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Method of preparing high-strength thin-crystal two-phase steel

A dual-phase steel, fine-grained technology, applied in the direction of manufacturing tools, heat treatment equipment, heat treatment process control, etc.

Inactive Publication Date: 2007-10-17
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] The purpose of the invention is to solve the problem of preparing high-strength fine-grained dual-phase steel in low-carbon (manganese) steel, and proposes a method based on supercooled austenite in A 3 ~ Ar 3 Multi-pass deformation between temperature ranges, a technical solution to control the dual-phase structure with strain

Method used

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  • Method of preparing high-strength thin-crystal two-phase steel
  • Method of preparing high-strength thin-crystal two-phase steel
  • Method of preparing high-strength thin-crystal two-phase steel

Examples

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Effect test

Embodiment 1

[0013] Select the low-carbon steel whose chemical composition is: 0.087%C, 1.24%Mn, 0.35%Si, and the balance is Fe. Its A was measured by thermal dilatation method 3 is 860°C, cooling rate C2 is 30°C / s, Ar 3 It is 760°C. After heating the low-carbon steel to 1200°C for 5 minutes, at 1100°C and 1000°C in the temperature range of T2~T3 respectively for 1s -1 The strain rate is deformed, and the deformation amount of each pass is 30%, and the recrystallized austenite structure of about 25 microns is obtained as shown in Fig. 2 . Afterwards, cool at a cooling rate of 30°C / s to 820°C in the temperature range of T4~T5, and -1 The deformation rate is 30% in two passes, the interval between the two passes is 1s, and the cooling rate is 60°C / s to room temperature, and the fine-grained dual-phase structure shown in Figure 3 is obtained. The average grain size of ferrite is about 3.94 microns, the average size of martensitic islands is about 2.56 microns, and the volume fraction is a...

Embodiment 2

[0015] The chemical composition of the selected steel grade is the same as in Example 1. Heat the low-carbon steel to 1200°C for 5 minutes and then heat it at 1100°C and 1000°C in the temperature range of T2~T3 for 1s -1 The strain rate is deformed, and the deformation amount of each pass is 30%, and the recrystallized austenite structure of about 25 microns is obtained as shown in Fig. 2 . After that, cool down to 800°C at a cooling rate of 15°C / s and take 10s -1 The deformation rate is 30% in two passes, the interval between the two passes is 10s, and the cooling rate is 60°C / s to room temperature, and the fine-grained dual-phase structure shown in Figure 4 is obtained. The average grain size of ferrite is about 4.09 microns, the average size of martensitic islands is about 3.33 microns, and the volume fraction is about 10%.

Embodiment 3

[0017] The hot-rolled slab of ordinary low-carbon manganese steel is used, and its chemical composition is: 0.09%C, 1.4%Mn, 0.35%Si, and the balance is Fe. The original thickness of the blank is 15mm. The multi-pass reversible rolling test was carried out on the 350 four / two-high reversible hot strip experimental rolling mill, and the rolling speed used was 500mm.s -1 . The hot rolling process is: 1200°C for 30 minutes, then air-cooled to 1100°C to start rolling, two passes of rolling with a reduction of 30%, the interval between passes is 5s, and the temperature after the second pass is 1000°C about. After that, air cooling (cooling rate is about 12°C / s) to 840°C for two consecutive rolling passes with a reduction of 30%, the interval between passes is 3s, the final rolling temperature is 790°C, and water cooling after rolling. Figure 5 is the SEM morphology of the fine-grained dual-phase structure obtained under this process. The average grain size of ferrite is about 4....

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Abstract

The invention relates to a method for producing the fine grained dual phase steel, especially by low carbon(manganese) steel. The method comprises making the common low carbon(manganese) steel austenization, obtaining small austenitic organism after multi-pass deformation of recrystallized zone, over-cooling to a certain temperature in the temperature range of A3-Ar3 by proper cooling speed to apply multi-pass deformation with a strain rate between 0.1s-1 to 30s-1, getting 80-90% ferrite transforming mass by controlling each pass dependent variable, then quickly cooling or quenching to the room temperature. The average dimension of isometric ferrite grain in fine grained dual phase organism is less than 5 mum. The Martensite island integration number is 10-15% and the average dimension is less than 3 mum. The method is more controllable and is easy to apply on the conventional hot mill.

Description

technical field [0001] The invention relates to a method for preparing fine-grain dual-phase steel, in particular to a method for preparing fine-grain dual-phase steel from low-carbon (manganese) steel. Background technique [0002] The microstructure refinement of dual-phase steel can not only promote the strength of dual-phase steel to a higher level, but also the complex phase of fine-grained structure still has mechanical characteristics such as continuous yield, high strength-to-yield ratio, and good work hardening ability. At present, the way to obtain fine-grained dual-phase steel mainly focuses on large-strain deformation, such as equal channel extrusion (ECAP) or the use of complex deformation heat treatment processes such as TMCP process with lower finish rolling temperature and deformation-induced phase transformation (DIFT). method. “Ultrafine grained dual phase steel fabricated by equal channel angular pressing and subsequent intercritical annealing” (Scripta M...

Claims

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Application Information

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IPC IPC(8): C21D8/00C21D11/00
Inventor 孙祖庆杨王玥徐海卫李龙飞
Owner UNIV OF SCI & TECH BEIJING
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