effect, it should be 0.002% or more. However, if it exceeds 0.5%, Sb segregation occurs and cracks occur during welding, so the upper limit is set to 0.5%. Considering the high temperature characteristics, manufacturing cost and toughness, it is desirable that the lower limit of the Sb content is 0.03% and the upper limit is 0.3%. More preferably, the lower limit of the Sb content is 0.05% and the upper limit is 0.2%.
ＲＥＭ（希土類元素）は、耐酸化性の向上に有効であり、必要に応じて０．００１％以上含有する。また、０．２％を超えて含有してもその効果は飽和し、ＲＥＭの硫化物による耐食性低下を生じるため、０．００１〜０．２％で含有する。製造コストを考慮すると、下限を０．００２％とし、上限を０．１０％とすることが望ましい。ＲＥＭ（希土類元素）は、一般的な定義に従う。スカンジウム （Ｓｃ）、イットリウム （Ｙ）の２元素と、ランタン（Ｌａ）からルテチウム（Ｌｕ） までの１５元素（ランタノイド）の総称を指す。単独で含有しても良いし、混合物であっても良い。 REM (rare earth element) is effective in improving oxidation resistance, and contains 0.001% or more as required. Further, even if it is contained in an amount of more than 0.2%, the effect is saturated and the corrosion resistance is lowered due to the sulfide of REM. Therefore, it is contained in an amount of 0.001 to 0.2%. Considering the manufacturing cost, it is desirable that the lower limit is 0.002% and the upper limit is 0.10%. REM (rare earth element) follows a general definition. It is a general term for the two elements scandium (Sc) and yttrium (Y) and the 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu). It may be contained alone or as a mixture.
Ｇａは、耐食性向上や水素脆化抑制のため、０．３％以下で含有しても良いが、０．３％超の含有により粗大硫化物が生成しｒ値が劣化する。硫化物や水素化物形成の観点から下限は０．０００２％とする。更に、製造性やコストの観点から０．００２％以上が更に好ましい。 Ga may be contained in an amount of 0.3% or less in order to improve corrosion resistance and suppress hydrogen embrittlement, but if it is contained in an amount of more than 0.3%, coarse sulfide is generated and the r value deteriorates. From the viewpoint of sulfide and hydride formation, the lower limit is 0.0002%. Further, 0.002% or more is more preferable from the viewpoint of manufacturability and cost.
Ｔａ、Ｈｆは高温強度向上のために各０．００１〜１．０％含有しても良い。０．００１％以上で効果があり、０．０１％以上でさらに高強度が得られる。なお、Ａｓ、Ｐｂ等の一般的な有害な元素や不純物元素はできるだけ低減することが望ましい。 Ta and Hf may be contained in an amount of 0.001 to 1.0%, respectively, in order to improve the high temperature strength. Effective at 0.001% or more, and higher strength can be obtained at 0.01% or more. It is desirable to reduce general harmful elements such as As and Pb and impurity elements as much as possible.
