Cryogenic Technique for Processing Steel Treatment

Abstract

Cryogenics or deep freezing have been around for quite some time. There is documented research from as far back as the 1930’s where German companies used it on components of jumbo aircraft engines. Cryogenic processing had its US origins in the 1940s. Cold treatments or sub zero treatments are done to make sure there is no retained austenite during quenching. Cryogenics is a relatively new process and to eliminate retained austenite, the temperature has to be lowered, but one that using correct procedures can bring substantial economic benefits. In cryogenic treatment the material is to be deep freeze temperatures of as low as -185°C (-301℉). The austenite is unstable at this temperature and the whole structure become martensite. This is the region to use cryogenic treatment. Processing is not a substitute for heat treating if the product is properly treated or if the product is over heated during remanufacturing or if it is over stressed during use. Cryogenic processing will not in itself harden metal like quenching and tempering, it is an additional treatment to heat-treating. The benefits of this process includes; reduction of abrasive and adhesive wear, improved machining properties resulting from the permanent change of the structure of the metal, reduction of the frequency and cost of tool remanufacturing and reduction of likelihood of catastrophic tool failure due to stress fracture. In the present study, the cryogenic technique is applied by exposing the steel to deep freezing environment (-320℉) for 24 hours and slowly raised to room temperature. The results are correlated with standard results. Cryogenic processing makes changes to the structure of the materials being treated and dependent on the composition of the material, it performs three things; viz. retained austenite turned to martensite, carbide structures are refined and stress is relieved.