JP2978427B2 - High Mn nonmagnetic steel for cryogenic use and manufacturing method - Google Patents
High Mn nonmagnetic steel for cryogenic use and manufacturing methodInfo
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- JP2978427B2 JP2978427B2 JP7262982A JP26298295A JP2978427B2 JP 2978427 B2 JP2978427 B2 JP 2978427B2 JP 7262982 A JP7262982 A JP 7262982A JP 26298295 A JP26298295 A JP 26298295A JP 2978427 B2 JP2978427 B2 JP 2978427B2
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Description
【０００１】[0001]
【産業上の利用分野】本発明は４Ｋ（-269℃）の極低温
で高強度、高靱性を有する高Mn非磁性鋼とそれに加えて
残留応力を低いレベルに抑えた、高Mn非磁性鋼の製造方
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 high-Mn non-magnetic steel having high strength and high toughness at an extremely low temperature of 4K (-269.degree. C.) and a high-Mn non-magnetic steel in which residual stress is suppressed to a low level. And a method for producing the same.
【０００２】[0002]
【従来技術と発明が解決しようとする課題】近年、大型
超電導マグネットを利用したＭＨＤ発電や核融合炉など
に関する技術が急速に進展している。これらの装置で用
いられる超電導マグネットは、液体ヘリウムにより絶対
温度４Ｋまで冷却された状態で運転されるため、これら
の支持体や構造物は同様の温度まで冷却される。さら
に、これらは強磁場の中で繰り返し高応力が働く。した
がって、このような用途に使用される鋼としては、極低
温で高い耐力と優れた破壊靱性を有する非磁性鋼が必要
とされる。2. Description of the Related Art In recent years, technologies relating to MHD power generation and fusion reactors utilizing large superconducting magnets have been rapidly advancing. Since the superconducting magnet used in these devices is operated in a state where it is cooled to an absolute temperature of 4K by liquid helium, these supports and structures are cooled to the same temperature. Furthermore, these are repeatedly subjected to high stress in a strong magnetic field. Therefore, a nonmagnetic steel having high yield strength and excellent fracture toughness at cryogenic temperatures is required as a steel used for such an application.
【０００３】このようなことから大型超電導マグネット
の構造材料に対しては、４Ｋでの 0.2％YS≧ 1200MPa、
破壊靱性値ＫIC≧ 200MPam 1/2が要求されている。しか
しこのような要求を安定して満足することは容易でなか
った。[0003] Therefore, for the structural material of a large superconducting magnet, 0.2% YS at 4K ≥ 1200 MPa,
Fracture toughness value K IC ≧ 200MPam 1/2 is required. However, it has not been easy to stably satisfy such requirements.
【０００４】これまでに、特公平1- 38850号、 特公平2-
45695号などでは、このような要求に応えるための高Mn
非磁性鋼が提唱されているが、その破壊靱性はシャルピ
衝撃試験によって評価されており、ＪIC試験によって求
められるＫIC値が上述の要求を満足するという保証はな
かったのである。実際に本発明者らの検討によれば、こ
れらの特許で規定された範囲内での鋼であっても、ＫIC
値が前述の要求を満足しない場合が多く存在したのであ
る。Until now, Japanese Patent Publication No. 1-38850, Japanese Patent Publication No. 2-850
No. 45695, etc., requires high Mn to meet such demands.
Non-magnetic steel has been proposed, but its fracture toughness has been evaluated by the Charpy impact test, and there was no guarantee that the K IC value determined by the J IC test would satisfy the above requirements. In fact, according to the present inventors' studies, even if the steel is within the range specified in these patents, K IC
In many cases, the values did not satisfy the above requirements.
【０００５】たとえば、特公平1- 38850号では、Ｃ：0.
03％以下、Ｎ： 0.025％以上という低Ｃ−高Ｎ型の成分
系の鋼を1000℃以上の高温で仕上げ圧延し、溶体化処理
を施さない技術であるが、この場合にはＫIC値はシャル
ピ吸収エネルギで予測されるほどには良好とならない。For example, in Japanese Patent Publication No. 1-38850, C: 0.
This is a technology that finish-rolls steel of low C-high N type composition, which is 03% or less and N: 0.025% or more, at a high temperature of 1000 ° C or more and does not perform solution treatment. In this case, the K IC value is used. Is not as good as predicted by Charpy absorbed energy.
【０００６】いっぽう、特公平2- 45695号では、靱性向
上のための技術的ポイントとしてＳを 0.003％以下とす
ることが強調されているが、このような手段をとっても
ＫIC値はシャルピ吸収エネルギで予測されるほどには良
好とならないのである。[0006] On the other hand, in JP Kokoku 2 45695, although the S as technical point for improving the toughness to be 0.003% or less have been emphasized, very K IC value such means Charpy absorbed energy Is not as good as expected.
【０００７】このような機械的性質に関する問題点に加
えて、従来鋼には次のような加工上の問題点も存在して
いたのである。すなわち、通常このような用途に使用さ
れる非磁性鋼は、圧延終了後1000℃以上に加熱した後水
冷を行う溶体化処理が施される。[0007] In addition to the problems related to mechanical properties, conventional steel has the following processing problems. That is, the non-magnetic steel usually used for such an application is subjected to a solution treatment of heating to 1000 ° C. or more after the completion of rolling and then cooling with water.
【０００８】その目的は加工硬化の影響を取り去り、ま
たＣを固溶させて安定した組織を得るためであるが、そ
の場合に水冷を行うのはCr炭化物の粒界析出によって生
じる靱性の劣化を防止するためである。The purpose is to remove the effect of work hardening and to obtain a stable structure by dissolving C. In this case, water cooling is performed to reduce the toughness caused by grain boundary precipitation of Cr carbide. This is to prevent it.
【０００９】しかしながら、このような処理を施した非
磁性鋼は水冷のままであるため、残留応力が高く、超電
導マグネットの構造体として組み立てる切断・溶接など
の際に変形を生じ、機器としての寸法精度への厳しい要
求を満足する上で大きな問題となっていた。However, since the non-magnetic steel treated as described above is kept water-cooled, it has a high residual stress, and is deformed during cutting and welding for assembling as a superconducting magnet structure. This was a major problem in satisfying the strict requirements for precision.
