JP2022550329A - Double phase steel with high hole expandability and method for producing the same - Google Patents
Double phase steel with high hole expandability and method for producing the same Download PDFInfo
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- JP2022550329A JP2022550329A JP2022519055A JP2022519055A JP2022550329A JP 2022550329 A JP2022550329 A JP 2022550329A JP 2022519055 A JP2022519055 A JP 2022519055A JP 2022519055 A JP2022519055 A JP 2022519055A JP 2022550329 A JP2022550329 A JP 2022550329A
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 31
- 229910000831 Steel Inorganic materials 0.000 title claims description 62
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- 238000010438 heat treatment Methods 0.000 claims abstract description 9
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- 238000005096 rolling process Methods 0.000 claims description 35
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
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- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0242—Flattening; Dressing; Flexing
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- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
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Abstract
本発明は、微細組織がフェライト＋ベイナイトであり、以下の化学元素質量百分率を有する高穴拡げ性複相鋼を開示した：Ｃ：０．０６～０．０９％、Ｓｉ：０．０５～０．５％、Ａｌ：０．０２～０．１％、Ｍｎ：１．５～１．８％、Ｃｒ：０．３～０．６％、Ｎｂ≦０．０３％、Ｔｉ：０．０５～０．１２％、残部はＦｅ及び他の不可避不純物である。また、本発明は、以下の工程を含む前記の高穴拡げ性複相鋼の製造方法も開示した：（１）製錬・鋳造；（２）加熱；（３）熱間圧延；（４）脱リン；（５）層流冷却：緩和時間を０～８ｓに制御し、層流冷却速度を４０～７０℃／ｓに制御する；（６）巻取り；（７）平坦化；（８）酸洗。該高穴拡げ性複相鋼は、良好な穴拡げ性と良好な可塑性を両立させることができる。The present invention discloses a high hole expandability dual phase steel with a ferrite + bainite microstructure and the following chemical element mass percentages: C: 0.06-0.09%, Si: 0.05-0 .5%, Al: 0.02-0.1%, Mn: 1.5-1.8%, Cr: 0.3-0.6%, Nb≤0.03%, Ti: 0.05- 0.12%, the balance being Fe and other unavoidable impurities. The present invention also discloses a method for producing the high-hole-expandable dual-phase steel, comprising the following steps: (1) smelting and casting; (2) heating; (3) hot rolling; (5) laminar cooling: controlling the relaxation time to 0-8 s and controlling the laminar cooling rate to 40-70° C./s; (6) winding; (7) flattening; (8) Pickling. The high hole expandability dual phase steel can achieve both good hole expandability and good plasticity.
Description
本発明は鋼種及びその製造方法に関し、特に複相鋼及びその製造方法に関する。 TECHNICAL FIELD The present invention relates to a steel grade and its manufacturing method, and more particularly to a dual phase steel and its manufacturing method.
自動車の高強度・軽量化に伴い、コントロールアーム、タイロッド、スプリングシートなどの自動車シャーシ部品に８０ｋｇレベルの熱延酸洗鋼板が使用されるモデルは、ますます増えている。例えば、コントロールアームなどの自動車シャーシ部品は、その成形過程にスタンピング、フランジング、穴拡げなどが含まれるため、強度や伸びだけでなく、穴拡げ性に対してもある程度の要求がある。 With the increasing strength and weight reduction of automobiles, more and more models are using 80kg level hot-rolled pickled steel sheets for automobile chassis parts such as control arms, tie rods and spring seats. For example, automobile chassis parts such as control arms require not only strength and elongation, but also hole expandability to some extent, because the molding process includes stamping, flanging, hole expansion, and the like.
公開番号がＣＮ１０３６０２８９５Ａで、公開日が２０１４年２月２６日で、名称が「引張強度７８０ＭＰａレベルの高穴拡げ性鋼板及びその製造方法」の中国特許文献には、抗引張強度７８０ＭＰａレベルの高穴拡げ性鋼板及びその製造方法が開示されたが、そのＳｉ含有量が０．５～１．５％と高く、鉄橄欖石（２ＦｅＯ－ＳｉＯ２）酸化スケールが形成しやすく且つ除去しにくく、高レベルの表面を有する帯鋼を獲得することが困難であった。また、鋼板表面の赤スケールの制御が難しいので、熱間圧延温度測定過程において正確に測定することが難しくなり、製品の不安定な性能に繋がる。 A Chinese patent document with a publication number of CN103602895A, a publication date of February 26, 2014, and a title of "High-hole expandable steel sheet with tensile strength of 780 MPa level and method for manufacturing the same" describes high-hole with tensile strength of 780 MPa level An expandable steel sheet and a method for producing the same have been disclosed, but the Si content thereof is as high as 0.5-1.5%, and the olivine (2FeO—SiO 2 ) oxide scale is easy to form and difficult to remove. It was difficult to obtain a strip with a level surface. In addition, since it is difficult to control the red scale on the surface of the steel sheet, it becomes difficult to accurately measure the temperature during the hot rolling process, leading to unstable performance of the product.
公開番号がＣＮ１０８５７０６０４Ａで、公開日が２０１８年９月２５日で、名称が「７８０ＭＰａレベルの熱延酸洗高穴拡げ性鋼帯及びその生産方法」の中国特許文献には、７８０ＭＰａレベルの熱延酸洗高穴拡げ性鋼帯及びその生産方法が開示されたが、その成分Ａｌ含有量が０．２～０．６％と高く、連続鋳造の過程において酸化されやすいと共に、それに適用されるのは三段冷却の手段であり、生産の安定性が低い。 A Chinese patent document with a publication number of CN108570604A, a publication date of September 25, 2018, and a title of "780 MPa level hot rolled pickled high hole expandable steel strip and its production method" discloses a 780 MPa level hot rolled A pickled high hole expandable steel strip and its production method have been disclosed. is a means of three-stage cooling, and the production stability is low.
公開号がＣＮ１０５４８３５４５Ａで、公開日が２０１６年４月１３日で、名称が「８００ＭＰａレベルの熱延高穴拡げ性鋼板及びその製造方法」の中国特許文献には、８００ＭＰａレベルの熱延高穴拡げ性鋼板及びその製造方法が開示されたが、その成分に０．２～１．０％のＳｉが含有され、Ｓｉ含有量が比較的に高く、表面で赤スケールが形成しやすく、表面及び巻取り温度の制御に不利である。また、０．０３～０．０８％のＮｂが含有され、Ｎｂ含有量も比較的に高く、コストが高く、且つ圧延後に段階的冷却が必要であり、冷却プロセスが複雑である。 A Chinese patent document with publication number CN105483545A, publication date April 13, 2016 and titled "800 MPa level hot rolled high hole expandable steel sheet and manufacturing method thereof" describes 800 MPa level hot rolled high hole expandable A high-strength steel sheet and a method for producing the same have been disclosed, but the composition contains 0.2-1.0% Si, the Si content is relatively high, the surface is easy to form red scale, and the surface and winding It is disadvantageous in controlling the take-out temperature. In addition, it contains 0.03-0.08% Nb, the Nb content is also relatively high, the cost is high, and the cooling process is complicated, requiring stepwise cooling after rolling.
