JPH0641689A - High cr steel tube excellent in workability - Google Patents
High cr steel tube excellent in workabilityInfo
- Publication number
- JPH0641689A JPH0641689A JP16308492A JP16308492A JPH0641689A JP H0641689 A JPH0641689 A JP H0641689A JP 16308492 A JP16308492 A JP 16308492A JP 16308492 A JP16308492 A JP 16308492A JP H0641689 A JPH0641689 A JP H0641689A
- Authority
- JP
- Japan
- Prior art keywords
- steel pipe
- steel
- rolling direction
- strip
- workability
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
(57)【要約】
【目的】 本発明は加工性の優れた高Ｃｒ含有鋼管に係
り、さらに詳しくは、例えば曲げ加工時において減肉や
破断を起こしにくい高Ｃｒ含有鋼管に関する。
【構成】 Ｃｒを重量％で７．５％以上２５％未満含有
し、金属組織が実質的にフェライトを主体とする鋼から
なる帯鋼を連続的にロール成形によって円筒状に成形
し、電気抵抗溶接によって電縫鋼管として製造される高
Ｃｒ含有鋼管において、帯鋼での圧延方向に平行な方向
のランクフォード値を１．２以上とし、圧延方向に直交
方向のランクフォード値を１．５以上とした材料を使用
して鋼管とすることを特徴とする加工性の優れた高Ｃｒ
含有鋼管。(57) [Summary] [Object] The present invention relates to a high Cr-containing steel pipe having excellent workability, and more particularly to a high Cr-containing steel pipe that is unlikely to cause wall thinning or fracture during bending, for example. [Structure] A steel strip containing Cr in a content of 7.5% or more and less than 25% by weight and having a metallic structure substantially composed mainly of ferrite is continuously formed into a cylindrical shape by roll forming to obtain an electric resistance. In a high Cr content steel pipe manufactured as an electric resistance welded steel pipe by welding, the Rankford value in the direction parallel to the rolling direction of the strip steel is 1.2 or more, and the Rankford value in the direction orthogonal to the rolling direction is 1.5 or more. High Cr with excellent workability, characterized by using the material
Containing steel pipe.
Description
【０００１】[0001]
【産業上の利用分野】本発明は加工性の優れた高Ｃｒ含
有鋼管に係り、さらに詳しくは、例えば曲げ加工時にお
いて減肉や破断を起こしにくい高Ｃｒ含有鋼管に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high Cr content steel pipe having excellent workability, and more particularly, to a high Cr content steel pipe which is less likely to be thinned or broken during bending.
【０００２】[0002]
【従来の技術】近年、自動車のエギゾーストマニホール
ド（以下エキマニと称する）には従来の鋳物製エキマニ
に代えて、ステンレス鋼板製のエキマニが使用される例
が増加している。これはステンレス鋼板製エキマニの方
がに肉厚を薄くすることが可能であり、自動車の軽量化
に大きく役立つためである。こうした用途に対する鋼と
して既に種々の検討がなされており、例えば特開平２−
１７５８４３号公報にあるようにＣｒを多量含有するフ
ェライト系ステンレス鋼が提案されている。2. Description of the Related Art In recent years, there is an increasing number of cases in which an exhaust manifold (hereinafter referred to as "exhaust manifold") of an automobile is replaced with a conventional cast exhaust manifold by using a stainless steel exhaust manifold. This is because the exhaust manifold made of stainless steel plate can have a thinner wall thickness, which is very useful for reducing the weight of the automobile. Various studies have already been made as steel for such applications, and for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 175843, ferritic stainless steel containing a large amount of Cr has been proposed.
【０００３】かかるフェライト系ステンレス鋼を使用し
てエキマニを製造する方法としては、フェライト系ステ
ンレス鋼板をプレス成形し溶接して製造する方法や、フ
ェライト系ステンレス鋼板を鋼管として造管したステン
レス鋼管を二次加工してエキマニとして製造する方法な
どが提案されている。As a method for manufacturing exhaust manifolds using such ferritic stainless steel, there are two methods: a method in which a ferritic stainless steel sheet is press-formed and welded, and a stainless steel tube manufactured by using a ferritic stainless steel sheet as a steel tube. A method for producing the exhaust manifold by subsequent processing has been proposed.
【０００４】しかし、フェライト系ステンレス鋼はＣｒ
を多量に含有するために加工性が悪く、エキマニのよう
な複雑な形状を有する製品を製造するためには、例えば
中間で焼鈍して加工性を確保するなどの工程が必要な場
合があり、加工コストが高いという難点がある。特に、
フェライト系ステンレス鋼を先ず鋼管としてから曲げ加
工等によってエキマニとして加工する場合には、曲げの
外側に位置する部分で減肉が生じ、減肉が著しい場合に
は破断に至る場合があるために、あまり曲げ半径の小さ
い加工はできなかった。However, ferritic stainless steel is Cr
Processability is poor because it contains a large amount of, in order to produce a product having a complicated shape such as exhaust manifold, it may be necessary, for example, a step such as annealing to ensure workability in the middle, There is a drawback that the processing cost is high. In particular,
When the ferritic stainless steel is first processed as a steel pipe and then processed as an exhaust manifold by bending or the like, a part of the wall located outside the bending causes a thinning, and when the thinning is remarkable, it may lead to breakage. Processing with a very small bending radius was not possible.
【０００５】また、他の用途、例えばフェライト系ステ
ンレス鋼管を配管や手すり等に使用する場合において
も、上記と同様に曲げ加工する場合は多く、こうした用
途においても加工性が充分でないために割れを発生しな
い許容曲げ半径には制限があった。In other applications, for example, when a ferritic stainless steel pipe is used for piping, handrails, etc., it is often bent in the same manner as described above, and cracks are caused due to insufficient workability in such applications. There is a limit to the allowable bending radius that does not occur.
