Heat Treatment Process of Heat Resistant Steel Casting

Heat Treatment Process of Heat Resistant Steel Casting
Heat resistant steel casting is widely used in metallurgy, building materials, electric power and other industries, such as the guide plate of rolling mill, the kiln mouth guard plate of rotary kiln, the first and second chamber castor plates of castor cooler, and the coal nozzle of thermal power plant.
These accessories are operated at high temperatures ranging from 1000 ℃ to 1300 ℃. They must not only withstand high temperature oxidation and corrosion, but also bear the movement wear of red hot materials under high temperatures. The working conditions are very harsh.
If there is a slight deviation between material selection and product quality, it will lead to early failure in use and cause losses to users.

clean:
1. Oil stain, residual salt, paint and other foreign matters shall be removed from the workpiece and fixture before heat treatment
2. The fixture used in the vacuum furnace shall be degassed and purified at a vacuum degree not lower than that required by the workpiece in advance
Charging:
1. Workpieces easy to deform during heat treatment shall be heated on special fixture
2. The workpiece shall be placed in the effective heating area.
preheat:
1. For workpieces with complex shape, sharp change of section and large effective thickness, preheating shall be carried out
2. The preheating methods are as follows: the primary preheating is 800 º C, the secondary preheating is 500~550 º C and 850 º C, and the temperature rise speed of the primary preheating should be limited
Heating:
1. Workpieces, castings and weldments with grooves and no through holes, as well as stainless steel workpieces formed by machining, are generally not suitable for heating in salt bath furnaces
2. The workpiece shall be heated for enough heat preservation time,
1. Martensitic stainless steel heat-resistant steel should be scattered in a dry place when air cooling
2. Martensitic stainless steel and heat-resistant steel can be cleaned, cryogenic treated or tempered after quenching and cooling to room temperature
3. The workpiece shall be tempered in time after quenching, and the time interval shall not exceed 4h generally. The carbon content (carbon mass fraction) of the steel used for the workpiece is low, and the shape of the workpiece is simple, which shall not exceed 16h
4. For welded assemblies composed of martensitic stainless steel and heat-resistant steel, the time interval between welding and subsequent heat treatment shall not exceed 4h
Cleaning: 1. According to the requirements of the workpiece and the surface condition, use alkali cleaning, water-soluble cleaning agent, chlorine solvent sand blasting, shot blasting and other methods for cleaning. After correction, stress relief annealing shall be carried out at a temperature lower than the original tempering temperature. For workpieces with complex shape or strict size requirements, shape setting fixture shall be combined with tempering for correction during tempering after correction. Austenitic stainless steel workpieces shall be stress relieved below 300 º C after correction.