The difference of 379HB between the surface hardness of 2Cr13 surfacing Stellite NO.6 and that of 379HB is more than 50HB. The 17-4PH steel is heat-treated with 1040 ℃ for 1h, air cooling, 610 ℃ for 4h, and air cooling. Its hardness is 329HB. During the heat treatment of forging blanks, attention should be paid to the starting point of martensite transformation and the temperature of aging treatment. Transformation point The martensite starting transformation point Ms of 17-4PH steel is about 121 ℃, and the transformation ending point Mf is about 32 ℃. The valve seat is a large section part, which should be preheated at 650 ℃, then heated to 1040 ℃ in a high temperature furnace for 1h, air cooled, and needs to be quickly cooled to below 32 ℃, that is, air cooled, water cooled or oil cooled. In order to prevent cracking, air cooling is often used.

(6) Electromagnetic flowmeter is a kind of surface for volume flow measurement. In the measurement process, it is not affected by the temperature, viscosity, density and conductivity (at a certain scale) of the measured medium. Therefore, the electromagnetic flowmeter can be used to measure the flow of other conductive liquids only after being calibrated with water.