従来技術では、材料の強度が高いほど、材料の長さと幅の安定性を制御することが難しくなる。これにより、穴拡げ性と冷間成形性が共に良好で、且つ安定的に製造・生産できる高穴拡げ性複相鋼を得ることが望まれている。 In the prior art, the stronger the material, the more difficult it is to control the length and width stability of the material. Accordingly, it is desired to obtain a highly hole-expandable dual-phase steel that has both good hole expandability and cold formability and that can be stably manufactured and produced.
本発明の一つの目的は、良好な穴拡げ性と良好な可塑性を両立させることができ、且つ該高穴拡げ性複相鋼の２相はフェライトとベイナイトであるので、従来の材料である低合金高強度鋼やフェライト・マルテンサイト二相鋼に比べて硬度差が小さいことにより、その穴拡げ性と冷間成形性が良好となる高穴拡げ性複相鋼を提供することである。 One object of the present invention is to achieve both good hole expandability and good plasticity, and to achieve the two phases of the high hole expandability dual-phase steel, which are ferrite and bainite. To provide a high hole expandability dual-phase steel which has good hole expandability and cold formability due to a smaller difference in hardness than alloyed high-strength steel and ferrite-martensite dual-phase steel.
上記目的を達成するために、本発明は、微細組織がフェライト＋ベイナイトであり、以下の化学元素質量百分率を有する高穴拡げ性複相鋼を提供する。 In order to achieve the above object, the present invention provides a high hole expandability dual phase steel having a microstructure of ferrite + bainite and having the following mass percentages of chemical elements.
Ｃ：０．０６～０．０９％、Ｓｉ：０．０５～０．５％、Ａｌ：０．０２～０．１％、Ｍｎ：１．５～１．８％、Ｃｒ：０．３～０．６％、Ｎｂ≦０．０３％、Ｔｉ：０．０５～０．１２％、残部はＦｅ及び他の不可避不純物である。 C: 0.06-0.09%, Si: 0.05-0.5%, Al: 0.02-0.1%, Mn: 1.5-1.8%, Cr: 0.3- 0.6%, Nb≦0.03%, Ti: 0.05-0.12%, the balance being Fe and other unavoidable impurities.
本発明に係る高穴拡げ性複相鋼において、各化学元素の設計原理は以下のようである。
Ｃ：本発明にかかる高穴拡げ性複相鋼において、炭素含有量のレベルが鋼板の引張強度レベルを大きく左右し、炭素が固溶強化及び十分な析出強化相の形成に関与し、鋼の強度を確保するが、炭素の質量百分率が高くなると、炭化物粒子が粗大化して穴拡げ性に不利になり、逆に炭素が低すぎると、鋼板の強度の低下に繋がるということを考慮すると、鋼種の強度で高穴拡げ性を確保すると共に、良好な成形性と溶接性をもたらすために、本発明に係る技術方案において、Ｃの質量百分率は０．０６～０．０９％に制御される。
In the high hole expansibility dual phase steel according to the present invention, the design principle of each chemical element is as follows.
C: In the high hole expansibility dual phase steel according to the present invention, the level of carbon content greatly affects the tensile strength level of the steel sheet, carbon participates in solid solution strengthening and formation of a sufficient precipitation strengthening phase, Although strength is ensured, if the mass percentage of carbon is high, the carbide particles become coarse and disadvantageous for hole expandability. The mass percentage of C is controlled to 0.06 to 0.09% in the technical solution according to the present invention in order to ensure high hole expansibility with the strength of , and to bring about good formability and weldability.
Ｓｉ：本発明にかかる高穴拡げ性複相鋼において、ケイ素は固溶強化の作用を奏して鋼板の強度を向上させると共に、ケイ素の添加により、加工硬化速度及び所定の強度での均一伸びと全伸びを向上させることができ、鋼板の伸びの改善に寄与する。さらに、ケイ素は炭化物の析出を阻止し、パーライト相の出現を低減させることもできる。しかし、鋼にケイ素を含ませると、鋼板の表面は鉄橄欖石（２ＦｅＯ－ＳｉＯ２）酸化スケールの表面欠陥が形成する傾向にあり、表面品質に悪影響を与える。また、赤スケールの出現は、熱間圧延過程での温度制御に不利であるため、最終的に製品性能の安定性に不利な影響を与える。以上のことを踏まえ、本発明にかかる高穴拡げ性複相鋼において、ケイ素の質量百分率は０．０５～０．５％に制御される。 Si: In the high-hole expandable double-phase steel according to the present invention, silicon exerts a solid-solution strengthening action to improve the strength of the steel sheet, and the addition of silicon improves the work hardening rate and uniform elongation at a predetermined strength. It can improve the total elongation and contributes to the improvement of the elongation of the steel sheet. In addition, silicon can also inhibit carbide precipitation and reduce the appearance of pearlite phase. However, when the steel contains silicon, the surface of the steel sheet tends to form surface defects of olivine (2FeO—SiO 2 ) oxide scale, which adversely affects the surface quality. In addition, the appearance of red scale is disadvantageous to temperature control in the hot rolling process, which ultimately adversely affects the stability of product performance. Based on the above, the mass percentage of silicon is controlled to 0.05 to 0.5% in the high hole expandability dual phase steel according to the present invention.
Ａｌ：本発明にかかる高穴拡げ性複相鋼において、Ａｌは鋼の脱酸元素であり、鋼における酸化物の介在を低減して鋼を清浄化し、鋼板の成形性の向上に有利であるが、アルミニウムの質量百分率が高くなると、酸化が発生し、さらに連続鋳造生産に影響を及ぼす。以上のことを踏まえ、本発明にかかる高穴拡げ性複相鋼において、Ａｌの質量百分率は０．０２～０．１％に制御される。 Al: In the high hole expansibility dual-phase steel according to the present invention, Al is a deoxidizing element for the steel, and is advantageous for improving the formability of the steel sheet by reducing the presence of oxides in the steel, purifying the steel. However, at higher mass percentages of aluminum, oxidation occurs, further affecting continuous casting production. Based on the above, in the high hole expandability dual phase steel according to the present invention, the mass percentage of Al is controlled to 0.02 to 0.1%.
Ｍｎ：本発明にかかる高穴拡げ性複相鋼において、マンガンは固溶強化元素であり、マンガンの質量百分率が低くなると、強度が不足するが、マンガンの質量百分率が高くなると、鋼板の可塑性が低下する。また、マンガンはパーライト変態を遅延させ、鋼の焼入れ性を向上させ、ベイナイト変態温度を下げ、鋼の下部組織の構造を微細化させ、且つラス下部組織の獲得を確保し、製品の引張強度を確保する前提で、良好な成形性をもたらす。以上のことを踏まえ、本発明にかかる高穴拡げ性複相鋼において、Ｍｎの質量百分率は１．５～１．８％に制御される。 Mn: In the high hole-expandability dual-phase steel according to the present invention, manganese is a solid-solution strengthening element, and when the mass percentage of manganese decreases, the strength becomes insufficient. descend. In addition, manganese can delay the pearlite transformation, improve the hardenability of steel, lower the bainite transformation temperature, refine the structure of the steel substructure, ensure the acquisition of the lath substructure, and increase the tensile strength of the product. On the premise of ensuring, it leads to good moldability. Based on the above, the mass percentage of Mn is controlled to 1.5 to 1.8% in the high hole expandability dual phase steel according to the present invention.
