JP6105996B2 - Low Ni austenitic stainless steel sheet and processed product obtained by processing the steel sheet - Google Patents
Low Ni austenitic stainless steel sheet and processed product obtained by processing the steel sheet Download PDFInfo
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- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims description 10
- 229910000831 Steel Inorganic materials 0.000 title description 41
- 239000010959 steel Substances 0.000 title description 41
- 229910000734 martensite Inorganic materials 0.000 claims description 51
- 229910001566 austenite Inorganic materials 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 6
- 229910001220 stainless steel Inorganic materials 0.000 claims description 6
- 239000010935 stainless steel Substances 0.000 claims description 4
- 238000005336 cracking Methods 0.000 description 26
- 239000000047 product Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 8
- 238000005098 hot rolling Methods 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 238000000137 annealing Methods 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- 229910017755 Cu-Sn Inorganic materials 0.000 description 1
- 229910017927 Cu—Sn Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
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- Heat Treatment Of Sheet Steel (AREA)
Description
本発明は、NiおよびMnを必要最小限の含有量に抑制しつつ、器物等の用途に使用可能な低Niオ−ステナイト系ステンレス鋼に関する。 The present invention relates to a low Ni austenitic stainless steel that can be used for purposes such as containers while suppressing Ni and Mn to the minimum required content.
従来、器物等の用途には特許文献1〜3に記されるようなオーステナイト系ステンレス鋼が多用されている。 Conventionally, austenitic stainless steels as described in Patent Documents 1 to 3 are frequently used for applications such as equipment.
特許文献1〜3の技術では、オーステナイト安定度が不安定で加工度が大きい場合時期割れが発生することがある。時期割れとは、金属材料を絞り加工等の成形をした場合、素材の脆化や引張残留応力により、室温で放置されているうちに材料中に亀裂が生じて割れる現象のことをいう。本発明の課題は、加工性および耐時期割れ性に優れた低Niオ−ステナイト系ステンレス鋼板を提供することにある。 In the techniques of Patent Documents 1 to 3, when the austenite stability is unstable and the degree of processing is large, a time crack may occur. The term “cracking” refers to a phenomenon in which when a metal material is formed by drawing or the like, a crack occurs in the material and breaks while the material is left at room temperature due to embrittlement or tensile residual stress. An object of the present invention is to provide a low Ni austenitic stainless steel sheet excellent in workability and time cracking resistance.
上記課題は、質量%で、C:0.03〜0.30%、Si:1.50%以下、Mn:2.0〜7.0%、P:0.06%以下、S:0.005%以下、Ni:1.0〜4.9%、Cr:15.0〜19.0%、Cu:1.0〜3.5%、N:0.03〜0.30%、Sn:0.02%以下、B:0.001〜0.010%を含み、残部がFeおよび不可避的不純物からなり、C+N≦0.30%かつ下記(1)式で示されるオ−ステナイト安定度指標Md30を用いてC+N≦−0.0025Md30+0.30を満足する低Niオーステナイト系ステンレス鋼板による達成される。
Md 30 =551−462(C+N)−9.2Si−8.1Mn−29(Ni+Cu)−13.7Cr・・・(1)
The above-mentioned problems are in mass%, C: 0.03 to 0.30 % , Si: 1.50% or less, Mn: 2.0 to 7.0 % , P: 0.06% or less, S: 0.00. 005% or less, Ni: 1.0 to 4.9 % , Cr: 15.0 to 19.0 % , Cu: 1.0 to 3.5 % , N: 0.03 to 0.30 % , Sn: An austenite stability index including 0.02% or less, B: 0.001 to 0.010 % , the balance being Fe and inevitable impurities, C + N ≦ 0.30%, and represented by the following formula (1) using md 30 satisfies the C + N ≦ -0.0025Md 30 +0.30 be achieved by the low-Ni austenitic stainless steel.
