JP2001164317A - Method for producing automotive exhaust system steel pipe excellent in oxidation resistance - Google Patents
Method for producing automotive exhaust system steel pipe excellent in oxidation resistanceInfo
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- JP2001164317A JP2001164317A JP35010299A JP35010299A JP2001164317A JP 2001164317 A JP2001164317 A JP 2001164317A JP 35010299 A JP35010299 A JP 35010299A JP 35010299 A JP35010299 A JP 35010299A JP 2001164317 A JP2001164317 A JP 2001164317A
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- steel
- steel pipe
- oxidation resistance
- exhaust system
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、耐酸化性に優れた
自動車排気系鋼管の製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel pipe for an automobile exhaust system having excellent oxidation resistance.
【０００２】[0002]
【従来の技術】自動車排気ガス規制の強化に伴い、触媒
の浄化能を向上させるために、排気ガスの温度は高くな
る傾向にあり、また、排気系に使用される素材は、熱容
量の大きな鋳物から、熱容量の小さいステンレス鋼管が
主力になっている。こうした用途には主にフェライト系
ステンレスが用いられているが、Ｃｒを１１％以上含む
ため高価である。また、こうしたフェライト系ステンレ
ス鋼の熱延板は加工性が低く、熱延後、酸洗、冷延、冷
延板焼鈍を行って、加工性を補っていたため、工程負荷
が大きかった。さらに、耐酸化性を高めたステンレス
は、Ｃｒ含有量が高く、難酸洗性であり、酸洗コストが
大きく、加えて、Ｎｂなどを多量に含むため、冷延板焼
鈍温度も高くとる必要があり、生産性が低いため、低コ
ストで耐酸化性が高い自動車排気系用鋼管が強く望まれ
ていた。2. Description of the Related Art With the tightening of automobile exhaust gas regulations, the temperature of exhaust gas tends to increase in order to improve the purifying ability of a catalyst, and a material used for an exhaust system is a cast material having a large heat capacity. Therefore, stainless steel tubes with small heat capacity are the mainstay. Ferrite stainless steels are mainly used for such applications, but are expensive because they contain 11% or more of Cr. Further, such a hot-rolled ferritic stainless steel sheet has low workability. After hot rolling, pickling, cold rolling, and cold-rolled sheet annealing were performed to compensate for the workability, so that the process load was large. Furthermore, stainless steel with improved oxidation resistance has a high Cr content, is difficult to pickle, has a high pickling cost, and requires a high cold-rolled sheet annealing temperature because it contains a large amount of Nb and the like. Therefore, steel pipes for automobile exhaust systems having low cost and high oxidation resistance have been strongly desired because of low productivity.
【０００３】[0003]
【発明が解決しようとする課題】本発明は、成分元素が
高く、さらに工程も複雑な自動車排気系用途に用いられ
るステンレス鋼に代わり、耐酸化性に優れた鋼を用い
て、自動車排気系用鋼管を安価に提供することにある。DISCLOSURE OF THE INVENTION The present invention uses a steel having excellent oxidation resistance in place of stainless steel used for automotive exhaust systems, which has a high component element and requires a complicated process, and uses the steel for automobile exhaust systems. It is to provide a steel pipe at low cost.
【０００４】[0004]
【課題を解決するための手段】本発明は上述した課題を
解決するためになされたものであり、請求項１に記載の
耐酸化性に優れた自動車排気系鋼管の製造方法は、質量
％で、Ｃを０．０１５％以下、Ｎを０．０１５％以下、
Ｃｒを１〜１０％、Ａｌを０．５〜５％、Ｓｉを３％以
下、Ｍｎを３％以下含有し、残部Ｆｅおよび不可避不純
物からなる鋼を板厚３ｍｍ以下の熱延板とした後、造管
し、８００℃以上１２００℃以下に加熱した後、３００
秒以内で４００℃以下まで冷却する方法である。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a method of manufacturing a steel pipe for an automobile exhaust system having excellent oxidation resistance according to the present invention is described in terms of mass%. , C: 0.015% or less, N: 0.015% or less,
A steel sheet containing 1 to 10% of Cr, 0.5 to 5% of Al, 3% or less of Si, 3% or less of Mn, and the balance of Fe and unavoidable impurities is formed into a hot-rolled sheet having a thickness of 3 mm or less. Pipe, and heated to 800 ° C or more and 1200 ° C or less.
This is a method of cooling to 400 ° C. or less within seconds.
【０００５】請求項２に記載の耐酸化性に優れた自動車
排気系鋼管の製造方法は、請求項１に記載の化学成分に
加えて、質量％でＴｉ：０．０１〜１％、Ｚｒ：０．０
１〜１％、Ｈｆ：０．０１〜０．５％、Ｖ：０．０１〜
１％、Ｎｂ：０．０１〜１％、Ｔａ：０．０１〜１％、
Ｍｏ：３％以下、Ｗ：３％以下のうち１種または２種以
上を含有し、残部Ｆｅおよび不可避不純物からなる鋼を
板厚３ｍｍ以下の熱延鋼板とした後、造管し、８００℃
以上１２００℃以下に加熱した後、３００秒以内で４０
０℃以下まで冷却する方法である。According to a second aspect of the present invention, there is provided a method for manufacturing an automobile exhaust system steel tube having excellent oxidation resistance, wherein Ti: 0.01 to 1% by mass%, Zr: 0.0
1-1%, Hf: 0.01-0.5%, V: 0.01-
1%, Nb: 0.01 to 1%, Ta: 0.01 to 1%,
Mo: 3% or less, W: 3% or less, containing one or more kinds, and the balance of Fe and unavoidable impurities is made into a hot-rolled steel sheet having a thickness of 3 mm or less, and then piped, and 800 ° C.
