阅读说明：本技术 马氏体钢深冷高压旋扭模具及方法 (Cryogenic high-pressure torque die and method for martensitic steel ) 是由 骆俊廷 肖遥 崔天伦 张丽丽 张春祥 于 2020-06-10 设计创作，主要内容包括：本发明公开马氏体钢深冷高压旋扭模具及方法,涉及高强度钢细晶处理技术领域,采用一种下模带有凹槽的模具,将USIBOR1500马氏体高强度钢板材装入下模的凹槽里的液氮中,上模下行压在板材上,向下模的凹槽中灌满液氮,然后把上模和下模之间进行密封,对试样进行深冷处理,处理时间为20min或30min；深冷处理后在4GPa或5GPa压力下高压旋扭,扭转角度为360°；将不同工艺深冷处理并进行高压旋扭后的USIBOR1500马氏体高强度钢板材再进行真空电场辅助再结晶退火处理,其温度为750℃,保温时间为20min,保温结束后空冷。最终制备出的USIBOR1500马氏体高强度钢晶粒为均匀的细小马氏体晶粒,其屈服强度、抗拉强度、延伸率均比处理前有所提高。(The invention discloses a cryogenic high-pressure torque-knob die and a method for martensitic steel, and relates to the technical field of high-strength steel fine grain treatment.A die with a groove on a lower die is adopted, a USIBOR1500 martensitic high-strength steel plate is loaded into liquid nitrogen in the groove of the lower die, an upper die descends to press on the plate, the groove of the lower die is filled with the liquid nitrogen, then the upper die and the lower die are sealed, and a sample is subjected to cryogenic treatment for 20min or 30 min; after the cryogenic treatment, high-pressure twisting is carried out under the pressure of 4GPa or 5GPa, and the twisting angle is 360 degrees; and (3) carrying out vacuum electric field assisted recrystallization annealing treatment on the USIBOR1500 martensite high-strength steel plate subjected to deep cooling treatment and high-pressure twisting by different processes, wherein the temperature is 750 ℃, the heat preservation time is 20min, and air cooling is carried out after the heat preservation is finished. The finally prepared USIBOR1500 martensite high-strength steel crystal grains are uniform and fine martensite crystal grains, and the yield strength, the tensile strength and the elongation are all improved compared with those before treatment.)

1. The cryogenic high-pressure torque die for the martensitic steel is characterized by comprising an upper die and a lower die, wherein a groove is formed in the upper surface of the lower die; after the lower part of the upper die is inserted into the groove, a gap is formed between the lower part of the upper die and the inner wall of the groove; and a sealing structure is arranged between the upper die and the lower die.

2. The martensitic steel cryogenic high-pressure knob die as claimed in claim 1, wherein the groove is a cylindrical groove.

3. The martensitic steel cryogenic high-pressure knob die as claimed in claim 1, wherein the sealing structure comprises a sealing ring, and the sealing ring is arranged at an opening of the groove.

4. The method for manufacturing the martensitic steel cryogenic high-pressure torsional mould based on any one of claims 1 to 3, is characterized by comprising the following steps of:

the method comprises the following steps: loading the USIBOR1500 martensite high-strength steel plate into the groove, pressing the upper die on the USIBOR1500 martensite high-strength steel plate downwards, filling liquid nitrogen into the groove, and sealing the upper die and the lower die;

step two: carrying out high-pressure twisting on the USIBOR1500 martensite high-strength steel plate subjected to deep cooling treatment in the step I under high pressure, and enabling the USIBOR1500 martensite high-strength steel plate to be subjected to compression deformation and shear deformation under the combined action of torque and pressure;

step three: and (4) placing the USIBOR1500 martensite high-strength steel plate treated in the step two on sintering equipment for electric field assisted recrystallization annealing treatment, and cooling in air after heat preservation is finished.

5. The cryogenic high-pressure torsional die of martensitic steel as claimed in claim 4, wherein the thickness of the USIBOR1500 martensitic high-strength steel plate in the first step is 1.5-2 mm.

6. The method for deeply cooling and high-pressure twisting the martensitic steel as claimed in claim 4, wherein the high pressure in the second step is 4GPa or 5GPa, and the twisting angle is 360 °.

7. The method for cryogenic high-pressure torque die of martensitic steel according to claim 4, wherein in the first step, the USIBOR1500 martensitic high-strength steel plate is cryogenically treated in liquid nitrogen for 20min or 30 min.

8. The method for manufacturing the martensitic steel cryogenic high-pressure torque die according to claim 4, wherein in the third step, the heating temperature of the USIBOR1500 martensitic high-strength steel plate is 750 ℃, and the heat preservation time is 20 min.

9. The method for manufacturing the martensitic steel cryogenic high-pressure knob die according to claim 4, wherein in the third step, the sintering equipment is spark plasma sintering equipment.

Technical Field

The invention relates to the technical field of high-strength steel fine grain treatment, in particular to a martensitic steel cryogenic high-pressure knob die and a method.

