JPS63118012A - Production of low yield ratio high tensile thick steel plate - Google Patents
Production of low yield ratio high tensile thick steel plateInfo
- Publication number
- JPS63118012A JPS63118012A JP26510786A JP26510786A JPS63118012A JP S63118012 A JPS63118012 A JP S63118012A JP 26510786 A JP26510786 A JP 26510786A JP 26510786 A JP26510786 A JP 26510786A JP S63118012 A JPS63118012 A JP S63118012A
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- transformation point
- less
- heating
- steel
- 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.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 51
- 239000010959 steel Substances 0.000 title claims abstract description 51
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 238000010438 heat treatment Methods 0.000 claims abstract description 56
- 230000009466 transformation Effects 0.000 claims abstract description 34
- 238000001816 cooling Methods 0.000 claims abstract description 21
- 238000005098 hot rolling Methods 0.000 claims abstract description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 12
- 230000001186 cumulative effect Effects 0.000 claims abstract description 10
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 9
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract 5
- 229910052750 molybdenum Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 229910052796 boron Inorganic materials 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 abstract description 5
- 230000000694 effects Effects 0.000 description 16
- 239000002131 composite material Substances 0.000 description 11
- 229910000859 α-Fe Inorganic materials 0.000 description 11
- 229910001566 austenite Inorganic materials 0.000 description 10
- 238000000034 method Methods 0.000 description 10
- 238000005096 rolling process Methods 0.000 description 9
- 229910000734 martensite Inorganic materials 0.000 description 8
- 239000002244 precipitate Substances 0.000 description 8
- 230000001965 increasing effect Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 239000010953 base metal Substances 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000001112 coagulating effect Effects 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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、低温靭性の優れた低降伏比高張力鋼板の製造
法、特に、ラインパイプ、圧力容器あるいは一般構造用
鋼として使用される高強度、高靭性の低降伏比高張力厚
鋼板の製造法に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing high-strength steel sheets with low yield ratios and excellent low-temperature toughness, particularly for high-strength steel sheets used as line pipes, pressure vessels, or general structural steel. The present invention relates to a method for producing high strength, high toughness, low yield ratio, high tensile strength steel plates.
（発明の技術的背景）
ラインパイプ用鋼板をはじめとする厚鋼板では高張力化
が著しく、それに伴い、降伏応力の増加によって、ｕＯ
プレス等曲げ加工が難しくなってきており、さらにスプ
リングバック、座屈等の問題から降伏比の高い高張力鋼
では製管時の精度を確保するのが困難になってきている
。さらに近年、海底パイプラインの施設が増加している
゛が、降伏比の高いパイプでは施設時に生ずる応力によ
って座屈する可能性が生じている。このような動向から
、低降伏比を有する厚鋼板の開発が望まれている。(Technical background of the invention) The tensile strength of thick steel plates, including line pipe steel plates, has increased significantly, and as a result, the yield stress has increased, resulting in uO
It has become difficult to perform bending processes such as pressing, and it has also become difficult to ensure accuracy during pipe manufacturing with high-strength steels that have a high yield ratio due to problems such as springback and buckling. Furthermore, in recent years, the number of submarine pipeline facilities has increased, but pipes with a high yield ratio may buckle due to the stress generated during construction. In view of these trends, there is a desire for the development of thick steel plates with a low yield ratio.
（従来の技術と問題点）
従来より低降伏比鋼の製、造法に関しては種々検討がな
されており、例えば特開昭５９−２１１５３３号では熱
間圧延もしくは冷間圧延後、（α＋γ）二相共存域に加
熱後冷却してフェライトとマルテンサイトの複合組織に
することによって低降伏比鋼を得る方法が示されている
。また、特公昭５９−５２２０７号では低温γ域（５９
５０℃）で大圧下（累積圧下率にて３０〜９０％）を含
む熱間圧延によって鋼板を成形した後、まずオーステナ
イト相域に加熱後焼入れし、ざらに（α＋γ）二相域に
加熱後空冷することによってマルテンサイトとフェライ
トの微細な混合ａ織を得て低降伏比化する方法が示され
ている。(Prior art and problems) Various studies have been made regarding the production and manufacturing methods of low yield ratio steel. For example, in Japanese Patent Application Laid-Open No. 59-211533, after hot rolling or cold rolling, (α+γ)2 A method of obtaining a low yield ratio steel by heating to a phase coexistence region and then cooling to form a composite structure of ferrite and martensite is shown. In addition, in Special Publication No. 59-52207, low-temperature γ region (59
After forming a steel plate by hot rolling with a large reduction (30 to 90% in cumulative reduction ratio) at 50℃), it is first heated to an austenite phase region and then quenched, and then heated to a rough (α + γ) two-phase region. A method is shown in which a fine mixed a-weave of martensite and ferrite is obtained by air cooling to achieve a low yield ratio.