After heating to 1200 ° C or less, 40
This is a method of cooling to 0 ° C or less.
【０００６】請求項３に記載の耐酸化性に優れた自動車
排気系鋼管の製造方法は、請求項１または２に記載の化
学成分に加えて、質量％でＣｕ：１％以下、Ｎｉ：１％
以下、Ｃｏ：３％以下、Ｓｎ：１％以下、Ｓｂ：０．５
％以下、Ｃａ：０．０００５〜０．０３％、Ｍｇ：０．
００１〜０．０５％、Ｂ：０．０１％以下、ＲＥＭ：
０．００１〜０．１％のうち１種または２種以上を含有
し、残部Ｆｅおよび不可避不純物からなる鋼を板厚３ｍ
ｍ以下の熱延鋼板とした後、造管し、８００℃以上１２
００℃以下に加熱した後、３００秒以内で４００℃以下
まで冷却する方法である。According to a third aspect of the present invention, there is provided a method of manufacturing a steel pipe for an automobile exhaust system having excellent oxidation resistance, in addition to the chemical components according to the first or second aspect, Cu: 1% or less and Ni: 1 by mass%. %
Hereinafter, Co: 3% or less, Sn: 1% or less, Sb: 0.5
% Or less, Ca: 0.0005 to 0.03%, Mg: 0.
001-0.05%, B: 0.01% or less, REM:
A steel sheet containing one or more of 0.001 to 0.1%, the balance being Fe and inevitable impurities, having a thickness of 3 m
m and hot rolled steel sheet, pipe forming, 800 ° C or more and 12
This is a method in which after heating to 00 ° C or lower, the temperature is cooled to 400 ° C or lower within 300 seconds.
【０００７】請求項４に記載の耐酸化性に優れた自動車
排気系鋼管の製造方法は、請求項１または２または３に
記載の成分を有する鋼を板厚１０ｍｍ以下の熱延鋼板と
した後、１０％以上９０％以下の冷間圧延を施し、得ら
れた冷延鋼板を造管した後、８００℃以上１２００℃以
下に加熱し、３００秒以内で４００℃以下まで冷却する
方法である。According to a fourth aspect of the present invention, there is provided a method for producing a steel pipe for an automobile exhaust system having excellent oxidation resistance, wherein the steel having the component according to the first, second or third aspect is formed into a hot-rolled steel sheet having a thickness of 10 mm or less. Cold rolling of 10% or more and 90% or less is performed, and the resulting cold-rolled steel sheet is formed into a tube, heated to 800 ° C to 1200 ° C, and cooled to 400 ° C or less within 300 seconds.
【０００８】請求項５に記載の耐酸化性に優れた自動車
排気系鋼管の製造方法は、請求項１または２または３に
記載の成分を有する鋼を板厚３ｍｍ以下の熱延鋼板とし
た後、造管し、１％以上２０％以下の絞り加工を施した
後、８００℃以上１２００℃以下に加熱し、３００秒以
内で４００℃以下まで冷却する方法である。According to a fifth aspect of the present invention, there is provided a method of manufacturing a steel pipe for an automobile exhaust system having excellent oxidation resistance, wherein the steel having the component according to the first, second or third aspect is formed into a hot-rolled steel sheet having a thickness of 3 mm or less. This is a method in which a pipe is formed, subjected to a drawing process of 1% or more and 20% or less, heated to 800 ° C or more and 1200 ° C or less, and cooled to 400 ° C or less within 300 seconds.
【０００９】請求項６に記載の耐酸化性に優れた自動車
排気系鋼管の製造方法は、請求項１または２または３に
記載の成分を有する鋼を板厚１０ｍｍ以下の熱延鋼板と
した後、１０％以上９０％以下の冷間圧延を施し、得ら
れた冷延鋼板を造管し、１％以上２０％以下の絞り加工
を施した後、８００℃以上１２００℃以下に加熱し、３
００秒以内で４００℃以下まで冷却する方法である。According to a sixth aspect of the present invention, there is provided a method for producing a steel pipe for an automobile exhaust system having excellent oxidation resistance, wherein the steel having the component according to the first, second or third aspect is formed into a hot-rolled steel sheet having a thickness of 10 mm or less. After cold rolling of 10% or more and 90% or less, the resulting cold-rolled steel sheet is formed into a tube, drawn by 1% or more and 20% or less, and then heated to 800 ° C or more and 1200 ° C or less.
This is a method of cooling to 400 ° C. or less within 00 seconds.
【００１０】すなわち、本発明は、鋼管の成分を特定
し、さらに鋼管に特定の熱処理を施すことにより、優れ
た耐酸化性を有し、自動車排気系としての加工に耐え得
る良加工性の鋼管を安価に製造する方法を提供するもの
である。That is, the present invention provides a steel pipe having excellent oxidation resistance by specifying the components of the steel pipe and further subjecting the steel pipe to a specific heat treatment, and having good workability capable of withstanding processing as an automobile exhaust system. Is provided at a low cost.
