Available electric stove, stainless steel forging pre-heating can also be used flame furnace.Production in the flame furnace, because of its lower cost. Furnace gas atmosphere should be kept neutral or slightly oxidizing. Austenitic stainless steel, not a reducing atmosphere, in order to avoid increasing carbon or chromium depletion and intergranular corrosion resistance decreased; martensitic stainless steel, high carbon content, can not be over-oxidation of the atmosphere, to avoid serious decarburization.
Flame furnace heating should also be noted that gas remained essentially free of hydrogen sulfide and other sulfur-containing pollutants, especially of high-nickel steel, but can not use the sulfur content of fuel, the sulfur penetrate steel with nickel formation of NiS (melting point 797 ° C) or Ni + Ni3S2 eutectic (melting point 645 ° C), it is mainly distributed on the grain boundaries, causing the plastic drop of stainless steel process, the formation of cracks in the forging.
Below 700 ~ 800 ℃, the thermal conductivity of stainless steel is smaller than the thermal conductivity of ordinary alloy steel. However, the stainless steel thermal conductivity increases with increasing temperature in the range of 700 ~ 800 ℃ and the thermal conductivity of the alloy steel line. Therefore, for the rough greater than 100mm in diameter shall be used for the two heating systems: in the warm-up stage, to maintain the furnace temperature of 800 ~ 850 ℃ in order to slow down the rate of heating; in the heating and soaking stage, to maintain a higher oven temperature (the beginning of forging temperature limit), in order to quickly heated to the initial forging temperature.
Precision forgings, high surface quality requirements or margin smaller forgings, such as compressor blades, heating is often on the rough surface coated with a layer of protective coatings (glass lubricant), and then within the ordinary furnace heating . Glass protective coatings to protect metal from oxidation and contamination, it is forging lubricant processing.
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