Background

Advanced high-strength steel is a material with a complex phase structure, achieves required chemical components and complex phase microstructure by strictly controlling heating and cooling processes, adopts various strengthening mechanisms to realize different strengths, ductility, toughness and fatigue properties, and is widely applied to the automobile industry. The USIBOR1500 high-strength steel is a commonly used high-strength steel material, and the steel can finally obtain martensite structure steel with the strength of more than 1500MPa through phase transformation.

The hot stamping forming process of the USIBOR1500 high-strength steel plate is researched by Zhule, and simultaneously, the condition for forming a martensite structure in a formed part in the hot stamping forming process is analyzed, so that the martensite phase transformation rule is obtained. However, no further studies have been made on the grain size uniformity of the USIBOR1500 martensitic high-strength steel, the shortening of the heat treatment time of the high-strength steel, and the like.

Disclosure of Invention

In order to solve the technical problems, the invention provides a cryogenic high-pressure torque die and a method for martensitic steel, so that the comprehensive mechanical property of the USIBOR1500 martensitic high-strength steel is improved, and the application of the USIBOR1500 martensitic high-strength steel in the engineering field is better met.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a martensitic steel cryogenic high-pressure knob die and a method, wherein the die comprises an upper die and a lower die, and the upper surface of the lower die is provided with a groove; after the lower part of the upper die is inserted into the groove, a gap is formed between the lower part of the upper die and the inner wall of the groove; and a sealing structure is arranged between the upper die and the lower die.

Optionally, the groove is a cylindrical groove.

Optionally, the sealing structure includes a sealing ring, and the sealing ring is disposed at the opening of the groove.

The invention also discloses a method for manufacturing the martensitic steel cryogenic high-pressure torque die, which is characterized by comprising the following steps of:

the method comprises the following steps: loading the USIBOR1500 martensite high-strength steel plate into the groove, pressing the upper die on the USIBOR1500 martensite high-strength steel plate downwards, filling liquid nitrogen into the groove, and sealing the upper die and the lower die;

step two: carrying out high-pressure twisting on the USIBOR1500 martensite high-strength steel plate subjected to deep cooling treatment in the step I under high pressure, and enabling the USIBOR1500 martensite high-strength steel plate to be subjected to compression deformation and shear deformation under the combined action of torque and pressure;

step three: and (4) placing the USIBOR1500 martensite high-strength steel plate treated in the step two on sintering equipment for electric field assisted recrystallization annealing treatment, and cooling in air after heat preservation is finished.

Optionally, the thickness of the USIBOR1500 martensite high-strength steel plate in the step one is 1.5-2 mm.

Optionally, in the second step, the high pressure is 4GPa or 5GPa, and the torsion angle is 360 °.

Optionally, in the first step, the cryogenic treatment time of the USIBOR1500 martensite high-strength steel plate in liquid nitrogen is 20min or 30 min.

Optionally, in the third step, the heating temperature of the USIBOR1500 martensite high-strength steel plate is 750 ℃, and the heat preservation time is 20 min.

Optionally, the sintering equipment in the third step is discharge plasma sintering equipment.

Compared with the prior art, the invention has the following technical effects:

1. the deep cooling treatment is adopted in advance, severe plastic deformation is carried out at the liquid nitrogen temperature, dynamic recovery can be effectively inhibited, dislocation can be effectively accumulated, dislocation cells or dislocation walls and other structures are formed, meanwhile, deformation twin crystals or shear bands are induced to be formed, the internal stress generated by deformation can reduce the recrystallization activation energy of the material, and the grain refinement degree is improved. Under the same strain, the degree of grain refinement of the deep-cooling deformation is higher than that of the room-temperature deformation. And the cryogenic treatment can reduce the residual austenite amount in the steel, separate out fine carbides in the structure and also play a role in improving the mechanical property of the steel.

2. The method comprises the steps of adopting a high-pressure torque process to generate severe plastic deformation on a USIBOR1500 martensite high-strength steel plate, enabling a martensite lath to be twisted and broken, accumulating a large amount of dislocation in the martensite lath to form sub-grains and dislocation cells, and then adopting a discharge plasma sintering process to perform electric field assisted recrystallization annealing treatment. The process has the characteristics of low voltage and high current, and can remarkably change the microstructure of the USIBOR1500 martensite high-strength steel. Under the action of pulse current, free ion discharge in the USIBOR1500 martensite high-strength steel generates heat, the temperature is rapidly raised, meanwhile, the nucleation points in the broken grains are increased, and then the grains are uniformly nucleated and grow up, and finally, a uniform and fine martensite grain structure is formed.

3. The USIBOR1500 martensite high-strength steel treated by the method has excellent comprehensive mechanical property, the crystal grains are uniform and fine martensite crystal grains, the yield strength, the tensile strength and the elongation are all improved compared with those before treatment, the further improvement of the mechanical property of the USIBOR1500 martensite high-strength steel can be realized, and the application of the USIBOR1500 martensite high-strength steel in the engineering field can be better met.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic diagram of a martensitic steel cryogenic high-pressure knob die in the invention.

In the figure: 1. the device comprises an upper die, 2, a lower die, 3, a sealing structure, 4, liquid nitrogen, 5 and a sample.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.