JP2007016306A - Ferritic stainless steel sheet for original pipe of bellows - Google Patents
Ferritic stainless steel sheet for original pipe of bellows Download PDFInfo
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Abstract
Description
本発明は、ベローズ素管に用いられるフェライト系ステンレス鋼板に関し、特に、加工性に優れると共に高温疲労特性や高温塩害腐食特性に優れるベローズ素管用フェライト系ステンレス鋼板に関するものである。 The present invention relates to a ferritic stainless steel sheet used for a bellows base pipe, and more particularly to a ferritic stainless steel sheet for a bellows base pipe that is excellent in workability and excellent in high temperature fatigue characteristics and high temperature salt corrosion characteristics.
液体や気体或いは粉体等を取り扱う機械装置では、それらの輸送を、金属配管を介して行うことが一般的に行われている。そして、その配管の途中には、機械装置の振動や配管の熱膨張による歪や応力を吸収し、それらの影響を緩和するために、平行波型の壁をもつ蛇腹状の金属製の管であるベローズ（フレキシブルチューブとも称される）が設置されているのが普通である。 In a mechanical apparatus that handles liquid, gas, powder, or the like, it is generally performed to transport them through a metal pipe. In the middle of the pipe, a bellows-like metal pipe with parallel-wave walls is used to absorb strain and stress due to vibration of the machine and thermal expansion of the pipe, and to mitigate those effects. A certain bellows (also called a flexible tube) is usually installed.
従来、ベローズに用いられる素材としては、銅やＳＵＳ３０４などに代表されるＦＣＣ金属やオーステナイト系ステンレス鋼板などが主に用いられてきた。その理由は、ベローズに加工することが、他の金属材料では困難であったためである。即ち、銅やオーステナイト系ステンレス鋼板は、常温付近での伸びやｎ値が他の金属材料に比べて大きく、そのため、伸び特性が要求されるバルジ成形に適しているからである。 Conventionally, as a material used for the bellows, FCC metal typified by copper, SUS304 or the like, an austenitic stainless steel plate, or the like has been mainly used. The reason is that it was difficult to process the bellows with other metal materials. In other words, copper and austenitic stainless steel sheets have a larger elongation and n value near room temperature than other metal materials, and are therefore suitable for bulge forming that requires elongation characteristics.
しかし、オーステナイト系ステンレス鋼板は、ベローズへの加工は容易であるが、ベローズ内部を通過する気体や液体等が腐食性が強い場合や高温である場合には、酸化や高温腐食あるいは応力腐食割れが発生しやすいという問題があった。特に、自動車排気管のつなぎ部分に用いられているオーステナイト系ステンレス鋼板製のベローズは、使用中の温度が５００〜７５０℃程度にまで上昇するため、融雪のため道路に散布される塩類が付着した場合には、素材自身が鋭敏化して、高温塩害腐食を起こしやすいという問題もあった。 However, austenitic stainless steel sheets are easy to be processed into bellows, but oxidation, high temperature corrosion or stress corrosion cracking occurs when the gas or liquid passing through the bellows is highly corrosive or at high temperatures. There was a problem that it was likely to occur. In particular, the bellows made of austenitic stainless steel plate used in the connecting part of the automobile exhaust pipe rises to about 500 to 750 ° C. during use, and therefore the salt dispersed on the road due to snow melting adhered. In some cases, the material itself becomes sensitized, and high temperature salt damage corrosion is likely to occur.
このような背景から、各種のベローズ素管用フェライト系ステンレス鋼板が発明されている。例えば、特許文献１には、Ｃ，Ｓｉ，Ｍｎ，Ｓ，Ｃｒ，Ａｌ，Ｔｉ，Ｎ，Ｏ量を特定の範囲に規定することにより、３５％以上の伸びと１．５以上のｒ値を達成したベローズ加工性に優れたフェライト系ステンレス鋼板が、特許文献２には、Ｃ，Ｃｒ，Ａｌ，Ｎ，Ｓｉ，Ｍｎ，Ｔｉ，Ｎｂ，Ｍｏ，Ｃｕ，Ｎｉ量を特定の範囲に規定し、さらに、結晶粒径を最適な範囲に限定することにより、ベローズ加工性に優れたフェライト系ステンレス鋼板が開示されている。また、特許文献３には、Ｃ，Ｃｒ，Ａｌ，Ｎ，Ｓｉ，Ｍｎ，Ｔｉ，Ｎｂ，Ｍｏ，Ｃｕ，Ｎｉ量を特定の範囲に規定することにより、ベローズ加工性と高温疲労特性に優れたフェライト系ステンレス鋼板が、特許文献４には、Ｃ，Ｃｒ，Ｎ，Ｔｉ，Ｍｏ量を特定の範囲に規定するとともに、素材の表面粗さを最適な範囲に限定することによりベローズ加工性と高温塩害腐食性に優れたフェライト系ステンレス鋼板が開示されている。
しかしながら、上記技術によっても、フェライト系ステンレス鋼板を素材とした素管のベローズ加工性は、オーステナイト系ステンレス鋼板からなる素管に比べるとまだまだ不十分であり、厳しい形状にも適用可能なベローズ素管用フェライト系ステンレス鋼板は提供されていないのが実情である。さらに、自動車の燃費向上の観点から、自動車排気系部材等に要求される高温特性（高温塩害腐食性、高温疲労特性）は、ますます過酷化する傾向にあり、これらの特性を満足しつつ優れた加工性を有するベローズ素管用フェライト系ステンレス鋼板の開発が強く望まれている。 However, even with the above technology, the bellows workability of the base tube made of ferritic stainless steel plate is still insufficient compared to the base tube made of austenitic stainless steel plate. In fact, ferritic stainless steel sheets are not provided. Furthermore, from the viewpoint of improving the fuel efficiency of automobiles, the high-temperature characteristics (high-temperature salt corrosion resistance and high-temperature fatigue characteristics) required for automobile exhaust system components are becoming increasingly severe and excellent while satisfying these characteristics. Development of a ferritic stainless steel sheet for bellows pipes having excellent workability is strongly desired.
本発明の目的は、優れた加工性と優れた高温特性（耐高温塩害腐食と高温疲労特性）とを両立させたベローズ素管用フェライト系ステンレス鋼板を提供することにある。 An object of the present invention is to provide a ferritic stainless steel sheet for a bellows pipe that has both excellent workability and excellent high temperature characteristics (high temperature salt corrosion resistance and high temperature fatigue characteristics).