しかし、前者の如く、単に熱延材を（α＋γ）二相域に
加熱する方法ではフェライト、マルテンサイト両相とも
粗大化は避けられず、低降伏比鋼は得られるものの、寒
冷地での使用に耐え得るだけの低温靭性を付与させるこ
とは不可能である。However, if the hot-rolled material is simply heated to the (α + γ) two-phase region, as in the former method, coarsening of both the ferrite and martensite phases is inevitable, and although a low yield ratio steel can be obtained, it is difficult to use it in cold regions. It is impossible to impart sufficient low-temperature toughness to withstand this.
また後者の方法においても、組織の微細化によって比較
的良好な低温靭性が得られるものの、マルテンサイト相
が（α＋γ）域加熱時にほとんど完全に焼きもどされて
しまうことなどから十分に低降伏比化することが難しく
、降伏比７０％以下を達成することはできない、また１
回以上のクロス圧延を行う必要があるなどプロセスの複
雑化による製造コストの上昇と圧延能力の低下は避けら
れないものである。In the latter method, although relatively good low-temperature toughness can be obtained by refining the structure, the martensitic phase is almost completely tempered during heating in the (α + γ) region, so it is difficult to obtain a sufficiently low yield ratio. It is difficult to achieve a yield ratio of 70% or less, and 1
An increase in manufacturing costs and a decrease in rolling capacity due to the complexity of the process, such as the need to perform cross rolling more than once, are unavoidable.
（発明の目的）
本発明の目的は、こうした問題点を排除しつつ、より製
造効率の高い低温靭性の優れた低降伏比高張力厚鋼板の
製造法を提供せんとするものである。(Object of the Invention) An object of the present invention is to provide a method for producing a high-strength thick steel plate with a high production efficiency and excellent low-yield ratio and high tensile strength while eliminating these problems.
本発明の別の目的は、微細な複合組織化によって良好な
低温靭性を確保しつつ、かつ７０％以下の低降伏比を有
する高張力厚鋼板の製造法を提供することである。Another object of the present invention is to provide a method for producing a high-strength steel plate having a low yield ratio of 70% or less while ensuring good low-temperature toughness through a fine composite structure.
（問題点を解決するための手段）
本発明者らは、加工熱処理プロセスを用いて、低降伏比
鋼を製造する方法を種々検討した結果、次のような知見
を得た。(Means for Solving the Problems) The present inventors have studied various methods of manufacturing low yield ratio steel using a working heat treatment process, and have obtained the following knowledge.
すなわち、鋼組成にＮｂ、 ＶおよびＴ１の１種または
２種以上を含有させることによりこれらの元素の炭窒化
物を析出させ、組織の微細化をはかるとともに、それに
続く熱処理期間中も析出物の４１集粗大化が起こらない
ように制御することにより低温靭性の確保がはかられ、
そしてこれらの総合的効果として降伏比７０％以下が実
現されることを知り、本発明を完成した。That is, by including one or more of Nb, V, and T1 in the steel composition, carbonitrides of these elements are precipitated to refine the structure, and the precipitates are also prevented during the subsequent heat treatment. Low-temperature toughness is ensured by controlling the 41 aggregate to prevent coarsening.
The present invention was completed based on the knowledge that a yield ratio of 70% or less can be achieved as a comprehensive effect.
ここに、本発明の要旨とするところは、重量％にて、
Ｃ：０．０２〜０．２０％、 Ｓｉ：１．０％以下、
Ｍｎ：０．５〜２．０ ％、 ｓｏ＋．Ａｌ：ｏ
、Ｏｔ 〜０．１ ％さらに
Ｎｂ：０．０１〜０．１５％、Ｔｉ：０．ＯＬ〜０．１
５％およびシ：０．Ｏ］〜０．１５％のうち１種または
２種以上、ならびに所望により、
Ｃｒ：０．０５〜１．０％、Ｍｏ：０．０５〜１．０％
、Ｃｕ：０．１〜１．０％、Ｎｉ：０．１〜３．０％、
およびＢ：０．０Ｏ０５〜０．００２％のうち１種また
は２種以上、および／または
ＣａおよびＲＥＭそれぞれ０．０１％以下のうち１種ま
たは２種以上含有し、
残部鉄および不可避不純物
からなる鋼に少なくとも９５０℃以下の累積圧下率が４
０％以上の熱間圧延を行い、該熱間圧延終了後、室温ま
たはＡｒ、変態点−５０℃以下の任意の温度から３°ｃ
７ｓ以上の加熱速度にてＡｃ１変態点〜Ａｃｚ変態点の
温度域に加熱後直くまたは５分以下の時間保持してから
冷却することを特徴とする低温靭性の優れた低降伏比高
張力厚鋼板の製造法である。Here, the gist of the present invention is, in weight%, C: 0.02 to 0.20%, Si: 1.0% or less,
Mn: 0.5-2.0%, so+. Al:o
, Ot ~0.1%, further Nb: 0.01~0.15%, Ti: 0. OL~0.1
5% and 0. O]~0.15%, and optionally, Cr: 0.05~1.0%, Mo: 0.05~1.0%
, Cu: 0.1-1.0%, Ni: 0.1-3.0%,
and B: Contains one or more of 0.0O05 to 0.002%, and/or one or more of Ca and REM each of 0.01% or less, with the balance consisting of iron and inevitable impurities. The steel has a cumulative reduction rate of at least 950℃ or less of 4
0% or more hot rolling, and after the hot rolling is completed, the temperature is 3°C from room temperature or Ar, any temperature below the transformation point -50°C.
