JPH02305925A - Production of high-strength hot rolled steel sheet having excellent ductility - Google Patents
Production of high-strength hot rolled steel sheet having excellent ductilityInfo
- Publication number
- JPH02305925A JPH02305925A JP12736789A JP12736789A JPH02305925A JP H02305925 A JPH02305925 A JP H02305925A JP 12736789 A JP12736789 A JP 12736789A JP 12736789 A JP12736789 A JP 12736789A JP H02305925 A JPH02305925 A JP H02305925A
- Authority
- JP
- Japan
- Prior art keywords
- steel sheet
- strength
- hot rolled
- cooling
- cooling rate
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 33
- 239000010959 steel Substances 0.000 title claims abstract description 33
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 238000001816 cooling Methods 0.000 claims abstract description 30
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 5
- 238000005096 rolling process Methods 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 229910052742 iron Inorganic materials 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 6
- 238000004804 winding Methods 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 238000010583 slow cooling Methods 0.000 claims description 4
- 230000000717 retained effect Effects 0.000 claims description 2
- BTCSSZJGUNDROE-UHFFFAOYSA-N gamma-aminobutyric acid Chemical compound NCCCC(O)=O BTCSSZJGUNDROE-UHFFFAOYSA-N 0.000 abstract 1
- 229940084388 gammar Drugs 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 11
- 238000005098 hot rolling Methods 0.000 description 6
- 230000009466 transformation Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
（産業上の利用分野）
本発明は、特にホイールディスク、各種メンバー類を始
めとする自動車用部材或いは建設用材等に使用され、延
性に優れた６ Ｑ ｋｇｆ ／ ｍｍ”以上の強度を有
する高強度熱延鋼板及びその製造方法に関する。
（従来の技術及び解決しようとする課題）近年、自動車
用部材の軽量化のため、高強度で且つ高延性の熱延鋼板
の要求が強いが、従来は、二相（Ｄ ｕａｌ Ｐ ｈａ
ｓｅ）鋼（以下、ｒＤＰ鋼」と称す）、すなわち、フェ
ライト＋マルテンサイト鋼が高強度と高延性を兼備した
鋼として使用されてきた。
しかし、ＤＰｔＲといえども、強度−延性バランスがＴ
ＳＸＥＱ≧２０００を安定して得ることは困難であり、
更なる高強度化、又は複雑な成形を要する部材への適用
が可能な鋼材が求められている。
さて、最近になってγＲのＴＲＩＰ効果を利用した熱延
鋼板がＴＳＸＥＩ２＞２０００を可能にする鋼として注
目されるようになり、多くの提案がなされているが、Ｃ
量が高いため、溶接性に問題があるものが多い。
”
すなわち、例えば、特開昭６０−１８４６６４号ではγ
、を残留させる目的からＣが規制されており、Ｃ含有量
は０．１５％超え、０．８％以下とされている。しかし
ながら、実際にはＣ含有量は０．３８％超えであり、多
量のγ、が得られので延性は良好なものの、溶接が困難
であり、自動車用としては問題がある。
本発明は、か）る事情に鑑みてなされたものであって、
強度−延性バランスに優れると共に溶接性の良好な熱延