Ｃｒ：本発明にかかる高穴拡げ性複相鋼において、クロムは、ＣＣＴ曲線におけるパーライトとフェライトの潜伏期を延ばし、パーライトとフェライトの形成を抑制し、ベイナイト組織の形成に有利し、最終的に強度と穴拡げ率の向上に有利であるが、クロムの質量百分率が０．１５％未満であると、ＣＣＴ曲線への影響は顕著ではないが、Ｃｒの質量百分率が高くなると、コスト高に繋がる。以上のことを踏まえ、本発明にかかる高穴拡げ性複相鋼において、Ｃｒの質量百分率は０．３～０．６％に制御される。 Cr: In the high-hole expandability dual-phase steel according to the present invention, chromium extends the latency period of pearlite and ferrite in the CCT curve, suppresses the formation of pearlite and ferrite, favors the formation of bainite structure, and finally increases the strength. When the mass percentage of chromium is less than 0.15%, the effect on the CCT curve is not significant, but the higher the mass percentage of Cr, the higher the cost. Based on the above, the mass percentage of Cr is controlled to 0.3 to 0.6% in the high hole expandability dual phase steel according to the present invention.
Ｎｂ：本発明にかかる高穴拡げ性複相鋼において、ニオブは重要な析出強化元素と細粒強化元素の一つであり、圧延終了後の冷却中または巻取り後で微細な析出物の形で存在し、析出強化によって強度を向上させる。また、ニオブの存在は、結晶粒の微細化、強度や靭性の向上に有利であると共に、フェライトとベイナイトのマトリックス間の強度差を低減させることにより、穴拡げ率の向上にも有利であるが、Ｎｂの質量百分率が０．０３％を超えると、Ｎｂによる強化効果は飽和に近づき、且つコストが高くなる。よって、本発明にかかる高穴拡げ性複相鋼において、Ｎｂの質量百分率はＮｂ≦０．０３％に制御される。Ｎｂの質量百分率が０．０１５％未満であると、ＮｂＣの析出が不十分となり、析出強化の目的が達成しにくいことを考慮すると、いくつかの好ましい実施形態において、Ｎｂの質量百分率は０．０１５～０．０３％に好ましく設定しても良い。 Nb: Niobium is one of the important precipitation-strengthening elements and fine-grain-strengthening elements in the high-hole expandability double-phase steel according to the present invention, and forms fine precipitates during cooling after rolling or after winding. and improves strength by precipitation strengthening. In addition, the presence of niobium is advantageous for refining crystal grains and improving strength and toughness, and is also advantageous for improving the hole expansion rate by reducing the strength difference between the matrix of ferrite and bainite. , the mass percentage of Nb exceeds 0.03%, the reinforcing effect of Nb approaches saturation and the cost increases. Therefore, in the high-hole expandability dual-phase steel according to the present invention, the mass percentage of Nb is controlled to Nb≦0.03%. Considering that if the mass percentage of Nb is less than 0.015%, the precipitation of NbC is insufficient and the purpose of precipitation strengthening is difficult to achieve, in some preferred embodiments, the mass percentage of Nb is 0.015%. It may be preferably set to 015 to 0.03%.
Ｔｉ：本発明にかかる高穴拡げ性複相鋼において、チタンは重要な析出強化元素と細粒強化元素の一つであり、本願におけるチタンは以下の２つの役割を果たす：１つ目は鋼中の不純物元素の窒素と結合してＴｉＮを形成することであり、これは、鋼におけるフリーな窒素原子が鋼の衝撃靭性に不利であるので、微量のチタンの添加によりフリーな窒素を固定化し、穴拡げ性の発揮及び衝撃靭性の向上に有利であるからである；２つ目はニオブと協力してオーステナイト結晶粒微細化及び析出強化に最適の役割を果たすことである。しかし、本願において、Ｔｉの質量百分率が多すぎると、サイズが大きなＴｉＮが形成しやすく、鋼の衝撃靭性に不利であるため、望ましくない。よって、本発明にかかる高穴拡げ性複相鋼において、Ｔｉの質量百分率はＴｉ：０．０５～０．１２％に制御される。 Ti: Titanium is one of the important precipitation strengthening elements and fine grain strengthening elements in the high-hole expandability double-phase steel according to the present invention, and titanium in the present application plays the following two roles: the first is steel It is to combine with the nitrogen of the impurity element in the steel to form TiN. This is because the free nitrogen atoms in the steel are unfavorable to the impact toughness of the steel, so the addition of a small amount of titanium fixes the free nitrogen. Second, it plays an optimal role in austenite grain refinement and precipitation strengthening in cooperation with niobium. However, in the present application, if the mass percentage of Ti is too high, TiN having a large size tends to be formed, which is disadvantageous to the impact toughness of the steel, which is undesirable. Therefore, in the high-hole expandability dual-phase steel according to the present invention, the mass percentage of Ti is controlled to Ti: 0.05 to 0.12%.
さらに、本発明にかかる高穴拡げ性複相鋼において、Ｎｂ元素の含有量は０．０１５～０．０３％である。 Furthermore, in the high-hole-expansion dual-phase steel according to the present invention, the content of Nb element is 0.015 to 0.03%.
さらに、本発明にかかる高穴拡げ性複相鋼において、他の不可避不純物では、Ｐ≦０．０３％、Ｓ≦０．０２％、Ｎ≦０．００５％である。 Furthermore, in the high-hole-expanding dual-phase steel according to the present invention, other unavoidable impurities are P≦0.03%, S≦0.02%, and N≦0.005%.
上記形態において、不可避不純物元素は可能な限り低く制御するべきであるが、コスト管理やプロセスの制限などを考慮すると、Ｐ≦０．０３％、Ｓ≦０．０２％、Ｎ≦０．００５％と制御しても良い。ただし、Ｎの質量百分率がＮ≦０．００５％に制御されるのは、窒素が高温条件下でチタンと反応してＴｉＮ粒子として析出し、大きすぎるＴｉＮ粒子が鋼板の局所変形マイクロクラックになり、最終的に穴拡げ率に影響を及ぼすので、鋼における窒素含有量を制御しなければならないからである。 In the above embodiment, the amount of unavoidable impurity elements should be controlled as low as possible. and control. However, the reason why the mass percentage of N is controlled to N ≤ 0.005% is that nitrogen reacts with titanium under high temperature conditions and precipitates as TiN particles, and excessively large TiN particles become local deformation microcracks in the steel sheet. , because the nitrogen content in the steel must be controlled, as it ultimately affects the hole expansion ratio.
Ｐについて、Ｐの質量百分率がＰ≦０．０３％に制御されるのは、鋼におけるリンは通常、フェライト中に固溶して鋼の靭性を低下させるが、高レベルのリンは溶接性に不利であると共に、リンは結晶粒界に偏在して帯鋼の穴拡げ性に不利であるので、リン含有量はできるだけ低減させるべきだからである。 Regarding P, the mass percentage of P is controlled to P≦0.03% because phosphorus in steel usually dissolves in ferrite and reduces the toughness of steel, but a high level of phosphorus affects weldability. This is because the phosphorus content should be reduced as much as possible because it is disadvantageous and is unevenly distributed at grain boundaries, which is disadvantageous to the hole expandability of the strip steel.