Md 30 = 551-462 (C + N ) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr ··· (1)
また、質量%で、C:0.03〜0.15%、Si:1.50%以下、Mn:2.0〜5.0%、P:0.06%以下、S:0.005%以下、Ni:1.0〜4.0%、Cr:15.0〜17.0%、Cu:1.0〜3.5%、N:0.03〜0.15%、Sn:0.02%以下、B:0.001〜0.010%、を含み、残部がFeおよび不可避的不純物からなり、C+N≦0.30%かつ下記(1)式で示されるオ−ステナイト安定度指標Md 30 を用いてC+N≦−0.0025Md30+0.30を満足する低Niオ−ステナイト系ステンレス鋼板としても良い。 Further, in terms of mass%, C: 0.03 to 0.15 % , Si: 1.50% or less, Mn: 2.0 to 5.0 % , P: 0.06% or less, S: 0.005% Hereinafter, Ni: 1.0 to 4.0 % , Cr: 15.0 to 17.0 % , Cu: 1.0 to 3.5 % , N: 0.03 to 0.15 % , Sn: 0.00. 02% or less, B: 0.001 to 0.010%, wherein the balance of Fe and unavoidable impurities, C + N ≦ 0.30% and below (1) o formula - austenite stability index Md 30 may be used as a low Ni austenitic stainless steel sheet satisfying C + N ≦ −0.0025Md 30 +0.30.
また、第3の発明は、加工誘起マルテンサイト量が60%以下かつ加工誘起マルテンサイト相の硬さが450HV以下である、上記2種のステンレス鋼板を加工した加工品である。 The third invention is a processed product obtained by processing the above-described two types of stainless steel sheets, wherein the amount of work-induced martensite is 60% or less and the hardness of the work-induced martensite phase is 450 HV or less.
本発明によれば、Ni含有量を節減しつつもMn含有量の多量添加を回避し、加工性に優れた低Niオ−ステナイト系ステンレス鋼板が提供される。この鋼板を加工した加工品は、素材が300系ステンレス鋼である器物等の用途に使用できる。 According to the present invention, there is provided a low Ni austenitic stainless steel sheet excellent in workability by avoiding the addition of a large amount of Mn content while reducing the Ni content. The processed product obtained by processing this steel plate can be used for purposes such as a container made of 300 series stainless steel.
本発明者らは、種々の成分を有する鋼を深絞り加工し、Md30およびC+N含有量を制御することにより耐時期割れ性が良好な鋼が得られ、かつその鋼板を加工した加工品にて加工誘起マルテンサイト量が60%以下かつ加工誘起マルテンサイト相の硬さが450HV以下の場合に時期割れが防止できることを見出した。Md30とは、30%の変形を加えて加工誘起マルテンサイト量が50%となる温度のことをいい、加工誘起マルテンサイトの生成のしやすさを表す指標である。 The inventors have deep drawn a steel having various components and controlled Md 30 and C + N contents to obtain a steel with good time cracking resistance, and a processed product obtained by processing the steel plate. It has been found that cracking can be prevented when the amount of work-induced martensite is 60% or less and the hardness of the work-induced martensite phase is 450 HV or less. Md 30 refers to a temperature at which the deformation-induced martensite amount is 50% after deformation of 30%, and is an index representing the ease with which processing-induced martensite is generated.
図1にパンチ径φ40mm,ダイス径φ42mm,パンチ速度20mm/分,しわ押え力10kNの条件にて深絞りした加工品の外観を示す。絞り比は、試験片のブランク径をパンチ径で割った値で、鋼板Aが本発明鋼、鋼板Bが比較鋼である。鋼板Bはカップ縁から割れが発生していることがわかる。これは絞り加工後、1日で発生した割れである。 FIG. 1 shows the appearance of a deeply drawn processed product under the conditions of a punch diameter of 40 mm, a die diameter of 42 mm, a punch speed of 20 mm / min, and a wrinkle pressing force of 10 kN. The drawing ratio is a value obtained by dividing the blank diameter of the test piece by the punch diameter. Steel plate A is the steel of the present invention, and steel plate B is the comparative steel. It can be seen that the steel plate B is cracked from the cup edge. This is a crack that occurred one day after drawing.
