JP2595092B2 - Manufacturing method of high strength and high toughness steel - Google Patents
Manufacturing method of high strength and high toughness steelInfo
- Publication number
- JP2595092B2 JP2595092B2 JP1119266A JP11926689A JP2595092B2 JP 2595092 B2 JP2595092 B2 JP 2595092B2 JP 1119266 A JP1119266 A JP 1119266A JP 11926689 A JP11926689 A JP 11926689A JP 2595092 B2 JP2595092 B2 JP 2595092B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- toughness
- steel
- strength
- rolling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Landscapes
- Heat Treatment Of Steel (AREA)
Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は、溶接施工を受ける高強度高靭性鋼の製造方
法に関するものである。The present invention relates to a method for producing high-strength and high-toughness steel subjected to welding.
（従来の技術） 高強度で溶接性が良好な鋼板として、Cu析出強化型高
張力鋼が知られており、米国特許第3692514号またはAST
M A710にその例を見ることができる。(Prior Art) As a steel plate having high strength and good weldability, a Cu precipitation strengthened high strength steel is known, and US Pat. No. 3,692,514 or AST
You can see an example in M A710.
しかし、近年構造物の大型化と使用環境の苛酷化に伴
い使用鋼材に要求される特性も厳しくなってきた。However, in recent years, with the enlargement of the structure and the severer use environment, the characteristics required for the steel material used have become severer.
この要求に応えるべく、つぎのような技術が提案され
ている。In order to meet this demand, the following techniques have been proposed.
例えば、制御圧延、加速冷却、時効処理を組合わせた
製造方法（特開昭62−256915）、また、制御圧延と時効
処理を組合わせた製造方法（特開昭61−149430）などが
ある。For example, there is a production method combining controlled rolling, accelerated cooling, and aging treatment (Japanese Patent Application Laid-Open No. 62-256915), and a production method combining controlled rolling and aging treatment (Japanese Patent Application Publication No. 61-149430).
（発明が解決しようとする課題） しかし、上記の高張力鋼の製造方法は、何れも圧延条
件、冷却条件および熱処理条件を制御するものであり、
厚鋼板での高強度化および低温での高靭性化には対応が
困難である。(Problems to be Solved by the Invention) However, all of the above methods for producing high-tensile steel control rolling conditions, cooling conditions, and heat treatment conditions.
It is difficult to deal with high strength of steel plates and high toughness at low temperatures.
本発明は、低炭素当量の成分系でCuの析出硬化を利用
し、さらに、MoとＮの複合添加と制御圧延により低温靭
性の向上を図り、降伏強度が55kgf/mm2以上、−80℃で
のシャルピ吸収エネルギが10kgf・ｍ以上の値を有する
高強度高靭性の鋼を得る方法を提供することを目的とす
るものである。The present invention utilizes the precipitation hardening of Cu in a low carbon equivalent component system, further improves the low-temperature toughness by the combined addition of Mo and N and controlled rolling, and has a yield strength of 55 kgf / mm 2 or more, at -80 ° C. It is an object of the present invention to provide a method for obtaining a high-strength and high-toughness steel having a Charpy absorbed energy of 10 kgf · m or more.
（課題を解決するための手段） 本発明は、上記に説明した高強度高靭性鋼の製造方法
の問題点に鑑み、本発明者らが化学成分、特にMoとＮ量
を適切に調整し、さらに、圧延工程において圧下条件お
よび圧延後の冷却条件を適切に制御することによって高
強度高靭性鋼の製造が可能であるという知見を得て完成
されたもので、その要旨は、C:0.01〜0.10％、Si:0.10
〜0.50％、Mn:0.8〜2.0％、Al:0.01〜0.10％、Cu:0.8〜
1.8％、Ni:0.4〜4.0％、Mo:0.1〜1.0％、Nb:0.01〜0.06
％、N:0.006％超え0.015％以下を含み、残部Feおよび不
可避不純物から成る鋼片を加熱圧延するに際し、900℃
以下の温度で40％以上の圧下を加え、700℃以上の温度
で圧延を完了し、その後直ちに２℃/sec以上の冷却速度
で550℃以下の温度まで強制冷却を行い、さらに、500〜
680℃の温度範囲で焼戻し処理を行うものである。(Means for Solving the Problems) The present invention has been made in view of the above-described problems of the method for producing a high-strength and high-toughness steel, and has appropriately adjusted the chemical components, in particular, the amounts of Mo and N. Furthermore, it was completed with the knowledge that the production of high-strength and high-toughness steel is possible by appropriately controlling the rolling conditions and the cooling conditions after rolling in the rolling process, and the gist is C: 0.01 to 0.10%, Si: 0.10
~ 0.50%, Mn: 0.8 ~ 2.0%, Al: 0.01 ~ 0.10%, Cu: 0.8 ~
1.8%, Ni: 0.4-4.0%, Mo: 0.1-1.0%, Nb: 0.01-0.06
%, N: more than 0.006% and 0.015% or less, 900 ° C when hot-rolling a slab consisting of the balance of Fe and unavoidable impurities
Rolling is completed at a temperature of 700 ° C or more by applying a reduction of 40% or more at the following temperature. Immediately thereafter, forced cooling is performed to a temperature of 550 ° C or less at a cooling rate of 2 ° C / sec or more.
