Manufacturing method of lightweight high-strength magnesium alloy brake disc

Abstract

The invention relates to a manufacturing method of a lightweight high-strength magnesium alloy brake disc, and belongs to the technical field of brake disc manufacturing. Magnesium is put into a smelting furnace to be smelted, then aluminum, zinc, manganese, rare earth elements and silicon are sequentially added, and uniform magnesium alloy melt is formed through stirring and mixing; a sulfydryl-titanium coordination type refining agent is added into the magnesium alloy melt for refining treatment; after the melt is cooled, an Al-5Ti-1B intermediate alloy is added for modification treatment; magnesium alloy melt subjected to refining and modification treatment is poured into the preheated mold, and the magnesium alloy brake disc subjected to casting molding is subjected to solution treatment and aging treatment; the magnesium alloy brake disc subjected to heat treatment is subjected to surface treatment, and a layer of compact ceramic film is formed on the surface of the brake disc through a micro-arc oxidation technology; the prepared magnesium alloy brake disc has good mechanical properties and wear resistance, and can meet the use requirements of an automobile brake system.

Description

Technical Field

[0001] The present invention relates to the technical field of brake disc manufacturing, in particular to a manufacturing method of a lightweight and high-strength magnesium alloy brake disc. Background Art

[0002] With the rapid development of the automotive industry, the lightweight design of automobiles has become an important means to improve fuel economy and reduce emissions. As a key component of the automotive braking system, the performance of the brake disc directly affects the braking safety and driving experience of the vehicle. Traditional brake discs are mostly made of cast iron materials, which, although having good wear resistance and thermal stability, are relatively heavy and not conducive to the lightweight development of automobiles. Magnesium alloys have the advantages of low density, high specific strength, good damping performance, etc., and are ideal lightweight materials. However, there are still many challenges in applying magnesium alloys to brake disc manufacturing at present. For example, the high-temperature strength and wear resistance of magnesium alloys are relatively poor. During the braking process, a large amount of heat is generated in the brake disc, and the mechanical properties of magnesium alloys will significantly decline under high-temperature environments, resulting in a shortened service life of the brake disc and unstable braking performance. At the same time, the corrosion resistance of magnesium alloys also needs to be improved. They are prone to corrosion in humid and corrosive environments, affecting the safety of the brake disc. Therefore, it is of great practical significance to develop a magnesium alloy brake disc with both lightweight and high strength and its manufacturing method. Summary of the Invention

[0003] To solve the above problems, the present invention provides a manufacturing method of a lightweight and high-strength magnesium alloy brake disc, and its operation steps are as follows: S1 Prepare a magnesium alloy melt: Prepare 6 - 8% aluminum, 2 - 3% zinc, 0.3 - 0.5% manganese, 0.5 - 1% rare earth elements, 0.2 - 0.4% silicon, and the balance is magnesium raw materials; put magnesium into a furnace, heat it to 650 - 700 °C to melt it, and then add aluminum, zinc, manganese, rare earth elements, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add a mercapto-titanium coordination type refining agent accounting for 0.3 - 0.5% of the melt mass to the magnesium alloy melt for refining treatment to remove gases and impurities in the magnesium alloy melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 620 - 650 °C, add an Al-5Ti-1B master alloy accounting for 0.2 - 0.3% of the melt mass for modification treatment, stir evenly and then let it stand for 10 - 15 minutes; the modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold used for manufacturing the brake disc to 200 - 250 °C to reduce the heat loss of the magnesium alloy melt during the casting process and ensure the integrity of filling and the quality of the casting; S5 Casting and molding: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 2 - 3 m / s, and the pouring temperature is 630 - 660 °C; S6 Heat treatment: Perform solution treatment and aging treatment on the cast magnesium alloy brake disc; Through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Perform surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0004] As a preferred embodiment of the present invention, the rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0005] As a preferred embodiment of the present invention, the temperature of the refining treatment is 680 - 720 °C, and the refining time is 15 - 20 minutes.

[0006] As a preferred embodiment of the present invention, during the casting and molding process, the low-pressure casting method is adopted, and the pressure in the mold is maintained at 0.02 - 0.05 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as pores and shrinkage porosity.

[0007] As a preferred embodiment of the present invention, the solution treatment temperature is 410 - 430 °C, the holding time is 4 - 6 hours, and then it is rapidly water-cooled to room temperature.

