JPH09122915A - Welding method to prevent ductile fracture of ferritic stainless steel - Google Patents
Welding method to prevent ductile fracture of ferritic stainless steelInfo
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- JPH09122915A JPH09122915A JP30848395A JP30848395A JPH09122915A JP H09122915 A JPH09122915 A JP H09122915A JP 30848395 A JP30848395 A JP 30848395A JP 30848395 A JP30848395 A JP 30848395A JP H09122915 A JPH09122915 A JP H09122915A
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- ferritic stainless
- stainless steel
- ductility
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、フェライト系ステ
ンレス鋼の溶接熱影響部の延性低下割れを防止する溶接
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 welding method for preventing deterioration of ductility cracking in a heat-affected zone of ferritic stainless steel.
【０００２】[0002]
【従来の技術】フェライト系ステンレス鋼は、オーステ
ナイト系ステンレス鋼よりも熱膨張係数が小さく、加熱
・冷却の繰り返される用途に有利であること、応力腐食
割れが発生しないこと、比較的安価であることから、自
動車排ガス経路部材、各種プラント材、建材などの様々
な分野で使用されている。これらの用途には、溶接施工
が頻繁に行われる。2. Description of the Related Art Ferritic stainless steels have a smaller coefficient of thermal expansion than austenitic stainless steels, are advantageous for applications in which heating and cooling are repeated, do not cause stress corrosion cracking, and are relatively inexpensive. Therefore, it is used in various fields such as automobile exhaust path members, various plant materials, and building materials. Welding is frequently used for these applications.
【０００３】フェライト系ステンレス鋼の溶接上の問題
として、溶接部および熱影響部の結晶粒粗大化による
靱性低下、熱影響部の鋭敏化による耐食性の低下、
溶接施工時の高温割れ、などが挙げられる。これらの問
題に対しては、従来からいくつかの対策が採られてお
り、例えば、に対しては母材および溶接心線に結晶粒
の粗大化を抑制する合金元素を添加すること、に対し
てはＮｂ，Ｔｉなどを含む安定化鋼の使用、に対して
は高温割れ感受性を高めるＰ，Ｓなどの合金元素の低
減、などが図られてきた。[0003] Welding problems of ferritic stainless steel include deterioration of toughness due to coarsening of crystal grains in the weld and heat affected zone, deterioration of corrosion resistance due to sensitization of heat affected zone,
Examples include hot cracking during welding. For these problems, some measures have been conventionally taken, for example, for the addition of an alloying element that suppresses the coarsening of crystal grains to the base metal and the welding core wire, As for the use of stabilized steel containing Nb, Ti, etc., reduction of alloying elements such as P, S, etc., which enhances hot cracking susceptibility, has been attempted.
【０００４】[0004]
【発明が解決しようとする課題】しかし、の割れに
は、溶接金属に発生するものばかりでなく、溶接施工方
法によっては熱影響部に発生することもある。この溶接
熱影響部に発生する割れは、液化割れと延性低下割れに
分類できる。前者は粒界に偏析した低融点の化合物が加
熱によって液化して割れに至るものであり、後者は材料
そのものの延性が低下する温度域で割れに至るものであ
る。液化割れに対しては上述のの対策にて、ある程度
防止することが可能であるが、延性低下割れに対して
は、割れを防止する有効な解決手段が明らかにされてい
ないのが実情である。However, not only the cracks that occur in the weld metal but also the cracks that occur in the heat-affected zone depending on the welding method. The cracks generated in the weld heat affected zone can be classified into liquefaction cracks and ductility-decay cracks. In the former, the low-melting-point compound segregated at the grain boundaries is liquefied by heating and leads to cracking, and in the latter, cracking occurs in a temperature range where the ductility of the material itself decreases. Although it is possible to prevent liquefaction cracks to some extent by the above-mentioned countermeasures, it is the actual situation that effective solutions for preventing cracks have been not clarified for ductility-decay cracks. .
【０００５】本発明の目的は、フェライト系ステンレス
鋼の溶接時に発生することのある延性低下割れを再現性
良く防止するための溶接方法を提供することにある。An object of the present invention is to provide a welding method for reproducibly preventing ductility-decreasing cracks that may occur during welding of ferritic stainless steel.
