Die casting process for copper retainer

Abstract

The invention relates to the technical field of bearing manufacturing, in particular to a copper retainer die-casting process which comprises the following steps: firstly, mixing electrolytic copper, tin and zinc with rare earth yttrium, nano silicon carbide and graphene nanosheets, and performing vacuum melting and degassing to prepare a composite alloy; the mold is subjected to laser cladding and supersonic spraying to form a gradient coating; the alloy melt is subjected to high-speed mold filling under ultrasonic vibration, and pulse pressure is applied for pressure maintaining; gradient cooling is conducted after forming, and then two-step aging and pressure stress treatment are conducted; and finally, surface nanocrystallization treatment is carried out through ion implantation and ultrasonic shot blasting, and the performance is improved. The material utilization rate is increased to be larger than or equal to 92%, energy consumption is reduced, the tensile strength of the product is larger than or equal to 400 MPa, abrasion resistance is improved, the size precision is high, and the method is environmentally friendly and suitable for high-end bearing manufacturing.

Description

Technical Field

[0001] The invention relates to the technical field of bearing manufacturing, in particular to a copper retainer die-casting process. Background Art

[0002] As a core component of bearing assemblies, the manufacturing process of copper retainers directly affects the precision, lifespan, and reliability of bearings. Traditional copper retainers utilize a "smelting-centrifugal casting-cutting" process, which has the following significant drawbacks: Low material utilization: During centrifugal casting, the solidification shrinkage of copper alloys is as high as 5-8%, and a large amount of machining allowance must be reserved. Material utilization is generally less than 30%, generating over 700kg of scrap copper per ton of product, resulting in a waste of resources. Inadequate mechanical properties: Copper sleeves prepared using traditional processes have a coarse structure (grain size ≥50μm), a tensile strength of only around 250MPa, and an elongation of ≤8%, which cannot meet the material strength and toughness requirements of high-speed bearings. Limited production efficiency: Centrifugal casting requires multiple processes such as sand mold preparation, smelting, casting, and subsequent cutting. The production cycle for a single batch is as long as 24 hours, and a large amount of manual operation is required, making automated mass production difficult. Environmental pressure is prominent: Sand casting produces a large amount of waste sand (3-5 tons of waste sand per ton of product), the cost of waste acid treatment is high, and the energy consumption is as high as 800kWh / ton, which is not in line with the trend of green manufacturing.

[0003] The limitations of existing die-casting technology include a single alloy design: Traditional die-cast copper alloys are primarily based on the Cu-Sn-Zn system, lacking nanoscale reinforcement phases and unable to enhance performance through microstructural manipulation. For example, in alloys without rare earth elements, impurity elements (such as Fe and Pb) tend to form hard and brittle phases, leading to product cracking.

[0004] Short mold life: Copper alloy has a high melting point (1083℃) and poor fluidity. During die casting, the mold is subjected to high temperature and high pressure (≥100MPa). Conventional H13 steel molds are prone to sticking and thermal fatigue cracking. The lifespan is only 5000-8000 times, and frequent mold repairs are required.

[0005] Insufficient molding precision: Traditional die-casting has a low filling speed (≤5m / s), which makes it difficult to fill complex cavities, resulting in incomplete molding of features such as retainer windows and bosses, with dimensional tolerances ≥±0.05mm, requiring subsequent grinding and correction.

[0006] (1) Technical problems solved

[0007] In view of the deficiencies of the prior art, the present invention provides a copper retainer die-casting process.

[0008] (2) Technical solution

[0009] A copper retainer die-casting process comprises the following steps:

[0010] S1: Composite copper alloy preparation

[0011] Electrolytic copper, tin, and zinc are mixed in a mass ratio of 82-84:9-11:6-7, and 0.8-1.2% of the rare earth element yttrium Y, 0.3-0.7% of nano-silicon carbide, and 0.1-0.3% of graphene nanosheets are added to the alloy, and the mixture is melted at 1150-1180° C. in a vacuum melting furnace, and nitrogen containing 5-10 vol% of hydrogen is introduced for degassing.

[0012] S2: Mold pretreatment and gradient coating preparation

[0013] The surface of H13 mold steel is laser clad and pre-deposited with WC-Co alloy powder to form a hard base layer with a thickness of 80-120 μm. Subsequently, a composite coating containing 15-25wt% molybdenum disulfide MoS2, 8-12wt% graphene and 2-4wt% hexagonal boron nitride h-BN is sprayed by high-velocity flame, with a total coating thickness of 15-25 μm.

[0014] S3: Vacuum die casting-ultrasonic vibration composite molding

[0015] The composite copper alloy melt is heated to 1220-1280°C, ultrasonic vibration of 20-40kHz is applied in the injection cylinder, and the melt is injected into the mold cavity at an injection speed of 8-12m / s. At the same time, a pulse pressure of 100-150MPa is applied to the mold cavity.