The tempering treatment is performed in a temperature range of 680 ° C.
（作用） 以下、本発明の作用について発明者らの実験結果等に
基づいて詳述して行くことにする。(Operation) Hereinafter, the operation of the present invention will be described in detail based on experimental results of the inventors.
先ずは、低温靭性に及ぼすMoとＮ量との関係について
説明する。本発明者らは低温靭性に及ぼすMoとＮ量との
関係を明らかにするために、以下のような試験を行っ
た。First, the relationship between Mo and N content on low-temperature toughness will be described. The present inventors conducted the following test in order to clarify the relationship between Mo and N content on the low-temperature toughness.
試験には、0.04％Ｃ−0.3％Si−1.4％Mn−1.2％Cu−
0.7％Ni−0.04％Nb−0.03％Alを基本成分とし、Moおよ
びＮ量を変化させた鋼片を用い、これを1000℃に加熱し
た後、780℃の温度で圧延を終了し、直ちに直接焼入れ
を行い、その後600℃で焼戻し処理を行った。In the test, 0.04% C-0.3% Si-1.4% Mn-1.2% Cu-
A steel slab containing 0.7% Ni-0.04% Nb-0.03% Al as a basic component and varying amounts of Mo and N was heated to 1000 ° C, and then finished rolling at a temperature of 780 ° C. After quenching, tempering treatment was performed at 600 ° C.
第１図は、これらの鋼板から得られた−80℃における
シャルピ吸収エネルギとMoおよびＮ量との関係を示した
ものである。FIG. 1 shows the relationship between the Charpy absorbed energy at −80 ° C. and the amounts of Mo and N obtained from these steel sheets.
同図の●印はMo添加を、○印はMo無添加をそれぞれ示
している。In the figure, the symbol ● indicates Mo addition, and the symbol ○ indicates no Mo addition.
第１図から明らかなように、Mo添加した鋼板はＮ量が
60ppm超えにおいて靭性が著しく向上している。一方、M
oを添加していない鋼板はＮ量の影響は認められない。As is clear from FIG. 1, the N content of the steel sheet added with Mo is
At over 60 ppm, the toughness is significantly improved. On the other hand, M
The effect of N content is not recognized in the steel sheet to which o is not added.
従って、MoとＮとの複合添加によって低温靭性を向上
させる元素であることが明らかである。Therefore, it is clear that the element is an element that improves the low-temperature toughness by the combined addition of Mo and N.
つぎに、本発明に規定される鋼中成分について説明す
る。Next, components in steel specified in the present invention will be described.
Ｃは、強度上昇に有効な元素であり、そのためには0.
01％以上が必要である。しかし、靭性の確保および耐溶
接割れ性の低下防止の観点から上限を0.10％に制限する
必要がある。従って、Ｃ量は0.01〜0.10％の範囲とす
る。C is an element effective for increasing the strength, and for that purpose, C is 0.
01% or more is required. However, it is necessary to limit the upper limit to 0.10% from the viewpoint of securing toughness and preventing a decrease in weld cracking resistance. Therefore, the C content is in the range of 0.01 to 0.10%.
