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 guide plate of rolling mill, kiln mouth guard plate of rotary kiln, one or two chamber castor plate of castor cooler, coal nozzle of thermal power plant and so on.

These accessories work at high temperature, and the working temperature is between 1000 ℃ and 1300 ℃. They not only bear high temperature oxidation and corrosion, but also bear the movement wear of red hot material transportation at high temperature, and the working conditions are very bad.

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.

Therefore, the design and high quality of heat-resistant steel casting products is an important topic for the majority of scientific and technological workers and enterprises.

clean:

1. Before heat treatment, the workpiece and fixture shall be cleaned of oil, residual salt, paint and other foreign objects

2. For the fixture used for the first time in the vacuum furnace, degassing and purification treatment shall be carried out in advance under the vacuum degree not lower than the required by the workpiece

Charging:

1. The workpiece that is easy to deform during heat treatment shall be heated on the special fixture

2. The workpiece should be placed in the effective heating zone

preheat:

1. Preheat the workpiece with complex shape or sharp change of section and large effective thickness

2. Preheating method: one time preheating is 800 º C. The second preheating is 500 ~ 550 º C and 850 º C. The speed of temperature rise of primary preheating should be limited

Heating:

1. Generally, it is not suitable to heat the workpieces with grooves and no holes, castings and weldments, as well as the stainless steel workpieces processed and formed in the salt bath furnace

2. There should be enough heat preservation time for workpiece heating, which can be calculated according to the effective thickness and condition thickness of workpiece (actual thickness multiplied by workpiece shape coefficient) with reference to table 5-16 and table 5-17

Cooling:

1. Martensitic stainless steel heat-resistant steel should be placed in a dry place when it is air-cooled

2. Martensitic stainless steel and heat-resistant steel can be cleaned, cryogenic treated or tempered after quenching to room temperature

3. The workpiece should be tempered in time after quenching, the time interval should not exceed 4h, the carbon content (carbon content) of the steel used for the workpiece is low, and the shape of the workpiece is simple, which should 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

clear:

1. According to the workpiece requirements and surface conditions, alkali cleaning, water-soluble cleaning agent, chlorine solvent sand blasting, shot blasting and other methods are used for cleaning

2. Generally, pickling is not used for cleaning

correcting:

1. The workpiece should be corrected by static load, and it is generally not suitable for local knocking

2. After correction, stress relief annealing should be carried out at a temperature lower than the original tempering temperature

3. The workpiece with complex shape or strict size requirements shall be corrected by setting fixture combined with tempering after correction

4. Austenitic stainless steel workpieces, after correction in 300 º Stress relief treatment shall be carried out below C