JP5696709B2 - Ferritic stainless steel and manufacturing method thereof - Google Patents
Ferritic stainless steel and manufacturing method thereof Download PDFInfo
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- 229910001220 stainless steel Inorganic materials 0.000 title claims description 31
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 31
- 238000005554 pickling Methods 0.000 claims description 25
- 229910000831 Steel Inorganic materials 0.000 claims description 23
- 239000010959 steel Substances 0.000 claims description 23
- 239000002245 particle Substances 0.000 claims description 9
- 238000000137 annealing Methods 0.000 claims description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 229910052710 silicon Inorganic materials 0.000 claims description 6
- 229910052758 niobium Inorganic materials 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 238000005097 cold rolling Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 229910052726 zirconium Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 230000007797 corrosion Effects 0.000 description 49
- 238000005260 corrosion Methods 0.000 description 49
- 230000000694 effects Effects 0.000 description 19
- 238000003466 welding Methods 0.000 description 17
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 14
- 239000007789 gas Substances 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 230000007423 decrease Effects 0.000 description 9
- 239000010935 stainless steel Substances 0.000 description 9
- 206010070834 Sensitisation Diseases 0.000 description 8
- 239000011324 bead Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 230000008313 sensitization Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 239000002244 precipitate Substances 0.000 description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 6
- 239000002253 acid Substances 0.000 description 6
- 238000010306 acid treatment Methods 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000004042 decolorization Methods 0.000 description 5
- 230000002950 deficient Effects 0.000 description 5
- 230000005611 electricity Effects 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 238000012805 post-processing Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 229920000742 Cotton Polymers 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000000368 destabilizing effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Landscapes
- Heat Treatment Of Sheet Steel (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Description
本発明は、ステンレス鋼本来の優れた耐食性を必要とするため、溶接部に生成するテンパーカラーを酸処理や電解処理によって除去して使用されている用途、例えば、電気温水器の貯湯用缶体などに使用されるフェライト系ステンレス鋼に関する。 Since the present invention requires the excellent corrosion resistance inherent to stainless steel, it is used by removing the temper collar generated in the welded portion by acid treatment or electrolytic treatment, for example, a hot water storage can of an electric water heater The present invention relates to ferritic stainless steel used for such as.
電気温水器の貯湯用缶体などにおいては、応力腐食割れの危険性がないことから、フェライト系ステンレス鋼が使用されている。缶体は通常、ＴＩＧ溶接によって組み立てられるが、ステンレス鋼の溶接においては、テンパーカラーと呼ばれる酸化膜の形成や溶接ビードへの窒素の侵入による鋭敏化によって、溶接部の耐食性が低下する場合がある。そのため、溶接施工時にはＡｒによるガスシールドを表裏両面から厳重に行い、テンパーカラーや鋭敏化が発生しない溶接方法が推奨される。 Ferritic stainless steel is used in cans for hot water storage of electric water heaters because there is no risk of stress corrosion cracking. The can body is usually assembled by TIG welding. However, in stainless steel welding, the corrosion resistance of the weld may be reduced due to the formation of an oxide film called a temper collar and the sensitization by the penetration of nitrogen into the weld bead. . For this reason, it is recommended to use a welding method in which a gas shield with Ar is strictly applied from the front and back sides at the time of welding construction so that no temper color or sensitization occurs.
しかし、近年では、缶体構造の複雑化にともなって、ガスシールドが十分に実施できない溶接部位が増えており、そういった部位の耐食性の低下が問題となっている。 However, in recent years, with the complexity of the can body structure, there are an increasing number of welded parts where gas shielding cannot be sufficiently performed, and the corrosion resistance of such parts has become a problem.
不十分なガスシールドによって溶接部に形成されたテンパーカラーは、電気温水器の貯湯用缶体内面などの厳しい腐食環境にさらされる用途では、酸処理や電解処理などの後処理によって除去されるのが一般的である。 Temper collars formed on welds due to insufficient gas shielding can be removed by post-treatment such as acid treatment or electrolytic treatment in applications exposed to severe corrosive environments such as the inner surface of hot water storage cans for electric water heaters. Is common.
しかし、缶体材料の高耐食性化にともなって後処理の負荷が増大している。特に熱影響部に生成するテンパーカラーの除去が困難となっている。このため、テンパーカラー除去性の向上による後処理負荷の低減が望まれている。 However, the post-processing load is increasing with the increase in corrosion resistance of the can body material. In particular, it is difficult to remove the temper color generated in the heat affected zone. For this reason, reduction of the post-processing load by improvement of temper color removability is desired.
特許文献１には溶接部の鋭敏化を抑制するために、ＴｉおよびＮｂを添加し、鋭敏化の原因となるＣやＮを安定化する技術が開示されている。 Patent Document 1 discloses a technique for stabilizing Ti and Nb to stabilize C and N that cause sensitization in order to suppress sensitization of a welded portion.
特許文献２にはＣｒ＋３．３Ｍｏ≧２２．０および４Ａｌ＋Ｔｉ≦０．３２を満たすことで、溶接部の耐食性を向上させる技術が開示されている。特許文献３には、高Ｃｒ化とＮｉ、Ｃｕの添加により、バックガスシールを行わないＴＩＧ溶接により形成された裏ビード側溶接部の耐食性を向上する技術が開示されている。 Patent Document 2 discloses a technique for improving the corrosion resistance of a welded portion by satisfying Cr + 3.3Mo ≧ 22.0 and 4Al + Ti ≦ 0.32. Patent Document 3 discloses a technique for improving the corrosion resistance of a back bead-side weld formed by TIG welding without performing back gas sealing by increasing Cr and adding Ni and Cu.
しかし、特許文献１に記載の発明では添加されたＮｂがテンパーカラーに濃縮し除去性を低下させるため、酸処理や電解処理の負荷が増大するという問題がある。 However, the invention described in Patent Document 1 has a problem that the load of acid treatment or electrolytic treatment increases because the added Nb is concentrated in a temper color to reduce removability.
