Alloy die steel and preparation method thereof

Abstract

The invention discloses alloy die steel and a preparation method thereof, and the alloy die steel comprises the following components in percentage by mass: 0.3%-0.4% of C, 0.2%-0.5% of S , 0.3%-0.6% of Mn, 1.0%-1.3% of Cr, 0.08%-0.15% of Mo, 2.5%-3.0% of N , less than or equal to 0.03% of P, less than or equal to 0.03% of S, 1.5%-2.5% of a carbon fiber-aluminum-based composite material and the balance of Fe. The content of the polytetrafluoroethylene-silicon nitride composite material is 0.8%-1.2%, and the balance is Fe. According to the alloy die steel and the preparation method thereof, the carbon fiber-aluminum-based composite material and the polytetrafluoroethylene-silicon nitride composite material are introduced into the die steel, and the carbon fiber-aluminum-based composite material enhances the strength, modulus and wear resistance of the die steel; the polytetrafluoroethylene-silicon nitride composite material endows the die steel with good self-lubricating property, low friction coefficient and high temperature resistance, expensive rare metal elements are not used in the formula, the main raw materials are wide in source and relatively stable in price, the preparation process is relatively simple, the production cost is reduced, and the market competitiveness of the product is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of die steel, and particularly relates to an alloy die steel and a preparation method thereof. Background Art

[0002] Die steel plays a crucial role in industrial production and is widely used in multiple fields such as automobiles, electronics, aerospace, etc. With the continuous development of modern industry, the performance requirements for die steel are increasing day by day. It not only needs to have high strength, high hardness, good wear resistance, but also requires excellent high-temperature resistance, corrosion resistance, and good processing performance.

[0003] Currently, the existing die steels on the market have certain limitations in some performances. Some die steels have high hardness but insufficient wear resistance, and are prone to problems such as wear and scratches during frequent use, affecting the service life of the die and the quality of products; some die steels have poor high-temperature resistance, and their mechanical properties will significantly decline when working in a high-temperature environment, resulting in die deformation or even failure; and some die steels have complex processing processes and high costs. Summary of the Invention

[0004] The main purpose of the present invention is to provide an alloy die steel and a preparation method thereof, which have excellent comprehensive performance, relatively reasonable cost, and simple processing technology.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] An alloy die steel, the mass percentages of each component are calculated as follows: C is 0.3% - 0.4%, Si is 0.2% - 0.5%, Mn is 0.3% - 0.6%, Cr is 1.0% - 1.3%, Mo is 0.08% - 0.15%, Ni is 2.5% - 3.0%, the content of P is not more than 0.03%, the content of S is not more than 0.03%, the content of carbon fiber - aluminum matrix composite material is 1.5% - 2.5%, the content of polytetrafluoroethylene - silicon nitride composite material is 0.8% - 1.2%, and the balance is Fe;

[0007] In the carbon fiber - aluminum matrix composite material, the volume fraction of carbon fiber is 30%, and the carbon fiber length is 15 μm, the diameter is 10 nm, and the aluminum substrate is high-purity aluminum with a purity not less than 99.5%;

[0008] In the polytetrafluoroethylene - silicon nitride composite material, the mass percentage of polytetrafluoroethylene is 50%, and the average particle size of silicon nitride is 75 nm.

[0009] Preferably, the mass percentages of the components of the alloy die steel are calculated as follows: C is 0.35%, Si is 0.35%, Mn is 0.47%, Cr is 1.13%, Mo is 0.13%, Ni is 2.72%, P is 0.02%, S is 0.02%, the content of carbon fiber-aluminum matrix composite material is 2.1%, the content of polytetrafluoroethylene-silicon nitride composite material is 0.95%, and the balance is Fe;

[0010] In the carbon fiber-aluminum matrix composite material, the volume fraction of carbon fiber is 25%, and the length of the carbon fiber is 13 μm and the diameter is 7 nm. The aluminum matrix material is high-purity aluminum with a purity of not less than 99.5%;

[0011] In the polytetrafluoroethylene-silicon nitride composite material, the mass percentage of polytetrafluoroethylene is 45%, and the average particle size of silicon nitride is 80 nm.