Low yield ratio, high tensile strength and excellent low-temperature toughness characterized by heating to a temperature range of Ac1 transformation point to Acz transformation point at a heating rate of 7 seconds or more, or cooling after holding for a time of 5 minutes or less. This is a method of manufacturing steel plates.
すなわち、本発明によれば、Ｎｂ、 ＶおよびＴｉを１
種以上含有する鋼に対して、９５０℃以下の低温Ｔ域に
て累積圧下率４０％以上の熱間圧延を行うことによ−７
，て、まず微細な炭窒化物を均一分散した微細なフェラ
イト組織を得る。ここで、９５０ ・ｃ以下の温度域で
行う大圧下は微粒組織を１゛）ると同時に鋼中に微細な
歪誘起析出物を分散させる上で極めて重要な工程である
。こうした微細析出物は後の熱処理におけるオーステナ
イ１の核生成サイトとなり、微細γ粒を生成させるだけ
でなく、オーステナイト、フェライト両相の加熱中の粒
成長を著しく抑制する効果がある。また、熱間圧延後の
冷却速度は特に限定しないが、組織の微細化（細粒フェ
ライト−微細ヘイティ１−−マルテンサイト）という点
で冷却速度は大きい程望ましい。つまり、熱間圧延終了
後は、そのま−室温にまで冷却してもよい。しかし、そ
の熱延［才はＡｃ＋変！声点〜Ａｃ＋変態点の温度域に
まで再加熱されるため、室温にまで冷却しなくとも、Ａ
ｒ、変態点−５０℃以下にまで冷却すれば、その温度か
ら再加熱してもよい。That is, according to the present invention, Nb, V and Ti are
-7 by hot rolling steel containing at least 40% of the total rolling stock at a cumulative reduction rate of 40% or more in the low temperature T range of 950°C or less.
First, a fine ferrite structure in which fine carbonitrides are uniformly dispersed is obtained. Here, the large reduction carried out in a temperature range of 950 °C or lower is an extremely important step for improving the fine grain structure and at the same time dispersing fine strain-induced precipitates in the steel. These fine precipitates serve as nucleation sites for austenite 1 in the subsequent heat treatment, and have the effect of not only producing fine γ grains but also significantly suppressing grain growth of both austenite and ferrite phases during heating. Further, the cooling rate after hot rolling is not particularly limited, but the higher the cooling rate is, the more desirable it is in terms of refining the structure (fine grain ferrite - fine heity 1 - martensite). That is, after the hot rolling is completed, it may be cooled to room temperature. However, the hot rolling [talent is Ac + strange! Since it is reheated to the temperature range from voice point to Ac + transformation point, A
r. If it is cooled to below the transformation point -50°C, it may be reheated from that temperature.
このように、引き続き組織の複合化のためにオーステナ
イト＋フエライトニ相共存温度域に加熱を行うが、この
際、最終製品の低温靭性を確保する上で特に重要なのが
加熱速度を３℃／Ｓ以上、好ましくはｌＯ℃／Ｓ以上に
することと、昇温後のＡｃ。In this way, heating is continued to the temperature range where the austenite and ferrite coexist in order to create a composite structure, but at this time, it is especially important to keep the heating rate at 3°C/S or higher in order to ensure the low-temperature toughness of the final product. , preferably 10° C./S or more, and Ac after heating.
変態点〜Ａｃ３変態点の温度域における保持時間を５分
以下に制限することである。これらの熱処理条件の制約
は、α−Ｔ変態時の駆動力を大にし、微細なオーステナ
イトを析出させると同時に加熱中の微細析出物の凝集粗
大化を防いでオーステナイト−フェライト複合組織の粗
大化を抑制し、さらに析出強化能のσ友少による強度低
下を防止する。The purpose is to limit the holding time in the temperature range from the transformation point to the Ac3 transformation point to 5 minutes or less. These restrictions on heat treatment conditions increase the driving force during α-T transformation, precipitate fine austenite, and at the same time prevent the fine precipitates from coagulating and coarsening during heating, thereby preventing coarsening of the austenite-ferrite composite structure. In addition, it prevents a decrease in strength due to a decrease in precipitation strengthening ability.
つまり、本発明者にあっては、複合組織の微細化による
低温靭性の確保と析出強化の促進を図るべく、加熱速度
と保持時間を上述の如く制限するものである。ここで加
熱速度を３℃／Ｓ以上にする手段としてはガス炎による
加熱、赤外線加熱および誘導加熱等が考えられるが、温
度制御の正確さや経済性から判断して、厚鋼板に対して
は誘導加熱方式が最も望ましい。That is, the inventors of the present invention limit the heating rate and holding time as described above in order to ensure low-temperature toughness and promote precipitation strengthening by making the composite structure finer. Here, heating with gas flame, infrared heating, induction heating, etc. can be considered as a means of increasing the heating rate to 3℃/S or more, but judging from the accuracy of temperature control and economical efficiency, induction heating is recommended for thick steel plates. Heating method is most desirable.
