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780 MPa-grade low-carbon low-alloy hot-dip galvanized TRIP steel and rapid heat treatment method thereof

A rapid heat treatment and hot-dip galvanizing technology, applied in heat treatment furnaces, heat treatment equipment, hot-dip galvanizing processes, etc., can solve the problems of increasing the cost of precious metals, and achieve the effects of superior performance, increased elongation, and increased tensile strength.

Active Publication Date: 2019-06-28
BAOSHAN IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

By reducing the addition of Si and Mn, and adding P, Nb, Mo, Cr and other alloys to improve the strength, it can greatly reduce the selective oxidation in the process of continuous annealing and galvanizing, improve its platability, and ensure its strength and plasticity at 20GPa% The above, but the ultra-fast cooling technology is adopted after hot rolling, which significantly increases the requirements for equipment, and the addition of precious metals also brings about an increase in cost

Method used

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  • 780 MPa-grade low-carbon low-alloy hot-dip galvanized TRIP steel and rapid heat treatment method thereof
  • 780 MPa-grade low-carbon low-alloy hot-dip galvanized TRIP steel and rapid heat treatment method thereof
  • 780 MPa-grade low-carbon low-alloy hot-dip galvanized TRIP steel and rapid heat treatment method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0060] The chemical composition of the selected raw material steel is calculated by weight percentage: C-0.16%, Mn-1.6%, Si-1.4%, and the balance is Fe and unavoidable impurity elements. The steel plate before heat treatment is cold-rolled strip steel, and the cold-rolling reduction rate is 65%. The microstructure of steel plate after cold rolling is composed of pearlite and ferrite.

[0061] GI product heat treatment process steps are as follows:

[0062] 1) Heat the steel plate to 770°C at a heating rate of 300°C / s and keep it warm for 40s;

[0063] 2) Cool the steel plate to 410°C at a cooling rate of 40°C / s and keep it warm for 215s;

[0064] 3) Heating from 410°C to 460°C for hot-dip galvanizing;

[0065] 4) Rapid cooling to room temperature at a cooling rate of 50°C / s.

[0066] The heat treatment steps of GA products are as follows:

[0067] 1) Heat the steel plate to 770°C at a heating rate of 300°C / s and keep it warm for 40s;

[0068] 2) The steel strip is cooled...

Embodiment 2

[0077] The chemical composition of the selected raw material steel is calculated by weight percentage: C-0.22%, Mn-2.2%, Si-1.2%, and the balance is Fe and unavoidable impurity elements. The steel plate before heat treatment is cold-rolled strip steel, and the cold-rolling reduction rate is 55%. The microstructure of steel plate after cold rolling is composed of pearlite and ferrite.

[0078] GI product heat treatment steps are as follows:

[0079] 1) Heat the strip steel plate to 800°C at a heating rate of 30°C / s and keep it warm for 90s;

[0080] 2) The steel strip is cooled to 430°C at a cooling rate of 100°C / s, and held for 200s;

[0081] 3) The strip steel is heated from 430°C to 470°C for hot-dip galvanizing;

[0082] 4) After galvanizing, cool to room temperature at a cooling rate of 150°C / s.

[0083] The heat treatment steps of GA products are as follows:

[0084] 1) Heat the steel plate to 800°C at a heating rate of 30°C / s, and keep it warm for 90s;

[0085] 2) ...

Embodiment 3

[0094] The chemical composition of the selected raw material steel is calculated by weight percentage: C-0.18%, Mn-2.0%, Si-1.6%, and the balance is Fe and unavoidable impurity elements. The steel plate before heat treatment is cold-rolled strip steel, and the cold-rolling reduction rate is 65%. The microstructure of steel plate after cold rolling is composed of pearlite and ferrite.

[0095] GI product heat treatment steps are as follows:

[0096] 1) Heat the steel plate to 850°C at a heating rate of 200°C / s and keep it warm for 65s;

[0097] 2) The steel strip is cooled to 420°C at a cooling rate of 80°C / s, and held for 300s;

[0098] 3) The strip steel is heated from 420°C to 465°C for hot-dip galvanizing;

[0099] 4) Cool to room temperature at a cooling rate of 100°C / s.

[0100] The heat treatment steps of GA products are as follows:

[0101] 1) Heat the steel plate to 850°C at a heating rate of 200°C / s and keep it warm for 65s;

[0102] 2) The steel strip is cooled...

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Abstract

The invention discloses a 780 MPa-grade low-carbon low-alloy hot-dip galvanized TRIP steel and a rapid heat treatment method thereof. The steel comprises the following chemical components of, in percentage by mass, 0.16-0.22% of C, 1.2-1.6% of Si, 1.6-2.2% of Mn, and the balance Fe and inevitable impurities. According to the 780 MPa-grade low-carbon low-alloy hot-dip galvanized TRIP steel and therapid heat treatment method thereof, the recrystallization and phase change processes in the heating process and the phase change process in cooling process are controlled, and finally a three-phase structure which is uniformly distributed on a ferrite matrix by bainite and austenite is obtained; the average grain size of the bainite and the austenite is 1-3 microns; the bainite is submicron granular; the austenite is in the shape of an island-shaped and are uniform-distributed isometric crystal; in the whole of the three-phase structure, the volume fraction of the bainite is 35% -75%, the volume fraction of the ferrite is 10%-60%, and the volume fraction of the austenite is 5%-15%; and through the rapid heat treatment, the mechanical property of the material is improved while the heat treatment efficiency is improved, and the material performance interval range is expanded.

Description

technical field [0001] The invention belongs to the technical field of rapid heat treatment of materials, and in particular relates to a 780MPa low-carbon low-alloy hot-dip galvanized TRIP steel and a rapid heat treatment method thereof. Background technique [0002] With the gradual improvement of people's awareness of energy conservation and material safety in service, the use of high-strength steel, especially advanced high-strength steel, is increasing. This also makes iron and steel enterprises and scientific research institutes pay more and more attention to the development of advanced high-strength steel. In order to further improve the strength-plastic product of steel products, the development of advanced high-strength steel represented by TRIP (phase transformation induced plastic deformation) steel has been paid more and more attention. The cold rolling heat treatment process of cold rolled TRIP steel consists of two stages of austenitizing annealing and bainite ...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C21D9/52C23C2/06C23C2/40
Inventor 孟庆格李俊王健张利祥马新建
Owner BAOSHAN IRON & STEEL CO LTD
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