図2に耐時期割れ限界絞り比が1.7以上を得られるMd30とC+N含有量の範囲を示す。図2中の●は耐時期割れ限界絞り比1.7以上、×は耐時期割れ限界絞り比1.7未満、▲は絞り加工ができないことを表す。この結果から、C+N≦0.30質量%かつ、C+N≦−0.0025Md30+0.30を満足する範囲で耐時期割れ性が良好な鋼板が得られることがわかる。この範囲で耐時期割れ性が改善される理由について以下に説明する。 FIG. 2 shows the range of the Md 30 and C + N contents at which the time cracking limit drawing ratio is 1.7 or more. In FIG. 2, ● represents a time-resistant crack limit drawing ratio of 1.7 or more, x represents a time-resistant crack limit drawing ratio of less than 1.7, and ▲ represents that drawing cannot be performed. From this result, it can be seen that a steel sheet having good time cracking resistance can be obtained within a range satisfying C + N ≦ 0.30 mass% and C + N ≦ −0.0025 Md 30 +0.30. The reason why the time cracking resistance is improved within this range will be described below.
図3にMd30と絞り比1.7で深絞りした加工品のカップ縁における加工誘起マルテンサイト量の関係を示す。図3中の●が時期割れ発生なし、×が時期割れ発生ありである。加工誘起マルテンサイト量は、カップ縁で径5mmの円盤を採取後、エッジをリン酸硫酸中にて電解研磨したサンプルを用い、4枚重ね合わせて振動試料型磁力計により測定した。Md30が増加するにともない加工誘起マルテンサイト量が増加している。ここで、Md30が0以下で耐時期割れ性が良好であるのは、加工誘起マルテンサイトの生成量が少ないことが要因と考えられる、但し、Md30が0以下でもC+N含有量が0.30質量%以上であると加工性そのものが低下し、絞り比1.7で絞り加工ができない。それを示したのが、図2のプロット▲である。一方、Md30が高いと加工誘起マルテンサイト量が多くなるが、同等のマルテンサイト量でも耐時期割れ性に差異が見られる。図中()内にC+N含有量を示しているが、C+N含有量が低いと●になる傾向があることがわかる。図2,3中の1,2は同等のMd30、加工誘起マルテンサイト量であるが、耐時期割れ性に差異が見られる。1,2の鋼板を加工したカップ縁の加工誘起マルテンサイト相の硬さの比較を図4に示す。硬さ測定はマイクロビッカ−ス硬さ試験機を用いて5gの荷重で測定した。鋼板2の方が鋼板1に比べ、加工誘起マルテンサイト相の硬さが低いことがわかる。すなわち、加工誘起マルテンサイトが生成してもその硬さを低減させることにより時期割れを抑制できるものと考えられる。C+N含有量の低減は、加工誘起マルテンサイト相の硬さ低減に寄与する。 FIG. 3 shows a relationship between Md 30 and the amount of processing-induced martensite at the cup edge of a processed product deep-drawn with a drawing ratio of 1.7. In FIG. 3, ● indicates no occurrence of time cracking, and x indicates occurrence of time cracking. The amount of work-induced martensite was measured with a vibrating sample magnetometer by using a sample obtained by collecting a disk having a diameter of 5 mm at the cup edge and then electropolishing the edge in phosphoric sulfuric acid. As Md 30 increases, the amount of work-induced martensite increases. Here, it can be considered that the reason why the Md 30 is 0 or less and the time cracking resistance is good is that the amount of work-induced martensite produced is small. However, even if the Md 30 is 0 or less, the C + N content is 0.00. If it is 30% by mass or more, the workability itself is lowered, and drawing cannot be performed at a drawing ratio of 1.7. This is shown in the plot ▲ in FIG. On the other hand, when Md 30 is high, the amount of work-induced martensite increases, but even with an equivalent amount of martensite, there is a difference in the resistance to time cracking. In the figure, the C + N content is shown in parentheses, but it can be seen that if the C + N content is low, it tends to be ●. 1 and 2 in FIGS. 2 and 3 are equivalent Md 30 and the amount of work-induced martensite, but there is a difference in the resistance to time cracking. FIG. 4 shows a comparison of the hardness of the work-induced martensite phase at the cup edge where the steel sheets 1 and 2 are processed. The hardness was measured using a micro Vickers hardness tester with a load of 5 g. It can be seen that the steel plate 2 has a lower hardness of the work-induced martensite phase than the steel plate 1. That is, it is considered that even if the processing-induced martensite is generated, the time cracking can be suppressed by reducing its hardness. Reduction of the C + N content contributes to a reduction in the hardness of the processing-induced martensite phase.