[冷延焼鈍酸洗板のΔL*（L*の最大値―最小値）がΔL*≦０．５０]
本発明では製品板において観察される表面色ムラについて色差指標L*で評価した。表１に１７％Ｃｒ−１３％Ｎｉ−３％Ｓｉ−１．４％Ｍｏ成分のオーステナイト系ステンレス薄鋼板（後記［表２］の鋼Ｎｏ．Ａ１）の中間冷延ロール粗度Ｒａ、中間焼鈍前油付着量、製品板ΔL*、溶接溶け落ち有無について示す。油付着量は１００ｍｍ（長さ）×２００ｍｍ（幅）×０．６ｍｍ（厚さ）サイズのサンプルを用いた。冷間圧延サンプルをビーカー内でノルマルヘキサン中に浸漬させて１０ｍｉｎ超音波洗浄にかけた後、回収したノルマルヘキサンを乾燥機にて完全に揮発させた乾燥後のビーカー重量と初期のビーカー重量の差を表面油付着量とした。製品板ΔL*は５００ｍｍ（長さ）×１０００ｍｍ(幅)×０．２０ｍｍ(厚さ)のサンプル表裏面を色差計を用いて最低５０点以上測定したときのL*の最大値と最小値の差とした。溶接溶け落ち性の評価はビードオンプレートＴＩＧ溶接試験にて行った。溶接試験条件は、電流１００Ａ、溶接速度５０００ｃｍ／ｍｉｎ、シールドガスＡｒ、アーク長１ｍｍとした。溶接試験後にビード部を目視で観察して溶け落ちのあったものを「×」、溶け落ちの無かったものを「〇」とした。また、高温塩害試験には４０ｍｍ(長さ)×２０ｍｍ（幅）×０．６ｍｍ（厚さ）サイズのサンプルの端面を＃６００湿式研磨して用いた。試験条件は加熱：７００℃×１１０ｍｉｎ→冷却：室温×２０ｍｉｎ→全浸漬：５％ＮａＣｌ溶液×２０ｍｉｎ→乾燥：５０℃×２５ｍｉｎを６０サイクル繰り返した。試験後のサンプル表面に付着した腐食生成物を除去後、腐食減量（＝試験前のサンプル重量―試験後のサンプル重量）を求め、腐食減量が５０ｍｇ／ｃｍ２以下のものを「〇」、５０ｍｇ／ｃｍ２より大きいものと「×」とした。中間冷延焼鈍酸洗後に研磨工程がある場合、中間冷延ロール粗度および中間焼鈍前油付着量に関係なくΔL*が小さく、溶接溶け落ちの無い良好な溶接ビードが得られるが、研磨ムラに起因して耐高温塩害性が悪化する。中間冷延焼鈍酸洗後に研磨工程がない場合、中間冷延ロール粗度がＲａ＝１．００μｍでは油付着量が多く、ΔL*が大きいため溶接溶け落ちが発生するが、中間冷延ロール粗度をＲａ＝０．０３μｍにすると、油付着量が少なくなり、ΔL*が小さく溶接溶け落ちが発生しない良好な溶接ビードが得られ、耐高温塩害性と溶接性を両立できる。
[ΔL * (maximum value-minimum value of L *) of cold-rolled annealed pickling plate is ΔL * ≤ 0.50]
In the present invention, the surface color unevenness observed on the product board was evaluated by the color difference index L *. Table 1 shows the intermediate cold-rolled roll roughness Ra and intermediate annealing of austenitic stainless steel sheet (Steel No. A1 in [Table 2] below) containing 17% Cr-13% Ni-3% Si-1.4% Mo. The amount of pre-oil adhered, the product plate ΔL *, and the presence or absence of welding melt-off are shown. A sample having a size of 100 mm (length) × 200 mm (width) × 0.6 mm (thickness) was used as the amount of oil adhered. The cold-rolled sample was immersed in normal hexane in a beaker and subjected to ultrasonic cleaning for 10 minutes, and then the recovered normal hexane was completely volatilized in a dryer to determine the difference between the beaker weight after drying and the initial beaker weight. The amount of surface oil adhered was used. The product plate ΔL * is the maximum and minimum value of L * when at least 50 points or more are measured on the front and back surfaces of a sample of 500 mm (length) x 1000 mm (width) x 0.20 mm (thickness) using a color difference meter. It was a difference. The weld melt-through property was evaluated by a bead-on-plate TIG welding test. The welding test conditions were a current of 100 A, a welding speed of 5000 cm / min, a shield gas Ar, and an arc length of 1 mm. After the welding test, the bead portion was visually observed and the one that had melted down was marked with "x", and the one without melted down was marked with "○". In the high temperature salt damage test, the end face of a sample having a size of 40 mm (length) × 20 mm (width) × 0.6 mm (thickness) was wet-polished with # 600 and used. The test conditions were heating: 700 ° C. × 110 min → cooling: room temperature × 20 min → total immersion: 5% NaCl solution × 20 min → drying: 