発明者らは、上記目的を達成するために、素管の素材となるフェライト系ステンレス鋼板の成分組成と鋼板が有する諸特性に着目して鋭意検討を重ねた。その結果、ベローズ素管の加工性は、素材となるフェライト系ステンレス鋼板に微量のＢを添加した上で、鋼板の表面粗さを適正範囲に制御することにより向上すること、一方、高温塩害腐食性と高温疲労特性の高温特性は、適正量のＮｂとＭｏを複合添加することにより向上することを知見し、本発明を完成させた。 In order to achieve the above-mentioned object, the inventors have made extensive studies by paying attention to the component composition of the ferritic stainless steel plate that is the raw material of the raw tube and various properties of the steel plate. As a result, the workability of the bellows tube can be improved by adding a small amount of B to the ferritic stainless steel plate as a material and controlling the surface roughness of the steel plate to an appropriate range. As a result, it was found that the high temperature characteristics of the heat resistance and the high temperature fatigue characteristics were improved by adding a proper amount of Nb and Mo in combination, and the present invention was completed.
すなわち、本発明は、Ｃ：０．０１５ｍａｓｓ％以下、Ｓｉ：１．０ｍａｓｓ％以下、Ｍｎ：１．０ｍａｓｓ％以下、Ｐ：０．０４ｍａｓｓ％以下、Ｓ：０．０１０ｍａｓｓ％以下、Ｃｒ：１１〜１９ｍａｓｓ％、Ｎ：０．０１５ｍａｓｓ％以下、Ａｌ：０．１５ｍａｓｓ％以下、Ｍｏ：１．２５〜２．５ｍａｓｓ％、Ｎｂ：０．３〜０．７ｍａｓｓ％、Ｂ：０．０００３〜０．００３ｍａｓｓ％を含有し、残部がＦｅおよび不可避的不純物からなり、表面粗さＲａが０．４μｍ以下であることを特徴とするベローズ素管用フェライト系ステンレス鋼板である。 That is, the present invention includes C: 0.015 mass% or less, Si: 1.0 mass% or less, Mn: 1.0 mass% or less, P: 0.04 mass% or less, S: 0.010 mass% or less, Cr: 11-11 19 mass%, N: 0.015 mass% or less, Al: 0.15 mass% or less, Mo: 1.25 to 2.5 mass%, Nb: 0.3 to 0.7 mass%, B: 0.0003 to 0.003 mass %, The balance is Fe and inevitable impurities, and the surface roughness Ra is 0.4 μm or less.
本発明のステンレス鋼板は、上記成分組成に加えてさらに、Ｃｕ：０．１〜０．６ｍａｓｓ％、Ｎｉ：０．１〜０．６ｍａｓｓ％およびＣｏ：０．０３〜０．６ｍａｓｓ％のうちから選ばれる１種または２種以上を含有することを特徴とする。 In addition to the above component composition, the stainless steel plate of the present invention is further made of Cu: 0.1 to 0.6 mass%, Ni: 0.1 to 0.6 mass%, and Co: 0.03 to 0.6 mass%. It contains one or two or more selected.
また、本発明のステンレス鋼板は、上記成分組成に加えてさらに、Ｖ：０．０４〜１．０ｍａｓｓ％、Ｗ：０．０４〜５．０ｍａｓｓ％、Ｔａ：０．０４〜１．０ｍａｓｓ％およびＴｉ：０．０２〜１．０ｍａｓｓ％のうちから選ばれる１種または２種以上を含有することを特徴とする。 In addition to the above component composition, the stainless steel plate of the present invention further includes V: 0.04 to 1.0 mass%, W: 0.04 to 5.0 mass%, Ta: 0.04 to 1.0 mass%, and It contains one or more selected from Ti: 0.02 to 1.0 mass%.
また、本発明のステンレス鋼板は、板厚が０．５ｍｍ以下であり、外径が２８〜８０ｍｍφの１重もしくは２重の自動車排気系ベローズの素管に用いるものであることを特徴とする。 The stainless steel plate of the present invention is characterized in that it is used for a base tube of a single or double automobile exhaust system bellows having a plate thickness of 0.5 mm or less and an outer diameter of 28 to 80 mmφ.
本発明のフェライト系ステンレス鋼板は、均一伸びが高く、高温塩害腐食特性や高温疲労特性等に優れる特性を有する。そのため、本発明のフェライト系ステンレス鋼板を素材としたベローズ素管は、加工性と高温特性に優れるので自動車排気系に用いるベローズ素管に好適に用いることができる。 The ferritic stainless steel sheet of the present invention has high uniform elongation and excellent properties such as high temperature salt damage corrosion properties and high temperature fatigue properties. Therefore, the bellows tube made of the ferritic stainless steel sheet of the present invention is excellent in workability and high temperature characteristics, and therefore can be suitably used for a bellows tube used in an automobile exhaust system.
ベローズは、パイプ状の素管を、液圧バルジ成形して製造するのが一般的である。従って、素管の素材に要求される特性としては、伸び特性、特に、均一伸び（一様伸び）特性が重要であると考えられる。何故ならば、一箇所でも不均一変形が起こると、局部的に液圧が上昇して割れの起点となるほか、例え、割れに至らなくても、ベローズとしての寿命が著しく低下するからである。発明者らは、種々のフェライト系ステンレス鋼板について、液圧バルジ成形によるベローズ成形試験と、ＪＩＳ１３号Ｂ試験片を用いた引張試験を行い、ベローズ成形可能な最大山高さと引張試験における均一伸びとの関係を調査した。その結果では、両特性の間には、明瞭な関係が認められなかった。 A bellows is generally manufactured by forming a pipe-shaped raw tube by hydraulic bulge forming. Accordingly, it is considered that the elongation characteristics, particularly the uniform elongation (uniform elongation) characteristics are important as the characteristics required for the raw material of the raw tube. This is because if uneven deformation occurs even at one location, the hydraulic pressure increases locally and becomes the starting point of cracking, and even if it does not lead to cracking, the life as a bellows is significantly reduced. . The inventors conducted a bellows forming test by hydraulic bulge forming on various ferritic stainless steel plates and a tensile test using a JIS No. 13 B test piece, and found that the maximum peak height that can be formed by bellows and the uniform elongation in the tensile test. The relationship was investigated. As a result, no clear relationship was observed between the two characteristics.
そこで、引張試験片の形状を種々に変化させて均一伸びを測定し、これと成形可能な最大山高さとの関係を調べた。その結果、平行部の幅が１５０ｍｍ、平行部の長さが２５ｍｍの特殊な形状の引張試験片を用いて測定した均一伸びとベローズ成形可能な最大山高さとの間に、相関があることを見出した。これは、広い加工領域において、一箇所でも不均一変形が生ずれば、割れを起こすベローズの加工と相通ずるものであり、均一伸びの測定方法を工夫することでベローズ加工性を評価できることを示すものである。 Accordingly, the uniform elongation was measured by changing the shape of the tensile test piece in various ways, and the relationship between this and the maximum peak height that could be formed was examined. As a result, it was found that there is a correlation between the uniform elongation measured using a special tensile test piece having a parallel part width of 150 mm and a parallel part length of 25 mm and the maximum peak height that can be formed by bellows. It was. This shows that if even non-uniform deformation occurs in one place in a wide processing area, it is compatible with the processing of the bellows that causes cracking, and the bellows workability can be evaluated by devising a method for measuring uniform elongation. Is.