一方、特許文献２および特許文献３に記載の発明ではテンパーカラーの耐食性が向上しているものの、ステンレス鋼本来の耐食性と比較するとテンパーカラーの除去なしでは耐食性に劣っており、水質の悪い厳しい使用環境では耐食性が不足する場合があった。これらの発明は、テンパーカラーの耐食性そのものを向上させた結果、その除去性が低下するため、溶接部の後処理を行うには適していないこととなる。 On the other hand, although the corrosion resistance of the temper color is improved in the inventions described in Patent Document 2 and Patent Document 3, the corrosion resistance is inferior without removing the temper color as compared with the original corrosion resistance of stainless steel, and the water quality is severely used. In some environments, corrosion resistance was insufficient. Since these inventions improve the corrosion resistance of the temper color itself, the removability of the temper color is lowered, and therefore, the invention is not suitable for the post-treatment of the welded portion.
従来技術の抱える上記のような問題点に鑑み、本発明は、フェライト系ステンレス鋼の溶接で、ガスシールドが不十分であるために、溶接ビードの鋭敏化やテンパーカラーの形成による耐食性の低下が起こりやすい溶接条件においても、耐食性とテンパーカラーの除去性に優れる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 the above-mentioned problems of the prior art, the present invention has insufficient gas shielding in the welding of ferritic stainless steel, so that the corrosion resistance is lowered due to the sensitization of the weld bead and the formation of the temper collar. It is an object of the present invention to provide a ferritic stainless steel having excellent corrosion resistance and temper color removability even under welding conditions that are likely to occur.
本発明では、上記課題を解決するために、テンパーカラーの除去性におよぼす各種添加元素の影響について鋭意研究を行った。 In the present invention, in order to solve the above-mentioned problems, intensive studies were conducted on the influence of various additive elements on the removability of the temper color.
２３質量％Ｃｒ−１．０質量％Ｍｏのフェライト系ステンレス鋼を基準に、各種添加元素を変化させた冷延焼鈍板を用いて、酸洗条件を種々変更した冷延焼鈍酸洗板を用意して、これに対してＴＩＧ溶接を行い、テンパーカラーの除去性を、１０質量％リン酸溶液を用いた電解処理により評価した。その結果、以下の知見を得た。 A cold-rolled annealed pickled steel plate with various changes in pickling conditions is prepared using a cold-rolled annealed steel plate with various additive elements changed based on 23 mass% Cr-1.0 mass% Mo ferritic stainless steel Then, TIG welding was performed on this, and the removability of the temper color was evaluated by electrolytic treatment using a 10% by mass phosphoric acid solution. As a result, the following knowledge was obtained.
（１）溶接部のテンパーカラーにＡｌ、Ｓｉ、Ｎｂ、Ｖが濃縮すると電解処理によるテンパーカラーの除去性が低下すること。 (1) When Al, Si, Nb, and V are concentrated in the temper collar of the weld, the temper color removability by electrolytic treatment is reduced.
（２）１μｍ以上の粒径のＴｉＮが鋼表面に分散して存在するとテンパーカラーの除去性が向上すること。 (2) When TiN having a particle diameter of 1 μm or more is dispersed and present on the steel surface, the temper color removability is improved.
（３）そのＴｉＮにＮｂＮが析出して存在するとよりテンパーカラーの除去性が向上すること。 (3) When NbN is precipitated and present on the TiN, the temper color removability is further improved.
（４）冷延焼鈍後の酸洗における酸洗減量を０．５ｇ／ｍ２以上とすることでテンパーカラーの除去性が向上すること。 (4) The removability of the temper color is improved by setting the pickling loss in pickling after cold rolling annealing to 0.5 g / m 2 or more.
本発明は、上記知見に基づいてなされたもので、その要旨は以下の通りである。 The present invention has been made based on the above findings, and the gist thereof is as follows.
［１］ 質量％でＣ：０．００１〜０．０３０％、Ｓｉ：０．０３〜０．３０％、Ｍｎ：０．０５〜０．３０％、Ｐ：０．０５％以下、Ｓ：０．０１％以下、Ｃｒ：２２．０％超２８．０％以下、Ｎｉ：０．０１％以上０．３０％未満、Ｍｏ：０．２〜３．０％、Ａｌ：０．０１〜０．１５％、Ｔｉ：０．３０％超０．８０％以下、Ｖ：０．００１〜０．０８０％、Ｎ：０．００１〜０．０５０％を含有し、残部がＦｅおよび不可避的不純物からなり、粒径１μｍ以上のＴｉＮが３０個／ｍｍ２以上の密度で、鋼表面に分布することを特徴とする溶接部の耐食性とテンパーカラーの除去性に優れたフェライト系ステンレス鋼。 [1] C: 0.001 to 0.030% in mass%, Si: 0.03 to 0.30%, Mn: 0.05 to 0.30%, P: 0.05% or less, S: 0 0.01% or less, Cr: more than 22.0% and 28.0% or less, Ni: 0.01% or more and less than 0.30%, Mo: 0.2-3.0%, Al: 0.01-0. 15%, Ti: more than 0.30% and 0.80% or less, V: 0.001 to 0.080%, N: 0.001 to 0.050%, with the balance being Fe and inevitable impurities A ferritic stainless steel excellent in corrosion resistance of welds and temper color removal, characterized in that TiN having a particle size of 1 μm or more is distributed on the steel surface at a density of 30 pieces / mm 2 or more.
［２］ 更に、質量％で、Ｎｂ：０．００１〜０．０５０％を含有し、粒径１μｍ以上のＴｉＮの表面にＮｂＮが析出していることを特徴とする、前記［１］に記載の溶接部の耐食性とテンパーカラーの除去性に優れたフェライト系ステンレス鋼。 [2] Further described in [1] above, characterized in that Nb: 0.001 to 0.050% by mass and NbN is precipitated on the surface of TiN having a particle size of 1 μm or more. Ferritic stainless steel with excellent corrosion resistance of welds and temper color removal.
［３］ 更に、質量％で、Ｃｕ：１．０％以下、Ｚｒ：１．０％以下、Ｗ：１．０％以下、Ｂ：０．０１％以下の中から選ばれる１種以上を含有することを特徴とする、前記［１］または［２］に記載の溶接部の耐食性とテンパーカラーの除去性に優れたフェライト系ステンレス鋼。 [3] Further, by mass%, Cu: 1.0% or less, Zr: 1.0% or less, W: 1.0% or less, B: 0.01% or less selected from B The ferritic stainless steel having excellent corrosion resistance and temper color removability according to the above [1] or [2].