[0016] S4: Gradient cooling and composite aging treatment

[0017] After forming, the mold is first cooled to 150°C at a rate of 100-150°C / min, held for 30 minutes, and then cooled to room temperature at a rate of 20-50°C / min. The copper retainer is then aged in a nitrogen atmosphere in two steps: first at 180°C for 1.5 hours and then at 280°C for 2 hours. At the same time, a constant compressive stress of 50-100 MPa is applied to promote the coordinated precipitation of Y2O3 and Cu3Sn strengthening phases. The reaction formula is:

[0018]

[0019] S5: Surface nanocrystallization-ion implantation composite treatment

[0020] Magnetron sputtering ion implantation technology is used to implant nitrogen ions on the surface of the copper retainer, and ultrasonic shot peening is performed at the same time. The shot peening medium is diamond shot. The processing time is 8-12 minutes to form a gradient nano layer with a thickness of 30-60μm.

[0021] Preferably, the method further includes a pretreatment step of mixing nano-silicon carbide and graphene nanosheets in a mass ratio of 2:1, ultrasonically dispersing the nanosheets with deionized water-ethanol, adding 0.5-1.0wt% of a silane coupling agent KH-560 for surface modification to form a uniformly dispersed nano-slurry, and compounding the nano-slurry with a copper alloy melt after drying, with a grafting rate of ≥95%.

[0022] Preferably, the process of melt filling is also monitored in real time in S3: the surface temperature field of the mold is monitored by an infrared thermal imager, and when the filling front temperature is 20-30°C lower than the liquidus temperature, the local heating system of the mold is automatically triggered.

[0023] Preferably, a transition layer is provided between the bottom layer and the surface layer of the gradient coating in S2, and the transition layer is composed of WC-Co-MoS2 composite powder and has a thickness of 20-40 μm.

[0024] Preferably, the constant compressive stress in S4 is applied by a piezoelectric ceramic actuator built into the mold cavity, with a stress control accuracy of ±5 MPa, so that the strengthening phase is precipitated along the grain boundaries.

[0025] Preferably, the in-plane orientation degree of the graphene nanosheets in the prepared copper retainer is ≥85%, and is observed by scanning electron microscopy to be distributed in layers at the grain boundaries, forming a "nano-enhanced network".

[0026] Preferably, the ion implantation in S5 works in synergy with ultrasonic shot peening to achieve a surface residual compressive stress of 200-300 MPa.

[0027] Preferably, the material utilization rate of the entire process is ≥92%, and the unit product energy consumption is ≤450 kWh / ton.

[0028] Preferably, the dimensional tolerance of the manufactured copper retainer is ≤±0.008 mm, and the surface roughness Ra is ≤0.6 μm.

[0029] Preferably, the graphene nanosheets introduced into the composite copper alloy can capture vacancy defects generated during the solidification process of the alloy, reducing the dislocation density to 10 10 / cm 2 the following.

[0030] (3) Beneficial effects

[0031] Compared with the existing technology, the beneficial effects of the present invention are:

[0032] 1. The tensile strength of the nanocomposite alloy is ≥400MPa, the elongation is low, and the bending strength is 550MPa. It can withstand the centrifugal force under high-speed rotation (speed ≥20,000rpm). The synergistic strengthening effect of Y2O3 and graphene increases the dislocation slip resistance and the fracture toughness is improved to 25MPa·m 1 / 2, which is significantly improved compared to traditional alloys. Wear resistance is significantly enhanced: the surface nanocrystalline layer (grain size ≤ 50nm) has a hardness of ≥ 400HV, combined with the copper nitride layer (Cu3N) formed by ion implantation, the friction coefficient is reduced to 0.08, the wear rate is only 1 / 5 of that of traditional processes, and the service life is extended. Dimensional accuracy and stability: Gradient aging treatment basically eliminates casting stress, dimensional tolerance ≤ ± 0.008mm, thermal expansion coefficient ≤ 18×10 -6 / ℃, meeting the precision maintenance requirements of aerospace bearings in extreme environments (-50℃~150℃).

[0033] 2. The die-casting process does not require large-scale cutting, resulting in extremely high material utilization, an improvement over traditional centrifugal casting. It saves 620kg of copper per ton of product, significantly reducing costs. Production cycles are significantly shortened: Integrated die-casting replaces "casting + multi-process processing," compressing single-batch production time. Combined with an automated part retrieval system, production capacity is increased to meet the needs of large-scale customized production. Mold life and energy consumption advantages: Gradient-coated molds significantly improve thermal fatigue resistance, with a lifespan of over 20,000 cycles, reducing downtime for mold repairs. The total process energy consumption is ≤450kWh / ton, lower than traditional processes, and there is no waste sand discharge, reducing environmental costs.

[0034] 3. Ultrasonic vibration die-casting technology can form precision retainers with window diameters ≤ 2mm and wall thicknesses ≤ 1.5mm, achieving a mold fill integrity of ≥ 99% and a surface roughness of Ra ≤ 0.6μm. These retainers can be directly used in aircraft engine bearings, eliminating the need for grinding. Green Manufacturing Features: A sandless die-casting process achieves "zero waste sand" production; the nanocomposite alloy is fully recyclable, and nitrogen-hydrogen mixed atmosphere degassing technology during production reduces harmful gas emissions, complying with EU RoHS environmental standards.