Siは、脱酸元素であり、0.10％以上の添加が必要であ
るが、過度の添加は靭性を劣化させるため上限を0.50％
とする。このため、Si量は0.10〜0.50％の範囲とする。Si is a deoxidizing element and must be added in an amount of 0.10% or more. However, excessive addition deteriorates toughness, so the upper limit is 0.50%.
And For this reason, the Si content is in the range of 0.10 to 0.50%.
Mnは、強度上昇に有効であり、そのためには0.8％以
上が必要であるが、2.0％を超えて添加すると靭性が劣
化する。従って、Mn量は0.8〜2.0％の範囲とする。Mn is effective for increasing the strength, and for that purpose 0.8% or more is required. However, if it exceeds 2.0%, toughness is deteriorated. Therefore, the Mn content is in the range of 0.8 to 2.0%.
Alは、脱酸元素であり、0.01％以上の添加が必要であ
るが、過度の添加は介在物を形成し、靭性を劣化させる
ために上限を0.10％とする。このため、Al量は0.01〜0.
10％の範囲とする。Al is a deoxidizing element and needs to be added in an amount of 0.01% or more, but an excessive addition forms inclusions and degrades toughness, so the upper limit is 0.10%. For this reason, the Al content is 0.01-0.
The range is 10%.
Cuは、固液強化、析出強化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0.8％以上の添加が必要
である。しかし、過度の添加は靭性を低下させるため、
上限を1.8％とする。従って、Cu量は0.8〜1.8％の範囲
とする。Cu is an element effective for solid-liquid strengthening and precipitation strengthening. In order to exert these effects, it is necessary to add 0.8% or more. However, excessive addition reduces toughness,
The upper limit is 1.8%. Therefore, the Cu content is in the range of 0.8 to 1.8%.
Niは、低温靭性を改善する効果があり、このためには
0.4％以上の添加が必要である。しかし、経済性の観点
から上限を4.0％とする。従って、Ni量は0.4〜4.0％の
範囲とする。Ni has the effect of improving low-temperature toughness.
It is necessary to add 0.4% or more. However, the upper limit is set at 4.0% from the viewpoint of economy. Therefore, the Ni content is in the range of 0.4 to 4.0%.
Moは、上記のように本発明の特徴成分の一つであり、
後述するＮ量の調整とあいまって、鋼の低温靭性を著し
く改善する効果がある。このためには、0.1％以上の添
加が必要であるが過度の添加は溶接性を劣化させるた
め、上限を1.0％とする。従って、Mo量は0.1〜1.0％の
範囲とする。Mo is one of the characteristic components of the present invention as described above,
The effect of remarkably improving the low-temperature toughness of the steel, in combination with the adjustment of the N amount described below, is obtained. For this purpose, it is necessary to add 0.1% or more, but excessive addition deteriorates the weldability, so the upper limit is made 1.0%. Therefore, the amount of Mo is set in the range of 0.1 to 1.0%.
Nbは、圧延中オーステナイトの再結晶を抑制し細粒化
に有効な元素であり、そのためには、0.01％以上の添加
が必要である。しかし、0.06％を超えると溶接部の靭性
を損なう。このため、Nb量は0.01〜0.06％の範囲とす
る。Nb is an element that suppresses austenite recrystallization during rolling and is effective for grain refinement. For this purpose, 0.01% or more of Nb is required. However, if it exceeds 0.06%, the toughness of the weld is impaired. For this reason, the Nb content is in the range of 0.01 to 0.06%.
Ｎは、Moと同じく本発明の特徴成分の一つであり、Mo
の添加とあいまって、鋼の低温靭性の改善に効果があ
り、このためには、0.006％超えの添加が必要である。
しかしながら、過度の添加は溶接部の靭性を劣化させる
ため、上限を0.015％に抑える必要がある。従って、Ｎ
量は0.006％超え0.015％以下の範囲とする。N is one of the characteristic components of the present invention like Mo,
Is effective in improving the low-temperature toughness of steel in combination with the addition of 0.006% or more.
However, excessive addition degrades the toughness of the weld, so the upper limit must be suppressed to 0.015%. Therefore, N
The amount should be between 0.006% and 0.015%.