［４］ 前記［１］乃至［３］の何れかに記載の成分組成を有する鋼を冷延焼鈍した後に、酸洗減量を０．５ｇ／ｍ２以上とする酸洗を行うことを特徴とする溶接部の耐食性とテンパーカラーの除去性に優れたフェライト系ステンレス鋼の製造方法。 [4] The steel having the component composition according to any one of [1] to [3] is subjected to cold rolling annealing, and then pickling to reduce the pickling weight to 0.5 g / m 2 or more. A method for producing ferritic stainless steel having excellent corrosion resistance of welded parts and excellent temper color removal.
本発明によれば、フェライト系ステンレス鋼の溶接で、ガスシールドが不十分であるために、溶接ビードの鋭敏化やがテンパーカラーの形成による耐食性の低下が起こりやすい溶接条件においても、耐食性とテンパーカラーの除去性に優れるフェライト系ステンレス鋼が得られる。 According to the present invention, since the gas shield is insufficient in the welding of ferritic stainless steel, the corrosion resistance and the temper can be improved even under welding conditions in which the weld bead is sensitized or the corrosion resistance is likely to deteriorate due to the formation of the temper collar. Ferritic stainless steel with excellent color removability can be obtained.
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.
１．成分組成について
本発明のフェライト系ステンレス鋼の成分組成を規定した理由を説明する。なお、成分％は全て質量％を意味する。
1. About a component composition The reason which prescribed | regulated the component composition of the ferritic stainless steel of this invention is demonstrated. In addition, all component% means the mass%.
Ｃ：０．００１〜０．０３０％
Ｃは鋼に不可避的に含まれる元素である。Ｃの含有量が多いと強度が向上し、少ないと加工性が向上する。十分な強度を得るためには０．００１％以上の含有が好ましいが、０．０３０％を超えて含有すると加工性の低下が顕著となるうえ、Ｃｒ炭化物を析出して局所的なＣｒ欠乏による耐食性の低下を起こしやすくなる。特に溶接部の鋭敏化の観点からは少ないほうが望ましい。よって、Ｃ量は０．００１〜０．０３０％の範囲とする。好ましくは、０．００２〜０．０１８％の範囲である。より好ましくは０．００２〜０．０１２％の範囲である。
C: 0.001 to 0.030%
C is an element inevitably contained in steel. When the C content is large, the strength is improved, and when the C content is low, the workability is improved. In order to obtain sufficient strength, the content is preferably 0.001% or more. However, if the content exceeds 0.030%, the workability deteriorates significantly, and Cr carbide is precipitated to cause local Cr deficiency. It tends to cause a decrease in corrosion resistance. In particular, a smaller amount is desirable from the viewpoint of sensitization of the weld. Therefore, the C content is in the range of 0.001 to 0.030%. Preferably, it is 0.002 to 0.018% of range. More preferably, it is 0.002 to 0.012% of range.
Ｓｉ：０．０３〜０．３０％
Ｓｉは脱酸に有用な元素であり、その効果は０．０３％以上の含有で得られる。しかし、溶接部のテンパーカラーに濃縮しテンパーカラーの除去性を低下させ、０．３０％を超えると除去が困難になる。よって、Ｓｉ量は０．０３〜０．３０％の範囲とする。好ましくは、０．０５〜０．１５％の範囲である。
Si: 0.03-0.30%
Si is an element useful for deoxidation, and the effect is obtained with a content of 0.03% or more. However, it is concentrated in the temper color of the welded portion to reduce the temper color removability, and if it exceeds 0.30%, the removal becomes difficult. Therefore, the Si amount is set to a range of 0.03 to 0.30%. Preferably, it is 0.05 to 0.15% of range.
Ｍｎ：０．０５〜０．３０％
Ｍｎは鋼の強度を高める効果がある。その効果は０．０５％以上の含有で得られるが、過剰の含有は腐食の起点となるＭｎＳの析出を促進し、耐食性を低下させるため、０．３０％以下の含有とする。よって、Ｍｎ量は０．０５〜０．３０％の範囲とする。好ましくは、０．０８〜０．２５％の範囲である。より好ましくは、０．０８〜０．２０％の範囲である。
Mn: 0.05-0.30%
Mn has the effect of increasing the strength of the steel. The effect can be obtained with a content of 0.05% or more, but excessive content promotes the precipitation of MnS, which is the starting point of corrosion, and lowers the corrosion resistance. Therefore, the content is made 0.30% or less. Therefore, the amount of Mn is made 0.05 to 0.30% of range. Preferably, it is 0.08 to 0.25% of range. More preferably, it is 0.08 to 0.20% of range.
Ｐ：０．０５％以下
Ｐは鋼に不可避的に含まれる元素であり、過剰な含有は溶接性を低下させ、粒界腐食を生じやすくさせる。よって、Ｐ量は０．０５％以下とする。好ましくは０．０３％以下である。
P: 0.05% or less P is an element inevitably contained in steel. Excessive content decreases weldability and easily causes intergranular corrosion. Therefore, the P content is 0.05% or less. Preferably it is 0.03% or less.
Ｓ：０．０１％以下
Ｓは鋼に不可避的に含まれる元素であるが、０．０１％超の含有はＣａＳやＭｎＳなどの水溶性硫化物の形成が促進され耐食性を低下させる。よって、Ｓ量は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 an element inevitably contained in steel, but the content exceeding 0.01% promotes the formation of water-soluble sulfides such as CaS and MnS and lowers the corrosion resistance. Therefore, the S content is 0.01% or less. Preferably it is 0.006% or less.
