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Ultra-fine grain ferrite/nano bainite dual-phase medium carbon steel and preparation method thereof

A nano-bainite and ferrite technology, applied in the field of steel material engineering, can solve the problems of low tensile strength and insufficient toughness, and achieve the effects of low yield ratio, easy control, and high strength and plastic product.

Active Publication Date: 2017-06-20
YANSHAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] At present, ferritic / bainitic dual-phase steel is mainly prepared from low-carbon low-alloy steel (including microalloyed and non-microalloyed) through controlled rolling and controlled cooling. The preparation method has been disclosed in a number of patents. For example, the Chinese patent application number 200910169738.X discloses a high tensile strength hot-rolled ferritic bainite dual-phase steel and its manufacturing method. The tensile strength is between 514 and 535 MPa, and the yield strength ratio is 0.63 Above, but the tensile strength is still relatively low, the toughness is not enough

Method used

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  • Ultra-fine grain ferrite/nano bainite dual-phase medium carbon steel and preparation method thereof
  • Ultra-fine grain ferrite/nano bainite dual-phase medium carbon steel and preparation method thereof
  • Ultra-fine grain ferrite/nano bainite dual-phase medium carbon steel and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] A. According to the mass percentage of C 0.35, Si 1.55, Mn 0.74, Cr 0.51, Mo0.2, P 0.006, S 0.002, the balance is the proportion of Fe and unavoidable impurities, calculate the feeding ratio, and use it in a vacuum medium frequency induction furnace It is melted in a medium and poured into a cylindrical steel ingot with a diameter of 170 mm, and refined in a vacuum.

[0023] B. Annealing and hot rolling: heat the steel ingot to 1220°C for 2 hours for homogenization treatment, and air-cool it to 1150°C to start rolling. The final rolling temperature is 880°C. After 6 passes of rolling, it is air-cooled to room temperature after rolling to obtain 20 mm thick hot rolled slab.

[0024] C. Quenching: reheat the hot-rolled slab to 920° C. in the furnace, keep it warm for 40 minutes, and put it into oil to quench and cool to room temperature after being out of the furnace to obtain a quenched slab.

[0025] D. Warm rolling: put the quenched slab into a furnace at 550°C for 1 ...

Embodiment 2

[0033] A. According to the mass percentage of C 0.30, Si 1.70, Mn 0.78, Cr 0.45, Mo0.20, P 0.003, S 0.001, the balance is the ratio of Fe and unavoidable impurities, calculate the feeding ratio, and put it in the vacuum medium frequency induction furnace It is melted in a medium and poured into a cylindrical steel ingot with a diameter of 170 mm, and refined in a vacuum.

[0034] B. Annealing and hot rolling: heat the steel ingot to 1220°C for 2 hours for homogenization treatment, and air-cool it to 1150°C to start rolling. The final rolling temperature is 880°C. After 7 passes of rolling, it is air-cooled to room temperature after rolling to obtain 20 mm thick hot-rolled slabs.

[0035] C. Quenching: reheat the hot-rolled slab to 920° C. in the furnace, keep it warm for 1 hour, put it in oil and quench it to room temperature after being out of the furnace, and obtain the quenched slab.

[0036]D. Warm rolling: put the quenched slab into a furnace at 550°C to keep it warm for...

Embodiment 3

[0041] The difference from Example 1 is: Step D, putting the quenched slab into a furnace at 570 °C for 1 h, taking it out of the furnace to carry out multi-pass warm rolling deformation with a total reduction of 40%, and then air cooling to room temperature to obtain Warm-rolled sheet with a thickness of 12 mm; step E, put the warm-rolled sheet into a furnace with a temperature of 780 °C, keep it warm for 0.5 h, then quickly put it into a salt-bath furnace with a temperature of 240 °C for 2 h, and then take it out of the furnace and air-cool it to room temperature.

[0042] A scanning electron microscope (SEM) analysis and a tensile test were carried out on the plates prepared in this example, and the results are shown in Table 1.

[0043] The results show that: the ultra-fine-grained ferrite / nano-bainite dual-phase steel prepared in this example has high strength, high plasticity, low yield ratio, high strength-plastic product, and good comprehensive mechanical properties. ...

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Abstract

The invention discloses ultra-fine grain ferrite / nano bainite dual-phase medium carbon steel which comprises the following chemical elements in percentage by weight: 0.30-0.35 of C, 1.5-1.7 of Si, 0.7-0.8 of Mn, 0.4-0.6 of Cr, 0.18-0.22 of Mo, less than or equal to 0.02 of P, less than or equal to 0.02 of S and the balance of Fe and unavoidable impurities. The metallographic structures of the dual-phase steel are ultra-fine grain ferrite and nano bainite, wherein the grain size of the ultra-fine grain ferrite is 0.5-3 microns, the volume content of ultra-fine grain ferrite is 48-59%, and the batten size of nano bainite is 95-212 nm. medium carbon silicon-containing low alloy steel is adopted to quench a martensitic structure, the martensitic structure is heated to obtain the temperature of a tempered troostite, temperature is preserved for a period of time, draw a charge, rolling is carried out for deformation at the temperature, air cooling is carried out to the room temperature, then, reheating is carried out to an 'alpha+gamma' two-phase region, partial saturation is carried out, warm-rolling panel is put in a salt bath furnace of a martensite starting point for isothermal bainite transformation, and then an ultra-fine grain ferrite / nano bainite dual-phase structure is obtained through air cooling to the room temperature, wherein the temperature of the salt bath furnace is slightly higher than that of a two-phase region austenite.

Description

[0001] technical field [0002] The invention belongs to the field of iron and steel material engineering, and relates to a dual-phase steel and a preparation method thereof, in particular to an ultrafine-grained ferrite / nanometer bainite dual-phase medium-carbon steel and a preparation method thereof. Background technique [0003] The traditional ferrite / martensitic dual-phase steel has low yield ratio, high initial work hardening rate and good plasticity and toughness. However, due to the large difference in strength between ferrite and martensite, microcracks tend to expand along the ferrite / martensite phase interface, resulting in poor hole expansion performance, and cracks often occur in the hole expansion and flanging process. The ferrite / bainite dual-phase steel replaces martensite with bainite with better toughness, and has better flanging and hole expansion performance than ferrite / martensitic dual-phase steel, and With better tensile properties and impact toughness,...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/22C22C38/04C22C38/34C22C38/02C21D1/26C21D1/20C21D8/02
CPCC21D1/20C21D1/26C21D8/0221C21D8/0226C21D8/0231C21D8/0236C21D8/0247C21D2211/002C21D2211/005C22C38/02C22C38/04C22C38/22C22C38/34C22C38/44C22C38/58
Inventor 王天生贺延明张烈王岳峰
Owner YANSHAN UNIV
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