Step 1: Billet Preparation and Induction Heating
High-purity cylindrical aluminum alloy billets are sheared to specific log lengths and fed into a gas or electric induction preheat furnace. The billet is heated to the optimal hot-working temperature range—typically between 450°C and 500°C for 6000-series alloys—rendering the metal ductile without melting.
Step 2: Tooling Preheating and Extrusion Pressing
The hardened steel extrusion die (manufactured from H13 tool steel) is preheated to 450°C to prevent thermal shock. A powerful hydraulic ram applies thousands of tons of pressure (ranging from 600 tons to 3,600+ tons depending on press capacity), forcing the plasticized aluminum through the precision-machined aperture of the die.
Step 3: Online Quenching and Temperature Monitoring
As the continuous profile emerges from the die onto the runout table, it must be rapidly cooled below 200°C to lock the alloying elements (magnesium and silicon) into solid solution. Depending on the alloy and wall thickness, quenching is executed via high-velocity forced air fans or continuous water mist chambers.
Step 4: Puller Guidance, Cooling Table & Stretch Straightening
An automated mechanical puller guides the hot extrusion along the runout table to maintain straightness. After cooling to room temperature on walking beams, the entire length undergoes hydraulic stretch straightening to relieve internal residual stresses, correct minor twisting, and achieve specified angular tolerances.
Step 5: Precision Sawing and Artificial Aging Heat Treatment
Extrusions are sawn to intermediate lengths and transferred into computer-controlled artificial aging furnaces. Profiles are held at controlled soaking temperatures (typically 175°C – 190°C for 4 to 8 hours) to precipitate Mg₂Si phases, elevating the metal from soft T4 temper to full structural T5 or T6 hardness.
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