Ｃｒ：２２．０％超２８．０％以下
Ｃｒはステンレス鋼の耐食性を確保するために最も重要な元素である。本発明では、水質の悪い腐食環境の厳しい用途を想定しているため高い耐食性が必要であり、２２．０％超のＣｒの含有が必要である。さらに、２２．０％以下では溶接による酸化で表層のＣｒが減少する溶接部やＣｒを含むＮｂＮ周辺のＣｒ欠乏領域において十分な耐食性が得られない。一方で、２８．０％を超える含有は、加工性、製造性が低下するため、２８．０％以下の含有とする。よって、Ｃｒ量は２２．０％超２８．０％以下の範囲とする。好ましくは、２２．３〜２６．０％の範囲である。より好ましくは２２．３〜２４．５％の範囲である。
Cr: more than 22.0% and not more than 28.0% Cr is the most important element for ensuring the corrosion resistance of stainless steel. In this invention, since the severe use of the corrosive environment with bad water quality is assumed, high corrosion resistance is required, and content of Cr exceeding 22.0% is required. Furthermore, if it is 22.0% or less, sufficient corrosion resistance cannot be obtained in a welded portion where Cr on the surface layer decreases due to oxidation by welding or in a Cr-deficient region around NbN containing Cr. On the other hand, if the content exceeds 28.0%, workability and manufacturability deteriorate, so the content is made 28.0% or less. Therefore, the Cr content is in the range of more than 22.0% and 28.0% or less. Preferably, it is 22.3 to 26.0% of range. More preferably, it is 22.3 to 24.5% of range.
Ｎｉ：０．０１％以上０．３０％未満
Ｎｉはステンレス鋼の耐食性を向上させる元素であり、不動態皮膜が形成できず活性溶解が起こる腐食環境において腐食の進行を抑制する元素である。その効果は０．０１％以上の含有で得られる。しかし、０．３０％以上の含有では、加工性を低下させることに加えて、高価な元素であるためコストの増大を招く。よって、Ｎｉ量は０．０１％以上０．３０％未満の範囲である。好ましくは、０．０３〜０．２４％の範囲である。
Ni: 0.01% or more and less than 0.30% Ni is an element that improves the corrosion resistance of stainless steel, and is an element that suppresses the progress of corrosion in a corrosive environment where a passive film cannot be formed and active dissolution occurs. The effect is acquired by 0.01% or more of containing. However, if the content is 0.30% or more, in addition to lowering workability, it is an expensive element, which causes an increase in cost. Therefore, the amount of Ni is in the range of 0.01% or more and less than 0.30%. Preferably, it is 0.03 to 0.24% of range.
Ｍｏ：０．２〜３．０％
Ｍｏは不動態皮膜の再不動態化を促進し、ステンレス鋼の耐食性を向上する元素である。２２．０％超のＣｒとともに含有することによってその効果はより顕著となる。Ｍｏによる耐食性向上効果は０．２％以上の含有で得られる。しかし、含有量が３．０％を超えると強度が増加し、圧延負荷が大きくなるため製造性が低下する。よって、Ｍｏ量は０．２〜３．０％の範囲とする。好ましくは、０．６〜２．４％の範囲である。より好ましくは０．８〜１．８％の範囲である。
Mo: 0.2-3.0%
Mo is an element that promotes repassivation of the passive film and improves the corrosion resistance of stainless steel. The effect becomes more remarkable by containing together with more than 22.0% Cr. The effect of improving the corrosion resistance by Mo is obtained with a content of 0.2% or more. However, if the content exceeds 3.0%, the strength increases, and the rolling load increases, so the productivity decreases. Therefore, the Mo amount is in the range of 0.2 to 3.0%. Preferably, it is 0.6 to 2.4% of range. More preferably, it is 0.8 to 1.8% of range.
Ａｌ：０．０１〜０．１５％
Ａｌは脱酸に有用な元素であり、その効果は０．０１％以上の含有で得られる。しかし、溶接部のテンパーカラーに濃縮しテンパーカラーの除去性を低下させ、０．１５％を超えると除去が困難になる。よって、Ａｌ量は０．０１〜０．１５％の範囲とする。好ましくは、０．０１５〜０．０８％の範囲である。より好ましくは０．０２〜０．０５％の範囲である。
Al: 0.01 to 0.15%
Al is an element useful for deoxidation, and the effect is obtained with a content of 0.01% or more. However, it is concentrated in the temper color of the welded portion to reduce the temper color removal. If it exceeds 0.15%, the removal becomes difficult. Therefore, the Al content is in the range of 0.01 to 0.15%. Preferably, it is 0.015 to 0.08% of range. More preferably, it is 0.02 to 0.05% of range.
Ｔｉ：０．３０％超０．８０％以下
ＴｉはＣ、Ｎと優先的に結合してＣｒ炭窒化物の析出による耐食性の低下を抑制する元素である。本発明では、シールドガスから侵入したＮと結合して溶接ビードの鋭敏化を抑制するために重要な元素である。さらに、鋼の表面にＴｉＮを分散させることで、テンパーカラーの除去性を向上させる元素でもある。その効果は、Ｔｉ量が０．３０％超で得られる。しかし、含有量が０．８０％を超えると加工性が低下する。よって、Ｔｉ量は０．３０超０．８０％以下の範囲である。好ましくは、０．３２〜０．６０％の範囲である。より好ましくは０．３３〜０．５０％の範囲である。
Ti: more than 0.30% and not more than 0.80% Ti is an element that preferentially bonds with C and N and suppresses a decrease in corrosion resistance due to the precipitation of Cr carbonitride. In the present invention, it is an important element for suppressing sensitization of the weld bead by combining with N that has entered from the shielding gas. Further, it is an element that improves the removability of the temper color by dispersing TiN on the surface of the steel. The effect is obtained when the Ti content exceeds 0.30%. However, if the content exceeds 0.80%, the workability decreases. Therefore, the Ti amount is in the range of more than 0.30 and 0.80% or less. Preferably, it is 0.32 to 0.60% of range. More preferably, it is 0.33 to 0.50% of range.
Ｖ：０．００１〜０．０８０％
Ｖは耐食性を向上させる元素であり、その効果は、０．００１％以上の含有で得られる。しかし、０．０８０％を超える過剰な含有は、溶接によるテンパーカラーの形成を促進するため、その除去性が低下する。よって、Ｖ量は０．００１〜０．０８０％の範囲とする。好ましくは、０．００２〜０．０６０％の範囲である。より好ましくは０．００５〜０．０４０％の範囲である。
V: 0.001 to 0.080%
V is an element that improves the corrosion resistance, and the effect is obtained with a content of 0.001% or more. However, an excessive content exceeding 0.080% promotes the formation of a temper color by welding, so that its removability is lowered. Therefore, the V amount is in the range of 0.001 to 0.080%. Preferably, it is 0.002 to 0.060% of range. More preferably, it is 0.005 to 0.040% of range.