【０００６】[0006]
【課題を解決するための手段】上記目的を達成するため
に、本発明者らは、溶接熱サイクル再現装置を用いた引
張試験により延性低下割れの発生する温度域を明らかに
するとともに、実溶接により延性低下割れが発生する条
件を詳細に検討した。その結果、延性低下割れはフェラ
イト系ステンレス鋼の融点直下の非常に狭い温度域で起
こること、これを安定して防止するには溶接中の溶接部
裏面の最高到達温度および溶接部の溶け込み率を規制す
る必要があることを知見し、本発明に至った。In order to achieve the above object, the inventors of the present invention have clarified the temperature range in which ductility-decay cracking occurs by a tensile test using a welding heat cycle reproducing device, and also perform actual welding. Therefore, the conditions under which ductility-decay cracking occurs were examined in detail. As a result, ductility reduction cracks occur in a very narrow temperature range just below the melting point of ferritic stainless steel.To prevent this stably, the maximum temperature reached on the back surface of the weld during welding and the penetration rate of the weld are determined. The inventors have found that it is necessary to regulate, and have reached the present invention.
【０００７】すなわち、本発明は、質量％において、
Ｃ：０.０３％以下、Ｓｉ：２.０％以下、Ｍｎ：２.０
％以下、Ｃｒ：５.０〜３０.０％、Ｎ：０.０３％以下
を含有し、かつ、Ｎｂ：０.０５〜１.０％、Ｔｉ：０.
０５〜１.０％、Ｍｏ：０.０５〜３.０％、Ｃｕ：０.０
２〜１.０％の１種または２種以上を含有し、残部がＦ
ｅおよび製造上の不可避的な不純物からなるフェライト
系ステンレス鋼の溶接において、溶接中の溶接部裏面の
最高到達温度を当該鋼の融点より１００℃以上低い温度
とし、かつ、下記（１）式で定義される溶け込み率
（％）を２０〜８０％の範囲とする、フェライト系ステ
ンレス鋼の溶接熱影響部の延性低下割れを防止する溶接
方法を提供する。 溶け込み率（％）＝溶け込み深さ／当該被溶接母材の厚さ×１００…（１） ここで、溶け込み深さとは、被溶接母材の溶けた部分の
最頂点（最深部）と溶接する面の表面との距離と定義す
る。That is, the present invention, in mass%,
C: 0.03% or less, Si: 2.0% or less, Mn: 2.0
% Or less, Cr: 5.0 to 30.0%, N: 0.03% or less, and Nb: 0.05 to 1.0%, Ti: 0.0.
05-1.0%, Mo: 0.05-3.0%, Cu: 0.0
2 to 1.0% of 1 type or 2 types or more, with the balance being F
In the welding of ferritic stainless steel consisting of e and inevitable impurities in manufacturing, the maximum temperature reached on the back surface of the welded portion during welding is set to a temperature lower than the melting point of the steel by 100 ° C. or more, and by the following formula (1): Provided is a welding method for preventing a ductility-decreasing crack in a weld heat affected zone of ferritic stainless steel with a defined penetration rate (%) in the range of 20 to 80%. Penetration rate (%) = Penetration depth / Thickness of the base metal to be welded x 100 (1) Here, the penetration depth is the highest peak (the deepest part) of the melted base material to be welded. It is defined as the distance between the surface and the surface.
【０００８】[0008]
【発明の実施の形態】以下に、本発明を特定するための
事項について、限定理由を説明する。BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the matters for specifying the present invention will be described below.
【０００９】ＣとＮは、一般的には高温での強度を高め
るためには重要な元素である。しかし、含有量が多くな
ると加工性および低温靱性の低下をきたすので、それぞ
れ０.０３％以下とする。C and N are generally important elements for increasing the strength at high temperatures. However, if the content is high, the workability and low temperature toughness are deteriorated, so the respective contents are made 0.03% or less.
