JPH0499817A - Production of high-tensile steel having low-yield ratio - Google Patents
Production of high-tensile steel having low-yield ratioInfo
- Publication number
- JPH0499817A JPH0499817A JP21578490A JP21578490A JPH0499817A JP H0499817 A JPH0499817 A JP H0499817A JP 21578490 A JP21578490 A JP 21578490A JP 21578490 A JP21578490 A JP 21578490A JP H0499817 A JPH0499817 A JP H0499817A
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- steel
- yield ratio
- point
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 36
- 239000010959 steel Substances 0.000 title claims abstract description 36
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 238000001816 cooling Methods 0.000 claims abstract description 25
- 238000010438 heat treatment Methods 0.000 claims abstract description 15
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052802 copper Inorganic materials 0.000 claims abstract description 5
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 5
- 238000005096 rolling process Methods 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 4
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 3
- 238000005496 tempering Methods 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 abstract description 2
- 229910052759 nickel Inorganic materials 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000000034 method Methods 0.000 description 7
- 229910000859 α-Fe Inorganic materials 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910000744 A-2 tool steel Inorganic materials 0.000 description 1
- 229910001193 A-6 tool steel Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【発明の詳細な説明】
〈産業上の利用分野〉
本発明は建築、橋梁、タンクなどの鉄鋼構造物に利用さ
れる降伏比が８０％以下で引張強さが７０ｋｇｆ／−以
上の低降伏比高張力鋼の製造方法に関するものである。[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to steel structures such as buildings, bridges, and tanks, with a yield ratio of 80% or less and a tensile strength of 70 kgf/- or more. The present invention relates to a method for manufacturing high-strength steel.
〈従来の技術〉
建築、橋梁、タンクなどの鉄鋼構造物の大型化にともな
い使用される鋼材には高強度化が求められている一方で
構造物の安全性、即ち脆性破壊防止の観点からは降伏比
の低いことが求められている。しかしながら、降伏比は
高強度化とともに上昇する傾向にあり、引張強さが７０
ｋｇｆ／−以上の高張力鋼では８０％以下の低降伏比を
得ることは容易ではない。<Conventional technology> As steel structures such as buildings, bridges, and tanks become larger, the steel materials used are required to have higher strength.However, from the viewpoint of structural safety, that is, prevention of brittle fracture, A low yield ratio is required. However, the yield ratio tends to increase with increasing strength, and the tensile strength is 70
It is not easy to obtain a low yield ratio of 80% or less with high tensile strength steel of kgf/- or more.
従来の低降伏比高張力鋼の製造方法としては、例えば特
開昭５５−９７４２５号公報に開示された方法がある。As a conventional method for manufacturing low yield ratio high tensile strength steel, for example, there is a method disclosed in JP-A-55-97425.
これは単にフェライトとオーステナイトの２相域温度に
再加熱してから焼入れるものである。This is simply reheating to a temperature in the two-phase region of ferrite and austenite and then quenching.
この方法は厚物（板厚３０ｍｍ以上）の６０キロ鋼の低
降伏比化には有効であるが、焼入性の良好な薄物材（板
厚２５ｍｍ以下）あるいは、合金元素含有量の多い７０
〜８０キロ鋼の低降伏比化に対しては有効でない。例え
ば鉄鋼協会講演大会ＣＡＭＰ−Ｉ Ｓ ＩＪ Ｖｏｌ、
１ （１９８８） −８１３（５４０）で示される
ように、ＨＴ−８０鋼では８３％の降伏比（ＹＲ）Ｌ、
か得られていない。このように従来法では引張強さが７
０ｋｇｆ／−以上の高張力鋼で８０％以下の低降伏比が
得られなかった。This method is effective for lowering the yield ratio of thick 60kg steel (plate thickness 30mm or more), but it is also effective for reducing the yield ratio of 60kg steel with good hardenability (plate thickness 25mm or less) or 70kg steel with a high alloying element content.
It is not effective for lowering the yield ratio of ~80 kg steel. For example, the Iron and Steel Institute Lecture Conference CAMP-IS IJ Vol.