Ｎ：０．００１〜０．０５０％
Ｎは、Ｃと同様に鋼に不可避的に含まれる元素であり、固溶強化により鋼の強度を上昇させる効果がある。さらに、ＴｉＮ、ＮｂＮを析出し、テンパーカラーの除去性を向上させる元素でもある。その効果は含有量が０．００１％以上で得られる。しかし、ＮｂやＴｉで安定化できないほどの多量の含有は、Ｃｒ窒化物を析出して耐食性を低下させるため、０．０５０％以下の含有とする。よって、Ｎ量は０．００１〜０．０５０％の範囲とする。好ましくは、０．００２〜０．０２５％の範囲である。より好ましくは０．００２〜０．０１８％の範囲である。
N: 0.001 to 0.050%
N is an element that is inevitably contained in steel like C, and has the effect of increasing the strength of the steel by solid solution strengthening. Furthermore, TiN and NbN are also precipitated to improve the temper color removability. The effect is obtained when the content is 0.001% or more. However, if the content is too large to be stabilized by Nb or Ti, Cr nitride is precipitated and the corrosion resistance is lowered, so the content is 0.050% or less. Therefore, the N amount is set in the range of 0.001 to 0.050%. Preferably, it is 0.002 to 0.025% of range. More preferably, it is 0.002 to 0.018% of range.
鋼の表面に粒径が１μｍ以上のＴｉＮの密度分布：３０個／ｍｍ２以上
テンパーカラーの除去は通常、酸処理または電解処理によって行われる。テンパーカラーはＳｉ、Ａｌ、Ｃｒといった元素の酸化物で形成されている。これらの酸化物は酸や電位に対して地鉄よりも安定で溶解しにくい。したがって、酸処理などによってテンパーカラーを除去する場合、テンパーカラー直下のＣｒ欠乏領域が溶解して、テンパーカラーを剥離する形で除去が進行する。このとき、テンパーカラーが地鉄の表面を一様に緻密に保護していると、酸や電解液がＣｒ欠乏領域まで到達せず、テンパーカラーの除去性が低下する。
Density distribution of TiN having a particle size of 1 μm or more on the surface of steel: 30 pieces / mm 2 or more The temper color is usually removed by acid treatment or electrolytic treatment. The temper collar is formed of an oxide of an element such as Si, Al, or Cr. These oxides are more stable and less soluble than the iron for acid and electric potential. Therefore, when the temper color is removed by acid treatment or the like, the removal proceeds in a form in which the Cr-deficient region immediately below the temper color is dissolved and the temper color is peeled off. At this time, if the temper color uniformly and densely protects the surface of the base iron, the acid or the electrolyte does not reach the Cr-deficient region, and the temper color removability is lowered.
テンパーカラーの厚さは数百ｎｍであるのが一般的である。粒径が１μｍ以上となる粗大なＴｉＮが表面に存在した場合、テンパーカラーを突き破ってＴｉＮが存在することになるため、ＴｉＮ周囲がテンパーカラーの欠陥となり、そこを通して酸や電解液が地鉄まで浸透し除去性が向上する。この除去性向上は、表面に粒径が１μｍ以上のＴｉＮが３０個／ｍｍ２以上の密度で分布することで得られる。好ましくは３５個／ｍｍ２以上〜１５０個／ｍｍ２の密度での分布とする。 The thickness of the temper color is generally several hundred nm. When coarse TiN with a particle size of 1 μm or more is present on the surface, TiN will break through the temper color, and therefore the temper color defect around the TiN will pass through the acid and electrolyte to the iron. Penetration and improved removability. This improvement in removability can be obtained by distributing TiN having a particle size of 1 μm or more on the surface with a density of 30 pieces / mm 2 or more. The distribution is preferably 35 / mm 2 or more to 150 / mm 2 .
以上が本発明のフェライト系ステンレス鋼の基本化学成分であり、残部はＦｅ及び不可避的不純物であるが、更に、Ｎｂを下記範囲で含有してもよい。 The above are the basic chemical components of the ferritic stainless steel of the present invention, and the balance is Fe and inevitable impurities, but Nb may further be contained in the following range.
Ｎｂ：０．００１〜０．０５０％
Ｎｂは、Ｃ、Ｎと優先的に結合してＣｒ炭窒化物の析出による耐食性の低下を抑制する元素であるが、本発明では、溶接部のテンパーカラーに濃縮し、その除去性を低下させる元素である。０．０５０％を超えて含有すると溶接部のテンパーカラーの除去性低下が顕著となる。よって、Ｎｂの含有量は０．０１０％以下とすることが好ましい。一方で、微量のＮｂを添加した場合には、ＮｂＮがＴｉＮに付着して析出する。ＮｂＮが析出する時には、Ｃｒと複合析出する（ＮｂＮのなかにＣｒが取り込まれる）ため、ＴｉＮの周囲に、耐食性には影響しない程度のわずかなＣｒ欠乏領域が形成される。
Nb: 0.001 to 0.050%
Nb is an element that preferentially binds to C and N and suppresses a decrease in corrosion resistance due to the precipitation of Cr carbonitride. In the present invention, Nb is concentrated in the temper collar of the welded portion, thereby reducing its removability It is an element. If the content exceeds 0.050%, the temper color removability of the welded portion is significantly lowered. Therefore, the Nb content is preferably 0.010% or less. On the other hand, when a small amount of Nb is added, NbN adheres to TiN and precipitates. When NbN is precipitated, it is combined with Cr (Cr is taken into NbN), so that a slight Cr-deficient region is formed around TiN so as not to affect the corrosion resistance.
テンパーカラーは地鉄のＣｒ含有量が少ないほど除去しやすい。したがって、ＮｂＮが付着したＴｉＮの周囲に形成されるテンパーカラーは、地鉄のＣｒ含有量が少ないために、より除去しやすくなる。この効果はＮｂ量が０．００１％以上で得られる。よって、Ｎｂ量は０．００１〜０．０５０％の範囲とすることが好ましい。より好ましくは、０．００２〜０．００８％の範囲である。 The temper color is easier to remove as the Cr content of the base iron is smaller. Therefore, the temper collar formed around TiN to which NbN is adhered becomes easier to remove because the Cr content of the ground iron is small. This effect is obtained when the Nb content is 0.001% or more. Therefore, the Nb content is preferably in the range of 0.001 to 0.050%. More preferably, it is 0.002 to 0.008% of range.