【０００６】[0006]
【発明が解決しようとする課題】本発明はこうした現状
に鑑みて、曲げ加工時において減肉や破断を起こしにく
い高Ｃｒ含有鋼管を提供することを目的とする。SUMMARY OF THE INVENTION In view of the above situation, it is an object of the present invention to provide a high Cr content steel pipe which is less likely to be thinned or broken during bending.
【０００７】[0007]
【課題を解決するための手段】本発明者らは上記の目的
を達成すべく、鋼材の成分組成、造管方法、後熱処理、
ミクロ組織などについて種々検討した結果、帯鋼の集合
組織、従って機械的性質の異方性が鋼管における引張り
や曲げなどの加工性・機械的性質に影響することを見出
した。さらに検討を続けた結果、帯鋼での圧延方向に平
行な方向のランクフォード値を積極的に高めておくと、
該帯鋼を使用して造管した鋼管の特性が向上し、特に帯
鋼での圧延方向に平行な方向のランクフォード値（ｒ0
値）を１．５以上にするとその効果が顕著であることを
見出した。また、圧延方向に直交方向のランクフォード
値（ｒ90値）を高めることも効果があり、該ランクフォ
ード値を２．０以上とすればその効果が特に顕著である
ことも見出だした。ここでランクフォード値（ｒ値）と
は次式で定義されるもので、引張応力下における幅方向
の変形と板厚方向の変形の関係を表す指標である。Means for Solving the Problems In order to achieve the above-mentioned objects, the present inventors have investigated the composition of the steel material, the pipe forming method, the post heat treatment,
As a result of various studies on the microstructure and the like, it was found that the texture of the steel strip, and hence the anisotropy of mechanical properties, affects the workability and mechanical properties such as tension and bending in the steel pipe. As a result of further study, if the Rankford value in the direction parallel to the rolling direction of the steel strip is positively increased,
The properties of a steel pipe produced by using the steel strip are improved, and particularly, the Rankford value (r 0 in a direction parallel to the rolling direction of the steel strip).
It was found that the effect is remarkable when the value) is 1.5 or more. It has also been found that increasing the Rankford value (r 90 value) in the direction orthogonal to the rolling direction is also effective, and when the Rankford value is 2.0 or more, the effect is particularly remarkable. Here, the Rankford value (r value) is defined by the following equation and is an index showing the relationship between the deformation in the width direction and the deformation in the plate thickness direction under tensile stress.
【０００８】[0008]
【数１】 [Equation 1]
【０００９】帯鋼での圧延方向は鋼管の軸方向に、帯鋼
で圧延方向に直交する方向は鋼管の円周方向に対応して
おり、帯鋼の段階でこれらの方向での引張におけるラン
クフォード値を高めることが鋼管の加工性を大きく改善
するものであることが、本発明者らの発見した全く新規
な知見である。The rolling direction in the strip steel corresponds to the axial direction of the steel pipe, and the direction orthogonal to the rolling direction in the strip steel corresponds to the circumferential direction of the steel pipe. Ranks in tension in these directions at the stage of strip steel. It is a completely new finding discovered by the present inventors that increasing the Ford value greatly improves the workability of the steel pipe.
【００１０】従来は一般に高Ｃｒ鋼の加工性を改善する
ためには、帯鋼での圧延方向に平行なランクフォード値
および圧延方向に直交する方向のランクフォード値をや
や低くし、圧延方向に対して４５°をなす方向のランク
フォード値（ｒ45）を高くすること、すなわち圧延方向
に対して種々の方向でのランクフォード値を極力均一な
分布とすることが広く適用されてきた。すなわち、鋼材
の機械的性質の異方性を極力抑制し、特に圧延方向およ
び圧延方向に直交する方向のランクフォード値を抑制す
ることが従来の常識であったのに対して、本発明者らが
見出した知見は逆に鋼材の異方性を高めることによって
鋼管の加工性を飛躍的に高めることができるというもの
であって、従来の技術的常識とは全くことなる新規な知
見である。Conventionally, in general, in order to improve the workability of high Cr steel, the Rankford value parallel to the rolling direction and the Rankford value in the direction orthogonal to the rolling direction are slightly lowered in the strip steel, and On the other hand, it has been widely applied to increase the Rankford value (r 45 ) in the direction forming 45 °, that is, to make the Rankford value in various directions with respect to the rolling direction as uniform as possible. That is, while it has been a conventional common sense to suppress the anisotropy of the mechanical properties of the steel material as much as possible, and particularly to suppress the Rankford value in the rolling direction and the direction orthogonal to the rolling direction, the present inventors On the contrary, the finding found by the author is that the workability of a steel pipe can be dramatically improved by increasing the anisotropy of the steel material, which is a new finding completely different from the conventional technical common sense.
【００１１】本発明は上記の知見に基づいてなされたも
のであり、その要旨とするところは、 Ｃｒを重量％で
７．５％以上２５％未満含有し、金属組織が実質的にフ
ェライトを主体とする鋼からなる帯鋼を、連続的にロー
ル成形によって円筒状に成形し、電気抵抗溶接によって
電縫鋼管として製造される高Ｃｒ含有鋼管において、帯
鋼の段階において該帯鋼の圧延方向に平行な方向におけ
るランクフォード値が１．２以上であり、圧延方向に直
交する方向におけるランクフォード値が１．５以上であ
ることを特徴とする加工性の優れた高Ｃｒ含有鋼管にあ
る。The present invention has been made on the basis of the above findings. The gist of the present invention is that Cr is contained in an amount of 7.5% or more and less than 25% by weight, and the metallic structure is mainly composed of ferrite. In a steel pipe containing high Cr, which is produced as an electric resistance welded steel pipe by electric resistance welding by continuously forming a steel strip made of a steel to be rolled into a cylindrical shape, in the rolling direction of the steel strip at the stage of the steel strip. A high Cr content steel pipe having excellent workability, characterized in that the Rankford value in the parallel direction is 1.2 or more and the Rankford value in the direction orthogonal to the rolling direction is 1.5 or more.
