Method for improving overall performance of multi-phase steel with hot-rolled deformation substructure

A technology of comprehensive performance and substructure, applied in the field of improving the comprehensive performance of multi-phase steel, can solve the problems of increasing the sensitivity index of cold cracks of steel plates, increasing the difficulty of welding, and increasing the manufacturing cost of steel plates, so as to increase the stability and hardenability, excellent Cold workability, effect of reducing Pcm value

Active Publication Date: 2018-02-09
WUHAN UNIV OF SCI & TECH
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  • Abstract
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Problems solved by technology

Similarly, too much hard phase is not conducive to the cold forming performance of the steel plate
[0004] 2) Some adopt both front-mounted ultra-fast cooling and rear-mounted ultra-fast cooling in controlled cooling, and use ultra-fast cooling technology more than once. Such cooling means have high requirements on equipment and high equipment pressure, and at the same time increase the cost
Although the strength level of the multi-phase steel is relatively high, the first and third stages of controlled cooling adopt pre-type ultra-fast cooling and rear-mounted ultra-fast cooling respectively, and the controlled cooling equipment is complex and demanding
[0005] 3) Some steels do not add or add a small amount of alloy, although the cost is low, but the overall performance is slightly worse
For example, "a hot-rolled dual-phase steel and its production method" (CN201310414988.1) patent technology discloses a method for producing ferrite + martensitic dual-phase steel by rapid cooling, air cooling and laminar cooling. Although the technology does not add precious alloy elements and does not need to add ultra-fast cooling equipment, the cost is low, but the strength is low, around 650MPa, and the cold bending performance cannot be guaranteed
"A method for preparing hot-rolled dual-phase steel by pre-type ultra-fast cooling" (CN 201210085758.0) patent technology discloses a method for preparing hot-rolled dual-phase steel by using front-type ultra-fast cooling. The prepared dual-phase steel Although the strength is 650~700MPa, it does not involve cold working performance
[0006] 4) Some steels have high alloy content, complex process and high cost
A higher alloy addition not only increases the manufacturing cost of the steel plate, but also increases the cold crack sensitivity index Pcm value of the steel plate, which increases the difficulty of welding
Although the strength of the steel plate produced by this technology is about 800MPa, the elongation is insufficient, as low as 11.5%, and the yield ratio is as high as 0.86

Method used

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  • Method for improving overall performance of multi-phase steel with hot-rolled deformation substructure

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Experimental program
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Effect test

Embodiment 1

[0020] A method for improving the comprehensive performance of multi-phase steel by using the deformed substructure after hot rolling. The low-carbon steel with a thickness of 30.0mm is firstly rough-rolled in Ac 3 Finish rolling in the range of ~910°C, and the cumulative reduction rate of finish rolling is 60~80%; then cool at a rate of 95~135°C / s to 540~640°C, and then air cool for 6~11s, so that part of the steel will form ferrite , and finally laminar cooling to room temperature to obtain ferrite + martensite + retained austenite multiphase steel.

[0021] The chemical composition of the low carbon steel is: C is 0.01~0.09wt%, Mn is 0.5~1.0wt%, Si is 0.10~0.25wt%, Nb is 0.020~0.030wt%, Al is 0.04~0.06wt%, Cr is 0.20~0.75wt%, P is 0.020~0.048wt% and S≤0.005wt%, and the rest is iron and unavoidable impurities.

[0022] The mechanical properties of the multiphase steel obtained in this embodiment are: yield strength Rp 0.2 422~439MPa; tensile strength R m 820~838MPa; Elon...

Embodiment 2

[0024] A method for improving the comprehensive performance of multi-phase steel by using the deformed substructure after hot rolling. The low-carbon steel with a thickness of 30.0mm is firstly rough-rolled in Ac 3 Finish rolling in the range of ~910℃, and the rolling reduction rate of the finishing rolling is 80~100%; then cooling to 580~680℃ at a rate of 110~150℃ / s, air cooling for 5~10s, so that part of the steel will form ferrite, Finally laminar cooling to room temperature.