【００１０】本発明は、４Ｋの極低温での 0.2％YSが 1
200MPa以上の高強度と、ＫIC値で評価される破壊靱性値
が 200MPam1/2 以上の高靱性を有すると同時に、残留応
力を低いレベルに抑えた高Mn非磁性鋼及びその製造方法
を提供することを目的とするものである。According to the present invention, 0.2% YS at an extremely low temperature of 4K is 1%.
Provide high-Mn non-magnetic steel with high strength of 200 MPa or more and high toughness with a fracture toughness value evaluated by K IC value of 200 MPam 1/2 or more, while suppressing residual stress to a low level, and a method for producing the same. It is intended to do so.
【００１１】[0011]
【問題を解決するための手段】本発明者らは、４Ｋでの
高強度、高靱性を安定的に確保する手段について、鋭意
検討を行った。その結果、Ｃ、Ｎなどのオーステナイト
安定化元素やCr炭化物の粒界析出量に影響するNi、Moな
どの合金元素量を適正に制御すると同時に、オーステナ
イト結晶粒径（粒度番号）を適正な範囲に制御すること
により、高強度と高靱性が得られることを見いだし、本
発明に至ったものである。Means for Solving the Problems The present inventors have intensively studied means for stably ensuring high strength and high toughness at 4K. As a result, the amount of austenite stabilizing elements such as C and N, and the amount of alloying elements such as Ni and Mo that affect the amount of grain boundary precipitation of Cr carbide are properly controlled, and the austenite crystal grain size (grain size number) is properly controlled. It has been found that high strength and high toughness can be obtained by controlling the thickness of the steel, and the present invention has been achieved.
【００１２】その第１発明は請求項１に示すように、重
量％にてＣ：0.03〜0.10％、Si：0.05〜0.50％、Mn：10
〜30％、Ｐ： 0.009％以下、Ｓ： 0.003％以下、Ni：２
〜15％、Cu：10〜25％、Mo： 0.5〜 7.0％、Al：0.01〜
0.10％、Ｎ：0.15〜0.24％、Ca：0.0005〜0.0050％を含
有し、かつＸ＝Ni-30C+0.5Moで表されるパラメータＸが
5.50以上であり、残部Ｆｅおよび不可避的不純物からな
る化学成分でオーステナイト結晶粒度番号が 2.0〜 5.0
の範囲であることを特徴とする極低温用高Mn非磁性鋼で
ある。In the first invention, C: 0.03 to 0.10%, Si: 0.05 to 0.50%, Mn: 10% by weight.
~ 30%, P: 0.009% or less, S: 0.003% or less, Ni: 2
~ 15%, Cu: 10 ~ 25%, Mo: 0.5 ~ 7.0%, Al: 0.01 ~
A parameter X containing 0.10%, N: 0.15 to 0.24%, Ca: 0.0005 to 0.0050%, and represented by X = Ni-30C + 0.5Mo
5.50 or more, and the austenite grain size number is 2.0 to 5.0
Is a high-Mn nonmagnetic steel for cryogenic use.
【００１３】第２発明は請求項２に示すように、前記請
求項１の化学成分の鋼に選択添加元素として更に、Cu：
0.01〜 2.0％、Ｂ：0.0005〜0.0030％、Nb、Ｖ、Ti：総
量で0.01〜 2.0％、を１種又は２種以上含有した極低温
用高Mn非磁性鋼である。According to a second aspect of the present invention, as a second aspect, the steel having the chemical composition according to the first aspect further includes Cu:
It is a high Mn nonmagnetic steel for cryogenic use containing one or more of 0.01 to 2.0%, B: 0.0005 to 0.0030%, Nb, V, and Ti: 0.01 to 2.0% in total.
【００１４】さらに、残留応力発生の原因である溶体化
処理の水冷を行わずに４Ｋでの高強度、高靱性を確保す
る手段について種々検討を行った。その結果、Ｃ、Ｎな
どのオーステナイト安定化元素やCr炭化物の粒界析出量
に影響するNi、Moなどの合金化元素量を適正に制御する
と同時に、溶体化処理時の加熱温度を適正な範囲に制御
することにより、溶体化処理時に水冷を行わずとも、高
強度と高靱性が得られることを見いだした。Further, various investigations were made on means for ensuring high strength and high toughness at 4K without performing water cooling of the solution treatment, which is a cause of residual stress. As a result, the amount of austenite stabilizing elements such as C and N and the amount of alloying elements such as Ni and Mo, which affect the amount of grain boundary precipitation of Cr carbide, are properly controlled, and the heating temperature during the solution treatment is set within an appropriate range. It was found that high strength and high toughness can be obtained without controlling water cooling during the solution treatment.
【００１５】その第３発明は請求項４に示すように、前
記請求項１又は２の化学成分の鋼片を1000〜1250℃に加
熱後、 900℃以上の仕上温度で熱間圧延又は鍛造を終了
し空冷あるいは強制冷却を行った後、 950〜1150℃の範
囲で加熱後空冷する溶体化処理を施すことを特徴とする
極低温用高Mn非磁性鋼の製造方法である。According to a third aspect of the present invention, as set forth in claim 4, after the steel slab having the chemical composition of claim 1 or 2 is heated to 1000 to 1250 ° C, hot rolling or forging is performed at a finishing temperature of 900 ° C or more. A method for producing a high-Mn nonmagnetic steel for cryogenic use, characterized by performing a solution treatment of heating at a temperature in the range of 950 to 1150 ° C. and air cooling after completion of air cooling or forced cooling.