そこで、発明者らは、フェライト系ステンレス鋼板の均一伸びに及ぼす各種添加元素および鋼板諸特性の影響について調査した。そのうち、均一伸びの改善効果が認められたＢ添加および鋼板表面粗さに関する実験について説明する。
＜実験１＞
Ｃ：０．００８ｍａｓｓ％−Ｓｉ：０．４１ｍａｓｓ％−Ｍｎ：０．３１ｍａｓｓ％−Ｐ：０．０３ｍａｓｓ％−Ｓ：０．００３ｍａｓｓ％−Ｃｒ：１４．５ｍａｓｓ％−Ａｌ：０．０３ｍａｓｓ％−Ｎ：０．０１ｍａｓｓ％−Ｎｂ：０．４７ｍａｓｓ％−Ｍｏ：１．３５ｍａｓｓ％の基本成分組成を有し、Ｂ含有量を０．０００１〜０．００４０ｍａｓｓ％の範囲で変化させた鋼を実験室的に溶製し、鋼塊とした後、この鋼塊を１１７０℃×１時間の加熱後、熱間圧延して板厚３．５ｍｍの熱延板とし、その後、１０７０℃×３０秒の焼鈍後、冷間圧延して板厚０．４ｍｍの冷延板とした。この冷延板に１０３０℃×３０秒の焼鈍を施して冷延焼鈍板とした後、この冷延焼鈍板から、上述した特殊な形状の引張試験片（平行部幅：１５０ｍｍ、平行部長さ：２５ｍｍ）を圧延方向に平行に採取し、引張試験に供して均一伸びを測定した。
Therefore, the inventors investigated the effects of various additive elements and various steel sheet properties on the uniform elongation of ferritic stainless steel sheets. Of these, the experiments regarding the addition of B, which was found to have an effect of improving uniform elongation, and the surface roughness of the steel sheet will be described.
<Experiment 1>
C: 0.008 mass% -Si: 0.41 mass% -Mn: 0.31 mass% -P: 0.03 mass% -S: 0.003 mass% -Cr: 14.5 mass% -Al: 0.03 mass% -N : 0.01 mass%-Nb: 0.47 mass%-Mo: 1.35 mass% Basic component composition of steel, B content changed in the range of 0.0001 to 0.0040 mass% in the laboratory The steel ingot is heated to 1170 ° C. for 1 hour, and then hot-rolled to form a hot-rolled sheet having a thickness of 3.5 mm, and then annealed at 1070 ° C. for 30 seconds. Then, it was cold-rolled to obtain a cold-rolled sheet having a thickness of 0.4 mm. The cold-rolled sheet was annealed at 1030 ° C. for 30 seconds to form a cold-rolled annealed sheet, and from this cold-rolled annealed sheet, the above-mentioned special shape tensile test piece (parallel part width: 150 mm, parallel part length: 25 mm) was taken in parallel with the rolling direction and subjected to a tensile test to measure the uniform elongation.
図１は、上記引張試験の均一伸びに及ぼすＢ含有量の影響を示したものである。図１から、Ｂを０．０００３ｍａｓｓ％以上含有させることにより高い均一伸びが得られる、即ち、ベローズ加工性が向上する、しかし、Ｂを０．００３０ｍａｓｓ％超え含有させた場合には、逆に、均一伸びが低下することがわかる。上記Ｂの効果の原因は、十分に明らかとはなっていないが、Ｂは、粒界に偏析し、粒界強度を高める元素であることから、Ｂを０．０００３ｍａｓｓ％以上添加した場合には、変形時における粒界での微小なクラックの生成を抑制するためと考えられる。また、Ｂを０．００３０ｍａｓｓ％超え添加した場合の均一伸びの低下は、過剰なＢの添加により、多量のＢ化物が粒界に析出し、このＢ化物とマトリックスとの界面に微小なクラックが生成し、均一伸びの低下をもたらすためと考えられる。 FIG. 1 shows the influence of the B content on the uniform elongation of the tensile test. From FIG. 1, it is possible to obtain a high uniform elongation by containing B in an amount of 0.0003 mass% or more, that is, the bellows processability is improved. However, when B is contained in an amount exceeding 0.0030 mass%, conversely, It can be seen that the uniform elongation decreases. The cause of the effect of B is not sufficiently clear, but since B is an element that segregates at the grain boundary and increases the grain boundary strength, when B is added in an amount of 0.0003 mass% or more. This is considered to suppress the generation of minute cracks at the grain boundaries during deformation. In addition, when B is added in excess of 0.0030 mass%, the decrease in uniform elongation is that a large amount of B compound precipitates at the grain boundary due to the addition of excess B, and micro cracks are formed at the interface between the B compound and the matrix. This is thought to be due to the generation and reduction in uniform elongation.
＜実験２＞
実験１で製造したＢ含有量が８ｍａｓｓｐｐｍの冷延焼鈍板の表面粗さを、冷間圧延ロールの表面粗度を変えることにより、算術平均粗さＲａで０．１〜１．０８μｍの範囲で変化させた。そして、これらの冷延焼鈍板から、実験１と同じ特殊な引張試験片（平行部幅：１５０ｍｍ、平行部長さ：２５ｍｍ）を圧延方向に平行に採取し、引張試験に供して均一伸びを測定した。
<Experiment 2>
By changing the surface roughness of the cold-rolled roll with the surface roughness of the cold-rolled annealing plate having a B content of 8 massppm produced in Experiment 1, the arithmetic average roughness Ra is in the range of 0.1 to 1.08 μm. Changed. Then, from these cold-rolled annealed plates, the same special tensile test pieces (parallel part width: 150 mm, parallel part length: 25 mm) as those in Experiment 1 were taken in parallel to the rolling direction and subjected to a tensile test to measure uniform elongation. did.
上記測定の結果を図２に示す。この図２の結果から、鋼板表面粗さが算術平均粗さＲａで０．４μｍ以下であれば、ベローズ加工性の指標である均一伸びが増大することがわかる。この理由は、Ｒａが０．４μｍを超えて粗い場合には、表面の凹凸が引張試験における割れの起点となるため、均一伸びの低下を招くためであると考えられる。 The result of the measurement is shown in FIG. From the results of FIG. 2, it can be seen that if the steel sheet surface roughness is 0.4 μm or less in terms of arithmetic average roughness Ra, uniform elongation, which is an index of bellows workability, increases. The reason for this is considered to be that when Ra is larger than 0.4 μm, the unevenness on the surface becomes the starting point of cracking in the tensile test, which causes a reduction in uniform elongation.