[0025] The chemical composition of the low carbon steel is: C is 0.02~0.10wt%, Mn is 1.1~1.6wt%, Si is 0.20~0.35wt%, Nb is 0.015~0.025wt%, Al is 0.03~0.05wt%, Cr is 0.10~0.65wt%, P is 0.010~0.038wt%, and S≤0.005wt%, and the rest is iron and unavoidable impurities.

[0026] The mechanical property of the multi-phase steel that present embodiment obtains is: Yield strength Rp 0.2 438~455MPa; tensile strength R m 835~850MPa; Elongation A 50It is 21~24%; the yield strength ratio is 0.515~0.545; the ...

Embodiment 3

[0028] A method for improving the comprehensive performance of multi-phase steel by using the deformed substructure after hot rolling. The low-carbon steel with a thickness of 30.0mm is firstly rough-rolled in Ac 3 Finish rolling in the range of ~910°C, and the cumulative reduction rate of the finish rolling is 70~90%; then cool at a rate of 80~120°C / s to 610~710°C, and then hold the temperature for 7~12s, so that part of the steel will form ferrite , and finally cooled to room temperature by laminar flow.

[0029] The chemical composition of the low carbon steel is: C≤0.08wt%, Mn 0.8~1.3wt%, Si≤0.15wt%, Nb≤0.020wt%, Al 0.02~0.04wt%, Cr≤0.55wt%, P≤0.028wt% and S≤0.005wt%, the rest is iron and unavoidable impurities.

[0030] The mechanical properties of the multiphase steel obtained in this embodiment are: yield strength Rp 0.2 415~428MPa; tensile strength R m 795~825MPa; Elongation A 50 is 23~26%; yield ratio is 0.5~0.542; processing hardness index n is 0.13~0.15.

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Abstract

The invention particularly relates to a method for improving the overall performance of multi-phase steel with a hot-rolled deformation substructure. According to the technical scheme, the method includes the steps that low-carbon steel subjected to rough rolling is precisely rolled within the section of Ac3-910 DEG C at first, and the precise-rolling reduction rate is accumulated to be 60%-100%;then the temperature is lowered to 540-710 DEG C at the speed of 80-150 DEG C / s; afterwards, heat preservation lasts for 5-12s or air cooling lasts for 5-12s; and finally laminar cooling is conductedto an indoor temperature. The low-carbon steel comprises, by weight, 0-0.10% of C, 0.5%-1.6% of Mn, 0-0.35% of Si, 0-0.030% of Nb, 0.02%-0.06% of Al, 0-0.75% of Cr, 0-0.048% of P, 0-0.005% of S and the balance iron and inevitable impurities. The method for improving the overall performance of the multi-phase steel with the hot-rolled deformation substructure is simple in technology, the content ofthe alloy elements is low, and the overall performance of the obtained multi-phase steel is good.

Description

technical field [0001] The invention belongs to the technical field of improving the comprehensive performance of multiphase steel. Specifically, it relates to a method for improving the comprehensive performance of multi-phase steel by using the deformed substructure after hot rolling. Background technique [0002] Steel with high strength, good plasticity and toughness and cold forming performance is one of the key points in the development of iron and steel enterprises. Dual-phase steel belongs to this type of steel, which has low yield ratio, continuous yield, high initial work hardening rate, and good strength and elongation. Features such as matching and high bake hardening are widely used in the automotive field to reduce body weight and ensure safe operation. In traditional hot-rolled dual-phase steel, alloying elements such as Mo are added to inhibit the formation of pearlite and bainite, and reduce the critical cooling rate of martensite, so that ferrite + martens...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D8/02C22C38/02C22C38/04C22C38/06C22C38/12C22C38/38
CPCC21D8/0205C21D8/0221C21D8/0247C22C38/02C22C38/04C22C38/06C22C38/12C22C38/38
Inventor 吴润刘娅琴吴腾柯德庆周和荣向志东
Owner WUHAN UNIV OF SCI & TECH
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