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600MPa-grade hot rolled TRIP(transformation-induced plasticity)-type double-phase steel and preparation method thereof

A dual-phase steel and main body technology, applied in the field of hot-rolled advanced high-strength steel for automobiles, can solve problems such as difficult forming and difficult to meet, and achieve the effects of improving safety factor, good economic applicability and application prospect

Active Publication Date: 2019-03-01
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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  • 600MPa-grade hot rolled TRIP(transformation-induced plasticity)-type double-phase steel and preparation method thereof
  • 600MPa-grade hot rolled TRIP(transformation-induced plasticity)-type double-phase steel and preparation method thereof
  • 600MPa-grade hot rolled TRIP(transformation-induced plasticity)-type double-phase steel and preparation method thereof

Examples

Experimental program
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Effect test

preparation example Construction

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

[0027] S1. Hot metal smelting and casting to obtain a billet meeting the chemical composition requirements, heating the billet to 1150-1250°C under the protection of 99.99% high-purity nitrogen and keeping it warm for 1.5-2.5 hours;

[0028] S2. Controlled hot rolling of the slab after heat preservation, the controlled hot rolling includes 2-3 passes of rough rolling and 3-5 passes of finish rolling, and the total reduction of the rough rolling is 82-84%. The finish rolling is rolled at a constant speed of 7-8m / s, the total reduction of the finish rolling is 75-82%, and a hot-rolled steel strip with a thickness of 4.3-4.7mm is obtained;

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

Embodiment 1

[0032] This embodiment provides a method for preparing a 600MPa grade hot-rolled TRIP type dual-phase steel, the steps comprising:

[0033] The slab is heated to 1200° C. for 2 hours under the protection of 99.99% high-purity nitrogen, and 99.99% of purity nitrogen is used for protection during heating. The chemical composition of the slab is as follows: by mass percentage, C: 0.124%, Si: 0.39%, Mn: 1.67%, Alt: 0.42%, P: 0.014%, and the rest is Fe and unavoidable impurities.

[0034] The slab after heating and heat preservation is started to be hot-rolled at 1180° C. The hot-rolling process is controlled as follows: 3 passes of rough rolling, the total reduction of rough rolling is 83%, and then 4 passes of finish rolling. Rolling at a constant speed of 7.5m / s, the entrance temperature of the final pass of finishing rolling is 880°C, and the total reduction of finishing rolling is 79%, to obtain a hot-rolled steel strip with a thickness of 4.5mm;

[0035] The obtained hot-rol...

Embodiment 2

[0039] This example provides a 600MPa grade hot-rolled TRIP dual-phase steel, using the same preparation steps as Example 1, the difference is that the chemical composition of the slab is: by mass percentage, C: 0.131%, Si : 0.36%, Mn: 1.55%, Alt: 0.45%, P: 0.012%, and the rest are Fe and unavoidable impurities.

[0040] The microstructure of the obtained 600MPa grade hot-rolled TRIP type dual-phase steel consists of three phases: ferrite, martensite and film-like retained austenite. The percentages of each phase in the surface structure (volume percentage, %) are: 5.2% retained austenite, 11% martensite, the rest are ferrite, and there are rod-shaped 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 1000 square micron...

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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 in particular relates to a 600MPa hot-rolled TRIP 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 applied to the preparation of automotive structural parts. 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 for automotive design. However, when phase transformation induced plasticity steel is used, there is a certain margin in the elongation rate, which causes waste, and the higher the strength level, the worse the weldability, but the residual austenite in TRIP steel can absorb energy when e...

Claims

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Application Information

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Patent Type & Authority Applications(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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