【００１０】Ｓｉは、耐高温酸化性を改善する元素であ
る。しかし、過剰に添加すると硬質になり、加工性およ
び靱性の劣化をもたらすので、２.０％以下とする。Si is an element that improves the high temperature oxidation resistance. However, if added excessively, it becomes hard and the workability and toughness are deteriorated, so the content is made 2.0% or less.
【００１１】Ｍｎは、表層酸化物の密着性を著しく改善
するため、耐熱用途には積極的に添加する場合がある。
しかし、過剰に添加すると耐食性を劣化させるととも
に、硬質となり、低温靱性や加工性を低下させるので、
２.０％以下とする。Since Mn remarkably improves the adhesion of the surface oxide, it may be positively added for heat resistant applications.
However, if added excessively, it deteriorates the corrosion resistance, becomes hard, and lowers the low temperature toughness and workability.
It should be 2.0% or less.
【００１２】Ｃｒは、耐食性および耐高温酸化性を付与
するために有効な元素であり、５.０％以上の添加を必
要とする。一方、過剰に添加すると鋼の脆化を招き、ま
た、硬質となって加工性を劣化させる他、原料価格が高
くなる。したがって、Ｃｒの範囲は、５.０〜３０.０％
とする。[0012] Cr is an element effective for imparting corrosion resistance and high temperature oxidation resistance, and needs to be added in an amount of 5.0% or more. On the other hand, excessive addition causes embrittlement of the steel, hardens the workability, and raises the raw material cost. Therefore, the range of Cr is 5.0 to 30.0%
And
【００１３】Ｎｂは、高温強度の上昇に有効に作用す
る。高温強度を上昇させるためには少なくとも０.０５
％以上添加する必要がある。一方、Ｎｂを過剰に添加す
ると低温靱性や加工性の低下を招く。高温強度を維持
し、かつ低温靱性や加工性低下にあまり影響を及ぼさな
いように、Ｎｂの範囲は０.０５〜１.０％とする。Nb effectively acts to increase the high temperature strength. At least 0.05 to increase high temperature strength
% Must be added. On the other hand, when Nb is added excessively, the low-temperature toughness and the workability are reduced. The range of Nb is 0.05 to 1.0% so that the high temperature strength is maintained and the low temperature toughness and workability are not adversely affected.
【００１４】Ｔｉは、鋼板のｒ値を向上させ、深絞り性
の向上に有効な元素である。その効果を発揮させるため
には０.０５％以上の添加を必要とする。しかし、過剰
に添加するとＴｉＮを生成しやすく、鋼板におけるヘゲ
疵の発生による歩留低下を招くとともに、溶接性を劣化
させる原因ともなる。したがって、Ｔｉの範囲は０.０
５〜１.０％とする。Ti is an element effective for improving the r value of the steel sheet and improving the deep drawability. In order to exert its effect, addition of 0.05% or more is required. However, if added excessively, TiN is likely to be generated, which causes yield loss due to the occurrence of bald defects in the steel sheet and also causes deterioration of weldability. Therefore, the range of Ti is 0.0
5 to 1.0%.
【００１５】Ｍｏは、耐食性、耐酸化性および高温強度
の改善に有効な元素である。これらの効果を発揮させる
ためには０.０５％以上の添加を必要とする。しかし、
過剰に添加すると鋼の脆化を招く。したがって、Ｍｏの
範囲は０.０５〜３.０％とする。Mo is an element effective in improving corrosion resistance, oxidation resistance and high temperature strength. In order to exert these effects, addition of 0.05% or more is required. But,
If added excessively, the steel becomes brittle. Therefore, the range of Mo is set to 0.05 to 3.0%.
【００１６】Ｃｕは、低温靱性と加工性の両方を向上さ
せるのに有効な元素である。その効果は０.０２％の添
加で顕著となる。しかし、多量に添加すると加工性を阻
害する。したがって、Ｃｕの範囲は０.０２〜１.０％と
する。Cu is an element effective in improving both low temperature toughness and workability. The effect becomes remarkable when 0.02% is added. However, if added in a large amount, workability is impaired. Therefore, the range of Cu is 0.02 to 1.0%.
