6063 Aluminum: Practical Production Differences Between T5 and T6 Tempers

When extruding 6063 aluminum, choosing between the T5 and T6 tempers changes how you run your production line. This choice changes press speed, cooling setups, and oven times. It is a direct trade-off between excellent profile shapes and maximum mechanical strength.

1. Die Exit Temperature Management

The temperature of the metal profile as it leaves the die controls how well the alloying elements (Magnesium and Silicon) mix inside the aluminum matrix.

• T5 Temper: The target exit temperature is 500°C to 520°C. This is an easier window to hit. It reduces the risk of overburning the metal, allows for faster press speeds, and saves die life.
• T6 Temper: The target exit temperature must be high and tight at 520°C to 545°C. You must monitor this closely. If the temperature drops below 520°C, the chemical phase cannot fully dissolve, and the metal will fail the final hardness check.

2. The Quenching Setup on the Press Line

Quenching locks the internal structure immediately after the profile leaves the die.

• T5 Temper (Forced Air): You only need cooling fans on the run-out table. The cooling rate must be at least 4°C per minute. Because air cools the metal slowly and evenly, the profile stays perfectly straight. This is the practical choice for complex, thin-walled, or architectural shapes that warp easily.
• T6 Temper (Water Quench): You must use water spray headers, mist nozzles, or a water bath right behind the die. The cooling rate must hit at least 20°C to 30°C per second. This rapid chilling causes uneven shrinkage. It creates a high risk of warping, twisting, or bending the profile, which requires intense post-quench stretching to correct.

3. Aging Oven Regimes

After cooling and cutting, the profiles go into the artificial aging oven to reach their final hardness.

• T5 Oven Cycle: Bake at 175°C to 185°C for 2 to 5 hours. Because air cooling leaves fewer reactive points in the metal structure, the profile stabilizes quickly. Final hardness is a modest 8 to 12 HW on the Webster scale.
• T6 Oven Cycle: Bake at 180°C to 195°C for 5 to 8 hours. The heavy water quench creates an active metal structure that responds strongly to the longer bake. This brings the profile to peak mechanical strength, hitting a yield strength of 170 to 200 MPa and a hardness of 13.5+ HW.

Practical Comparison Table

Shop Floor Parameter	T5 Temper	T6 Temper
Target Exit Temp	500°C to 520°C	520°C to 545°C
Quench Tooling	Air Fans Only	Water Spray / Mist / Bath
Risk of Shape Warping	Very Low	High (Requires Stretching)
Oven Hold Time	2 to 5 hours (Faster Turnaround)	5 to 8 hours (Higher Energy Cost)
Final Hardness	8 to 12 HW (Easy to Cut/Bend)	13.5+ HW (Stiff / High Load)

Conclusion

From a practical view, use T5 to speed up production, lower tool wear, and keep exact shapes on tricky profiles. Switch to T6 only when the customer’s blueprint demands heavy load-bearing strength and you are ready to handle water-cooling warping.