【００１２】特に上記帯鋼の圧延方向に平行な方向にお
けるランクフォード値が１．５以上であり、圧延方向に
直交する方向におけるランクフォード値が２．０以上で
あるようにすることが好ましい。Particularly, it is preferable that the Rankford value of the strip steel in the direction parallel to the rolling direction is 1.5 or more and the Rankford value in the direction orthogonal to the rolling direction is 2.0 or more.
【００１３】本発明の特徴を明確にするために本発明者
らが見出した結果を簡単に述べるならば以下の通りであ
る。鋼管を軸方向に引張変形させた場合、鋼管としての
変形は肉厚の減少と共に外径の減少によってもなされ
る。このときｒ0 およびｒ90が大きくなるほど鋼管の塑
性変形は鋼管外径が変化することでなされる割合が大き
くなり、板厚方向の減肉は相対的に少なくなり、減肉に
よって鋼管の伸びが減少して早期に破断することが回避
できるというのが本発明者らが見出だした知見である。
これに対して、この場合にせん断変形を生じる加工は少
ないので、ｒ45が小さくても鋼管の加工性に対する影響
は小さく、ｒ0 およびｒ90を増大させる効果がはるかに
大きいものである。The following is a brief description of the results found by the present inventors in order to clarify the characteristics of the present invention. When the steel pipe is stretched and deformed in the axial direction, the deformation as a steel pipe is achieved not only by the reduction of the wall thickness but also by the reduction of the outer diameter. At this time, as r 0 and r 90 become larger, the plastic deformation of the steel pipe becomes larger due to the change of the outer diameter of the steel pipe, and the thickness reduction in the plate thickness direction becomes relatively small. It is a finding found by the present inventors that it is possible to avoid the decrease and the early fracture.
On the other hand, in this case, since the work that causes shear deformation is small, even if r 45 is small, the effect on the workability of the steel pipe is small, and the effect of increasing r 0 and r 90 is much greater.
【００１４】なお本発明で帯鋼として、Ｃｒを７．５％
以上２５％未満含有し、金属組織が実質的にフェライト
を主体とする鋼を対象としたのは、金属組織がフェライ
ト主体でＣｒを７．５％未満含有する場合において鋼管
の加工性が大きく低下するためであり、Ｃｒを２５％以
上含有する鋼においてはもはやランクフォード値の制御
だけでは鋼管の加工性を充分に高めることが困難である
から、何れも本発明の対象外とした。Ｃｒを７．５％以
上２５％未満含有し、金属組織が実質的にフェライトを
主体とする鋼であれば、耐食性、強度、靭性等の他の特
性の確保のためにＣ，Ｓｉ，Ｍｎ，Ｎｉ，Ｃｕ，Ｍｏ，
Ｗ，Ｎｂ，Ｖ，Ｔｉ，Ａｌ，Ｎ，Ｏ，Ｂ等の他の元素を
添加している鋼も全て本発明の対象とするものである。
加工性以外に必要とされる特性に応じて選択された組成
を有する鋼であっても、ランクフォード値を本発明で規
定する範囲に制御にすることによって、さらに加工性を
も付与することができるのであって、何れも本発明が対
象とするところを逸脱するものではない。In the present invention, as the steel strip, Cr is 7.5%.
The steel whose content is less than 25% and whose metallographic structure is mainly composed of ferrite is targeted. When the metallographic structure is mainly composed of ferrite and the content of Cr is less than 7.5%, the workability of the steel pipe is greatly reduced. This is because it is difficult to sufficiently improve the workability of the steel pipe only by controlling the Rankford value in the steel containing 25% or more of Cr, and thus it was excluded from the scope of the present invention. In the case of steel containing Cr in the range of 7.5% or more and less than 25% and having a metallic structure substantially composed mainly of ferrite, in order to secure other properties such as corrosion resistance, strength and toughness, C, Si, Mn, Ni, Cu, Mo,
Steels to which other elements such as W, Nb, V, Ti, Al, N, O and B are added are all covered by the present invention.
Even in the case of a steel having a composition selected according to the properties required in addition to the workability, the workability can be further imparted by controlling the Rankford value within the range specified in the present invention. However, none of these are within the scope of the present invention.
【００１５】本発明において、帯鋼の段階において該帯
鋼の圧延方向に平行な方向におけるランクフォード値
（ｒ0 ）を１．２以上とし、圧延方向に直交する方向に
おけるランクフォード値（ｒ90）を１．５以上としたの
は、ｒ0 が１．２未満あるいはｒ90が１．５未満ではエ
キマニ等として使用するのに充分な加工性が得られない
からである。また、例えば鋼管の曲げ加工で曲げ曲率半
径が小さい場合のように、特に厳しい加工性が必要な場
合には、ｒ0 を１．５以上とし、ｒ90を２．０とするこ
とが非常に有効である。In the present invention, the Rankford value (r 0 ) in the direction parallel to the rolling direction of the steel strip is set to 1.2 or more at the stage of the steel strip, and the Rankford value (r 90 in the direction orthogonal to the rolling direction is set. ) Is set to 1.5 or more because if r 0 is less than 1.2 or r 90 is less than 1.5, sufficient processability for use as an exhaust manifold or the like cannot be obtained. Further, when particularly rigorous workability is required, for example, when bending radius of a steel pipe is small, it is very preferable to set r 0 to 1.5 or more and r 90 to 2.0. It is valid.