[0035] 4. The combined addition of rare earth yttrium and graphene solves the challenges of difficult nanophase dispersion and weak interfacial bonding. Modification with a silane coupling agent creates a strong interfacial bond (Si-O-Cu bond), enhancing phase retention to ≥98%. Intelligent process control: Infrared thermal imaging monitors the filling temperature field in real time, and combined with a local heating system, dynamically adjusts the mold temperature to ensure high-quality filling of complex structures, resulting in higher product yields compared to traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a copper retainer die casting process flow chart;

[0037] Figure 2 is a bar chart comparing energy consumption and production costs of the embodiment and the comparative example;

[0038] Figure 3 is a line graph comparing the elongation and wear rate of the embodiment and the comparative example;

[0039] Figure 4It is a bar graph comparing the tensile strength and surface roughness of the embodiment and the comparative example. DETAILED DESCRIPTION

[0040] according to Figures 1 to 4 , the specific implementation methods of the present invention are as follows:

[0041] 1. Materials and Equipment Preparation

[0042] Raw material specifications: Electrolytic copper must be ≥99.95% pure, Cu-CATH-1 grade, supplied by Jiangxi Copper; Tin must be ≥99.8% pure, Sn99.85, supplied by Yunnan Tin; Zinc must be ≥99.5% pure, Zn99.5, supplied by Zhuzhou Metallurgical Group; Rare earth yttrium (Y) must be ≥99.9% pure, particle size ≤50μm, prepared by Baotou Rare Earth Research Institute; Nano-silicon carbide particle size 30-40nm, purity ≥99%, purchased from Nanjing Apre Nanomaterials Co., Ltd.; Graphene nanosheets must be 5-10nm thick, sheet diameter 1 -5μm, produced by Changzhou Sixth Element Materials Technology Co., Ltd.; silane coupling agent KH-560 with a purity of ≥98% is supplied by Nanjing Shuguang Chemical Group; WC-Co alloy powder with a particle size of 50-100μm and a Co content of 12wt% is from Zigong Cemented Carbide Co., Ltd.; molybdenum disulfide (MoS2) with a purity of ≥99% and a particle size of ≤2μm is provided by Shanghai Aladdin Biochemical Technology Co., Ltd.; hexagonal boron nitride (h-BN) with a purity of ≥99% and a particle size of ≤1μm is purchased from Panjin Xinji Chemical Co., Ltd.

[0043] Main equipment: ZG-25 vacuum melting furnace, with working temperature ≤1600℃ and ultimate vacuum degree 10 -4 Pa; JP-5000 supersonic flame spraying equipment, flame speed ≥2000m / s; J11350 CNC die-casting machine, clamping force 3500kN, injection speed 0-15m / s; CZ-40 ultrasonic vibration device, frequency 20-40kHz, amplitude 0-50μm; FLIR A655sc infrared thermal imager, temperature range -20℃-2000℃, accuracy ±0.03℃; MEVVA-80 ion implanter, ion energy 50-200keV; USSP-100 ultrasonic shot peening equipment, frequency 30-50kHz, pressure 0-2MPa.

[0044] 2. Example 1: Standard Process Preparation

[0045] Formula (by mass)

[0046] Step S0: 0.5 parts by mass of nano-silicon carbide, 0.25 parts by mass of graphene nanosheets, and 0.0075 parts by mass of silane coupling agent KH-560, mixed with 10 L of deionized water-ethanol mixed solution (volume ratio 1:1).

[0047] Step S1: 83 parts by mass of electrolytic copper, 10 parts by mass of tin, 6.5 parts by mass of zinc, 1.0 part by mass of rare earth yttrium (Y), and pretreated nanocomposite powder.

[0048] S2 step (mold coating):

[0049] Hard bottom layer: WC-Co alloy powder (particle size 50-100μm), thickness 100μm;

[0050] Transition layer: WC-Co-MoS2, thickness 30μm;

[0051] Composite surface layer: MoS2 20wt%, graphene 10wt%, h-BN 3wt%, thickness 20μm.

[0052] Step S3: nitrogen-hydrogen mixed gas (volume ratio 95:5, purity 99.999%).

[0053] Step S5: Nitrogen ion implantation dose 10 17 ions / cm 2 , with diamond pellets of 0.1mm particle size.

[0054] Preparation steps

[0055] S0 preprocessing

[0056] 0.5 kg of nano-silicon carbide and 0.25 kg of graphene nanosheets were added to a 10 L deionized water-ethanol (volume ratio 1:1) mixed solution and ultrasonically dispersed (power 500 W, frequency 40 kHz) for 45 minutes. 0.0075 kg of silane coupling agent KH-560 was slowly added dropwise, stirred at 60 ° C for 3 hours, and then dried at 120 ° C for 12 hours to obtain a surface-modified nanocomposite powder. By Fourier transform infrared spectroscopy (FTIR) detection, the surface of the nanocomposite powder was 1080 cm -1 The characteristic peak of Si-OC bond appeared at , which proved that the coupling agent was successfully grafted. The grafting rate was determined by thermogravimetric analysis (TGA) to be 96.3%.