次に、フェライト系ステンレス鋼板の高温特性（高温塩害腐食特性，高温疲労特性）を改善するために、各種添加元素の影響を調査した。そのうち、効果の認められた実験について説明する。
＜実験３＞
Ｃ：０．０１ｍａｓｓ％−Ｓｉ：０．３１ｍａｓｓ％−Ｍｎ：０．３４ｍａｓｓ％−Ｐ：０．０３ｍａｓｓ％−Ｓ：０．００５ｍａｓｓ％−Ｃｒ：１６ｍａｓｓ％−Ａｌ：０．０１８ｍａｓｓ％−Ｎ：０．０１ｍａｓｓ％−Ｍｏ：１．４５ｍａｓｓ％−Ｂ：０．０００６ｍａｓｓ％の基本成分組成を有し、Ｎｂ含有量を０．１９〜０．７４ｍａｓｓ％の範囲で変化させた鋼を実験室的に溶製して鋼塊とした後、この鋼塊を１１７０℃×１時間の加熱後、熱間圧延して板厚３．５ｍｍの熱延板とし、１０７０℃×３０秒の焼鈍後、冷間圧延して板厚０．４ｍｍの冷延板とした。この冷延板に１０３０℃×３０秒の焼鈍を施して冷延焼鈍板とし、下記の高温塩害腐食試験と高温疲労試験に供した。
［高温塩害腐食試験］
冷延焼鈍板の試験片表面および端面を４００番のエメリー紙で研磨した後、常温の飽和食塩水（２６％ＮａＣｌ水溶液）中に５分間浸漬し、大気中で７５０℃×２時間加熱後、室温まで冷却する工程を１サイクルとする腐食試験を２５サイクル実施し、試験片表面に生成した腐食生成物をクエン酸アンモニウム水溶液で除去した後、板厚の減少量（腐食深さ）を測定して、耐高温塩害腐食性を評価した。
［高温疲労試験］
シェンク式の高温疲労試験機を用いて、７５０℃、２２Ｈｚの条件で、試験片に掛ける曲げ応力を種々変化させて両振高温疲労試験を行った。そして、１００万回の曲げでも破断しない曲げ応力を疲労限として求めた。
Next, in order to improve the high temperature characteristics (high temperature salt damage corrosion characteristics, high temperature fatigue characteristics) of ferritic stainless steel sheets, the effects of various additive elements were investigated. Of these, we will explain the experiments that were effective.
<Experiment 3>
C: 0.01 mass% -Si: 0.31 mass% -Mn: 0.34 mass% -P: 0.03 mass% -S: 0.005 mass% -Cr: 16 mass% -Al: 0.018 mass% -N: 0 .01 mass% -Mo: 1.45 mass% -B: 0.0006 mass% of the basic component composition, and Nb content varied in the range of 0.19 to 0.74 mass% in the laboratory. After making into a steel ingot, this steel ingot is heated at 1170 ° C. for 1 hour, and then hot rolled to form a hot-rolled sheet having a thickness of 3.5 mm, after annealing at 1070 ° C. for 30 seconds, and then cold rolled. Thus, a cold-rolled plate having a thickness of 0.4 mm was obtained. The cold-rolled sheet was annealed at 1030 ° C. for 30 seconds to obtain a cold-rolled annealed sheet, which was subjected to the following high-temperature salt damage corrosion test and high-temperature fatigue test.
[High temperature salt corrosion test]
After polishing the surface and end face of the cold-rolled annealed plate with No. 400 emery paper, it was immersed in a normal saline solution (26% NaCl aqueous solution) for 5 minutes, heated in the atmosphere at 750 ° C. for 2 hours, After 25 cycles of corrosion test with 1 cycle of cooling to room temperature, the corrosion product formed on the surface of the test piece was removed with ammonium citrate aqueous solution, and then the thickness reduction (corrosion depth) was measured. The high temperature salt corrosion resistance was evaluated.
[High temperature fatigue test]
Using a Schenk type high-temperature fatigue testing machine, a double-sided high-temperature fatigue test was conducted under various conditions of bending stress applied to the test piece under the conditions of 750 ° C. and 22 Hz. The bending stress that does not break even after one million bendings was determined as the fatigue limit.
＜実験４＞
Ｃ：０．０１ｍａｓｓ％−Ｓｉ：０．３１ｍａｓｓ％−Ｍｎ：０．３４ｍａｓｓ％−Ｐ：０．０３ｍａｓｓ％−Ｓ：０．００５ｍａｓｓ％−Ｃｒ：１６ｍａｓｓ％−Ａｌ：０．０１８ｍａｓｓ％−Ｎ：０．０１ｍａｓｓ％−Ｎｂ：０．４７ｍａｓｓ％−Ｂ：０．０００６ｍａｓｓ％の基本成分組成を有し、Ｍｏ含有量を０．６５〜２．４１ｍａｓｓ％の範囲で変化させた鋼を実験室的に溶製して鋼塊とした後、実験２と同条件で、板厚０．４ｍｍの冷延焼鈍板とし、高温塩害腐食試験と高温疲労試験に供した。
<Experiment 4>
C: 0.01 mass% -Si: 0.31 mass% -Mn: 0.34 mass% -P: 0.03 mass% -S: 0.005 mass% -Cr: 16 mass% -Al: 0.018 mass% -N: 0 .01 mass% -Nb: 0.47 mass% -B: 0.0006 mass% of a basic component composition, and Mo content was varied in the range of 0.65 to 2.41 mass% in a laboratory. After making into a steel ingot, it was made into a cold-rolled annealed plate having a thickness of 0.4 mm under the same conditions as in Experiment 2, and subjected to a high temperature salt corrosion test and a high temperature fatigue test.
図３は、高温塩害腐食特性と高温疲労特性に及ぼすＮｂ含有量の影響を示したものである。この図３から、Ｎｂを０．３ｍａｓｓ％以上含有させることにより、耐高温塩害腐食性と高温疲労特性に優れる鋼板が得られることがわかる。また、図４は、高温塩害腐食特性と高温疲労特性に及ぼすＭｏ含有量の影響を示したものであるが、Ｍｏを１．２５ｍａｓｓ％以上含有させることにより、耐高温塩害腐食性と高温疲労特性に優れる鋼板が得られることがわかる。
本発明は、上記実験１〜４の結果に基き、開発されたものである。
FIG. 3 shows the influence of the Nb content on the high temperature salt damage corrosion characteristics and the high temperature fatigue characteristics. It can be seen from FIG. 3 that a steel sheet excellent in high temperature salt corrosion resistance and high temperature fatigue properties can be obtained by containing 0.3 mass% or more of Nb. FIG. 4 shows the effect of Mo content on high temperature salt corrosion resistance and high temperature fatigue characteristics. By containing Mo in an amount of 1.25 mass% or more, high temperature salt corrosion resistance and high temperature fatigue characteristics are shown. It turns out that the steel plate which is excellent in is obtained.