【００１６】[0016]
【実施例】以下に本発明の実施例について説明する。表
１に成分と鋼板でのランクフォード値を示すステンレス
鋼板を素材として、通常の電縫鋼管製造工程によって表
２に示す寸法の鋼管を製造した。続いてこれら鋼管につ
いて、ＪＩＳ Ｚ２２４１に準拠して、ＪＩＳ Ｚ２２
０１に定める１１号試験片を用いて鋼管引張試験を実施
して、破断に至るまでの伸びを測定した。また、曲げ半
径が１．０Ｄ（Ｄ：鋼管外径）の曲げ加工を施して、曲
げ外周部の破断の有無と減肉の状況を調査した。表２の
曲げ試験結果において、○は曲げ外周部に破断がなく肉
厚が引張前の肉厚に対して８０％以上であったことを示
し、△は曲げ外周部に破断はないものの肉厚が引張前の
肉厚に対して８０％未満であったことを示し、×は曲げ
外周部で破断したことを示す。EXAMPLES Examples of the present invention will be described below. A steel pipe having the dimensions shown in Table 2 was manufactured by a normal ERW steel pipe manufacturing process using a stainless steel plate whose components and Rankford values of the steel plate are shown in Table 1. Then, regarding these steel pipes, in accordance with JIS Z2241, JIS Z22
A steel pipe tensile test was carried out using the No. 11 test piece specified in 01 to measure the elongation until breakage. Further, bending was performed with a bending radius of 1.0 D (D: steel pipe outer diameter), and the presence or absence of breakage of the bending outer peripheral portion and the state of wall thinning were investigated. In the bending test results in Table 2, ◯ indicates that the outer peripheral portion of the bend was not broken and the wall thickness was 80% or more of the wall thickness before tension, and Δ is the wall thickness of the outer peripheral portion of the bend that was not broken. Was less than 80% of the wall thickness before tensioning, and x indicates fracture at the outer periphery of bending.
【００１７】表２から明らかなように、帯鋼での圧延方
向に平行な方向のランクフォード値を１．２以上とし、
圧延方向に直交方向のランクフォード値を１．５以上と
した材料を使用した材料を本発明鋼管例であるＮｏ．１
〜５は鋼管引張試験での破断伸びが大きく、曲げ部に割
れを発生することなく、かつ曲げ外周部の減肉が少ない
のに対して比較例であるＮｏ．６，７では破断伸びが小
さく、曲げ部の減肉が著しく、破断する場合もある。As is clear from Table 2, the Rankford value in the direction parallel to the rolling direction of the strip steel is 1.2 or more,
A material using a material having a Rankford value of 1.5 or more in the direction orthogonal to the rolling direction is No. 1
Nos. 5 to 5 are comparative examples, in which the elongation at break in the steel pipe tensile test is large, cracks do not occur in the bent portion, and the thinning of the bent outer peripheral portion is small. In Nos. 6 and 7, the elongation at break is small, the thickness of the bent portion is significantly reduced, and there are cases where the material breaks.
【００１８】[0018]
【表１】 [Table 1]
【００１９】[0019]
【表２】 [Table 2]
【００２０】[0020]
【発明の効果】以上に述べたように、本発明は素材帯鋼
の段階で圧延方向およびその直交方向のｒ値を向上させ
ることにより、曲げ加工時に減肉や破断を起こすことな
く、加工性に優れた高Ｃｒ含有鋼管を提供するものであ
り、産業の発展に貢献するところ極めて大である。As described above, according to the present invention, by improving the r value in the rolling direction and the direction orthogonal thereto at the stage of the material strip steel, the workability can be improved without causing wall thinning or fracture during bending. It provides an excellent high Cr content steel pipe and is extremely large in contributing to industrial development.
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【手続補正書】[Procedure amendment]
【提出日】平成５年２月２４日[Submission date] February 24, 1993
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】発明の詳細な説明[Name of item to be amended] Detailed explanation of the invention
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【発明の詳細な説明】Detailed Description of the Invention
【０００１】[0001]
【産業上の利用分野】本発明は加工性の優れた高Ｃｒ含
有鋼管に係り、さらに詳しくは、例えば曲げ加工時にお
いて減肉や破断を起こしにくい高Ｃｒ含有鋼管に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high Cr content steel pipe having excellent workability, and more particularly, to a high Cr content steel pipe which is less likely to be thinned or broken during bending.
【０００２】[0002]
【従来の技術】近年、自動車のエギゾーストマニホール
ド（以下エキマニと称する）には従来の鋳物製エキマニ
に代えて、ステンレス鋼板製のエキマニが使用される例
が増加している。これはステンレス鋼板製エキマニの方
が肉厚を薄くすることが可能であり、自動車の軽量化に
大きく役立つためである。こうした用途に対する鋼とし
て既に種々の検討がなされており、例えば特開平２−１
７５８４３号公報にあるようにＣｒを多量含有するフェ
ライト系ステンレス鋼が提案されている。2. Description of the Related Art In recent years, there is an increasing number of cases in which an exhaust manifold (hereinafter referred to as "exhaust manifold") of an automobile is replaced with a conventional cast exhaust manifold by using a stainless steel exhaust manifold. This is more of a stainless steel exhaust manifold
This is because it is possible to reduce the wall thickness, which greatly contributes to weight reduction of the automobile. Various studies have already been made as steel for such applications, for example, Japanese Patent Laid-Open No. 2-1.
As disclosed in Japanese Patent No. 75843, ferritic stainless steel containing a large amount of Cr has been proposed.