【００１７】溶接部裏面の最高到達温度は、延性低下割
れを防止するうえで最も重要な因子である。本発明者ら
は、以下の試験研究を重ねた結果、溶接部裏面の最高到
達温度を融点より１００℃以上低い温度とすることを規
定した。The maximum temperature reached on the back surface of the weld is the most important factor in preventing ductility-decay cracking. As a result of repeating the following test studies, the present inventors have specified that the maximum temperature reached on the back surface of the welded portion is set to a temperature lower than the melting point by 100 ° C. or more.
【００１８】現実に熱影響部で発生した延性低下割れの
破面について、いくつかの事例を調査してみると、いず
れの破面も粒界破壊の破面であり、しかも粒界は液化し
ていないことが判った。そこで、まず、各種のフェライ
ト系ステンレス鋼を用いて、延性低下割れ破面の再現を
試みた。図１に、ＳＵＳ４２９相当鋼，ＳＵＳ４４４相
当鋼，ＳＵＳ４３０Ｊ１Ｌ相当鋼を用いて、溶接熱サイ
クル再現装置にて高温引張試験を行った後の板幅の減少
率と引張試験温度との関係を示す。１０００℃から１４
００℃までは、いずれの鋼も良好な延性を示しているこ
とがわかり、この温度範囲では、仮に溶接中熱影響部に
引張応力が加わったとしても、延性的に変形するものと
考えられる。一方、１４００℃を越えると延性は急激に
低下する。そして、１４４０℃以上では粒界破壊を呈す
るようになる。この粒界破壊の破面は、前述の事例調査
で観察された延性低下割れの破面とよく一致しているこ
とを確認した。このことから、溶接熱影響部の延性低下
およびこれに起因した割れは、１４００℃を越え融点
（約１５００℃）までの非常に狭い温度範囲で起こるこ
とが明らかとなった。すなわち、融点より１００℃以上
低い温度であれば良好な延性を示すことがわかった。次
に、この知見をもとに実際の溶接における溶接部裏面の
温度と延性低下割れの関係を種々調査した。その結果、
被溶接母材の溶接部裏面の温度が融点より１００℃以上
低い温度であれば、延性低下割れを再現性良く防止でき
ることを突き止めた。これは、被溶接母材の溶接部の板
厚のうち溶融していない部分（＝板厚−溶け込み深さで
表される部分）の一部にでも延性の良好な領域があれ
ば、板全体としての延性低下割れの発生はくい止められ
るものと考えられる。Examination of some examples of fracture surfaces of ductility-degrading cracks that actually occurred in the heat-affected zone revealed that all fracture surfaces were those of grain boundary fracture, and the grain boundaries were liquefied. Turned out not to. Therefore, first, an attempt was made to reproduce the ductility-decay crack fracture surface using various ferritic stainless steels. FIG. 1 shows the relationship between the reduction rate of the sheet width and the tensile test temperature after performing a high temperature tensile test with a welding heat cycle reproducing device using SUS429 equivalent steel, SUS444 equivalent steel, and SUS430J1L equivalent steel. 1000 ° C to 14
It was found that all of the steels exhibited good ductility up to 00 ° C, and it is considered that in this temperature range, even if tensile stress is applied to the heat-affected zone during welding, ductile deformation occurs. On the other hand, when the temperature exceeds 1400 ° C, the ductility sharply decreases. Then, at 1440 ° C. or higher, the grain boundary breakage occurs. It was confirmed that the fracture surface of this intergranular fracture was in good agreement with the fracture surface of the ductility-decay crack observed in the above-mentioned case study. From this, it became clear that the decrease in ductility of the heat-affected zone of welding and the cracks caused by it occur in a very narrow temperature range from above 1400 ° C to the melting point (about 1500 ° C). That is, it was found that a good ductility is exhibited at a temperature lower than the melting point by 100 ° C. or more. Next, based on this knowledge, various investigations were conducted on the relationship between the temperature on the back surface of the weld and the ductility-decay crack in actual welding. as a result,
It has been found that if the temperature of the back surface of the welded portion of the base metal to be welded is lower than the melting point by 100 ° C. or more, ductile cracking can be prevented with good reproducibility. This is because if there is an area with good ductility even in a part of the unmelted portion (= sheet thickness-penetration depth) of the plate thickness of the welded part of the base metal to be welded, the entire plate It is thought that the occurrence of ductility-decreasing cracks can be stopped.
