The incoming raw materials are brass ingots with complete mill test certificates (MTC). The QC team cross-checks the heat number, alloy grade, chemical composition and mechanical properties against relevant ASTM standards. Visual inspection is carried out to check for surface cracks, cold shuts, slag inclusions, porosity and surface segregation. Random sampling is taken for spectrometer analysis to verify the content of copper, zinc, lead and other trace alloy elements, which directly affect machinability, corrosion resistance and surface quality. The dimensions and weight of ingots are measured and recorded for production scheduling. Qualified ingots are marked and stored in the designated area; non-conforming materials are isolated and returned to the supplier with a formal rejection report.
2.Melting & Continuous Casting:
Qualified brass ingots are put into the melting furnace under a protective atmosphere to reduce oxidation and zinc burning loss. The temperature is accurately controlled and the molten brass is fully stirred to homogenize the composition. Slag removal and purification treatment are performed to eliminate inclusions and gas inside the liquid metal. After composition sampling and confirmation, the molten brass is poured into the continuous casting crystallizer. The solidified round billet is pulled out at a stable speed with water cooling to control the solidification rate. The cast billet is cut to the specified length, and surface defects such as oxide skin and segregation layer are inspected.
3.Extrusion & Intermediate Annealing:
The qualified cast billet is heated to the proper extrusion temperature and sent to the horizontal extrusion press. Under stable extrusion pressure, the billet is extruded through the round die to form the primary solid round bar blank. The extrusion speed and temperature are strictly controlled to avoid surface tearing, coarse grain and uneven structure. After extrusion, the bar is air-cooled. For brass grades prone to work hardening, intermediate annealing is arranged: heat the bar in a circulating air furnace, hold at the set temperature and cool slowly to eliminate extrusion stress, restore ductility and prepare for subsequent drawing.
4.Cold Drawing & Straightening:
The extruded blank is transferred to the cold drawing line. Multi-pass cold drawing is adopted with reasonable single-pass reduction, gradually reducing the diameter to the finished size and meeting strict diameter tolerance requirements. After each drawing pass, the surface and dimension are checked. The cold-worked bar has high hardness and internal stress. It is sent to the straightening machine for multi-roll straightening to eliminate bending and camber. Straightness inspection is carried out to ensure the bar meets straightness specifications.
5.Finishing Machining & Comprehensive Inspection:
The straightened brass bars go to the finishing workshop. The two ends are cut to the required finished length by sawing machine. The end faces are chamfered and deburred to remove sharp burrs and cutting scraps. Polishing is optional if bright surface is required. Full inspection items include diameter tolerance, length, straightness, surface finish. Visual inspection checks for scratches, pits, cracks and discoloration. Hardness test can be performed on request to confirm mechanical properties. Qualified bars are marked with heat number, alloy grade, size and QC stamp.
6.Cleaning, Anti-tarnish Treatment & Export Packaging:
Qualified bars are cleaned with degreasing agent and pure water rinsing to remove drawing oil, dust and residual stains, then fully dried. Anti-tarnish passivation treatment is applied to form a thin protective film and prevent brass oxidation and discoloration during storage and transportation. The bars are bundled neatly, separated by moisture-proof paper. Bundles are fixed on export wooden pallets, reinforced with packing belts, and desiccants are placed inside the package to avoid dampness. Packing list, material test certificate and shipping mark are attached outside the package for overseas shipment.