鋼板を製造し得る方法を提供することを目的とするもの
である。
（課題を解決するための手段）
前記目的を達成するため、本発明者らは、強度−延性バ
ランスに優れ、且つ溶接性も良好な熱延鋼板が得られる
方策について鋭意検討した。
その結果、Ｃ量を低く抑え、溶接性に悪影響を及ぼさぬ
程度のＳｉとＭｎを添加して成分調整すると共に、熱延
仕上げ温度を規制し、更に熱延後の冷却過程において、
α＋γ２相域で緩冷却を行うことによりＣ濃度の低い軟
質なαを生成させ、且つ未変態オーステナイト中にＣの
濃化を図ることによってγ□を積極的に生成せしめるこ
とにより、可能であることを知見した。また、更にＮｂ
の添加により組織を微細化し、安定したｙＨを微細に分
散させることにより、強度−延性バランスに優れ、より
高強度の鋼板が得られることも知見し、ここに本発明を
完成するに至ったものである。
すなわち１本発明は、Ｃ：０．１５〜０．２５％、Ｓｉ
：２．０〜４．０％及びＭｎ：１．０〜２．０％を含有
し、必要に応じて更にＮｂ：０．０１〜０．０７％及び
Ｃａ：０．００５〜０．０１％の１種又は２種を含有し
、残部が鉄及び不可避的不純物よりなる鋼につき、仕上
げ温度７５０〜９５０℃にて圧延を行った後、冷却速度
２０〜２００℃／ｓｅｃにてＡｒ３〜６００℃まで急冷
し、続いて冷却速度３０℃１５８Ｃ以下にて３〜４Ｑｓ
ａｃの間を緩冷却した後、３００℃〜４５０℃までを冷
却速度２０℃／ｓｅｃ以上で冷却して巻取ることにより
、ＹＲ（残留オーステナイト）を面積率で５〜２０％有
する組織を得ることを特徴とする延性の優れた高強度熱
延鋼板の製造方法を要旨とするものである。
以下、本発明について更に詳細に説明する。
（作用）
まず、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：
Ｃは鋼の強化及びＹＲの安定化に不可欠な元素である。
しかし、０．１５％未満では充分なγ、が得られず、ま
た０、２５％を超えると溶接性が劣化するので、Ｃ量は
０．１５〜０．２５％の範囲とする。
Ｓｉ：
Ｓｉは少ないＣｆで充分なγ、量を得るために非常に重
要な元素である。すなわち、γ→α（フェライト）変態
を促進し、且つα中のＣ′ａ度を低下することによりα
の延性を向上させると共にγ中のＣ濃度を高めて安定化
し、ＹＲを得やすくする効果がある。所要の効果を得る
ためには２．０％以上が必要であるが、４．０％を超え
て含有させてもそれ以上効果が上がらないだけでなく、
溶接性を劣化させるので、Ｓｉ量は２６０〜４．０％の
範囲とする。
Ｍｎ：
Ｍｎは固溶強化元素として強度（ＴＳ）上昇に効果があ
るだけでなく、γを安定化し、独を得るのに重要な元素
である。所要の効果を得るためには１．０％以上が必要
であるが、２．０％を超えて含有させるとバンド状組織
を生成し、加工性が劣化する。したがって、Ｍ ｎ ｆ
ｉは１．０〜２．０％の範囲とする。
本発明ではに記の元素を必須成分とするが、必要に応じ
て以下の元素Ｎｂ、Ｃａの１種又は２種を適量で添加す
ることができる。
Ｎｂ：
Ｎｂは、変態前のγを細粒化するため、熱延板組織を微
細化すると共に、仕上げ圧延後の冷却時に残留するオー
ステナイト中へのＣの濃化を促進するので、ＹＲの生成
を助長する効果がある。また、γ、を微細に分散せしめ
ることにより、強度−延性バランスを向上させるのに重
要な元素である。このような所要の効果を得るには０．
０１％以上が必要であるが、０．０７％を超えて添加し
てもそれ以上効果は上がらないだけでなく、延性（ＥＱ
）の劣化が著しいので、Ｎｂ量は０．０１〜０゜０７％
の範囲とする。
Ｃａ：
Ｃａは加工性の改善、特に局部延性の改善に有効である
。しかし、０．０００５％未満では所要の効果が得られ
ず、また０、０１％を超えて加えてもそれ以上の効果が
なく、逆に介在物となり、加工性を劣化させるので、Ｃ
ａ量は０．０００５〜０．０１％の範囲とする。
次に１本発明により得られる熱延鋼板の組織について述
べる。
本発明で得られる鋼は、加工時のγ２の加工誘起マルテ
ンサイト変態を利用した高強度高延性型鋼板であり、第
１図にγＲ面積率と強度−延性バランス（ＴＳＸＥＱ）
の関係を示すように、所要の特性を得るには、５％以上
のＹＲが必要である。
しかし、本成分系においては、２０％以上のＹＲを得る
のは困難であり、２０％以上のＹＲを得るべく更に合金
を添加すると、伸びフランジ性及び溶接性が劣化する。
したがって、ＹＲの面積率を５〜２０％とする。
か）る組織を有する熱延鋼板を得るための製造条件（熱
延、冷却条件）は以下のとおりである。
仕上げ温度は、γを微細化することによりα変態の促進
及び微細化を図り、強度−延性バランスを向上すると共
に、未変態γを微細１分散させて安定化するために規制
する必要がある。そのためには、第２図に示すように、
９５０℃以下とする必要がある。しかし、仕上げ温度が
７５０℃未満では、加工αが混入するため、強度−延性
バランスが劣化する。したがって、仕上げ温度は７５０
〜９５０℃の範囲とする。
なお、他の熱間圧延条件は特に制限する必要はない。
次に、熱延後の冷却条件の第１として、仕上げ後Ａｒ３