【００１９】以上の結果から、フェライト系ステンレス
鋼の溶接時の延性低下割れを再現性良く抑制する手段と
して、図２に示すような溶接部裏面の溶接中における最
高到達温度を融点より１００℃以上低い温度とするとい
う事項を規定した。なお、図１に示した鋼の融点はいず
れも約１５００℃であるが、融点は鋼の組成によって変
動する。したがって、使用する鋼に応じて溶接部裏面の
最高到達温度を規定する必要がある。例えば、ＳＵＳ４
２９系，ＳＵＳ４４４系，ＳＵＳ４３０系の鋼であれ
ば、溶接部裏面の最高到達温度を１４００℃以下に規定
すればよい。From the above results, as a means for reproducibly suppressing ductility-decreasing cracks during ferritic stainless steel welding, the maximum temperature reached during welding on the back surface of the welded portion as shown in FIG. The item that the temperature is low is specified. Although the melting points of the steels shown in FIG. 1 are all about 1500 ° C., the melting points vary depending on the composition of the steel. Therefore, it is necessary to specify the maximum ultimate temperature of the back surface of the welded portion according to the steel used. For example, SUS4
For the 29 series, SUS444 series, and SUS430 series steels, the maximum temperature reached on the back surface of the welded portion may be specified to 1400 ° C. or lower.
【００２０】溶け込み率は、２０％未満であると溶接条
件の変動によっては接合不良あるいは接合強度不足を生
じるため、２０％以上とすることが必要である。しか
し、溶け込み率が８０％を越えると、溶接中の溶接部裏
面の最高到達温度が融点−１００℃の温度を越え、延性
低下割れを生じる場合があるため、８０％以下とする。If the penetration rate is less than 20%, poor joining or insufficient joining strength may occur depending on changes in welding conditions, so it is necessary to set it to 20% or more. However, if the penetration rate exceeds 80%, the maximum temperature reached on the back surface of the welded portion during welding may exceed the temperature of the melting point -100 ° C, and ductility degradation cracking may occur, so the content is set to 80% or less.
【００２１】ここで、溶接部裏面の最高到達温度および
溶け込み率の具体的設定手段について述べる。図２に示
すような継手形状では、実溶接施工時においては温度測
定ならびに溶け込み率の測定は事実上できない。そこ
で、例えば、実施工に即した継手のモデルを事前に製作
し、これを種々の溶接入熱条件にて溶接し、溶接部裏面
の最高到達温度が融点より１００℃以上低い温度に、溶
け込み率が２０〜８０％の範囲になるような溶接入熱条
件範囲を選定し、この溶接入熱条件範囲を実溶接施工時
に適用する方法を用いることができる。溶接部裏面の温
度測定としては、例えば、熱電対を複数配列して貼付け
て測温する方法、あるいはサーモグラフィーによる測定
方法などが採用できる。溶け込み率は、例えば、各種の
溶接入熱条件にて溶接した試片から、一試片あたり複数
の断面を採取し、断面研磨後光学顕微鏡観察により測定
して求めることができる。Here, a concrete setting means of the maximum temperature and the penetration rate of the back surface of the welded portion will be described. With the joint shape as shown in FIG. 2, it is practically impossible to measure the temperature and the penetration rate during actual welding. Therefore, for example, a joint model suitable for the actual work is manufactured in advance, welded under various welding heat input conditions, and the maximum penetration temperature of the back surface of the welded portion is 100 ° C or more lower than the melting point. It is possible to use a method in which a welding heat input condition range is selected so as to be in the range of 20 to 80%, and this welding heat input condition range is applied during actual welding. As the temperature measurement of the back surface of the welded portion, for example, a method of arranging and bonding a plurality of thermocouples to measure the temperature, a measurement method by thermography, or the like can be adopted. The penetration rate can be obtained by, for example, collecting a plurality of cross sections for each sample from the samples welded under various welding heat input conditions, measuring the cross sections after polishing the sections, and observing with an optical microscope.