【０００３】かかるフェライト系ステンレス鋼を使用し
てエキマニを製造する方法としては、フェライト系ステ
ンレス鋼板をプレス成形し溶接して製造する方法や、フ
ェライト系ステンレス鋼板を鋼管として造管したステン
レス鋼管を二次加工してエキマニとして製造する方法な
どが提案されている。As a method for manufacturing exhaust manifolds using such ferritic stainless steel, there are two methods: a method in which a ferritic stainless steel sheet is press-formed and welded, and a stainless steel tube manufactured by using a ferritic stainless steel sheet as a steel tube. A method for producing the exhaust manifold by subsequent processing has been proposed.
【０００４】しかし、フェライト系ステンレス鋼はＣｒ
を多量に含有するために加工性が悪く、エキマニのよう
な複雑な形状を有する製品を製造するためには、例えば
中間で焼鈍して加工性を確保するなどの工程が必要な場
合があり、加工コストが高いという難点がある。特に、
フェライト系ステンレス鋼を先ず鋼管としてから曲げ加
工等によってエキマニとして加工する場合には、曲げの
外側に位置する部分で減肉が生じ、減肉が著しい場合に
は破断に至る場合があるために、あまり曲げ半径の小さ
い加工はできなかった。However, ferritic stainless steel is Cr
Processability is poor because it contains a large amount of, in order to produce a product having a complicated shape such as exhaust manifold, it may be necessary, for example, a step such as annealing to ensure workability in the middle, There is a drawback that the processing cost is high. In particular,
When the ferritic stainless steel is first processed as a steel pipe and then processed as an exhaust manifold by bending or the like, a part of the wall located outside the bending causes a thinning, and when the thinning is remarkable, it may lead to breakage. Processing with a very small bending radius was not possible.
【０００５】また、他の用途、例えばフェライト系ステ
ンレス鋼管を配管や手すり等に使用する場合において
も、上記と同様に曲げ加工する場合は多く、こうした用
途においても加工性が充分でないために割れを発生しな
い許容曲げ半径には制限があった。In other applications, for example, when a ferritic stainless steel pipe is used for piping, handrails, etc., it is often bent in the same manner as described above, and cracks are caused due to insufficient workability in such applications. There is a limit to the allowable bending radius that does not occur.
【０００６】[0006]
【発明が解決しようとする課題】本発明はこうした現状
に鑑みて、曲げ加工時において減肉や破断を起こしにく
い高Ｃｒ含有鋼管を提供することを目的とする。SUMMARY OF THE INVENTION In view of the above situation, it is an object of the present invention to provide a high Cr content steel pipe which is less likely to be thinned or broken during bending.
【０００７】[0007]
【課題を解決するための手段】本発明者らは上記の目的
を達成すべく、鋼材の成分組成、造管方法、後熱処理、
ミクロ組織などについて種々検討した結果、帯鋼の集合
組織、従って機械的性質の異方性が鋼管における引張り
や曲げなどの加工性・機械的性質に影響することを見出
した。さらに検討を続けた結果、帯鋼での圧延方向に平
行な方向のランクフォード値を積極的に高めておくと、
該帯鋼を使用して造管した鋼管の特性が向上し、特に帯
鋼での圧延方向に平行な方向のランクフォード値（ｒ0
値）を１．２以上、さらに好ましくは１．５以上にする
とその効果が顕著であることを見出した。また、圧延方
向に直交方向のランクフォード値（ｒ90値）を高めるこ
とも効果があり、該ランクフォード値を１．５以上、さ
らに好ましくは２．０以上とすればその効果が特に顕著
であることも見出だした。ここでランクフォード値（ｒ
値）とは次式で定義されるもので、引張応力下における
幅方向の変形と板厚方向の変形の関係を表す指標であ
る。Means for Solving the Problems In order to achieve the above-mentioned objects, the present inventors have investigated the composition of the steel material, the pipe forming method, the post heat treatment,
As a result of various studies on the microstructure and the like, it was found that the texture of the steel strip, and hence the anisotropy of mechanical properties, affects the workability and mechanical properties such as tension and bending in the steel pipe. As a result of further study, if the Rankford value in the direction parallel to the rolling direction of the steel strip is positively increased,
The properties of a steel pipe produced by using the steel strip are improved, and particularly, the Rankford value (r 0 in a direction parallel to the rolling direction of the steel strip).
It has been found that the effect is remarkable when the value) is 1.2 or more, more preferably 1.5 or more. Further, there is an effect to increase the Lankford value in the perpendicular direction to the rolling direction (r 90 value), the Lankford value of 1.5 or more, and
It was also found that the effect is particularly remarkable when the ratio is preferably 2.0 or more. Rank Ford value (r
The value) is defined by the following equation and is an index showing the relationship between the deformation in the width direction and the deformation in the plate thickness direction under tensile stress.
【０００８】[0008]
【数１】 [Equation 1]
【０００９】帯鋼での圧延方向は鋼管の軸方向に、帯鋼
で圧延方向に直交する方向は鋼管の円周方向に対応して
おり、帯鋼の段階でこれらの方向での引張におけるラン
クフォード値を高めることが鋼管の加工性を大きく改善
するものであることが、本発明者らの発見した全く新規
な知見である。The rolling direction in the strip steel corresponds to the axial direction of the steel pipe, and the direction orthogonal to the rolling direction in the strip steel corresponds to the circumferential direction of the steel pipe. Ranks in tension in these directions at the stage of strip steel. It is a completely new finding discovered by the present inventors that increasing the Ford value greatly improves the workability of the steel pipe.