上記形態において、Ｓの質量百分率がＳ≦０．０２％に制御されるのは、硫の含有量及び硫化物の形態が成形性に影響する主要な要因であり、硫化物の量が多くてサイズが大きくなるほど、穴拡げ性に不利になるからである。 In the above form, the mass percentage of S is controlled to S≦0.02% because the sulfur content and the form of sulfide are the main factors affecting moldability. This is because the larger the size, the more disadvantageous the hole expansibility.
さらに、本発明にかかる高穴拡げ性複相鋼において、その化学元素質量百分率含有量は、下記の各式の少なくとも一つを満たす：
０．２％≦Ｃｒ－０．５（Ｓｉ＋Ａｌ）≦０．４２％；
０．０８％≦３．３Ｎｂ＋Ｔｉ≦０．２０％。
Further, in the high-hole-expanding dual-phase steel according to the present invention, the chemical element mass percentage content satisfies at least one of the following expressions:
0.2%≦Cr−0.5(Si+Al)≦0.42%;
0.08%≤3.3Nb+Ti≤0.20%.
上記形態において、０．２％≦Ｃｒ－０．５（Ｓｉ＋Ａｌ）≦０．４２％と制御されることにより、パーライトとフェライトの変態領域が右にシフトし、パーライトとフェライトの変態が遅延され、ベイナイト相の形成に有利であることから、高強度と高穴拡げ性の目的を実現できる。 In the above embodiment, by controlling 0.2% ≤ Cr-0.5 (Si + Al) ≤ 0.42%, the transformation region between pearlite and ferrite shifts to the right, and the transformation between pearlite and ferrite is delayed, Since it is advantageous for the formation of the bainite phase, the purpose of high strength and high hole expandability can be achieved.
また、本技術方案において、Ｎｂ、Ｔｉの質量百分率が０．０８％≦３．３Ｎｂ＋Ｔｉ≦０．２０％を満たすように制御されることにより、析出強化が約１００～２００ＭＰａに制御されると共に、高レベルチタン成分の設計を採用する場合に、ニオブを添加せずに、本願に要求される高穴拡げ性と高可塑性の目的を実現できると同時に、コストダウンの目的も実現できる。 In addition, in this technical plan, the mass percentage of Nb and Ti is controlled to satisfy 0.08% ≤ 3.3Nb + Ti ≤ 0.20%, thereby controlling precipitation strengthening to about 100 to 200 MPa, When adopting a high-level titanium component design, it is possible to achieve the objectives of high hole expandability and high plasticity required by the present application without adding niobium, and at the same time achieve the objective of cost reduction.
さらに、本発明にかかる高穴拡げ性複相鋼において、その微細組織には、（Ｔｉ，Ｎｂ）Ｃ及びＮｂＮを含む微量合金析出物がある。 Further, in the high-hole-expansion dual-phase steel according to the present invention, the microstructure has minor alloy precipitates containing (Ti,Nb)C and NbN.
さらに、本発明にかかる高穴拡げ性複相鋼において、その引張強度及び化学元素質量百分率含有量は、以下の式を満たす：
引張強度Ｒｍ＝３４３＋７８９×Ｃ＋１７０×Ｓｉ＋１３２×Ｍｎ＋１９５×Ｃｒ＋８４３×（Ｎｂ＋Ｔｉ）－２０７×Ａｌ、引張強度Ｒｍの次元はＭＰａである。
Furthermore, in the high-hole-expansion double-phase steel according to the present invention, its tensile strength and chemical element mass percentage content satisfy the following formulae:
Tensile strength Rm=343+789*C+170*Si+132*Mn+195*Cr+843*(Nb+Ti)-207*Al, the dimension of tensile strength Rm is MPa.
本技術方案において、上記の式と本願の化学元素成分配合により、引張強度Ｒｍは通常７９０～８５０ＭＰａである。 In this technical solution, the tensile strength Rm is generally 790-850 MPa according to the above formula and the composition of chemical elements in the present application.
さらに、本発明にかかる高穴拡げ性複相鋼において、その横方向引張強度が≧７８０ＭＰａで、降伏強度が≧７００ＭＰａで、伸びＡ５０が≧１５％で、抜き穴の穴拡げ率が≧５０％である。 Further, in the high-hole-expandable dual-phase steel according to the present invention, its transverse tensile strength is ≧780 MPa, the yield strength is ≧700 MPa, the elongation A50 is ≧15%, and the hole expansion ratio of the punched hole is ≧50. %.
好ましくは、本発明にかかる高穴拡げ性複相鋼において、抜き穴の穴拡げ率が≧７０％である。 Preferably, in the high hole-expandability dual-phase steel according to the present invention, the hole expansion ratio of punched holes is ≧70%.
好ましくは、本発明にかかる高穴拡げ性複相鋼において、降伏強度が≧７３０ＭＰａである。 Preferably, the high-hole-expandability dual-phase steel according to the present invention has a yield strength of ≧730 MPa.
好ましくは、本発明にかかる高穴拡げ性複相鋼において、横方向引張強度が≧８０００ＭＰａである。 Preferably, in the high-hole-expandability dual-phase steel according to the present invention, the lateral tensile strength is ≧8000 MPa.
好ましくは、本発明にかかる高穴拡げ性複相鋼において、その横方向引張強度が≧８００ＭＰａで、降伏強度が≧７３０ＭＰａで、伸びＡ５０が≧１５％で、抜き穴の穴拡げ率が≧７０％である。 Preferably, in the high hole-expansion double-phase steel according to the present invention, its transverse tensile strength is ≧800 MPa, the yield strength is ≧730 MPa, the elongation A50 is ≧15%, and the hole expansion ratio of the punched hole is ≧ 70%.
相応に、本発明のもう一つの目的は、穴拡げ性と冷間成形性が良好な高穴拡げ性複相鋼を獲得できる前記の高穴拡げ性複相鋼の製造方法を提供することである。 Correspondingly, another object of the present invention is to provide a method for producing the above-mentioned high hole expandability dual phase steel that can obtain the high hole expandability dual phase steel with good hole expandability and cold formability. be.
上記発明目的を達成するために、本発明によって提供される前記の高穴拡げ性複相鋼の製造方法は、以下の工程を含む：
（１）製錬・鋳造；
（２）加熱；
（３）熱間圧延：総圧下率を≧８０％に制御し、粗圧延が再結晶領域で行われるように制御し、粗圧延出口温度を１０２０～１１００℃に制御する；仕上圧延過程に準定速圧延プロセスを適用し、仕上圧延速度を６～１２ｍ／ｓに制御し、鋼材圧延加速度を≦０．００５ｍ／ｓ２に制御する；仕上圧延温度を８４０～９００℃に制御する；
（４）脱リン；
（５）層流冷却：緩和時間を０～８ｓに制御し、層流冷却速度を４０～７０℃／ｓに制御する；
（６）巻取り；
（７）平坦化；
（８）酸洗。
In order to achieve the above object of the invention, the method for producing the high hole expandability dual phase steel provided by the present invention includes the following steps:
(1) smelting and casting;
(2) heating;
(3) hot rolling: control the total rolling reduction to ≥ 80%, control the rough rolling to be performed in the recrystallization region, and control the rough rolling exit temperature to 1020 ~ 1100 ° C; Apply a constant speed rolling process, control the finish rolling speed to 6~12m/s, control the steel rolling acceleration to ≤0.005m/ s2 ; control the finish rolling temperature to 840~900°C;
(4) dephosphorization;
(5) laminar cooling: control the relaxation time to 0-8 s and the laminar cooling rate to 40-70° C./s;
(6) winding;
(7) flattening;
(8) Pickling.