Caは、靭性の向上に有効な元素であるが、過度に添加
すると靭性を損なうので、添加する場合は添加量を0.00
50％以下に制限する。Ca is an element effective for improving toughness, but if added excessively, it impairs toughness.
Limit to 50% or less.
つぎに、圧延条件の限定理由について述べる。 Next, the reasons for limiting the rolling conditions will be described.
圧延工程において、高靭性を得るにはオーステナイト
粒への加工歪みの付与が必須条件であり、このためには
オーステナイト低温域の圧延が有効であり、900℃を超
える温度ではこの効果が小さい。このため、900℃以下
の温度で40％以上の圧下を加える。In the rolling step, in order to obtain high toughness, it is essential to impart processing strain to austenite grains. For this purpose, rolling in a low-temperature austenite region is effective, and this effect is small at temperatures exceeding 900 ° C. For this purpose, a reduction of 40% or more is applied at a temperature of 900 ° C or less.
圧延完了温度については、圧延後の強制冷却により強
度の上昇を図るため、圧延完了温度は700℃以上に限定
する。The rolling completion temperature is limited to 700 ° C. or higher in order to increase the strength by forced cooling after the rolling.
圧延後の冷却速度については、十分な強度が得られる
条件として、２℃/sec以上の冷却速度で550℃以下の温
度まで強制冷却する必要がある。Regarding the cooling rate after rolling, it is necessary to forcibly cool to a temperature of 550 ° C. or less at a cooling rate of 2 ° C./sec or more as a condition for obtaining sufficient strength.
さらに、Cuの析出強化を発揮させるため、500〜680℃
の温度範囲で焼戻し処理を行う必要がある。500℃未満
ではCuの析出に長時間を要し、一方、680℃を超える温
度ではCuの析出物が粗大化し十分な析出強化が得られな
い。このため、焼戻し処理温度は500〜680℃の温度範囲
とする。Furthermore, in order to demonstrate the precipitation strengthening of Cu, 500-680 ° C
It is necessary to perform a tempering treatment in the temperature range described above. If the temperature is lower than 500 ° C., a long time is required for the precipitation of Cu. On the other hand, if the temperature is higher than 680 ° C., the precipitate of Cu becomes coarse and sufficient precipitation strengthening cannot be obtained. For this reason, the tempering temperature is set to a temperature range of 500 to 680 ° C.
（実施例） 本発明の構成は上記の通りであるが、以下に実施例に
ついて説明する。(Example) The configuration of the present invention is as described above, and an example will be described below.
供試鋼板は第１表に示す化学成分を有する鋼を常法に
より溶製、鋳造し、得られた鋼片を第２表に示す圧延条
件および冷却条件にしたがい、圧延、冷却し、その後60
0℃の温度で焼戻し処理を行ったものである。これの鋼
板から試験片を採取し、引張試験および2mmVノッチシャ
ルピ衝撃試験を行った。その結果を第２表に併記する。The test steel sheet was prepared by melting and casting a steel having the chemical composition shown in Table 1 by a conventional method, rolling the obtained steel slab in accordance with the rolling conditions and cooling conditions shown in Table 2, and then cooling and cooling.
The tempering treatment was performed at a temperature of 0 ° C. A test piece was taken from the steel plate and subjected to a tensile test and a 2 mmV notch Charpy impact test. The results are shown in Table 2.
第１表には本発明法および比較法の化学成分を、第２
表には圧延条件、冷却条件および機械的性質をそれぞれ
示す。Table 1 shows the chemical components of the method of the present invention and the comparative method.
The table shows rolling conditions, cooling conditions, and mechanical properties.
第２表の本発明法によるNo.1、６、９〜11は何れも、
降伏強度は60kgf/mm2以上を、引張強さは60〜80kgf/mm2
級の値を示し、また、−80℃でのシャルピ吸収エネルギ
は13kgf・ｍ以上の極めて良い値を示している。 Nos. 1, 6, 9 to 11 according to the method of the present invention in Table 2 are all
The yield strength is 60kgf / mm 2 or more, the tensile strength is 60~80kgf / mm 2
And the Charpy absorbed energy at -80 ° C is an extremely good value of 13 kgf · m or more.
これに対して、比較法No.2は900℃以下の圧下率不足
のためシャピル吸収エネルギは4.8kgf・ｍと低い値であ
る。On the other hand, in Comparative Method No. 2, the Sharpil absorbed energy is a low value of 4.8 kgf · m due to insufficient rolling reduction below 900 ° C.
