Method for making ultrafine grained steel

A technology of ultra-fine grains and manufacturing methods, which is applied in manufacturing tools, metal rolling, metal rolling, etc., can solve the problems of increasing production difficulty and cost due to cooling control requirements, and achieve stable grains, simple process, and lightening of rolling mills. load effect

Inactive Publication Date: 2011-04-13
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method not only increases the expensive micro-alloying element Nb, but also increases the difficulty and cost of production due to the high requirements of continuous casting process control and strict cooling control requirements.

Method used

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  • Method for making ultrafine grained steel
  • Method for making ultrafine grained steel
  • Method for making ultrafine grained steel

Examples

Experimental program
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Effect test

Embodiment 1

[0026] A kind of manufacturing method of ultra-fine-grained steel of the present invention, the chemical composition of material used is shown in Table 1, for the carbon steel with carbon content between 0.18% and manganese content between 0.54% in mass fraction , using the following hot deformation process to obtain ultra-fine grain steel, the deformation process is as follows figure 1 shown.

[0027] Heat the sample to 1200°C and hold it for 5 minutes. After it is fully austenitized, cool it to 1000°C, 850°C, and 780°C respectively at a cooling rate of 5°C / s. , 50%, 50%, uniaxial compression test, the strain rate of all deformation passes is Then carry out 5°C / s controlled cooling method to cool down to 600°C, and finally place it in air for cooling. obtained organizations such as figure 2 shown. from figure 2 It can be seen from the figure that the ferrite in the structure is composed of equiaxed ferrite and deformed ferrite, among which the grains of equiaxed ferri...

Embodiment 2

[0031] Yet another method for manufacturing ultra-fine grain steel according to the present invention, the material used is the same as in Example 1, and the post-rolling cooling rate in Example 1 is increased to 10°C / s in the deformation process, and the obtained room temperature microstructure Such as image 3 shown. The ferrite grains in the obtained structure are finer and more uniform than those obtained in Example 1. The average ferrite grain size measured by the intercept method is 2.29 μm.

[0032] It can be seen that the ultra-fine grain steel obtained according to the present invention has small grain size, simple process and low cost.

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Abstract

The invention discloses a method for making ultrafine grained steel, comprising the steps of: heating carbon steel to a temperature of 1200-1240DEG C to carry out austenization, wherein the carbon steel contains 0.02-0.20% of carbon and 0.40-1.60% of manganese by mass fraction; controlling to roll by using an austenite recrystallization area and an austenite non-recrystallization area; performing another deformation near an Ar3 temperature by combining the deformation induced ferrite transformation technology so as to restrain the reverse transformation from the ferrite to the austenite after twice transformation, accumulate mass storage energy of the second transformation, increase the nucleation points of the ferrite, and promote the increase of the volume fraction of the ferrite; and finally cooling to a temperature of 600-650DEG C at a cooling speed of 1-10DEG C / micron for air cooling. The ferrite grain dimension of the prepared ultrafine grained ferrite steel is less than 3.0 microns. The manufacturing method of the ultrafine grained steel does not need large deformation and ultrafast cooling process, and has small mill load and simple process; and the obtained room-temperature ultrafine ferrite grains are stable.

Description

technical field [0001] The invention relates to a production of low-carbon steel, in particular to a method for manufacturing ultra-fine grain steel whose crystal grains can be refined to 3 μm. Background technique [0002] Low carbon steel is an important engineering structural material, which is widely used in infrastructure construction. The performance of low carbon steel mainly depends on its microstructure characteristics, including the size, morphology and spatial distribution of grains and phases, etc. The structural characteristics of the material can be changed by deformation or heat treatment. Therefore, it is particularly important to design appropriate processes to optimize the organization of materials. The optimization process of carbon steel structure has gone through two processes: controlled rolling and controlled cooling technology and deformation-induced ferrite transformation technology. Controlled rolling and controlled cooling is a controlled rolling...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D8/00B21B37/00
Inventor 楚觉非邱红雷王端军刘朝霞李晓玲陈远姝宋世佳范益王晓文赵亚娟李丽
Owner NANJING IRON & STEEL CO LTD
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