本発明にかかる製造方法において、熱間圧延の総圧下率を≧８０％に制御する；粗圧延が再結晶領域で行われることを確保すると共に、オーステナイト領域での微量合金析出を回避する；粗圧延出口温度を１０２０～１１００℃に制御する；仕上圧延過程に準定速圧延プロセスを適用し、鋼材圧延加速度を≦０．００５ｍ／ｓ２に制御し、仕上圧延速度を６～１２ｍ／ｓに制御する；仕上圧延温度を８４０～９００℃の間に制御し、未再結晶領域で圧延を行うことで、結晶粒を微細化させると共に、変形誘起析出にも有利である；標的温度を確保する前提で、定速圧延時の安定した空冷時間を確保し、緩和冷却時間の制御に有利である。 In the manufacturing method according to the present invention, the total reduction ratio of hot rolling is controlled to ≧80%; ensuring that rough rolling is performed in the recrystallization region and avoiding trace alloy precipitation in the austenite region; Control the rolling exit temperature to 1020-1100°C; apply the semi-constant speed rolling process in the finishing rolling process, control the steel rolling acceleration to ≤0.005m/ s2 , and the finishing rolling speed to 6-12m/s. By controlling the finish rolling temperature between 840 and 900°C and rolling in the non-recrystallized region, the grains are refined and it is also advantageous for deformation-induced precipitation; The target temperature is secured. On the premise, it is advantageous to secure a stable air cooling time during constant speed rolling and control the relaxation cooling time.
また、層流冷却において、前段冷却と緩和制御冷却モードの適用は、結晶粒の回復と微量合金の析出に有利であり、主に仕上圧延帯鋼の速度と開始バルブの位置を制御することで、緩和時間を０～８ｓに制御し、層流冷却速度を４０～７０℃／ｓに制御する。 In addition, in laminar flow cooling, the application of pre-cooling and relaxation control cooling mode is advantageous for grain recovery and trace alloy precipitation, mainly by controlling the speed of the finish rolled strip and the position of the start valve. , the relaxation time is controlled between 0 and 8 s, and the laminar cooling rate is controlled between 40 and 70° C./s.
また、いくつかの好ましい実施形態において、連続鋳造プロセスを適用し、且つ過熱度と二次冷却水を制御し、並びに適切に軽圧下することにより、連続鋳造スラブの中心偏析を制御しても良い。 Also, in some preferred embodiments, the center segregation of the continuously cast slab may be controlled by applying a continuous casting process and controlling the degree of superheat and secondary cooling water, as well as appropriate light reduction. .
さらに、本発明にかかる製造方法において、工程（２）では、加熱温度を１２００～１２６０℃にする。 Furthermore, in the manufacturing method according to the present invention, the heating temperature is set to 1200 to 1260° C. in step (2).
上記形態において、ＴｉとＮｂを十分に固溶させる目的を考慮すると、より有利な効果を得るように、加熱温度を１２００～１２６０℃に設定し、且つ１～３時間保温しても良い。温度が１２６０℃を超えると、結晶粒が粗大化する傾向にあり、鋼板の靭性に不利であると共に、酸化スケールが厚くなり、酸化スケールからの脱リンに不利であることから、加熱温度を１２００～１２６０℃に設定することが好ましい。 In the above embodiment, considering the purpose of sufficiently dissolving Ti and Nb, the heating temperature may be set to 1200 to 1260° C. and maintained for 1 to 3 hours so as to obtain a more advantageous effect. If the temperature exceeds 1260 ° C., the crystal grains tend to coarsen, which is disadvantageous for the toughness of the steel sheet, and the oxide scale becomes thick, which is disadvantageous for dephosphorization from the oxide scale. It is preferable to set to ~1260°C.
さらに、本発明にかかる製造方法において、工程（４）では、脱リン圧力を１５～３５ＭＰａに制御する。 Furthermore, in the production method according to the present invention, the dephosphorization pressure is controlled at 15 to 35 MPa in step (4).
上記形態において、鉄橄欖石（２ＦｅＯ－ＳｉＯ２）が鋼の緻密なスケール層に繋がり、熱間圧延された表面の酸化スケールからの脱リン効果がよくない場合、壊れた酸化スケールの表面の大きな粗さの原因で、層流冷却過程における水の流れが減り、水が局所に貯え、さらに帯鋼の局所性能に影響を与え、帯鋼の局所冷却が影響を受けて不均一となることを考慮すると、脱リン効果がよくないことにより、材料の表面にバラツキが出てくるだけでなく、特性にもバラツキが出てくることから、これに基づいて高圧脱リン水系を好ましく適用することができ、且つ脱リン圧力を１５～３５ＭＰａに制御することができる。 In the above form, when iron olivine (2FeO—SiO 2 ) leads to a dense scale layer of steel, and the dephosphorization effect from the oxide scale on the hot-rolled surface is not good, the broken oxide scale has a large surface area. Due to the roughness, the water flow in the laminar cooling process is reduced, and the water accumulates locally, which further affects the local performance of the strip, and the local cooling of the strip is affected and uneven. Considering that the dephosphorization effect is not good, not only the surface of the material will be uneven, but also the characteristics will be uneven. and the dephosphorization pressure can be controlled at 15-35 MPa.
さらに、本発明にかかる製造方法において、工程（６）では、巻取り温度を４８０～５６０℃にする。 Furthermore, in the manufacturing method according to the present invention, the winding temperature is set to 480 to 560° C. in step (6).
上記形態において、巻取り温度を４８０～５６０℃に制御することで、ベイナイト変態と微量合金析出を制御する。ただし、巻取り温度が高くなると、フェライトとパーライトの含有量が多くなり、穴拡げ率の向上に不利であるが、巻取り温度が低くなると、フェライトの含有量が少なくなると共に、析出量も少なくなり、且つマルテンサイト組織が現れる可能性があり、伸びも低くなる。よって、巻取り温度を４８０～５６０℃の間に制御することで、伸びと穴拡げ率のマッチングの問題を解決できる。 In the above embodiment, bainite transformation and trace alloy precipitation are controlled by controlling the coiling temperature to 480 to 560°C. However, the higher the coiling temperature, the higher the ferrite and pearlite contents, which is disadvantageous for improving the hole expansion ratio. and a martensitic structure may appear, and the elongation is also low. Therefore, by controlling the winding temperature between 480 and 560° C., the problem of matching the elongation and the hole expansion ratio can be solved.