図5に加工誘起マルテンサイト相の硬さと絞り比1.7で加工した時の時期割れ発生有無の関係を示す。図中のプロットはMd30が25〜30の範囲で、加工誘起マルテンサイト量は25〜45%であり、()内はC+N含有量を示している。加工誘起マルテンサイト相の硬さが450HV以下で時期割れが発生していない。したがって、少なくとも絞り比1.7で時期割れを発生させないためには、加工誘起マルテンサイト相の硬さが450HV以下である必要がある。 FIG. 5 shows the relationship between the hardness of the processing-induced martensite phase and the presence or absence of time cracking when processing at a drawing ratio of 1.7. The plot in the figure shows that Md 30 is in the range of 25-30, the amount of work-induced martensite is 25-45%, and the parentheses indicate the C + N content. The hardness of the work-induced martensite phase is 450 HV or less, and no time cracking occurs. Therefore, the hardness of the work-induced martensite phase needs to be 450 HV or less so as not to cause time cracking at least at a drawing ratio of 1.7.
一方、図6に加工誘起マルテンサイト量と絞り比1.7で加工した時の時期割れ発生有無の関係を示す。C+N含有量は約0.15質量%、加工誘起マルテンサイト相の硬さは約440HVであり、()内はMd30を示している。加工誘起マルテンサイト量が60%以下で時期割れが発生していない。したがって、少なくとも絞り比1.7で時期割れを発生させないためには、加工誘起マルテンサイト量が60%以下である必要がある。以上の検討結果から、成分範囲を調整し、加工誘起マルテンサイト量が60%以下かつ加工誘起マルテンサイト相の硬さが450HV以下で耐時期割れ性が改善されることがわかった。 On the other hand, FIG. 6 shows the relationship between the amount of processing-induced martensite and the presence or absence of time cracking when processing at a drawing ratio of 1.7. The C + N content is about 0.15% by mass, the hardness of the work-induced martensite phase is about 440 HV, and the values in parentheses indicate Md 30 . The amount of processing-induced martensite is 60% or less and no time cracking occurs. Therefore, in order to prevent the occurrence of time cracking at least at a drawing ratio of 1.7, the amount of work-induced martensite needs to be 60% or less. From the above examination results, it was found that the component range was adjusted, the amount of work-induced martensite was 60% or less, and the hardness of the work-induced martensite phase was 450 HV or less, whereby the time crack resistance was improved.
以下、本発明鋼に含まれる合金成分ならびに含有範囲限定理由について説明する。
C、Nは、オ−ステナイト生成元素であり、オ−ステナイト相を安定化させるのに必要な元素である。これらの元素の含有量が少なすぎるとδフェライト相の生成量が増大し、熱間加工性が低下するため0.03質量%以上確保する必要がある。一方、C、Nの含有量が多くなりすぎると過度に硬質化し、加工性を阻害する要因となるため、C,N含有量の上限は0.30質量%となる。加工性、熱間加工性を考慮すると望ましくは、0.03〜0.15質量%の範囲となる。
Hereinafter, the alloy components contained in the steel of the present invention and the reasons for limiting the content range will be described.
C and N are austenite-forming elements and are elements necessary for stabilizing the austenite phase. If the content of these elements is too small, the amount of δ ferrite phase produced will increase and the hot workability will decrease, so it is necessary to ensure 0.03% by mass or more. On the other hand, if the content of C and N is too large, the content becomes excessively hard and the workability is hindered, so the upper limit of the C and N content is 0.30% by mass. Considering workability and hot workability, it is desirably in the range of 0.03 to 0.15 mass%.
Siは、製鋼での脱酸に有用な元素である。1.5質量%を越えて過剰に含有させると鋼が硬質化し加工性を損なう要因となる。また、Siはフェライト生成元素であるため、過剰添加は高温域でのδフェライト相の多量生成を招き、熱間加工性を阻害する。したがって、Si含有量は1.5質量%以下に規定した。 Si is an element useful for deoxidation in steelmaking. If the content exceeds 1.5% by mass, the steel becomes hard and the workability is impaired. Further, since Si is a ferrite-forming element, excessive addition causes a large amount of δ-ferrite phase to be generated at a high temperature range, thereby impairing hot workability. Therefore, the Si content is specified to be 1.5% by mass or less.
