JP2014005479A - Ferritic stainless steel - Google Patents
Ferritic stainless steel Download PDFInfo
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- JP2014005479A JP2014005479A JP2012134341A JP2012134341A JP2014005479A JP 2014005479 A JP2014005479 A JP 2014005479A JP 2012134341 A JP2012134341 A JP 2012134341A JP 2012134341 A JP2012134341 A JP 2012134341A JP 2014005479 A JP2014005479 A JP 2014005479A
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 31
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 33
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 19
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 16
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 13
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 5
- 229910052802 copper Inorganic materials 0.000 claims abstract description 4
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 4
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims description 14
- 230000007797 corrosion Effects 0.000 abstract description 55
- 238000005260 corrosion Methods 0.000 abstract description 55
- 239000002253 acid Substances 0.000 abstract description 8
- 238000004140 cleaning Methods 0.000 abstract 1
- 239000010936 titanium Substances 0.000 description 47
- 238000005554 pickling Methods 0.000 description 38
- 239000002436 steel type Substances 0.000 description 33
- 238000003466 welding Methods 0.000 description 33
- 239000011651 chromium Substances 0.000 description 28
- 239000000463 material Substances 0.000 description 27
- 150000003839 salts Chemical class 0.000 description 20
- 239000007921 spray Substances 0.000 description 19
- 238000000137 annealing Methods 0.000 description 17
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 14
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 14
- 229910000831 Steel Inorganic materials 0.000 description 12
- 239000010959 steel Substances 0.000 description 12
- 238000005097 cold rolling Methods 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 7
- 229910017604 nitric acid Inorganic materials 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 230000007547 defect Effects 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000009749 continuous casting Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000000567 combustion gas Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000005498 polishing Methods 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 206010070834 Sensitisation Diseases 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000000945 filler Substances 0.000 description 3
- 230000001771 impaired effect Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000008313 sensitization Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 230000005856 abnormality Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000004677 Nylon Substances 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Landscapes
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
本発明は、フェライト系ステンレス鋼に関し、表面性状に優れ、且つ、溶接部の耐食性および酸洗性に優れたフェライト系ステンレス鋼に関するものである。 The present invention relates to a ferritic stainless steel, and relates to a ferritic stainless steel having excellent surface properties and excellent corrosion resistance and pickling properties of a welded portion.
ステンレス鋼の中では、その優れた耐食性によりオーステナイト系ステンレス鋼のSUS304(18%Cr−8%Ni)(日本工業規格、JIS G 4305)が広く使われている。しかし、この鋼種は、Niを多量に含むため高価である。 Among stainless steels, austenitic stainless steel SUS304 (18% Cr-8% Ni) (Japanese Industrial Standard, JIS G 4305) is widely used due to its excellent corrosion resistance. However, this steel type is expensive because it contains a large amount of Ni.
これに対して、特許文献1には、成分組成として、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、22.5%以下、Cu:0.3%以上、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%以下を含有し、残部がFeおよび不可避的不純物からなることを特徴とするフェライト系ステンレス鋼板が開示されている。
このステンレス鋼板はその優れた耐食性とNiを使用しないことによる経済性から、建築部材、産業機械、厨房類に広く使用されている。
On the other hand, in Patent Document 1, as component composition, C: 0.03% or less, Si: 1.0% or less, Mn: 0.5% or less, P: 0.04% or less, S: 0 0.02% or less, Al: 0.1% or less, Cr: 20.5% or more, 22.5% or less, Cu: 0.3% or more, 0.8% or less, Ni: 1.0% or less, Ti : 4 × (C% + N%) or more, 0.35% or less, Nb: 0.01% or less, N: 0.03% or less, C + N: 0.05% or less, the balance being Fe and inevitable A ferritic stainless steel sheet comprising impurities is disclosed.
This stainless steel plate is widely used for building members, industrial machines, and kitchens because of its excellent corrosion resistance and economy by not using Ni.
しかし、特許文献1に開示されるフェライト系ステンレス鋼板が産業機械等に用いられる場合には、同一鋼種同士だけでなく、異鋼種、特にSUS304と溶接されて使用されることが多い。その場合も良好な耐食性を保つことが求められる。本鋼種は同一鋼種での溶接部は良好な耐食性を持つが、SUS304とTIG溶接された場合、溶接部の耐食性が母材より低下する場合が起こるという問題がある。 However, when the ferritic stainless steel sheet disclosed in Patent Document 1 is used for industrial machinery or the like, it is often used by welding not only to the same steel type but also to a different steel type, particularly SUS304. Even in that case, it is required to maintain good corrosion resistance. Although this steel type has good corrosion resistance in welded parts of the same steel type, there is a problem that when SUS304 and TIG are welded, the corrosion resistance of the welded part is lower than that of the base material.
溶接部の耐食性は、溶接時の熱履歴で鋼中のC、NがCrと結合して、クロム炭窒化物として粒界に析出することにより、粒界にクロム欠乏層が生じることにより起こる(鋭敏化)。これを防ぐために、鋼中のC、Nを低減するとともに、適量のTiを添加して、C、Nをチタン炭窒化物として固定化して、クロム炭窒化物の生成を防止する方法が取られている。この方法により、特許文献1に開示されるフェライト系ステンレス鋼板同士でのTIG溶接部は良好な耐食性を維持している。 The corrosion resistance of the welded portion is caused by the fact that C and N in the steel are combined with Cr in the heat history during welding and precipitated at the grain boundary as chromium carbonitride, thereby forming a chromium-deficient layer at the grain boundary ( Sensitization). In order to prevent this, a method of reducing the amount of C and N in the steel and adding an appropriate amount of Ti to fix C and N as titanium carbonitride to prevent the formation of chromium carbonitride is taken. ing. By this method, the TIG welded portion between the ferritic stainless steel plates disclosed in Patent Document 1 maintains good corrosion resistance.
しかし、上記鋼板のC含有量が0.01%程度であるのに対して、SUS304はC含有量が0.04〜0.05%と高いために、上記鋼板とSUS304との接合部で、鋭敏化を防止するためには、Ti添加量を0.4〜1.0%程度までに高めなければならない。 However, while the C content of the steel sheet is about 0.01%, SUS304 has a high C content of 0.04 to 0.05%, so that at the joint between the steel sheet and SUS304, In order to prevent sensitization, the amount of Ti added must be increased to about 0.4 to 1.0%.
しかし、このようにTiを添加すると鋼が脆くなったり、Tiが窒素と結合してTiNとなりこれが集合して、いわゆるチタンストリンガーの大量発生により表面性状が著しく損なわれてしまう。 However, when Ti is added in this manner, the steel becomes brittle, or Ti combines with nitrogen to become TiN, which aggregates and the surface properties are significantly impaired due to the large amount of so-called titanium stringers.