[0008] As a preferred embodiment of the present invention, the aging treatment temperature is 170 - 190 °C, the holding time is 8 - 10 hours, and then it is air-cooled to room temperature.

[0009] As a preferred embodiment of the present invention, the voltage of the micro-arc oxidation is 300 - 400 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 20 - 30 minutes; the mass concentration of sodium silicate in the electrolyte is 10 - 20 g / L, and the mass concentration of sodium hydroxide is 5 - 15 g / L.

[0010] As a preferred embodiment of the present invention, the preparation method of the mercapto-titanium coordination type refining agent is: T1: Add 40 - 50 parts of magnesium mercaptoacetate, 1000 - 1500 parts of absolute ethanol, and 15 - 20 parts of titanyl sulfate into the reaction kettle, stir at 50 - 60 °C for 2 - 5 hours, and use the coordination reaction of TiO2 + and -SH to generate an intermediate; T2: Then add 1 - 4 parts of spherical polymethylsilsesquioxane resin and 150 - 200 parts of nano boron nitride, and ultrasonically disperse for 1 - 3 hours; after removing ethanol by vacuum distillation, vacuum dry at 80 - 100 °C for 4 - 6 hours, crush and pass through a 100 - mesh sieve to obtain a mercapto - titanium coordination type refining agent.

[0011] Reaction mechanism: Molecular design innovation: Through the dual action of Ti - O - S coordination bonds and Si - O - Ti covalent bonds, "active ingredient stabilization + functional group high - efficiency" is achieved.

[0012] Structural synergistic effect: The combination of the three - dimensional network of silsesquioxane and nano - BN solves the problems of fast high - temperature decomposition and poor dispersibility of traditional refining agents.

[0013] Multi - mechanism coupling: Integrate the three major functions of "impurity adsorption, grain refinement, and gas removal" into a single refining agent, breaking through the single - function limitation of traditional methods.

[0014] Synergistic mechanism of the refining process: "Adsorption - nucleation - degassing" triple effect.

[0015] Impurity adsorption: Mercapto radicals (·SH) form stable mercaptides with alkali metal ions such as K + , Na + in the melt, reducing their activity; titanium - sulfur complexes wrap MgO particles through coordination bonds, causing them to precipitate from the melt.

[0016] Grain refinement: The TiO2 nanocrystals decomposed from titanium - oxygen intermediates and nano boron nitride together serve as heterogeneous nucleation cores, increasing the nucleation rate and refining the grain size.

[0017] Gas removal: Methyl radicals (·CH3) generated by the decomposition of silsesquioxane react with hydrogen (H2) in the melt to form methane (CH4), promoting gas escape.

[0018] The manufacturing method of the lightweight and high - strength magnesium alloy brake disc of the present invention has the following beneficial effects compared with the prior art: 1. Breakthrough in impurity removal efficiency: The contents of inclusions such as MgO and Al2O3 are reduced, reducing internal defects in castings; the residual amounts of K and Na are reduced, avoiding corrosion cracking caused by grain boundary segregation.

[0019] 2. Significantly improved mechanical properties: By optimizing the composition of the magnesium alloy, adding alloying elements such as aluminum, zinc, manganese, rare earth elements, and silicon, and adopting special manufacturing processes, including refining treatment, modification treatment, heat treatment, etc., the grains of the magnesium alloy are refined and the strength of the alloy is improved.

[0020] 3. Excellent wear resistance and corrosion resistance: The ceramic film formed on the surface of the brake disc by micro-arc oxidation treatment has the advantages of good wear resistance and strong chemical stability, which can effectively improve the wear resistance and corrosion resistance of the brake disc and extend its service life. Detailed implementation manners

[0021] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in combination with examples and comparative examples.