【００１１】[0011]
【発明の実施の形態】はじめに本発明で成分組成を限定
した理由を述べる。ＣとＮはＣｒ、Ａｌ、Ｎｂなどと結
合して炭化物や窒化物、あるいは複合炭窒化物を生成
し、加工性と耐酸化性を低減させるため、少ないほど好
ましい。しかし、過度の限定は、いたずらに脱炭、脱窒
工程の負荷を高めるだけであり、Ｃの上限を０．０１５
％、Ｎの上限を０．０１５％とした。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the component composition in the present invention will be described. C and N combine with Cr, Al, Nb and the like to form carbides, nitrides, or composite carbonitrides, and reduce workability and oxidation resistance. However, the excessive limitation only unnecessarily increases the load of the decarburization and denitrification steps, and the upper limit of C is set to 0.015.
% And the upper limit of N are set to 0.015%.
【００１２】ＣｒはＡｌ含有鋼の加工性と耐酸化性を高
めるのに有効な元素であり、１％以上が必要である。１
０％を越えて添加しても特に問題はないが、原料コスト
が高くなるため、上限を１０％とした。[0012] Cr is an element effective for improving the workability and oxidation resistance of the Al-containing steel, and requires 1% or more. 1
Although there is no particular problem even if it is added in excess of 0%, the upper limit is set to 10% because the raw material cost increases.
【００１３】ＡｌはＣｒを含有する鋼の耐酸化性を高め
るのに有効な元素であり、０．５％以上が必要である
が、５％を越えて添加すると、加工性低下が非常に大き
いため、上限を５％とした。Al is an effective element for increasing the oxidation resistance of steel containing Cr, and 0.5% or more is required. However, if it exceeds 5%, the workability is greatly reduced. Therefore, the upper limit is set to 5%.
【００１４】ＳｉはＣｒとＡｌを含有する鋼の耐酸化性
を補うのに有効な元素であるが、３％を越えて添加する
と加工性低下が大きく、上限を３％とした。[0014] Si is an element effective for supplementing the oxidation resistance of steel containing Cr and Al, but when added in excess of 3%, the workability is greatly reduced, and the upper limit is set to 3%.
【００１５】ＭｎはＣｒとＡｌを含有する鋼の耐酸化性
を補うのに有効な元素であるが、３％を超えて添加する
と加工性低下が大きく、さらに高温でオーステナイト相
を生成して、耐酸化性を逆に劣化させるため、上限を３
％とした。Mn is an element effective in supplementing the oxidation resistance of steel containing Cr and Al, but when added in excess of 3%, the workability is greatly reduced, and an austenite phase is formed at a high temperature. The upper limit is set to 3 in order to degrade the oxidation resistance.
%.
【００１６】Ｔｉ、Ｚｒ、Ｈｆ、Ｖはフェライト系ステ
ンレスではＣ、Ｎを固定して加工性を向上させる元素と
して知られているが、Ｃｒ含有量が１０％以下で、Ａｌ
を５％以下含有する本鋼にも、加工性向上元素として有
効であることがわかった。添加元素の効果が有効に生じ
るためには、Ｔｉ：０．０１％以上、Ｚｒ：０．０１％
以上、Ｈｆ：０．０１％以上、Ｖ：０．０１％以上の添
加が必要である。ただし、これらの元素を多量に添加す
ると、逆に加工性が低下するため、Ｔｉ：１％、Ｚｒ：
１％、Ｈｆ：０．５％、Ｖ：１％を上限とした。[0016] Ti, Zr, Hf, and V are known in ferrite stainless steels as elements that fix C and N to improve workability.
Is also effective as a workability improving element in the present steel containing 5% or less. In order for the effect of the additional element to be effectively generated, Ti: 0.01% or more, Zr: 0.01%
As described above, it is necessary to add Hf: 0.01% or more and V: 0.01% or more. However, when these elements are added in a large amount, the workability is conversely reduced, so that Ti: 1%, Zr:
The upper limits were 1%, Hf: 0.5%, and V: 1%.
【００１７】Ｎｂ、Ｔａはフェライト系ステンレスでは
高温強度を高めるのに有効な元素として知られている
が、Ｃｒ含有量が１０％以下で、Ａｌを５％以下含有す
る本鋼にも、高温強度向上元素として有効であることが
わかった。添加元素の効果が有効に生じるためには、Ｎ
ｂ：０．０１％以上、Ｔａ：０．０１％以上の添加が必
要である。ただし、これらの元素を多量に添加すると、
熱延板の靭性が著しく低下し、また鋼管焼鈍温度も上昇
し、製造性が低下するため、Ｎｂ：１％、Ｔａ：１％を
上限とした。Nb and Ta are known to be effective elements for increasing the high-temperature strength of ferritic stainless steels. However, the steels having a Cr content of 10% or less and an Al content of 5% or less also have a high-temperature strength. It was found to be effective as an improving element. In order for the effect of the additional element to be effective, N
b: 0.01% or more, Ta: 0.01% or more must be added. However, if these elements are added in large amounts,
Since the toughness of the hot-rolled sheet is remarkably reduced, the annealing temperature of the steel pipe is also increased, and the productivity is reduced, the upper limits of Nb: 1% and Ta: 1% are set.