【００１０】従来は一般に高Ｃｒ鋼の加工性を改善する
ためには、帯鋼での圧延方向に平行なランクフォード値
および圧延方向に直交する方向のランクフォード値をや
や低くし、圧延方向に対して４５°をなす方向のランク
フォード値（ｒ45）を高くすること、すなわち圧延方向
に対して種々の方向でのランクフォード値を極力均一な
分布とすることが広く適用されてきた。すなわち、鋼材
の機械的性質の異方性を極力抑制し、特に圧延方向およ
び圧延方向に直交する方向のランクフォード値を抑制す
ることが従来の常識であったのに対して、本発明者らが
見出した知見は逆に鋼材の異方性を高めることによって
鋼管の加工性を飛躍的に高めることができるというもの
であって、従来の技術的常識とは全くことなる新規な知
見である。Conventionally, in general, in order to improve the workability of high Cr steel, the Rankford value parallel to the rolling direction and the Rankford value in the direction orthogonal to the rolling direction are slightly lowered in the strip steel, and On the other hand, it has been widely applied to increase the Rankford value (r 45 ) in the direction forming 45 °, that is, to make the Rankford value in various directions with respect to the rolling direction as uniform as possible. That is, while it has been a conventional common sense to suppress the anisotropy of the mechanical properties of the steel material as much as possible, and particularly to suppress the Rankford value in the rolling direction and the direction orthogonal to the rolling direction, the present inventors On the contrary, the finding found by the author is that the workability of a steel pipe can be dramatically improved by increasing the anisotropy of the steel material, which is a new finding completely different from the conventional technical common sense.
【００１１】本発明は上記の知見に基づいてなされたも
のであり、第１発明が要旨とするところは、Ｃｒを重量
％で７．５％以上２５％未満含有し、金属組織が実質的
にフェライトを主体とする鋼からなる帯鋼を、連続的に
ロール成形によって円筒状に成形し、電気抵抗溶接によ
って電縫鋼管として製造される高Ｃｒ含有鋼管におい
て、帯鋼の段階において該帯鋼の圧延方向に平行な方向
におけるランクフォード値が１．２以上であり、圧延方
向に直交する方向におけるランクフォード値が１．５以
上であることを特徴とする加工性の優れた高Ｃｒ含有鋼
管にあり、第２発明が要旨とするところは、直交する方
向におけるランクフォード値をそれぞれ１．５以上およ
び２．０以上とした高Ｃｒ含有鋼管にある。 The present invention has been made on the basis of the above findings. The gist of the first invention is that Cr is contained in an amount of 7.5% or more and less than 25% by weight, and the metal structure is substantially In a high Cr-containing steel pipe manufactured as an electric resistance welded steel pipe by continuously forming a steel strip mainly composed of ferrite into a cylindrical shape by roll forming, and at the stage of the steel strip, A high Cr content steel pipe having excellent workability, characterized in that the Rankford value in the direction parallel to the rolling direction is 1.2 or more and the Rankford value in the direction orthogonal to the rolling direction is 1.5 or more. Yes, the gist of the second invention is that it is orthogonal
The rank Ford value in each direction is 1.5 or more.
And a high Cr content steel pipe of 2.0 or more.
【００１２】異方性の積極的利用による鋼管の加工性向
上の理由を詳細に述べることは、必ずしも本願の目的と
するところではないが、本発明の特徴を明確にするため
に本発明者らが見出した結果を簡単に述べるならば以下
の通りである。鋼管を軸方向に引張変形させた場合、鋼
管としての変形は肉厚の減少と共に外径の減少によって
もなされる。このときｒ0 およびｒ90が大きくなるほど
鋼管の塑性変形は鋼管外径が変化することでなされる割
合が大きくなり、板厚方向の減肉は相対的に少なくな
り、減肉によって鋼管の伸びが減少して早期に破断する
ことが回避できるというのが本発明者らが見出だした知
見である。これに対して、この場合にせん断変形を生じ
る加工は少ないので、ｒ45が小さくても鋼管の加工性に
対する影響は小さく、ｒ0 およびｒ90を増大させる効果
がはるかに大きいものである。Workability of steel pipe by positive utilization of anisotropy
It is not always the purpose of the present application to elaborate on the above reasons.
Although it is not the case, the following is a brief description of the results found by the present inventors in order to clarify the characteristics of the present invention. When the steel pipe is stretched and deformed in the axial direction, the deformation as a steel pipe is achieved not only by the reduction of the wall thickness but also by the reduction of the outer diameter. At this time, as r 0 and r 90 become larger, the plastic deformation of the steel pipe becomes larger due to the change of the outer diameter of the steel pipe, and the thickness reduction in the plate thickness direction becomes relatively small. It is a finding found by the present inventors that it is possible to avoid the decrease and the early fracture. On the other hand, in this case, since the work that causes shear deformation is small, even if r 45 is small, the effect on the workability of the steel pipe is small, and the effect of increasing r 0 and r 90 is much greater.
【００１３】なお本発明で帯鋼として、Ｃｒを７．５％
以上２５％未満含有し、金属組織が実質的にフェライト
を主体とする鋼を対象としたのは、金属組織がフェライ
ト主体でＣｒを７．５％以上含有する場合において鋼管
の加工性が大きく低下するためであり、Ｃｒを２５％以
上含有する鋼においてはもはやランクフォード値の制御
だけでは鋼管の加工性を充分に高めることが困難である
から、何れも本発明の対象外とした。Ｃｒを７．５％以
上２５％未満含有し、金属組織が実質的にフェライトを
主体とする鋼であれば、耐食性、強度、靱性等の他の特
性の確保のためにＣ，Ｓｉ，Ｍｎ，Ｎｉ，Ｃｕ，Ｍｏ，
Ｗ，Ｎｂ，Ｖ，Ｔｉ，Ａｌ，Ｎ，Ｏ，Ｂ等の他の元素を
添加している鋼も全て本発明の対象とするものである。
加工性以外に必要とされる特性に応じて選択された組成
を有する鋼であっても、ランクフォード値を本発明で規
定する範囲に制御にすることによって、さらに加工性を
も付与することができるのであって、何れも本発明が対
象とするところを逸脱するものではない。In the present invention, the steel strip contains 7.5% of Cr.