【００１６】[0016]
【作用】以下に、本発明における化学成分の限定理由に
ついて説明する。Ｃは、オーステナイトの安定化を通じ
て非磁性の確保および４Ｋでの強度上昇に有効な元素で
ある。添加量が0.03％未満ではこのような効果が乏し
く、一方、0.10％を超えて添加すると、Cr炭化物のオー
ステナイト粒界への析出により靱性や耐食性が劣化す
る。したがって、Ｃ含有量は0.03〜0.10％の範囲とす
る。The reasons for limiting the chemical components in the present invention will be described below. C is an element effective for securing non-magnetism and increasing the strength at 4K through stabilization of austenite. If the addition amount is less than 0.03%, such effects are poor. On the other hand, if the addition amount exceeds 0.10%, toughness and corrosion resistance deteriorate due to precipitation of Cr carbide at austenite grain boundaries. Therefore, the C content is in the range of 0.03 to 0.10%.
【００１７】Siは脱酸のために必須の元素であり、また
強度上昇に有効であるが、0.05％未満では効果が不十分
であり、 0.5％を超えると高温延性および靱性の劣化を
もたらす。したがって、Si含有量は0.05〜0.50％の範囲
とする。Si is an essential element for deoxidation and is effective for increasing the strength. However, if it is less than 0.05%, the effect is insufficient, and if it exceeds 0.5%, high-temperature ductility and toughness are deteriorated. Therefore, the Si content is in the range of 0.05 to 0.50%.
【００１８】Mnは、オーステナイトの安定化と靱性の向
上に有効であるが、10％未満ではα’マルテンサイトな
どの析出により非磁性が失われ、強磁性となる。また、
30％を超えて過多に添加すると、熱間加工性と靱性が劣
化する。したがって、Mn含有量は10〜30％の範囲とす
る。Mn is effective for stabilizing austenite and improving toughness. However, if it is less than 10%, nonmagnetic properties are lost due to precipitation of α ′ martensite and the like, and Mn becomes ferromagnetic. Also,
Excessive addition exceeding 30% deteriorates hot workability and toughness. Therefore, the Mn content is in the range of 10 to 30%.
【００１９】Ｐ、Ｓは熱間加工性を損なう不純物元素で
あり、またオーステナイト鋼においては両元素を同時に
低減することにより、それらを単独に低減する場合より
も大きなＫIC値の向上効果が得られる。そこで、Ｐは
0.009％以下、かつＳは 0.003％以下とする。P and S are impurity elements which impair hot workability. In the case of austenitic steel, by simultaneously reducing both elements, a greater effect of increasing the K IC value than when reducing them alone is obtained. Can be So P
0.009% or less and S should be 0.003% or less.
【００２０】Niはオーステナイトの安定化と靱性の向
上、さらにδフェライトの生成抑制に有効な元素である
が、２％未満ではこのような優れた効果が小さい。いっ
ぽう、15％よりも過剰に添加してもその効果は飽和して
いる。よって、Ni含有量は２〜15％の範囲とする。Ni is an element effective for stabilizing austenite, improving toughness, and suppressing the formation of δ-ferrite, but if it is less than 2%, such excellent effects are small. On the other hand, the effect is saturated even if it is added in excess of 15%. Therefore, the Ni content is in the range of 2 to 15%.
【００２１】Crはオーステナイトを安定化し、耐銹性を
付与するために必要であり、耐力を向上させる元素であ
るが、含有量が10％未満ではこの効果がなく、25％を超
えると熱間加工性、靱性を低下させる。したがって、Cr
含有量は10〜25％の範囲とする。Cr is necessary for stabilizing austenite and imparting rust resistance, and is an element for improving proof stress. However, if the content is less than 10%, this effect is not obtained. Decreases workability and toughness. Therefore, Cr
The content is in the range of 10 to 25%.
【００２２】Moは強度の上昇に効果があるだけでなく、
Cr炭化物の粒界析出に起因した靱性の劣化を防止するの
に有効である。このような効果は 0.5％未満では得られ
ず、また７％を超えるとその効果は飽和する。よって、
Mo添加量は 0.5〜 7.0％の範囲とする。Mo not only has the effect of increasing the strength,
This is effective for preventing the deterioration of toughness due to the precipitation of Cr carbide at the grain boundary. Such an effect cannot be obtained at less than 0.5%, and the effect saturates at more than 7%. Therefore,
The amount of Mo added is in the range of 0.5 to 7.0%.
【００２３】Alは結晶粒の微細化による強度上昇を目的
として用いるが、0.01％未満では十分な効果が得られ
ず、いっぽう、0.10％を超えると靱性が劣化する。した
がって、Al含有量は0.01〜0.10％の範囲とする。Al is used for the purpose of increasing the strength by refining the crystal grains, but if it is less than 0.01%, a sufficient effect cannot be obtained, while if it exceeds 0.10%, the toughness deteriorates. Therefore, the Al content is in the range of 0.01 to 0.10%.
【００２４】ＮはＣと同様にオーステナイトの安定化と
４Ｋでの耐力向上に有効である。ＣはCr炭化物の粒界析
出による靱性劣化をもたらすが、Ｎはかかる悪影響をお
よぼさない。上記効果を発現させるためには、0.15％以
上が必要であるが、0.24％を超えると靱性の劣化が著し
い。よって、Ｎ添加量は0.15〜0.24％の範囲とする。N, like C, is effective for stabilizing austenite and improving the proof stress at 4K. C causes toughness deterioration due to grain boundary precipitation of Cr carbide, but N does not have such an adverse effect. 0.15% or more is required to exhibit the above effects, but if it exceeds 0.24%, the toughness is significantly deteriorated. Therefore, the amount of N added is set in the range of 0.15 to 0.24%.
【００２５】Caは0.0005％以上の添加で介在物の球状化
作用をもたらし、靱性を向上させるが、0.0050％を超え
て添加すると清浄度を悪化させ靱性が失われる、Caの添
加量は0.0005〜0.0050％の範囲とする。When Ca is added in an amount of 0.0005% or more, it causes a spheroidizing effect of inclusions and improves toughness. However, when added in excess of 0.0050%, cleanliness is deteriorated and toughness is lost. The range is 0.0050%.
【００２６】この他に耐力向上のためCu、Ｂ、Nb、Ｖ、
Tiの１種又は２種以上を含有することができる。In addition, Cu, B, Nb, V,
One or more of Ti can be contained.