このように、従来技術ではSUS304との異鋼種TIG溶接部の耐食性と表面性状の両立は困難であった。また、溶接を行うと表面に酸化皮膜が生成して(溶接焼けとも呼ばれる)美観が損なわれるので、酸洗で該酸化皮膜を除去する必要がある。しかし、特許文献1に開示されたフェライト系ステンレス鋼は、その溶接部の酸化皮膜は酸洗で除去されにくいという問題があった。 Thus, in the prior art, it was difficult to achieve both the corrosion resistance and the surface properties of the different steel type TIG welds with SUS304. Further, when welding is performed, an oxide film is formed on the surface (also referred to as welding burn) and the aesthetic appearance is impaired. Therefore, it is necessary to remove the oxide film by pickling. However, the ferritic stainless steel disclosed in Patent Document 1 has a problem that the oxide film of the welded portion is difficult to be removed by pickling.
本発明は、かかる事情に鑑み、表面性状に優れ、且つ、同一鋼種同士だけでなく異鋼種、特にSUS304と溶接されて使用される場合も、溶接部の耐食性および酸洗性に優れたフェライト系ステンレス鋼を提供することを目的とする。 In view of such circumstances, the present invention is excellent in surface properties, and not only the same steel type but also different steel types, especially when used welded to SUS304, a ferrite system excellent in corrosion resistance and pickling properties of the welded portion. It aims to provide stainless steel.
発明者等は、適量のSiを添加すると、チタン炭窒化物の析出が凝固の初期段階で促進されて、析出物の寸法が小さくなり、チタンストリンガーの問題を解消できること、溶接時に酸化皮膜の生成が抑制されて、溶接後の酸洗で酸化皮膜が除去されやすくなることを見出した。さらに、Cr添加量を適正化することにより、SUS304とのTIG溶接部に、マルテンサイト相を析出させることにより、鋭敏化を防止できることを見出した。 When the inventors add an appropriate amount of Si, the precipitation of titanium carbonitride is promoted at the initial stage of solidification, the size of the precipitate is reduced, and the problem of titanium stringer can be solved, and the formation of an oxide film during welding It was found that the oxide film was easily removed by pickling after welding. Furthermore, it discovered that sensitization could be prevented by precipitating a martensite phase in the TIG weld part with SUS304 by optimizing the amount of Cr added.
これにより、良好な耐食性を持ち、表面研削を行うことなく熱延焼鈍酸洗板から良好な表面品質の冷延焼鈍酸洗板を製作でき、さらにSUS304とのTIG溶接部の耐食性および酸洗性も良好なフェライト系ステンレス鋼が得られることを見出した。 As a result, it is possible to produce a cold rolled annealed pickling plate having a good surface quality from a hot rolled annealed pickling plate without surface grinding, and further, corrosion resistance and pickling properties of a TIG welded portion with SUS304. It was also found that a good ferritic stainless steel can be obtained.
本発明は、以上の知見に基づきなされたもので、その要旨は以下のとおりである。 The present invention has been made based on the above findings, and the gist thereof is as follows.
[1]質量%で、C:0.010%以下、Si:0.15〜0.60%、Mn:0.5%以下、P:0.04%以下、S:0.01%以下、Al:0.2%以下、Cr:17.0〜19.0%、Cu:0.3〜0.5%、Ni:0.6%以下、Ti:0.10〜0.20%、N:0.015%以下、C+N:0.02%以下を含有し、残部Feおよび不可避的不純物からなり、下記式(1)を満たすことを特徴とするフェライト系ステンレス鋼。
Ti%/(C%+N%)≧8 (1)
ここで、C%、N%、Ti%は、それぞれC、N、Tiの含有量(質量%)を表す。
[1] By mass%, C: 0.010% or less, Si: 0.15 to 0.60%, Mn: 0.5% or less, P: 0.04% or less, S: 0.01% or less, Al: 0.2% or less, Cr: 17.0 to 19.0%, Cu: 0.3 to 0.5%, Ni: 0.6% or less, Ti: 0.10 to 0.20%, N : Ferritic stainless steel containing 0.015% or less, C + N: 0.02% or less, consisting of the balance Fe and inevitable impurities and satisfying the following formula (1).
Ti% / (C% + N%) ≧ 8 (1)
Here, C%, N%, and Ti% represent the contents (mass%) of C, N, and Ti, respectively.
[2]前記成分組成に加えてさらに、質量%で、Ca:0.0005〜0.0020%、B:0.0003〜0.0020%の中から選ばれる1種または2種を含有することを特徴とする上記[1]に記載のフェライト系ステンレス鋼。 [2] In addition to the above component composition, the composition further contains one or two selected from Ca: 0.0005 to 0.0020% and B: 0.0003 to 0.0020% by mass%. The ferritic stainless steel as described in [1] above.
[3]前記成分組成に加えてさらに、下記式(2)を満たすことを特徴とする上記[1]または[2]に記載のフェライト系ステンレス鋼。
Si%/Ti%≧1.3 (2)
ここで、Si%、Ti%は、それぞれSi、Tiの含有量(質量%)を表す。
[3] The ferritic stainless steel according to the above [1] or [2], which further satisfies the following formula (2) in addition to the component composition.
Si% / Ti% ≧ 1.3 (2)
Here, Si% and Ti% represent the contents (mass%) of Si and Ti, respectively.
[4]前記成分組成に加えてさらに、下記式(3)を満たすことを特徴とする上記[1]乃至[3]に記載のフェライト系ステンレス鋼。
Si%/Cr%≧0.013 (3)
ここで、Si%、Cr%は、それぞれSi、Crの含有量(質量%)を表す。
[4] The ferritic stainless steel according to the above [1] to [3], which satisfies the following formula (3) in addition to the component composition.
Si% / Cr% ≧ 0.013 (3)
Here, Si% and Cr% represent the contents (mass%) of Si and Cr, respectively.
本発明によれば、同一鋼種同士だけでなく異鋼種、特にSUS304と溶接されて使用される場合も良好な溶接部の耐食性を有するフェライト系ステンレス鋼が得られる。また、本発明のステンレス鋼板は、適量のSiを添加することによりチタンストリンガーの発生を防止できるので、チタンストリンガーの発生を防止するための熱延板での表面研削が不要となり、安価に製造することができる。さらに、溶接部に生成した酸化皮膜を酸洗で容易に除去して良好な外観が得られる。 According to the present invention, a ferritic stainless steel having good corrosion resistance of a welded portion can be obtained not only between the same steel types but also when used by welding with different steel types, particularly SUS304. In addition, since the stainless steel sheet of the present invention can prevent the generation of titanium stringers by adding an appropriate amount of Si, surface grinding with a hot-rolled sheet for preventing the generation of titanium stringers is unnecessary, and is manufactured at a low cost. be able to. Furthermore, a good appearance can be obtained by easily removing the oxide film formed on the welded portion by pickling.