さらに、本発明にかかる製造方法において、工程（７）では、平坦化圧延力を１００～８００トンに制御し、且つ平坦化伸びが≦１．５％を満たす。 Further, in the manufacturing method according to the present invention, in step (7), the flattening rolling force is controlled to 100 to 800 tons, and the flattening elongation satisfies ≦1.5%.
いくつかの好ましい実施形態において、工程（８）では、酸洗速度を６０～１００ｍ／ｍｉｎに制御し、酸洗過程における最終の酸洗槽の温度を８０～９０℃に制御し、鉄イオン濃度を３０～４０ｇ／Ｌに制御する。 In some preferred embodiments, in step (8), the pickling speed is controlled at 60-100 m/min, the temperature of the final pickling tank in the pickling process is controlled at 80-90° C., and the iron ion concentration is is controlled to 30-40 g/L.
本発明に係る高穴拡げ性複相鋼は、以下のような利点及び有益な効果を有する：
本発明にかかる高穴拡げ性複相鋼は、良好な穴拡げ性と良好な可塑性を両立させることができ、且つ本願にかかる高穴拡げ性複相鋼の２相はフェライトとベイナイトであるので、従来の材料である低合金高強度鋼やフェライト・マルテンサイト二相鋼に比べて硬度差が小さいことにより、その穴拡げ性と冷間成形性が良好となる。
The high hole expansibility dual phase steel according to the present invention has the following advantages and beneficial effects:
The high hole expandability dual phase steel according to the present invention can achieve both good hole expandability and good plasticity, and the two phases of the high hole expandability dual phase steel according to the present application are ferrite and bainite. The hole expandability and cold formability are improved due to the smaller difference in hardness compared to conventional materials such as low-alloy high-strength steel and ferrite-martensite duplex steel.
また、本発明にかかる製造方法も同じく、上記の利点及び有益な効果を有する。 The manufacturing method according to the present invention also has the above advantages and beneficial effects.
以下、図面及び具体的な実施例に基づいて、本発明にかかる高穴拡げ性複相鋼及びその製造方法をさらに解釈・説明するが、該解釈・説明は本発明の技術方案を不当に制限するものではない。 The high-hole-expandability dual-phase steel and the manufacturing method thereof according to the present invention will be further interpreted and explained below based on the drawings and specific examples, but the interpretation and explanation unduly restrict the technical solution of the present invention. not something to do.
実施例１～７及び比較例１～６
上記実施例１～７にかかる高穴拡げ性複相鋼及びその製造方法、並びに比較例１～６にかかる比較鋼板は、以下の工程によって調製された：
（１）表１に示す化学成分に従って製錬・鋳造し、転炉で製錬し、溶鋼をＲＨで真空脱ガス処理し、ＬＦ炉で脱硫処理し、ただし、Ｐ≦０．０１５％、Ｓ≦０．００５％のように制御した。連続鋳造の際は、過熱度と二次冷却水を制御し、並びに適切に軽圧下することにより、連続鋳造スラブの中心偏析を制御した。
Examples 1-7 and Comparative Examples 1-6
The high-hole-expandability dual phase steels of Examples 1 to 7 and their manufacturing methods, and the comparative steel sheets of Comparative Examples 1 to 6 were prepared by the following steps:
(1) Smelting and casting according to the chemical composition shown in Table 1, smelting in a converter, vacuum degassing the molten steel at RH, and desulfurizing in an LF furnace, provided that P ≤ 0.015%, S It was controlled such that ≦0.005%. During the continuous casting, the center segregation of the continuously cast slab was controlled by controlling the degree of superheat and the secondary cooling water and by appropriately reducing the pressure.
（２）加熱：加熱温度を１２００～１２６０℃にした。
（３）熱間圧延：総圧下率を≧８０％に制御し、粗圧延が再結晶領域で行われるように制御し、粗圧延出口温度を１０２０～１１００℃に制御した；仕上圧延過程に準定速圧延プロセスを適用し、仕上圧延速度を６～１２ｍ／ｓに制御し、鋼材圧延加速度を≦０．００５ｍ／ｓ２に制御した；仕上圧延温度を８４０～９００℃に制御した。
(2) Heating: The heating temperature was set to 1200-1260°C.
(3) Hot rolling: the total rolling reduction is controlled to ≧80%, the rough rolling is controlled to be performed in the recrystallization region, and the rough rolling exit temperature is controlled to 1020 to 1100 ° C.; A constant speed rolling process was applied, the finish rolling speed was controlled at 6~12m/s, the steel rolling acceleration was controlled at ≤0.005m/ s2 ; the finish rolling temperature was controlled at 840~900°C.
（４）脱リン：脱リン圧力を１５～３５ＭＰａに制御した。
（５）層流冷却：緩和時間を０～８ｓに制御し、層流冷却速度を４０～７０℃／ｓに制御した。
(4) Dephosphorization: Dephosphorization pressure was controlled at 15-35 MPa.
(5) Laminar flow cooling: The relaxation time was controlled at 0-8 s, and the laminar flow cooling rate was controlled at 40-70° C./s.
（６）巻取り：巻取り温度を４８０～５６０℃にした。
（７）平坦化：平坦化圧延力を１００～８００トンに制御し、且つ平坦化伸びが≦１．５％を満たした。
(6) Winding: The winding temperature was 480-560°C.
(7) Flattening: The flattening rolling force was controlled at 100-800 tons, and the flattening elongation met ≦1.5%.
（８）酸洗：酸洗速度を６０～１００ｍ／ｍｉｎに制御し、酸洗過程における最終の酸洗槽の温度を８０～９０℃に制御し、鉄イオン濃度を３０～４０ｇ／Ｌに制御した。 (8) Pickling: Control the pickling speed to 60-100m/min, control the temperature of the final pickling bath in the pickling process to 80-90°C, and control the iron ion concentration to 30-40g/L. did.
実施例１～７にかかる高穴拡げ性複相鋼及びその製造方法、並びに比較例１～６における各化学元素の質量百分率配合は表１に示す。 Table 1 shows the high-hole-expandability dual-phase steels according to Examples 1-7, their production methods, and the mass percentage formulations of chemical elements in Comparative Examples 1-6.
実施例１～７にかかる高穴拡げ性複相鋼及びその製造方法、並びに比較例１～６にかかる比較鋼板の具体的なプロセスパラメーターは表２に示す。 Table 2 shows specific process parameters of the high hole expandability dual phase steels of Examples 1 to 7 and their manufacturing methods, and the comparative steel sheets of Comparative Examples 1 to 6.
ＩＳＯ／ＤＩＳ１６６３０規格に準拠した穴広げ率計測方法に従い、試験片サンプルのサイズを１５０×１５０ｍｍにし、抜き穴のサイズをΦ１０ｍｍにし、クリアランスを１２．５％にし、６０°の円錐パンチを用いてせん断面から穴を広げ、き裂が板厚を貫通した時点の内径ｄを求めた。穴拡げ前の内径をｄ０とすると、下式から限界穴拡げ値λ％を求めた。限界穴拡げ値λ％＝（ｄ－ｄ０）／ｄ０×１００％。引張規格は、横方向のＪＩＳ ５＃引張試験片を採取し、力学的特性を測定した；１８０°曲げ特性は、ＧＢ／Ｔ２３２－２０１０規格に準拠して実施された。 According to the hole expansion rate measurement method in accordance with the ISO / DIS16630 standard, the size of the test piece sample is set to 150 × 150 mm, the size of the punched hole is set to Φ10 mm, the clearance is set to 12.5%, and a 60 ° conical punch is used. The hole was widened from the cross section, and the inner diameter d was determined when the crack penetrated through the plate thickness. Assuming that the inner diameter before hole expansion is d0 , the limit hole expansion value λ% was obtained from the following equation. Limit hole expansion value λ%=(d−d 0 )/d 0 ×100%. Tensile standards were obtained by taking JIS 5# tensile test specimens in the transverse direction and measuring mechanical properties; 180° bending properties were performed in accordance with GB/T232-2010 standards.