[0057] Preparation of S1 composite copper alloy

[0058] 83kg of electrolytic copper, 10kg of tin, and 6.5kg of zinc were added to a vacuum melting furnace and heated to 1150°C for melting. 1.0kg of rare earth yttrium and pretreated nanocomposite powder were added, and a mixture of nitrogen (99.999% purity) and hydrogen (99.999% purity) (95:5 by volume) was introduced for degassing at a rate of 5 L / min for 18 minutes. Rotary jet degassing reduced the hydrogen content from an initial 0.0025wt% to 0.0008wt%. The melt temperature was controlled at 1180°C and held for 30 minutes to ensure uniform dispersion of the nanophase.

[0059] S2 mold pretreatment and coating preparation

[0060] The surface of H13 mold steel was laser clad using a pre-set powder method with WC-Co alloy powder (particle size 50-100μm). A laser power of 4kW, a scanning speed of 5mm / s, and a 40% overlap ratio were used to form a hard base layer with a thickness of 100μm. A WC-Co-MoS2 transition layer (30μm thick) and a MoS2-graphene-h-BN composite surface layer (20μm thick) were then applied using supersonic flame spraying. Spraying process parameters included an oxygen flow rate of 1200L / min, a propane flow rate of 300L / min, a powder feed rate of 40g / min, and a spray distance of 120mm. The coating's bond strength, as measured by tensile testing, was 85MPa, with a porosity of 1.2%.

[0061] S3 Vacuum die casting-ultrasonic vibration composite molding

[0062] The composite copper alloy melt is heated to 1250°C and poured into the injection cylinder of the die-casting machine. During the injection process, 30kHz ultrasonic vibration (amplitude 20μm) is applied, and the mold cavity is filled at an injection speed of 10m / s. At the same time, a pulse pressure of 120MPa (frequency 8Hz) is applied to the mold cavity and the pressure is maintained for 30 seconds. The mold temperature is controlled at 230°C by a microchannel cooling system, and the cavity vacuum is evacuated to 25Pa. The filling process is monitored in real time by an infrared thermal imager. The filling time is 0.25 seconds and the temperature drop is ≤15°C.

[0063] S4 gradient cooling and composite aging treatment

[0064] After die-casting, the mold was rapidly cooled to 150°C at a rate of 120°C / min, held for 30 minutes, and then cooled to room temperature at a rate of 30°C / min. The copper retainer was placed in a nitrogen-protected aging furnace, first held at 180°C for 1.5 hours, then raised to 280°C and held for 2 hours. At the same time, a constant compressive stress of 80 MPa was applied by the piezoelectric ceramic actuator built into the mold. X-ray diffraction (XRD) analysis showed that the diffraction peak intensity of the Y2O3 phase was significantly enhanced after aging, indicating that the strengthening phase was fully precipitated.

[0065] S5 surface nanostructured and ion implanted composite treatment

[0066] The copper holder was placed in an ion implanter and nitrogen ions were implanted at an energy of 50 keV with a dose of 10 17 ions / cm 2Ultrasonic shot peening was also performed using 0.1mm diamond shot at a pressure of 1.0 MPa, a frequency of 40 kHz, and a treatment time of 10 minutes. Scanning electron microscopy (SEM) observations revealed the formation of a gradient nanolayer with a thickness of approximately 45 μm, and a surface grain size of ≤50 nm.

[0067] 3. Example 2: High-performance process preparation

[0068] formula

[0069] Step S0: 0.7 parts by mass of nano-silicon carbide, 0.3 parts by mass of graphene nanosheets, and 0.0075 parts by mass of silane coupling agent KH-560, mixed with 10 L of deionized water-ethanol mixed solution (volume ratio 1:1).

[0070] Step S1: 83 parts by mass of electrolytic copper, 10 parts by mass of tin, 6.5 parts by mass of zinc, 1.2 parts by mass of rare earth yttrium (Y), and pretreated nanocomposite powder.

[0071] S2 step (mold coating):

[0072] Hard bottom layer: WC-Co alloy powder (particle size 50-100μm), thickness 100μm;

[0073] Transition layer: WC-Co-MoS2, thickness 30μm;

[0074] Composite surface layer: MoS2 25wt%, graphene 12wt%, h-BN 4wt%, thickness 20μm.

[0075] Step S3: nitrogen-hydrogen mixed gas (volume ratio 95:5, purity 99.999%).

[0076] Step S5: Nitrogen ion implantation dose 10 18 ions / cm 2 , with diamond shot of 0.1mm particle size, ultrasonic shot peening pressure of 1.0MPa and frequency of 40kHz.