【００１８】Ｍｏ、Ｗはフェライト系ステンレスでは耐
食性や耐高温塩害性を高め、また高温強度にも有効な元
素として知られているが、Ｃｒ含有量が１０％以下で、
Ａｌを５％以下含有する本鋼にも、同様に有効であるこ
とがわかった。但し多量に添加すると熱延板の靭性や加
工性が低下するため、Ｍｏは３％、Ｗは３％を上限とし
た。Mo and W are ferritic stainless steels that are known as elements that enhance corrosion resistance and high-temperature salt damage resistance and are also effective for high-temperature strength. However, when the Cr content is 10% or less,
It was also found that the present steel containing 5% or less of Al was similarly effective. However, if added in a large amount, the toughness and workability of the hot-rolled sheet decrease, so the upper limit of Mo is 3% and the upper limit of W is 3%.
【００１９】Ｃｕ、Ｎｉ、ＣｏはＣｒ含有量が１０％以
下で、Ａｌを５％以下含有する鋼の熱延板靭性と鋼管の
耐食性を向上させるが、いずれもオーステナイト生成元
素であり、多量に添加すると高温でオーステナイトを生
成して耐酸化性を劣化させるため、Ｃｕ：１％、Ｎｉ：
１％、Ｃｏ：３％を上限とした。Cu, Ni, and Co have a Cr content of 10% or less and improve the hot rolled sheet toughness of steel containing 5% or less of Al and the corrosion resistance of steel pipes. When added, austenite is formed at a high temperature to deteriorate the oxidation resistance, so that Cu: 1%, Ni:
The upper limits were 1% and Co: 3%.
【００２０】Ｓｎ、Ｓｂはフェライト系ステンレスでは
耐食性を高める元素として知られているが、Ｃｒ含有量
が１０％以下で、Ａｌを５％以下含有する本鋼にも、同
様に有効であることがわかった。但し多量に添加すると
熱延板の靭性や加工性が低下するため、Ｓｎは１％、Ｓ
ｂは０．５％を上限とした。Sn and Sb are known as elements for improving the corrosion resistance of ferritic stainless steel. However, they are also effective for the present steel containing 10% or less of Cr and 5% or less of Al. all right. However, if a large amount is added, the toughness and workability of the hot-rolled sheet decrease, so Sn is 1% and S
The upper limit of b was 0.5%.
【００２１】Ｃａは、熱間加工性の向上に効果がある
が、０．０００５％未満ではその効果は十分ではなく、
０．０３％を超えて添加すると粗大な介在物を生成して
逆に熱間加工性を劣化させるため、上限を０．０３％と
した。Ca is effective in improving hot workability, but if it is less than 0.0005%, the effect is not sufficient.
If added in excess of 0.03%, coarse inclusions are formed and consequently hot workability is degraded, so the upper limit was made 0.03%.
【００２２】Ｍｇは、耐食性および高温強度を向上させ
るが、０．００１％未満ではその効果は小さく、０．０
５％を超えて添加すると粗大な介在物を生成して鋼管の
加工性を低下させるので、上限を０．０５％とした。Mg improves the corrosion resistance and high-temperature strength, but its effect is small at less than 0.001%.
If added in excess of 5%, coarse inclusions are formed and the workability of the steel pipe is reduced, so the upper limit was made 0.05%.
【００２３】Ｂは、低炭素鋼やフェライト系ステンレス
では二次加工性を改善する元素として知られているが、
Ｃｒ含有量が１０％以下で、Ａｌを５％以下含有する本
鋼にも、同様に有効であることがわかった。但し多量の
添加は熱間加工性を劣化させるので、上限を０．０１％
とした。B is known as an element for improving the secondary workability in low carbon steel and ferritic stainless steel.
It was also found that the present steel having a Cr content of 10% or less and Al of 5% or less was similarly effective. However, the addition of a large amount deteriorates hot workability, so the upper limit is 0.01%.
And
【００２４】希土類元素（ＲＥＭ）は、フェライト系ス
テンレスでは酸化皮膜の密着性を向上させ、耐酸化性を
向上させる元素として知られているが、Ｃｒ含有量が１
０％以下で、Ａｌを５％以下含有する本鋼にも、有効で
あることがわかった。添加量が０．００１％未満ではそ
の効果は小さく、多量に添加すると熱間加工性を大きく
低下させ、また介在物を生成して鋼管の加工性を低下さ
せるので、０．１％を上限とした。なお、本発明におけ
る希土類元素とは、原子番号が５７〜７１番および８９
〜１０３番の元素およびＹを指す。A rare earth element (REM) is known as an element which improves the adhesion of an oxide film and improves oxidation resistance in ferritic stainless steel, but has a Cr content of 1%.
It was found that the composition was effective for the steel containing 0% or less and containing 5% or less of Al. If the addition amount is less than 0.001%, the effect is small, and if added in a large amount, the hot workability is greatly reduced, and the inclusions are formed to reduce the workability of the steel pipe. did. In the present invention, the rare earth element has an atomic number of 57 to 71 or 89.
It refers to the # 103 element and Y.
【００２５】つぎに造管方法について説明する。一般に
フェライト系ステンレスでは熱延後、酸洗、冷延、冷延
板焼鈍が必須であるが、本鋼は加工性が良好なため、熱
延後、そのまま造管し、管体熱処理を施すことで自動車
排気系用鋼管として使用可能である。Next, a pipe forming method will be described. Generally, pickling, cold rolling, and cold-rolled sheet annealing are essential for ferritic stainless steel after hot rolling.However, this steel has good workability. It can be used as a steel pipe for automobile exhaust system.