[0012] The present invention also discloses a method for preparing the above die steel, and the specific steps are as follows:

[0013] Step 1: Accurately weigh the raw materials of each component according to the formula to ensure that the quality of all raw materials meets the requirements, and there is no scale and impurities on the surface of the metal raw materials;

[0014] Step 2: Take carbon fiber and aluminum base material to prepare a carbon fiber-aluminum matrix composite material mixture;

[0015] Step 3: Take polytetrafluoroethylene and silicon nitride to prepare a polytetrafluoroethylene-silicon nitride composite material mixture;

[0016] Step 4: Put all the weighed raw materials except Ni into a vacuum induction melting furnace and melt at a temperature of 1600 °C. After the metal raw materials are completely melted into a liquid state, add the weighed Ni into the metal liquid and stir evenly;

[0017] Step 5: Add the carbon fiber-aluminum matrix composite material and the polytetrafluoroethylene-silicon nitride composite material into the melted metal liquid in sequence, and stir for 20 min under the condition of 450 r / min by electromagnetic stirring to form a uniform alloy liquid;

[0018] Step 6: Pour the alloy liquid into a mold preheated to 250 °C, and use centrifugal casting to cast into a die steel blank. The casting speed is 1000 r / min, and the casting time is 15 min;

[0019] Step 7: After the die steel blank is subjected to three heat treatments, it is machined. After being machined into the required shape and size, it is polished so that the surface roughness of the die steel reaches Ra0.8-Ra1.6 μm to obtain a finished alloy die steel part.

[0020] Preferably, the specific steps for subjecting the mold steel blank to three heat treatments are as follows:

[0021] S71. Place the mold steel blank in a vacuum heat treatment furnace, and heat it at a heating rate of 8 °C / min to 600 °C, hold for 60 min, then cool it in the furnace to 300 °C, and then take it out and air-cool it to room temperature;

[0022] S72. Place the mold steel blank that has undergone the first heat treatment back into the heating furnace, heat it at a heating rate of 5 °C / min to 450 °C, hold for 20 min; then heat it at a heating rate of 12 °C / min to 890 °C, hold for 1.5 h; take it out and quickly put it into oil for quenching, control the temperature of the quenching oil at 40 °C, the quenching time is 15 min, and then let it stand to room temperature;

[0023] S73. Place the quenched mold steel blank in a tempering furnace, heat it at a heating rate of 6 °C / min to 420 °C, hold for 60 min, and then naturally cool it to room temperature.

[0024] Preferably, in step 2, the specific steps for preparing the carbon fiber-aluminum matrix composite mixture are as follows:

[0025] S21. Heat the aluminum substrate to the molten state, then add the prepared carbon fiber into it, and use a double-helix blade stirrer to stir at a temperature of 700 °C and a rotation speed of 1200 r / min for 20 minutes;

[0026] S22. After stirring, put the fused material into another induction furnace, and cool it naturally under the protection of argon, and keep the temperature at 350 °C through the induction furnace for standby.

[0027] Preferably, in step 3, the specific steps for preparing the polytetrafluoroethylene-silicon nitride composite material and performing pretreatment are as follows:

[0028] S31. Take the weighed silicon nitride powder, add methylene chloride with a mass ratio of 1:2 as a dispersion solvent, and use an ultrasonic disperser for dispersion;

[0029] S32. Add the weighed polytetrafluoroethylene powder into the dispersed silicon nitride solution, and use a ball mill for mixing, set the rotation speed at 500 rpm, and the ball milling time at 2 hours;

[0030] S33. Put the mixed liquid into an oven, set the drying temperature at 60 °C, and keep it for 8 - 12 h to complete the preliminary drying and solvent removal treatment, and then transfer it to a vacuum chamber and dry it at 80 °C for 5 h to obtain the polytetrafluoroethylene-silicon nitride composite material for standby.