[0022] Example 1: A manufacturing method of a lightweight and high-strength magnesium alloy brake disc, and its operation steps are as follows: S1 Prepare a magnesium alloy melt: Prepare 6% aluminum, 2% zinc, 0.3% manganese, 0.5% rare earth elements, 0.2% silicon, and the balance is magnesium raw materials; put magnesium into a furnace and heat it to 650 °C to melt it, and then add aluminum, zinc, manganese, rare earth elements, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add a mercapto-titanium coordination type refining agent accounting for 0.3% of the mass of the melt to the magnesium alloy melt for refining treatment to remove the gas and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 620 °C, add an Al-5Ti-1B master alloy accounting for 0.2% of the mass of the melt for modification treatment, stir evenly and then let it stand for 10 minutes; the modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold for manufacturing the brake disc to 200 °C to reduce the heat loss of the magnesium alloy melt during the pouring process and ensure the integrity of filling and the quality of the casting; S5 Pouring and forming: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 2 m / s, and the pouring temperature is 630 °C; S6 Heat treatment: Perform solution treatment and aging treatment on the poured and formed magnesium alloy brake disc; through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Perform surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc, and the ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0023] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0024] The refining temperature is 680 °C, and the refining time is 15 minutes.

[0025] During the pouring process, low-pressure casting is adopted to maintain the pressure in the mold at 0.02 MPa, enabling the magnesium alloy melt to better fill the mold cavity and reducing the generation of defects such as porosity and shrinkage porosity.

[0026] The solution treatment temperature is 410 °C, and the holding time is 4 hours, followed by rapid water cooling to room temperature.

[0027] The aging treatment temperature is 170 °C, and the holding time is 8 hours, followed by air cooling to room temperature.

[0028] The voltage of the micro-arc oxidation treatment is 300 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 20 minutes; the mass concentration of sodium silicate in the electrolyte is 10 g / L, and the mass concentration of sodium hydroxide is 5 g / L.

[0029] The preparation method of the mercapto-titanium coordination type refining agent is as follows: T1: Add 40 g of magnesium mercaptoacetate, 1000 g of absolute ethanol, and 15 g of titanyl sulfate to the reaction kettle, stir at 50 °C for 2 hours, and generate an intermediate through the coordination reaction of TiO2 + and -SH; T2: Then add 1 g of spherical polymethylsilsesquioxane resin and 150 g of nano boron nitride, and ultrasonically disperse for 1 hour; after removing ethanol by vacuum distillation, vacuum dry at 80 °C for 4 hours, crush and pass through a 100-mesh sieve to obtain the mercapto-titanium coordination type refining agent.

[0030] Example 2: The manufacturing method of a lightweight and high-strength magnesium alloy brake disc, and its operation steps are as follows: S1 Prepare magnesium alloy melt: Prepare 7% aluminum, 2.5% zinc, 0.4% manganese, 0.6% rare earth element, 0.3% silicon, and the balance is magnesium raw material; put magnesium into the furnace, heat it to 660 °C to melt it, and then add aluminum, zinc, manganese, rare earth element, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add 0.4% of the mercapto-titanium coordination type refining agent based on the mass of the melt to the magnesium alloy melt for refining treatment to remove the gas and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 630 °C, add 0.2% of the Al-5Ti-1B master alloy based on the mass of the melt for modification treatment, stir evenly and then stand for 12 minutes; the modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold for manufacturing the brake disc to 210 °C to reduce the heat loss of the magnesium alloy melt during the pouring process and ensure the integrity of filling and the quality of the casting; S5 Casting and molding: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 2 m / s, and the pouring temperature is 640 °C; S6 Heat treatment: Perform solution treatment and aging treatment on the cast magnesium alloy brake disc; Through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Perform surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0031] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0032] The refining temperature is 690 °C, and the refining time is 16 minutes.

[0033] During the pouring process, the low-pressure casting method is adopted to keep the pressure in the mold at 0.03 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as pores and shrinkage porosity.

[0034] The solution treatment temperature is 420 °C, the holding time is 5 hours, and then it is rapidly water-cooled to room temperature.

[0035] The aging treatment temperature is 180 °C, the holding time is 9 hours, and then it is air-cooled to room temperature.

[0036] The voltage of the micro-arc oxidation treatment is 350 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 25 minutes; the mass concentration of sodium silicate in the electrolyte is 15 g / L, and the mass concentration of sodium hydroxide is 10 g / L.