50 ° C. × 25 min, repeated for 60 cycles. After removing the corrosion products adhering to the sample surface after the test, determine the corrosion weight loss (= sample weight before the test-sample weight after the test), and if the corrosion weight loss is 50 mg / cm 2 or less, "○", 50 mg Those larger than / cm 2 were marked with "x". When there is a polishing process after intermediate cold rolling annealing pickling, ΔL * is small regardless of the intermediate cold rolling roll roughness and the amount of oil adhering before intermediate annealing, and a good weld bead without welding melt-off can be obtained, but polishing unevenness is obtained. Due to this, high temperature salt damage resistance deteriorates. If there is no polishing process after intermediate cold rolling annealing pickling, if the intermediate cold rolling roll roughness is Ra = 1.00 μm, the amount of oil adhered is large and the ΔL * is large, so welding melt-off occurs, but the intermediate cold rolling roll coarseness When the degree is Ra = 0.03 μm, the amount of oil adhered is small, ΔL * is small, and a good weld bead that does not cause welding melt-off can be obtained, and both high-temperature salt damage resistance and weldability can be achieved.
［製造方法］
次に製造方法について説明する。本発明の鋼板の製造方法は、基本的に製鋼−熱間圧延−焼鈍・酸洗−冷間圧延−焼鈍・酸洗よりなる。製鋼においては、前記必須成分および必要に応じて含有される成分を含有する鋼を、電気炉溶製あるいは転炉溶製し、続いて２次精錬を行う方法が好適である。溶製した溶鋼は、公知の鋳造方法（連続鋳造など）に従ってスラブとする。スラブは、所定の温度に加熱され、所定の板厚に連続圧延で熱間圧延される。熱間圧延後の鋼板は、一般的には熱延板焼鈍と酸洗処理が施されるが、熱延板焼鈍を省略しても構わない。
[Production method]
Next, the manufacturing method will be described. The method for producing a steel sheet of the present invention basically comprises steelmaking-hot rolling-annealing / pickling-cold rolling-annealing / pickling. In steelmaking, a method is preferable in which steel containing the above-mentioned essential components and components contained as necessary is melted in an electric furnace or a converter, followed by secondary refining. The molten steel is made into a slab according to a known casting method (continuous casting or the like). The slab is heated to a predetermined temperature and hot-rolled to a predetermined plate thickness by continuous rolling. The steel sheet after hot rolling is generally subjected to hot-rolled sheet annealing and pickling treatment, but hot-rolled sheet annealing may be omitted.
熱間圧延焼鈍板は必要に応じて表面研削を施した後に所定の板厚に冷間圧延され、焼鈍・酸洗が施される。本発明は、複数回の冷間圧延−焼鈍・酸洗を施す場合、上述のように中間の冷間圧延ロール粗度と焼鈍前の油付着量が製品板の表面色ムラおよび溶接溶け落ちに影響を及ぼすこと知見したため、中間の冷間圧延ワークロール粗度を特定し、必要に応じ、中間冷延された後焼鈍前の鋼板表面の油付着量をも特定した。具体的には冷間圧延ワークロール粗度ＲａがＲａ≦０．５０μｍ、冷延板焼鈍前の油付着量を２００ｍｍ２あたり１５０ｍｇ以下とする。冷間圧延鋼板の表面には圧延ワークロール目が転写される。そのため粗いワークロールを使用すると鋼板の表面粗度が粗くなり付着した圧延油が浸み込みやすく除去しにくくなる。粗度の小さなワークロールを使用すると平滑な鋼板表面を得ることが出来、表面に付着した油の除去も簡単となる。そのため冷間圧延ワークロール粗度Ｒａ≦０．１０μｍ、冷延板焼鈍前の油付着量を２００ｍｍ２あたり１１０ｍｇ以下とすることもできる。冷間圧延中は圧延油を流した状態となるが冷間圧延終了後は焼鈍前に余分な油を除去する必要がある。油を除去する方法は油切りワイパー、水、温水やアルカリ性の洗浄剤を使用するなど適宜選択すればよい。 