１μｍ以上のＴｉＮに付着してＮｂＮが析出
前記説明の通り微量のＮｂを含有することでＴｉＮ周囲のテンパーカラーがより除去しやすくなる。ＮｂＮはＴｉＮの表面を析出核として析出し、その厚さは５〜５０ｎｍが好ましい。本発明の成分範囲では、ＮｂＮにはＣｒが含まれるが、テンパーカラーの除去性を向上させるためには、ＮｂＮに含まれるＣｒとＮｂの比Ｃｒ／Ｎｂは、０．０５〜０．５０の範囲が好ましい。
NbN is deposited by adhering to TiN of 1 μm or more. As described above, the temper color around TiN is more easily removed by containing a small amount of Nb. NbN precipitates with the surface of TiN as a precipitation nucleus, and the thickness is preferably 5 to 50 nm. In the component range of the present invention, NbN contains Cr, but in order to improve the removability of the temper color, the Cr / Nb ratio Cr / Nb contained in NbN is 0.05 to 0.50. A range is preferred.
更に、耐食性向上、加工性改善の観点からＣｕ、Ｚｒ、Ｗ、Ｂの中から選らばれる１種以上を選択元素として下記の範囲で含有してもよい。 Furthermore, from the viewpoint of improving corrosion resistance and improving workability, one or more selected from Cu, Zr, W, and B may be contained in the following ranges as selective elements.
Ｃｕ：１．０％以下
Ｃｕはステンレス鋼の耐食性を向上させる元素であり、その効果を得るには０．０１％以上の含有が好ましい。しかし、過剰な含有は不動態維持電流を増加させて不動態皮膜を不安定とし、耐食性を低下させる作用がある。よって、Ｃｕを含有する場合、その量は１．０％以下とすることが好ましい。より好ましくは０．６％以下である。
Cu: 1.0% or less Cu is an element that improves the corrosion resistance of stainless steel. To obtain the effect, Cu is preferably contained in an amount of 0.01% or more. However, excessive inclusion has the effect of increasing the passive maintenance current, destabilizing the passive film, and reducing the corrosion resistance. Therefore, when it contains Cu, it is preferable that the quantity shall be 1.0% or less. More preferably, it is 0.6% or less.
Ｚｒ：１．０％以下
ＺｒはＣ、Ｎと結合して、鋭敏化を抑制する効果がある。その効果を得るには０．０１％以上の含有が好ましい。しかし、過剰な含有は加工性を低下させるうえ、非常に高価な元素であるためコストの増大を招く。よって、Ｚｒを含有する場合、その量は１．０％以下とすることが好ましい。より好ましくは０．６％以下である。さらに好ましくは０．２％以下である。
Zr: 1.0% or less Zr combines with C and N and has an effect of suppressing sensitization. In order to obtain the effect, the content is preferably 0.01% or more. However, excessive content lowers workability and increases the cost because it is an extremely expensive element. Therefore, when Zr is contained, the amount is preferably 1.0% or less. More preferably, it is 0.6% or less. More preferably, it is 0.2% or less.
Ｗ：１．０％以下
ＷはＭｏと同様に耐食性を向上する効果がある。その効果を得るには０．０１％以上の含有が好ましい。しかし、過剰の含有は強度を上昇させ、製造性を低下させる。よって、Ｗを含有する場合は、その量は１．０％以下とすることが好ましい。より好ましくは０．６％以下である。さらに好ましくは０．２％以下である。
W: 1.0% or less W, like Mo, has an effect of improving corrosion resistance. In order to obtain the effect, the content is preferably 0.01% or more. However, excessive content increases strength and decreases manufacturability. Therefore, when it contains W, it is preferable that the quantity shall be 1.0% or less. More preferably, it is 0.6% or less. More preferably, it is 0.2% or less.
Ｂ：０．０１％以下
Ｂは二次加工脆性を改善する元素であり、その効果を得るには、０．０００１％以上の含有が好ましい。しかし、過剰の含有は、固溶強化による延性低下を引き起こす。よってＢを含有する場合は、その量は０．０１％以下とすることが好ましい。より好ましくは０．００５％以下である。さらに好ましくは０．００２％以下である。
B: 0.01% or less B is an element that improves secondary work brittleness, and in order to obtain the effect, the content is preferably 0.0001% or more. However, excessive inclusion causes a decrease in ductility due to solid solution strengthening. Therefore, when it contains B, it is preferable that the quantity shall be 0.01% or less. More preferably, it is 0.005% or less. More preferably, it is 0.002% or less.
２．製造方法について
次に、本発明のフェライト系ステンレス鋼の製造方法について説明する。
以下に本発明のフェライト系ステンレス鋼の好適な製造方法を述べる。
2. About a manufacturing method Next, the manufacturing method of the ferritic stainless steel of this invention is demonstrated.
A suitable method for producing the ferritic stainless steel of the present invention will be described below.
上記化学組成のステンレス鋼を、１１００℃〜１３００℃に加熱後、仕上温度を７００℃〜１０００℃、巻取温度を５００℃〜９００℃として熱間圧延を施し、板厚を２．０ｍｍ〜５．０ｍｍとする。こうして作製した熱間圧延鋼帯を、８００℃〜１０００℃の温度で焼鈍し酸洗を行い、次に、冷間圧延を行い、８００℃〜９００℃の温度で１ｍｉｎ以上の冷延板焼鈍を行う。ＴｉＮ周囲のＣｒ欠乏領域の回復を抑制するため、冷延板焼鈍後の冷却速度は５００℃までを５℃／ｓ以上とする。より好ましくは１０℃／ｓ以上である。 After the stainless steel having the above chemical composition is heated to 1100 ° C. to 1300 ° C., hot rolling is performed at a finishing temperature of 700 ° C. to 1000 ° C. and a winding temperature of 500 ° C. to 900 ° C., and the plate thickness is 2.0 mm to 5 mm. 0.0 mm. The hot-rolled steel strip thus produced is annealed at a temperature of 800 ° C. to 1000 ° C. and pickled, then cold-rolled, and subjected to cold rolled sheet annealing at a temperature of 800 ° C. to 900 ° C. for 1 min or more. Do. In order to suppress recovery of the Cr-deficient region around TiN, the cooling rate after the cold-rolled sheet annealing is set to 5 ° C./s or more up to 500 ° C. More preferably, it is 10 ° C./s or more.
