Precautions for Vacuum Heat Treatment of AISI4140 (42CRMO) Mold Steel or Parts

Die steel contains more alloying elements, and elements with higher vapor pressure (such as AL, Mn, Mn, Cr, Si, Pb, Zn, CU, etc.) tend to evaporate when heated in vacuum, so the vacuum degree of quenching heating should be controlled properly. To prevent the volatilization of alloy elements, especially the steel with the highest Cr content.

1.In order to reduce the thermal effect and structure stress of heating die steel or parts due to the difference of internal and external temperature, the complex or large-section die parts should be preheated many times, and the heating rate should not be too fast, This is one of the keys to reducing or preventing deformation.

2.High speed steel high Cr steel, 3Cr2W8v steel and other large section gas quenching die parts should be recommended as far as possible in the high pressure gas quenching furnace for processing. If the air-cooling speed is not enough for oil quenching, air-cooled oil quenching must be used to prevent white bright layered structure on the surface of the workpiece after oil quenching.

3.The vacuum quenching heating temperature can be basically the same or slightly lower as that of salt bath heating and air heating.However, it should be noted that the workpiece heating rate is much slower than the furnace temperature when the temperature is rising, so the average temperature and the holding time should be appropriately prolonged depending on the charging condition.

4.Whether the charge is reasonable or not depends on the quality of the heat treatment. Considering that the 42CRMO vacuum heating is based on radiation, the mold parts should be placed properly in the furnace, and the small parts should be separated by a metal mesh to make the heating and cooling uniform.