First, preheating:
1. For the workpiece with complex shape or sharp cross-section change and large effective thickness, it should be preheated
2. The method of preheating is: a preheating for 800℃, secondary preheating is 500~550℃ and 850℃, the temperature rise rate of primary preheating should be limited
Two, heating:
1. There are notches and holes in the workpiece, casting and welding parts and processed stainless steel workpiece, generally not in the salt bath furnace heating
2. Ensure that the workpiece is heated for a sufficient time. Calculate the effective thickness of the workpiece and the conditional thickness (the actual thickness multiplied by the workpiece shape coefficient) by referring to Table 5-16 and Table 5-17
Three, cleaning:
1. The workpiece and fixture should be cleared of oil, residual salt, paint and other foreign objects before heat treatment
2. The fixture used for the first time in the vacuum furnace should be degassed and purified in advance at least under the vacuum degree required by the workpiece
Four, furnace loading:
1. In the process of heat treatment, the deformable workpiece should be heated on a special fixture
2. The workpiece should be placed in an effective heating zone