冷延板焼鈍後には酸洗を行い、酸洗減量で０．５ｇ／ｍ２以上、鋼板表面を両面あわせて０．０５μｍ以上除去し、鋼板表面にＴｉＮを出現させる。この酸洗によって、鋼板表面に存在するＴｉＮを３０個／ｍｍ２以上とする。酸洗方法には、硫酸酸洗、硝酸酸洗、硝弗酸酸洗などの酸浸漬、および／または、中性塩電解酸洗、硝塩酸電解酸洗などの電解酸洗が含まれる。これらの酸洗方法を組み合わせてもよい。また、酸洗以外の方法によって鋼板表面にＴｉＮを出現させてもよい。 After cold-rolled sheet annealing, pickling is performed, pickling reduction is 0.5 g / m 2 or more, and the steel sheet surface is removed by 0.05 μm or more on both sides, and TiN appears on the steel sheet surface. By this pickling, TiN existing on the surface of the steel sheet is set to 30 pieces / mm 2 or more. Acid pickling methods include acid pickling such as sulfuric acid pickling, nitric acid pickling, and nitric hydrofluoric acid pickling, and / or electrolytic pickling such as neutral salt electrolytic pickling and nitric hydrochloric acid electrolytic pickling. These pickling methods may be combined. Moreover, you may make TiN appear on the steel plate surface by methods other than pickling.
以下、実施例に基づいて本発明を説明する。 Hereinafter, the present invention will be described based on examples.
表１に示すステンレス鋼を真空溶製し、１２００℃に加熱したのち、板厚４ｍｍまで熱間圧延し、８５０〜９５０℃の範囲で焼鈍し、酸洗によりスケールを除去した。さらに、板厚０．８ｍｍまで冷間圧延し、８５０℃〜９００℃の範囲で１ｍｉｎ以上焼鈍した。焼鈍後の冷却速度は焼鈍温度から５００℃までを５〜５０℃／ｓとした。その後、硝酸１５ｍａｓｓ％−塩酸１０ｍａｓｓ％の混合酸中で電気量／面積２０〜１５０Ｃ／ｄｍ２の電解酸洗を行い、供試材とした。冷却速度、電解酸洗の電気量／面積、酸洗減量および板厚減少を表２に示す。 Stainless steel shown in Table 1 was vacuum-melted and heated to 1200 ° C., then hot-rolled to a plate thickness of 4 mm, annealed in the range of 850 to 950 ° C., and the scale was removed by pickling. Furthermore, it cold-rolled to plate | board thickness 0.8mm, and annealed for 1 minute or more in the range of 850 to 900 degreeC. The cooling rate after annealing was 5 to 50 ° C./s from the annealing temperature to 500 ° C. Thereafter, electrolytic pickling was carried out at a quantity of electricity / area of 20 to 150 C / dm 2 in a mixed acid of 15 mass% nitric acid and 10 mass% hydrochloric acid to obtain a test material. Table 2 shows the cooling rate, the amount of electricity / area of electrolytic pickling, the amount of pickling reduction, and the reduction in sheet thickness.
作製した供試材の表面をＳＥＭにより観察し、表面に存在するＴｉＮの分布密度を求めた。ＳＥＭにより供試材表面の任意の１００μｍ×１００μｍの範囲を１０視野観察し、表面の析出物を観察した。観察された析出物のうち、粒径が１μｍ以上で、立方晶に近い形状の析出物をＴｉＮとみなした。１０視野のＴｉＮの個数を数えて平均し、１ｍｍ２あたりのＴｉＮの個数を算出した。粒径の測定方法は、ＳＥＭによって観察されたＴｉＮの長径と短径をそれぞれ測定し、その平均を粒径とした。 The surface of the produced test material was observed by SEM, and the distribution density of TiN existing on the surface was determined. Ten fields of view of an arbitrary 100 μm × 100 μm range on the surface of the test material were observed by SEM, and precipitates on the surface were observed. Among the observed precipitates, a precipitate having a particle size of 1 μm or more and a shape close to a cubic crystal was regarded as TiN. The number of TiNs in 10 fields was counted and averaged to calculate the number of TiNs per 1 mm 2 . The particle diameter was measured by measuring the major and minor diameters of TiN observed by SEM, and taking the average as the grain diameter.
ＴｉＮをより詳細に解析するため、析出物を電解抽出し、ＴＥＭによる観察を行った。ＥＤＳによる元素分析の結果、１μｍ以上の粗大なＴｉＮに付着するように５〜５０ｎｍの厚さのＮｂＮの析出が確認された。析出物の核となるＴｉＮにはほとんどＣｒが認められなかったが、ＴｉＮに付着したＮｂＮからはＣｒの存在が確認された。ＮｂＮに含まれるＣｒとＮｂの比Ｃｒ／ＮｂをＴＥＭのＥＤＳにより分析すると、いずれのＮｂＮもＣｒ／Ｎｂが０．０５〜０．５０の範囲に含まれた。 In order to analyze TiN in more detail, the precipitate was electrolytically extracted and observed by TEM. As a result of elemental analysis by EDS, it was confirmed that NbN having a thickness of 5 to 50 nm was deposited so as to adhere to coarse TiN of 1 μm or more. Although almost no Cr was observed in TiN as the nucleus of the precipitate, the presence of Cr was confirmed from NbN adhering to TiN. When the ratio Cr / Nb of Cr to Nb contained in NbN was analyzed by EDS of TEM, all NbN contained Cr / Nb in the range of 0.05 to 0.50.
作製した供試材にビードオンプレートのＴＩＧ溶接を行った。溶接電流は９０Ａ、溶接速度は６０ｃｍ／ｍｉｎとした。シールドガスは、表側（トーチ側）のみ、１００％Ａｒを使用し、裏側はシールドガスを使用しなかった。シールドガスの流量は１５Ｌ／ｍｉｎとした。表側の溶接ビードの幅はおよそ４ｍｍであった。 TIG welding of the bead-on-plate was performed on the prepared test material. The welding current was 90 A and the welding speed was 60 cm / min. As the shielding gas, 100% Ar was used only on the front side (torch side), and no shielding gas was used on the back side. The flow rate of the shielding gas was 15 L / min. The width of the front side weld bead was approximately 4 mm.