【００２７】Cuはオーステナイト地を強化し耐力の上昇
に有効であるが、添加量が0.01％未満ではそのような効
果は得られず、 2.0％を超えると熱間加工性を劣化させ
る。よって、Cu添加量は0.01〜 2.0％の範囲とする。Cu is effective in strengthening austenite ground and increasing the proof stress. However, such an effect cannot be obtained if the addition amount is less than 0.01%, and the hot workability is deteriorated if the addition amount exceeds 2.0%. Therefore, the added amount of Cu is set in the range of 0.01 to 2.0%.
【００２８】Ｂはオーステナイト粒界に偏析することに
より粒界破壊を防止し耐力を向上させる効果を有する
が、添加量が0.0005％未満ではその効果は得られず、0.
0030％を超えると靱性が劣化する。よって、Ｂ添加量は
0.0005〜0.0030％の範囲とする。B has the effect of preventing grain boundary destruction and improving proof stress by segregating at austenite grain boundaries. However, the effect is not obtained when the amount of addition is less than 0.0005%.
If it exceeds 0030%, the toughness deteriorates. Therefore, the amount of B added is
The range is 0.0005 to 0.0030%.
【００２９】Nb、Ｖ、Tiは炭窒化物を作り、析出強化に
よる耐力向上に有効であり、含有量が0.01％未満ではそ
の効果はなく、 2.0％を超えて添加すると靱性が劣化す
る。したがって、Nb、Ｖ、Ti含有量は総量で0.01〜 2.0
％の範囲とする。Nb, V, and Ti form carbonitrides and are effective for improving the yield strength by precipitation strengthening. If the content is less than 0.01%, the effect is not obtained, and if the content exceeds 2.0%, the toughness is deteriorated. Therefore, the total content of Nb, V, and Ti is 0.01 to 2.0.
% Range.
【００３０】次に、本発明においての請求項１、請求項
２においてオーステナイト結晶粒度番号とＣ、Ni、Mo量
の関係を限定した理由を説明する。Next, the reason why the relationship between the austenite grain size number and the amounts of C, Ni and Mo in claims 1 and 2 of the present invention will be described.
【００３１】一般に、非磁性鋼の靱性はCr炭化物の粒界
析出によって大きく影響を受け、析出量が多いほど靱性
は劣化する。そこで、本発明者らは、析出サイトとして
の粒界面積を決定するオーストナイト結晶粒径と、Cr炭
化物の析出速度に影響を及ぼす上記の各元素に着目し
て、種々の検討を行った。Generally, the toughness of a nonmagnetic steel is greatly affected by the grain boundary precipitation of Cr carbide, and the toughness deteriorates as the amount of precipitation increases. Thus, the present inventors have conducted various studies focusing on the austenitic crystal grain size that determines the grain boundary area as a precipitation site and the above-mentioned elements that affect the precipitation rate of Cr carbide.
【００３２】用いた鋼は板厚30mmの高Mn非磁性鋼であ
り、その化学成分を表１に示す。The steel used was a high-Mn non-magnetic steel sheet having a thickness of 30 mm, and its chemical composition is shown in Table 1.
【００３３】[0033]
【表１】 [Table 1]
【００３４】この鋼に種々の温度での溶体化処理を施す
ことにより、オーストナイト結晶粒径を広い範囲で変化
させた。４Ｋでの破壊靱性（ＫIC値）に及ぼすオースト
ナイト結晶粒度番号の影響を第１図に示す。なお、ＫIC
値はASTM Ｅ813-89に規定されたＪIC試験により求め
た。By subjecting the steel to a solution treatment at various temperatures, the austenite crystal grain size was changed over a wide range. FIG. 1 shows the effect of the austenite grain size number on the fracture toughness (K IC value) at 4K. Note that K IC
Values were determined by J IC test specified in ASTM E813-89.
【００３５】この図からは、オーストナイト結晶粒度番
号が低下（結晶粒が粗大化）するほど破壊靱性は向上
し、200MPam1/2以上を確保するためには、オーステナイ
ト結晶粒度番号を 5.0以下とする必要があることがわか
る。これは、結晶粒が粗大化し粒界面積が減少するほ
ど、靱性を劣化させるCr炭化物の粒界析出量が減少する
ためと考える。From this figure, it can be seen that the fracture toughness increases as the austenite grain size number decreases (crystal grains become coarser), and in order to secure 200 MPam 1/2 or more, the austenite grain size number is set to 5.0 or less. You need to do that. This is considered to be due to the fact that as the crystal grains become coarser and the grain boundary area decreases, the amount of grain boundary precipitation of Cr carbide that deteriorates toughness decreases.
【００３６】いっぽう、図２からわかるように、４Ｋで
の 0.2％YS≧ 1200MPa、という要求を満足させる観点か
らは、オーステナイト結晶粒度番号が低下（結晶粒が粗
大化）しすぎると強度を確保することができず、 2.0以
上とする必要がある。On the other hand, as can be seen from FIG. 2, from the viewpoint of satisfying the requirement that 0.2% YS ≧ 1200 MPa at 4K, the strength is secured when the austenite grain size number is too low (crystal grains are too coarse). I can't do that and need to be 2.0 or higher.
【００３７】次に、Cr炭化物の粒界析出速度に大きな影
響を及ぼすＣ、Ni、Mo量に関する検討結果について述べ
る。Next, the results of studies on the amounts of C, Ni, and Mo, which greatly affect the grain boundary precipitation rate of Cr carbide, will be described.
【００３８】Ｃ、Ni、Mo量を種々変化させ、オーステナ
イト結晶粒度番号を約 3.5に固定した場合の４Ｋでの破
壊靱性（ＫIC値）を測定した結果、図３に示すように、
ＫIC値はパラメータＸ＝Ni-30C+0.5Mo（％）と相関があ
り、このパラメータＸが5.50以上の範囲でＫICは200MPa
m1/2以上の良好な値となるのである。As a result of measuring the fracture toughness (K IC value) at 4K when the austenite grain size number was fixed to about 3.5 while varying the amounts of C, Ni and Mo, as shown in FIG.
The K IC value has a correlation with the parameter X = Ni-30C + 0.5Mo (%). When the parameter X is in the range of 5.50 or more, the K IC is 200 MPa.