[0037] The preparation method of the mercapto-titanium coordination type refining agent is as follows: T1: Add 43 g of magnesium mercaptoacetate, 1200 g of absolute ethanol, and 16 g of titanyl sulfate to the reaction kettle, stir at 55 °C for 3 hours, and use the coordination reaction of TiO2 + and -SH to generate an intermediate; T2: Then add 2 g of spherical polymethylsilsesquioxane resin and 160 g of nano boron nitride, and ultrasonically disperse for 2 hours; After removing ethanol by vacuum distillation, vacuum dry at 90 °C for 5 hours, crush and pass through a 100-mesh sieve to obtain the mercapto-titanium coordination type refining agent.

[0038] Example 3: The manufacturing method of a lightweight and high-strength magnesium alloy brake disc, and its operation steps are as follows: S1 Preparation of magnesium alloy melt: Prepare 7% aluminum, 2.5% zinc, 0.4% manganese, 0.8% rare earth elements, 0.3% silicon, and the balance is magnesium raw materials; Put magnesium into a furnace and heat it to 680 °C to melt it, then add aluminum, zinc, manganese, rare earth elements, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add a mercapto-titanium coordination type refining agent accounting for 0.4% of the melt mass to the magnesium alloy melt for refining treatment to remove the gas and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 640 °C, add an Al-5Ti-1B master alloy accounting for 0.3% of the melt mass for modification treatment, stir evenly and then let it stand for 14 minutes; The modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold used for manufacturing the brake disc to 240 °C to reduce the heat loss of the magnesium alloy melt during the pouring process and ensure the integrity of filling and the quality of the casting; S5 Pouring and molding: Pour the magnesium alloy melt that has been refined and modified into the preheated mold at a pouring speed of 3 m / s, and the pouring temperature is 650 °C; S6 Heat treatment: Carry out solution treatment and aging treatment on the cast magnesium alloy brake disc; Through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Carry out surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0039] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0040] The refining temperature is 710 °C and the refining time is 18 minutes.

[0041] During the pouring process, the low-pressure casting method is adopted to keep the pressure in the mold at 0.04 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as pores and shrinkage porosity.

[0042] The solution treatment temperature is 420 °C, the holding time is 5 hours, and then it is quickly water-cooled to room temperature.

[0043] The aging treatment temperature is 180 °C, the holding time is 9 hours, and then it is air-cooled to room temperature.

[0044] The voltage of the micro-arc oxidation treatment is 350 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 25 minutes; the mass concentration of sodium silicate in the electrolyte is 15 g / L, and the mass concentration of sodium hydroxide is 10 g / L.

[0045] The preparation method of the mercapto-titanium coordination type refining agent is as follows: T1: Add 48 g of magnesium mercaptoacetate, 1400 g of absolute ethanol, and 18 g of titanyl sulfate into the reaction kettle, stir at 55 °C for 4 hours, and use the coordination reaction of TiO2 + and -SH to generate an intermediate; T2: Then add 3 g of spherical polymethylsilsesquioxane resin and 180 g of nano boron nitride, and ultrasonically disperse for 2 hours; after removing ethanol by vacuum distillation, vacuum dry at 90 °C for 5 hours, crush and pass through a 100-mesh sieve to obtain the mercapto-titanium coordination type refining agent.

[0046] Example 4: The manufacturing method of a lightweight high-strength magnesium alloy brake disc, and its operation steps are as follows: S1 Prepare the magnesium alloy melt: Prepare 8% aluminum, 3% zinc, 0.5% manganese, 1% rare earth element, 0.4% silicon, and the balance is magnesium raw material; put the magnesium into the furnace, heat it to 700 °C to melt it, and then add aluminum, zinc, manganese, rare earth element, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add 0.5% of the mercapto-titanium coordination type refining agent based on the mass of the melt to the magnesium alloy melt for refining treatment to remove the gas and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 650 °C, add 0.3% of the Al-5Ti-1B master alloy based on the mass of the melt for modification treatment, stir evenly and then stand for 15 minutes; the modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold for manufacturing the brake disc to 250 °C to reduce the heat loss of the magnesium alloy melt during the pouring process and ensure the integrity of filling and the quality of the casting; S5 Pouring and forming: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 3 m / s, and the pouring temperature is 660 °C; S6 Heat treatment: Perform solution treatment and aging treatment on the cast magnesium alloy brake disc; through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Perform surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0047] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0048] The refining temperature is 720 °C and the refining time is 20 minutes.

[0049] During the casting process, low-pressure casting is adopted to maintain the pressure in the mold at 0.05 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as pores and shrinkage porosity.