以下に本発明の各構成要件の限定理由について説明する。 The reasons for limiting the respective constituent requirements of the present invention will be described below.
[成分組成]
はじめに、本発明の鋼の成分組成を規定した理由を説明する。なお、成分%は、すべて質量%を意味する。
[Ingredient composition]
First, the reason for defining the component composition of the steel of the present invention will be described. In addition, all component% means the mass%.
C:0.010%以下、N:0.015%以下、C+N:0.02%以下
CおよびNは溶接部の耐食性を低下させるので少ないほうが望ましく、C:0.010%以下、N:0.015%以下、C+N:0.02%以下とする。
C: 0.010% or less, N: 0.015% or less, C + N: 0.02% or less C and N are desirable because they reduce the corrosion resistance of the welded portion. C: 0.010% or less, N: 0 0.15% or less, C + N: 0.02% or less.
Si:0.15〜0.60%
Siは、チタン炭窒化物の析出を制御し、表面性状を向上させるのに必要な元素である。しかし、0.15%未満ではその効果は得られず、多量に添加すると加工性と冷延板焼鈍時の酸洗性を低下させるので、Si量は0.15〜0.60%の範囲とする。好ましくは0.20〜0.50%の範囲である。さらに好ましくは0.20〜0.40%の範囲である。
Si: 0.15-0.60%
Si is an element necessary for controlling the precipitation of titanium carbonitride and improving the surface properties. However, if it is less than 0.15%, the effect cannot be obtained, and if added in a large amount, the workability and pickling properties during cold-rolled sheet annealing are lowered, so the Si amount is in the range of 0.15 to 0.60%. To do. Preferably it is 0.20 to 0.50% of range. More preferably, it is 0.20 to 0.40% of range.
Mn:0.5%以下
Mnは、脱酸作用があるが、鋼中で硫化物を形成し、著しく耐食性を低下させるため添加量は低い方が望ましく、製造時の経済性を考慮して0.5%以下とする。ただし、Mn量が少なすぎると介在物が増えるので、好ましくは0.1〜0.4%の範囲である。
Mn: 0.5% or less Although Mn has a deoxidizing action, it is desirable that the addition amount be low because it forms sulfides in the steel and significantly reduces the corrosion resistance. .5% or less. However, if the amount of Mn is too small, inclusions increase, so the content is preferably in the range of 0.1 to 0.4%.
P:0.04%以下
Pは、熱間加工性の点から少ない方が望ましく、0.04%以下とする。
P: 0.04% or less P is preferably smaller in terms of hot workability, and is 0.04% or less.
S:0.01%以下
Sは、熱間加工性及び耐食性の点から少ないほうが望ましく、0.01%以下とする。好ましくは、0.006%以下である。
S: 0.01% or less S is preferably smaller in terms of hot workability and corrosion resistance, and is 0.01% or less. Preferably, it is 0.006% or less.
Al:0.2%以下
Alは、脱酸に有効な成分であるが、過剰添加はAl系の非金属介在物の増加により表面疵を招くとともに加工性も低下させることから、0.2%以下とする。Alは、溶接能率を低下させることから、好ましくは、0.06%以下である。
Al: 0.2% or less Al is an effective component for deoxidation, but excessive addition leads to surface flaws due to an increase in Al-based non-metallic inclusions and lowers workability, so 0.2% The following. Al is preferably 0.06% or less because it lowers the welding efficiency.
Cr:17.0〜19.0%
Crは、耐食性改善に有効であり、良好な耐食性を得るためには17.0%以上の添加が必要であるが、19.0%を超えての添加はSUS304とのTIG溶接部でマルテンサイトが生成しなくなり耐食性低下を防止できなくなるので、Cr量は17.0〜19.0%の範囲とする。好ましくは17.5〜18.5%の範囲である。より好ましくは18.0〜18.5%の範囲である。
Cr: 17.0 to 19.0%
Cr is effective in improving the corrosion resistance, and in order to obtain good corrosion resistance, addition of 17.0% or more is necessary, but addition exceeding 19.0% is martensite in the TIG welded portion with SUS304. Is not generated and the corrosion resistance cannot be prevented from being lowered, so the Cr content is set in the range of 17.0 to 19.0%. Preferably it is 17.5 to 18.5% of range. More preferably, it is 18.0 to 18.5% of range.
Cu:0.3〜0.5%
Cuは、耐食性を確保するために必要な元素であり、そのためには少なくとも0.3%以上添加することが必要である。しかし、0.5%を超えると熱間加工性が劣化する。従ってCu量は0.3〜0.5%の範囲とする。
Cu: 0.3 to 0.5%
Cu is an element necessary for ensuring corrosion resistance, and for that purpose, it is necessary to add at least 0.3% or more. However, when it exceeds 0.5%, hot workability deteriorates. Therefore, the amount of Cu is made 0.3 to 0.5%.
Ni:0.6%以下
Niは、耐食性向上に有効であるが、高価な元素であることと0.6%を超えて添加すると応力腐食割れを発生する可能性があるので、0.6%以下とする。好ましくは0.4%以下である。
Ni: 0.6% or less Ni is effective in improving corrosion resistance, but it is an expensive element, and if added over 0.6%, stress corrosion cracking may occur, so 0.6% The following. Preferably it is 0.4% or less.
Ti:0.10〜0.20%、Ti%/(C%+N%)≧8
Tiは、溶接部の耐食性を確保するために必要不可欠な成分であり、0.10%以上でかつ、Ti%/(C%+N%)≧8の添加が必要である。しかし、0.20%を超えて過剰に添加すると熱延板の表面性状を悪化させる。よって、Ti量は0.10〜0.20%の範囲とする。溶接部の耐食性を確保するためには、Ti%/(C%+N%)≧10が望ましい。ここで、C%、N%、Ti%は、それぞれC、N、Tiの含有量(質量%)を表す。
Ti: 0.10 to 0.20%, Ti% / (C% + N%) ≧ 8
Ti is an indispensable component for ensuring the corrosion resistance of the welded portion, and it is necessary to add Ti% / (C% + N%) ≧ 8 at 0.10% or more. However, if it exceeds 0.20% and is added excessively, the surface properties of the hot-rolled sheet are deteriorated. Therefore, the Ti amount is in the range of 0.10 to 0.20%. In order to ensure the corrosion resistance of the welded portion, it is desirable that Ti% / (C% + N%) ≧ 10. Here, C%, N%, and Ti% represent the contents (mass%) of C, N, and Ti, respectively.
以上が本発明の基本化学成分であるが、さらにCa、Bの1種または2種を添加することができる。 The above is the basic chemical component of the present invention, and one or two of Ca and B can be further added.
