Copper-Nickel-Silicon Precipitation Hardening
A thermal hardening process in copper alloys involving the precipitation of silicides to maximize electrical conductivity while maintaining high elevated-temperature strength. Precipitation kinetics are controlled by solution annealing and subsequent aging.
The hardening of CuNiSi alloys occurs through solution annealing and subsequent precipitation of silicides. This improves conductivity and hot strength, but if you put too much heat into welding, you can ruin the condition again. Then the material becomes soft or cracks form, especially if cooling is too fast or uncontrolled. You must have the parts clean and dry before welding and keep heat input as low as possible. After welding, you can restore hardening through controlled heat treatment, but exact times and temperatures depend on the alloy and wall thickness – if in doubt, ask the manufacturer.