This is a good value of m 1/2 or more.
【００３９】以上が、本発明においてオーステナイト結
晶粒度番号とＣ、Ni、Mo量の関係を限定した理由であっ
て、この両者を同時に満たすことにより、結晶粒が粗大
化し粒界面積が減少するとともに、Cr炭化物の粒界析出
が抑えられるため、４Ｋでの0.2％耐力が 1200MPa以
上、破壊靱性値ＫICが 200MPam 1/2以上の良好な値が得
られるものと考えられる。The above is the reason for limiting the relationship between the austenite grain size number and the amounts of C, Ni and Mo in the present invention. By satisfying both of them simultaneously, the crystal grains become coarse and the grain boundary area decreases. It is considered that since the grain boundary precipitation of Cr carbide is suppressed, good values such as 0.2% proof stress at 4K of 1200 MPa or more and fracture toughness value K IC of 200 MPam 1/2 or more can be obtained.
【００４０】次に、残留応力が小さく、破壊靱性の良好
な極低温用高Mn非磁性鋼の製造方法の請求項４の製造条
件の限定理由を説明する。Next, the reason for limiting the production conditions in claim 4 of the method for producing a cryogenic high-Mn nonmagnetic steel having low residual stress and good fracture toughness will be described.
【００４１】一般に高Mn系非磁性鋼は炭素鋼や低合金鋼
に比べて熱間加工性が劣り、適正な条件で鍛造あるいは
圧延を行わないと、鋼片、鋼板の表面に割れが生じ、歩
留の低下を招く。このような観点からは鋼塊の加熱条
件、圧延条件の厳密な管理が重要であり、加熱温度を10
00〜1250℃とし、仕上温度を 900℃以上とする必要があ
る。その後の冷却は空冷あるいは強制冷却のいずれでも
よい。In general, high-Mn nonmagnetic steel is inferior in hot workability to carbon steel and low-alloy steel, and if not forged or rolled under appropriate conditions, cracks occur on the surfaces of billets and steel sheets, This leads to a decrease in yield. From such a viewpoint, strict control of the heating conditions and rolling conditions of the ingot is important.
The temperature must be between 00 and 1250 ° C and the finishing temperature must be 900 ° C or higher. Subsequent cooling may be either air cooling or forced cooling.
【００４２】溶体化処理の条件として、冷却を空冷とす
ることが本発明の大きな特徴である。従来は溶体化処理
時に水冷を行い所定の靱性を確保していたが、水冷によ
って生じる残留応力の問題を解決するためには空冷を行
う必要がある。しかしながら、単に空冷を実施するだけ
ではCr炭化物が粒界析出し靱性は劣化する。したがっ
て、この問題を解決することが本発明の最大のポイント
であり、以下に検討結果を説明する。As a condition of the solution treatment, it is a great feature of the present invention that the cooling is air cooling. Conventionally, water cooling was performed during solution treatment to ensure a predetermined toughness. However, air cooling must be performed to solve the problem of residual stress caused by water cooling. However, mere execution of air cooling causes the precipitation of Cr carbide at the grain boundaries and deteriorates the toughness. Therefore, solving this problem is the most important point of the present invention, and the examination results will be described below.
【００４３】本発明者らは、溶体化処理時に空冷を行っ
ても靱性の劣化が生じない製造条件を鋭意検討した。こ
こでは、溶体化処理時の加熱温度に注目し、加熱温度を
種々変化させ、冷却時に水冷および空冷を行った場合の
靱性の変化挙動を調査した。用いた鋼は板厚30mmの高Mn
非磁性鋼であり、その化学成分を表２に示す。The present inventors have intensively studied manufacturing conditions under which toughness does not deteriorate even if air cooling is performed during the solution treatment. Here, focusing on the heating temperature during the solution treatment, the heating temperature was variously changed, and the change behavior of toughness when water cooling and air cooling were performed during cooling was investigated. The steel used was high Mn with a thickness of 30 mm.
It is a non-magnetic steel, and its chemical components are shown in Table 2.
【００４４】[0044]
【表２】 [Table 2]
【００４５】４Ｋでの破壊靱性（ＫIC値）に及ぼす溶体
化処理時の加熱温度の影響を図４に示す。ＫIC値はASTM
E813-89に規定されたＪIC試験により求めた。この図か
らは、溶体化処理時の加熱温度が上昇するほど破壊靱性
は向上すること、特に 950℃以上では空冷材の方が水冷
材よりも良好となることがわかる。従来は溶体化処理時
の冷却は水冷とすることが常識であり、このような現象
は全く新規な知見である。このような現象が表れる原因
は次のように考えられる。すなわち、溶体化処理時の加
熱温度が高い場合には、結晶粒が粗大化し粒界面積が
減少するため、靱性を劣化させるCr炭化物の粒界析出量
が減少すること、Cr炭化物の粒界析出量が最も多い温
度域は 600℃から 800℃の範囲であるが、加熱温度を 9
50℃以上にし、かつ、空冷を行うとCr炭化物は 800℃以
上の温度で粒内析出するため、結果として粒界析出量が
減少すること、などによるものと考えられる。FIG. 4 shows the effect of the heating temperature during the solution treatment on the fracture toughness (K IC value) at 4K. K IC value is ASTM
It was determined by J IC test specified in E813-89. From this figure, it is understood that the fracture toughness is improved as the heating temperature during the solution treatment is increased, and in particular, at 950 ° C. or higher, the air-cooled material is better than the water-cooled material. Conventionally, it is common knowledge that the cooling during the solution treatment is water-cooled, and such a phenomenon is completely new knowledge. The cause of such a phenomenon is considered as follows. In other words, when the heating temperature during the solution treatment is high, the crystal grains are coarsened and the grain boundary area is reduced, so that the amount of grain boundary precipitation of Cr carbide that deteriorates toughness is reduced, and that the grain boundary precipitation of Cr carbide is reduced. The temperature range with the highest volume is in the range of 600 to 800 ° C.
It is considered that when the temperature is increased to 50 ° C. or more and air cooling is performed, Cr carbide precipitates at a temperature of 800 ° C. or more, resulting in a decrease in the amount of grain boundary precipitation.
