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A kind of 600mpa grade hot-rolled trip type dual-phase steel and its preparation method

A dual-phase steel and hot-rolled steel technology, applied in the field of 600MPa-level hot-rolled TRIP dual-phase steel and its preparation, can solve problems such as difficult to meet, difficult to form, etc., to improve safety factor, good economic applicability and application prospects Effect

Active Publication Date: 2020-12-15
SHOUGANG CORPORATION
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the actual production process, we found that the traditional dual-phase steel is difficult to form on many high-drawability parts, and it is difficult to meet the requirements of complex stamping structural parts in automotive design

Method used

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  • A kind of 600mpa grade hot-rolled trip type dual-phase steel and its preparation method
  • A kind of 600mpa grade hot-rolled trip type dual-phase steel and its preparation method
  • A kind of 600mpa grade hot-rolled trip type dual-phase steel and its preparation method

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Experimental program
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Effect test

preparation example Construction

[0026] The second aspect of the present invention provides the preparation method of the above-mentioned 600MPa grade hot-rolled TRIP type dual-phase steel, the steps comprising:

[0027] S1. The molten iron is smelted and cast to obtain the cast billet that meets the chemical composition requirements, and the cast billet is heated to 1150-1250 ℃ under the protection of 99.99% high-purity nitrogen and kept for 1.5-2.5h;

[0028] S2. Controlling hot rolling of the heat-preserved slab, the controlled hot rolling includes 2-3 passes of rough rolling and 3-5 passes of finishing rolling, and the total reduction of the rough rolling is 82-84%. The finishing rolling is uniformly rolled at a speed of 7-8m / s, and the total reduction of finishing rolling is 75-82% to obtain a hot-rolled steel strip with a thickness of 4.3-4.7mm;

[0029] S3. Cool the hot-rolled steel strip to 690-720°C at a cooling rate of 40-55°C / s, then air-cool it for 20-30s, and then cool it to 250-280°C at a coolin...

Embodiment 1

[0032] The present embodiment provides a preparation method of 600MPa grade hot-rolled TRIP type dual-phase steel, the steps comprising:

[0033] The casting billet was heated to 1200 ℃ under the protection of 99.99% high-purity nitrogen for 2 hours, and protected with nitrogen with a purity of 99.99% during heating. The chemical composition of the cast slab is as follows: in terms of mass percentage, C: 0.124%, Si: 0.39%, Mn: 1.67%, Alt: 0.42%, P: 0.014%, and the rest are Fe and inevitable impurities.

[0034] The hot-rolled slab after heating and heat preservation is started at 1180°C, and the hot-rolling process is controlled as follows: 3 passes of rough rolling, the total rough rolling reduction is 83%, and 4 passes of finishing rolling are carried out. The speed of 7.5m / s was uniformly rolled, the entry temperature of the final pass of finishing rolling was 880°C, and the total reduction of finishing rolling was 79%, and a hot-rolled steel strip with a thickness of 4.5mm...

Embodiment 2

[0039] This embodiment provides a 600MPa-grade hot-rolled TRIP-type dual-phase steel, which adopts basically the same preparation steps as in Embodiment 1, except that the chemical composition of the cast slab is: in terms of mass percentage, C: 0.131%, Si : 0.36%, Mn: 1.55%, Alt: 0.45%, P: 0.012%, and the rest are Fe and inevitable impurities.

[0040] The obtained 600MPa hot-rolled TRIP type dual-phase steel microstructure is composed of three phases: ferrite, martensite and thin-film retained austenite. The percentage of each phase (volume percentage, %) of the surface structure is: 5.2% retained austenite, 11% martensite, the rest are ferrite, and there are rod-like carbides in the ferrite. The percentage of each phase of the main structure of the steel except the surface structure is: 3.5% retained austenite, 38% martensite, the rest is ferrite, no carbide precipitation; within the thickness range of 0-22μm from the surface , the average number of rod-shaped carbides per...

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Abstract

The invention provides 600MPa-grade hot rolled TRIP(transformation-induced plasticity)-type double-phase steel and a preparation method thereof. The 600MPa-grade hot rolled TRIP-type double-phase steel comprises retained austenite, martensite and ferrite; a surface layer of the steel comprises 4-6% of the retained austenite, 5-15% of the martensite and the balance of the ferrite containing rod-like carbides; a main body of the steel comprises 2-5% of the retained austenite, 25-40% of the martensite and the balance of the ferrite, wherein no carbide is precipitated from the ferrite. The specified plastic elongation strength of the steel is 333-351MPa, the tensile strength is 602-614MPa, and the elongation after fracture (80mm in gauge length) is 23-25%. The steel can be applied to complex automotive structural parts and chassis parts, and has high economical efficiency and a good application prospect.

Description

technical field [0001] The invention belongs to the technical field of advanced high-strength steel for hot-rolled automobiles, and particularly relates to a 600MPa-grade hot-rolled TRIP type dual-phase steel and a preparation method thereof. Background technique [0002] At present, hot-rolled advanced high-strength steels for automobiles, such as dual-phase (DP) steels and transformation-induced plasticity (TRIP) steels, have been used in the preparation of automobile structural parts. In the actual production process, we found that the traditional dual-phase steel is difficult to form on many parts with high ductility, and it is difficult to meet the requirements of complex stamping structural parts for automobile design. However, when the transformation-induced plasticity steel is used, the elongation has a certain margin, causing waste, and the higher the strength grade, the worse the weldability, but the retained austenite in the TRIP steel can absorb energy when the e...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D8/02C22C38/02C22C38/04C22C38/06C21D1/18
CPCC21D1/18C21D8/0226C21D2211/001C21D2211/005C21D2211/008C22C38/002C22C38/02C22C38/04C22C38/06
Inventor 刘杰郭佳代晓莉郭子峰刘锟李文远陈斌张旭
Owner SHOUGANG CORPORATION
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