さらに急速、短時間二用域加熱によって得られた微細な
フェライト−オーステナイト混合組織はその後の冷却に
よってマルテンサイトを含む微細複合相８ヨとなるが、
ここでも、Ｎｂ、 ＶおよびＴｉの添加は鋼の焼入性を
高め、マルテンサイト化を促進する土で重要な役割を持
つ、また、冷却前のオーステナイト率は冷却中のマルテ
ンサイト変態を容易にする上で体積率５〜５０％にコン
トロールすることが望ましい。Furthermore, the fine ferrite-austenite mixed structure obtained by rapid and short-time double-zone heating becomes a fine composite phase containing martensite by subsequent cooling.
Again, the addition of Nb, V and Ti plays an important role in soil enhancing the hardenability of the steel and promoting martensitic transformation, and the austenite fraction before cooling facilitates the martensitic transformation during cooling. It is desirable to control the volume ratio to 5 to 50%.
Ｃ：Ｃは強度確保のため０，０２％以上必要とし、−方
０．２０％を越えて含有させると、母材および溶接部の
靭性劣化を招くようになることからその含有量を０．０
２〜０．２０％と定めた。C: 0.02% or more of C is required to ensure strength, and if it is contained in excess of 0.20%, the toughness of the base metal and weld zone will deteriorate, so the content should be reduced to 0.02% or more. 0
It was set at 2 to 0.20%.
Ｓｉ： Ｓｉは鋼の脱酸剤として有効であり、また固溶
強化を通じて強度上昇に有効であるが、１．０％を越え
ると靭性および溶接性に悪影響を及ぼすことから上限を
１．０％とした。Si: Si is effective as a deoxidizing agent for steel and is also effective in increasing strength through solid solution strengthening, but if it exceeds 1.0% it will have a negative effect on toughness and weldability, so the upper limit should be set at 1.0%. And so.
Ｍｎ： Ｍｎは鋼の強度並びに靭性を向上させ、また焼
入性を向上させることから低降伏比に有効な元素である
が、０．５％未満ではこうした効果が期待できず、また
２、０％を超えると溶接性を劣化させるため、その含有
量を０，５〜２．０％と定めた。Mn: Mn improves the strength and toughness of steel, as well as improves hardenability, so it is an effective element for lowering the yield ratio. However, if it is less than 0.5%, such effects cannot be expected; %, the weldability deteriorates, so the content was set at 0.5 to 2.0%.
ｓｏｌ．Ａｌ： ＡＱは鋼の脱酸および結晶粒の微細化
のために添加されるが、ｓｏｌ、ＡＱｆｔにて０．０１
％未満ではその効果が望めず、一方、ｓ ｏ Ｉ 、
Ａ、Ｑ、ｆＪを０゜１％を超えて含有させると、非金属
介在物の蛍が急激に増加して鋼の靭性が劣化するように
なることからその含有量を０．０１〜０．１％と定めた
。sol. Al: AQ is added for deoxidizing steel and refining grains, but 0.01 in sol, AQft
%, the effect cannot be expected; on the other hand, s o I,
If A, Q, and fJ are contained in excess of 0.1%, the number of nonmetallic inclusions will rapidly increase and the toughness of the steel will deteriorate. It was set at 1%.
Ｎｂ、 ＶおよびＴｉ： これらの元素は本発明におい
て特に重要な役割を持つ元素である。オーステナイト中
あるいはフェライト中に炭窒化物として析出し、鋼の強
度を向上させると同時に、所定の熱履歴によって生ずる
複合組織を微細化し、鋼の靭性を向上させる作用がある
が、各々０．０１％未満ではその効果が望めず、一方、
０．１５％を超えて含有すると、溶接部の靭性が劣化し
、母材の低降伏比化が得られなくなるので、その含有量
をそれぞれ０．０１〜０．１５％と定めた。本発明にあ
ってはそのうちの１種または２種以上が含有される。Nb, V and Ti: These elements play a particularly important role in the present invention. They precipitate as carbonitrides in austenite or ferrite, and have the effect of improving the strength of steel, as well as refining the composite structure produced by a given thermal history and improving the toughness of steel. If the amount is less than that, the effect cannot be expected; on the other hand,
If the content exceeds 0.15%, the toughness of the weld zone deteriorates and it becomes impossible to obtain a low yield ratio of the base metal, so the content was determined to be 0.01 to 0.15%. In the present invention, one or more of them are contained.
Ｃｒ、 Ｍｏ、Ｃｕ、ＮｉおよびＢ：これらの元素は所
望添加元素で、強度、耐食性および焼入性をさらに改善
する必要があるときに所望により１種または２種以上添
加してもよい。これらの各元素の添加量は以下の理由に
より限定される。Cr, Mo, Cu, Ni, and B: These elements are optional addition elements, and one or more of these elements may be added as desired when it is necessary to further improve strength, corrosion resistance, and hardenability. The amount of each of these elements added is limited by the following reasons.