[0077] Preparation steps

[0078] S0 preprocessing

[0079] 0.7 kg of nano-silicon carbide and 0.3 kg of graphene nanosheets were added to a 10 L deionized water-ethanol (volume ratio 1:1) mixed solution and ultrasonically dispersed (power 500 W, frequency 40 kHz, power increased by 20%) for 45 minutes. 0.0075 kg of silane coupling agent KH-560 was slowly added dropwise, stirred at 60 ° C for 3 hours, and then dried at 120 ° C for 12 hours to obtain a surface-modified nanocomposite powder. By Fourier transform infrared spectroscopy (FTIR) detection, the surface of the nanocomposite powder was 1080 cm-1 The characteristic peak of Si-OC bond appeared at , which proved that the coupling agent was successfully grafted. The grafting rate was determined by thermogravimetric analysis (TGA) to be 96.3%.

[0080] Preparation of S1 composite copper alloy

[0081] 83kg of electrolytic copper, 10kg of tin, and 6.5kg of zinc were added to a vacuum melting furnace and heated to 1150°C for melting. 1.2kg of rare earth yttrium and pretreated nanocomposite powder were added, and a mixture of nitrogen (99.999% purity) and hydrogen (99.999% purity) (volume ratio 95:5) was introduced, degassing at a flow rate of 5L / min for 18 minutes. The hydrogen content was reduced from an initial 0.0025wt% to 0.0008wt% by rotary jet degassing. The melt temperature was controlled at 1180°C for 30 minutes, combined with high-intensity ultrasonic vibration (power increased by 20%) to ensure uniform dispersion of the nanophase (nanophase spacing was reduced from 180nm to 150nm).

[0082] S2 mold pretreatment and coating preparation

[0083] The surface of H13 mold steel was laser clad using a pre-set powder method. WC-Co alloy powder (50-100 μm in size) was pre-deposited at a laser power of 4 kW, a scanning speed of 5 mm / s, and a 40% overlap ratio to form a 100 μm-thick hard base layer. A 30 μm-thick WC-Co-MoS transition layer and a 20 μm-thick MoS-graphene-h-BN composite top layer (composed of 25 wt% MoS, 12 wt% graphene, and 4 wt% h-BN) were then applied using supersonic flame spraying. Spraying parameters included an oxygen flow rate of 1200 L / min, a propane flow rate of 300 L / min, a powder feed rate of 40 g / min, and a spray distance of 120 mm. The resulting coating exhibited a tensile strength of 85 MPa, a porosity of 1.2%, a reduced friction coefficient of 0.025, and an increased thermal conductivity of 85 W / (m·K).

[0084] S3 Vacuum die casting-ultrasonic vibration composite molding

[0085] The composite copper alloy melt is heated to 1250°C and poured into the injection cylinder of the die-casting machine. During the injection process, 40kHz ultrasonic vibration (amplitude 25μm) is applied, and the mold cavity is filled at an injection speed of 12m / s. Simultaneously, a pulse pressure of 150MPa (frequency 8Hz) is applied to the mold cavity and maintained for 30 seconds. The mold temperature is controlled at 230°C by a microchannel cooling system, and the cavity vacuum is evacuated to 25Pa. Filling time is shortened to 0.2 seconds, and the casting density reaches 99.8%.

[0086] S4 gradient cooling and composite aging treatment

[0087] After die-casting, the mold is first rapidly cooled to 150°C at a rate of 120°C / min, held for 30 minutes, and then cooled to room temperature at a rate of 30°C / min. The copper retainer is placed in a nitrogen-protected aging furnace, first kept at 180°C for 1.5 hours, then heated to 300°C and kept for 2 hours. At the same time, a constant compressive stress of 100MPa is applied through the piezoelectric ceramic actuator built into the mold. X-ray diffraction (XRD) analysis shows that the diffraction peak intensity of the Y2O3 phase is significantly enhanced after aging, and the strengthening phase is fully precipitated (Y2O3 particle size is controlled at 60-70nm).

[0088] S5 surface nanostructured and ion implanted composite treatment

[0089] The copper holder was placed in an ion implanter and nitrogen ions were implanted at an energy of 80 keV with a dose of 10 18 ions / cm 2 Ultrasonic shot peening was also performed, using 0.1mm diamond shot at a pressure of 1.0 MPa, a frequency of 40 kHz, and a treatment time of 10 minutes. Scanning electron microscopy (SEM) revealed the formation of a gradient nanolayer with a thickness of approximately 45 μm, a surface grain size of ≤50 nm, an increase in surface hardness to 450 HV, and a residual compressive stress of 280 MPa.

[0090] Example 3: Low-cost process preparation

[0091] formula

[0092] Step S0: 0.5 parts by mass of nano-silicon carbide, 0.5 parts by mass of expanded graphite (sheet diameter 5-10 μm), and 0.0075 parts by mass of silane coupling agent KH-560, mixed with 10 L of deionized water-ethanol mixed solution (volume ratio 1:1).

[0093] Step S1: 83 parts by mass of electrolytic copper, 10 parts by mass of tin, 6.5 parts by mass of zinc, 1.0 part by mass of rare earth yttrium (Y), and pretreated nanocomposite powder.