1 (1988) -813 (540), the yield ratio (YR) L of 83% for HT-80 steel,
or not obtained. In this way, the conventional method has a tensile strength of 7
A low yield ratio of 80% or less could not be obtained with high tensile strength steel of 0 kgf/- or more.
〈発明が解決しようとする課題〉
本発明はこのような現状に鑑みてなされたもので、その
目的とするところは引張強さが７０ｋｇｆ／ｍ１１以上
でかつ８０％以下の低降伏比を有する高張力鋼の製造方
法を擢案することである。<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned current situation, and its purpose is to develop a high-density steel with a tensile strength of 70 kgf/m11 or more and a low yield ratio of 80% or less. The purpose is to develop a method for producing tension steel.
〈課題を解決するための手段〉
本発明者らは、高張力鋼でかつ低降伏比の得られる成分
系および熱処理法について研究を重ねた結果、不純物と
して存在するＴｉおよびＮｂ含有量ならびにα＋γの２
相域温度までの加熱速度が、降伏比に大きく影響するこ
とを見出し、本発明を構成するに至った。<Means for Solving the Problems> As a result of repeated research on the composition system and heat treatment method for high-strength steel with a low yield ratio, the present inventors have determined that the content of Ti and Nb existing as impurities and the α+γ 2
It was discovered that the heating rate up to the phase region temperature greatly affects the yield ratio, and the present invention was constructed based on this discovery.
すなわち本発明は、重量比にて、Ｃ： ｏ、ｏｓ〜０．
２５％、Ｓｉ ： ０．０５〜１．００％、Ｍｎ ：
０．５０〜１．８０％、Ｐ ； ０．０４０％以下、Ｓ
Ｆ ０．０２０％以下、Ｎ ： ０．００６０％以下
、／Ｖ ： ０．０２０−０．０８０％、Ｂ ： ０
．０００３〜０．００３０％を含み、さらにＮｉ ：
１．５０％以下、ｃｒ：０．８０％以下、Ｍｏ ： ０
．２０〜０．８０％およびＣｕ ： ０．５０％以下の
うち１種以上を含み、かつ不純物としてのＴｉ及びＮｂ
をそれぞれ０．００５％以下に制限し、残部実質的にＦ
ｅからなる鋼を圧延終了後冷却したのち、Ａｃｓ点以上
の温度に加熱後、空冷以上の冷却速度で冷却したのち、
再度（Ａｃ＋点＋４０℃）〜（Ａｃ８点−３０℃）の（
α＋γ）２相域温度まで、少なくとも７００℃以上は１
０℃／ｗｉｎ以下の昇温速度で加熱した後、空冷以上の
冷却速度で冷却し、その後Ａｃ１点以下の温度で焼もど
しを行うことを特徴とする低降伏比高張力鋼の製造方法
である。That is, the present invention has a weight ratio of C: o, os to 0.
25%, Si: 0.05-1.00%, Mn:
0.50-1.80%, P; 0.040% or less, S
F: 0.020% or less, N: 0.0060% or less, /V: 0.020-0.080%, B: 0
．． 0003 to 0.0030%, and further contains Ni:
1.50% or less, cr: 0.80% or less, Mo: 0
．． 20 to 0.80% and Cu: Contains one or more of 0.50% or less, and contains Ti and Nb as impurities.
are limited to 0.005% or less, and the remainder is substantially F.
After the steel consisting of e is cooled after rolling, heated to a temperature above the Acs point, and cooled at a cooling rate higher than air cooling,
Again (Ac+ point +40℃) to (Ac8 point -30℃) (
α + γ) Up to the two-phase region temperature, at least 700℃ or higher is 1
A method for producing a low yield ratio high tensile strength steel, which is characterized by heating at a temperature increase rate of 0°C/win or less, cooling at a cooling rate of air cooling or higher, and then tempering at a temperature of Ac1 point or less. .
〈作 用〉 まず本発明の組成構成について説明する。<For production> First, the composition of the present invention will be explained.