The present invention has been developed based on the results of Experiments 1 to 4 described above.
次に、本発明に係るフェライト系ステンレス鋼板について説明する。
鋼板表面粗さＲａ：０．４μｍ以下
先述した実験２の結果から明らかなように、本発明のフェライト系ステンレス鋼板の表面粗さは、算術平均粗さＲａで０．４μｍ以下に制御する必要がある。表面粗さＲａを０．４μｍ以下とすることにより、表面の凹凸に起因する割れの発生を抑制して均一伸びを増大させ、ひいては、ベローズ加工性を改善することができる。鋼板の表面粗さをＲａ：０．４μｍ以下に調整する方法は、冷間圧延のワークロールの表面粗さを制御する方法、仕上焼鈍後、調質圧延を行い調整する方法等、いずれの方法を用いてもよい。なお、上記Ｒａは、ＪＩＳ
Ｂ ０６０１に準拠した方法で測定した算術平均粗さの値である。
Next, the ferritic stainless steel sheet according to the present invention will be described.
Steel plate surface roughness Ra: 0.4 μm or less As is clear from the results of Experiment 2 described above, the surface roughness of the ferritic stainless steel plate of the present invention must be controlled to an arithmetic average roughness Ra of 0.4 μm or less. is there. By setting the surface roughness Ra to 0.4 μm or less, it is possible to suppress the occurrence of cracks due to surface irregularities and increase the uniform elongation, thereby improving the bellows workability. The method of adjusting the surface roughness of the steel sheet to Ra: 0.4 μm or less is any method such as a method of controlling the surface roughness of the work roll of cold rolling, a method of adjusting by performing temper rolling after finish annealing, etc. May be used. The above Ra is JIS
It is a value of arithmetic average roughness measured by a method based on B 0601.
次に、本発明のフェライト系ステンレス鋼板の成分組成について説明する。
Ｃ：０．０１５ｍａｓｓ％以下
Ｃは、鋼板の延性や靭性を低下させる元素であり、特に、本発明の主眼とするベローズ加工性にも悪影響を及ぼすため、極力低減することが好ましく、Ｃの上限は０．０１５ｍａｓｓ％とする。なお、本発明においては、Ｃ含有量が極微量であっても何ら悪影響を及ぼさないので、下限を規定する必要はない。
Next, the component composition of the ferritic stainless steel sheet of the present invention will be described.
C: 0.015 mass% or less C is an element that lowers the ductility and toughness of the steel sheet, and particularly adversely affects the bellows workability that is the main subject of the present invention. Is 0.015 mass%. In the present invention, since there is no adverse effect even if the C content is extremely small, it is not necessary to define a lower limit.
Ｓｉ：１．０ｍａｓｓ％以下
Ｓｉは、耐酸化性や耐高温塩害腐食性の改善に有効な元素であるが、鋼を硬質化し、延性の低下を招く元素でもある。特に、Ｓｉを１．０ｍａｓｓ％超え添加すると、本発明の主眼であるベローズ加工性が顕著に低下し始めるので、Ｓｉの上限は１．０ｍａｓｓ％とする。Ｓｉの下限は、特に限定しないが、耐酸化性や耐高温塩害腐食性を確保する観点からは、０．２ｍａｓｓ％以上含有することが好ましい。
Si: 1.0 mass% or less Si is an element effective for improving oxidation resistance and high-temperature salt damage corrosion resistance, but also an element that hardens steel and causes a decrease in ductility. In particular, when Si is added in excess of 1.0 mass%, the bellows workability, which is the main feature of the present invention, starts to deteriorate significantly, so the upper limit of Si is set to 1.0 mass%. Although the minimum of Si is not specifically limited, From a viewpoint of ensuring oxidation resistance and high temperature salt damage corrosion resistance, it is preferable to contain 0.2 mass% or more.
Ｍｎ：１．０ｍａｓｓ％以下
Ｍｎは、Ｎｂ添加フェライト系ステンレス鋼における溶接凝固割れ感受性を低下させる有効な元素である。しかし、Ｍｎは、オーステナイト安定化元素であるため、多量の添加は、高温でのフェライト相の安定性を低下させ、場合によってはオーステナイト相が生成して耐酸化性の低下を招く。また、Ｍｎは、固溶硬化により鋼を硬質化し、特に、１．０ｍａｓｓ％を超えると、加工性の低下が顕著となるので、上限を１．０ｍａｓｓ％とする。なお、Ｍｎの下限は、特に設けないが、溶接凝固割れ感受性を低く抑える観点からは、０．３ｍａｓｓ％以上含有することが好ましい。
Mn: 1.0 mass% or less Mn is an effective element that reduces the susceptibility to weld solidification cracking in Nb-added ferritic stainless steel. However, since Mn is an austenite stabilizing element, a large amount of addition reduces the stability of the ferrite phase at high temperatures, and in some cases, an austenite phase is generated, leading to a reduction in oxidation resistance. Further, Mn hardens the steel by solid solution hardening, and particularly when it exceeds 1.0 mass%, the workability deteriorates significantly, so the upper limit is 1.0 mass%. In addition, although the minimum of Mn is not especially provided, it is preferable to contain 0.3 mass% or more from a viewpoint of suppressing weld solidification cracking sensitivity low.
Ｐ：０．０４ｍａｓｓ％以下
Ｐは、靭性と延性を低下させる元素である。特に、０．０４ｍａｓｓ％を超えて含有すると、靭性・延性の低下が顕著となるため、上限は０．０４ｍａｓｓ％とする。なお、Ｐの含有量は、低くても本発明の効果に悪影響を及ぼさないので、下限を限定する必要はない。
P: 0.04 mass% or less P is an element that decreases toughness and ductility. In particular, if the content exceeds 0.04 mass%, the toughness and ductility are significantly lowered, so the upper limit is 0.04 mass%. Note that even if the content of P is low, the effect of the present invention is not adversely affected, so there is no need to limit the lower limit.
Ｓ：０．０１０ｍａｓｓ％以下
Ｓは、耐食性・耐酸化性を低下させる元素である。特に、０．０１０ｍａｓｓ％を超えると耐食性・耐酸化性の低下が著しくなるため、上限は０．０１０ｍａｓｓ％とする。なお、Ｓの含有量は、低くても本発明の効果に悪影響を及ぼさないので、下限を限定する必要はない。
S: 0.010 mass% or less S is an element that reduces corrosion resistance and oxidation resistance. In particular, if it exceeds 0.010 mass%, the corrosion resistance and oxidation resistance are significantly lowered, so the upper limit is made 0.010 mass%. Note that even if the S content is low, the effect of the present invention is not adversely affected, so there is no need to limit the lower limit.
