真空淬火，是指实现零件的光洁淬火。零件的淬火冷却在真空炉内进行，淬火介质主要是气(如惰性气体)、水和真空淬火油等。真空淬火已大量应用于各种渗碳钢、合金工具钢、高速钢和不锈钢的淬火，以及各种时效合金、硬磁合金的固溶处理。
Vacuum quenching refers to the smooth quenching of parts. The quenching and cooling of parts are carried out in a vacuum furnace, and the quenching medium is mainly gas (such as inert gas), water and vacuum quenching oil. Vacuum quenching has been widely used in the quenching of various carburizing steels, alloy tool steels, high speed steels and stainless steels, as well as the solution treatment of various aging alloys and hard magnetic alloys.
真空中的淬火有气淬和液淬两种。气淬即将工件在真空加热后向冷却室中充以高纯度中性气体（如氮）进行冷却。适用于气淬的有高速钢和高碳高铬钢等马氏体临界冷却速度较低的材料。液淬是将工件在加热室中加热后，移至冷却室中充入高纯氮气并立即送入淬火油槽，快速冷却。如果需要高的表面质量，工件真空淬火和固溶热处理后的回火和沉淀硬化仍应在真空炉中进行。
There are two kinds of quenching in vacuum: gas quenching and liquid quenching. Gas quenching means that the workpiece is cooled by filling a high purity neutral gas (such as nitrogen) into the cooling chamber after being heated in vacuum. Materials with low critical cooling rate, such as high speed steel and high carbon high chromium steel, are suitable for air quenching. Liquid quenching is to heat the workpiece in the heating chamber, move it to the cooling chamber, fill it with high-purity nitrogen and send it to the quenching oil tank immediately for rapid cooling. If high surface quality is required, tempering and precipitation hardening of workpieces after vacuum quenching and solution heat treatment shall still be carried out in vacuum furnace.