[0031] Preferably, when using an ultrasonic disperser for dispersion, the frequency is controlled at 22 kHz and the dispersion time is 30 min.

[0032] Preferably, when drying the polytetrafluoroethylene-silicon nitride composite material again in a vacuum chamber, the initial pressure value is controlled at 50 mbar, and after drying for 2 h, it is reduced to 20 mbar.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Through reasonable composition design, the alloy die steel of the present invention introduces carbon fiber-aluminum matrix composite material and polytetrafluoroethylene-silicon nitride composite material into the die steel, combining the advantages of each component; the carbon fiber-aluminum matrix composite material enhances the strength, modulus and wear resistance of the die steel; the polytetrafluoroethylene-silicon nitride composite material endows the die steel with good self-lubricity, low friction coefficient and high temperature resistance.

[0035] 2. In the die steel formula of the present invention, expensive rare metal elements are not used, the main raw materials are widely sourced and the prices are relatively stable; at the same time, the preparation process is relatively simple, without the need for complex equipment and special process conditions, reducing production costs and improving the market competitiveness of products. In the preparation process, processes such as centrifugal casting and vacuum heat treatment are mature and reliable and are easy to control; through reasonable process parameter settings, the quality stability and consistency of the die steel can be effectively guaranteed, facilitating large-scale industrial production. Specific embodiments

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The present invention discloses an alloy die steel and a preparation method thereof, which are prepared according to the following steps:

[0038] Step 1. Accurately weigh the following raw materials according to the formula, specifically: C is 0.3% - 0.4%, Si is 0.2% - 0.5%, Mn is 0.3% - 0.6%, Cr is 1.0% - 1.3%, Mo is 0.08% - 0.15%, Ni is 2.5% - 3.0%, the content of P is not more than 0.03%, the content of S is not more than 0.03%, the content of carbon fiber-aluminum matrix composite material is 1.5% - 2.5%, the content of polytetrafluoroethylene-silicon nitride composite material is 0.8% - 1.2%, and the balance is Fe. Ensure that the quality of all raw materials meets the requirements and there is no oxide scale or impurity on the surface of the metal raw materials;

[0039] Among them, in the carbon fiber-aluminum matrix composite material, the volume fraction of carbon fiber is 30%, and the carbon fiber length is 15 μm, the diameter is 10 nm, and the aluminum substrate is high-purity aluminum with a purity of not less than 99.5%;

[0040] In the polytetrafluoroethylene-silicon nitride composite material, the mass percentage of polytetrafluoroethylene is 50%, and the average particle size of silicon nitride is 75 nm;

[0041] Step 2: Take carbon fiber and aluminum substrate to prepare a carbon fiber-aluminum matrix composite material mixture; the specific preparation steps are as follows:

[0042] S21: After heating the aluminum substrate to the molten state, add the prepared carbon fiber into it, and use a double-screw blade stirrer to stir at a temperature of 700 °C and a rotation speed of 1200 r / min for 20 minutes;

[0043] S22: After stirring is completed, put the fused material into another induction furnace, and cool it naturally under the protection of argon, and keep the temperature at 350 °C through the induction furnace for standby;

[0044] Step 3: Take polytetrafluoroethylene and silicon nitride to prepare a polytetrafluoroethylene-silicon nitride composite material mixture; the specific preparation steps are as follows: S31: Take the weighed silicon nitride powder, add methylene chloride with a mass ratio of 1:2 as a dispersion solvent, and use an ultrasonic disperser for dispersion;

[0045] S32: Add the weighed polytetrafluoroethylene powder into the dispersed silicon nitride solution, and use a ball mill for mixing, set the rotation speed to 500 rpm, and the ball milling time to 2 hours;

[0046] S33: Put the mixed liquid into an oven, set the drying temperature to 60 °C, and keep it for 8 - 12 h to complete the preliminary drying and solvent removal treatment, then transfer it to a vacuum box and dry it at 80 °C for 5 h to obtain the polytetrafluoroethylene-silicon nitride composite material for standby.