【００４６】いっぽう、４Ｋでの 0.2％YSに及ぼす加熱
温度の影響を図５に示す。この図から、溶体化処理時の
加熱温度が上昇するほど結晶粒が粗大化するため 0.2％
YSは低下し、 0.2％YS≧ 1200MPaを満足するためには加
熱温度は1150℃以下とする必要があることがわかる。On the other hand, FIG. 5 shows the effect of the heating temperature on 0.2% YS at 4K. From this figure, it can be seen that as the heating temperature during the solution treatment increases, the crystal grains become coarser,
It can be seen that the YS decreases and the heating temperature must be 1150 ° C. or lower to satisfy 0.2% YS ≧ 1200 MPa.
【００４７】次に、４Ｋにおける強度、靱性に及ぼすMo
の影響を図６に示す。用いた鋼は、板厚30mmで化学成分
を表３に示す。適用した溶体化処理は加熱温度1050℃の
水冷および空冷処理である。Next, the effect of Mo on the strength and toughness at 4K
FIG. The steel used has a thickness of 30 mm and the chemical composition is shown in Table 3. The solution treatment applied was water cooling at a heating temperature of 1050 ° C. and air cooling.
【００４８】[0048]
【表３】 この図より、以下の３つのことが分かる。 (1) Mo量が多いほど強度は上昇し、空冷材において 0.2
％YS≧ 1200MPaを満足するためには、Moは 0.5％以上必
要である。 (2) Mo量が多いほど靱性は劣化し、空冷材においてＫIC
≧ 200MPam 1/2を満足するためには、Moは 7.0％以下と
する必要がある。 (3) Mo量が１％以下の場合は、水冷、空冷材ともに強度
はほぼ同等であるが、１％を超える場合は空冷材の方が
水冷材よりも強度が高くなり、その差はMo量が多いほど
大きくなる。 (3) のような現象は全く新規な知見である。一般に低合
金鋼の場合は、水冷するとマルテンサイトやベイナイト
に変態するため水冷材の方が、空冷材よりも強度は高く
なる。しかしながら、一般的な高Mn鋼の場合では、変態
せず室温でもオーステナイトのままであるため、強度は
結晶粒の大きさにより決まり、水冷材、空冷材とも強度
はほぼ等しい。[Table 3] This figure shows the following three points. (1) The higher the Mo content, the higher the strength.
In order to satisfy% YS ≧ 1200MPa, Mo must be 0.5% or more. (2) toughness as Mo amount is large to degrade, K IC in air material
In order to satisfy ≧ 200MPam 1/2 , Mo needs to be 7.0% or less. (3) When the amount of Mo is 1% or less, the strength of both water-cooled and air-cooled materials is almost the same, but when it exceeds 1%, the strength of air-cooled materials is higher than that of water-cooled materials, and the difference is Mo. The larger the amount, the larger. Phenomena such as (3) are completely new findings. Generally, in the case of low-alloy steel, when water-cooled, it transforms into martensite or bainite, so that the strength of the water-cooled material is higher than that of the air-cooled material. However, in the case of a general high-Mn steel, since it does not transform and remains austenite even at room temperature, the strength is determined by the size of the crystal grains, and the strength of the water-cooled material and the air-cooled material is almost equal.
【００４９】本鋼板では、Mo量が１％を超える場合は空
冷材の方が水冷材よりも強度が高くなり、その差はMo量
が多い程大きくなる。この理由は、空冷中に析出するMo
炭化物の析出強化によるものと考えられる。本鋼板は空
冷を実施しているため析出物の粒子径はある程度大きく
なっている。そのため、強化への寄与は小さく、ある程
度析出物が存在してはじめて効果が現れると考えられ
る。従って、Mo量が１％を超えてはじめて析出物の粒子
数も多くなり、水冷材に比べて強度が高くなる。また、
Mo量が増加するほど析出物の粒子数も増加するため水冷
材に対する強度差も大きくなる。In the present steel sheet, when the Mo content exceeds 1%, the strength of the air-cooled material is higher than that of the water-cooled material, and the difference increases as the Mo content increases. The reason for this is that Mo precipitates during air cooling.
It is thought to be due to precipitation strengthening of carbides. Since the steel sheet is air-cooled, the particle size of the precipitate is somewhat large. Therefore, it is considered that the contribution to strengthening is small, and the effect appears only when precipitates are present to some extent. Therefore, only when the Mo amount exceeds 1%, the number of particles of the precipitates increases, and the strength becomes higher than that of the water-cooled material. Also,
As the amount of Mo increases, the number of particles of the precipitate increases, so that the difference in strength with respect to the water-cooled material also increases.
【００５０】なお、このような空冷による靱性改善効果
を発揮させるためには、Cr炭化物の粒界析出挙動に大き
な影響を及ぼすＣ、Ni、Mo量を規制する必要がある。す
なわち、図７に示すように、 950℃に加熱し空冷を行っ
た場合の４Ｋでの破壊靱性（ＫIC値）はＸ＝Ni-30C+0.5
Mo（％）と相関があり、このパラメータＸが5.50以上の
範囲でＫICは200MPam1/2以上の良好な値となるのであ
る。In order to exert the effect of improving toughness by such air cooling, it is necessary to regulate the amounts of C, Ni and Mo which have a great effect on the grain boundary precipitation behavior of Cr carbide. That is, as shown in FIG. 7, the fracture toughness (K IC value) at 4K when heated to 950 ° C. and air-cooled is X = Ni-30C + 0.5.
There is a correlation with Mo (%), and when this parameter X is in the range of 5.50 or more, K IC becomes a good value of 200 MPam 1/2 or more.
【００５１】[0051]
【実施例】以下に実施例を挙げて本発明を説明するが、
本発明はこれらの実施例により何ら限定されるものでは
ない。EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.
【００５２】表４に示す種々の化学成分、オーステナイ
ト結晶粒度番号を有する鋼板を製造した。Steel sheets having various chemical components and austenite grain size numbers shown in Table 4 were produced.
