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Preparation method of delta-ferrite-containing TRIP (transformation induced plasticity) steel

A technology of ferrite and preparation steps, applied in the field of high-strength steel for automobiles, can solve the problems of loss of optimal strength-plastic balance, poor weldability, surface oxidation, etc.

Active Publication Date: 2017-05-10
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The disadvantage is that the cost of the alloy is high, especially the high carbon equivalent, which leads to poor weldability. Some components contain high Si content, which will cause serious oxidation of the surface of the steel plate during hot rolling, and poor wettability during subsequent coating. Coating is difficult and seriously affects the steel plate. Surface Quality
Some even introduce too much volume fraction of martensite in the structure to sacrifice a certain amount of elongation to increase the tensile strength, thus losing the best balance of strength and plasticity of steel

Method used

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  • Preparation method of delta-ferrite-containing TRIP (transformation induced plasticity) steel
  • Preparation method of delta-ferrite-containing TRIP (transformation induced plasticity) steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] The mass percentage of the chemical composition of the slab is C: 0.25%, Si: 0.62%, Mn: 2.2%, Alt: 3.15%, P: 0.006%, S+N: 0.007%, and the rest is Fe and unavoidable impurities.

[0023] Heat the cast slab at 1150°C, keep it warm for 1 hour, then carry out 2 passes of rough rolling; after rough rolling, it enters the coil box for induction heating, the induction heating temperature is 1050°C, and the holding time is 10 minutes; Steel edge heating device, the finish rolling temperature is 950°C; after finish rolling, it enters ultra-fast cooling, the cooling speed is 220°C / s, the steel strip is cooled to 280°C and then coiled to obtain a hot-rolled steel strip with a thickness of 2.5mm steel belt. Then the hot-rolled steel strip is heat-treated, heated to 800°C for 2 minutes, then rapidly cooled to 400°C, coiled, then put into the heat preservation pit and slowly cooled to 200°C, taken out and naturally cooled to room temperature. The key process parameters are shown in ...

Embodiment 2

[0025] The mass percentage of the chemical composition of the slab is C: 0.26%, Si: 0.81%, Mn: 2.4%, Alt: 2.97%, P: 0.007%, S+N: 0.005%, and the rest is Fe and unavoidable impurities. Take the same preparation steps as in Example 1, the process parameters are as shown in Table 1, and the process parameters not listed in Table 1 are the same as in Example 1. The mechanical properties and structure of the finished product are shown in Table 2.

Embodiment 3

[0027] The chemical composition of the slab is the same as in Example 1. Take the same preparation steps as in Example 1, the process parameters are as shown in Table 1, and the process parameters not listed in Table 1 are the same as in Example 1. The mechanical properties and structure of the finished product are shown in Table 2.

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Abstract

The invention discloses a preparation method of delta-ferrite-containing TRIP (transformation induced plasticity) steel, and belongs to the technical field of high-strength steel for automobiles. The delta-ferrite-containing TRIP steel comprises the following chemical components in percentage by mass: 0.24-0.28% of C, 0.5-1.0% of Si, 1.8-2.5% of Mn, 2.9-3.7% of Alt, no more than 0.01% of P, no more than 0.008% of S+N and the balance of Fe and inevitable impurities. The preparation method comprises the following steps: hot rolling, induction heating, ultra-fast cooling and heat treatment. The steel structure disclosed by the invention contains delta-ferrite, thereby improving the weldability. During composition design, the Al content is increased, thereby obtaining high elongation percentage, lowering the density of the steel, and effectively realizing lightweight development. The structure of the steel finished product comprises alpha-ferrite, delta-ferrite, bainite, thin-film retained austenite (or martensite / austenite island), wherein the volume percent of the retained austenite is 11.31-13.39%. The yield strength of the steel is 486-516 MPa, the tensile strength is 729-799 MPa, the elongation percentage is 28.2-29.8%, and the product of strength and elongation is 20.6-23.8 GPa.%.

Description

technical field [0001] The invention belongs to the technical field of high-strength steel for automobiles, in particular to a preparation method of TRIP steel containing δ-ferrite. Background technique [0002] In recent years, the number of cars in the world is increasing day by day, changing people's work and life with increasing influence. The application of dual-phase (DP) steel, complex-phase steel (CP), phase transformation-induced plasticity steel (TRIP) and martensitic steel (MART) in automobiles has made automobiles more lightweight, energy-saving and environmentally friendly, safe and comfortable, Moving in the direction of low cost. [0003] The structure of TRIP steel contains retained austenite. During plastic deformation, the retained austenite will produce strain hardening, induce martensite nucleation, and undergo martensitic transformation, which will increase the local hardness, and at the same time, the deformation will be further transferred to the surr...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/06C22C38/04C22C38/02C21D8/02
CPCC21D8/0226C21D8/0263C21D2211/001C21D2211/002C21D2211/005C22C38/02C22C38/04C22C38/06
Inventor 赵征志梁驹华张才华梁江涛康涛袁洪涛唐荻赵爱民苏岚
Owner UNIV OF SCI & TECH BEIJING
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