I. Processing Technology
This product is an aluminum alloy valve body for a high-speed rail hydraulic valve. It is a cubic cavity hydraulic core component that must meet the pressure resistance, sealing, and fatigue resistance requirements of the high-speed rail hydraulic system. The core process utilizes a forged blank + five-axis CNC machining + surface strengthening treatment. The specific process is as follows:
1. Raw Material Selection: 6061-T6 aluminum alloy is selected (high comprehensive strength, good weldability, suitable for the pressure resistance requirements of the hydraulic system); for heavy-duty applications, 7075-T6 aerospace aluminum alloy (ultra-high strength, excellent fatigue resistance) can be selected. Forged aluminum blanks are used (to eliminate internal porosity and improve structural density).
2. Blank Pretreatment: The forged aluminum blank undergoes solution treatment and aging (530℃ solution treatment + 175℃ artificial aging) to eliminate forging internal stress; after being cut to length by a CNC sawing machine, rough datum machining is performed by plane milling to ensure subsequent clamping accuracy.
3. Five-Axis CNC Precision Machining:
◦ Utilizing a five-axis CNC machining center, cavity boring, oil passage drilling/tapping, sealing groove milling, and flange face finish milling are completed in a single setup, ensuring coaxiality and perpendicularity during multi-station machining;
◦ Deep hole drilling and honing are applied to the hydraulic oil passages to achieve a hole wall roughness of Ra0.2~0.4μm, reducing hydraulic oil flow resistance;
◦ The sealing groove employs precision boring and polishing processes to ensure groove wall smoothness and dimensional accuracy, meeting the compression sealing requirements of the sealing ring;
◦ Mass production utilizes hydraulic tooling fixtures to prevent deformation during the machining of thin-walled cavities.
4. Surface Treatment:
◦ Hard Anodizing: Key sealing and mating surfaces undergo 20-30μm thick hard anodizing, achieving a hardness ≥HV450, improving wear resistance and resistance to hydraulic oil corrosion.
◦ Passivation Treatment: Non-mating surfaces undergo chromating/chromium-free passivation to form a 5-8μm protective layer, preventing oxidation and corrosion in the outdoor environment of high-speed rail.
◦ Thread Protection: Plastic protective plugs are installed in the oil passage thread holes to prevent the entry of chips and impurities during subsequent processes.
5. Inspection and Pressure Testing: Full-dimensional inspection using a coordinate measuring machine is performed, and a hydraulic pressure test is conducted to ensure the oil passage sealing performance (pressure 1.5 times the working pressure, held for 30 minutes without leakage). Simultaneously, the valve body's pressure resistance and fatigue resistance are tested.
II. Machining Accuracy
This valve body is a core component of the high-speed rail hydraulic system. Its accuracy must match the high reliability requirements of high-speed rail operation. Key indicators are as follows:
1. Dimensional Accuracy:
◦ Oil passage inner diameter tolerance: H7 grade (+0.018/0mm), ensuring a clearance fit with the valve core (clearance ≤0.02mm);
◦ Sealing groove dimensions (width/depth) tolerance: ±0.01mm, ensuring uniform compression of the sealing ring for hydraulic sealing;
◦ Flange mounting hole position accuracy: ≤0.03mm, hole diameter tolerance H7 grade, suitable for assembly positioning in the high-speed rail hydraulic system;
◦ Cavity internal dimension tolerance: ±0.02mm, meeting the movement clearance requirements of the hydraulic valve core.
2. Geometric Tolerances:
◦ Sealing surface flatness: ≤0.01mm/100mm, reducing the sealing gap of the sealing ring;
◦ Coaxiality of the oil passage axis: ≤0.02mm, ensuring smooth flow of hydraulic oil;
◦ Perpendicularity of the flange face and the cavity axis: ≤0.02mm, preventing displacement of the oil passage under stress after assembly;
◦ Cylindricity of the cavity inner wall: ≤0.02mm, preventing valve core movement jamming.
3. Surface Finishes:
◦ Oil passage inner wall roughness Ra0.2~0.4μm, reducing hydraulic oil flow resistance and valve core wear;
◦ Sealing surface roughness Ra0.4~0.8μm, improving the fit and sealing performance with the sealing ring;
◦ Non-mating surface roughness Ra3.2μm, meeting basic protection and assembly requirements.
III. Industry Applications
These aluminum alloy high-speed rail hydraulic valve bodies, with their lightweight, high strength, and resistance to hydraulic corrosion, are primarily used in the high-speed rail transit sector. They can also be extended to other rail transit and hydraulic equipment applications, specifically as follows:
1. High-speed Rail Transit Sector:
◦ High-speed rail braking system: As the core valve body of the brake hydraulic valve, it controls the pressure and flow of the brake oil circuit. Its lightweight design reduces the unsprung mass of the high-speed rail, improving operational stability.
◦ High-speed rail bogie system: Used as the valve body for the bogie suspension hydraulic adjustment valve, adapting to the hydraulic control requirements of suspension damping during high-speed rail operation.
◦ High-speed rail door system: As the valve body of the door hydraulic drive valve, it precisely controls the hydraulic power for door opening and closing, ensuring smoothness and sealing of the door.
2. Urban Rail Transit:
◦ Subway Vehicles: Hydraulic valve bodies for subway braking and traction systems; the corrosion resistance of the aluminum alloy material is suitable for the humid environment of subway tunnels.
◦ Trams: Hydraulic valve bodies for tram hydraulic steering systems; lightweight design reduces vehicle energy consumption and improves range.
3. Industrial Hydraulic Equipment:
◦ Heavy Machinery: Control valve bodies for construction machinery hydraulic systems, suitable for the high-pressure hydraulic conditions of excavators and cranes.
◦ Hydraulic Power Stations: Core valve bodies for industrial hydraulic power stations; the heat dissipation of the aluminum alloy material reduces hydraulic oil temperature rise and improves system efficiency.
4. Aerospace:
◦ Aircraft Hydraulic Systems: Miniaturized hydraulic valve bodies (lightweight modified version), suitable for the weight reduction requirements of aircraft hydraulic systems.
◦ Aerospace Ground Equipment: Hydraulic valve bodies for rocket launch pad hydraulic adjustment systems; high-strength aluminum alloy can withstand the harsh operating conditions of aerospace equipment.