【００２６】従って、本発明では、熱間圧延での板厚は
３ｍｍ以下の最終製品板厚とすることができる。また、
板厚矯正を目的に１０％未満のスキンパスをかけること
も可能である。さらに、熱間圧延機によっては薄い板厚
の制御が困難な場合や、生産性低下が原因で板厚３ｍｍ
以下を得ることが困難な場合があり、これらの場合は、
熱間圧延で板厚１０ｍｍ以下の鋼板として、必要に応じ
て酸洗した後、１０％以上９０％以下の冷間圧延により
最終製品板厚を制御することができる。熱延板の板厚は
１０ｍｍを越え、また冷間圧下率は９０％を越えると冷
間圧延の負荷が増大するため、板厚の上限を１０ｍｍ、
冷間圧下率の上限を９０％とした。冷延鋼板とした場
合、鋼管の加工性も向上する。Therefore, in the present invention, the thickness of the final product can be reduced to 3 mm or less by hot rolling. Also,
It is also possible to apply a skin pass of less than 10% for the purpose of correcting the thickness. Furthermore, depending on the hot rolling mill, it may be difficult to control a thin plate thickness, or the thickness may be reduced to 3 mm due to a decrease in productivity.
It can be difficult to get: In these cases,
After the steel sheet having a thickness of 10 mm or less is hot-rolled, and if necessary, is pickled, the final product thickness can be controlled by cold rolling of 10% or more and 90% or less. If the thickness of the hot rolled sheet exceeds 10 mm, and if the cold rolling reduction exceeds 90%, the load of cold rolling increases, the upper limit of the sheet thickness is 10 mm.
The upper limit of the cold reduction was set to 90%. When a cold-rolled steel sheet is used, the workability of the steel pipe is also improved.
【００２７】得られた熱延鋼板または冷延鋼板は通常の
電縫鋼管として、またはレーザー溶接、ＴＩＧ溶接、プ
ラズマ溶接などにより造管されるが、得られた鋼管に絞
り加工を施すことで、加工性をさらに向上させることが
できる。しかし、絞り率は１％未満では効果が小さく、
その下限を１％とする。絞り加工も大きいほど鋼管の加
工性は向上するが、２０％を越える絞り加工は困難であ
るため、その上限を２０％とした。The obtained hot rolled steel sheet or cold rolled steel sheet is formed as a normal electric resistance welded steel pipe or by laser welding, TIG welding, plasma welding, or the like. Workability can be further improved. However, if the aperture ratio is less than 1%, the effect is small,
The lower limit is 1%. The larger the drawing, the better the workability of the steel pipe, but it is difficult to draw more than 20%, so the upper limit was set to 20%.
【００２８】上述した方法で得られた鋼管を最終的に８
００℃〜１２００℃に加熱し、ついで３００秒以内で４
００℃以下まで冷却することで、再結晶が進行し、粒界
上の析出物が少なく、自動車排気系用鋼管として十分な
加工性を有する鋼管が得られる。加熱温度が８００℃未
満では再結晶が十分に生じないため加工性は低く、加熱
温度が１２００℃より高いと結晶粒が粗大化し加工性は
大きく低下する。また、４００℃以下までの冷却時間は
３００秒を越えると粒界にＣｒ、Ｎｂ、あるいはＭｏを
含む析出物が析出し、加工性を著しく低下させるため、
４００℃以下までの冷却時間は３００秒以内とした。４
００℃以下ではこれらの析出は極めて遅くなるため、放
冷でも良いし、強制空冷、あるいは水冷などでもよいの
で特に限定はしない。なお、本発明鋼の耐酸化性が極め
て良好なため、熱処理は、例えば光輝焼鈍炉のように不
活性ガス雰囲気中で施しても良いし、大気中で誘導加熱
や赤外線加熱を施してもよい。The steel pipe obtained by the above-mentioned method is finally
Heat to 00 ° C to 1200 ° C, then 4 within 300 seconds
By cooling to 00 ° C. or lower, recrystallization proceeds, and precipitates on grain boundaries are reduced, and a steel pipe having sufficient workability as a steel pipe for an automobile exhaust system can be obtained. If the heating temperature is lower than 800 ° C., recrystallization does not sufficiently occur, so that the workability is low. If the heating temperature is higher than 1200 ° C., the crystal grains become coarse and the workability is greatly reduced. Further, if the cooling time to 400 ° C. or less exceeds 300 seconds, precipitates containing Cr, Nb, or Mo are precipitated at the grain boundaries, and the workability is significantly reduced.
The cooling time to 400 ° C. or less was set within 300 seconds. 4
When the temperature is not higher than 00 ° C., the precipitation is extremely slow, so that the precipitation may be carried out, forced air cooling, water cooling, or the like may be used, and thus there is no particular limitation. In addition, since the oxidation resistance of the steel of the present invention is very good, the heat treatment may be performed in an inert gas atmosphere such as a bright annealing furnace, or may be performed by induction heating or infrared heating in the air. .