The hot-rolled annealed plate is surface-ground if necessary, then cold-rolled to a predetermined plate thickness, and annealed and pickled. In the present invention, when cold rolling-annealing / pickling is performed a plurality of times, as described above, the intermediate cold-rolled roll roughness and the amount of oil adhered before annealing cause uneven surface color and melt-through of the product plate. Since it was found to have an effect, the roughness of the intermediate cold-rolled work roll was specified, and if necessary, the amount of oil adhered to the surface of the steel sheet after intermediate cold rolling and before annealing was also specified. Specifically, the cold-rolled work roll roughness Ra is Ra ≦ 0.50 μm, and the amount of oil adhered before annealing the cold-rolled plate is 150 mg or less per 200 mm 2. Rolled work rolls are transferred to the surface of the cold-rolled steel sheet. Therefore, if a coarse work roll is used, the surface roughness of the steel sheet becomes rough, and the adhering rolling oil easily penetrates and becomes difficult to remove. When a work roll having a small roughness is used, a smooth steel plate surface can be obtained, and oil adhering to the surface can be easily removed. Therefore, the roughness of the cold-rolled work roll Ra ≦ 0.10 μm, and the amount of oil adhered before annealing the cold-rolled plate can be set to 110 mg or less per 200 mm 2. During cold rolling, the rolling oil is in a flowing state, but after the completion of cold rolling, it is necessary to remove excess oil before annealing. The method for removing the oil may be appropriately selected, such as using an oil drain wiper, water, warm water, or an alkaline cleaning agent.
なお、製造工程における他の条件は適宜選択すれば良い。例えば、スラブ厚さ、熱間圧延板厚などは適宜設計すれば良い。冷間圧延においては、ロール径、圧延油、圧延パス回数、圧延速度、圧延温度などは適宜選択すれば良い。冷間圧延の途中に入る中間焼鈍は、バッチ式焼鈍でも連続式焼鈍でも良い。また焼鈍工程の温度、時間、冷却速度等は十分再結晶した冷延焼鈍鋼板が得られる条件を選択すればよい。酸洗工程は、硝酸、硝酸電解酸洗の他、硫酸や塩酸を用いた処理を行っても良い。冷延板の焼鈍・酸洗後にテンションレベラー等により形状および材質調整を行っても良い。加えて、プレス成形を向上させる目的で、潤滑皮膜を製品板に付与することも可能である。 In addition, other conditions in the manufacturing process may be appropriately selected. For example, the slab thickness, the hot-rolled plate thickness, and the like may be appropriately designed. In cold rolling, the roll diameter, rolling oil, number of rolling passes, rolling speed, rolling temperature and the like may be appropriately selected. The intermediate annealing that enters the middle of cold rolling may be batch annealing or continuous annealing. Further, the temperature, time, cooling rate, etc. of the annealing step may be selected from the conditions under which a sufficiently recrystallized cold-rolled annealed steel sheet can be obtained. In the pickling step, in addition to nitric acid and nitric acid electrolytic pickling, treatment with sulfuric acid or hydrochloric acid may be performed. After annealing and pickling the cold-rolled plate, the shape and material may be adjusted by a tension leveler or the like. In addition, a lubricating film can be applied to the product plate for the purpose of improving press molding.
