Method for accelerating phase changing of bainite in steel through in-situ nanometer AlN heterogeneous nucleation

A bainite and nanotechnology, applied in the field of materials, can solve problems such as cost increase, manufacturing process complexity, and accelerated bainite transformation

Active Publication Date: 2017-11-10
YANSHAN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

These techniques not only have no obvious effect on accelerating the bainite transformation, but at the same t

Method used

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  • Method for accelerating phase changing of bainite in steel through in-situ nanometer AlN heterogeneous nucleation

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Embodiment 1

[0013] A Fe-0.42C-1.5Si-1.8Mn-1.0Cr-0.3Mo-0.2Ni-0.1Al-0.01N steel, the rest is a small amount of impurities such as P and S, after the molten steel is smelted by an electric furnace, the molten steel is cast into a steel ingot , heat the steel ingot to 1200 °C for 5 hours, and then carry out the rolling thermal deformation of the steel ingot, the final deformation temperature is 900 °C, the deformation ratio is 8, and the deformation is divided into 8 times. AlN particles with a fraction of 0.1 vol.% uniformly distributed; heat the hot-formed billet to 950 °C, hold it for 2 h for austenitization, and then cool it to 350 °C at a cooling rate of 0.5 °C / s for 0.5 h. Air-cooled to room temperature; then heated to 350°C for 1 h and then air-cooled. The phase transformation time of the bainitic steel obtained by the above composition and treatment process is 0.5h, and the average thickness of the bainite lath is about 95nm.

[0014] figure 1 As shown in the figure, the kinetic cur...

Embodiment 2

[0016] A Fe-0.70C-2.6Si-0.70Mn-0.41Cr-0.15Al-0.013N steel, the rest is a small amount of impurities such as P and S. After smelting molten steel with an electric furnace, the molten steel is cast into a steel ingot, and the steel ingot is heated to 1230 ℃ for 3 hours, and then the steel ingot is subjected to rolling hot deformation, the final deformation temperature is 920 ℃, the deformation ratio is 6, and the deformation is divided into 6 times. Evenly distributed AlN particles; heat the hot-formed billet to 900°C, hold it for 1 hour for austenitization, then cool it to 350°C at a cooling rate of 0.7°C / s for 1 hour, and then cool it to room temperature in air; then heat it to 320℃ for 2h and then air-cooled. The phase transformation time of the bainitic steel obtained by the above composition and treatment process is 1h, and the average thickness of the bainite lath is about 60nm.

Embodiment 3

[0018] A Fe-1.0C-2.0Si-0.21Mn-1.51Cr-0.20Al-0.020N steel, the rest is a small amount of impurities such as P and S, after the molten steel is smelted by an electric furnace, the molten steel is cast into a steel ingot, and the steel ingot is heated to 1250 After holding at ℃ for 2 hours, the steel ingot is subjected to rolling hot deformation, the final deformation temperature is 910 ℃, the deformation ratio is 6, and the deformation amount is divided into 5 times. Uniformly distributed AlN particles; heat the hot-formed billet to 860°C, hold it for 3 hours for austenitization, then cool it to 230°C at a cooling rate of 0.2°C / s for 4 hours, and then cool it to room temperature in air; then heat it to 250 °C for 2 hours and then air-cooled. The phase transformation time of the bainitic steel obtained by the above composition and treatment process is 4h, and the average thickness of the bainite lath is about 50nm.

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Abstract

The invention discloses a method for accelerating phase changing of bainite in steel through in-situ nanometer AlN heterogeneous nucleation. The method is mainly characterized in that Al with the weight percent ranging from 0.1 to 0.2 and 100 ppm to 200 ppm of N are added into alloy steel, wherein the carbon content of the alloy steel ranges from 0.4 weight percent to 1.2 weight percent, the silicon content of the alloy steel ranges from 1.5 weight percent to 2.8 weight percent, and MnCrNiMo is contained in the alloy steel; and in the heat deformation and heat treatment process of the steel, AlN particles which are evenly distributed with the size ranging from 20 nm to 100 nm and the volume fraction ranging from 0.1 vol.% to 0.2 vol.% are separated out from the steel in an in-situ manner, the bainite phase changing time ranges from 0.5 h to 5 h, and a bainite batten with the thickness ranging from 30 nm to 100 nm is obtained. By means of the method, the bainite phase changing time is shortened by 1 time to 10 times; the bainite ferrite batten and a residual austenite film are smaller; and the bainite steel has more excellent welding performance.

Description

technical field [0001] The invention belongs to the technical field of materials, and particularly relates to a method for accelerating bainite transformation in steel. Background technique [0002] The addition of Si element to the steel can effectively inhibit the precipitation of cementite in the austenite during the bainite transformation, so as to obtain strip-shaped bainitic ferrite and thin-film or massive retained austenite structure. It is called carbide-free bainite structure. Compared with traditional bainite and martensite structures, carbide-free bainite can achieve a combination of high strength and high plasticity. The carbide-free bainite transformation is controlled by the diffusion rate of carbon at the bainite / austenite phase interface, and the bainite formation rate is relatively slow. It usually takes a long time for medium and high carbon steel to realize carbide-free bainite structure. The isothermal transition time of the method is relatively long, ...

Claims

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Application Information

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IPC IPC(8): C21D8/00C21D1/20C22C38/06C22C38/44C22C38/58C22C38/02C22C38/04C22C38/34
CPCC21D1/20C21D8/005C21D2211/002C22C38/001C22C38/02C22C38/04C22C38/06C22C38/34C22C38/44C22C38/58
Inventor 张福成杨志南吕博赵晓洁
Owner YANSHAN UNIV
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