【００５３】[0053]
【表４】 [Table 4]
【００５４】表４及び図８に示すように本発明の請求範
囲に属する略号Ａ〜Ｊの鋼板は、適切な化学成分とオー
ステナイト結晶粒度番号、パラメータＸを有するため、
４Ｋにおいて200MPam1/2以上のＫICと 1200MPa以上の
0.2％YSを有している。これに対して、略号Ｋ、Ｌでは
オーステナイト結晶粒度番号が大きいためＫICが低く、
略号Ｍではオーステナイト結晶粒度番号が小さいため強
度が低く、略号ＮおよびＯではNi、Ｃ、Moで計算される
パラメータＸが小さいため、ＫICが低い値にとどまって
いる。As shown in Table 4 and FIG. 8, the steel sheets of the abbreviations A to J belonging to the claims of the present invention have appropriate chemical components, austenite grain size numbers, and parameters X.
200Kam 1/2 or more K IC at 4K and 1200MPa or more
Has 0.2% YS. In contrast, in the abbreviations K and L, the austenite grain size number is large, so that K IC is low,
In the abbreviation M, the austenite grain size number is small, so that the strength is low. In the abbreviations N and O, the parameter X calculated by Ni, C, and Mo is small, so that K IC remains at a low value.
【００５５】次に、表５及び表６に示す種々の化学成
分、製造条件にて鋼板を製造した。Next, steel sheets were manufactured under various chemical components and manufacturing conditions shown in Tables 5 and 6.
【００５６】[0056]
【表５】 [Table 5]
【００５７】[0057]
【表６】 [Table 6]
【００５８】表５、表６及び図９に示すように、本発明
の請求範囲に属する略号Ａ〜Ｊの鋼板は、適切な化学成
分と高温に加熱後空冷を行う溶体化処理を行っているた
め、４Ｋにおいて200MPam1/2以上のＫICと 1200MPa以上
の 0.2％YSを有しており、また残留応力もほとんどな
い。これに対して、略号Ｋでは加熱温度が低いため、略
号ＬおよびＭではNi、Ｃ、Moで計算されるパラメータＸ
が小さいため、いずれもＫICが低い値にとどまってい
る。いっぽう略号Ｎでは溶体化処理時に水冷を行ってい
るため、残留応力が極めて高い。なお、残留応力の測定
は穿孔法によった。As shown in Tables 5 and 6, and FIG. 9, the steel sheets of the abbreviations A to J belonging to the claims of the present invention have been subjected to a solution treatment of heating to an appropriate chemical component, high temperature, and air cooling. Therefore, it has a K IC of 200MPam 1/2 or more at 4K, 0.2% YS of 1200MPa or more, and almost no residual stress. On the other hand, since the heating temperature is low in the abbreviation K, the parameters X calculated by Ni, C, and Mo are used in the abbreviations L and M.
Are small, the K IC remains at a low value in all cases. On the other hand, in the abbreviation N, the residual stress is extremely high because water cooling is performed during the solution treatment. The measurement of the residual stress was based on the perforation method.
【００５９】[0059]
【発明の効果】本発明によれば、極低温で高強度、高靱
性を有し、しかも残留応力の小さい極低温用高Mn非磁性
鋼が容易に製造でき、これをＭＨＤ発電や核融合炉など
に用いられる大型超電導マグネットの構造材料に適用で
き、この分野の技術の発展に多大に貢献できるものであ
る。According to the present invention, high Mn non-magnetic steel for cryogenic use which has high strength and high toughness at cryogenic temperature and low residual stress can be easily manufactured. It can be applied to the structural materials of large superconducting magnets used for such applications, and can greatly contribute to the development of technology in this field.
【図面の簡単な説明】[Brief description of the drawings]
【図１】表１に示す材料のオーステナイト結晶粒度によ
る４ＫでのＫICへの影響を示した図である。FIG. 1 is a graph showing the effect of austenite grain size of the materials shown in Table 1 on K IC at 4K.
【図２】表１に示す材料のオーステナイト結晶粒度によ
る４Ｋでの 0.2％YSへの影響を示した図である。FIG. 2 is a graph showing the effect of austenite grain size of the materials shown in Table 1 on 0.2% YS at 4K.
【図３】オーステナイト結晶粒度番号を約 3.5に固定し
た場合の４ＫでのＫIC値に及ぼすＸパラメータの影響を
示した図である。FIG. 3 is a diagram showing the effect of the X parameter on the K IC value at 4K when the austenite grain size number is fixed at about 3.5.
【図４】４ＫでのＫIC値に及ぼす溶体化処理の加熱温度
の影響を示した図である。FIG. 4 is a diagram showing the effect of the heating temperature of the solution treatment on the K IC value at 4K.
【図５】４Ｋでの 0.2％ＹＳ値に及ぼす溶体化処理の加
熱温度の影響を示した図である。FIG. 5 is a diagram showing the effect of the heating temperature of the solution treatment on the 0.2% YS value at 4K.
【図６】４Ｋでの強度、靱性に及ぼすMoの影響を示した
図である。FIG. 6 is a diagram showing the effect of Mo on strength and toughness at 4K.
【図７】950℃に加熱し空冷を行った場合の４ＫでのＫ
IC値に及ぼすＸパラメータの影響を示した図である。FIG. 7: K at 4K when heated to 950 ° C. and air-cooled
FIG. 3 is a diagram illustrating the influence of an X parameter on an IC value.
【図８】表４に示す鋼の強度、靱性の測定結果を示す図
である。FIG. 8 is a diagram showing measurement results of strength and toughness of steel shown in Table 4.
【図９】表５に示す鋼の強度、靱性、残留応力の測定結
果を示す図である。FIG. 9 is a diagram showing measurement results of strength, toughness, and residual stress of steel shown in Table 5.
フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) C22C 38/00 - 38/60 C21D 8/00 Continuation of front page (58) Field surveyed (Int. Cl. 6 , DB name) C22C 38/00-38/60 C21D 8/00
Claims (4)
05〜0.50％、Mn：10〜30％、Ｐ：0.009 ％以下、Ｓ：0.