[0094] S2 step (mold coating):

[0095] Hard bottom layer: WC-Co alloy powder (particle size 50-100μm), thickness 100μm;

[0096] Transition layer: WC-Co-MoS2, thickness 30μm;

[0097] Composite surface layer: MoS2 15wt%, graphite powder (particle size ≤ 2μm) 10wt%, h-BN 3wt%, thickness 20μm.

[0098] Step S3: nitrogen-hydrogen mixed gas (volume ratio 95:5, nitrogen purity 99.9%).

[0099] Step S5: Nitrogen ion implantation dose 5×10 16 ions / cm 2 , with diamond shots of 0.1mm particle size, shot peening pressure 1.0MPa, frequency 40kHz, and processing time 8 minutes.

[0100] Preparation steps

[0101] S0 preprocessing

[0102] 0.5 kg of nano-silicon carbide and 0.5 kg of expanded graphite (5-10 μm flake diameter) were added to 10 L of a deionized water-ethanol (1:1 volume ratio) mixture and ultrasonically dispersed (500 W, 40 kHz) for 45 minutes. 0.0075 kg of silane coupling agent KH-560 was slowly added dropwise. The mixture was stirred at 60°C for 3 hours and then dried at 120°C for 12 hours to obtain a surface-modified nanocomposite powder. Raman spectroscopy revealed a D-to-G peak intensity ratio (ID / IG) of 0.85, confirming that some graphite exfoliation occurred.

[0103] Preparation of S1 composite copper alloy

[0104] 83kg of electrolytic copper, 10kg of tin, and 6.5kg of zinc were placed in a vacuum melting furnace and heated to 1150°C to melt. 1.0kg of rare earth yttrium and pretreated nanocomposite powder were added, and a mixture of nitrogen (99.9% purity) and hydrogen (99.999% purity) (95:5 by volume) was introduced. Degassing was performed at a flow rate of 5 L / min for 25 minutes (extended degassing time), with the hydrogen content controlled at 0.0012wt%. The melt temperature was controlled at 1180°C and held for 30 minutes to ensure dispersion of the nanophase.

[0105] S2 mold pretreatment and coating preparation

[0106] The surface of H13 mold steel was laser clad using a pre-set powder method. WC-Co alloy powder (particle size 50-100μm) was pre-set at a laser power of 4kW, a scanning speed of 5mm / s, and a 40% overlap ratio to form a 100μm-thick hard base layer. A WC-Co-MoS2 transition layer (30μm thick) and a MoS2-graphite powder-h-BN composite surface layer (20μm thick, with a composition adjusted to 15wt% MoS2, 10wt% graphite powder, and 3wt% h-BN) were then applied using supersonic flame spraying. Spraying process parameters included an oxygen flow rate of 1200L / min, a propane flow rate of 300L / min, a powder feed rate of 40g / min, and a spray distance of 120mm. The coating achieved a tensile strength of 85MPa, a porosity of 1.2%, and a friction coefficient of 0.04, reducing coating costs by 30%.

[0107] S3 Vacuum die casting-ultrasonic vibration composite molding

[0108] The composite copper alloy melt is heated to 1250°C and poured into the die-casting machine's injection cylinder. During the injection process, 30kHz ultrasonic vibration (amplitude 20μm) is applied, and the mold cavity is filled at an injection speed of 10m / s. Simultaneously, a pulse pressure of 100MPa (frequency 8Hz) is applied to the mold cavity, and the pressure is maintained for 30 seconds. The mold temperature is controlled at 230°C using a microchannel cooling system, and the cavity vacuum is evacuated to 25Pa. The filling time is 0.25 seconds, and the temperature drop is ≤15°C.

[0109] S4 gradient cooling and composite aging treatment

[0110] After die-casting, the mold is rapidly cooled to 150°C at a rate of 120°C / min, held for 30 minutes, and then cooled to room temperature at a rate of 30°C / min. The copper retainer is placed in a nitrogen-protected aging furnace, held at 180°C for one hour, then raised to 280°C for 0.5 hours. Simultaneously, a constant compressive stress of 60 MPa is applied via a piezoelectric ceramic actuator built into the mold. This reduces the amount of strengthening phase precipitation by 15%, with subsequent shot peening compensating for the performance loss.

[0111] S5 surface nanostructured and ion implanted composite treatment

[0112] The copper holder was placed in an ion implanter and nitrogen ions were implanted at an energy of 50 keV and a dose of 5 × 10 16 ions / cm 2 Ultrasonic shot peening was also performed using 0.1mm diamond shot at a pressure of 1.0 MPa, a frequency of 40 kHz, and a treatment time of 8 minutes. Scanning electron microscopy (SEM) revealed the formation of a gradient nanolayer with a thickness of approximately 35 μm, a surface hardness of 380 HV, and a residual compressive stress of 200 MPa.

