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在真空热处理中,用气体作淬火剂的优点很多。但气体淬火比盐浴淬火的冷却速度低,这对于具有中等临界淬火速度的金属来说,气体淬火的应用受到了限制。使用氦淬火,除了具有使用通常气体淬火的优点而外,还因氦的热导率较大(仅次于氢),使用安全的优点而受到重视。在一个相同的炉内环境中,零件放在氦气中比放在氮气或氩气中冷却得快。为了充分发挥氦的热导率高的优点需要了解淬火炉的散热效率(包括评价热交换器、循环风机、气体输送、淬火压力)。
In vacuum heat treatment, the use of gas as a quenching agent has many advantages. However, gas quenching has a lower cooling rate than salt bath quenching, which limits the use of gas quenching for metals with medium critical quenching rates. The use of helium quenching, in addition to the advantages of using conventional gas quenching, is also emphasized by the safety benefits of helium’s greater thermal conductivity (second only to hydrogen). In an identical furnace environment, the part is cooled faster in helium than in nitrogen or argon. In order to give full play to the advantages of high thermal conductivity of helium, it is necessary to know the heat dissipation efficiency of the quenching furnace (including evaluation of heat exchanger, circulating fan, gas delivery, quenching pressure).