作製した溶接ビードの表裏のテンパーカラーに対して、１０質量％リン酸溶液を含ませた脱脂綿を接触させ、１〜１５Ｃ／ｄｍ２の電気量／面積で電解処理を行った。電解処理後にＧＤＳにより溶接部の深さ方向の元素分布を測定した。ＳｉやＡｌなどのテンパーカラーに濃縮する元素が、表層に地鉄よりも多く認められたものをテンパーカラー残り有りと判断した。結果を表２に示す。 Absorbent cotton containing a 10% by mass phosphoric acid solution was brought into contact with the temper collars on the front and back of the produced weld bead, and electrolytic treatment was performed at an electric quantity / area of 1 to 15 C / dm 2 . After the electrolytic treatment, the element distribution in the depth direction of the weld was measured by GDS. It was judged that there was a remaining temper color when the elements concentrated in the temper color such as Si and Al were recognized in the surface layer more than the base iron. The results are shown in Table 2.
６Ｃ／ｄｍ２以下の電気量／面積でもテンパーカラー残りがなかったものを◎（合格、特に優れる）、１０Ｃ／ｄｍ２以下の電気量／面積でテンパーカラー残りがなかったものを○（合格）、１０Ｃ／ｄｍ２超の電気量／面積でもテンパーカラー残りがあったものを×（不合格）とした。酸洗減量が不十分で鋼板表面のＴｉＮの個数が３０個／ｍｍ２より少ないＮｏ．１、およびＴｉ含有量が本発明範囲より少なく鋼板表面のＴｉＮの個数が３０個／ｍｍ２より少ないＮｏ．２０と、Ｓｉ、Ａｌ、Ｎｂ、Ｖのいずれかが本発明の成分範囲よりも多いＮｏ．１８、Ｎｏ．１９、Ｎｏ．２２、Ｎｏ．２３で１０Ｃ／ｄｍ２超の電気量／面積でもテンパーカラー残りが確認された。すべての成分が本発明の成分範囲内でありＮｂＮの析出が確認されたＮｏ．１３、Ｎｏ．１６、Ｎｏ．１７、および、Ｃｒが本発明の成分範囲以下であるものの、ＮｂＮの析出が確認されたＮｏ．２１では６Ｃ／ｄｍ２の電気量／面積でテンパーカラー残りがなく、テンパーカラーの除去性がより良好であった。 ◎ (pass, especially excellent) with no temper color remaining even at 6C / dm 2 or less of electricity / area ◯ (pass) with no temper color remaining at 10C / dm 2 or less of electricity / area Even if the amount of electricity / area was more than 10 C / dm 2, the remaining temper color was defined as x (failed). No. of pickling loss is insufficient and the number of TiN on the steel sheet surface is less than 30 / mm 2 . No. 1 and No. 1 in which the Ti content is less than the range of the present invention and the number of TiNs on the steel sheet surface is less than 30 pieces / mm 2 . No. 20 and any of Si, Al, Nb, and V is larger than the component range of the present invention. 18, no. 19, no. 22, no. 23, the remaining temper color was confirmed even with an electric quantity / area exceeding 10 C / dm 2 . All the components are within the component range of the present invention, and NbN precipitation was confirmed. 13, no. 16, no. No. 17 and Cr No. in which the precipitation of NbN was confirmed although Cr was not more than the component range of the present invention. In No. 21, there was no remaining temper color at an electric amount / area of 6 C / dm 2 , and the temper color removal property was better.
供試材の溶接ビードを１０質量％リン酸溶液にて電解処理したのち、５０ｍｍの溶接ビードを含む試験片を採取し、８０℃の５質量％ＮａＣｌに１週間浸漬した。浸漬後に溶接部に腐食が発生した供試材を、浸漬試験による腐食有りとした。結果を表２に示す。腐食のあったものを×（不合格）、腐食のなかったものを○（合格）とした。テンパーカラー残りのあったＮｏ．１、Ｎｏ．１８、Ｎｏ．１９、Ｎｏ．２０、Ｎｏ．２２、Ｎｏ．２３ではいずれも腐食が発生し、耐食性が悪いことが確認された。Ｃｒの含有量が本発明からはずれるＮｏ．２１でも腐食が発生し、耐食性が悪いことが確認された。
本発明例であるＮｏ．２〜Ｎｏ．１７ではいずれもテンパーカラー残りがなく耐食性が良好であった。
After subjecting the weld bead of the test material to electrolytic treatment with a 10% by mass phosphoric acid solution, a test piece containing a 50 mm weld bead was collected and immersed in 5% by mass NaCl at 80 ° C. for 1 week. A test material in which corrosion occurred in the weld after immersion was regarded as having corrosion due to the immersion test. The results are shown in Table 2. Those with corrosion were evaluated as x (failed), and those without corrosion were evaluated as ◯ (accepted). No. with temper color remaining. 1, no. 18, no. 19, no. 20, no. 22, no. In No. 23, corrosion occurred and it was confirmed that the corrosion resistance was poor. No. Cr content deviates from the present invention. No. 21 also corroded and it was confirmed that the corrosion resistance was poor.
No. as an example of the present invention. 2-No. In No. 17, no temper color residue was left and the corrosion resistance was good.
本発明で得られるフェライト系ステンレス鋼は、溶接によって構造体の作製が行われ、溶接後に酸処理などによってテンパーカラーの除去が行われる用途、たとえば、電気温水器の貯湯用缶体材料などへの適用に好適である。 Ferritic stainless steel obtained in the present invention is used for applications in which a structure is produced by welding and the temper color is removed by acid treatment after welding, for example, a hot water storage can body material for an electric water heater. Suitable for application.
Claims (4)
鋼を冷延焼鈍した後に、酸洗減量を０．５ｇ／ｍ２以上とする酸洗を行うことを特徴とするフェライト系ステンレス鋼の製造方法。 A method for producing a ferritic stainless steel according to any one of claims 1 to 3 ,
A method for producing a ferritic stainless steel, characterized in that after cold-rolling annealing of steel , pickling is performed so that the pickling loss is 0.5 g / m 2 or more.
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