[0047] Step 4: Put all the weighed raw materials except Ni into a vacuum induction melting furnace, and carry out melting at a temperature of 1600 °C. After the metal raw materials are completely melted into a liquid state, add the weighed Ni into the metal liquid and stir evenly;

[0048] Step 5: Add the carbon fiber-aluminum matrix composite material and the polytetrafluoroethylene-silicon nitride composite material into the melted metal liquid in sequence, and stir for 20 min under the condition of 450 r / min by electromagnetic stirring to form a uniform alloy liquid;

[0049] Step 6: Pour the alloy liquid into a mold preheated to 250 °C, and use centrifugal casting to cast it into a mold steel blank. The casting speed is 1000 r / min, and the casting time is 15 min;

[0050] Step 7: After subjecting the mold steel billet to three heat treatments, perform machining. After machining it into the required shape and size, grind and polish it to make the surface roughness of the mold steel reach Ra0.8 - Ra1.6 μm, thus obtaining the finished alloy mold steel part;

[0051] Specifically, the method of the three heat treatments is as follows: S71: Place the mold steel billet in a vacuum heat treatment furnace, and heat it up to 600 °C at a heating rate of 8 °C / min, hold for 60 min, then cool it in the furnace to 300 °C, and then take it out and air-cool it to room temperature;

[0052] S72: Place the mold steel billet that has undergone the first heat treatment back into the heating furnace, heat it up to 450 °C at a heating rate of 5 °C / min, hold for 20 min; then heat it up to 890 °C at a heating rate of 12 °C / min, hold for 1.5 h; take it out and quickly put it into oil for quenching, control the temperature of the quenching oil at 40 °C, the quenching time is 15 min, and then let it stand to room temperature;

[0053] S73: Place the quenched mold steel billet in a tempering furnace, heat it up to 420 °C at a heating rate of 6 °C / min, hold for 60 min, and then naturally cool it to room temperature.

[0054] The present invention will be further disclosed below in conjunction with specific examples and comparative examples.

[0055] The following table shows the component raw material ratios for preparing mold steel in Examples 1 - 5 and Comparative Examples 1 - 2:

[0056]

[0057]

[0058] It should be noted here that in Comparative Examples 1 - 2, carbon fiber - aluminum matrix composite material and polytetrafluoroethylene - silicon nitride composite material are not added respectively. The other component ratios are the same as those in Example 3. At the same time, its preparation steps only lie in not adding carbon fiber - aluminum matrix composite material and polytetrafluoroethylene - silicon nitride composite material, and the other preparation steps are also the same as the preparation steps disclosed in the present invention.

[0059] Respectively take the alloy mold steel samples prepared in the above Examples 1 - 5 and Comparative Examples 1 - 2 for the following tests:

[0060] I. Wear resistance test: The test is carried out in accordance with GB / T 12444-2019 "Test methods for wear of metallic materials - Part 1: Pin-on-disc wear test". This standard stipulates the principles, equipment, specimens, test procedures, and result representation of the pin-on-disc wear test. In this test, a die steel pin specimen with a diameter of 6 mm and a length of 30 mm is selected and rubbed against a GCr15 steel disc with a hardness of HRC60. The test parameters are set as follows: load 100 N, rotational speed 200 r / min, test time 60 min. The test is carried out at room temperature, and the environmental humidity is controlled at 50% ± 5%.

[0061] II. Lubricity test: Refer to GB / T 3142-1982 "Method for determination of load-carrying capacity of lubricants (four-ball method)" and combine it with the friction coefficient test to evaluate the lubricity. The four-ball method is mainly used to determine the extreme pressure performance and anti-wear performance of lubricants, and it is evaluated by measuring the friction coefficient and wear scar diameter between steel balls under specified conditions. At the same time, a friction coefficient measuring instrument is used to measure the friction coefficient of the die steel surface on the pin-disc friction pair. The test conditions are: load 50 N, rotational speed 150 r / min, test time 30 min, and test temperature is room temperature.