比較法No.3は圧延完了温度が650℃と低く、その後の
強制冷却効果が十分に得られなかったため、降伏強度、
引張強さとも低い値を示している。In Comparative Method No. 3, the rolling completion temperature was as low as 650 ° C., and the subsequent forced cooling effect was not sufficiently obtained.
The tensile strength also shows a low value.
比較法No.4は冷却速度が小さく、十分な冷却効果が得
られなかったため、降伏強度、引張強さとも低い値を示
している。In Comparative Method No. 4, since the cooling rate was low and a sufficient cooling effect was not obtained, both the yield strength and the tensile strength showed low values.
比較法No.5は冷却停止温度が600℃と高く冷却効果不
足のため、降伏強度、引張強さとも低い値を示してい
る。In Comparative Method No. 5, the yield strength and tensile strength are low because the cooling stop temperature is as high as 600 ° C. and the cooling effect is insufficient.
比較法No.7はＮが、比較法No.8はMoが本発明の範囲外
のため、圧延条件、冷却条件とも本発明の範囲内にある
にも拘らず、−80℃でのシャルピ吸収エネルギは9.2、
6.3kgf・ｍと低い値を示している。In Comparative Method No. 7, N was used, and in Comparative Method No. 8, Mo was out of the scope of the present invention. Thus, Charpy absorption at −80 ° C. despite the rolling conditions and cooling conditions being within the scope of the present invention. Energy is 9.2,
It shows a low value of 6.3 kgf · m.
以上の実施例の結果からも明らかなように、本発明に
係わる高強度高靭性鋼の製造方法は、低温靭性に優れた
高張力鋼の製造に最も相応しいものである。As is clear from the results of the above examples, the method for producing a high-strength and high-toughness steel according to the present invention is most suitable for producing a high-tensile steel having excellent low-temperature toughness.
なお、上記実施例は厚鋼板の製造方法についてのもの
であるが、本発明は他の鋼製品、例えば条鋼、形鋼の製
造にも適応し得ることは言うまでもない。Although the above embodiment is directed to a method of manufacturing a thick steel plate, it goes without saying that the present invention can be applied to the manufacture of other steel products, for example, a bar and a section steel.
（発明の効果） 以上説明したように、本発明に係わる高強度高靭性鋼
の製造方法は、上記の構成であるから、強度が高くかつ
低温靭性の優れた鋼を製造することができるという優れ
た効果を有するものである。(Effects of the Invention) As described above, the method for producing a high-strength and high-toughness steel according to the present invention has the above-described configuration, and thus is excellent in that a steel having high strength and excellent low-temperature toughness can be produced. This has the effect.
第１図はMoおよびＮ量の低温靭性VE-80（−80℃でのシ
ャルピ吸収エネルギ値）に及ぼす影響を示すグラフであ
る。FIG. 1 is a graph showing the effect of the amounts of Mo and N on the low-temperature toughness V E -80 (Charpy absorbed energy value at -80 ° C.).
Claims (1)
8〜2.0％、Al:0.01〜0.10％、Cu:0.8〜1.8％、Ni:0.4〜
4.0％、Mo:0.1〜1.0％、Nb:0.01〜0.06％、N:0.006％超
え0.015％以下を含み、残部Feおよび不可避不純物から
成る鋼片を加熱圧延するに際し、900℃以下の温度で40
％以上の圧下を加え700℃以上の温度で圧延を完了し、
その後直ちに２℃/sec以上の冷却速度で550℃以下の温
度まで強制冷却を行い、さらに、500〜680℃の温度範囲
で焼戻し処理を行うことを特徴とする高強度高靭性鋼の
製造方法。(1) C: 0.01 to 0.10%, Si: 0.10 to 0.50%, Mn: 0.
8 to 2.0%, Al: 0.01 to 0.10%, Cu: 0.8 to 1.8%, Ni: 0.4 to
4.0%, Mo: 0.1-1.0%, Nb: 0.01-0.06%, N: More than 0.006% and 0.015% or less.