Ｃ： ０．０５〜０．２５％
Ｃは高強度を得るために０．０５％以上は必要であるが
、０．２５％を超えると溶接性、靭性を劣化させる。C: 0.05-0.25% C is required to be at least 0.05% in order to obtain high strength, but if it exceeds 0.25%, weldability and toughness deteriorate.
Ｓｉ ： ０．０５〜１．００％
Ｓｉは脱酸剤として０．０５％以上必要であるが、１．
００％超では延靭性、溶接性を低下させる。Si: 0.05-1.00% Si is required as a deoxidizing agent in an amount of 0.05% or more, but 1.
If it exceeds 0.00%, ductility and weldability are reduced.
Ｍｎ ： ０．５０〜１．８０％
Ｍｎは焼入性確保および強度確保のために０．５０％以
上必要であるが、１．８０％超の過剰添加は溶接性を低
下させる。Mn: 0.50 to 1.80% Mn is required to be 0.50% or more to ensure hardenability and strength, but excessive addition of more than 1.80% reduces weldability.
Ｐ ： ０．０４０％以下、Ｓ ： ０．０２０以
下Ｐ、Ｓは共に延靭性を低下させるので、それぞれ０．
０４０％以下、０．０２０％以下に限定する。P: 0.040% or less, S: 0.020% or less Since both P and S reduce ductility, they should each be set at 0.040% or less.
It is limited to 0.040% or less and 0.020% or less.
Ｎ ： ０．００６０％以下
ＮはＢと窒化物を形成し、焼入性に有効な固溶Ｂを減少
させるため、上限を０．００６０％とする。N: 0.0060% or less N forms a nitride with B and reduces solid solution B, which is effective for hardenability, so the upper limit is set to 0.0060%.
Ｂ ： ０．０００３〜０．００３０％焼入性向上のた
めに０．０００３％以上添加するが、０、００３０％を
超えるとその効果は飽和し、かつ靭性を低下させるので
、上限を０．００３０％とする。B: 0.0003-0.0030% 0.0003% or more is added to improve hardenability, but if it exceeds 0.0030%, the effect is saturated and the toughness is reduced, so the upper limit is set to 0.0030%. 0030%.
Ａ１０．０２０〜０．０８０％
Ｎを固定し焼入性に有効な固溶Ｂ確保のため、Ｍは０．
０２０％以上必要であるが、過剰の添加は靭性を劣化さ
せるので上限を０．０８０％とする。A10.020~0.080% In order to fix N and secure solid solution B that is effective for hardenability, M is 0.020% to 0.080%.
0.020% or more is required, but since excessive addition deteriorates toughness, the upper limit is set to 0.080%.
以上の成分に加えて、目的の強度に応じて下記のＮｉ、
Ｍｏ、 ＣｒおよびＣｕの１種以上を添加する。In addition to the above ingredients, depending on the desired strength, the following Ni,
One or more of Mo, Cr and Cu are added.
［： １．５０％以下
焼入性向上、靭性向上に有効な元素であるが、経済性の
点から上限を１．５０％とする。[: 1.50% or less Although it is an effective element for improving hardenability and toughness, the upper limit is set to 1.50% from the economic point of view.
Ｍｏ ： ０．２０〜０．８０％
Ｍｏは焼入性を高めるとともに、焼もどし軟化抵抗を高
め、強度上昇に有効である。高強度確保のために０．２
０％以上必要であるが、過剰添加は炭化物の析出強化に
より降伏比の上昇を来すと共に溶接性、靭性を低下させ
るので、上限を０．８０％とする。Mo: 0.20-0.80% Mo improves hardenability, increases resistance to temper softening, and is effective in increasing strength. 0.2 to ensure high strength
0% or more is necessary, but excessive addition increases the yield ratio due to precipitation strengthening of carbides and reduces weldability and toughness, so the upper limit is set to 0.80%.
Ｃｒ ： ０．８０％以下、Ｃｕ ： ０．５０％以下
いずれも強度上昇に有効な元素であるが、過剰な添加は
溶接性を低下させるので、それぞれの上限を０．８０％
、０４５０％とする。Cr: 0.80% or less, Cu: 0.50% or less. Both are effective elements for increasing strength, but excessive addition reduces weldability, so the upper limit of each is set at 0.80%.
