Tempering temperature

You do tempering after hardening to give the workpiece toughness again. The hard, brittle martensitic structure is transformed into a tougher structure. You choose the temperature depending on the desired hardness and material – the higher you go, the softer and tougher the part becomes. Make sure the temperature is uniform and not too high, otherwise you lose the hardness completely. If you temper after welding, it's usually about relieving stresses and relaxing the heat-affected zone.