Maintenance of weld neck flange

　　The methods of preheating are: 800?C for one time, 500-550 and 850 for two times. The speed of temperature rise for one time should be limited.

　　1. Heating:

　　Workpieces, castings and welds with grooves and no through holes, and ASTM A105 Dn150 Class 150 RF Weld Neck Flange processed and formed, are generally not suitable for heating in salt bath furnaces.

　　Workpiece heating should have sufficient holding time, depending on the effective thickness and conditional thickness of the workpiece.

　　2. Cleaning:

　　Workpieces and fixtures should be cleaned of foreign substances weld neck flange, residual salt and paint before heat treatment.

　　The fixture used for the first time in vacuum furnace should be degassed and purified in advance at the required vacuum degree of the workpiece.

　　3. Furnace loading:

　　Weld neck flange that are easily deformed during heat treatment should be heated on special fixtures.

　　Workpiece should be placed in the effective heating zone