表２に示す成分組成の鋼を溶製した後、熱延、熱延板焼鈍・酸洗、中間冷延、中間焼鈍・酸洗、最終冷延、最終焼鈍・酸洗を施して０．２ｍｍ厚の製品鋼板を得た。ここで、中間および最終冷延板焼鈍前に温水を用いて鋼板表面の洗浄を行った。中間および最終冷延板の焼鈍条件は、再結晶組織が得られる様に、加熱温度１０５０〜１１００℃とした。中間冷延板焼鈍前の表面油付着量の測定、製品板の色差ΔL*の測定、溶接溶け落ち性、耐高温塩害性の評価は上述した方法で行った。 After melting the steel with the composition shown in Table 2, hot rolling, hot rolling plate annealing / pickling, intermediate cold rolling, intermediate annealing / pickling, final cold rolling, final annealing / pickling are performed to 0.2 mm. A thick product steel sheet was obtained. Here, the surface of the steel sheet was washed with warm water before the intermediate and final cold-rolled sheet was annealed. The annealing conditions of the intermediate and final cold rolled plates were set to a heating temperature of 1050 to 1100 ° C. so that a recrystallized structure could be obtained. The amount of surface oil adhering before annealing the intermediate cold-rolled plate, the color difference ΔL * of the product plate, the weld melt-through resistance, and the high-temperature salt damage resistance were evaluated by the above-mentioned methods.
表３に本発明例および比較例の中間冷延ロール粗度、中間焼鈍前油付着量、製品板の色差ΔL*、溶接溶け落ちの有無および耐高温塩害性の結果を示す。比較例はＡ１をロール粗度をＲａ＝１．００μｍおよび０．８０μｍと粗くして製造した。従来例は、鋼成分のＳｉ量が規定範囲外であり、ロール粗度が粗くかつ中間研磨無しで、ΔL*は規定範囲内で溶接溶け落ちは無いが、要求特性のひとつである耐高温塩害性を満足できない。本発明例は、冷延板焼鈍前の表面油付着量が１５０ｍｇ以下であり、製品板のΔL*がΔL*≦０．５０μｍで表面色ムラが抑制され溶接溶け落ちが無く、耐高温塩害性と溶接性を両立したオーステナイト系ステンレス鋼板が得られた。 Table 3 shows the intermediate cold-rolled roll roughness, the amount of oil adhered before intermediate annealing, the color difference ΔL * of the product plate, the presence or absence of welding melt-through, and the results of high-temperature salt damage resistance in Examples of the present invention and Comparative Examples. A comparative example was produced by roughening A1 with a roll roughness of Ra = 1.00 μm and 0.80 μm. In the conventional example, the amount of Si in the steel component is out of the specified range, the roll roughness is rough and there is no intermediate polishing, and ΔL * is within the specified range and there is no weld melt-off, but high temperature salt damage resistance, which is one of the required characteristics. I can't be satisfied with my sex. In the example of the present invention, the amount of surface oil adhered before annealing the cold-rolled sheet is 150 mg or less, the ΔL * of the product plate is ΔL * ≤ 0.50 μm, surface color unevenness is suppressed, welding does not melt off, and high temperature salt damage resistance An austenitic stainless steel sheet having both good weldability was obtained.
本発明によれば、自動車のエキゾーストマニホールド、ターボ、エキゾーストパイプ、コンバーター、フレキシブルチューブ、排熱回収機、ＤＰＦ（Ｄｉｅｚｅｌ Ｐａｒｔｉｃｕｌａｔｅ Ｆｉｌｔｅｒ）、ＧＰＦ（Ｇａｓｏｌｉｎｅ Ｐａｒｔｉｃｕｌａｔｅ Ｆｉｌｔｅｒ）、尿素ＳＣＲ（Ｓｅｌｅｃｔｉｖｅ Ｃａｔａｌｙｔｉｃ Ｒｅｄｕｃｔｉｏｎ）、ガスケット、耐熱ばね、マフラー部品等に使用される表面色ムラの少ないオーステナイト系ステンレス薄鋼板を得ることが出来る。特に板厚が０．２ｍｍ〜０．３ｍｍ程度で溶接溶け落ちが抑制されるため溶接構造を有する部品に適用することが可能であり、排気部品に好適であるなど、産業上で有益である。 According to the present invention, an automobile exhaust manifold, turbo, exhaust pipe, converter, flexible tube, exhaust heat recovery device, DPF (Diesel Particulate Filter), GPF (Gasoline Particulate Filter), urea SCR (Selective Catalytic Gasket) It is possible to obtain an austenite-based stainless steel thin steel plate with less surface color unevenness used for heat-resistant springs, muffler parts, and the like. In particular, since welding melt-off is suppressed when the plate thickness is about 0.2 mm to 0.3 mm, it can be applied to parts having a welded structure, and is suitable for exhaust parts, which is industrially beneficial.