Ca:0.0005〜0.0020%
Caは、連続鋳造の際に発生しやすいTi系介在物析出によるノズルの閉塞を防止するのに有効な成分である。0.0005%未満ではその効果がなく、0.0020%を超えると耐食性が低下するので、Ca量は0.0005〜0.0020%の範囲とする。
Ca: 0.0005 to 0.0020%
Ca is an effective component for preventing nozzle clogging due to precipitation of Ti-based inclusions that are likely to occur during continuous casting. If it is less than 0.0005%, the effect is not obtained, and if it exceeds 0.0020%, the corrosion resistance is lowered. Therefore, the Ca content is set in the range of 0.0005 to 0.0020%.
B:0.0003〜0.0020%
Bは、低温二次加工脆化を防止するのに有効である。0.0003%未満ではその効果がなく、0.0020%を超えると熱間加工性が低下するので、B量は0.0003〜0.0020%の範囲とする。好ましくは0.0003〜0.0010%の範囲である。
B: 0.0003 to 0.0020%
B is effective in preventing low temperature secondary work embrittlement. If it is less than 0.0003%, the effect is not obtained, and if it exceeds 0.0020%, the hot workability deteriorates, so the amount of B is set in the range of 0.0003 to 0.0020%. Preferably it is 0.0003 to 0.0010% of range.
上記以外の残部はFeおよび不可避的不純物である。不純物の例として、Cr鉱石からV、Coが混入することがあるが、混入すると鋼が硬くなり加工性が低下するので、それぞれ0.5%以下とする。 The balance other than the above is Fe and inevitable impurities. As an example of impurities, V and Co may be mixed from Cr ore, but if mixed, the steel becomes hard and the workability deteriorates.
Si%/Ti%≧1.3
Ti添加量が多い場合、大きなチタン炭窒化物が析出して表面性状が劣化しやすい。そこで、Ti添加量が多い場合は、Si添加量を増やして、凝固の初期段階でのチタン炭窒化物の析出をさらに促進させて、大きなチタン炭窒化物の析出を防止する必要がある。このために、Si%/Ti%≧1.3のSi添加が望ましい。ここで、Si%、Ti%は、それぞれSi、Tiの含有量(質量%)を表す。
Si% / Ti% ≧ 1.3
When the amount of Ti added is large, large titanium carbonitride precipitates and the surface properties tend to deteriorate. Therefore, when the amount of Ti added is large, it is necessary to increase the amount of Si added to further promote the precipitation of titanium carbonitride at the initial stage of solidification and prevent the precipitation of large titanium carbonitride. For this reason, Si addition of Si% / Ti% ≧ 1.3 is desirable. Here, Si% and Ti% represent the contents (mass%) of Si and Ti, respectively.
Si%/Cr%≧0.013
ステンレス鋼の溶接を行うと表面に酸化皮膜が生成して美観が損なわれるので、多くの用途では酸洗でこの酸化皮膜を除去しなければならない。しかし、フェライト系ステンレス鋼の中でCr含有量が多いものでは、Cr酸化物が多い酸化皮膜が生成し、酸洗で除去しにくい問題がある。そこで、SiはCrより酸化されやすいので、Cr含有量に対するSi含有量の比率を上げて、Si酸化物の生成量を増やして、Cr酸化物の生成を抑制すると、酸化皮膜は酸洗で除去しやすくなることを見出した。この効果を得るために、Si%/Cr%≧0.013が望ましい。ここで、Si%、Cr%は、それぞれSi、Crの含有量(質量%)を表す。
Si% / Cr% ≧ 0.013
When stainless steel is welded, an oxide film is formed on the surface and the aesthetic appearance is impaired. In many applications, this oxide film must be removed by pickling. However, ferritic stainless steel having a high Cr content produces an oxide film containing a large amount of Cr oxide, which is difficult to remove by pickling. Therefore, since Si is more easily oxidized than Cr, increasing the ratio of Si content to Cr content, increasing the amount of Si oxide generated, and suppressing the formation of Cr oxide will remove the oxide film by pickling. I found it easier to do. In order to obtain this effect, Si% / Cr% ≧ 0.013 is desirable. Here, Si% and Cr% represent the contents (mass%) of Si and Cr, respectively.
[製造方法]
次に本発明の溶接部の耐食性、酸洗性および表面性状に優れたフェライト系ステンレス鋼板の製造方法について説明する。
[Production method]
Next, the manufacturing method of the ferritic stainless steel sheet excellent in the corrosion resistance, pickling property and surface property of the welded portion of the present invention will be described.
本発明鋼の高効率な製造方法としては、スラブに連続鋳造し、1100〜1250℃に加熱して熱間圧延を行い熱延コイルとして、これを熱延板連続焼鈍・酸洗ラインで800〜1000℃の温度で焼鈍し酸洗を行い、次に、冷間圧延を施し冷延板として、仕上げ焼鈍と酸洗を行う方法が推奨される。詳細には以下の通りである。 As a highly efficient production method of the steel of the present invention, it is continuously cast on a slab, heated to 1100 to 1250 ° C. and hot-rolled to form a hot-rolled coil, and this is 800- A method is recommended in which annealing is performed at a temperature of 1000 ° C. and pickling is performed, and then cold rolling is performed to perform finish annealing and pickling as a cold-rolled sheet. Details are as follows.
まず、転炉、電気炉等と強攪拌・真空酸素脱炭処理(SS−VOD)あるいはアルゴン・酸素脱炭処理(AOD法)による2次精錬で上記の化学成分範囲に調整された溶鋼を溶製する。次いで、上記溶鋼から連続鋳造または造塊でスラブを溶製する。鋳造方法は、生産性、品質の面から連続鋳造が好ましい。 First, molten steel adjusted to the above chemical component range by secondary refining with a converter, electric furnace, etc. and strong stirring / vacuum oxygen decarburization treatment (SS-VOD) or argon / oxygen decarburization treatment (AOD method). To make. Next, the slab is melted from the molten steel by continuous casting or ingot forming. The casting method is preferably continuous casting in terms of productivity and quality.
鋳造により得られたスラブは、必要により1100〜1250℃に再加熱し、熱間圧延し、800〜1000℃の温度で熱延板焼鈍した後酸洗する。良好な機械的特性・加工性を得るためには、熱延板焼鈍温度は850〜950℃が好ましい。 If necessary, the slab obtained by casting is reheated to 1100 to 1250 ° C., hot-rolled, annealed at a temperature of 800 to 1000 ° C., and pickled. In order to obtain good mechanical properties and workability, the hot-rolled sheet annealing temperature is preferably 850 to 950 ° C.
酸洗された熱延板は冷間圧延、仕上げ焼鈍、冷却、酸洗の各工程を順次経て、冷延焼鈍板とする。 The pickled hot-rolled sheet is subjected to cold rolling, finish annealing, cooling, and pickling in order to form a cold-rolled annealed sheet.