, 0450%.
Ｔｉ： ｏ、ｏｏ５％以下、Ｎｂ： ０．００５％
以下いずれも安定な炭化物を形成し、２相域温度への加
熱時にオーステナイトの析出サイトとなり、結果的にオ
ーステナイＩ・がフェライト地に微細に析出し、２相域
焼入れ後でも微細なフェライトと硬化相の混合組織とな
り降伏比を高めるため、不純物としての存在をそれぞれ
０．００５％以下に制限する。Ti: o, oo 5% or less, Nb: 0.005%
All of the following form stable carbides and become austenite precipitation sites when heated to a two-phase region temperature, resulting in fine precipitation of austenite I on the ferrite base, and even after two-phase region quenching, fine ferrite and hardening occur. In order to form a mixed phase structure and increase the yield ratio, the presence of each impurity is limited to 0.005% or less.
以上の成分系からなる鋼を通常の造塊または連鋳法によ
り造塊した後、熱間圧延により所定の板厚まで圧延し冷
却する。圧延後の冷却は急冷でも徐冷でも良い。After the steel having the above-mentioned component system is formed into an ingot by a normal ingot-forming or continuous casting method, it is hot-rolled to a predetermined thickness and cooled. Cooling after rolling may be rapid cooling or slow cooling.
本発明の熱処理は、まずＡｃ３点以上の温度に加熱保持
後、空冷以上の冷却速度で冷却する。この熱処理は圧延
歪および組織不均一を除き、前組織を調整することによ
って最終的に得られる機械的性質のバラツキを小さくす
るために必要である。In the heat treatment of the present invention, first, the material is heated and maintained at a temperature equal to or higher than the Ac3 point, and then cooled at a cooling rate equal to or higher than air cooling. This heat treatment is necessary to remove rolling strain and nonuniform structure, and to reduce variations in the mechanical properties finally obtained by adjusting the previous structure.
次に（へ０１点＋４０℃）〜（八Ｃ３３０℃）の２相域
温度まで加熱するが、その際少なくとも７００℃から２
相域温度までの加熱速度を１０°ｃ／１１Ｔ１以下の昇
温速度で加熱し、前記２相域温度で保持した後冷却し、
焼もどしをすることにより低降伏比と高強度を得ようと
するものである。特に７００℃以上の温度域での加熱速
度をＩＯ℃／細以下に制御することが低降伏比を得るた
めに重要である。Next, it is heated to a two-phase region temperature of (01 point + 40℃) to (8C330℃), at least 700℃ to 2
Heating at a heating rate of 10 ° C / 11T1 or less to the phase region temperature, cooling after maintaining at the two-phase region temperature,
The aim is to obtain a low yield ratio and high strength by tempering. In particular, it is important to control the heating rate in the temperature range of 700° C. or higher to less than IO° C./fine in order to obtain a low yield ratio.
まず（Ａｃ＋点−ト４０℃） 〜（Ａｃｉ ３０℃）
の２相域温度に保持する理由について述べる。この温度
が高いほどオーステナイト（硬化相）の割合が増加し、
フェライトの割合が減少すると共に、オーステナイト中
のＣ濃度が低下する。降伏比および強度はフェライトと
硬化相の割合、各相の特性、分布に依存し、低降伏比か
つ高強度を得るには（へｃ、点＋４０℃） 〜（Ａｃｓ
３０℃）の２相域温度で保持する必要がある。First (Ac+ point - 40℃) ~ (Aci 30℃)
The reason for maintaining the temperature in the two-phase region will be explained below. The higher the temperature, the higher the proportion of austenite (hardened phase),
As the proportion of ferrite decreases, the C concentration in austenite decreases. The yield ratio and strength depend on the ratio of ferrite and hardened phase, the characteristics and distribution of each phase, and to obtain a low yield ratio and high strength (Hec, point +40℃) ~ (Acs
It is necessary to maintain the temperature in the two-phase region of 30°C.