Ｃｒ＋ Ｍｏ：
これらの成分には鋼の強度および焼入性を向上させる作
用があるが、それぞれ０．０５％未満ではその効果が期
待できず、一方、それぞれ１．０％を超えると母材およ
び溶接部の靭性を劣化するようになることがらＣｒおよ
びＭｏいずれも０．０５〜１．０％に限定した。Cr + Mo: These components have the effect of improving the strength and hardenability of steel, but if each is less than 0.05%, the effect cannot be expected, while if each exceeds 1.0%, the base material and Both Cr and Mo were limited to 0.05 to 1.0% since they deteriorated the toughness of the welded part.
Ｃｕ：
Ｃｕには鋼の強度および焼入性、ならびに耐食性を向上
させる効果があるが、０．１％未満では効果が望めず、
また１、０％を超えて含有させるとスラブに熱間割れが
発生しやすくなるごとから、その含有量を０．１〜１゜
０％と定めた。Cu: Cu has the effect of improving the strength, hardenability, and corrosion resistance of steel, but if it is less than 0.1%, no effect can be expected;
In addition, if the content exceeds 1.0%, hot cracking tends to occur in the slab, so the content was set at 0.1 to 1.0%.
ＮＩ；
Ｎｉには鋼の強度、靭性、焼入性ならびに耐食性を向上
させる効果があるが；０．１％未満では効果が望めず、
また３％を超えると母材および溶接部の靭性を劣化させ
るようになることから、その含有量を０．１〜３．０％
と定めた。NI: Ni has the effect of improving the strength, toughness, hardenability, and corrosion resistance of steel; however, if it is less than 0.1%, no effect can be expected;
In addition, if it exceeds 3%, the toughness of the base metal and welded part will deteriorate, so the content should be reduced to 0.1 to 3.0%.
It was determined that
Ｂ：
Ｂは強度増加に有効な元素であるが、その添加量が０．
０００５％未満では効果が望めず、０．００２％を超え
るとｌユ材および溶接部の靭性を劣化させるようになる
ことから、下限をｏ、ｏｏｏｓ％、上限を０．００２％
と定めた。B: B is an element effective in increasing strength, but when the amount added is 0.
If it is less than 0.0005%, no effect can be expected, and if it exceeds 0.002%, the toughness of the material and welded part will deteriorate, so the lower limit is set to o, oos% and the upper limit is set to 0.002%.
It was determined that
Ｃａ、 ＲＩＥＭ：
これらの元素も所望添加元素であり、それらは介在物の
形態制御により、靭性および延性改善に効果があるが、
０．０１％を超えて含まれると逆に靭性を害するため上
限を０゜０１％とした。Ca, RIEM: These elements are also desired additive elements, and they are effective in improving toughness and ductility by controlling the morphology of inclusions.
If the content exceeds 0.01%, the toughness will be adversely affected, so the upper limit was set at 0°01%.
Ｃ熱間圧延）
・９５０℃以下の累積圧下率：
９５０℃以下の温度域における圧下は■熱処理前のＭｉ
織の微細化および■歪誘起析出物の分散化乙こよって、
その後の熱処理によって得られる複合組織を微細化し、
靭性を向とさゼる効果がある。これらの効果は累（責圧
下率（板厚減少率）二二で４０９′Ｑ以上で有効である
。好ましくは累積圧Ｆ率は５０％以上である。C hot rolling) ・Cumulative rolling reduction rate below 950°C: The rolling reduction in the temperature range below 950°C is ■Mi before heat treatment
Refinement of the texture and dispersion of strain-induced precipitates.
The composite structure obtained by subsequent heat treatment is refined,
It has the effect of increasing toughness. These effects are effective when the cumulative reduction rate (plate thickness reduction rate) is 409'Q or more. Preferably, the cumulative reduction rate is 50% or more.
（熱処理）
・圧延後の加熱開始温度：
圧延後、再び加熱を行うにあたり、その開始温度がＡｒ
＝変態点−５０℃超では複合組織が得られず、低降伏比
化しないため、圧延後の加熱開始温度を＾ｒ３変態点−
５０℃以下と定めた。−旦室温に冷却したものは室温か
ら開始する。(Heat treatment) ・Heating start temperature after rolling: When heating is performed again after rolling, the start temperature is Ar
= Transformation point - Since a composite structure cannot be obtained and a low yield ratio cannot be obtained at temperatures exceeding 50°C, the heating start temperature after rolling is set to ^r3 transformation point -
The temperature was set at 50℃ or less. - Once cooled to room temperature, start at room temperature.