冷間圧延時の圧下率は、伸び性、曲げ性、プレス成形性等の機械的特性を確保するために50%以上が好ましい。また、冷間圧延は1回または中間焼鈍を含む2回以上の冷間圧延としてもよい。冷間圧延、仕上げ焼鈍、酸洗の工程は繰り返し行ってもよい。 The rolling reduction during cold rolling is preferably 50% or more in order to ensure mechanical properties such as extensibility, bendability and press formability. Further, the cold rolling may be performed once or twice or more cold rolling including intermediate annealing. The steps of cold rolling, finish annealing, and pickling may be repeated.
さらに、冷延板連続焼鈍ラインで冷延板焼鈍と酸洗を行う。また、必要に応じて光輝焼鈍ラインで焼鈍を行っても良い。 Furthermore, cold-rolled sheet annealing and pickling are performed in a cold-rolled sheet continuous annealing line. Moreover, you may anneal with a bright annealing line as needed.
表1に示す発明例A1〜A5、および比較例C1〜C5の組成を有するフェライト系ステンレス鋼を30kg鋼塊に溶製した後、1150℃の温度に加熱して熱間圧延を行って板厚4.0mmの熱延板とした。次いで、950℃、アルゴンガス雰囲気で焼鈍した後、冷間圧延を行い、板厚0.8mmの冷延板を製作した。次いで、930℃、アルゴンガス雰囲気で焼鈍し、フッ酸と硝酸の混合酸を使用して酸洗を行った。 Thickness of the ferritic stainless steel having the composition of Invention Examples A1 to A5 and Comparative Examples C1 to C5 shown in Table 1 in a 30 kg steel ingot, heated to a temperature of 1150 ° C. and hot-rolled A 4.0 mm hot-rolled sheet was used. Next, after annealing in an argon gas atmosphere at 950 ° C., cold rolling was performed to produce a cold-rolled sheet having a thickness of 0.8 mm. Subsequently, it annealed in 930 degreeC and argon gas atmosphere, and pickled using the mixed acid of a hydrofluoric acid and nitric acid.
以上により得られた発明例A1〜A5、および比較例C1〜C5に対して、600番の研磨紙で表面を研磨し、供試材とした。 With respect to Invention Examples A1 to A5 and Comparative Examples C1 to C5 obtained as described above, the surface was polished with No. 600 polishing paper to obtain test materials.
供試材に対して、JIS H 8502に準じて塩水噴霧サイクル試験を行った。塩水噴霧サイクル試験は、5%NaCl噴霧(35℃、2hr)→乾燥(60℃、4hr、相対湿度20〜30%)→湿潤(40℃、2hr、相対湿度95%以上)を1サイクルとして、15サイクルを行った。 A salt spray cycle test was performed on the test material according to JIS H8502. In the salt spray cycle test, 5% NaCl spray (35 ° C., 2 hr) → drying (60 ° C., 4 hr, relative humidity 20-30%) → wet (40 ° C., 2 hr, relative humidity 95% or more) as one cycle, Fifteen cycles were performed.
次に、C1を除く残りの供試材に対して、同材(同一鋼種)でのTIG溶接部耐食性試験を行った。この試験では、それぞれの供試材から採取した2枚の板をTIG溶接で接合し、それらの表面を600番の研磨紙で研磨した後、上記の塩水噴霧サイクル試験を15サイクル行い、耐食性を調べた。 Next, the TIG welded part corrosion resistance test with the same material (same steel type) was performed with respect to the remaining specimens except C1. In this test, two plates taken from each test material were joined by TIG welding, their surfaces were polished with No. 600 abrasive paper, and then the above-mentioned salt spray cycle test was conducted for 15 cycles to improve the corrosion resistance. Examined.
次に、C1、C2、C3を除く残りの供試材に対して、SUS304との異鋼種TIG溶接部耐食性試験を行った。この試験では、それぞれの供試材から採取した板と0.8mm厚のSUS304をTIG溶接で接合し、それらの表面を600番の研磨紙で研磨した後、上記の塩水噴霧サイクル試験を15サイクル行い、耐食性を調べた。
以上により得られた結果を表1に示す。
Next, a different steel type TIG weld corrosion resistance test with SUS304 was performed on the remaining specimens excluding C1, C2, and C3. In this test, a plate taken from each test material and SUS304 having a thickness of 0.8 mm were joined by TIG welding, their surfaces were polished with No. 600 abrasive paper, and then the above-mentioned salt spray cycle test was repeated 15 cycles. The corrosion resistance was checked.
The results obtained as described above are shown in Table 1.
なお、表1において、各試験の判定基準は以下の通りである。
(1)塩水噴霧サイクル試験結果:15サイクル試験後の発錆面積が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(2)同材(同一鋼種)TIG溶接部耐食性試験結果:同材(同一鋼種)同士でTIG突き合わせ溶接を行い、表面を600番の研磨紙で研磨した後、塩水噴霧サイクル試験15サイクル後の溶接部(溶接金属、および熱影響部)の発錆率が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(3)SUS304との異鋼種TIG溶接部耐食性試験結果:SUS304とTIG突き合わせ溶接を行い、表面を600番の研磨紙で研磨した後、塩水噴霧サイクル試験15サイクル後の溶接部(溶接金属、および熱影響部)の発錆率が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
In Table 1, the criteria for each test are as follows.
(1) Salt spray cycle test result: The rusting area after the 15-cycle test was determined to be less than 20% as ◯ (pass) and 20% or more as x (fail).
(2) Corrosion resistance test result of the same material (same steel type) TIG welded part: TIG butt welding is performed between the same material (same steel type), the surface is polished with No. 600 abrasive paper, and after 15 cycles of salt spray cycle test As for the rusting rate of a welded part (welded metal and heat-affected zone), less than 20% was judged as ◯ (passed), and 20% or more was judged as x (failed).
(3) Corrosion resistance test result of different steel type TIG welded part with SUS304: SUS304 and TIG butt welded, the surface was polished with No. 600 abrasive paper, and then the welded part after 15 cycles of salt spray cycle test (welded metal, and The rusting rate of the heat-affected zone was determined to be less than 20% (good) and 20% or more as x (failed).
なお、(2)および(3)のTIG溶接は、表面、裏面ともにシールドガスとしてArガスを流し、溶加材は使用せず、裏ビードの幅が板厚程度になるように行った。これらの溶接条件は、溶接速度:600mm/min、溶接電圧:10〜12V、溶接電流:70〜110A、シールドガス量:表10リットル/min、裏5リットル/minである。 The TIG welding of (2) and (3) was performed such that Ar gas was flowed as a shielding gas on both the front and back surfaces, no filler material was used, and the width of the back bead was about the plate thickness. These welding conditions are welding speed: 600 mm / min, welding voltage: 10 to 12 V, welding current: 70 to 110 A, shielding gas amount: Table 10 liter / min, back 5 liter / min.
