1、 Preheating:
1. For workpieces with complex shapes or sharp changes in cross-section, as well as larger effective thickness, preheating should be carried out
2. The methods for preheating include: preheating at 800? C. Is the secondary preheating between 500 and 550? C and 850? C. The speed of temperature rise during one preheating should be limited
2、 Heating:
1. Workpieces with grooves but no holes, castings and welded parts, as well as processed stainless steel workpieces, are generally not suitable for heating in a salt bath furnace
2. The heating of the workpiece should have sufficient insulation time, which can be calculated based on the effective thickness and conditional thickness of the workpiece (actual thickness multiplied by the workpiece shape coefficient) by referring to Tables 5-16 and 5-17
3、 Cleaning:
1. Before heat treatment, the workpiece and fixture should be cleaned of foreign objects such as oil stains, residual salt, paint, etc
2. The fixture used for the first time in a vacuum furnace should undergo degassing and purification treatment in advance at a vacuum degree not lower than the required for the workpiece
、 Charging:
1. Workpieces that are prone to deformation during heat treatment should be heated on a dedicated fixture
2. The workpiece should be placed in an effective heating zone