Inspect incoming 6061 aluminum alloy cast billets. Use a spectrometer to confirm chemical composition complies with ASTM B211 standard. Check internal quality by ultrasonic testing to detect shrinkage cavities, porosity, slag inclusions and internal cracks. Visually examine billet surface for peeling, deep scratches, severe oxidation and segregation. All test data shall be recorded in the inspection report. Non-conforming billets shall be clearly marked, isolated and returned to the supplier.
2.Hot Extrusion Forming:
Load qualified billets into a circulating hot-air furnace for uniform heating, strictly control heating temperature, holding time and temperature uniformity to avoid local overheating. Transfer the heated billet to the extrusion press rapidly. Extrude through precision circular carbide die under stable hydraulic pressure. Adjust extrusion force, extrusion speed and exit temperature continuously to prevent surface tearing, orange peel, coarse grain ring and uneven metallographic structure, obtaining the preliminary extruded solid round aluminum bar blank.
3.Multi-pass Cold Drawing Sizing:
Treat extruded blanks with surface lubrication before drawing. Carry out progressive multi-pass cold drawing with matched tungsten carbide drawing dies. Gradually reduce the cross-section area in each pass within reasonable deformation rate. Monitor drawing speed and lubrication status in real time to stabilize outer diameter tolerance, roundness and straightness, reduce surface roughness and achieve the precise size required by drawings.
4.Solution Heat Treatment & Artificial Aging (T6):
Transfer sized aluminum blanks to heat treatment line for T6 temper. Solution treatment: heat the bar to specified solution temperature and keep constant for sufficient holding time to dissolve alloying elements into aluminum matrix, followed by rapid water quenching to retain supersaturated solid solution. Then perform artificial aging at constant temperature for scheduled holding time. Fine Mg₂Si strengthening phases precipitate uniformly during aging, so the material reaches designed tensile strength, yield strength and hardness.
5.Finishing & Anodizing Surface Treatment:
Straighten the aluminum bar on multi-roll straightening machine to eliminate bending and twisting deformation generated in extrusion and drawing. Cut to customer-specified fixed lengths by precision sawing, then deburr both ends. Conduct pre-treatment procedures sequentially: degreasing to remove oil and lubricant, alkaline etching to eliminate natural oxide layer and minor surface flaws, neutralization to neutralize residual alkali, multi-stage pure water rinsing to avoid contamination. After thorough drying, implement anodic oxidation process in sulfuric acid electrolyte under stabilized voltage and temperature, forming a dense, uniform and hard alumina anodic film on the surface. Rinse again and perform sealing treatment to improve corrosion resistance and dyeing stability if color is required.
6.Final Inspection & Packaging:
Conduct full finished inspection, including dimensional tolerance checking, straightness and roundness measurement, visual surface defect inspection, anodic oxide film thickness test, hardness test, tensile property test and metallographic spot check. Label qualified products with alloy grade, diameter, length, temper, anodizing mark, batch number and inspection mark. Wrap each bar with anti-scratch protective film, arrange neatly inside fumigated wooden cases, place moisture-proof desiccants and fasten the package to avoid collision damage during sea or land transportation.