[0050] The solution treatment temperature is 430 °C, the holding time is 6 hours, and then it is rapidly water-cooled to room temperature.

[0051] The aging treatment temperature is 190 °C, the holding time is 10 hours, and then it is air-cooled to room temperature.

[0052] The voltage of the micro-arc oxidation treatment is 400 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 30 minutes; the mass concentration of sodium silicate in the electrolyte is 20 g / L, and the mass concentration of sodium hydroxide is 15 g / L.

[0053] The preparation method of the mercapto-titanium coordination type refining agent is as follows: T1: Add 50 g of magnesium mercaptoacetate, 1500 g of absolute ethanol, and 20 g of titanium oxysulfate to the reaction kettle, stir at 60 °C for 5 hours, and use the coordination reaction of TiO2 + and -SH to generate an intermediate; T2: Then add 4 g of spherical polymethylsilsesquioxane resin and 200 g of nano boron nitride, and ultrasonically disperse for 3 hours; after removing ethanol by vacuum distillation, vacuum dry at 100 °C for 6 hours, crush and pass through a 100-mesh sieve to obtain the mercapto-titanium coordination type refining agent.

[0054] Comparative Example 1: The manufacturing method of a lightweight and high-strength magnesium alloy brake disc, and its operating steps are as follows: S1 Prepare magnesium alloy melt: Prepare 6% aluminum, 2% zinc, 0.3% manganese, 0.5% rare earth elements, 0.2% silicon, and the balance is magnesium raw material; put magnesium into the furnace, heat it to 650 °C to melt it, and then add aluminum, zinc, manganese, rare earth elements, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add 0.3% of hexachloroethane based on the mass of the melt to the magnesium alloy melt for refining treatment to remove the gas and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification Treatment: Lower the temperature of the magnesium alloy melt to 620 °C, add an Al-5Ti-1B master alloy accounting for 0.2% of the melt mass for modification treatment, stir evenly and then let it stand for 10 minutes; the modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold Preheating: Preheat the mold used for manufacturing the brake disc to 200 °C to reduce the heat loss of the magnesium alloy melt during pouring, and ensure the integrity of filling and the quality of the casting; S5 Pouring and Forming: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 2 m / s, and the pouring temperature is 630 °C; S6 Heat Treatment: Carry out solution treatment and aging treatment on the cast magnesium alloy brake disc; through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface Treatment: Carry out surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0055] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0056] The refining temperature is 680 °C, and the refining time is 15 minutes.

[0057] During the pouring process, the low-pressure casting method is adopted, and the pressure in the mold is maintained at 0.02 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as porosity and shrinkage porosity.

[0058] The solution treatment temperature is 410 °C, the holding time is 4 hours, and then it is quickly water-cooled to room temperature.

[0059] The aging treatment temperature is 170 °C, the holding time is 8 hours, and then it is air-cooled to room temperature.

[0060] The voltage of the micro-arc oxidation treatment is 300 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 20 minutes; the mass concentration of sodium silicate in the electrolyte is 10 g / L, and the mass concentration of sodium hydroxide is 5 g / L.

[0061] Comparative Example 2: The manufacturing method of a lightweight and high-strength magnesium alloy brake disc, and its operation steps are as follows: S1 Preparation of Magnesium Alloy Melt: Prepare 6% aluminum, 2% zinc, 0.3% manganese, 0.5% rare earth elements, 0.2% silicon, and the balance is magnesium raw materials; put magnesium into a furnace, heat it to 650 °C to melt it, and then add aluminum, zinc, manganese, rare earth elements, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add a refining agent accounting for 0.3% of the mass of the magnesium alloy melt to the magnesium alloy melt for refining treatment to remove the gas and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 620 °C, add an Al-5Ti-1B master alloy accounting for 0.2% of the mass of the melt for modification treatment, stir evenly and then let it stand for 10 minutes; The modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold used for manufacturing the brake disc to 200 °C to reduce the heat loss of the magnesium alloy melt during the pouring process and ensure the integrity of filling and the quality of the casting; S5 Pouring and molding: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 2 m / s, and the pouring temperature is 630 °C; S6 Heat treatment: Perform solution treatment and aging treatment on the cast magnesium alloy brake disc; Through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Perform surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0062] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0063] The refining temperature is 680 °C, and the refining time is 15 minutes.