Ｃｒ：１１〜１９ｍａｓｓ％
Ｃｒは、フェライト系ステンレス鋼板を構成する主要合金元素であり、耐食性・耐酸化性を向上させるために必須の元素である。その効果を得るためには、Ｃｒは１１ｍａｓｓ％以上添加する必要がある。一方、多量のＣｒの添加は、鋼の硬質化を招くばかりでなく、本発明の主眼であるベローズ加工性を低下させるので、Ｃｒの上限は１９ｍａｓｓ％とする。好ましくは、１３〜１９ｍａｓｓ％の範囲である。
Cr: 11-19 mass%
Cr is a main alloy element constituting a ferritic stainless steel sheet, and is an essential element for improving corrosion resistance and oxidation resistance. In order to obtain the effect, it is necessary to add 11 mass% or more of Cr. On the other hand, the addition of a large amount of Cr not only leads to hardening of the steel, but also reduces the bellows workability, which is the main point of the present invention, so the upper limit of Cr is 19 mass%. Preferably, it is the range of 13-19 mass%.
Ｎ：０．０１５ｍａｓｓ％以下
Ｎは、靭性や延性を低下させる元素であり、その含有量は極力低減することが好ましい。特に、本発明の主眼であるベローズ加工性にも悪影響を及ぼすため、Ｎは０．０１５ｍａｓｓ％以下に制限する。なお、Ｎ量は少なくても、ベローズとしての特性に何ら悪影響を及ぼさないので、下限値は限定しない。
N: 0.015 mass% or less N is an element that lowers toughness and ductility, and the content is preferably reduced as much as possible. In particular, N is limited to 0.015 mass% or less because it adversely affects the bellows processability, which is the main focus of the present invention. Note that even if the amount of N is small, there is no adverse effect on the characteristics of the bellows, so the lower limit is not limited.
Ａｌ：０．１５ｍａｓｓ％以下
Ａｌは、強力な脱酸元素であり、精錬時の鋼中酸素低減のために添加される。また、耐酸化性の向上にも有効な元素である。しかし、Ａｌは、過剰に添加すると、靭性・延性の低下を招き、特に、０．１５ｍａｓｓ％を超えるとその傾向が顕著となるため、０．１５ｍａｓｓ％以下に制限する。なお、下限は特に限定しないが、精錬時の脱酸を完全に行うためには、０．００３ｍａｓｓ％以上添加することが好ましい。
Al: 0.15 mass% or less Al is a strong deoxidizing element and is added to reduce oxygen in steel during refining. It is also an element effective for improving oxidation resistance. However, when Al is added excessively, the toughness and ductility are lowered. In particular, when the Al content exceeds 0.15 mass%, the tendency becomes remarkable, so the content is limited to 0.15 mass% or less. In addition, although a minimum is not specifically limited, In order to perform deoxidation at the time of refining completely, adding 0.003 mass% or more is preferable.
Ｎｂ：０．３〜０．７ｍａｓｓ％、Ｍｏ：１．２５〜２．５ｍａｓｓ％
ＭｏおよびＮｂは、高温特性を向上する元素であり、本発明においては重要な添加元素である。Ｎｂは、上述した実験２から明らかなように、０．３ｍａｓｓ％以上含有させることにより、耐高温塩害腐食性と高温疲労特性を改善する効果がある。しかし、Ｎｂ含有量が０．７ｍａｓｓ％を超えると、靭性や延性の低下が顕著になる。よって、Ｎｂ含有量は、０．３〜０．７ｍａｓｓ％の範囲とする。また、Ｍｏは、上述した実験３から明らかなように、１．２５ｍａｓｓ％以上含有させることにより、耐高温塩害腐食性と高温疲労特性を改善する効果がある。しかし、Ｍｏを２．５ｍａｓｓ％超え含有させた場合には、延性や靭性の低下を招く。よって、Ｍｏの含有量は、１．２５〜２．５ｍａｓｓ％の範囲とする。
Nb: 0.3-0.7 mass%, Mo: 1.25-2.5 mass%
Mo and Nb are elements that improve high-temperature characteristics, and are important additive elements in the present invention. As apparent from Experiment 2 described above, Nb has an effect of improving high temperature salt corrosion resistance and high temperature fatigue characteristics by containing 0.3 mass% or more. However, when the Nb content exceeds 0.7 mass%, the toughness and ductility are significantly reduced. Therefore, Nb content shall be the range of 0.3-0.7 mass%. Further, as apparent from Experiment 3 described above, Mo is effective to improve the high temperature salt corrosion resistance and high temperature fatigue characteristics by containing 1.25 mass% or more. However, when Mo is contained exceeding 2.5 mass%, ductility and toughness are reduced. Therefore, the Mo content is in the range of 1.25 to 2.5 mass%.
Ｂ：０．０００３〜０．００３ｍａｓｓ％
Ｂは、ベローズ加工性の向上をもたらす重要な元素であり、本発明においては必須の元素である。上述した実験１の結果（図１）から明らかなように、Ｂを０．０００３ｍａｓｓ％以上含有させることにより均一伸びが向上し、優れたベローズ加工性が得られる。一方、Ｂは、０．００３０ｍａｓｓ％を超えて含有させた場合には、逆に、均一伸びの低下を招く。そのため、本発明においては、Ｂの含有量は、０．０００３〜０．００３０ｍａｓｓ％の範囲とする。
B: 0.0003 to 0.003 mass%
B is an important element for improving the bellows processability, and is an essential element in the present invention. As is clear from the results of Experiment 1 described above (FIG. 1), by containing B in an amount of 0.0003 mass% or more, uniform elongation is improved and excellent bellows workability is obtained. On the other hand, when B is contained exceeding 0.0030 mass%, conversely, the uniform elongation is reduced. Therefore, in the present invention, the B content is in the range of 0.0003 to 0.0030 mass%.
なお、本発明のフェライト系ステンレス鋼板は、上記必須成分以外に、要求特性に応じて、下記の成分を添加することができる。
Ｃｕ：０．１〜０．６ｍａｓｓ％、Ｎｉ：０．１〜０．６ｍａｓｓ％およびＣｏ：０．０３〜０．６ｍａｓｓ％のうちから選ばれる１種または２種以上
Ｃｕ，ＮｉおよびＣｏは、靭性および耐食性の改善に有効な元素である。それらの効果を得るためには、Ｃｕ：０．１ｍａｓｓ％以上、Ｎｉ：０．１ｍａｓｓ％以上およびＣｏ：０．０３ｍａｓｓ％以上のうちから選ばれる１種または２種以上を添加することが好ましい。しかし、過剰な添加は、鋼を硬質化するので、それぞれの上限は、Ｃｕ：０．６ｍａｓｓ％、Ｎｉ：０．６ｍａｓｓ％、Ｃｏ：０．６ｍａｓｓ％とすることが好ましい。
In addition to the above essential components, the ferritic stainless steel plate of the present invention can contain the following components according to required characteristics.