Rolling is completed at a temperature of 700 ° C or more by applying a reduction of at least
A method for producing a high-strength, high-toughness steel, comprising: immediately forcibly cooling to a temperature of 550 ° C. or less at a cooling rate of 2 ° C./sec or more, and further performing a tempering treatment in a temperature range of 500 to 680 ° C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1119266A JP2595092B2 (en) | 1989-05-12 | 1989-05-12 | Manufacturing method of high strength and high toughness steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1119266A JP2595092B2 (en) | 1989-05-12 | 1989-05-12 | Manufacturing method of high strength and high toughness steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02298216A JPH02298216A (en) | 1990-12-10 |
| JP2595092B2 true JP2595092B2 (en) | 1997-03-26 |
Family
ID=14757089
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1119266A Expired - Lifetime JP2595092B2 (en) | 1989-05-12 | 1989-05-12 | Manufacturing method of high strength and high toughness steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2595092B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7195191B2 (en) | 2002-12-30 | 2007-03-27 | Samsung Electronics Co., Ltd. | Oil spattering prevention apparatus for tape recorder |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58171526A (en) * | 1982-03-31 | 1983-10-08 | Nippon Steel Corp | Manufacture of steel for extra-low temperature use |
| JPH0615689B2 (en) * | 1987-05-19 | 1994-03-02 | 新日本製鐵株式会社 | Method of manufacturing low yield ratio high strength steel |
-
1989
- 1989-05-12 JP JP1119266A patent/JP2595092B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7195191B2 (en) | 2002-12-30 | 2007-03-27 | Samsung Electronics Co., Ltd. | Oil spattering prevention apparatus for tape recorder |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02298216A (en) | 1990-12-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3045856B2 (en) | Method for producing high toughness Cu-containing high tensile steel | |
| JP4096839B2 (en) | Manufacturing method of high yield thick steel plate with low yield ratio and excellent toughness of heat affected zone | |
| JPH0748621A (en) | Production of steel for pressure vessel excellent in ssc resistance and hic resistance | |
| JP3602471B2 (en) | High tensile strength steel sheet excellent in weldability and method for producing the same | |
| JPH06128631A (en) | Production of high manganese ultrahigh tensile strength steel excellent in low temperature toughness | |
| JPH0781164B2 (en) | Method for manufacturing high-strength and high-toughness steel sheet | |
| JP2595092B2 (en) | Manufacturing method of high strength and high toughness steel | |
| JPH0693332A (en) | Production of high tensile strength and high toughness fine bainitic steel | |
| JP2692523B2 (en) | Method for producing 780 MPa class high strength steel with excellent weldability and low temperature toughness | |
| JP2706159B2 (en) | Method for producing low yield ratio high strength steel with good weldability | |
| JP3229107B2 (en) | Manufacturing method of low yield ratio high strength steel sheet with excellent uniform elongation | |
| JP2898455B2 (en) | Manufacturing method of high strength steel with excellent weldability | |
| JPH04276018A (en) | Manufacture of door guard bar excellent in collapse resistant property | |
| JPS583012B2 (en) | Manufacturing method of high toughness high tensile strength steel plate | |
| JP2671732B2 (en) | Manufacturing method of high strength steel with excellent weldability | |
| JP2706133B2 (en) | Method for producing low yield ratio, high toughness, high strength steel sheet | |
| JP3298718B2 (en) | Manufacturing method of ultra-thick tempered high strength steel sheet | |
| JP2500948B2 (en) | Manufacturing method of thick 80kgf / mm2 grade high strength steel with excellent weldability | |
| JP3739997B2 (en) | High-tensile steel plate with excellent weldability | |
| JP2743765B2 (en) | Cr-Mo steel plate for pressure vessel and method for producing the same | |
| JP2546888B2 (en) | Manufacturing method of high-strength steel sheet with excellent weldability and toughness | |
| JP3828480B2 (en) | High toughness and high strength non-tempered steel sheet and its production | |
| JP2529042B2 (en) | Manufacturing method of low yield ratio steel pipe for building by cold forming. | |
| JP2710846B2 (en) | Method for producing Cu precipitation-strengthened extra-thick high-strength steel sheet excellent in low-temperature toughness | |
| JPH05331539A (en) | Manufacture of low yield ratio high strength and high roughness steel excellent in weldability |