MnはNiに比べて安価で、Niの機能を代替できる有用なオ−ステナイト形成元素である。オ−ステナイト相を安定化させるために2.0%以上のMn含有量を確保する必要がある。一方、Mn含有量が過剰となると、表面性状に起因する生産性の低下ならびにMnSなどの介在物生成に起因する加工性低下や耐食性低下を引き起こす要因となる。このため、Mn含有量は上限を7.0質量%に規定した。耐食性の観点から望ましくは、2.0〜5.0質量%の範囲となる。 Mn is a useful austenite forming element that is less expensive than Ni and can replace the function of Ni. In order to stabilize the austenite phase, it is necessary to ensure a Mn content of 2.0% or more. On the other hand, when the Mn content is excessive, it causes a decrease in productivity due to surface properties and a decrease in workability and corrosion resistance due to the formation of inclusions such as MnS. For this reason, the upper limit of the Mn content is defined as 7.0% by mass. From the viewpoint of corrosion resistance, it is desirably in the range of 2.0 to 5.0 mass%.
PおよびSは不可避的不純物として混入するが、その含有量は低いほど望ましく、加工性その他の材料特性や製造性に多大な悪影響を与えない範囲として、Pについては0.06質量%以下、Sは0.005質量%以下に規定した。 P and S are mixed as unavoidable impurities, but the lower the content, the more desirable. P is 0.06% by mass or less for P as a range that does not have a great adverse effect on processability and other material properties and manufacturability. Was defined as 0.005 mass% or less.
Niはオ−ステナイト系ステンレス鋼に必須の元素である。良好な熱間加工性を得るには、例えば1200℃の加熱温度でγ単相となるようにNi量を含有させる必要があり、その下限は1.0質量%である。本発明ではコスト低減の観点からNi含有量を極力低く抑える成分設計を行っており、上限を4.9質量%に規定した。コスト面を考慮すると、Ni含有量は4.0質量%以下が望ましい。 Ni is an essential element for austenitic stainless steel. In order to obtain good hot workability, for example, it is necessary to contain Ni so that it becomes a γ single phase at a heating temperature of 1200 ° C., and the lower limit is 1.0 mass%. In the present invention, component design is performed to keep the Ni content as low as possible from the viewpoint of cost reduction, and the upper limit is defined as 4.9% by mass. Considering the cost, the Ni content is preferably 4.0% by mass or less.
Crはステンレス鋼の耐食性を担保する不動態皮膜の形成に必須の元素である。本発明では、耐食性を十分に確保する上で、Cr含有量の下限を15.0質量%とした。ただし、Crはフェライト生成元素であるため、過度のCr含有により熱延前加熱温度が(γ+δ)2相域となり、加熱後もδフェライトの多量生成を招き熱間加工性を損なう要因となるため、好ましくない。したがって、Cr含有量は上限を19.0質量%に規定した。熱間加工性の観点から、Cr含有量は17.0質量%以下が望ましい。 Cr is an essential element for forming a passive film that ensures the corrosion resistance of stainless steel. In the present invention, in order to sufficiently secure the corrosion resistance, the lower limit of the Cr content is set to 15.0% by mass. However, since Cr is a ferrite-forming element, the heating temperature before hot rolling becomes a (γ + δ) two-phase region due to excessive Cr content, and after heating, a large amount of δ-ferrite is generated, which is a factor that impairs hot workability. It is not preferable. Therefore, the upper limit of Cr content is defined as 19.0% by mass. From the viewpoint of hot workability, the Cr content is preferably 17.0% by mass or less.