〜６００℃まで（望ましくはフェライト変態ノーズ近傍
まで）を冷却速度２０℃／ｓｅｃ以上にて急冷し、続い
て冷却速度３０℃／ｓｅｃ以下にて３〜４０ｓｅｃの間
緩冷却を行うことにより、α（フェライト）の生成を助
長すると共に、未変態γ中にＣを濃縮させ、安定化を図
る。
ここで、急冷速さが２０℃／ｓｅｃ未満では粗大αの生
成を招くため、強度−延性バランスが劣化するので好ま
しくない。また、冷却速度の上限を２００℃／ｓｅｃと
定めたのは設備上の制約によるものである。
また、上記緩冷却域を３０℃／ｓｅｃを超える冷却速度
又は３ ｓｅｃ未満の冷却時間とすると、αの充分な生
成並びにαからのＣの拡散と未変態γ中へのＣの濃縮が
充分行われないため、強度−延性バランスが劣化するの
で好ましくない。更に、緩冷却時間が４０ｓｅｃを超え
ると、パーライトの生成により未変態γ中の固溶Ｃが消
費され、γ、量が減少するので好ましくない。
緩冷却の後、３００〜４５０℃までを冷却速度２０℃／
ｓｅｃ以上で冷却して巻き取るのは、パーライトの生成
を抑制し、５％以上のＹＲを得るためである。
しかし、冷却速度が２０℃／ｓｅｃ未満ではパーライト
の生成によりＹＲ量が減少する。
また、巻取り温度とＹＲ量の関係は、第３図に示すよう
に、３００°Ｃ未満又は４Ｅ）０℃より高温域ではＹＲ
が所要の５％を得ることができない。
すなわち、３００℃未満では、未変態γがマルテンサイ
トに変態するため、所要のＹＲ量が得られず、また、４
５０°Ｃより高温域では、パーライト、ベイナイト変態
が必要以上に進むため、所要のγ、量が得られない。
以下に本発明の実施例を示す。
（実施例）
第１表に示す化学成分を有する供試鋼に対し、第２表に
示す条件で熱間圧延を行い、冷却して巻取った。なお、
第２表中の各条件記号Ｔ工〜、Ｔ３、ＪＩ、Ｃ工〜Ｃ１
は第４図に示す温度ヒストグラムでの記号に対応してい
る。
得られた熱延鋼板の特性を第２表に併記する。
第２表より明らかなように、本発明例のＮα１〜Ｎα４
は、いずれも適正なγＲ量を有し、良好な強度−延性バ
ランス（ＴＳＸＥＱ）を示している。勿論、Ｃ量が少な
いので溶接性（穴拡げ率）は良好である。
一方、Ｎα５〜Ｎα１１は比較例で、Ｎα５〜Ｎα７は
化学成分範囲が本発明範囲外の例、Ｎα８〜Ｎα１１は
冷却条件が本発明範囲外の例であり、いずれも強度−延
性バランスがＴＳｘＥＱ＜２０００と劣っている。(Industrial Application Field) The present invention is particularly applicable to automobile parts such as wheel discs and various members, construction materials, etc., and is a high-strength material with excellent ductility and a strength of 6 Q kgf/mm" or more. Related to hot-rolled steel sheets and methods of manufacturing the same. (Prior art and problems to be solved) In recent years, there has been a strong demand for hot-rolled steel sheets with high strength and high ductility in order to reduce the weight of automobile parts. Two-phase (Dual P ha
se) steel (hereinafter referred to as "rDP steel"), ie, ferritic + martensitic steel, has been used as a steel that has both high strength and high ductility. However, even with DPtR, the strength-ductility balance is T.
It is difficult to stably obtain SXEQ≧2000,
There is a need for steel materials that have even higher strength or can be applied to members that require complex forming. Recently, hot-rolled steel sheets that utilize the TRIP effect of γR have been attracting attention as a steel that can achieve TSXEI2>2000, and many proposals have been made.
Due to the high amount, there are many problems with weldability.
