CN108300949B - A method of distributing bundled bainite orientation in steel - Google Patents

Abstract

A method of orienting the distribution of bundled bainite in steel. In the present invention, the steel billet smelted by the intermediate frequency vacuum induction furnace is cast into a steel ingot, and then forged into a plate at a high temperature. The steel is heated to 1000-1050°C, kept for 20-30min, oil-cooled to 240-260°C, kept for 20-30min, and then water-cooled to room temperature, through the temperature gradient field formed inside the steel during cooling to obtain bundled bainite Orientation distribution steel, its composition and content: C is 0.84wt.%-0.90wt.%; Si is 1.34wt.%-1.45wt.%; Mn is 0.35wt.%-0.40wt.%; Cr is 0.95wt.% .%-1.10wt.%; P<0.02wt.%;S<0.02wt.%; the rest is Fe. The invention has the characteristics of low cost, short cycle, simple process and high production efficiency. The prepared bundled bainitic steel has a tensile strength of 1700-2100 MPa, and can be used in construction machinery, highways, bridges and other fields.

Description

A method of distributing bundled bainite orientation in steel

technical field

The invention belongs to the technical field of metal materials, and particularly relates to a bainitic steel and a preparation method thereof.

Background technique

In the 1930s, Bain and Davenprot obtained the bainite structure through mesothermal transformation. Since then, bainite structures with various morphologies have been discovered by scholars from all over the world. It has greatly promoted the practical application of bainitic steel in engineering. In 2002, Bhadeshia et al. obtained bundled bainite by changing the chemical composition of steel, so that the steel material obtained an excellent combination of strength, toughness and ductility, which further aroused people's enthusiasm for low-temperature bainite research. However, due to the long isothermal time at medium temperature and the low production efficiency, it is difficult for bundled bainitic steel to be applied on a large scale in industry.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and to produce a bundled bainitic steel with orientation distribution characteristics by utilizing the temperature gradient field. The method has the advantages of simple production process, short period and low production cost, and the prepared bundled bainitic steel has excellent mechanical properties.

Technical solution of the present invention

A beam-shaped bainitic steel with orientation distribution obtained through a temperature gradient field, the mass percentage of its chemical composition is: C is 0.84wt.%-0.90wt.%; Si is 1.34wt.%-1.45wt.%; Mn is 0.35wt.%-0.40wt.%; Cr is 0.95wt.%-1.10wt.%; P<0.02wt.%; S<0.02wt.%; the rest are Fe and inevitable impurities.

The method for making bundled bainite orientation distribution in steel provided by the present invention comprises the following steps:

(1) Cast the steel billet containing the above-mentioned components smelted in the intermediate frequency vacuum induction furnace into a steel ingot, and then forge it into a plate at a high temperature of 1050-1100 ° C; cut the plate into a thickness of 5-10mm and a length and width of 50mm. steel.

(2) Heating the steel to 1000°C-1050°C, holding the temperature for 20-30min, cooling the oil to 240-260°C, holding the temperature for 20-30min, cooling to room temperature with water, and obtaining the oriented steel through the temperature gradient field formed inside the steel during cooling. Distribution characteristic of bundled bainitic steels.

In the present invention, a large temperature gradient is formed in the thickness direction of the sample through a thinner sample, so as to have a relatively large driving force in the thickness direction, and can increase the nucleation rate of bundled bainite, thereby increasing the number of bundles. The number of bainite and the fascicle bainite have the characteristics of orientation distribution. This greatly increases the mechanical properties of bundled bainitic steels.

Advantages and beneficial effects of the present invention:

1. Through the thinner thickness, a larger temperature gradient is formed in the thickness direction when the steel is subjected to medium temperature isothermal. Under the action of a large temperature gradient field, the bundled bainite structure can obtain a large phase transformation driving force during the medium temperature transformation, so that the bundled bainite structure has a large nucleation rate and has the characteristics of orientation distribution. . The mechanical properties of the bundled bainite steel are greatly increased, and the productivity of the bundled bainite steel is improved.

2. The bundled bainitic steel formed under the action of a large temperature gradient field has good mechanical properties, and the tensile strength can reach 1700-2100MPa.

3. Under the action of the temperature gradient field, the mesothermal isothermal time of the bundled bainite is short, which can improve the production efficiency and reduce the cost.