Cuはオ−ステナイト生成元素であることから、Cu含有量の増加に応じてNi含有量の設定自由度が拡大し、Niを抑制した成分設計が容易になる。オ−ステナイト相を安定化させるために1.0%以上のCu含有量を確保する必要がある。ただし、3.5質量%を越える多量のCu含有は熱間加工性を阻害しやすい。このため、Cu含有量は1.0〜3.5質量%に規定した。 Since Cu is an austenite-generating element, the degree of freedom in setting the Ni content increases with an increase in Cu content, and component design that suppresses Ni becomes easy. In order to stabilize the austenite phase, it is necessary to ensure a Cu content of 1.0% or more. However, a large amount of Cu exceeding 3.5 mass% tends to hinder hot workability. For this reason, Cu content was prescribed | regulated to 1.0-3.5 mass%.
Snは不可避的不純物として混入する可能性があるが、Cuを含有している鋼では低融点化合物のCu−Sn相を生成して熱間加工性を著しく低下させる。したがって、Sn含有量の上限を0.02質量%に規定した。 Sn may be mixed as an unavoidable impurity, but in steel containing Cu, a Cu—Sn phase of a low melting point compound is generated to significantly reduce hot workability. Therefore, the upper limit of the Sn content is defined as 0.02% by mass.
Bは熱間加工性や軟質化を改善するために添加させる元素であり、0.001質量%以上の添加により安定した効果が得られる。ただし、過剰に添加するとBの化合物が析出し、熱間加工性を劣化させるのでその上限を0.010質量%に規定した。 B is an element added to improve hot workability and softening, and a stable effect can be obtained by adding 0.001% by mass or more. However, since the compound of B will precipitate when it adds excessively and hot workability will deteriorate, the upper limit was prescribed | regulated to 0.010 mass%.
本発明鋼は、一般的なオーステナイト系ステンレス鋼板の製造プロセスにより製造可能である。具体的には、成分調整された溶鋼を連続鋳造またはバッチ式で鋳造し、得られた鋳造スラブを加熱した後抽出して、連続熱間圧延機またはリバース式熱間圧延機にて熱間圧延する手法が採用できる。熱間圧延以降の中間焼鈍あるいは仕上焼鈍は1050〜1100℃の範囲で行うことが望ましく、例えば板厚0.1〜3.0mmの焼鈍鋼板とすることが望ましい。 The steel of the present invention can be manufactured by a general austenitic stainless steel sheet manufacturing process. Specifically, the component-adjusted molten steel is cast continuously or batchwise, and the resulting cast slab is heated and extracted, and then hot-rolled with a continuous hot rolling mill or a reverse hot rolling mill. Can be used. The intermediate annealing or finish annealing after the hot rolling is desirably performed in the range of 1050 to 1100 ° C., for example, an annealed steel sheet having a thickness of 0.1 to 3.0 mm is desirable.
上記の鋼成分と製造条件にて得られた鋼板を加工誘起マルテンサイト量が60%以下かつ加工誘起マルテンサイト相の硬さが450HV以下とした加工品とすることにより、時期割れのない加工品を得ることが出来る。
(※実施の形態としても記述した方が良いので、記載しています。)
By making the steel sheet obtained under the above steel components and production conditions into a processed product having a work-induced martensite amount of 60% or less and a hardness of the work-induced martensite phase of 450 HV or less, a processed product free of time cracks. Can be obtained.
(* This is listed as it is better to describe it as an embodiment.)
表1の組成をもつ各種ステンレス鋼を溶製した。表1において、A1〜A11が本発明で規定する化学成分を有する本発明鋼、B1〜B7が比較鋼である。比較鋼の下線部の化学成分含有量が本発明で規定する範囲を外れる。 Various stainless steels having the compositions shown in Table 1 were melted. In Table 1, A1 to A11 are steels of the present invention having chemical components defined by the present invention, and B1 to B7 are comparative steels. The chemical component content of the underlined portion of the comparative steel is out of the range defined in the present invention.
本発明鋼A1〜A11および比較鋼B1〜B7について、冷延鋼板の素材作製を行った。各鋼とも100kgの鋼塊を得た後に、抽出温度1230℃で熱間圧延することにより板厚3.0mmの熱間圧延板を製造した。それぞれの鋼の板厚3.0mmの熱間圧延板を1080℃で均熱1分の焼鈍を施した後、冷間圧延、焼鈍を繰り返すことにより、板厚が1.0mmの焼鈍鋼板を得た。 For inventive steels A1 to A11 and comparative steels B1 to B7, cold-rolled steel sheets were prepared. After obtaining 100 kg of steel ingot for each steel, hot rolled plates having a thickness of 3.0 mm were manufactured by hot rolling at an extraction temperature of 1230 ° C. Annealed steel sheet having a thickness of 1.0 mm is obtained by subjecting each steel sheet to a hot rolled sheet having a thickness of 3.0 mm and annealing at 1080 ° C. for 1 minute soaking, and then repeatedly performing cold rolling and annealing. It was.