[0062] III. Yield strength test at 400°C: It is carried out in accordance with GB / T 4338-2015 "Test methods for high-temperature tension of metallic materials". This standard stipulates the requirements for the principles, equipment, specimens, test procedures, and result processing of the tensile test of metallic materials at high temperatures. A standard tensile specimen with a circular cross-section is used, with a gauge length of 50 mm and a parallel length of 60 mm. The test is carried out on a high-temperature tensile testing machine, and the heating rate is controlled at 5°C / min. After reaching 400°C, it is held for 10 min, and then the tensile test is carried out at a strain rate of 0.0025 / s.

[0063] The results of the above three performance tests are shown in the following table:

[0064]

[0065] From the above results, it can be seen that among the samples prepared in Examples 1-5 of the present invention, with reference to the test results of GB / T 12444-2019 "Test methods for wear of metallic materials - Part 1: Pin-on-disc wear test", their relative wear amounts are all lower than 0.65%. In particular, the wear resistance test results of the samples prepared with the component ratios in Example 3 are the best, and the wear amount is only 0.5%. In the lubricity test, the friction coefficients are all lower than 0.12. In particular, the lubricity test results of the samples prepared with the component ratios in Example 3 are the best, and the friction coefficient is only 0.09. In the yield strength test at 400°C, the tensile pressures are all higher than 640 MPa. In particular, the yield strength test results of the samples prepared with the component ratios in Example 3 are the best, and the tensile pressure is as high as 680 MPa.

[0066] In addition, it can also be seen from the above test results that since the carbon fiber-aluminum matrix composite material was not added in Comparative Example 1, its wear resistance was significantly affected. In Example 2, since the polytetrafluoroethylene-silicon nitride composite material was not added, its friction coefficient and tensile resistance were also significantly affected. Thus, it can be proved that the carbon fiber-aluminum matrix composite material enhances the strength, modulus and wear resistance of die steel; the polytetrafluoroethylene-silicon nitride composite material endows die steel with good self-lubricity, low friction coefficient and high temperature resistance.

[0067] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An alloy die steel, characterized in that: The mass percentage of each component of the alloy die steel is calculated as follows: C is 0.3% to 0.4%, Si is 0.2% to 0.5%, Mn is 0.3% to 0.6%, Cr is 1.0% to 1.3%, Mo is 0.08% to 0.15%, Ni is 2.5% to 3.0%, P content is not more than 0.03%, S content is not more than 0.03%, carbon fiber-aluminum matrix composite material content is 1.5% to 2.5%, polytetrafluoroethylene-silicon nitride composite material content is 0.8% to 1.2%, and the balance is Fe; In the carbon fiber-aluminum-based composite material, the volume fraction of the carbon fiber is 30%, and the carbon fiber length is 15 μm, the diameter is 10 nm, and the aluminum substrate is high-purity aluminum with a purity of not less than 99.5%; In the polytetrafluoroethylene-silicon nitride composite material, the mass percentage of polytetrafluoroethylene is 50%, and the average particle size of silicon nitride is 75 nm.

2. The alloy die steel according to claim 1, characterized in that: The mass percentage of each component of the alloy die steel is calculated as follows: C is 0.35%, Si is 0.35%, Mn is 0.47%, Cr is 1.13%, Mo is 0.13%, Ni is 2.72%, P is 0.02%, S is 0.02%, the content of carbon fiber-aluminum matrix composite material is 2.1%, the content of polytetrafluoroethylene-silicon nitride composite material is 0.95%, and the balance is Fe; In the carbon fiber-aluminum-based composite material, the volume fraction of the carbon fiber is 25%, and the carbon fiber length is 13 μm and the diameter is 7 nm. The aluminum-based material is high-purity aluminum with a purity of not less than 99.5%; In the polytetrafluoroethylene-silicon nitride composite material, the mass percentage of polytetrafluoroethylene is 45%, and the average particle size of silicon nitride is 80 nm.