次に少なくとも７００℃から２相域温度までの昇温速度
を１０℃／癲以下で加熱する理由について述べる。前述
のように降伏比および強度はフェライトと硬化相の各相
の割合、特性、分布に依存するが、各相の割合、特性は
主として２相域加熱温度に決定づけられる。これに対し
、各相の分布状況は７００℃から２相域加熱温度までの
昇温速度に影響され、この温度範囲の昇温速度を遅くす
るほどフェライト地に析出するオーステナイト（硬化相
ンが粗くなり、２相域温度から焼入れだ後の（フェライ
ト＋硬化相）混合組織も粗くなり、その結果低降伏比が
得られる。Next, the reason why the heating rate from at least 700° C. to the two-phase region temperature is set to 10° C./temperature or less will be described. As mentioned above, the yield ratio and strength depend on the ratio, characteristics, and distribution of each phase of ferrite and hardening phase, but the ratio and characteristics of each phase are mainly determined by the heating temperature in the two-phase region. On the other hand, the distribution of each phase is affected by the rate of temperature increase from 700℃ to the two-phase region heating temperature. The mixed structure (ferrite + hardened phase) after quenching from the two-phase region temperature also becomes coarse, resulting in a low yield ratio.
さらに、組織の粗さはＴｉおよびＮｂ含有量にも影響さ
れ、０．００５％を超えてＴｉ、 Ｎｂが不純物として
存在すると組織が細かくなる。そのためそれぞれ０．０
０５％以下に制限した。Furthermore, the roughness of the structure is also affected by the Ti and Nb contents, and if Ti and Nb are present as impurities in excess of 0.005%, the structure becomes finer. Therefore, each 0.0
It was limited to 0.5% or less.
２相域温度からの冷却速度は、空冷以上の冷却であれば
引張強さ７０ ｋｇ ｆ ／ ｉｊ以上の高強度が得ら
れるので、空冷以上の冷却速度とする。The cooling rate from the two-phase region temperature is set to a cooling rate higher than air cooling, since a high tensile strength of 70 kg f / ij or higher can be obtained if cooling is higher than air cooling.
２相域温度からの冷却で得られた脆い第２相はＡｃ１点
以下の焼もどし処理によって延靭性を向上できる。The brittle second phase obtained by cooling from the two-phase region temperature can improve ductility and toughness by tempering to an Ac point of 1 or less.
次に実施例に基づいて本発明を説明する。Next, the present invention will be explained based on examples.
〈実施例〉 第１表に供試材の化学成分を示す。<Example> Table 1 shows the chemical composition of the sample materials.
供試材Ａ−Ｇ鋼は本発明の成分範囲内からなる鋼で、Ｈ
，Ｉ鋼は比較鋼である。The test materials A-G steel are steels having compositions within the range of the present invention, and H
, I steel is a comparison steel.
これらの鋼を熔製し圧延スラブとした後、熱間圧延およ
び冷却し、−次加熱処理、再加熱処理および焼もどし処
理を施し、機械的性質を調べた。These steels were melted into rolled slabs, hot-rolled and cooled, and then subjected to secondary heat treatment, reheat treatment, and tempering treatment, and their mechanical properties were examined.
その結果を第２表に示す。従来法では降伏比が８０％以
上（ＡＩ、Ａ５、Ａ６、Ｈ，Ｉ綱）が、降伏比が８０％
以下でも衝撃吸収エネルギーｖｌＥｏが低い（Ａ２鋼）
か、引張強さが７０ｋｇＦ／−以下（Ａ６鋼）である。The results are shown in Table 2. In the conventional method, the yield ratio is 80% or more (AI, A5, A6, H, I steels);
Shock absorption energy vlEo is low even below (A2 steel)
Or, the tensile strength is 70 kgF/- or less (A6 steel).
本発明法では引張強さが７０ｋｇｆ／ｍｊで、８０％以
下の低降伏比が得られ、衝撃靭性も高い（Ａ３、Ａ４、
Ｂ１、Ｂ２、Ｃ，Ｄ、Ｅ、Ｆ、、Ｇ鋼）。The method of the present invention has a tensile strength of 70 kgf/mj, a low yield ratio of 80% or less, and high impact toughness (A3, A4,
B1, B2, C, D, E, F, G steel).