実施例１～７にかかる高穴拡げ性複相鋼及びその製造方法、並びに比較例１～６にかかる比較鋼板の力学的特性の計測結果は表３に示す。 Table 3 shows the measurement results of the mechanical properties of the high-hole expandability dual-phase steels according to Examples 1 to 7 and their manufacturing methods, and the comparative steel sheets according to Comparative Examples 1 to 6.
表３から分かるように、本願の各実施例にかかる高穴拡げ性複相鋼において、その横方向引張強度が≧７８０ＭＰａで、降伏強度が≧７００ＭＰａで、伸びＡ５０が≧１５％で、抜き穴の穴拡げ率が≧５０％であった。 As can be seen from Table 3, in the high-hole expandable dual-phase steel according to each example of the present application, the transverse tensile strength is ≧780 MPa, the yield strength is ≧700 MPa, the elongation A50 is ≧15%, and the The hole expansion rate was ≧50%.
表１も併せて見れば分かるように、比較例１において、Ｃｒ－０．５（Ｓｉ＋Ａｌ）が０．２％≦Ｃｒ－０．５（Ｓｉ＋Ａｌ）≦０．４２％の要件を満たしておらず、実施例１に比べると、両者は同じプロセスを適用したが、比較例１のほうは、Ｓｉ含有量が高く、鉄橄欖石（２ＦｅＯ－ＳｉＯ２）酸化スケールが形成しやすく且つ除去しにくく、高レベルの表面を有する帯鋼を獲得することが困難であったと共に、表面の赤スケールの制御が難しいので、熱間圧延温度測定過程において正確に測定することが難しくなり、製品の不安定な性能に繋がり、鉄橄欖石（２ＦｅＯ－ＳｉＯ２）が存在する箇所の強度が高すぎ、伸びが低かった。表１では、比較例２において、Ｃｒ－０．５（Ｓｉ＋Ａｌ）が０．２％≦Ｃｒ－０．５（Ｓｉ＋Ａｌ）≦０．４２％の要件を満たしておらず、実施例１に比べると、両者は同じプロセスを適用したが、比較例２のほうは、ベイナイト組織の変態に不利であり、組織中に多角形フェライトとパーライトが多量に存在し、強度の向上及び穴拡げ率の向上に不利であった。表１では、比較例３と実施例２を比較すると分かるように、比較例３のＴｉ含有量が低く、０．０８％≦３．３Ｎｂ＋Ｔｉ≦０．２０％を満たしておらず、両者は同じプロセスを適用したが、比較例３のほうは、結晶粒微細化作用が小さく、且つ析出強化作用も弱く、引張強度が７８０ＭＰａ以上に到達できなかった。 As can be seen from Table 1, in Comparative Example 1, Cr-0.5 (Si + Al) does not satisfy the requirement of 0.2% ≤ Cr-0.5 (Si + Al) ≤ 0.42%. , Compared to Example 1, both applied the same process, but Comparative Example 1 had a higher Si content, and olivine (2FeO—SiO 2 ) oxide scale was easily formed and difficult to remove. It was difficult to obtain a strip with a high surface level, and it was difficult to control the red scale on the surface, which made it difficult to measure accurately in the hot rolling temperature measurement process, resulting in unstable products. Contributing to the performance, the strength was too high and the elongation was low where the olivine (2FeO—SiO 2 ) was present. In Table 1, in Comparative Example 2, Cr-0.5 (Si + Al) does not satisfy the requirement of 0.2% ≤ Cr-0.5 (Si + Al) ≤ 0.42%, and compared to Example 1 , Both applied the same process, but in Comparative Example 2, the transformation of the bainite structure was disadvantageous, and a large amount of polygonal ferrite and pearlite existed in the structure. was a disadvantage. In Table 1, as can be seen by comparing Comparative Example 3 and Example 2, the Ti content in Comparative Example 3 is low and does not satisfy 0.08% ≤ 3.3Nb + Ti ≤ 0.20%, and both are the same Although the process was applied, in Comparative Example 3, the grain refining action was small and the precipitation strengthening action was weak, and the tensile strength could not reach 780 MPa or more.
また、表２と併せて見れば分かるように、比較例４において、加熱温度が比較的に低く、ＴｉとＮｂの固溶に不利であり、後段の冷却と巻取り過程においてＮｂとＴｉの微細な炭化物の析出に不利であり、強度の向上に不利であった。比較例５において、低い巻取り温度が適用されたが、過冷却組織にある程度のマルテンサイトが存在するようになり、伸びと穴拡げ率の向上に不利であった。比較例６において、大きな平坦化量が適用されたが、実施例１に比べて、伸びが３．４％損失した。 In addition, as can be seen in conjunction with Table 2, in Comparative Example 4, the heating temperature was relatively low, which was disadvantageous for the solid solution of Ti and Nb. This is disadvantageous for the precipitation of large carbides, and is also disadvantageous for improving the strength. In Comparative Example 5, a low coiling temperature was applied, but a certain amount of martensite was present in the supercooled structure, which was disadvantageous in improving elongation and hole expansion ratio. In Comparative Example 6, a large amount of flattening was applied, but compared to Example 1, there was a 3.4% loss in elongation.
熱間圧延された表面状態の相違が力学的特性の均一性に及ぼす影響を比較するために、実施例４の組成とプロセスを用いて、異なる脱リン圧力を設定したことで異なる表面状態の帯鋼を獲得したが、表面処理効果が悪いほど、その表面粗さが大きくなり、強度も相応に高くなり、伸びが低くなった。 In order to compare the effects of different hot rolled surface conditions on the uniformity of mechanical properties, using the composition and process of Example 4, bands with different surface conditions were obtained by setting different dephosphorization pressures. The steel was obtained, but the worse the surface treatment effect, the greater its surface roughness, the correspondingly higher strength, and the lower elongation.
表面状態の相違が力学的特性に及ぼす影響は表４に示す。また、図３と図４はそれぞれ、異なる表面状態のプロファイルを示す。ただし、図３は、表面が良好な帯鋼の表面酸化スケールの表面プロファイルを示し、図４は、表面が「ＮＧ１」の帯鋼の表面酸化スケールの表面プロファイルを示す。 Table 4 shows the effects of surface state differences on mechanical properties. 3 and 4 also show profiles of different surface conditions, respectively. However, FIG. 3 shows the surface profile of the surface oxide scale of the steel strip with a good surface, and FIG. 4 shows the surface profile of the surface oxide scale of the steel strip with the "NG1" surface.