・加熱速度：
熱処理時の加熱温度が３℃／Ｓ未満だと、加熱中にフェ
ライト粒が成長したり、逆変態によって生ずるオーステ
ナイ１−粒が粗大化し、本発明が目的とする微細な複合
Ｍｌ織が得られず、靭性が劣化するため加熱速度を３℃
／Ｓ以上と定めた。好ましくは１０℃／Ｓ以上である。・Heating rate: If the heating temperature during heat treatment is less than 3°C/S, ferrite grains will grow during heating, or austenite grains produced by reverse transformation will become coarser, resulting in fine composite Ml, which is the object of the present invention. The heating rate was lowered to 3℃ because the weave could not be obtained and the toughness deteriorated.
/S or higher. Preferably it is 10°C/S or more.
・加熱温度：
加熱温度がＡＣ３変停点を超えたり、ＡＣＩ変態点未満
の場合、複合Ｍ１織化セず低降伏比鋼が得られないため
、加熱温度をＡＣ１変態点以下、ＡＣ３変態点以下と定
めた。材質を安定化させる上ではＡｃ＋ ＋ ２０’ｃ
−Ａｃｉ −５０℃の温度域の加熱が望ましい。・Heating temperature: If the heating temperature exceeds the AC3 transformation point or is below the ACI transformation point, a composite M1 woven steel with low yield ratio cannot be obtained, so the heating temperature should be set below the AC1 transformation point or below the AC3 transformation point. It was determined that In order to stabilize the material, Ac+ + 20'c
-Aci Heating in the temperature range of -50°C is desirable.
保持時間：
Ａｃ＋変態点からＡｃ３変態点間の温度域における保持
時間は５分を超えると鋼中の微細析出物が凝縮、粗大化
し、鋼板の強度が低下ばかりでなく、フェライト、オー
ステナイト両相の粗大化を招き、靭性が劣化するため、
５分以下と定めた。Holding time: If the holding time in the temperature range between the Ac+ transformation point and the Ac3 transformation point exceeds 5 minutes, the fine precipitates in the steel will condense and become coarse, which will not only reduce the strength of the steel sheet but also cause the formation of both ferrite and austenite phases. This leads to coarsening and deterioration of toughness.
The duration was set at 5 minutes or less.
次に、本発明をその実施例によってさらに具体的に説明
する。Next, the present invention will be explained in more detail with reference to examples thereof.
（実施例）
第１表に示す化学成分組成の鋼片を第２表に示す軌間圧
延および熱処理にて板厚２０ｍｍの鋼板を製必した。熱
処理は誘導加熱装置を用い、比較例として電気炉加熱も
行った。(Example) Steel slabs having the chemical composition shown in Table 1 were subjected to gauge rolling and heat treatment shown in Table 2 to produce steel plates with a thickness of 20 mm. The heat treatment was performed using an induction heating device, and heating in an electric furnace was also performed as a comparative example.
熱処理後の冷却条件としては、■加熱温度より放冷（第
２表中「放冷」と表示）、■加熱温度より５００℃まで
ｌＯ℃／Ｓで加連冷ｔＪＩ後、放冷（第２表中「加速冷
却」）および■加熱温度より水焼入れ（第２表中ｒＤＱ
Ｊと表示）の３１重を行った。The cooling conditions after heat treatment include: ■ Cooling by cooling from the heating temperature (indicated as "cooling" in Table 2); ■ Cooling by continuous cooling tJI from the heating temperature to 500°C at 10°C/S, followed by cooling by cooling (second "Accelerated cooling" in the table) and ■Water quenching from the heating temperature (rDQ in Table 2)
31 times (denoted as J) were performed.
本発明にしたがって製造された鋼は低温靭性に優れ、し
かも７０ン６以下の低降伏比高張力鋼となっている。か
かる低降伏比高張力鋼１は従来前られることはなかった
。The steel produced according to the present invention has excellent low temperature toughness and is a high tensile strength steel with a low yield ratio of 70 N6 or less. Such a low yield ratio high tensile strength steel 1 has never been developed before.
Claims (4)
：０．５〜２．０％、ｓｏｌ．Ａｌ：０．０１〜０．１
％を含有し、さらに Ｎｂ：０．０１〜０．１５％、Ｔｉ：０．０１〜０．１
５％およびＶ：０．０１〜０．１５％のうち１種または
２種以上含有し、 残部鉄および不可避不純物 からなる鋼に少なくとも９５０℃以下の累積圧下率が４
０％以上の熱間圧延を行い、該熱間圧延の終了後、室温
またはＡｒ＿３変態点−５０℃以下の任意の温度から３
℃／Ｓ以上の加熱速度にてＡｃ＿１変態点〜Ａｃ＿３変
態点の温度域に加熱後直ぐまたは５分以下の時間保持し
てから冷却することを特徴とする低温靭性の優れた低降
伏比高張力厚鋼板の製造法。(1) C: 0.02 to 0.20%, Si: 1.0% or less, Mn in weight%
:0.5-2.0%, sol. Al: 0.01-0.1
%, further Nb: 0.01-0.15%, Ti: 0.01-0.1
5% and V: 0.01 to 0.15%, and the balance is iron and unavoidable impurities.
0% or more hot rolling is performed, and after the hot rolling is completed, the temperature is reduced from room temperature or any temperature below Ar_3 transformation point -50°C.