[0113] 5. Comparative Example: Traditional Die Casting Process

[0114] Formula and process

[0115] Electrolytic copper, tin, and zinc were added to a conventional smelting furnace in equal proportions and smelted in atmospheric conditions without the addition of rare earth elements or nano-reinforcement phases. The mold was made of uncoated H13 steel and preheated to 150°C. No ultrasonic vibration or pulse pressure was applied during the die-casting process. The injection speed was 5 m / s and the holding pressure was 50 MPa. The castings were machined directly after cooling without aging or surface nano-crystallization treatment.

[0116] 6. Performance Testing and Analysis

[0117] 1. Microstructure Characterization

[0118] TEM observations revealed that the copper matrix of Example 1 was uniformly distributed with Y2O3 nanoparticles (60-80 nm in diameter) and graphene nanosheets, with the nano-silicon carbide forming a good interfacial bond with the matrix. In Example 2, the nanophase distribution was even denser, with spacing ≤150 nm. In Example 3, the expanded graphite was partially exfoliated into graphene layers, which had a weaker bond with the matrix but still provided a reinforcing effect. The comparative example exhibited coarse structure, significant dendritic segregation, and pore defects.

[0119] 2. Mechanical properties test

[0120] The tensile strength of Examples 1-3 was ≥380 MPa, which is 1.46 times greater than that of the comparative example (260 MPa). The hardness of Example 2 reached 320 HV, and the wear resistance was 5 times higher than that of the comparative example. SEM analysis of the tensile fracture surface showed that Examples 1-3 all exhibited ductile fracture characteristics, while the comparative example exhibited brittle fracture.

[0121] 3. Tribological performance test

[0122] Under dry friction conditions, the friction coefficient of Examples 1-3 is ≤0.1, and the wear rate is ≤5×10 -6 mm 3 / (N·m), while the friction coefficient of the comparative example is 0.25 and the wear rate is 2×10 -5 mm 3 / (N·m). The surface nanolayer and high residual compressive stress of Example 2 effectively inhibited abrasive wear and adhesive wear.

[0123] 4. Fatigue performance test

[0124] Under 100 MPa alternating stress, the fatigue life of Examples 1-3 exceeds 10 7 cycles, while the control sample was only 5×10 5 The fatigue crack growth rate (da / dN) of Example 2 is 10 -10m / cycle, compared with the comparative example (10 -8 m / cycle) is reduced by two orders of magnitude.

[0125] This patent achieves a significant improvement in the performance and production efficiency of copper retainers through the coordinated application of multiple innovative technologies. Through the design of different embodiments, it can meet the needs of different application scenarios and has broad market prospects and application value.

[0126] The dissolution rate of herbal ingredients and the ester content of the examples and comparative examples are compared in the following table:

[0127] Table 1

[0128] Group Example 1 Example 2 Example 3 Comparative Example Tensile strength (MPa) 420 450 380 260 Elongation (%) 13 11 10 7 Hardness (HV) 280 320 250 180 <![CDATA[Wear rate (×10 -6 mm 3 / (N·m))]]> 3.2 2.1 4.5 20.0 Fatigue life (cycles) <![CDATA[8×10 7 ]]> <![CDATA[1.2×10 8 ]]> <![CDATA[5×10 7 ]]> <![CDATA[5×10 5 ]]> Surface roughness Ra (μm) 0.5 0.4 0.6 1.5

[0129] Summary: This table compares the performance of different copper retainers in different embodiments and comparative examples. In terms of tensile strength, Examples 1-3 reach 420 MPa, 450 MPa, and 380 MPa, respectively, which is higher than the comparative example's 260 MPa. Elongation is 13%, 11%, and 10%, respectively, which is 7% higher than the comparative example. In terms of hardness, the examples are 280 HV, 320 HV, and 250 HV, which is higher than the comparative example's 180 HV. In terms of wear rate, Examples 1-3 are 3.2×10 -6 mm 3 / (N·m), 2.1×10 -6 mm 3 / (N·m),4.5×10 -6 mm 3 / (N·m), which is much lower than 20.0×10 -6 mm 3 / (N·m); in terms of fatigue life, the fatigue life of Examples 1-3 is 8×10 7 cycles, 1.2×10 8 cycles, 5×10 7 cycles, significantly higher than the 5×10 5 It can be seen that the new process improves the quality and performance of copper retainers.

[0130] The mechanical and environmental adaptability comparisons of the examples and comparative examples are shown in the following table:

[0131] Table 2

[0132] Group Example 1 Example 2 Example 3 Comparative Example Material utilization rate (%) 93 94 91 28 Mold life (times) 18000 22000 15000 6000 Production cycle (hours) 2.0 2.2 1.8 24.0 Energy consumption (kWh / ton) 450 480 420 800 Production cost (yuan / kg) 120 135 95 70

[0133] Summary: This table compares the performance of different copper retainer embodiments with a comparative example. In terms of material utilization, Examples 1-3 achieved 93%, 94%, and 91%, respectively, significantly exceeding the comparative example's 28%. In terms of mold life, the Examples achieved 18,000, 22,000, and 15,000 cycles, respectively, significantly exceeding the comparative example's 6,000 cycles. The production cycle for the Examples was 1.8-2.2 hours, shorter than the comparative example's 24 hours. Energy consumption was 420-480 kWh per ton for the Examples, lower than the comparative example's 800 kWh. Production cost was 95-135 yuan per kilogram for the Examples, lower than the comparative example's 70 yuan. Overall, the Examples offer advantages in material utilization, mold life, production efficiency, and cost, demonstrating that the new process can significantly improve the production efficiency and quality of copper retainers.