3. A method for preparing the alloy die steel according to any one of claims 1 to 2, characterized in that: The specific preparation steps are as follows: Step 1. Accurately weigh the raw materials of each component according to the formula to ensure that the quality of all raw materials meets the requirements and there is no oxide scale or impurities on the surface of the metal raw materials; Step 2, taking carbon fiber and aluminum substrate to prepare a carbon fiber-aluminum matrix composite material mixed solution; Step 3, taking polytetrafluoroethylene and silicon nitride to prepare a tetrafluoroethylene-silicon nitride composite material mixed solution; Step 4: Put all the weighed raw materials except Ni into a vacuum induction melting furnace and melt them at a temperature of 1600° C. After the metal raw materials are completely melted into liquid, add the weighed Ni into the molten metal and stir evenly; Step 5, adding the carbon fiber-aluminum-based composite material and the tetrafluoroethylene-silicon nitride composite material to the smelted metal liquid in sequence, stirring at 450 r / min for 20 minutes by electromagnetic stirring to form a uniform alloy liquid; Step 6, pouring the alloy liquid into a mold preheated to 250° C., and casting it into a mold steel blank by centrifugal casting, with a casting speed of 1000 r / min and a casting time of 15 min; Step 7: After the mold steel blank is subjected to three heat treatments, it is machined into the required shape and size and then polished to make the mold steel surface roughness reach Ra0.8-Ra1.6μm to obtain a finished alloy mold steel part.

4. The method for preparing alloy die steel according to claim 3, characterized in that: The specific steps of performing three heat treatments on the die steel blank are: S71, placing the mold steel blank into a vacuum heat treatment furnace, heating it to 600°C at a heating rate of 8°C / min, keeping it at that temperature for 60 minutes, then cooling it to 300°C with the furnace, and then taking it out and air cooling it to room temperature; S72, put the mold steel blank that has undergone the first heat treatment into the heating furnace again, heat it to 450°C at a heating rate of 5°C / min, and keep it warm for 20 minutes; then heat it to 890°C at a heating rate of 12°C / min, and keep it warm for 1.5 hours; after taking it out, quickly put it into oil for quenching, the temperature of the quenching oil is controlled at 40°C, the quenching time is 15 minutes, and then let it stand until it reaches room temperature; S73. The quenched mold steel blank is placed in a tempering furnace, heated to 420°C at a heating rate of 6°C / min, kept at this temperature for 60 minutes, and then naturally cooled to room temperature.

5. The method for preparing alloy die steel according to claim 3, characterized in that: In step 2, the specific steps of preparing the carbon fiber-aluminum-based composite material mixed solution are: S21, after heating the aluminum substrate to a molten state, adding the prepared carbon fiber thereto, and stirring at a temperature of 700° C. and a speed of 1200 r / min for 20 minutes using a double helical blade stirrer; S22. After the stirring is completed, the fused material is placed in another induction furnace and cooled naturally under the protection of argon gas, and the temperature is maintained at 350° C. by the induction furnace for standby use.

6. The method for preparing alloy die steel according to claim 3, characterized in that: In step 3, the specific steps of preparing the tetrafluoroethylene-silicon nitride composite material and pretreating it are: S31, taking the weighed silicon nitride powder, adding dichloromethane with a mass ratio of 1:2 as a dispersing solvent, and dispersing it using an ultrasonic disperser; S32, adding the weighed tetrafluoroethylene powder to the dispersed silicon nitride solution, mixing using a ball mill, setting the speed to 500 rpm, and the ball milling time to 2 hours; S33, putting the mixed liquid into an oven, setting the drying temperature to 60°C, and drying for 8-12 hours to complete the preliminary drying and desolventizing treatment, then transferring it into a vacuum box and drying it at 80°C for 5 hours to obtain a tetrafluoroethylene-silicon nitride composite material for use.

7. The method for preparing alloy die steel according to claim 6, characterized in that: When an ultrasonic disperser is used for dispersion, the control frequency is 22 kHz and the dispersion time is 30 minutes.

8. The method for preparing alloy die steel according to claim 6, characterized in that: When the tetrafluoroethylene-silicon nitride composite material is dried again in the vacuum box, the initial pressure value is controlled to be 50 mbar, and after drying for 2 hours, it is reduced to 20 mbar.

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