003 ％以下、Ni：２〜15％、Cr：10〜25％、Mo：0.5 〜
7.0％、Al：0.01〜0.10％、Ｎ：0.15〜0.24％、Ca：0.
0005〜0.0050％を含有し、かつＸ＝Ni-30C+0.5Moで表さ
れるパラメータＸが5.50以上であり、残部Feおよび不可
避的不純物からなる化学成分でオーステナイト結晶粒度
番号が2.0 〜 5.0の範囲であることを特徴とする極低温
用Mn非磁性鋼。C. 0.03 to 0.10% by weight, Si: 0.
05 to 0.50%, Mn: 10 to 30%, P: 0.009% or less, S: 0.
003% or less, Ni: 2 to 15%, Cr: 10 to 25%, Mo: 0.5 to
7.0%, Al: 0.01-0.10%, N: 0.15-0.24%, Ca: 0.
0005-0.0050%, and the parameter X represented by X = Ni-30C + 0.5Mo is 5.50 or more, and the austenitic grain size number is a chemical component consisting of the balance Fe and unavoidable impurities, and the range of 2.0-5.0. Mn nonmagnetic steel for cryogenic use, characterized in that:
2.0％、Ｂ：0.0005〜0.0030％、Nb、Ｖ、Ti：総量で0.0
1〜 2.0％、を１種又は２種以上含有した請求項１記載
の極低温用高Mn非磁性鋼。2. The method according to claim 1, further comprising Cu: 0.01 to
2.0%, B: 0.0005 to 0.0030%, Nb, V, Ti: 0.0 in total amount
The high-Mn nonmagnetic steel for cryogenic use according to claim 1, which contains one or more of 1 to 2.0%.
つ破壊靱性値ＫICが200MPam 1/2以上である請求項１又
は２記載の極低温用高Mn非磁性鋼。3. The high-Mn nonmagnetic steel for cryogenic use according to claim 1, wherein a 0.2% proof stress at 4K is 1200 MPa or more and a fracture toughness value K IC is 200 MPam 1/2 or more.
〜1250℃に加熱後、900℃以上の仕上温度で熱間圧延又
は鍛造を終了し空冷あるいは強制冷却を行った後、 950
〜1150℃の範囲で加熱後空冷する溶体化処理を施すこと
を特徴とする極低温用高Mn非磁性鋼の製造方法。4. A steel slab of chemical composition according to claim 1 or 2
After heating to ~ 1250 ° C, finishing hot rolling or forging at a finishing temperature of 900 ° C or more and performing air cooling or forced cooling, 950
A method for producing a high-Mn nonmagnetic steel for cryogenic use, characterized by performing a solution treatment of heating at a temperature in the range of 1 to 150C and air cooling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7262982A JP2978427B2 (en) | 1995-05-22 | 1995-10-11 | High Mn nonmagnetic steel for cryogenic use and manufacturing method |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12265295 | 1995-05-22 | ||
| JP7-122652 | 1995-05-22 | ||
| JP7262982A JP2978427B2 (en) | 1995-05-22 | 1995-10-11 | High Mn nonmagnetic steel for cryogenic use and manufacturing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0941087A JPH0941087A (en) | 1997-02-10 |
| JP2978427B2 true JP2978427B2 (en) | 1999-11-15 |
Family
ID=26459746
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7262982A Expired - Lifetime JP2978427B2 (en) | 1995-05-22 | 1995-10-11 | High Mn nonmagnetic steel for cryogenic use and manufacturing method |
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| Country | Link |
|---|---|
| JP (1) | JP2978427B2 (en) |
Cited By (1)
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|---|---|---|---|---|
| CN102943220A (en) * | 2012-11-23 | 2013-02-27 | 四川金广技术开发有限公司 | Nickel-saving austenitic stainless steel and fabrication method thereof |
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|---|---|---|---|---|
| JP3864600B2 (en) * | 1999-01-27 | 2007-01-10 | Ｊｆｅスチール株式会社 | Method for producing high Mn non-magnetic steel sheet for cryogenic use |
| JP2003155542A (en) * | 2001-11-21 | 2003-05-30 | Japan Atom Energy Res Inst | HIGH NONMAGNETIC Mn STEEL FOR SUPERCONDUCTING MAGNET HAVING EXCELLENT HOT WORKABILITY AND HEATING EMBRITTLEMENT RESISTANCE AFTER HEAT TREATMENT FOR PRODUCING SUPERCONDUCTING MAGNET |
| JP5162954B2 (en) * | 2007-05-06 | 2013-03-13 | 大同特殊鋼株式会社 | High-strength nonmagnetic stainless steel, high-strength nonmagnetic stainless steel parts, and method for manufacturing the same |
| ATE546558T1 (en) * | 2008-07-30 | 2012-03-15 | Lepl Ferdinand Tavadze Inst Of Metallurg And Materials Science | AUSTENITIC ALLOY FOR LOW TEMPERATURE APPLICATIONS |
| KR101543916B1 (en) * | 2013-12-25 | 2015-08-11 | 주식회사 포스코 | Steels for low temperature services having superior deformed surface quality and method for production thereof |
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| KR102255827B1 (en) * | 2018-10-25 | 2021-05-26 | 주식회사 포스코 | Low-temperature austenitic high manganese steel having excellent surface quality and manufacturing method for the same |
| EP4039843A1 (en) | 2021-02-04 | 2022-08-10 | Richemont International S.A. | Non ferromagnetic alloy, manufacturing proccess therefore and clock movement component made of that alloy |
| CN113462991A (en) * | 2021-06-04 | 2021-10-01 | 中铁宝桥集团有限公司 | Forging or rolling process of alloyed high manganese steel frog |
| CN114959516B (en) * | 2022-05-25 | 2022-11-15 | 北京科技大学 | Stainless steel wire and preparation method thereof |
-
1995
- 1995-10-11 JP JP7262982A patent/JP2978427B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102943220A (en) * | 2012-11-23 | 2013-02-27 | 四川金广技术开发有限公司 | Nickel-saving austenitic stainless steel and fabrication method thereof |
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| Publication number | Publication date |
|---|---|
| JPH0941087A (en) | 1997-02-10 |
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