【００２９】[0029]
【実施例】表１〜４に示す成分を有する鋼を溶製し、表
５、６に示すような板厚の熱延板とした後、実施例６
４、６５、６７、６８は酸洗後に冷間圧延してから通常
の電縫鋼管として造管した。造管の際には溶接部周辺を
不活性ガスでパージし、溶接部に酸化物を巻き込まない
ようにした。実施例１〜６５は造管後、３８．１φ×２
ｔの鋼管を得た。実施例６６〜６８は造管後、１０％絞
り加工を施して、３８．１φ×２ｔの鋼管を得た。得ら
れた鋼管を誘導加熱により熱処理を施した。表５、６に
これらの製造条件を示す。得られた鋼管から３０ｍｍ角
の酸化試験片を採取し、石英容器に入れて９５０℃に加
熱した大気解放の加熱炉に挿入し、２００時間加熱後、
取り出して酸化増量を測定した。酸化増量の測定結果を
表５、６に示す。異常酸化の目安である１ｃｍ2 あたり
２ｍｇ以上のものは測定値を記入し、１ｃｍ2 あたり２
ｍｇ未満は＜２として記入した。また、得られた鋼管か
らＪＩＳ１２Ａ号引張試験片を採取し、引張試験に供し
た。測定した破断伸びを表５、６に示す。EXAMPLE A steel having the components shown in Tables 1 to 4 was melted to form a hot-rolled sheet having a thickness shown in Tables 5 and 6, and then a steel sheet having the composition shown in Tables 5 and 6 was prepared.
Nos. 4, 65, 67 and 68 were cold-rolled after pickling and then made as ordinary ERW steel pipes. At the time of pipe making, the periphery of the welded portion was purged with an inert gas so that oxides were not involved in the welded portion. In Examples 1 to 65, 38.1φ × 2
t steel pipe was obtained. In Examples 66 to 68, 10% drawing was performed after pipe making to obtain a 38.1φ × 2t steel pipe. The obtained steel pipe was heat-treated by induction heating. Tables 5 and 6 show the manufacturing conditions. A 30 mm square oxidation test specimen was collected from the obtained steel pipe, placed in a quartz container, inserted into a heating furnace open to the air heated to 950 ° C., and heated for 200 hours.
It was taken out and the oxidation weight increase was measured. Tables 5 and 6 show the measurement results of the oxidation increase. Abnormality indication above 2mg per 1 cm 2 is oxide ones fill measurements, 1 cm 2 per 2
Less than mg was noted as <2. Further, a JIS No. 12A tensile test piece was collected from the obtained steel pipe and subjected to a tensile test. Tables 5 and 6 show the measured elongation at break.
【００３０】[0030]
【表１】供試鋼の成分（質量％） [Table 1] Composition of test steel (% by mass)
【００３１】[0031]
【表２】供試鋼の成分（質量％）（表１のつづき） [Table 2] Composition of test steel (% by mass) (continued from Table 1)
【００３２】[0032]
【表３】供試鋼の成分（質量％） [Table 3] Composition of test steel (% by mass)
【００３３】[0033]
【表４】供試鋼の成分（質量％）（表３のつづき） [Table 4] Composition of test steel (% by mass) (continued from Table 3)
【００３４】[0034]
【表５】鋼管の製造条件と大気中酸化増加量および伸び Table 5: Manufacturing conditions of steel pipes, increase in oxidation in air and elongation
【００３５】[0035]
【表６】鋼管の製造条件と大気中酸化増加量および伸び
(表５のつづき） [Table 6] Steel pipe manufacturing conditions, atmospheric oxidation increase and elongation
(Continued from Table 5)
【００３６】実施例１〜５６、６４〜６７は本発明例で
あり、酸化増量は２ｍｇ／ｃｍ2 未満であり、また破断
伸びも３５％以上であり、優れた耐酸化性と加工性を有
することから、自動車排気系に適することがわかる。一
方、実施例５７、５９、６０は鋼管の化学成分が本発明
範囲外であり、酸化増量が大きい。実施例５８、６１は
鋼管の化学成分が本発明範囲外であり、伸びが低い。実
施例６２は鋼管の加熱温度が高く、結晶粒が粗大化して
伸びが低下している。実施例６３は鋼管の加熱温度が低
く、再結晶が十分に進まず、伸びが低い。実施例６８は
鋼管加熱後の冷却時間が長く、粒界に析出物が析出し
て、伸びが低い。Examples 1 to 56 and 64 to 67 are examples of the present invention. The weight gain by oxidation is less than 2 mg / cm 2 , the elongation at break is 35% or more, and they have excellent oxidation resistance and workability. From this, it is understood that it is suitable for an automobile exhaust system. On the other hand, in Examples 57, 59, and 60, the chemical components of the steel pipe were out of the range of the present invention, and the oxidation increase was large. In Examples 58 and 61, the chemical composition of the steel pipe was out of the range of the present invention, and the elongation was low. In Example 62, the heating temperature of the steel pipe was high, the crystal grains were coarsened, and the elongation was low. In Example 63, the heating temperature of the steel pipe was low, recrystallization did not proceed sufficiently, and the elongation was low. In Example 68, the cooling time after heating the steel pipe was long, precipitates were precipitated at grain boundaries, and the elongation was low.
