Preparation method of ferrite-twin-crystal martensite low-carbon steel
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A technology of low-carbon steel and martensite, applied in the field of low-carbon steel preparation, can solve the problems of high toughness and plasticity, reduced toughness and plasticity, and low hardness and strength
Active Publication Date: 2018-12-14
YANSHAN UNIV
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[0004] Under normal circumstances, the annealed structure of the existing low-carbon steel is coarse ferrite + pearlite group, which has high toughness and plasticity and low hardn
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Embodiment 1
[0020] Select Q345b low-carbon steel, the weight percentage of its chemical composition is: C 0.20%, Si 0.36%, Mn0.60%, Cr 0.20%, P 0.035%, S 0.030%, the balance is Fe, heated to 940 ° C for 1 Hours, quenched by 10% sodium chloride aqueous solution to obtain lath martensite; cold rolling at room temperature, the deformation amount is 75%, to obtain deformed lath martensite; heat deformation at 700°C to achieve recrystallization; then elastic stress at 210MPa At 700°C for 40 minutes, an ultra-fine equiaxed ferrite + twin martensite structure is obtained, and there is no carbide such as cementite in the steel.
[0021] Such as figure 1 As shown, a) is the prepared ultrafine equiaxed ferrite + twinned martensite without carbide. b) is a conventional quenched martensite structure, the length of the lath bundle is the original austenite grain size, about 20.1 μm; c) is a conventional annealed ferrite + pearlite structure. The white ferrite grain size is about 19 μm, and the black...
Embodiment 2
[0030] Choose No. 15 low-carbon steel, the weight percentage of its chemical composition is: C 0.13%, Si 0.46%, Mn 0.26%, P 0.021%, S 0.025%, Cr 0.001%, Cu 0.014%, the balance is Fe, heated to Insulate at 940°C for 1 hour, quench with 10% sodium chloride aqueous solution to obtain lath martensite; cold-roll at room temperature, the deformation amount is 75%, and obtain deformed lath martensite; Under the elastic stress of 220MPa, heat preservation at 710°C for 40 minutes, an ultra-fine equiaxed ferrite + twin martensite structure is obtained, and there is no carbide such as cementite in the steel.
[0031] Such as Figure 6 As shown, the preparation is carbide-free ultrafine equiaxed ferrite + twinned martensite, which is an optical metallographic structure, and the polygonal grain boundary shows ultrafine equiaxed grains, and the grain size is about 2.2 μm;
[0032] Such as Figure 7 As shown, due to the different degrees of corrosion, the ultrafine equiaxed grains show une...
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Abstract
The invention relates to a preparation method of ferrite-twin-crystal martensite low-carbon steel. The method mainly comprises the following steps that common low-carbon steel with the carbon contentof 0.13% or 0.20% is adopted, quenching is carried out to obtain low-carbon martensite, 75% rolling deformation at the room temperature is carried out, then deformation is carried out at the temperature of 700 DEG C or 710 DEG C for recrystallization, elastic stress of 210 MPa or 220 MPa is applied at the same temperature, ageing is for 40 minutes so as to obtain the ferrite-twin-crystal martensite low-carbon steel ferrite, wherein ferrite is ultrafine isometric crystal, and the grain size of the twin-crystal martensite is about 2 micrometers. The twin-crystal martensite low-carbon steel. According to the prepared ultrafine isometric crystal ferrite + twin-crystal martensite low-carbon steel, the hardness strength is higher than that in the normalizing state, the toughness plasticity is higher than that in the quenching state, the comprehensive mechanical property is greatly improved, the hardness of the low-carbon steel reaches 1.8 times that in the annealing state, and the elongationrate is 2.1 times that in the quenching state.
Description
technical field [0001] The invention belongs to the technical field of metal materials, in particular to a method for preparing low-carbon steel. technical background [0002] Low carbon steel is carbon steel with a carbon content of less than 0.25%. Low carbon steel is widely used in ships, bridges, vehicles, boilers and other fields. Low carbon steels are annealed or quenched-tempered under service conditions. The annealed structure of low-carbon steel is ferrite plus a small amount of pearlite. Ferrite has a body-centered cubic lattice and contains almost no carbon at room temperature; The number and shape of the body determine the strength and toughness of the steel. For example, R260 steel is subjected to isothermal treatment at 480–620°C to obtain a refined pearlite structure. The size of the pearlite clusters is significantly thinner than that of the conventional 930°C hot-rolled state, and the distance between cementite sheets is reduced by 2 to 4 times. The stren...
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