The steel whose content is less than 25% and whose metallographic structure is mainly composed of ferrite is targeted. When the metallographic structure is mainly composed of ferrite and the content of Cr is 7.5% or more , the workability of the steel pipe is significantly reduced. This is because it is difficult to sufficiently improve the workability of the steel pipe only by controlling the Rankford value in the steel containing 25% or more of Cr, and thus it was excluded from the scope of the present invention. In the case of steel containing Cr in the range of 7.5% or more and less than 25% and the metal structure of which is mainly ferrite, in order to secure other properties such as corrosion resistance, strength and toughness, C, Si, Mn, Ni, Cu, Mo,
Steels to which other elements such as W, Nb, V, Ti, Al, N, O and B are added are all covered by the present invention.
Even in the case of a steel having a composition selected according to the properties required in addition to the workability, the workability can be further imparted by controlling the Rankford value within the range specified in the present invention. However, none of these are within the scope of the present invention.
【００１４】本発明において、帯鋼の段階において該帯
鋼の圧延方向に平行な方向におけるランクフォード値
（ｒ0 ）を１．２以上とし、圧延方向に直交する方向に
おけるランクフォード値（ｒ90）を１．５以上としたの
は、ｒ0 が１．２未満あるいはｒ90が１．５未満ではエ
キマニ等として使用するのに充分な加工性が得られない
からである。また、例えば鋼管の曲げ加工で曲げ曲率半
径が小さい場合のように、特に厳しい加工性が必要な場
合には、ｒ0 を１．５以上とし、ｒ90を２．０とするこ
とが非常に有効である。In the present invention, the Rankford value (r 0 ) in the direction parallel to the rolling direction of the steel strip is 1.2 or more at the stage of the steel strip, and the Rankford value (r 90 in the direction orthogonal to the rolling direction). ) Is set to 1.5 or more because if r 0 is less than 1.2 or r 90 is less than 1.5, sufficient processability for use as an exhaust manifold or the like cannot be obtained. Further, when particularly rigorous workability is required, for example, when bending radius of a steel pipe is small, it is very preferable to set r 0 to 1.5 or more and r 90 to 2.0. It is valid.
【００１５】[0015]
【実施例】以下に本発明の実施例について説明する。表
１に成分と鋼板でのランクフォード値を示すステンレス
鋼板を素材として、通常の電縫鋼管製造工程によって表
２に示す寸法の鋼管を製造した。続いてこれら鋼管につ
いて、ＪＩＳ Ｚ２２４１に準拠して、ＪＩＳ Ｚ２２
０１に定める１１号試験片を用いて鋼管引張試験を実施
して、破断に至るまでの伸びを測定した。また、曲げ半
径が１．０Ｄ（Ｄ：鋼管外径）の曲げ加工を施して、曲
げ外周部の破断の有無と減肉の状況を調査した。表２の
曲げ試験結果において、○は曲げ外周部に破断がなく肉
厚が引張前の肉厚に対して８０％以上であったことを示
し、△は曲げ外周部に破断はないものの肉厚が引張前の
肉厚に対して８０％未満であったことを示し、×は曲げ
外周部で破断したことを示す。EXAMPLES Examples of the present invention will be described below. A steel pipe having the dimensions shown in Table 2 was manufactured by a normal ERW steel pipe manufacturing process using a stainless steel plate whose components and Rankford values of the steel plate are shown in Table 1. Then, regarding these steel pipes, in accordance with JIS Z2241, JIS Z22
A steel pipe tensile test was carried out using the No. 11 test piece specified in 01 to measure the elongation until breakage. Further, bending was performed with a bending radius of 1.0 D (D: steel pipe outer diameter), and the presence or absence of breakage of the bending outer peripheral portion and the state of wall thinning were investigated. In the bending test results of Table 2, ◯ indicates that the outer peripheral portion of the bend was not broken and the wall thickness was 80% or more of the wall thickness before tension, and Δ indicates the wall thickness of the outer peripheral portion of the bend that was not broken. Was less than 80% of the wall thickness before tensioning, and x indicates fracture at the outer periphery of bending.
【００１６】表２から明らかなように、帯鋼での圧延方
向に平行な方向のランクフォード値を１．２以上とし、
圧延方向に直交方向のランクフォード値を１．５以上と
した材料を使用した材料を本発明鋼管例であるＮｏ．１
〜５は鋼管引張試験での破断伸びが大きく、曲げ部に割
れを発生することなく、かつ曲げ外周部の減肉が少ない
のに対して比較例であるＮｏ．６，７では破断伸びが小
さく、曲げ部の減肉が著しく、破断する場合もある。As is clear from Table 2, the Rankford value in the direction parallel to the rolling direction of the strip steel is 1.2 or more,
A material using a material having a Rankford value of 1.5 or more in the direction orthogonal to the rolling direction is No. 1
Nos. 5 to 5 are comparative examples, in which the elongation at break in the steel pipe tensile test is large, cracks do not occur in the bent portion, and the thinning of the bent outer peripheral portion is small. In Nos. 6 and 7, the elongation at break is small, the thickness of the bent portion is significantly reduced, and there are cases where the material breaks.
【００１７】[0017]
【表１】 [Table 1]
【００１８】[0018]
【表２】 [Table 2]
【００１９】[0019]
【発明の効果】以上に述べたように、本発明は素材帯鋼
の段階で圧延方向およびその直交方向のｒ値を向上させ
ることにより、曲げ加工時に減肉や破断を起こすことな
く、加工性に優れた高Ｃｒ含有鋼管を提供するものであ
り、産業の発展に貢献するところ極めて大である。As described above, according to the present invention, by improving the r value in the rolling direction and the direction orthogonal thereto at the stage of the material strip steel, the workability can be improved without causing wall thinning or fracture during bending. It provides an excellent high Cr content steel pipe and is extremely large in contributing to industrial development.