塩水噴霧サイクル試験においては、Cr含有量が16.5%と低い比較例C1は発錆面積が大きく耐食性が劣っていた。同材(同一鋼種)TIG溶接部耐食性試験においては、Ti含有量が0.07%と少ないC2、Ti%/(C%+N%)が6.2と低いC3は、発錆面積が大きく耐食性が劣っていた。SUS304との異鋼種TIG溶接部耐食性試験においては、Cr添加量が19.4%と高い比較例C4、および特許文献1に開示されるフェライト系ステンレス鋼板の比較例C5は、発錆面積が大きく耐食性が劣っていた。 In the salt spray cycle test, Comparative Example C1 having a low Cr content of 16.5% had a large rusting area and poor corrosion resistance. In the same material (same steel type) TIG weld corrosion resistance test, C2 with a low Ti content of 0.07% and C3 with a low Ti% / (C% + N%) of 6.2 have a large rusting area and corrosion resistance. Was inferior. In the different steel type TIG weld corrosion resistance test with SUS304, Comparative Example C4 with a high Cr addition amount of 19.4% and Comparative Example C5 of the ferritic stainless steel sheet disclosed in Patent Document 1 have a large rusting area. Corrosion resistance was poor.
以上より、本発明例では、母材の耐食性、同材(同一鋼種)TIG溶接部耐食性、SUS304との異鋼種TIG溶接部耐食性のいずれの特性にも優れることが明らかとなった。 From the above, it has been clarified that the invention examples are excellent in all of the properties of the corrosion resistance of the base material, the corrosion resistance of the same material (same steel type) TIG welded part, and the corrosion resistance of the different steel type TIG welded part with SUS304.
表2に示す発明例B1〜B6、および比較例D1〜D4(D4は特許文献1に開示されるフェライト系ステンレス鋼)の組成を有するフェライト系ステンレス鋼を150tonVODで溶製した後、連続鋳造でスラブに鋳造した。これを、1150℃の温度に加熱して熱間圧延を行って板厚4.0mmの熱延コイルとした。 After melting ferritic stainless steel having the composition of Invention Examples B1 to B6 shown in Table 2 and Comparative Examples D1 to D4 (D4 is a ferritic stainless steel disclosed in Patent Document 1) at 150 ton VOD, continuous casting is performed. Cast into a slab. This was heated to a temperature of 1150 ° C. and hot-rolled to obtain a hot-rolled coil having a plate thickness of 4.0 mm.
次いで、950℃の燃焼ガス雰囲気中で焼鈍した後、硫酸を用いて酸洗し、続いて、フッ酸と硝酸の混合酸を使用して酸洗を行って熱延焼鈍酸洗コイルとした。次いで、冷間圧延で板厚0.8mmとし、930℃の燃焼ガス雰囲気中で焼鈍した後、中性塩電解を行い、続いて、フッ酸と硝酸の混合酸を使用した酸洗を行い、冷延焼鈍酸洗コイルとした。得られた冷延焼鈍酸洗板の表面性状の判定を目視で行った。 Subsequently, after annealing in a combustion gas atmosphere at 950 ° C., pickling was performed using sulfuric acid, followed by pickling using a mixed acid of hydrofluoric acid and nitric acid to obtain a hot rolled annealing pickled coil. Next, after cold rolling to a plate thickness of 0.8 mm and annealing in a combustion gas atmosphere at 930 ° C., neutral salt electrolysis is performed, followed by pickling using a mixed acid of hydrofluoric acid and nitric acid, A cold-rolled annealed pickled coil was obtained. The surface properties of the obtained cold-rolled annealed pickling plate were visually determined.
さらに、得られた冷延焼鈍酸洗板に対して、600番の研磨紙で表面を研磨し、供試材とした。実施例1と同様にJIS H 8502に準じた塩水噴霧サイクル試験、同材(同一鋼種)TIG溶接部耐食性試験およびSUS304との異鋼種TIG溶接部耐食性試験を行った。 Furthermore, the surface of the obtained cold-rolled annealed pickling plate was polished with No. 600 polishing paper to obtain a test material. In the same manner as in Example 1, a salt spray cycle test according to JIS H8502, a TIG welded part corrosion resistance test of the same material (same steel type), and a different steel type TIG welded part corrosion resistance test with SUS304 were performed.
以上により得られた結果を表2に示す。 The results obtained as described above are shown in Table 2.
なお、表2において、各試験の判定基準は以下の通りである。
(1)塩水噴霧サイクル試験結果:15サイクル試験後の発錆面積が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(2)同材(同一鋼種)TIG溶接部耐食性試験結果:同材(同一鋼種)同士でTIG突き合わせ溶接を行い、表面を600番の研磨紙で研磨した後、塩水噴霧サイクル試験15サイクル後の溶接部(溶接金属、および熱影響部)の発錆率が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(3)SUS304との異鋼種TIG溶接部耐食性試験結果:SUS304とTIG突き合わせ溶接を行い、表面を600番の研磨紙で研磨した後、塩水噴霧サイクル試験15サイクル後の溶接部(溶接金属、および熱影響部)の発錆率が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(4)冷延焼鈍酸洗板の表面性状:表面欠陥(線ヘゲやチタンストリンガーによる、形状異常や白筋模様状色異常)がある部分の長さ(1m未満は1mに換算)の板全長に対する割合で判断し、欠陥率が、10%未満が○(合格)、10%以上が×(不合格)と判定した。
In Table 2, the criteria for each test are as follows.
(1) Salt spray cycle test result: The rusting area after the 15-cycle test was determined to be less than 20% as ◯ (pass) and 20% or more as x (fail).
(2) Corrosion resistance test result of the same material (same steel type) TIG welded part: TIG butt welding is performed between the same material (same steel type), the surface is polished with No. 600 abrasive paper, and after 15 cycles of salt spray cycle test As for the rusting rate of a welded part (welded metal and heat-affected zone), less than 20% was judged as ◯ (passed), and 20% or more was judged as x (failed).
(3) Corrosion resistance test result of different steel type TIG welded part with SUS304: SUS304 and TIG butt welded, the surface was polished with No. 600 abrasive paper, and then the welded part after 15 cycles of salt spray cycle test (welded metal, and The rusting rate of the heat-affected zone was determined to be less than 20% (good) and 20% or more as x (failed).
(4) Surface property of cold-rolled annealed pickling plate: A plate having a length of a surface defect (abnormal shape or white streak-like color abnormality due to line shaving or titanium stringer) (less than 1 m is converted to 1 m) Judgment was based on the ratio to the total length, and the defect rate was less than 10% (good), and 10% or more was judged as x (failed).
なお、(2)および(3)のTIG溶接は、表面、裏面ともシールドガスとしてArガスを流し、溶加材は使用せず、裏ビードの幅が板厚程度になるように行った。それらの溶接条件は、溶接速度:600mm/min、溶接電圧:10〜12V、溶接電流:70〜110A、シールドガス量:表10リットル/min、裏5リットル/minである。 The TIG welding of (2) and (3) was performed so that Ar gas was flowed as a shielding gas on both the front and back surfaces, no filler material was used, and the width of the back bead was about the plate thickness. The welding conditions are welding speed: 600 mm / min, welding voltage: 10 to 12 V, welding current: 70 to 110 A, shielding gas amount: Table 10 liter / min, back 5 liter / min.