” That is, for example, in JP-A-60-184664, γ
C is regulated for the purpose of retaining , and the C content is set to be more than 0.15% and less than 0.8%. However, in reality, the C content exceeds 0.38%, and although a large amount of γ is obtained and the ductility is good, it is difficult to weld, which poses a problem for use in automobiles. The present invention has been made in view of the above circumstances, and
The object of the present invention is to provide a method for producing a hot-rolled steel sheet that has an excellent balance of strength and ductility and has good weldability. (Means for Solving the Problems) In order to achieve the above object, the inventors of the present invention have conducted intensive studies on methods for obtaining a hot rolled steel sheet with an excellent strength-ductility balance and good weldability. As a result, we kept the amount of C low, added Si and Mn to an extent that did not adversely affect weldability, adjusted the composition, regulated the hot-rolling finishing temperature, and furthermore, in the cooling process after hot-rolling,
This is possible by slowly cooling in the α + γ two-phase region to generate soft α with a low C concentration, and by actively generating γ□ by enriching C in untransformed austenite. I found out. Furthermore, Nb
It was also discovered that a steel plate with excellent strength-ductility balance and higher strength could be obtained by refining the structure by adding yH and finely dispersing stable yH, which led to the completion of the present invention. It is. That is, 1 the present invention has C: 0.15 to 0.25%, Si
: 2.0 to 4.0% and Mn: 1.0 to 2.0%, and if necessary further Nb: 0.01 to 0.07% and Ca: 0.005 to 0.01%. After rolling at a finishing temperature of 750 to 950°C, Ar 3 to 600°C at a cooling rate of 20 to 200°C/sec for steel containing one or two of the above, with the remainder consisting of iron and unavoidable impurities. 3 to 4 Qs at a cooling rate of 30°C to 158°C or less.
After slowly cooling between ac, cooling from 300 ° C to 450 ° C at a cooling rate of 20 ° C / sec or more and winding, obtain a structure having YR (retained austenite) in an area ratio of 5 to 20%. The gist of the present invention is a method for manufacturing a high-strength hot-rolled steel sheet with excellent ductility. The present invention will be explained in more detail below. (Function) First, the reason for limiting the chemical components in the present invention will be explained. C: C is an essential element for strengthening steel and stabilizing YR. However, if it is less than 0.15%, sufficient γ cannot be obtained, and if it exceeds 0.25%, weldability deteriorates, so the amount of C is set in the range of 0.15 to 0.25%. Si: Si is a very important element in order to obtain a sufficient amount of γ with a small amount of Cf. That is, by promoting the γ→α (ferrite) transformation and lowering the degree of C′a in α, α
It has the effect of improving the ductility of γ and increasing and stabilizing the C concentration in γ, making it easier to obtain YR. In order to obtain the desired effect, 2.0% or more is required, but if the content exceeds 4.0%, not only will the effect not increase any further, but
Since it deteriorates weldability, the amount of Si is set in the range of 260 to 4.0%. Mn: Mn is not only effective in increasing strength (TS) as a solid solution strengthening element, but also is an important element in stabilizing γ and obtaining strength. In order to obtain the desired effect, 1.0% or more is required, but if the content exceeds 2.0%, a band-like structure is generated and workability is deteriorated. Therefore, M n f
i is in the range of 1.0 to 2.0%. In the present invention, the elements listed below are essential components, but if necessary, one or two of the following elements Nb and Ca can be added in appropriate amounts. Nb: Nb refines the grains of γ before transformation, thereby refining the structure of the hot-rolled sheet, and also promotes the concentration of C in the austenite remaining during cooling after finish rolling, which reduces the formation of YR. It has the effect of promoting Further, by finely dispersing γ, it is an important element for improving the strength-ductility balance. 0.0 to get this desired effect.
0.01% or more is required, but adding more than 0.07% not only does not improve the effect any more, but also reduces the ductility (EQ
), the amount of Nb is 0.01 to 0.07%.
The range shall be . Ca: Ca is effective in improving workability, especially local ductility. However, if it is less than 0.0005%, the desired effect cannot be obtained, and if it is added in excess of 0.01%, there is no further effect, and on the contrary, it becomes inclusions and deteriorates workability.
The amount of a is in the range of 0.0005 to 0.01%. Next, the structure of the hot rolled steel sheet obtained by the present invention will be described. The steel obtained by the present invention is a high-strength, high-ductility type steel plate that utilizes the deformation-induced martensitic transformation of γ2 during processing, and Fig. 1 shows the γR area ratio and strength-ductility balance (TSXEQ).
