Pressure Welding The Efficiency Leader in Mass Production
Pressure Welding The Efficiency Leader in Mass Production
Pressure welding takes "pressure" as the core joining method, requiring no (or little) filler material. It has fast welding speed and low cost, making it especially suitable for mass joining of thin plates and wires. It is widely used in fields such as automotive manufacturing, home appliance production, and electronic component packaging.
(I) Resistance Welding: The "Core Technology" in Automotive Manufacturing
Resistance welding uses the principle of "contact resistance heating." It clamps the workpieces and passes a large current through them, generating high local temperatures to melt (or plastically deform) the metals. After cooling, weld spots are formed. It is divided into three types: spot welding, seam welding, and projection welding, among which spot welding is the "main force" in automotive body welding.
1. Spot Welding: The "Dot Matrix" Technology for Efficient Joining
Principle: Two electrodes clamp the thin plates and pass a large current of 1000-10,000A through them. The contact resistance between the electrodes and the thin plates generates heat, causing local metal melting to form a "fusion core." After powering off, pressure is maintained until cooling to form a circular weld spot. Arranging multiple weld spots enables large-area joining.
Operational Points:
• Electrode Selection: Use copper-chromium alloy electrodes for welding low-carbon steel and copper-zirconium alloy electrodes for welding galvanized steel sheets. Keep the electrode tip flat and regrind it in time after wear (the tip diameter is generally 2-3 times the plate thickness).
• Parameter Control: Strictly match the welding time (0.1-0.5 seconds), current (adjust according to the plate thickness; e.g., 3000-4000A for 2mm thick steel plates), and pressure (ensure tight contact between the electrodes and the workpieces to avoid excessive contact resistance) to prevent cold soldering or burn-through.
• Quality Inspection: Weld spots should be free of cracks and spatter. During tensile testing with a tensile testing machine, "base metal tearing" rather than "weld spot detachment" should occur to ensure welding strength.
2. Seam Welding: The "Continuous Defense Line" for Sealed Structures
Seam welding is similar in principle to spot welding, but the electrodes are replaced with copper rollers. The rollers rotate and pass a pulsed current to form a continuous weld. It is suitable for welding sealed structures such as automotive fuel tanks, water heater liners, and pipeline joints. During operation, control the roller pressure and rotation speed to ensure a continuous, leak-free weld. When welding galvanized steel sheets, regularly clean the zinc layer on the roller surface to avoid abnormal contact resistance.
(II) Friction Welding: The "High-Strength Option" for Shaft-Like Parts
Friction welding achieves joining through "high-speed rotational friction heating." It clamps two cylindrical parts (such as shafts and rods), with one rotating at a high speed (1000-5000r/min). The heat generated by friction brings the contact surface to a plastic state. After stopping rotation, greater pressure is applied to form a strong weld.
• Core Advantages: High welding strength (weld strength higher than that of the base metal), no porosity or slag inclusion, and fast welding speed (single welding time <10 seconds). It is suitable for welding shaft-like parts such as automotive half-shafts, engine crankshafts, and tool shanks.
• Operational Points: Control the rotational speed and friction pressure to ensure uniform temperature on the contact surface (avoid local overheating); when welding dissimilar materials (such as steel and copper), adjust the rotational speed and pressure to prevent cracks caused by differences in thermal expansion coefficients.