表面性状の判定においては、Si添加量が0.07%と低い比較例D1、Ti添加量が0.28%と高い比較例D2および0.29%と高い比較例D4、Cu添加量が0.55%と高い比較例D3はいずれも冷延焼鈍酸洗板の表面性状が劣っていた。一方、発明例であるB1〜B6はいずれも表面性状が優れていた。塩水噴霧サイクル試験、同材(同一鋼種)TIG溶接部耐食性試験、およびSUS304との異鋼種TIG溶接部耐食性試験に関しては、発明例であるB1〜B6はいずれの試験においても良好な耐食性を示した。 In the determination of surface properties, Comparative Example D1 with a low Si addition amount of 0.07%, Comparative Example D2 with a high Ti addition amount of 0.28% and Comparative Example D4 with a high addition of 0.29%, and a Cu addition amount of 0 Comparative Example D3, which is as high as .55%, was inferior in surface properties of the cold-rolled annealed pickling plate. On the other hand, B1 to B6, which are invention examples, were all excellent in surface properties. Regarding the salt spray cycle test, the same material (same steel type) TIG welded portion corrosion resistance test, and the different steel type TIG welded portion corrosion resistance test with SUS304, the inventive examples B1 to B6 showed good corrosion resistance in any of the tests. .
表3に示す発明例E1〜E10およびG1〜G6の組成を有するフェライト系ステンレス鋼を150tonVODで溶製した後、連続鋳造でスラブに鋳造した。なお、E3、E6のB量、Ca量、E9、G4のB量およびG6のCa量はいずれも不可避的不純物レベルの含有量である。上記各スラブを、1150℃の温度に加熱して熱間圧延を行って板厚4.0mmの熱延コイルとした。 Ferritic stainless steel having the compositions of Invention Examples E1 to E10 and G1 to G6 shown in Table 3 was melted at 150 ton VOD, and then cast into a slab by continuous casting. In addition, the B amount of E3 and E6, the Ca amount, the B amount of E9 and G4, and the Ca amount of G6 are all inevitable impurity level contents. Each slab was heated to a temperature of 1150 ° C. and hot-rolled to form a hot-rolled coil having a plate thickness of 4.0 mm.
次いで、950℃の燃焼ガス雰囲気中で焼鈍した後、硫酸を用いて酸洗し、続いて、フッ酸と硝酸の混合酸を使用して酸洗を行って熱延焼鈍酸洗コイルとした。次いで、冷間圧延で板厚1.2mmとし、930℃の燃焼ガス雰囲気中で焼鈍した後、中性塩電解を行い、続いて、フッ酸と硝酸の混合酸を使用した酸洗を行い、冷延焼鈍酸洗コイルとした。 Subsequently, after annealing in a combustion gas atmosphere at 950 ° C., pickling was performed using sulfuric acid, followed by pickling using a mixed acid of hydrofluoric acid and nitric acid to obtain a hot rolled annealing pickled coil. Next, after cold rolling to a sheet thickness of 1.2 mm and annealing in a combustion gas atmosphere at 930 ° C., neutral salt electrolysis is performed, followed by pickling using a mixed acid of hydrofluoric acid and nitric acid, A cold-rolled annealed pickled coil was obtained.
この段階で、得られた冷延焼鈍酸洗板の表面性状の判定を目視で行った。冷間圧延により板厚を薄くしていくと表面のチタンストリンガーが伸ばされて周囲と同化して目立たなくなる。実施例2では冷間圧延で板厚を0.8mmとしたが、実施例3ではそれより厚い1.2mmとしたので、チタンストリンガーの存在を検出しやすい条件である。さらに、得られた冷延焼鈍酸洗板に対して、600番の研磨紙で表面を研磨し、供試材とした。実施例1、2と同様にJIS H 8502に準じた塩水噴霧サイクル試験、同材TIG溶接部耐食性試験、SUS304との異鋼種TIG溶接部耐食性試験と新たにTIG溶接部酸洗性試験を行った。
以上により得られた結果を表3に示す。
At this stage, the surface properties of the obtained cold-rolled annealed pickling plate were visually determined. When the plate thickness is reduced by cold rolling, the titanium stringers on the surface are stretched and become assimilated with the surroundings so that they are not noticeable. In Example 2, the plate thickness was set to 0.8 mm by cold rolling, but in Example 3, the thickness was set to 1.2 mm, which is a condition for easily detecting the presence of the titanium stringer. Furthermore, the surface of the obtained cold-rolled annealed pickling plate was polished with No. 600 polishing paper to obtain a test material. In the same manner as in Examples 1 and 2, a salt spray cycle test according to JIS H 8502, a TIG welded part corrosion resistance test of the same material, a TIG welded part corrosion resistance test with SUS304, and a new TIG welded pickling test were performed. .
The results obtained as described above are shown in Table 3.
なお、表3において、各試験の判定基準は以下の通りである。
(1)塩水噴霧サイクル試験結果:15サイクル試験後の発錆面積が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(2)同材(同一鋼種)TIG溶接部耐食性試験結果:同材(同一鋼種)同士でTIG突き合わせ溶接を行い、表面を600番の研磨紙で研磨した後、塩水噴霧サイクル試験15サイクル後の溶接部(溶接金属、および熱影響部)の発錆率が、20%未満が○(合格)、20%以上が×(不合格)と判定した。
(3)SUS304との異鋼種TIG溶接部耐食性試験結果:SUS304との異鋼種TIG突き合わせ溶接を行い、表面を600番の研磨紙で研磨した後、塩水噴霧サイクル試験15サイクル後の溶接部(溶接金属、および熱影響部)の発錆率が、20%未満を○(合格)、20%以上を×(不合格)と判定した。
(4)冷延焼鈍酸洗板の表面性状:表面欠陥(線ヘゲやチタンストリンガーによる、形状異常や白筋模様状色異常)がある部分の長さ(1m未満は1mに換算)の板全長に対する割合で判断し、欠陥率が、3%未満が◎(合格、特に優れている)、3%以上10%未満が○(合格)、10%以上が×(不合格)と判定した。
(5)TIG溶接部酸洗性試験:同材(同一鋼種)同士でTIG突合せ溶接を行い、20℃のフッ酸と硝酸の混合酸液(フッ酸5%、硝酸35%)に浸漬した。10分ごとに酸液から引き上げてナイロンブラシで溶接表側(直接溶接アークを当てた面)の酸化皮膜を擦り酸化皮膜の除去具合を観察した。浸漬時間合計が30分以下で酸化皮膜が除去できたものを◎(特に優れている)、30分超え120分以下で除去できたものを○(合格)、120分超えの浸漬でも酸化皮膜が残っていたものを×(不合格)と判定した。
In Table 3, the criteria for each test are as follows.