4. The production process is simple and the application prospect is wide. Can be widely used in highways, bridges, marine facilities shipbuilding and other fields.

Description of drawings

Fig. 1 is a metallographic photograph of the sample obtained in Example 1 of the present invention, and the characteristics of the orientation arrangement of bundled bainite can be observed.

FIG. 2 is a metallographic photograph of the sample obtained in Example 2 of the present invention, and it can be observed that the characteristics of the orientation arrangement of bundled bainite can be observed.

Detailed ways

Example 1:

The high-carbon silicon-containing steel is smelted in a vacuum induction furnace, and the chemical composition mass percentage of the high-carbon silicon-containing steel is: C is 0.88wt.%; Si is 1.36wt.%; Mn is 0.38wt.%; Cr is 1.01wt.% %; P<0.02wt.%; S<0.02wt.%; the rest is Fe.

The smelted steel ingot with the above-mentioned component content is forged into a plate at a high temperature of 1050°C. The sheet was machined into steel with a thickness of 5 mm and a length and width of 50 mm by wire cutting. The steel was heated to 1000°C, kept for 20 minutes, oil-cooled to 240°C for 20 minutes, and then water-cooled to room temperature. The tensile strength of the prepared steel was 2100 MPa. FIG. 1 is a photo of the metallographic structure of the oriented bundled bainite obtained after the high carbon silicon-containing steel of the present invention is subjected to the above-mentioned experimental conditions.

Example 2:

The high-carbon silicon-containing steel is smelted in a vacuum induction furnace, and the chemical composition mass percentage of the high-carbon silicon-containing steel is: C is 0.89wt.%; Si is 1.39wt.%; Mn is 0.36wt.%; Cr is 0.96wt.%. %; P<0.02wt.%; S<0.02wt.%; the rest is Fe.

The smelted steel ingot with the above-mentioned component content is forged into a plate at a high temperature of 1080°C. The sheet was machined by wire cutting into steel with a thickness of 7 mm and a length and width of 50 mm. The steel was heated to 1020°C, kept for 30 minutes, oil-cooled to 260°C for 30 minutes, and then water-cooled to room temperature. The tensile strength of the prepared steel was 1950 MPa. FIG. 2 is a photograph of the metallographic structure of the oriented bundled bainite obtained after the high carbon silicon-containing steel of the present invention is subjected to the above-mentioned experimental conditions.

Claims (2)

1. A bundled bainite steel with orientation distribution obtained by a temperature gradient field, characterized in that the chemical composition mass percentage of the bundled bainite steel is: C is 0.84wt.%-0.88wt.%; Si is 1.34wt.%-1.45wt.%; Mn is 0.35wt.%-0.40wt.%; Cr is 0.95wt.%-1.10wt.%; P<0.02wt.%; S<0.02wt.%; the rest It is Fe and inevitable impurities; The method for obtaining bundled bainitic steel with orientation distribution through temperature gradient field, the steps are as follows: (1) Cast the molten steel of the chemical composition smelted in the intermediate frequency vacuum induction furnace into a steel ingot, and then forge it into a plate at a high temperature of 1050-1100 °C; the plate is processed by wire cutting into a thickness of 5-10mm, and the length and width are equal. 50mm steel sample; (2) Heating the steel sample to 1000°C-1050°C, holding the temperature for 20-30min, cooling the oil to 240-260°C and holding the temperature for 20-30min, and then cooling it to room temperature with water, and obtained by the temperature gradient field formed inside the steel sample during cooling A steel with a bundled bainite structure characterized by an orientation distribution. 2. a method for making bundled bainite orientation distribution in steel, characterized in that the steps are as follows: (1) Cast the molten steel containing the composition of claim 1 smelted in the intermediate frequency vacuum induction furnace into a steel ingot, and then forge it into a plate at a high temperature of 1050-1100 ° C; the plate is processed by wire cutting to a thickness of 5-10mm and long Steel samples with a width of 50mm; (2) Heating the steel sample to 1000°C-1050°C, holding the temperature for 20-30min, cooling the oil to 240-260°C and holding the temperature for 20-30min, and then cooling it to room temperature with water, and obtained by the temperature gradient field formed inside the steel sample during cooling A steel with a bundled bainite structure characterized by an orientation distribution.

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