【００２２】ところで、溶接時に熱影響部に発生してい
る応力も延性低下割れ発生に係る重要な因子である。図
３は、図１と同じ供試材を用いて、一定応力を負荷した
状態で試験片を加熱したときに破断する温度を測定した
結果を示す。応力の低下とともに破断温度は上昇し、図
１の結果と同様に１４４０℃以上の温度で粒界破壊を示
すようになる。この時の応力は２.０〜２.５Ｎ／mm2で
ある。一方、１.５Ｎ／mm2以下の応力を負荷した場合に
は、試験片が溶融し始めるまで破断しない。このことか
ら、延性低下割れは溶接時の応力が１.５Ｎ／mm2を越え
る場合に生じる可能性のあることがわかった。したがっ
て、溶接部裏面の最高到達温度と溶け込み率とから選定
した溶接入熱条件を実溶接施工に適用するにあたって
は、溶接熱応力の弾塑性解析等（例えば、溶接力学とそ
の応用；朝倉書店刊参照）により、その値が１.５Ｎ／m
m2以下であることを確認して適用するのが望ましい。By the way, the stress generated in the heat-affected zone during welding is also an important factor for the occurrence of ductility-decay cracking. FIG. 3 shows the results of measuring the temperature at which the test piece fractures when the test piece is heated with a constant stress applied, using the same test material as in FIG. As the stress decreases, the fracture temperature rises, and as with the result shown in FIG. 1, grain boundary fracture is exhibited at a temperature of 1440 ° C. or higher. The stress at this time is 2.0 to 2.5 N / mm 2 . On the other hand, when a stress of 1.5 N / mm 2 or less is applied, the test piece does not break until it begins to melt. From this, it was found that the ductility cracking may occur when the stress during welding exceeds 1.5 N / mm 2 . Therefore, when applying the welding heat input conditions selected from the maximum temperature reached on the backside of the weld and the penetration rate to actual welding, elasto-plastic analysis of welding thermal stress (for example, welding mechanics and its application; published by Asakura Shoten) The value is 1.5 N / m
It is desirable to confirm that it is less than m 2 before applying.
【００２３】本発明の方法は、溶接継手については、Ｊ
ＩＳＺ３００１にいう重ね継手，Ｔ継手，せぎり継手な
ど、溶接継手を構成する被溶接材の一方もしくは両方の
母材の溶け込みが、表面から裏面まで貫通しない施工方
法をとる溶接継手について適用できる。The method of the present invention, for welded joints, is described in J
The present invention can be applied to welded joints such as lap joints, T-joints, and barbed joints referred to in ISZ3001 that employ a construction method in which the penetration of one or both base materials of the welded material forming the welded joint does not penetrate from the front surface to the back surface.
【００２４】溶接方法については特に限定されることは
ない。また、溶接に使用するシールドガスおよび溶接心
線についても、限定されることはない。さらに、フェラ
イト系ステンレス鋼と他の合金との異材継手溶接におい
ても、本発明方法の適用により、フェライト系ステンレ
ス鋼の熱影響部の延性低下割れは防止できる。The welding method is not particularly limited. Further, the shield gas and the welding core wire used for welding are not limited. Furthermore, even in the welding of dissimilar joints between ferritic stainless steel and other alloys, by applying the method of the present invention, it is possible to prevent ductility degradation cracks in the heat-affected zone of ferritic stainless steel.
【００２５】[0025]
【実施例】表１に示す３種類の鋼を溶製し、熱間圧延，
焼鈍および冷間圧延により板厚２.０mmの板とし、９０
０〜１０５０℃の範囲で焼鈍したのち酸洗して溶接試験
用の供試材を得た。これらの供試材を用いて溶接試験を
行い延性低下割れを評価した。表２に溶接条件および結
果を示す。[Examples] Three types of steel shown in Table 1 were melted and hot-rolled.
90 mm thick plate by annealing and cold rolling, 90
It was annealed in the range of 0 to 1050 ° C. and then pickled to obtain a test material for welding test. Welding tests were performed using these test materials to evaluate ductility-decay cracking. Table 2 shows welding conditions and results.