(1) Salt spray cycle test result: The rusting area after the 15-cycle test was determined to be less than 20% as ◯ (pass) and 20% or more as x (fail).
(2) Corrosion resistance test result of the same material (same steel type) TIG welded part: TIG butt welding is performed between the same material (same steel type), the surface is polished with No. 600 abrasive paper, and after 15 cycles of salt spray cycle test As for the rusting rate of a welded part (welded metal and heat-affected zone), less than 20% was judged as ◯ (pass), and 20% or more was judged as x (failed).
(3) Corrosion resistance test result of different steel type TIG welded portion with SUS304: After welding the different steel type TIG butt weld with SUS304 and polishing the surface with No. 600 abrasive paper, the welded portion after 15 cycles of salt spray cycle test (welding) When the rusting rate of the metal and the heat-affected zone was less than 20%, it was judged as ◯ (passed), and 20% or more was judged as x (failed).
(4) Surface property of cold-rolled annealed pickling plate: A plate having a length of a surface defect (abnormal shape or white streak-like color abnormality due to line shaving or titanium stringer) (less than 1 m is converted to 1 m) Judging by the ratio with respect to the total length, the defect rate was judged to be less than 3% ◎ (passed, particularly excellent), 3% to less than 10% ○ (pass), 10% or more x (fail).
(5) TIG welded portion pickling test: TIG butt welding was performed between the same materials (same steel types) and immersed in a mixed acid solution of hydrofluoric acid and nitric acid at 20 ° C. (5% hydrofluoric acid, 35% nitric acid). The removal of the oxide film was observed every 10 minutes by pulling it up from the acid solution and rubbing the oxide film on the welding front side (the surface directly exposed to the welding arc) with a nylon brush. ◎ (particularly excellent) that the oxide film was able to be removed in the total immersion time of 30 minutes or less, ○ (passed) that was able to be removed in excess of 30 minutes to 120 minutes or less, even if the immersion was over 120 minutes What remained was judged as x (failed).
なお、(2)、(3)および(5)のTIG溶接は、表面、裏面ともにシールドガスとしてArガスを流し、溶加材は使用せず、裏ビードの幅が板厚程度になるように行った。これらの溶接条件は、溶接速度:600mm/min、溶接電圧:10〜12V、溶接電流:80〜120A、シールドガス量:表10リットル/min、裏5リットル/minである。 In TIG welding of (2), (3) and (5), Ar gas is flowed as a shielding gas on both the front and back surfaces, no filler material is used, and the width of the back bead is about the plate thickness. went. These welding conditions are welding speed: 600 mm / min, welding voltage: 10 to 12 V, welding current: 80 to 120 A, shielding gas amount: Table 10 liter / min, back 5 liter / min.
表面性状の判定においては、Si%/Ti%≧1.3である、E1〜E10は表面欠陥率が3%未満で特に優れていた。Si%/Ti%<1.3である、G1〜G6は表面欠陥率が3%以上10%未満の合格であった。このように、Si%/Ti%≧1.3は表面性状の向上に有効である。 In the determination of surface properties, E1 to E10 with Si% / Ti% ≧ 1.3 were particularly excellent with a surface defect rate of less than 3%. G1 to G6 with Si% / Ti% <1.3 were acceptable with a surface defect rate of 3% or more and less than 10%. Thus, Si% / Ti% ≧ 1.3 is effective for improving the surface properties.
TIG溶接部酸洗性の判定においては、Si%/Cr%≧0.013のE2、E4〜E10およびG1、G2は酸洗時間が30分以下で特に優れていた。Si%/Cr%<0.013のE1、E3、およびG3〜G6は酸洗時間が30分超え120分以下の合格であった。このように、Si%/Cr%≧0.013はTIG溶接部の表面坂皮膜の酸洗性の向上に有効である。 In the determination of the pickling property of the TIG welded part, E2, E4 to E10, and G1 and G2 with Si% / Cr% ≧ 0.013 were particularly excellent when the pickling time was 30 minutes or less. E1, E3, and G3 to G6 with Si% / Cr% <0.013 passed the pickling time exceeding 30 minutes and not exceeding 120 minutes. Thus, Si% / Cr% ≧ 0.013 is effective in improving the pickling property of the surface slope film of the TIG welded part.
E1〜E10およびG1〜G6は、塩水噴霧試験、同材(同一鋼種)TIG溶接部耐食性試験、およびSUS304との異鋼種TIG溶接部耐食性試験において良好な耐食性を示した。 E1 to E10 and G1 to G6 showed good corrosion resistance in a salt spray test, the same material (same steel type) TIG weld corrosion resistance test, and a different steel type TIG weld corrosion resistance test with SUS304.
器物、厨房機器、建築内外装材、建築金具、エレベーター・エスカレーター内装材、家電、自動車部品等を中心に、耐食性が要求される部材として好適である。 It is suitable as a member that requires corrosion resistance, mainly for furniture, kitchen equipment, interior / exterior materials for buildings, building hardware, elevator / escalator interior materials, home appliances, automobile parts, and the like.
Claims (4)
Ti%/(C%+N%)≧8 (1)
ここで、C%、N%、Ti%は、それぞれC、N、Tiの含有量(質量%)を表す。 In mass%, C: 0.010% or less, Si: 0.15 to 0.60%, Mn: 0.5% or less, P: 0.04% or less, S: 0.01% or less, Al: 0 0.2% or less, Cr: 17.0 to 19.0%, Cu: 0.3 to 0.5%, Ni: 0.6% or less, Ti: 0.10 to 0.20%, N: 0.0. A ferritic stainless steel containing 015% or less, C + N: 0.02% or less, consisting of the balance Fe and inevitable impurities and satisfying the following formula (1).
Ti% / (C% + N%) ≧ 8 (1)
Here, C%, N%, and Ti% represent the contents (mass%) of C, N, and Ti, respectively.
Si%/Ti%≧1.3 (2)
ここで、Si%、Ti%は、それぞれSi、Tiの含有量(質量%)を表す。 The ferritic stainless steel according to claim 1 or 2, further satisfying the following formula (2) in addition to the component composition.
Si% / Ti% ≧ 1.3 (2)
Here, Si% and Ti% represent the contents (mass%) of Si and Ti, respectively.
Si%/Cr%≧0.013 (3)
ここで、Si%、Cr%は、それぞれSi、Crの含有量(質量%)を表す。 The ferritic stainless steel according to claim 1, further satisfying the following formula (3) in addition to the component composition.
Si% / Cr% ≧ 0.013 (3)
Here, Si% and Cr% represent the contents (mass%) of Si and Cr, respectively.
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