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Introduction of working conditions of power station valves

Release Date: July 16, 2018

The working conditions of power station valves are usually high temperature water vapor at 540 ° C. Therefore, the material of the valve body is 25 or 12CrMoV, and the surfacing material of the valve body sealing surface is cobalt-based alloy D802 (STI6) electrode. D802 corresponds to the model EDCoCr-A in the GB984 standard, which is equivalent to ERCoCr-A in AWS. D802 material can be continuously opened and closed under high temperature and pressure, and has excellent abrasion resistance, impact resistance, oxidation resistance, corrosion resistance and cavitation resistance.

The ERCoCr-A welding wire and filler wire deposited in the AWS standard are characterized by a sub-eutectic structure consisting of a chromium carbide carbide eutectic network of approximately 13% distributed in a cobalt-chromium-tungsten solid solution matrix. The result is a perfect combination of resistance to low stress abrasion and the toughness necessary to withstand certain programmatic impacts. Cobalt alloys have good resistance to metal-to-metal wear, especially scratch resistance under high load conditions. The high alloy element content in the matrix provides excellent corrosion resistance and oxidation resistance. Cobalt-based alloys do not undergo allotropic transformation. When the deposited metal of cobalt-based alloys is in a hot state (below 650 ° C), the hardness decrease is not obvious. Only when the temperature rises above 650 ° C, the hardness decreases significantly. When the temperature returns below the hot state, its hardness returns to close to the original hardness. That is, when the base material is subjected to post-weld heat treatment, the performance of the sealing surface will not be lost.