図１は、実施例１にかかる高穴拡げ性複相鋼の金属ミクロ組織図である。
図２は、実施例１にかかる高穴拡げ性複相鋼のＳＥＭミクロ組織図である。
FIG. 1 is a metal microstructure diagram of the high-hole expandability dual-phase steel according to Example 1. FIG.
FIG. 2 is a SEM microstructure diagram of the high hole expandability dual phase steel according to Example 1. FIG.
図１と図２を併せて見れば分かるように、本願にかかる高穴拡げ性複相鋼の微細組織はフェライト＋ベイナイトであり、微細組織には、（Ｔｉ，Ｎｂ）Ｃ及びＮｂＮを含む微量合金析出物があった。 1 and 2 together, the microstructure of the high-hole expandability dual-phase steel according to the present application is ferrite + bainite, and the microstructure contains (Ti, Nb) C and NbN in small amounts. There were alloy precipitates.
図５は、実施例３にかかる高穴拡げ性複相鋼の、異なる平坦化変形量での力学的特性の変化を示す。 FIG. 5 shows changes in mechanical properties of the high hole-expandability dual-phase steel according to Example 3 at different amounts of flattening deformation.
図５に示すように、平坦化量の増加に従い、強度は向上する傾向にあった。
以上から分かるように、本発明にかかる高穴拡げ性複相鋼は、良好な穴拡げ性と良好な可塑性を両立させることができ、且つ本願にかかる高穴拡げ性複相鋼の２相はフェライトとベイナイトであるので、従来の材料である低合金高強度鋼やフェライト・マルテンサイト二相鋼に比べて硬度差が小さいことにより、その穴拡げ性と冷間成形性が良好となる。また、本発明にかかる製造方法も同じく、上記の利点及び有益な効果を有する。
As shown in FIG. 5, the strength tended to improve as the amount of flattening increased.
As can be seen from the above, the high hole-expandability dual phase steel according to the present invention can achieve both good hole expandability and good plasticity, and the high hole expandability dual phase steel according to the present application has two phases: Since it is ferrite and bainite, the difference in hardness is small compared to conventional materials such as low-alloy high-strength steel and ferritic-martensite dual-phase steel. The manufacturing method according to the present invention also has the above advantages and beneficial effects.
本発明の保護の範囲における従来技術部分は、本出願書類に記載の実施例に限定されるものではなく、本発明の方案と矛盾しない先行技術（先行の特許文献、先行の公開出版物、先行の公開使用などを含むが、それらに限定されない）は、全て本発明の保護の範囲に取り入れられることを説明すべきである。 The prior art part within the scope of protection of the present invention is not limited to the examples described in this application, but rather prior art (prior patent documents, prior publications, prior (including but not limited to public use of ) are all encompassed within the scope of protection of the present invention.
また、本願における各技術特徴の組み合わせは、本願の特許請求の範囲に記載の組み合わせ、若しくは具体的な実施例に記載の組み合わせに限定されるものではなく、互いに矛盾していない限り、本願の記載の技術特徴は全て任意の形態で自由に組み合わせる若しくは結合することができる。 In addition, the combination of each technical feature in this application is not limited to the combination described in the claims of this application or the combination described in the specific example, unless it contradicts each other, All the technical features of can be freely combined or combined in any form.
本発明は上記の実施例に限定されるものではなく、当業者が本発明の開示内容から直接的に導き出すことができる、又は容易に想到することができる類似の変化若しくは変形はいずれも、本発明の保護範囲に含まれることは、明らかである。
The present invention is not limited to the examples described above, and any similar changes or modifications that can be directly derived from the disclosure of the present invention or can be easily conceived by a person skilled in the art may be incorporated into the present invention. It is clearly included in the protection scope of the invention.
Claims (13)
Ｃ：０．０６～０．０９％、Ｓｉ：０．０５～０．５％、Ａｌ：０．０２～０．１％、Ｍｎ：１．５～１．８％、Ｃｒ：０．３～０．６％、Ｎｂ≦０．０３％、Ｔｉ：０．０５～０．１２％、残部はＦｅ及び他の不可避不純物である。 A high hole expandability dual phase steel characterized by having a ferrite + bainite microstructure and having the following chemical element mass percentages:
C: 0.06-0.09%, Si: 0.05-0.5%, Al: 0.02-0.1%, Mn: 1.5-1.8%, Cr: 0.3- 0.6%, Nb≦0.03%, Ti: 0.05-0.12%, the balance being Fe and other unavoidable impurities.
０．２％≦Ｃｒ－０．５（Ｓｉ＋Ａｌ）≦０．４２％；
０．０８％≦３．３Ｎｂ＋Ｔｉ≦０．２０％。 2. The high-hole expandable double phase steel according to claim 1, wherein the chemical element mass percentage content satisfies at least one of the following formulas:
0.2%≦Cr−0.5(Si+Al)≦0.42%;
0.08%≤3.3Nb+Ti≤0.20%.
引張強度Ｒｍ＝３４３＋７８９×Ｃ＋１７０×Ｓｉ＋１３２×Ｍｎ＋１９５×Ｃｒ＋８４３×（Ｎｂ＋Ｔｉ）－２０７×Ａｌ、ただし、引張強度Ｒｍの次元はＭＰａである。 6. The high-hole expandable double-phase steel according to any one of claims 1 to 5, characterized in that its tensile strength and chemical element mass percentage content satisfy the following formulae.
Tensile strength Rm = 343 + 789 x C + 170 x Si + 132 x Mn + 195 x Cr + 843 x (Nb + Ti) - 207 x Al, where the dimension of tensile strength Rm is MPa.
（１）製錬・鋳造；
（２）加熱；
（３）熱間圧延：総圧下率を≧８０％に制御し、粗圧延が再結晶領域で行われるように制御し、粗圧延出口温度を１０２０～１１００℃に制御する；仕上圧延過程に準定速圧延プロセスを適用し、仕上圧延速度を６～１２ｍ／ｓに制御し、鋼材圧延加速度を≦０．００５ｍ／ｓ２に制御する；仕上圧延温度を８４０～９００℃に制御する；
（４）脱リン；
（５）層流冷却：緩和時間を０～８ｓに制御し、層流冷却速度を４０～７０℃／ｓに制御する；
（６）巻取り；
（７）平坦化；
（８）酸洗。 A method for producing a high hole expandability dual phase steel according to any one of claims 1 to 8, characterized by comprising the following steps.
(1) smelting and casting;
(2) heating;
(3) hot rolling: control the total rolling reduction to ≧80%, control the rough rolling to be performed in the recrystallization region, and control the rough rolling exit temperature to 1020-1100 ° C; Apply a constant speed rolling process, control the finish rolling speed to 6~12m/s, control the steel rolling acceleration to ≤0.005m/s2; control the finish rolling temperature to 840~900°C;
(4) dephosphorization;
(5) laminar cooling: control the relaxation time to 0-8 s and the laminar cooling rate to 40-70° C./s;
(6) winding;
(7) flattening;
(8) Pickling.
10. The manufacturing method according to claim 9, wherein in the step (7), the flattening rolling force is controlled to 100-800 tons, and the flattening elongation satisfies ≦1.5%.
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