Equipment And Process Of Low Temperature Salt Bath Hardening Of AISI201Austenitic Stainless Steel

AISI300series austenitic stainless steels have been widely used in various industries as their excellent corrosion resistance.AISI300series austenitic stainless steels belong to Cr-Ni series stainless steel,but Cr-Mn series austenitic stainless steels which replay part of function of Ni with Mn-N was developed in order to save nickel resources, AISI201austenitic stainless steel is the typical one of Cr-Mn series austenitic stainless steel. The low hardness of austenitic stainless steel (250HV) limits its scope of application. Low temperature salt bath hardening treatment is introduced to AISI201austenitic stainless steel without reducing the corrosion resistance in this paper. The treatment could enhance the surface hardness and extend the scope of application of the steel. The main contents are as follows:A new salt bath furnace temperature controller which was based on STC12C5A60S2microcontroller was developed because of the requirement of high temperature control accuracy from low-temperature salt bath hardening of austenitic stainless steel. Hardware circuit was reliable, low-cost while software had a open-minded design and good adaptability. The special control procedures depending on heat treatment process could be designed. The experimental result showed that the control accuracy of temperature of salt bath furnace satisfied requirements of the process.A salt bath special for low-temperature salt bath hardening of austenitic stainless steel was developed.Furthermore, standards to evaluate the life of the special salt were established.On this basis, the service life and regeneration of the special salt were tested.The experimental result showed that the special salt had a long life and regenerated easily.The salt bath special for low-temperature salt bath hardening of austenitic stainless steel was introduced to low-temperature salt bath hardening of AISI201austenitic stainless steel. Structure properties including hardness, thickness, phase structure, distribution of elements, and wear resistance and corrosion resistance of hardened layer under different processing parameters were investigated. Tests showed that, a hardened layer of moderate thickness (>30μm), high hardness (>1000HV) was formed on the surface of AISI201austenitic stainless steel after low-temperature salt bath hardening. Chromium nitride did not precipitate in the hardened layer whose corrosion resistance was superior to the base body when the treatment temperature was lower than450℃.