As shown in the relationship below, YR of 5% or more is required to obtain the desired properties. However, in this component system, it is difficult to obtain a YR of 20% or more, and if an alloy is further added to obtain a YR of 20% or more, stretch flangeability and weldability deteriorate. Therefore, the area ratio of YR is set to 5 to 20%. The manufacturing conditions (hot rolling and cooling conditions) for obtaining a hot rolled steel sheet having the above structure are as follows. The finishing temperature needs to be regulated in order to promote and refine α transformation by making γ fine, improve the strength-ductility balance, and stabilize untransformed γ by finely dispersing it. To do this, as shown in Figure 2,
It is necessary to keep the temperature below 950°C. However, if the finishing temperature is less than 750°C, the strength-ductility balance deteriorates because processing α is mixed. Therefore, the finishing temperature is 750
The temperature should be in the range of ~950°C. Note that there is no need to particularly limit other hot rolling conditions. Next, as the first cooling condition after hot rolling, Ar3
By rapidly cooling to ~600°C (preferably to the vicinity of the ferrite transformation nose) at a cooling rate of 20°C/sec or more, and then slowly cooling for 3 to 40 seconds at a cooling rate of 30°C/sec or less, α (ferrite) and concentrates C in untransformed γ to stabilize it. Here, if the quenching rate is less than 20° C./sec, it is not preferable because coarse α is generated and the strength-ductility balance is deteriorated. Furthermore, the upper limit of the cooling rate was set at 200° C./sec due to equipment constraints. Furthermore, when the above-mentioned slow cooling region is set to a cooling rate exceeding 30°C/sec or a cooling time of less than 3 sec, sufficient generation of α, diffusion of C from α, and concentration of C into untransformed γ are achieved. This is not preferable because the strength-ductility balance deteriorates. Furthermore, if the slow cooling time exceeds 40 seconds, the solid solution C in the untransformed γ is consumed by the production of pearlite, and the amount of γ decreases, which is not preferable. After slow cooling, from 300 to 450℃ at a cooling rate of 20℃/
The reason for cooling and winding for more than sec is to suppress the formation of pearlite and obtain YR of 5% or more. However, if the cooling rate is less than 20° C./sec, the amount of YR decreases due to the formation of pearlite. Furthermore, the relationship between the winding temperature and the amount of YR is as shown in Figure 3.
cannot get the required 5%. That is, at temperatures below 300°C, untransformed γ transforms into martensite, making it impossible to obtain the required amount of YR;
At temperatures higher than 50°C, pearlite and bainite transformations proceed more than necessary, making it impossible to obtain the required γ and amount. Examples of the present invention are shown below. (Example) Test steel having the chemical components shown in Table 1 was hot rolled under the conditions shown in Table 2, cooled, and coiled. In addition,
Each condition symbol in Table 2 T-, T3, JI, C-C1
correspond to the symbols in the temperature histogram shown in FIG. The properties of the obtained hot rolled steel sheets are also listed in Table 2. As is clear from Table 2, Nα1 to Nα4 of the examples of the present invention
All have appropriate γR amounts and exhibit good strength-ductility balance (TSXEQ). Of course, since the amount of C is small, weldability (hole expansion rate) is good. On the other hand, Nα5 to Nα11 are comparative examples, Nα5 to Nα7 are examples in which the chemical composition range is outside the range of the present invention, and Nα8 to Nα11 are examples in which the cooling conditions are outside the range of the present invention, and in all cases, the strength-ductility balance is TSxEQ< It is inferior to 2000.
（発明の効果）
以上詳述したように、本発明によれば、特に低いＣ含有
量により、γＲを多量に生成させることができるため１
強度−延性バランス（ＴＳＸＥＩ２）が優れていると共
に、溶接性も良好な熱延鋼板を容易に得ることができる
。(Effects of the Invention) As detailed above, according to the present invention, it is possible to generate a large amount of γR with a particularly low C content.
A hot-rolled steel sheet having an excellent strength-ductility balance (TSXEI2) and good weldability can be easily obtained.