Claims (6)
酸洗された冷延焼鈍鋼板における、表面の色差指標L*の最大値と最小値の差ΔL*がΔL*≦０．５０であり、耐高温塩害性の劣化が抑制されることを特徴とするオーステナイト系ステンレス鋼板。 An austenitic stainless steel containing 0.5 to 4.0% of Si in mass%.
In the pickled cold-rolled annealed steel sheet, the difference ΔL * between the maximum value and the minimum value of the surface color difference index L * is ΔL * ≤ 0.50, and the deterioration of high temperature salt damage resistance is suppressed. Austenitic stainless steel sheet.
Ｃ：０．００２〜０．３００％、
Ｓｉ：０．５〜４．０％、
Ｍｎ：０．０５〜１０．００％、
Ｐ：０．００１〜０．０５０％、
Ｓ：０．０００１〜０．０１００％、
Ｎｉ：２〜２５％、
Ｃｒ：１５〜３０％、
Ｎ：０．００２〜０．５００％、
Ａｌ：０．００１〜１．０００％、
Ｃｕ：０．１〜４．０％、
Ｍｏ：０．０１〜３．００％、
Ｖ：０．０１〜１．００％、
を含有し、残部がＦｅ及び不可避的不純物からなる請求項１に記載のオーステナイト系ステンレス鋼板。 By mass%
C: 0.002 to 0.300%,
Si: 0.5-4.0%,
Mn: 0.05 to 10.00%,
P: 0.001 to 0.050%,
S: 0.0001 to 0.0100%,
Ni: 2-25%,
Cr: 15-30%,
N: 0.002 to 0.500%,
Al: 0.001 to 1.000%,
Cu: 0.1-4.0%,
Mo: 0.01 to 3.00%,
V: 0.01 to 1.00%,
The austenitic stainless steel sheet according to claim 1, wherein the austenitic stainless steel sheet contains Fe and the balance is composed of Fe and unavoidable impurities.
Ｎｂ：０．３００％以下、
Ｔｉ：０．３００％以下、
Ｂ：０．００６０％以下、
Ｃａ：０．０１００％以下、
Ｗ：３．００％以下、
Ｚｒ：０．３０％以下、
Ｓｎ：０．５０％以下、
Ｃｏ：０．３０％以下、
Ｍｇ：０．０１００％以下、
Ｓｂ：０．５００％以下、
ＲＥＭ：０．２００％以下、
Ｇａ：０．３０００％以下、
Ｔａ：１．０００％以下、
Ｈｆ：１．０００％以下、
から選択される１種または２種以上を含有することを特徴とする請求項２に記載のオーステナイト系ステンレス鋼板。 Furthermore, in mass%, Nb: 0.300% or less,
Ti: 0.300% or less,
B: 0.0060% or less,
Ca: 0.0100% or less,
W: 3.00% or less,
Zr: 0.30% or less,
Sn: 0.50% or less,
Co: 0.30% or less,
Mg: 0.0100% or less,
Sb: 0.500% or less,
REM: 0.200% or less,
Ga: 0.3000% or less,
Ta: 1.000% or less,
Hf: 1.000% or less,
The austenitic stainless steel sheet according to claim 2, wherein the austenitic stainless steel sheet contains one or more selected from the above.
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