上記の板厚1.0mmの焼鈍鋼板を用いて、パンチ径φ40mm,ダイス径φ42mm,パンチ速度20mm/min,しわ押え力10kNの条件にて成形性試験機で深絞り加工を行った。 Using the above annealed steel sheet having a thickness of 1.0 mm, deep drawing was performed with a formability tester under the conditions of a punch diameter of 40 mm, a die diameter of 42 mm, a punch speed of 20 mm / min, and a wrinkle pressing force of 10 kN.
また、上記の加工品を用いて、加工誘起マルテンサイト量の測定および加工誘起マルテンサイト相の硬さの測定を行った。加工誘起マルテンサイト量は、絞り比1.7のカップ縁から径5mmの円盤を採取後、エッジをリン酸硫酸中にて電解研磨したサンプルを用い、4枚重ね合わせて振動試料型磁力計により測定した。加工誘起マルテンサイト相の硬さは、カップ縁からサンプルを採取し断面がサンプルの圧延方向と平行になるように熱間埋め込み樹脂に埋め込み、しゅう酸溶液中で電解研磨した後、マイクロビッカ−ス硬さ試験機を用いて5gの荷重で測定した。表2に絞り比1.7の加工品での時期割れ発生の有無、深絞り加工品カップ縁のマルテンサイト量および加工誘起マルテンサイト相の硬さを示す。表中の0が時期割れ発生なし、×が時期割れ発生ありを示している。 Further, using the above processed product, the amount of processing induced martensite and the hardness of the processing induced martensite phase were measured. The amount of work-induced martensite is obtained by collecting four discs from a cup edge with a drawing ratio of 1.7 and then electropolishing the edges in phosphoric sulfuric acid. It was measured. The hardness of the processing-induced martensite phase is determined by taking a sample from the cup edge, embedding it in a hot embedding resin so that the cross section is parallel to the rolling direction of the sample, and electropolishing in an oxalic acid solution. It measured with the load of 5g using the hardness tester. Table 2 shows the presence or absence of occurrence of time cracking in the processed product having a drawing ratio of 1.7, the amount of martensite at the cup edge of the deep drawn product, and the hardness of the work-induced martensite phase. In the table, 0 indicates no occurrence of time cracking and x indicates occurrence of time cracking.
表2に示されるように、本発明鋼A1〜A11の絞り加工品は加工誘起マルテンサイト量が60%以下かつ加工誘起マルテンサイト相の硬さが450HV以下で時期割れが発生しなかった。一方、比較鋼B1〜B5の絞り加工品は加工誘起マルテンサイト量が60%以下であるが、加工誘起マルテンサイト相の硬さが450HV以上であり時期割れが発生した。また、比較鋼B6の絞り加工品は加工誘起マルテンサイト量が60%以上で、加工誘起マルテンサイト相の硬さが450HV以上あり時期割れが発生した。比較鋼B7の絞り加工品は加工誘起マルテンサイト相の硬さが450HV以下であるが、加工誘起マルテンサイト量が60%以上あり時期割れが発生した。これらの結果より本発明鋼は比較鋼に比べ耐時期割れ性に優れることが確認された。 As shown in Table 2, in the drawn products of the inventive steels A1 to A11, the amount of work-induced martensite was 60% or less and the hardness of the work-induced martensite phase was 450 HV or less, and no time cracking occurred. On the other hand, the drawn products of the comparative steels B1 to B5 had a work-induced martensite amount of 60% or less, but the work-induced martensite phase had a hardness of 450 HV or more and a time crack occurred. Further, the drawn product of the comparative steel B6 had a work-induced martensite amount of 60% or more, the work-induced martensite phase had a hardness of 450 HV or more, and time cracking occurred. The drawn product of comparative steel B7 had a work-induced martensite phase hardness of 450 HV or less, but the work-induced martensite amount was 60% or more and a time crack occurred. From these results, it was confirmed that the steel of the present invention is superior in time crack resistance compared to the comparative steel.