【００２６】[0026]
【表１】 [Table 1]
【００２７】[0027]
【表２】 [Table 2]
【００２８】延性低下割れは、２枚の板を重ねて治具に
て固定し、重ね継手溶接を行った後の割れの有無で評価
した。割れ有無の判定は、溶接部の断面を５箇所切断採
取し、バフ研磨後光学顕微鏡にて割れの有無を検査して
行った。その後エッチングを行い溶け込み率を測定し
た。なお、切断した溶接部断面試片にはあらかじめ溶接
部裏面に熱電対を貼り付けておき、溶接時の最高到達温
度を測定した。なお、供試材の融点は、いずれも約１５
００℃である。Ductility-decreasing cracks were evaluated based on the presence or absence of cracks after two plates were superposed and fixed with a jig, and lap joint welding was performed. The presence / absence of cracks was determined by cutting and collecting 5 sections of the welded portion, buffing, and inspecting for cracks with an optical microscope. Then, etching was performed to measure the penetration rate. In addition, a thermocouple was previously attached to the back surface of the welded section of the cut section specimen of the welded section, and the maximum temperature reached during welding was measured. The melting points of the test materials are about 15
00 ° C.
【００２９】Ｎｏ.１〜１１は、本発明方法によるもの
である。ＴＩＧ溶接，ＭＩＧ溶接およびＭＡＧ溶接のい
ずれの方法で行なっても、溶接部裏面の最高到達温度を
１４００℃（＝融点−１００℃）以下とし、かつ溶け込
み率を２０〜８０％の範囲となるように入熱条件を選定
して溶接すれば、熱影響部の延性低下割れは発生しない
ことが確認できた。Nos. 1 to 11 are based on the method of the present invention. Regardless of the method of TIG welding, MIG welding, and MAG welding, the maximum temperature reached on the back surface of the weld is 1400 ° C (= melting point -100 ° C) or less, and the penetration rate is in the range of 20 to 80%. It was confirmed that if the heat input conditions were selected and welding was performed, ductility-degrading cracks in the heat-affected zone would not occur.
【００３０】Ｎｏ.１２〜１６は、比較方法を示したも
のである。Ｎｏ.１２及びＮｏ.１６は、最高到達温度お
よび溶け込み率が本発明方法から外れているため、延性
低下割れを起こした。また、Ｎｏ.１３は、溶け込み率
は本発明の範囲に含まれるものの、溶接部裏面の最高到
達温度が本発明方法から外れているため、延性低下割れ
を起こした。なお、Ｎｏ.１４およびＮｏ.１５は、溶け
落ちたため溶接部に穴があき製品として使用できなかっ
た。Nos. 12 to 16 show comparison methods. In No. 12 and No. 16, the maximum attainable temperature and the penetration rate were out of the method of the present invention, and therefore ductility-decreasing cracking occurred. Further, in No. 13, although the penetration rate was included in the range of the present invention, the maximum ultimate temperature of the back surface of the welded portion was out of the method of the present invention, so that ductility-decay cracking occurred. Note that No. 14 and No. 15 could not be used as products with holes in the welded portions because they had melted down.
【００３１】[0031]
【発明の効果】本発明は、フェライト系ステンレス鋼の
溶接において延性低下割れが再現性良く防止できる溶接
方法を提供するものであり、特に、種々の構造の溶接継
手に適用できる汎用性の高いものである。したがって、
実際の溶接施行に際しては、本発明で規定する事項を満
足するように個々の状況に応じた適切な溶接条件を設定
することにより、従来は不明確であった溶接条件の許容
範囲を適切に設定することが可能となり、各種溶接現場
における溶接条件の最適化が図られる。INDUSTRIAL APPLICABILITY The present invention provides a welding method capable of reproducibly preventing deterioration of ductility cracking in the welding of ferritic stainless steel, and is particularly versatile and applicable to welded joints of various structures. Is. Therefore,
When actually performing welding, by setting appropriate welding conditions according to each situation so as to satisfy the items specified in the present invention, the allowable range of welding conditions, which was conventionally unclear, is appropriately set. It is possible to optimize the welding conditions at various welding sites.