Low yield ratio and high tensile strength with excellent low-temperature toughness characterized by heating to a temperature range of Ac_1 transformation point to Ac_3 transformation point at a heating rate of ℃/S or higher immediately after heating or after cooling after holding for 5 minutes or less. Manufacturing method for thick steel plates.
：０．５〜２．０％、ｓｏｌ．Ａｌ：０．０１〜０．１
％さらに Ｎｂ：０．０１〜０．１５％、Ｔｉ：０．０１〜０．１
５％およびＶ０．０１〜０．１５％のうち１種または２
種以上、ならびに Ｃｒ：０．０５〜１．０％、Ｍｏ：０．０５〜１．０％
、Ｃｕ：０．１〜１．０％、Ｎｉ：０．１〜３．０％、
およびＢ：０．０００５〜０．００２％のうち１種また
は２種以上含有し、残部鉄および不可避不純物 からなる鋼に少なくとも９５０℃以下の累積圧下率が４
０％以上の熱間圧延を行い、該熱間圧延の終了後、室温
またはＡｒ＿３変態点−５０℃以下の任意の温度から３
℃／Ｓ以上の加熱速度にてＡｃ＿１変態点〜Ａｃ＿３変
態点の温度域に加熱後直ぐまたは５分以下の時間保持し
てから冷却することを特徴とする低温靭性の優れた低降
伏比高張力厚鋼板の製造法。(2) In weight%, C: 0.02 to 0.20%, Si: 1.0% or less, Mn
:0.5-2.0%, sol. Al: 0.01-0.1
% further Nb: 0.01-0.15%, Ti: 0.01-0.1
5% and one or two of V0.01-0.15%
species, and Cr: 0.05-1.0%, Mo: 0.05-1.0%
, Cu: 0.1-1.0%, Ni: 0.1-3.0%,
and B: 0.0005 to 0.002%, the steel contains one or more of 0.0005 to 0.002%, and the balance is iron and unavoidable impurities, and the cumulative reduction rate of at least 950°C or less is 4.
0% or more hot rolling is performed, and after the hot rolling is completed, the temperature is reduced from room temperature or any temperature below Ar_3 transformation point -50°C.
Low yield ratio and high tensile strength with excellent low-temperature toughness characterized by heating to a temperature range of Ac_1 transformation point to Ac_3 transformation point at a heating rate of ℃/S or higher immediately after heating or after cooling after holding for 5 minutes or less. Manufacturing method for thick steel plates.
：０．５〜２．０％、ｓｏｌ．Ａｌ：０．０１〜０．１
％さらに Ｎｂ：０．０１〜０．１５％、Ｔｉ：０．０１〜０．１
５％およびＶ：０．０１〜０．１５％のうち１種または
２種以上、ならびに、 ＣａおよびＲＥＭそれぞれ０．０１％以下のうち１種ま
たは２種以上含有し、 残部鉄および不可避不純物 からなる鋼に少なくとも９５０℃以下の累積圧下率が４
０％以上の熱間圧延を行い、該熱間圧延終了後、室温ま
たはＡｒ＿３変態点−５０℃以下の任意の温度から３℃
／Ｓ以上の加熱速度にてＡｃ＿１変態点〜Ａｃ＿３変態
点の温度域に加熱後直ぐまたは５分以下の時間保持して
から冷却することを特徴とする低温靭性の優れた低降伏
比高張力厚鋼板の製造法。(3) In weight%, C: 0.02 to 0.20%, Si: 1.0% or less, Mn
:0.5-2.0%, sol. Al: 0.01-0.1
% further Nb: 0.01-0.15%, Ti: 0.01-0.1
5% and V: Contains one or more of 0.01 to 0.15%, and one or more of Ca and REM each of 0.01% or less, with the balance being iron and unavoidable impurities. The steel has a cumulative reduction rate of at least 950℃ or less of 4
0% or more hot rolling, and after the hot rolling is completed, the temperature is reduced to 3°C from room temperature or any temperature below Ar_3 transformation point -50°C.
A low yield ratio and high tensile thickness with excellent low-temperature toughness characterized by heating to a temperature range of Ac_1 transformation point to Ac_3 transformation point at a heating rate of /S or more immediately after heating or after cooling after holding for a time of 5 minutes or less. Manufacturing method of steel plate.