【００３７】[0037]
【発明の効果】本発明により、従来の自動車排気系用フ
ェライト系ステンレス鋼管に比べて、成分元素としてＣ
ｒが低く、さらに冷延焼鈍が省略できるため工程コスト
も低い、耐酸化性に優れた自動車排気系鋼管が提供でき
るようになった。今後も、耐酸化性に優れた鋼管の要求
は増加する。従って、本発明により製造された鋼管の効
果は極めて大きいものである。According to the present invention, as compared with the conventional ferritic stainless steel pipe for automobile exhaust system, C as a constituent element
Thus, it is possible to provide an automotive exhaust system steel pipe having a low r and a low process cost since cold rolling annealing can be omitted, and having excellent oxidation resistance. In the future, the demand for steel tubes having excellent oxidation resistance will increase. Therefore, the effect of the steel pipe manufactured according to the present invention is extremely large.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） Ｃ２２Ｃ 38/00 ３０２ Ｃ２２Ｃ 38/00 ３０２Ｚ 38/38 38/38 Ｆターム(参考） 4K032 AA00 AA01 AA02 AA04 AA08 AA09 AA10 AA12 AA14 AA16 AA17 AA19 AA20 AA21 AA22 AA23 AA27 AA29 AA31 AA32 AA33 AA35 AA36 AA37 AA39 AA40 BA03 CF03 CG01 CG02 CH04 CH05 CH06 4K042 AA06 AA24 BA06 BA13 CA02 CA03 CA04 CA05 CA06 CA07 CA08 CA09 CA10 CA12 CA13 CA14 DC02 DE05 DE06 ──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. 7 Identification symbol FI theme coat ゛ (reference) C22C 38/00 302 C22C 38/00 302Z 38/38 38/38 F term (reference) 4K032 AA00 AA01 AA02 AA04 AA08 AA09 AA10 AA12 AA14 AA16 AA17 AA19 AA20 AA21 AA22 AA23 AA27 AA29 AA31 AA32.
Claims (6)
０１５％以下、Ｃｒ：１〜１０％、Ａｌ：０．５〜５
％、Ｓｉ：３％以下、Ｍｎ：３％以下、を含有し、残部
Ｆｅおよび不可避不純物からなる鋼を板厚３ｍｍ以下の
熱延鋼板とした後、造管し、８００℃以上１２００℃以
下に加熱した後、３００秒以内で４００℃以下まで冷却
する、耐酸化性に優れた自動車排気系鋼管の製造方法。(1) C: 0.015% or less in mass%;
015% or less, Cr: 1 to 10%, Al: 0.5 to 5
%, Si: 3% or less, Mn: 3% or less, and a steel consisting of a balance of Fe and unavoidable impurities is made into a hot-rolled steel sheet having a thickness of 3 mm or less. A method for producing an automobile exhaust system steel pipe having excellent oxidation resistance, wherein the pipe is cooled to 400 ° C. or less within 300 seconds after heating.
％でＴｉ：０．０１〜１％、Ｚｒ：０．０１〜１％、Ｈ
ｆ：０．０１〜０．５％、Ｖ：０．０１〜１％、Ｎｂ：
０．０１〜１％、Ｔａ：０．０１〜１％、Ｍｏ：３％以
下、Ｗ：３％以下、のうち１種または２種以上を含有
し、残部Ｆｅおよび不可避不純物からなる鋼を板厚３ｍ
ｍ以下の熱延鋼板とした後、造管し、８００℃以上１２
００℃以下に加熱した後、３００秒以内で４００℃以下
まで冷却する、耐酸化性に優れた自動車排気系鋼管の製
造方法。2. In addition to the components described in claim 1, Ti: 0.01-1%, Zr: 0.01-1%, H
f: 0.01 to 0.5%, V: 0.01 to 1%, Nb:
A steel sheet containing one or more of 0.01 to 1%, Ta: 0.01 to 1%, Mo: 3% or less, and W: 3% or less, with the balance being Fe and inevitable impurities. 3m thick
m and hot rolled steel sheet, pipe forming, 800 ° C or more and 12
A method for producing an automobile exhaust system steel tube having excellent oxidation resistance, wherein the steel tube is cooled to 400 ° C. or less within 300 seconds after being heated to 00 ° C. or less.
らに質量％でＣｕ：１％以下、Ｎｉ：１％以下、Ｃｏ：
３％以下、Ｓｎ：１％以下、Ｓｂ：０．５％以下、Ｃ
ａ：０．０００５〜０．０３％、Ｍｇ：０．００１〜
０．０５％、Ｂ：０．０１％以下、ＲＥＭ：０．００１
〜０．１％、のうち１種または２種以上を含有し、残部
Ｆｅおよび不可避不純物からなる鋼を板厚３ｍｍ以下の
熱延鋼板とした後、造管し、８００℃以上１２００℃以
下に加熱した後、３００秒以内で４００℃以下まで冷却
する、耐酸化性に優れた自動車排気系鋼管の製造方法。3. In addition to the components described in claim 1 or 2, further, in mass%, Cu: 1% or less, Ni: 1% or less, Co:
3% or less, Sn: 1% or less, Sb: 0.5% or less, C
a: 0.0005 to 0.03%, Mg: 0.001 to
0.05%, B: 0.01% or less, REM: 0.001
After forming a hot-rolled steel sheet having a thickness of 3 mm or less from a steel containing one or more of 0.1% or more and a balance of Fe and unavoidable impurities, pipe forming is performed to 800 ° C or more and 1200 ° C or less. A method for producing an automobile exhaust system steel pipe having excellent oxidation resistance, wherein the pipe is cooled to 400 ° C. or less within 300 seconds after heating.
らなる鋼を板厚１０ｍｍ以下の熱延鋼板とした後、１０
％以上９０％以下の冷間圧延を施し、得られた冷延鋼板
を造管した後、８００℃以上１２００℃以下に加熱し、
３００秒以内で４００℃以下まで冷却する、耐酸化性に
優れた自動車排気系鋼管の製造方法。4. A hot-rolled steel sheet having a thickness of 10 mm or less is prepared from a steel comprising the components described in claim 1 or 2 or 3.