【図１】高温引張試験の試験温度と板幅減少率の関係を
示すグラフ。FIG. 1 is a graph showing a relationship between a test temperature and a strip width reduction rate in a high temperature tensile test.
【図２】重ね継手，Ｔ継手の溶接部裏面位置を示す断面
図。FIG. 2 is a cross-sectional view showing the back surface position of the welded portion of the lap joint and the T joint.
【図３】応力を負荷した状態で加熱したときの応力値と
破断温度との関係を示すグラフ。FIG. 3 is a graph showing the relationship between the stress value and the rupture temperature when heated under stress.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 // Ｂ２３Ｋ 103:04 (72)発明者 井上 正二 兵庫県尼崎市鶴町１番地 日新製鋼株式会 社技術研究所内 (72)発明者 福村 勝彦 兵庫県尼崎市鶴町１番地 日新製鋼株式会 社技術研究所内─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification number Internal reference number FI Technical indication location // B23K 103: 04 (72) Inventor Shoji Inoue 1 Tsurumachi, Amagasaki City, Hyogo Nisshin Steel Co., Ltd. (72) Inventor Katsuhiko Fukumura, 1 Tsurumachi, Amagasaki City, Hyogo Prefecture Nisshin Steel Co., Ltd. Technical Research Center
Claims (1)
下、Ｓｉ：２.０％以下、Ｍｎ：２.０％以下、Ｃｒ：
５.０〜３０.０％、Ｎ ：０.０３％以下を含有し、か
つＮｂ：０.０５〜１.０％、Ｔｉ：０.０５〜１.０％、
Ｍｏ：０.０５〜３.０％、Ｃｕ：０.０２〜１.０％の１
種または２種以上を含有し、残部がＦｅおよび製造上の
不可避的な不純物からなるフェライト系ステンレス鋼の
溶接において、溶接中の溶接部裏面の最高到達温度を当
該鋼の融点より１００℃以上低い温度とし、かつ、下記
（１）式で定義される溶け込み率（％）を２０〜８０％
の範囲とする、フェライト系ステンレス鋼の溶接熱影響
部の延性低下割れを防止する溶接方法。 溶け込み率（％）＝溶け込み深さ／当該被溶接母材の厚さ×１００…（１）1. In mass%, C: 0.03% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr:
5.0 to 3.0%, N: 0.03% or less, and Nb: 0.05 to 1.0%, Ti: 0.05 to 1.0%,
Mo: 0.05 to 3.0%, Cu: 0.02 to 1.0%, 1
In the welding of ferritic stainless steel containing at least one kind or two or more kinds and the balance being Fe and inevitable impurities in manufacturing, the maximum temperature reached on the back surface of the welded part during welding is 100 ° C or more lower than the melting point of the steel. The temperature is the melting rate (%) defined by the following formula (1) is 20 to 80%.
Welding method for preventing ductility degradation cracking in the heat affected zone of ferritic stainless steel. Penetration rate (%) = penetration depth / thickness of the base material to be welded × 100 ... (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30848395A JP3529520B2 (en) | 1995-11-02 | 1995-11-02 | Welding method to prevent ductility degradation crack of ferritic stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30848395A JP3529520B2 (en) | 1995-11-02 | 1995-11-02 | Welding method to prevent ductility degradation crack of ferritic stainless steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09122915A true JPH09122915A (en) | 1997-05-13 |
| JP3529520B2 JP3529520B2 (en) | 2004-05-24 |
Family
ID=17981565
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30848395A Expired - Lifetime JP3529520B2 (en) | 1995-11-02 | 1995-11-02 | Welding method to prevent ductility degradation crack of ferritic stainless steel |
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| Country | Link |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100455082B1 (en) * | 2000-05-30 | 2004-11-08 | 주식회사 포스코 | Method for manufacturing ferrite stainless steel having a good weldability |
-
1995
- 1995-11-02 JP JP30848395A patent/JP3529520B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100455082B1 (en) * | 2000-05-30 | 2004-11-08 | 주식회사 포스코 | Method for manufacturing ferrite stainless steel having a good weldability |
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| Publication number | Publication date |
|---|---|
| JP3529520B2 (en) | 2004-05-24 |
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