：０．５〜２．０％、ｓｏｌ．Ａｌ：０．０１〜０．１
％さらに Ｎｂ：０．０１〜０．１５％、Ｔｉ：０．０１〜０．１
５％およびＶ：０．０１〜０．１５％のうち１種または
２種以上、Ｃｒ：０．０５〜１．０％、Ｍｏ：０．０５
〜１．０％、Ｃｕ：０．１〜１．０％、Ｎｉ：０．１〜
３．０％、およびＢ：０．０００５〜０．００２％のう
ち１種または２種以上、 ならびに、 ＣａおよびＲＥＭそれぞれ０．０１％以下のうち１種ま
たは２種以上含有し、 残部鉄および不可避不純物 からなる鋼に少なくとも９５０℃以下の累積圧下率が４
０％以上の熱間圧延を行い、該熱間圧延終了後、室温ま
たはＡｒ、変態点−５０℃以下の任意の温度から３℃／
Ｓ以上の加熱速度にてＡｃ＿１変態点〜Ａｃ＿３変態点
の温度域に加熱後直ぐまたは５分以下の時間保持してか
ら冷却することを特徴とする低温靭性の優れた低降伏比
高張力厚鋼板の製造法。(4) In weight%, C: 0.02 to 0.20%, Si: 1.0% or less, Mn
:0.5-2.0%, sol. Al: 0.01-0.1
% further Nb: 0.01-0.15%, Ti: 0.01-0.1
5% and V: one or two or more of 0.01 to 0.15%, Cr: 0.05 to 1.0%, Mo: 0.05
~1.0%, Cu: 0.1~1.0%, Ni: 0.1~
3.0%, and B: 0.0005 to 0.002%, and one or more of Ca and REM, each of 0.01% or less, the balance being iron and Steel containing unavoidable impurities has a cumulative reduction rate of at least 950℃ or less.
0% or more hot rolling is performed, and after the hot rolling is completed, the temperature is reduced to 3°C/3°C from room temperature or Ar, any temperature below the transformation point -50°C.
A thick steel plate with low yield ratio and high tensile strength having excellent low-temperature toughness, characterized in that it is heated to a temperature range of Ac_1 transformation point to Ac_3 transformation point at a heating rate of S or more, or is cooled immediately after being held for a time of 5 minutes or less. manufacturing method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26510786A JPS63118012A (en) | 1986-11-07 | 1986-11-07 | Production of low yield ratio high tensile thick steel plate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26510786A JPS63118012A (en) | 1986-11-07 | 1986-11-07 | Production of low yield ratio high tensile thick steel plate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS63118012A true JPS63118012A (en) | 1988-05-23 |
Family
ID=17412701
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26510786A Pending JPS63118012A (en) | 1986-11-07 | 1986-11-07 | Production of low yield ratio high tensile thick steel plate |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63118012A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996023909A1 (en) * | 1995-02-03 | 1996-08-08 | Nippon Steel Corporation | High-strength line-pipe steel having low yield ratio and excellent low-temperature toughness |
| EP0747496A1 (en) * | 1995-06-08 | 1996-12-11 | Sollac S.A. | Hot rolled steel sheet with high strength and good deep-drawing properties, containing titanium and process for its manufacturing |
| JP2006283187A (en) * | 2005-03-09 | 2006-10-19 | Jfe Steel Kk | Production method of high-strength/high-toughness steel |
| JP2008075107A (en) * | 2006-09-20 | 2008-04-03 | Jfe Steel Kk | Method for manufacturing high-strength/high-toughness steel |
| CN102965574A (en) * | 2012-12-09 | 2013-03-13 | 新余钢铁集团有限公司 | Titanium microalloying hot-rolling thick steel plate with low yield ratio and high strength and production process of steel plate |
| CN105908082A (en) * | 2016-04-01 | 2016-08-31 | 唐山钢铁集团有限责任公司 | Ti-microalloyed Q345B steel plate and production method thereof |
-
1986
- 1986-11-07 JP JP26510786A patent/JPS63118012A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996023909A1 (en) * | 1995-02-03 | 1996-08-08 | Nippon Steel Corporation | High-strength line-pipe steel having low yield ratio and excellent low-temperature toughness |
| US5755895A (en) * | 1995-02-03 | 1998-05-26 | Nippon Steel Corporation | High strength line pipe steel having low yield ratio and excellent in low temperature toughness |
| EP0747496A1 (en) * | 1995-06-08 | 1996-12-11 | Sollac S.A. | Hot rolled steel sheet with high strength and good deep-drawing properties, containing titanium and process for its manufacturing |
| FR2735147A1 (en) * | 1995-06-08 | 1996-12-13 | Lorraine Laminage | HOT ROLLED STEEL PLATE WITH HIGH STRENGTH AND HIGH THRUST CAPABILITY COMPRISING TITANIUM, AND METHODS OF MANUFACTURE THEREOF. |
| US5759297A (en) * | 1995-06-08 | 1998-06-02 | Sollac | Titanium-containing hot-rolled steel sheet with high strength and high drawability and its manufacturing processes |
| JP2006283187A (en) * | 2005-03-09 | 2006-10-19 | Jfe Steel Kk | Production method of high-strength/high-toughness steel |
| JP2008075107A (en) * | 2006-09-20 | 2008-04-03 | Jfe Steel Kk | Method for manufacturing high-strength/high-toughness steel |
| CN102965574A (en) * | 2012-12-09 | 2013-03-13 | 新余钢铁集团有限公司 | Titanium microalloying hot-rolling thick steel plate with low yield ratio and high strength and production process of steel plate |
| CN105908082A (en) * | 2016-04-01 | 2016-08-31 | 唐山钢铁集团有限责任公司 | Ti-microalloyed Q345B steel plate and production method thereof |
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