[0134] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A copper retainer die-casting process, characterized in that: The following steps are involved: S1: Composite copper alloy preparation Electrolytic copper, tin, and zinc are mixed in a mass ratio of 82-84:9-11:6-7, and 0.8-1.2% of the rare earth element yttrium Y, 0.3-0.7% of nano-silicon carbide, and 0.1-0.3% of graphene nanosheets are added to the alloy, and the mixture is melted at 1150-1180° C. in a vacuum melting furnace, and nitrogen containing 5-10 vol% of hydrogen is introduced for degassing. S2: Mold pretreatment and gradient coating preparation The surface of H13 mold steel is laser clad and pre-deposited with WC-Co alloy powder to form a hard base layer with a thickness of 80-120 μm. Subsequently, a composite coating containing 15-25wt% molybdenum disulfide MoS2, 8-12wt% graphene and 2-4wt% hexagonal boron nitride h-BN is sprayed by high-velocity flame, with a total coating thickness of 15-25 μm. S3: Vacuum die casting-ultrasonic vibration composite molding The composite copper alloy melt is heated to 1220-1280°C, ultrasonic vibration of 20-40kHz is applied in the injection cylinder, and the melt is injected into the mold cavity at an injection speed of 8-12m / s. At the same time, a pulse pressure of 100-150MPa is applied to the mold cavity. S4: Gradient cooling and composite aging treatment After forming, the mold is first cooled to 150°C at a rate of 100-150°C / min, held for 30 minutes, and then cooled to room temperature at a rate of 20-50°C / min. The copper retainer is then aged in a nitrogen atmosphere in two steps: first at 180°C for 1.5 hours and then at 280°C for 2 hours. At the same time, a constant compressive stress of 50-100 MPa is applied to promote the coordinated precipitation of Y2O3 and Cu3Sn strengthening phases. The reaction formula is: S5: Surface nanocrystallization-ion implantation composite treatment Magnetron sputtering ion implantation technology is used to implant nitrogen ions on the surface of the copper retainer, and ultrasonic shot peening is performed at the same time. The shot peening medium is diamond shot. The processing time is 8-12 minutes to form a gradient nano layer with a thickness of 30-60μm.

2. The copper retainer die-casting process according to claim 1, characterized in that: The method also includes a pretreatment step: mixing nano-silicon carbide and graphene nanosheets in a mass ratio of 2:1, ultrasonically dispersing them with deionized water-ethanol, adding 0.5-1.0wt% of a silane coupling agent KH-560 for surface modification to form a uniformly dispersed nano-slurry, and compounding the slurry with a copper alloy melt after drying, with a grafting rate of ≥95%.

3. The copper retainer die-casting process according to claim 1, characterized in that: It also includes real-time monitoring of the melt filling process in S3: the mold surface temperature field is monitored by an infrared thermal imager, and when the filling front temperature is 20-30°C lower than the liquidus temperature, the mold local heating system is automatically triggered.

4. The copper retainer die-casting process according to claim 1, characterized in that: A transition layer is provided between the bottom layer and the surface layer of the gradient coating in S2. The transition layer is composed of WC-Co-MoS2 composite powder and has a thickness of 20-40 μm.

5. The copper retainer die-casting process according to claim 1, characterized in that: The constant compressive stress described in S4 is applied by a piezoelectric ceramic actuator built into the mold cavity, with a stress control accuracy of ±5 MPa, so that the strengthening phase is precipitated along the grain boundaries.

6. The copper retainer die-casting process according to claim 1, characterized in that: The in-plane orientation of the graphene nanosheets in the prepared copper retainer is ≥85%. Scanning electron microscopy shows that the graphene nanosheets are distributed in layers at the grain boundaries, forming a "nano-enhanced network." 7. The copper retainer die-casting process according to claim 1, characterized in that: The ion implantation and ultrasonic shot peening described in S5 work together to make the surface residual compressive stress reach 200-300 MPa.

8. The copper retainer die-casting process according to claim 1, characterized in that: The material utilization rate of the entire process is ≥92%, and the energy consumption per unit product is ≤450kWh / ton.

9. The copper retainer die-casting process according to claim 1, characterized in that: The dimensional tolerance of the manufactured copper retainer is ≤±0.008mm, and the surface roughness Ra is ≤0.6μm.

10. The copper retainer die-casting process according to claim 1, characterized in that: The graphene nanosheets introduced into the composite copper alloy can capture vacancy defects generated during the solidification process of the alloy, reducing the dislocation density to 10 10 / cm 2 the following.

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