One or more selected from Cu: 0.1 to 0.6 mass%, Ni: 0.1 to 0.6 mass% and Co: 0.03 to 0.6 mass% Cu, Ni and Co are: It is an element effective in improving toughness and corrosion resistance. In order to obtain these effects, it is preferable to add one or more selected from Cu: 0.1 mass% or more, Ni: 0.1 mass% or more, and Co: 0.03 mass% or more. However, since excessive addition hardens the steel, the upper limit of each is preferably Cu: 0.6 mass%, Ni: 0.6 mass%, and Co: 0.6 mass%.
Ｖ：０．０４〜１．０ｍａｓｓ％、Ｗ：０．０４〜５．０ｍａｓｓ％、Ｔａ：０．０４〜１．０ｍａｓｓ％およびＴｉ：０．０２〜１．０ｍａｓｓ％のうちから選ばれる１種または２種以上
本発明のフェライト系ステンレス鋼板のように、Ｎｂを多量に添加する鋼板では、Ｖ，Ｗ，ＴａおよびＴｉのうちから選ばれる１種または２種以上を添加することにより、生成する炭窒化物が微細に分散して結晶粒を微細化し、靭性を向上することができる。また、溶接時にＣやＮのコンタミがある場合には、これをＶ等の炭窒化物として固定し、Ｃｒ炭窒化物の生成を抑制することにより、Ｃｒ欠乏層の形成を防止できるので、溶接部の耐食性向上にも寄与する。これらの効果を得るには、Ｖは０．０４ｍａｓｓ％以上、Ｗは０．０４ｍａｓｓ％以上、Ｔａは０．０４ｍａｓｓ％以上、Ｔｉは０．０２ｍａｓｓ％以上添加することが好ましい。しかし、過度に多量の添加は、鋼板自身の靭性を低下させて製造性を低下させるので、それぞれ上限をＶ：１．０ｍａｓｓ％、Ｗ：５．０ｍａｓｓ％、Ｔａ：１．０ｍａｓｓ％およびＴｉ：１．０ｍａｓｓ％とすることが好ましい。
V: 0.04 to 1.0 mass%, W: 0.04 to 5.0 mass%, Ta: 0.04 to 1.0 mass%, and Ti: 0.02 to 1.0 mass% Or, two or more kinds of steel sheets containing a large amount of Nb, such as the ferritic stainless steel sheet of the present invention, are produced by adding one or more kinds selected from V, W, Ta and Ti. Carbonitride can be finely dispersed to refine crystal grains and improve toughness. In addition, when there is C or N contamination during welding, this is fixed as carbonitride such as V and the formation of Cr carbonitride can be suppressed, thereby preventing formation of a Cr-deficient layer. This also contributes to improving the corrosion resistance of the parts. In order to obtain these effects, it is preferable to add V of 0.04 mass% or more, W of 0.04 mass% or more, Ta of 0.04 mass% or more, and Ti of 0.02 mass% or more. However, an excessive amount of addition lowers the toughness of the steel sheet itself and lowers the manufacturability, so that the upper limits are V: 1.0 mass%, W: 5.0 mass%, Ta: 1.0 mass%, and Ti: It is preferable to set it as 1.0 mass%.
なお、本発明のフェライト系ステンレス鋼板は、板厚が０．５ｍｍ以下のものであることが好ましい。前述したように、ベローズは平行波型の蛇腹状に成形されており、熱膨張や振動による変位を吸収する機能を有するものである。上記変位は、ベローズに、曲げとして負荷されるが、このとき、板厚が大きいと材料の歪は大きくなる。そして、材料の弾性限界を超えた歪は塑性歪となり、ベローズ管の疲労破壊を引き起こす原因となる。したがって、疲労破壊を防止する観点からは、板厚は薄いほど好ましい。本発明では、素材となるステンレス鋼板の製造性や製造コストを考慮し、実質的に問題を生じない範囲として、板厚を０．５ｍｍ以下とすることが好ましい。 The ferritic stainless steel sheet of the present invention preferably has a thickness of 0.5 mm or less. As described above, the bellows is formed in a parallel wave bellows shape, and has a function of absorbing displacement due to thermal expansion and vibration. The displacement is loaded on the bellows as a bend. At this time, if the plate thickness is large, the distortion of the material increases. Strain exceeding the elastic limit of the material becomes plastic strain and causes fatigue fracture of the bellows tube. Therefore, from the viewpoint of preventing fatigue failure, the thinner the plate thickness, the better. In the present invention, considering the manufacturability and manufacturing cost of the stainless steel plate as the material, it is preferable to set the plate thickness to 0.5 mm or less as a range that does not substantially cause a problem.
また、本発明のフェライト系ステンレス鋼板を素材とするベローズ素管は、外径が２８〜８０ｍｍφの１重もしくは２重のものであることが好ましい。というのは、ベローズが吸収できる弾性限界範囲内の変位量は、その山高さによって決まるが、同じ山高さでも、素管外径が細いほど、山部の拡管率が大きくなり成形は困難となる。つまり、素管外径が細い場合には、成形可能な山高さは小さくなる。したがって、自動車排気系ベローズ用途において、所定の変位量を吸収できるようにするためには、その素管外径は２８ｍｍφ以上とすることが好ましい。一方、素管外径が大きく、薄肉の場合には、ベローズ自身の剛性不足のため、つぶれや座屈を生じやすく、実質的に使用が困難となる。そのため、素管外径は８０ｍｍφ以下とすることが好ましい。 Moreover, it is preferable that the bellows pipe | tube made from the ferritic stainless steel plate of the present invention is a single or double tube having an outer diameter of 28 to 80 mmφ. This is because the amount of displacement within the elastic limit range that can be absorbed by the bellows is determined by the height of the peak, but even at the same peak height, the narrower the outer diameter of the tube, the greater the expansion rate of the peak and the more difficult the molding becomes. . That is, when the outer diameter of the raw tube is small, the peak height that can be formed is small. Therefore, in order to be able to absorb a predetermined amount of displacement in automotive exhaust system bellows applications, it is preferable that the outer diameter of the raw tube be 28 mmφ or more. On the other hand, in the case where the outer diameter of the raw tube is large and the wall is thin, the bellows itself is insufficient in rigidity, so that it is liable to be crushed or buckled, making it substantially difficult to use. Therefore, the outer diameter of the raw tube is preferably 80 mmφ or less.