また、上述したとおりC+N≦0.30質量%かつ、C+N≦−0.0025Md30+0.30を満足する範囲で耐時期割れ性が良好な鋼板が得られることが確認された。以上のように、成分範囲を調整し、Md30およびC+N含有量を制御することにより加工性に優れる鋼板を提供し、かつその鋼板を加工した加工品にて加工誘起マルテンサイト量が60%以下かつ加工誘起マルテンサイト相の硬さが450HV以下の場合に時期割れが防止できることを見出した。 In addition, as described above, it was confirmed that a steel plate having good time cracking resistance was obtained in a range satisfying C + N ≦ 0.30 mass% and C + N ≦ −0.0025 Md 30 +0.30. As described above, a steel sheet with excellent workability is provided by adjusting the component range and controlling the Md 30 and C + N contents, and the work-induced martensite content is 60% or less in a processed product obtained by processing the steel sheet. And it discovered that a time crack could be prevented when the hardness of a processing induction martensite phase is 450 HV or less.
Claims (3)
C:0.03〜0.30%
Si:1.50%以下
Mn:2.0〜7.0%
P:0.06%以下
S:0.005%以下
Ni:1.0〜4.9%
Cr:15.0〜19.0%
Cu:1.0〜3.5%
N:0.03〜0.30%
Sn:0.02%以下
B:0.001〜0.010%
を含み、残部がFeおよび不可避的不純物からなり、C+N≦0.30%かつ下記(1)式で示されるオ−ステナイト安定度指標Md 30 を用いてC+N≦−0.0025Md30+0.30を満足する低Niオ−ステナイト系ステンレス鋼板。
Md 30 =551−462(C+N)−9.2Si−8.1Mn−29(Ni+Cu)−13.7Cr・・・(1) % By mass
C: 0.03-0.30 %
Si: 1.50% or less Mn: 2.0 to 7.0 %
P: 0.06% or less S: 0.005% or less Ni: 1.0 to 4.9 %
Cr: 15.0 to 19.0 %
Cu: 1.0 to 3.5 %
N: 0.03-0.30 %
Sn: 0.02% or less B: 0.001 to 0.010 %
And the balance is Fe and inevitable impurities, C + N ≦ 0.30%, and C + N ≦ −0.0025Md 30 +0.30 using the austenite stability index Md 30 represented by the following formula (1). Satisfied low Ni austenitic stainless steel sheet.
Md 30 = 551-462 (C + N ) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr ··· (1)
C:0.03〜0.15%
Si:1.50%以下
Mn:2.0〜5.0%
P:0.06%以下
S:0.005%以下
Ni:1.0〜4.0%
Cr:15.0〜17.0%
Cu:1.0〜3.5%
N:0.03〜0.15%
Sn:0.02%以下
B:0.001〜0.010%
を含み、残部がFeおよび不可避的不純物からなり、C+N≦0.30%かつ下記(1)式で示されるオ−ステナイト安定度指標Md30を用いてC+N≦−0.0025Md30+0.30を満足する低Niオ−ステナイト系ステンレス鋼板。
Md 30 =551−462(C+N)−9.2Si−8.1Mn−29(Ni+Cu)−13.7Cr・・・(1) % By mass
C: 0.03-0.15 %
Si: 1.50% or less Mn: 2.0 to 5.0 %
P: 0.06% or less S: 0.005% or less Ni: 1.0-4.0 %
Cr: 15.0 to 17.0 %
Cu: 1.0 to 3.5 %
N: 0.03-0.15 %
Sn: 0.02% or less B: 0.001 to 0.010 %
And the balance is Fe and inevitable impurities, C + N ≦ 0.30%, and C + N ≦ −0.0025Md 30 +0.30 using the austenite stability index Md 30 represented by the following formula (1). Satisfied low Ni austenitic stainless steel sheet.
Md 30 = 551-462 (C + N ) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr ··· (1)
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