[0064] During the pouring process, the low-pressure casting method is adopted, and the pressure in the mold is maintained at 0.02 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as pores and shrinkage porosity.

[0065] The solution treatment temperature is 410 °C, the holding time is 4 hours, and then it is rapidly water-cooled to room temperature.

[0066] The aging treatment temperature is 170 °C, the holding time is 8 hours, and then it is air-cooled to room temperature.

[0067] The voltage of the micro-arc oxidation treatment is 300 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 20 minutes; The mass concentration of sodium silicate in the electrolyte is 10 g / L, and the mass concentration of sodium hydroxide is 5 g / L.

[0068] The preparation method of the refining agent is as follows: T1: Add 40 g of magnesium mercaptoacetate, 1000 g of absolute ethanol, and 15 g of titanyl sulfate to the reaction kettle, stir at 50 °C for 2 hours, and use TiO2+ Coordination reaction with -SH generates an intermediate; T2: Add another 150 g of nano boron nitride and ultrasonically disperse for 1 hour; After removing ethanol by vacuum distillation, vacuum dry at 80 °C for 4 hours, crush and pass through a 100-mesh sieve to obtain the refining agent.

[0069] Comparative Example 3: Manufacturing method of a lightweight high-strength magnesium alloy brake disc, the operating steps are as follows: S1 Preparation of magnesium alloy melt: Prepare 6% aluminum, 2% zinc, 0.3% manganese, 0.5% rare earth elements, 0.2% silicon, and the balance is magnesium raw material; Put magnesium into a furnace, heat it to 650 °C to melt it, and then add aluminum, zinc, manganese, rare earth elements, and silicon in sequence, stirring while adding to ensure that each element is fully mixed to form a uniform magnesium alloy melt; S2 Refining treatment: Add a refining agent accounting for 0.3% of the melt mass to the magnesium alloy melt for refining treatment to remove gases and impurities in the melt and improve the quality of the magnesium alloy; S3 Modification treatment: Lower the temperature of the magnesium alloy melt to 620 °C, add an Al-5Ti-1B master alloy accounting for 0.2% of the melt mass for modification treatment, stir evenly and then let it stand for 10 minutes; The modification treatment can refine the grains of the magnesium alloy and improve its mechanical properties; S4 Mold preheating: Preheat the mold used for manufacturing the brake disc to 200 °C to reduce the heat loss of the magnesium alloy melt during pouring and ensure the integrity of filling and the quality of the casting; S5 Pouring and forming: Pour the refined and modified magnesium alloy melt into the preheated mold at a pouring speed of 2 m / s, and the pouring temperature is 630 °C; S6 Heat treatment: Perform solution treatment and aging treatment on the cast magnesium alloy brake disc; Through heat treatment, the strength and hardness of the magnesium alloy brake disc can be further improved; S7 Surface treatment: Perform surface treatment on the heat-treated magnesium alloy brake disc, and use micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc. The ceramic film can significantly improve the wear resistance and corrosion resistance of the brake disc.

[0070] The rare earth elements are a mixture composed of yttrium, lanthanum, and cerium, and their mass ratio is 1:1:1.

[0071] The refining temperature is 680 °C and the refining time is 15 minutes.

[0072] During the pouring process, the low-pressure casting method is adopted, and the pressure in the mold is maintained at 0.02 MPa, so that the magnesium alloy melt can better fill the mold cavity and reduce the generation of defects such as porosity and shrinkage.

[0073] The solution treatment temperature is 410 °C, the holding time is 4 hours, and then it is rapidly water-cooled to room temperature.

[0074] The aging treatment temperature is 170 °C, the holding time is 8 hours, and then it is air-cooled to room temperature.

[0075] The voltage of the micro-arc oxidation treatment is 300 V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 20 minutes; the mass concentration of sodium silicate in the electrolyte is 10 g / L, and the mass concentration of sodium hydroxide is 5 g / L.

[0076] The preparation method of the refining agent is as follows: T1: Add 40 g of magnesium mercaptoacetate, 1000 g of absolute ethanol, and 15 g of titanyl sulfate into a reaction kettle, stir at 50 °C for 2 hours, and use the coordination reaction of TiO2 + and -SH to generate an intermediate; T2: Then add 1 g of spherical polymethylsilsesquioxane resin, ultrasonically disperse for 1 hour; after removing ethanol by vacuum distillation, vacuum dry at 80 °C for 4 hours, crush and pass through a 100-mesh sieve to obtain the refining agent.

