Description of heat treatment of sealing surface of carbon steel gate valve

The heat treatment of the sealing surface of the carbon steel gate valve refers to the heat treatment of the carbon steel valve body and the gate plate for the cobalt-chromium-tungsten carbide sealing surface. After the carbon steel gate valve is surfacing the cobalt-chromium-tungsten carbide sealing surface, the stress relief annealing is carried out, and the main purpose is to remove the residual stress generated by the surfacing and improve the machinability.

For the gate valve of carbon steel, the CoCrW cemented carbide, SF-4 (137) alloy, spray welded WF330 or Fe30 parts, the stress relief annealing heating temperature is selected according to the base material carbon steel, generally 600~650 °C. The holding time depends on the effective thickness of the part, generally 1h/25mm, minimum 2h. After the heat preservation, the furnace was cooled to 300 ° C and then air-cooled.

Due to the different media used for carbon steel gate valves, different surfacing surface materials can be used. Gate valves for water, steam, petroleum and their products are generally surfacing Cr13 stainless steel, but some factories are welded with chromium-manganese alloy (85 alloy or 137 alloy), copper alloy and iron-based alloy.

Surfacing materials can be divided into two categories according to the effect of heat treatment. One type is represented by cobalt-chromium-tungsten carbide, and its hardness can not be changed by heat treatment. The hardness of the sealing surface is guaranteed by the surfacing material. The other type is represented by Cr13 stainless steel, the hardness of which can be changed by heat treatment, and the hardness of the sealing surface (generally required to be 38~44HRC) can be achieved by heat treatment.