〈発明の効果〉
本発明により、従来の単純な２相域焼入れ一焼もどし処
理法では低降伏比化が困難であった引張強さ７０ｋｇｆ
／−以上の高張力鋼においても確実に８０％以下の低降
伏比化を達成することができるようになった。<Effects of the Invention> The present invention has achieved a tensile strength of 70 kgf, which was difficult to achieve with a conventional simple two-phase region quenching and tempering treatment method.
It has now become possible to reliably achieve a yield ratio as low as 80% or less even in high tensile strength steel of /- or more.
Claims (1)
５〜１．００％、Ｍｎ：０．５０〜１．８０％、Ｐ：０
．０４０％以下、Ｓ：０．０２０％以下、Ｎ：０．００
６０％以下、Ａｌ：０．０２０〜０．０８０％、Ｂ：０
．０００３〜０．００３０％を含み、さらにＮｉ：１．
５０％以下、Ｃｒ：０．８０％以下、Ｍｏ：０．２０〜
０．８０％およびＣｕ：０．５０％以下のうち１種以上
を含み、かつ不純物としてのＴｉ及びＮｂをそれぞれ０
．００５％以下に制限し、残部実質的にＦｅからなる鋼
を圧延終了後冷却したのち、Ａｃ＿３点以上の温度に加
熱後、空冷以上の冷却速度で冷却したのち、再度（Ａｃ
＿１点＋４０℃）〜（Ａｃ＿３点−３０℃）の（α＋γ
）２相域温度まで、少なくとも７００℃以上は１０℃／
ｍｍ以下の昇温速度で加熱した後、空冷以上の冷却速度
で冷却し、その後Ａｃ＿１点以下の温度で焼もどしを行
うことを特徴とする低降伏比高張力鋼の製造方法。In weight ratio, C: 0.05 to 0.25%, Si: 0.0
5-1.00%, Mn: 0.50-1.80%, P: 0
．． 040% or less, S: 0.020% or less, N: 0.00
60% or less, Al: 0.020-0.080%, B: 0
．． 0003 to 0.0030%, and further contains Ni:1.
50% or less, Cr: 0.80% or less, Mo: 0.20~
0.80% and Cu: 0.50% or less, and each contains 0 Ti and Nb as impurities.
．． 005% or less, and the remainder essentially consists of Fe. After rolling, the steel is cooled, heated to a temperature of Ac_3 or higher, cooled at a cooling rate of air cooling or higher, and then heated again (Ac
(α+γ of _1 point +40℃) to (Ac_3 point -30℃)
) Up to the two-phase region temperature, at least 10℃/over 700℃
A method for producing a low yield ratio high tensile strength steel, which comprises heating at a temperature increase rate of 1 mm or less, cooling at a cooling rate of air cooling or higher, and then tempering at a temperature of Ac_1 point or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21578490A JPH0499817A (en) | 1990-08-17 | 1990-08-17 | Production of high-tensile steel having low-yield ratio |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21578490A JPH0499817A (en) | 1990-08-17 | 1990-08-17 | Production of high-tensile steel having low-yield ratio |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0499817A true JPH0499817A (en) | 1992-03-31 |
Family
ID=16678176
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21578490A Pending JPH0499817A (en) | 1990-08-17 | 1990-08-17 | Production of high-tensile steel having low-yield ratio |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0499817A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04272129A (en) * | 1991-02-27 | 1992-09-28 | Nkk Corp | Production of high tension steel having low yield ratio |
| US6537391B2 (en) * | 2001-06-12 | 2003-03-25 | Ishikawajima-Harima Jukogyo Kabushiki Kaisha | Steel with improved impact penetration resistance and method for producing the same |
-
1990
- 1990-08-17 JP JP21578490A patent/JPH0499817A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04272129A (en) * | 1991-02-27 | 1992-09-28 | Nkk Corp | Production of high tension steel having low yield ratio |
| US6537391B2 (en) * | 2001-06-12 | 2003-03-25 | Ishikawajima-Harima Jukogyo Kabushiki Kaisha | Steel with improved impact penetration resistance and method for producing the same |
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