なお、設計する上で、ベローズ管の剛性が必要な場合には、肉厚を大きくすることが考えられるが、上述したように、肉厚の増大は疲労破壊の要因となるため好ましくない。これを避けるためには、薄肉のものを重ねて多重管とすることで、剛性や強度を確保することができる。具体的には、２重管とすることが好ましく、３重管以上にすると製造性や製造コストの点で好ましくない。また、肉厚が同じであれば、２重管にした方が、剛性が低下し、柔軟性が増すため、疲労強度も向上するという効果もある。さらに、使用環境によっては、ベローズの内面と外面とで要求特性が異なる場合があり、その場合には、それぞれの要求に合わせた素材を用いた２重管とすることが好ましい。 In designing, if the bellows tube needs to have rigidity, it is conceivable to increase the wall thickness. However, as described above, an increase in the wall thickness is not preferable because it causes fatigue failure. In order to avoid this, rigidity and strength can be secured by stacking thin-walled tubes to form a multiple tube. Specifically, a double pipe is preferable, and a triple pipe or more is not preferable in terms of manufacturability and manufacturing cost. In addition, if the wall thickness is the same, the use of a double pipe has the effect of reducing the rigidity and increasing the flexibility, thereby improving the fatigue strength. Furthermore, depending on the usage environment, the required characteristics may differ between the inner surface and the outer surface of the bellows, and in such a case, it is preferable to use a double pipe using a material that meets each requirement.
表１に示す成分組成を有する各種鋼を高周波真空溶解炉で溶製して５０ｋｇの鋼塊とした後、１１７０℃で１時間加熱後、圧延終了温度を８００℃とする熱間圧延を行い、板厚３．５ｍｍの熱延板とした。その後、この熱延板に１０４０℃×３０秒の焼鈍を施した後、鋼板表面に生成した酸化スケールを酸洗して除去し、冷間圧延して板厚０．４ｍｍの冷延板とし、脱脂した後、１０３０℃×３０秒の焼鈍を行って冷延焼鈍板とした。この際、鋼板の表面粗さを、冷間圧延時のワークロールの粗度を変えることにより変化させた。この冷延焼鈍板から、先述した特殊形状の引張試験片（平行部幅：１５０ｍｍ、平行部長さ：２５ｍｍ）を採取して引張試験を行い、均一伸びを測定した。さらに、先述した高温塩害腐食試験および高温疲労試験にも供して、それぞれの特性を評価した。また、鋼板の表面粗さは、ＪＩＳ Ｂ０６５１に準拠した触針式表面粗さ測定器を用いて、ＪＩＳ Ｂ０６０１に準拠し、鋼板の圧延方向に直角方向の算術平均粗さＲａを測定した。 Various steels having the composition shown in Table 1 were melted in a high-frequency vacuum melting furnace to form a 50 kg steel ingot, heated at 1170 ° C. for 1 hour, and then hot rolled to a rolling end temperature of 800 ° C., A hot-rolled sheet having a thickness of 3.5 mm was used. Then, after subjecting this hot-rolled sheet to annealing at 1040 ° C. for 30 seconds, the oxidized scale produced on the steel sheet surface was removed by pickling, and cold-rolled to form a cold-rolled sheet having a thickness of 0.4 mm, After degreasing, annealing was performed at 1030 ° C. for 30 seconds to obtain a cold-rolled annealed plate. At this time, the surface roughness of the steel sheet was changed by changing the roughness of the work roll during cold rolling. From this cold-rolled annealed plate, the above-mentioned specially-shaped tensile test pieces (parallel part width: 150 mm, parallel part length: 25 mm) were sampled and subjected to a tensile test to measure uniform elongation. Furthermore, each characteristic was evaluated also in the high temperature salt damage corrosion test and high temperature fatigue test which were mentioned above. Moreover, the surface roughness of the steel sheet was measured according to JIS B0601 by using a stylus type surface roughness measuring instrument according to JIS B0651, and the arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the steel sheet was measured.
上記試験結果を表２に示す。本発明に適合するフェライト系ステンレス鋼板は、比較例の鋼板と比べて、ベローズ加工性の指標である均一伸びが高く、また、高温塩害腐食特性と高温疲労特性にも優れていることがわかる。 The test results are shown in Table 2. It can be seen that the ferritic stainless steel sheet suitable for the present invention has a high uniform elongation, which is an index of bellows workability, and is excellent in high temperature salt corrosion resistance and high temperature fatigue characteristics as compared with the steel sheet of the comparative example.
本発明フェライト系ステンレス鋼板は、熱交換器や燃料電池の分野をはじめとした高温特性が要求される用途、分野にも用いることができる。 The ferritic stainless steel sheet of the present invention can be used in applications and fields where high temperature characteristics are required, including the fields of heat exchangers and fuel cells.
Claims (4)
The plate thickness is 0.5 mm or less, and the outer diameter is 28 to 80 mmφ, which is used for a base pipe of a single or double automobile exhaust system bellows. Ferrite-based stainless steel sheet for bellows element tube described in 1.
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| JP2014145097A (en) * | 2013-01-28 | 2014-08-14 | Nippon Steel & Sumikin Stainless Steel Corp | Ferritic stainless steel sheet for automotive exhaust system member suitable for high temperature press molding and manufacturing method of ferritic stainless steel molding part |
| JP2015009828A (en) * | 2013-06-28 | 2015-01-19 | 日新製鋼株式会社 | Large tank for liquid chemical |
| JP2019178362A (en) * | 2018-03-30 | 2019-10-17 | 日鉄ステンレス株式会社 | Steel sheet for ferrite based stainless steel pipe |
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| JPH06100990A (en) * | 1992-09-21 | 1994-04-12 | Sumitomo Metal Ind Ltd | Ferritic stainless steel excellent in strength at high temperature |
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| JP2014145097A (en) * | 2013-01-28 | 2014-08-14 | Nippon Steel & Sumikin Stainless Steel Corp | Ferritic stainless steel sheet for automotive exhaust system member suitable for high temperature press molding and manufacturing method of ferritic stainless steel molding part |
| JP2015009828A (en) * | 2013-06-28 | 2015-01-19 | 日新製鋼株式会社 | Large tank for liquid chemical |
| JP2019178362A (en) * | 2018-03-30 | 2019-10-17 | 日鉄ステンレス株式会社 | Steel sheet for ferrite based stainless steel pipe |
| JP7178791B2 (en) | 2018-03-30 | 2022-11-28 | 日鉄ステンレス株式会社 | Steel plates for ferritic stainless steel pipes |
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Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| LAPS | Cancellation because of no payment of annual fees |