ensure clear casting outline and intact marking on the cross blank.
2.Investment Casting & Forming
Melt qualified A36 carbon steel under precise temperature control. Pour molten steel into the pre-treated mould cavity to form integrated four-way cross blanks with four socket holes and pre-cast threaded boss positions.Control pouring speed and cooling rate to avoid shrinkage, porosity and deformation, ensuring uniform wall thickness and complete contour of the cross body.
3.Deburring, Shot Blasting & Machining
Remove casting sprues, flash and burrs by grinding and shot blasting to eliminate residual sand and oxide scale on inner and outer surfaces. Perform precision machining on each threaded boss, tap internal threads for hex socket set screws. Ensure the inner diameter of each socket meets the tolerance requirement for matching round pipes.
4.Surface Pretreatment
Carry out multi-step pretreatment including degreasing, pickling and surface activation. Thoroughly remove oil stains, rust and oxide layers on the casting surface. Clean and dry the workpiece to obtain an active and clean substrate, improving the adhesion of the subsequent composite zinc coating.
5.Composite Electro-galvanizing & Hot-dip Galvanizing
Adopt combined electro-galvanizing and hot-dip galvanizing process to form composite anti-corrosion zinc layer with total thickness up to 80μm. Electro-galvanizing provides a uniform base zinc layer, then hot-dip galvanizing builds up thick protective coating. This treatment greatly enhances rust resistance and corrosion resistance, suitable for outdoor and humid working conditions.
6.Final Inspection & Packaging
Implement full quality inspection including coating thickness test, dimensional check, thread fit test and appearance inspection. Mark qualified products with material grade and batch information. Pack finished galvanized cross fittings with protective packaging to prevent scratches and collision damage during storage and transportation.