[0077] 1. Tensile strength test: It is tested on an SSS-1120 electronic universal testing machine with reference to GB228.

[0078] 2. Linear wear rate test: It is tested using an MM-1000 type friction and wear testing machine.

[0079] The test results obtained through the above test methods are shown in Table 1 below.

[0080] Table 1: Test results of each example and comparative example

[0081] Through the data analysis of the above examples and comparative examples, the magnesium alloy brake disc prepared by the present invention has good mechanical properties and wear resistance, and can meet the use requirements of the automotive braking system.

[0082] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to form equivalent embodiments without departing from the technical solution scope of the present invention. However, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for manufacturing a lightweight high-strength magnesium alloy brake disc, characterized in that: The steps are: S1: preparing a magnesium alloy melt: preparing 6-8% aluminum, 2-3% zinc, 0.3-0.5% manganese, 0.5-1% rare earth elements, 0.2-0.4% silicon, and the balance being magnesium raw materials; placing magnesium in a furnace, heating it to 650-700°C to melt it, and then sequentially adding aluminum, zinc, manganese, rare earth elements, and silicon, stirring while adding to ensure that the elements are fully mixed to form a uniform magnesium alloy melt; S2 refining treatment: adding 0.3-0.5% of the mass of the melt of the magnesium alloy to a mercapto-titanium coordination type refining agent for refining treatment; S3 modification treatment: lower the temperature of the magnesium alloy melt to 620-650°C, add 0.2-0.3% of the mass of the melt Al-5Ti-1B master alloy to perform modification treatment, stir evenly and let stand for 10-15 minutes; S4 mold preheating: preheat the mold used to manufacture the brake disc to 200-250℃; S5 casting: the refined and modified magnesium alloy melt is poured into the preheated mold at a casting speed of 2-3m / s and the casting temperature is 630-660℃; S6 heat treatment: the cast magnesium alloy brake disc is subjected to solution treatment and aging treatment; S7 surface treatment: Surface treatment of heat-treated magnesium alloy brake discs, using micro-arc oxidation technology to form a dense ceramic film on the surface of the brake disc; The mercapto-titanium coordination type refining agent is obtained by reacting magnesium thioglycolate, titanyl sulfate, spherical polymethylsilsesquioxane resin and nano boron nitride.

2. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: The rare earth element is a mixture of yttrium, lanthanum and cerium, and the mass ratio thereof is 1:1:

1.

3. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: The refining temperature is 680-720°C and the refining time is 15-20 minutes.

4. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: During the casting process, low-pressure casting is adopted to maintain the pressure in the mold at 0.02-0.05 MPa.

5. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: The solution treatment temperature is 410-430° C., the heat preservation time is 4-6 hours, and then the solution is rapidly cooled to room temperature.

6. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: The aging treatment temperature is 170-190° C., the heat preservation time is 8-10 hours, and then air-cooled to room temperature.

7. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: The voltage of the micro-arc oxidation is 300-400V, the electrolyte is a mixed solution of sodium silicate and sodium hydroxide, and the treatment time is 20-30 minutes; the mass concentration of sodium silicate in the electrolyte is 10-20g / L, and the mass concentration of sodium hydroxide is 5-15g / L.

8. The method for manufacturing a lightweight and high-strength magnesium alloy brake disc according to claim 1, characterized in that: The preparation method of the mercapto-titanium coordination type refining agent is as follows: T1: Add 40-50 parts of magnesium thioglycolate, 1000-1500 parts of anhydrous ethanol, and 15-20 parts of titanyl sulfate into a reaction kettle, stir at 50-60°C for 2-5 hours, and use TiO2 + The coordination reaction with -SH generates an intermediate; T2: Add 1-4 parts of spherical polymethylsilsesquioxane resin and 150-200 parts of nano boron nitride, and disperse by ultrasonic for 1-3 hours; remove ethanol by vacuum distillation under reduced pressure, and vacuum dry at 80-100°C for 4-6 hours, and crush through a 100-mesh sieve to obtain a mercapto-titanium coordination refining agent.

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