We inspect incoming A36 carbon steel coil strips. Use a spectrometer to verify chemical composition and perform mechanical property tests to confirm compliance with ASTM A36 standard. Carefully check the strip surface for cracks, rust, pits, scratches and laminations. Check the thickness and width tolerance. Unqualified steel strips will be marked, isolated and returned to the supplier.
2.Blanking & Stamping Forming:
Feed the qualified steel strip into the stamping press with precision die sets. Complete high-speed blanking to punch the inner hole and outer circle of flat washers in one stroke. Control stamping pressure and feeding accuracy strictly to guarantee concentricity, outer diameter and inner diameter dimensions. Remove rough edge burrs after stamping, sort out deformed, cracked or misshapen semi-finished washers.
3.Deburring & Pre-cleaning:
Put stamped washers into the tumbling machine with abrasive media for tumbling deburring. Remove sharp burrs and stamping flash around the inner hole and outer edge. Then carry out degreasing pre-cleaning to wipe off stamping oil, dust and metal powder on the surface, ensuring a clean base for subsequent plating.
4.Acid Activation & Color Zinc Plating:
Send cleaned washers to the electroplating line. First perform pickling and activation to remove thin oxide layer. Then proceed with color zinc plating process. Strictly control current density, plating time, bath temperature and PH value to form uniform, bright chromate color zinc coating. Control coating thickness to meet customer anti-corrosion requirements.
5.Post-plating Treatment & Full Inspection:
Complete passivation and sealing treatment after plating to improve corrosion resistance of the zinc layer. Conduct full visual inspection: check for plating leakage, blistering, peeling, discoloration and scratches. Randomly test coating thickness, salt spray resistance and dimensional tolerance. Mark batch number for qualified washers.
6.Sorting, Packaging & Shipment:
Sort qualified washers by size. Pack them into plastic bags or cartons according to packing quantity requirement, add desiccant inside for moisture-proof. Put packed goods into export wooden cases. Attach inspection certificate and shipping mark before shipment.