% To 90% or less, and the resulting cold-rolled steel sheet is formed into a tube, and then heated to 800 ° C or more and 1200 ° C or less.
A method for producing an automobile exhaust system steel pipe excellent in oxidation resistance, which is cooled to 400 ° C. or less within 300 seconds.
らなる鋼を板厚３ｍｍ以下の熱延鋼板とした後、造管
し、１％以上２０％以下の絞り加工を施した後、８００
℃以上１２００℃以下に加熱し、３００秒以内で４００
℃以下まで冷却する、耐酸化性に優れた自動車排気系鋼
管の製造方法。5. A steel comprising the component according to claim 1 or 2 or 3 is formed into a hot-rolled steel sheet having a thickness of 3 mm or less, then pipe-formed, and subjected to a drawing process of 1% or more and 20% or less. 800
℃ to 1200 ° C, 400 seconds within 300 seconds
A method for manufacturing an automotive exhaust steel pipe having excellent oxidation resistance, which is cooled to a temperature of not more than ℃.
らなる鋼を板厚１０ｍｍ以下の熱延鋼板とした後、１０
％以上９０％以下の冷間圧延を施し、得られた冷延鋼板
を造管し、１％以上２０％以下の絞り加工を施した後、
８００℃以上１２００℃以下に加熱し、３００秒以内で
４００℃以下まで冷却する、耐酸化性に優れた自動車排
気系鋼管の製造方法。6. A hot-rolled steel sheet having a thickness of 10 mm or less made of the steel according to claim 1 or 2 or 3.
% Or less and 90% or less cold-rolled, the resulting cold-rolled steel sheet is formed into a tube, and after drawing 1% or more and 20% or less,
A method for producing a steel pipe for an automobile exhaust system having excellent oxidation resistance, wherein the pipe is heated to 800 ° C. or more and 1200 ° C. or less and cooled to 400 ° C. or less within 300 seconds.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35010299A JP2001164317A (en) | 1999-12-09 | 1999-12-09 | Method for producing automotive exhaust system steel pipe excellent in oxidation resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35010299A JP2001164317A (en) | 1999-12-09 | 1999-12-09 | Method for producing automotive exhaust system steel pipe excellent in oxidation resistance |
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| Publication Number | Publication Date |
|---|---|
| JP2001164317A true JP2001164317A (en) | 2001-06-19 |
Family
ID=18408254
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35010299A Withdrawn JP2001164317A (en) | 1999-12-09 | 1999-12-09 | Method for producing automotive exhaust system steel pipe excellent in oxidation resistance |
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| Country | Link |
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| WO2013178629A1 (en) * | 2012-05-29 | 2013-12-05 | Thyssenkrupp Steel Europe Ag | Heat-resistant fe-al-cr steel |
| CN104060190A (en) * | 2014-07-09 | 2014-09-24 | 上海大学兴化特种不锈钢研究院 | Chromium-saving and nickel-saving type high-silicon heat-resistant stainless steel |
| WO2018215065A1 (en) * | 2017-05-24 | 2018-11-29 | Sandvik Intellectual Property Ab | Ferritic alloy |
| CN109072384A (en) * | 2016-04-22 | 2018-12-21 | 山特维克知识产权股份有限公司 | Alfer |
| WO2021020757A1 (en) * | 2019-07-31 | 2021-02-04 | 주식회사 포스코 | Ferrite-based steel sheet having excellent corrosion resistance for exhaust system |
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1999
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| WO2013178629A1 (en) * | 2012-05-29 | 2013-12-05 | Thyssenkrupp Steel Europe Ag | Heat-resistant fe-al-cr steel |
| CN104060190A (en) * | 2014-07-09 | 2014-09-24 | 上海大学兴化特种不锈钢研究院 | Chromium-saving and nickel-saving type high-silicon heat-resistant stainless steel |
| CN109072384A (en) * | 2016-04-22 | 2018-12-21 | 山特维克知识产权股份有限公司 | Alfer |
| CN113088830A (en) * | 2016-04-22 | 2021-07-09 | 山特维克知识产权股份有限公司 | Ferritic alloy |
| CN113088830B (en) * | 2016-04-22 | 2023-09-01 | 山特维克知识产权股份有限公司 | ferritic alloy |
| WO2018215065A1 (en) * | 2017-05-24 | 2018-11-29 | Sandvik Intellectual Property Ab | Ferritic alloy |
| CN110709529A (en) * | 2017-05-24 | 2020-01-17 | 山特维克知识产权股份有限公司 | Ferritic alloy |
| WO2021020757A1 (en) * | 2019-07-31 | 2021-02-04 | 주식회사 포스코 | Ferrite-based steel sheet having excellent corrosion resistance for exhaust system |
| KR20210015012A (en) * | 2019-07-31 | 2021-02-10 | 주식회사 포스코 | Ferritic steel sheet for exhaust system with excellent corrosion resistance |
| KR102255111B1 (en) | 2019-07-31 | 2021-05-24 | 주식회사 포스코 | Ferritic steel sheet for exhaust system with excellent corrosion resistance |
| EP3981895A4 (en) * | 2019-07-31 | 2022-09-28 | Posco | Ferrite-based steel sheet having excellent corrosion resistance for exhaust system |
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