Salt Bath Quenching for Minimum Distortion

Conventional quenching of some steel parts in water, brine, oil or polymer solution can cause unacceptable distortion and in some cases non-uniform hardness or even cracking. Quenching in molten salt minimizes distortion and cracking. There is no vapor phase barrier in the initial stage of quenching which is common with most other liquid quenchants and heat removal is fast. This helps in achieving more uniform hardness and more consistent physical properties. Salt is thermally so stable that it provides trouble-free performance for many years simply by compensating for the drag-out losses. Its quench severity can be easily altered by changing its temperature, agitation and/or water content for various different requirements. It can be recovered from wash water simply by evaporation. These features in conjunction with the advances made in equipment make salt bath quenching safer, nonpolluting, fully automated and programmable; and economically attractive. It is successfully applied by the manufacturing industry in carrying out processes such as austempering, martempering and their numerous modifications. In fact, there is no practical alternate to salt for most of these processes. As a result, use of salt bath quenching continues to grow with newer plants coming on stream with much larger capacity than ever before.