Claims (2)
含有し、金属組織が実質的にフェライトを主体とする鋼
からなる帯鋼を、連続的にロール成形によって円筒状に
成形し、電気抵抗溶接によって電縫鋼管として製造され
る高Ｃｒ含有鋼管において、帯鋼の段階において該帯鋼
の圧延方向に平行な方向におけるランクフォード値が
１．２以上であり、圧延方向に直交する方向におけるラ
ンクフォード値が１．５以上であることを特徴とする加
工性の優れた高Ｃｒ含有鋼管。1. A steel strip containing Cr in a content of 7.5% or more and less than 25% by weight and having a metal structure substantially composed mainly of ferrite is continuously formed into a cylindrical shape by roll forming. In a high Cr content steel pipe manufactured as an electric resistance welded steel pipe by electric resistance welding, the Rankford value in the direction parallel to the rolling direction of the steel strip is 1.2 or more at the stage of the steel strip and is orthogonal to the rolling direction. High Cr content steel pipe with excellent workability, characterized in that the Rankford value in the direction is 1.5 or more.
ンクフォード値が１．５以上であり、圧延方向に直交す
る方向におけるランクフォード値が２．０以上である請
求項１に記載の加工性の優れた高Ｃｒ含有鋼管。2. The processing according to claim 1, wherein the strip steel has a Rankford value of 1.5 or more in a direction parallel to the rolling direction and a Rankford value of 2.0 or more in a direction orthogonal to the rolling direction. High Cr content steel pipe with excellent properties.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16308492A JPH0641689A (en) | 1992-06-22 | 1992-06-22 | High cr steel tube excellent in workability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16308492A JPH0641689A (en) | 1992-06-22 | 1992-06-22 | High cr steel tube excellent in workability |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0641689A true JPH0641689A (en) | 1994-02-15 |
Family
ID=15766882
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16308492A Withdrawn JPH0641689A (en) | 1992-06-22 | 1992-06-22 | High cr steel tube excellent in workability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0641689A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001096624A1 (en) * | 2000-06-14 | 2001-12-20 | Kawasaki Steel Corporation | High carbon steel pipe excellent in cold formability and high frequency hardenability and method for producing the same |
| WO2002010469A1 (en) * | 2000-07-27 | 2002-02-07 | Kawasaki Steel Corporation | Stainless-steel pipe with excellent suitability for secondary processing for automotive structural member |
| WO2002010631A1 (en) * | 2000-08-01 | 2002-02-07 | Nisshin Steel Co., Ltd. | Stainless steel oil feeding pipe |
| WO2002103069A1 (en) * | 2000-01-28 | 2002-12-27 | Kawasaki Steel Corporation | Steel pipe having high formability and method for production thereof |
| WO2002103070A1 (en) * | 2001-06-14 | 2002-12-27 | Kawasaki Steel Corporation | Method for producing steel pipe having high ductility |
| JP2006176824A (en) * | 2004-12-22 | 2006-07-06 | Nippon Steel & Sumikin Stainless Steel Corp | Ferritic stainless steel welded pipe with excellent pipe expansion workability |
| KR100617931B1 (en) * | 2002-10-31 | 2006-08-30 | 제이에프이 스틸 가부시키가이샤 | High workability steel pipe and manufacturing method |
| US7591914B2 (en) * | 2000-01-28 | 2009-09-22 | Jfe Steel Corporation | High-workability steel pipe and method of producing same |
| US7754344B2 (en) | 2004-12-22 | 2010-07-13 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferritic stainless steel welded pipe superior in expandability |
-
1992
- 1992-06-22 JP JP16308492A patent/JPH0641689A/en not_active Withdrawn
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002103069A1 (en) * | 2000-01-28 | 2002-12-27 | Kawasaki Steel Corporation | Steel pipe having high formability and method for production thereof |
| US7591914B2 (en) * | 2000-01-28 | 2009-09-22 | Jfe Steel Corporation | High-workability steel pipe and method of producing same |
| WO2001096624A1 (en) * | 2000-06-14 | 2001-12-20 | Kawasaki Steel Corporation | High carbon steel pipe excellent in cold formability and high frequency hardenability and method for producing the same |
| WO2002010469A1 (en) * | 2000-07-27 | 2002-02-07 | Kawasaki Steel Corporation | Stainless-steel pipe with excellent suitability for secondary processing for automotive structural member |
| US6755919B2 (en) | 2000-07-27 | 2004-06-29 | Jfe Steel Corporation | Stainless steel tube for automobile structure |
| WO2002010631A1 (en) * | 2000-08-01 | 2002-02-07 | Nisshin Steel Co., Ltd. | Stainless steel oil feeding pipe |
| US6851455B2 (en) | 2000-08-01 | 2005-02-08 | Nisshin Steel Co., Ltd. | Stainless steel oil feeding pipe |
| WO2002103070A1 (en) * | 2001-06-14 | 2002-12-27 | Kawasaki Steel Corporation | Method for producing steel pipe having high ductility |
| KR100617931B1 (en) * | 2002-10-31 | 2006-08-30 | 제이에프이 스틸 가부시키가이샤 | High workability steel pipe and manufacturing method |
| JP2006176824A (en) * | 2004-12-22 | 2006-07-06 | Nippon Steel & Sumikin Stainless Steel Corp | Ferritic stainless steel welded pipe with excellent pipe expansion workability |
| US7754344B2 (en) | 2004-12-22 | 2010-07-13 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferritic stainless steel welded pipe superior in expandability |
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| A300 | Withdrawal of application because of no request for examination |
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