第１図はγＲ面積率と強度−延性バランス（ＴＳＸＥｎ
）の関係を示す図。
第２図は強度−延性バランス（ＴＳＸＥｎ）に及ぼす仕
上げ温度の影響を示す図、
第３図は７８面積率に及ぼす巻取り温度の影響を示す図
。
第４図は熱間圧延における温度ヒストグラムを示す図で
ある。
特許出願人 株式会社神戸製鋼所
代理人弁理士 中 村 尚
第１図
第２図Figure 1 shows the γR area ratio and strength-ductility balance (TSXEn
) is a diagram showing the relationship between FIG. 2 is a diagram showing the influence of finishing temperature on strength-ductility balance (TSXEn), and FIG. 3 is a diagram showing the influence of winding temperature on 78 area ratio. FIG. 4 is a diagram showing a temperature histogram during hot rolling. Patent applicant Hisashi Nakamura, patent attorney representing Kobe Steel, Ltd. Figure 1 Figure 2
Claims (3)
５％、Ｓｉ：２．０〜４．０％及びＭｎ：１．０〜２．
０％を含有し、残部が鉄及び不可避的不純物よりなる鋼
につき、仕上げ温度７５０〜９５０℃にて圧延を行った
後、冷却速度２０〜２００℃／ｓｅｃにてＡｒ＿３〜６
００℃まで急冷し、続いて冷却速度３０℃／ｓｅｃ以下
にて３〜４０ｓｅｃの間を緩冷却した後、３００℃〜４
５０℃までを冷却速度２０℃／ｓｅｃ以上で冷却して巻
取ることにより、γ＿Ｒ（残留オーステナイト）を面積
率で５〜２０％有する組織を得ることを特徴とする延性
の優れた高強度熱延鋼板の製造方法。(1) In weight% (the same applies hereinafter), C: 0.15 to 0.2
5%, Si: 2.0-4.0% and Mn: 1.0-2.
After rolling at a finishing temperature of 750 to 950°C, Ar_3 to 6 is applied at a cooling rate of 20 to 200°C/sec for steel containing 0% and the remainder consisting of iron and unavoidable impurities.
After rapid cooling to 00℃, followed by slow cooling for 3 to 40 seconds at a cooling rate of 30℃/sec or less, 300℃ to 4
A high-strength hot rolled sheet with excellent ductility characterized by obtaining a structure having γ_R (retained austenite) in an area ratio of 5 to 20% by cooling to 50°C at a cooling rate of 20°C/sec or more and winding. Method of manufacturing steel plates.
するものである請求項１に記載の方法。(2) The method according to claim 1, wherein the steel further contains Nb: 0.01 to 0.07%.
有するものである請求項１又は２に記載の方法。(3) The method according to claim 1 or 2, wherein the steel further contains Ca: 0.005 to 0.01%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1127367A JP2559272B2 (en) | 1989-05-20 | 1989-05-20 | Method for producing high strength hot rolled steel sheet with excellent ductility |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1127367A JP2559272B2 (en) | 1989-05-20 | 1989-05-20 | Method for producing high strength hot rolled steel sheet with excellent ductility |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02305925A true JPH02305925A (en) | 1990-12-19 |
| JP2559272B2 JP2559272B2 (en) | 1996-12-04 |
Family
ID=14958214
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1127367A Expired - Fee Related JP2559272B2 (en) | 1989-05-20 | 1989-05-20 | Method for producing high strength hot rolled steel sheet with excellent ductility |
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| Country | Link |
|---|---|
| JP (1) | JP2559272B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04341523A (en) * | 1991-05-17 | 1992-11-27 | Kobe Steel Ltd | Production of hot rolled high strength steel plate excellent in ductility and workability |
| KR100450613B1 (en) * | 1999-12-28 | 2004-09-30 | 주식회사 포스코 | A method for manufacturing wire rod for thick plate welding with superior impact toughness |
| KR100711476B1 (en) * | 2005-12-26 | 2007-04-24 | 주식회사 포스코 | Method for manufacturing high strength hot rolled steel sheet having excellent formability |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6479345A (en) * | 1987-06-03 | 1989-03-24 | Nippon Steel Corp | High-strength hot rolled steel plate excellent in workability and its production |
-
1989
- 1989-05-20 JP JP1127367A patent/JP2559272B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6479345A (en) * | 1987-06-03 | 1989-03-24 | Nippon Steel Corp | High-strength hot rolled steel plate excellent in workability and its production |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04341523A (en) * | 1991-05-17 | 1992-11-27 | Kobe Steel Ltd | Production of hot rolled high strength steel plate excellent in ductility and workability |
| KR100450613B1 (en) * | 1999-12-28 | 2004-09-30 | 주식회사 포스코 | A method for manufacturing wire rod for thick plate welding with superior impact toughness |
| KR100711476B1 (en) * | 2005-12-26 | 2007-04-24 | 주식회사 포스코 | Method for manufacturing high strength hot rolled steel sheet having excellent formability |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2559272B2 (en) | 1996-12-04 |
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