Ten key points of galvanized pipe heat treatment:

1, galvanized pipes and fixtures should be removed before heat treatment of oil, residual salt, paint and other foreign materials;

2, the fixture used for the first time in the vacuum furnace should be degassed and purified in advance at a vacuum degree not lower than that required by the workpiece;

3, the workpiece that is easy to deform in the heat treatment process should be heated on the special fixture. The preheating methods are: the primary preheating is 800℃, the secondary preheating is 500-550℃ and 850℃, and the primary preheating temperature rise speed should be limited;

4, for complex shapes or sharp changes in section and large effective thickness of the workpiece, should be preheated;

5, Workpieces, castings and welds with grooves through holes and processed stainless steel workpieces are generally not suitable for heating in salt bath furnaces;

6, according to the effective thickness of the workpiece and the condition thickness (actual thickness multiplied by the workpiece shape factor), galvanized pipe heating should have enough holding time;

7. Martensitic stainless steel and heat-resistant galvanized steel pipes can be cleaned, cryogenic treatment or tempering after quenching to room temperature, and the time interval between welding and subsequent heat treatment should not be more than 4 hours;

8. According to the requirements and surface conditions of galvanized pipes, alkaline washing, water-soluble cleaning agent, chlorine solvent sandblasting, shot blasting and other methods are used to clean them;

9. After correction, stress relief annealing should be carried out at a lower temperature than the original tempering temperature. The workpiece with complex shape or strict size requirements should be corrected with a set fixture combined with tempering after correction.

When the mechanical properties of the galvanized pipe are not qualified, repeated heat treatment can be carried out, but the number of repeated quenching or solid solution is generally not more than two times. Supplemental tempering of galvanized pipes does not count as repeated treatment. Martensitic stainless steel and heat-resistant steel workpieces in the quenched state or after low temperature tempering should be preheated, annealed or tempered at high temperature before repeated quenching.