Cryogenic Residual Stress

This paper deals with the overview of residual stresses produced by shallow and deep cryogenic treatment in steel. First, the two classification of cryogenic treatment, namely Shallow (SCT, -80°Cx 5h) and Deep Cryogenic Treatment (DCT, -196°Cx 24h) were discussed. Then the definition of and classification of residual stresses, material processing route and the x-ray diffraction methods to measure streses are discussed. Finally, how the cryogenic treatment increases the compressive residual stresses are detailed. The effect of tempering on residual stresses is also discussed. Researchers found that there are increases in the compressive residual stress in steels are subjected to deep cryogenic treatment before tempering. It is also revealed

Residual stresses are the stresses that remain within a component after the original cause of the stresses (external forces, heat gradient) has been removed. Kalpakjian, 1985 pointed out that the residual stresses remain along a cross section of the component, even without the external cause. Samant and Dahotre (2008) stated that these internal stresses become evenly balanced by themselves. They existed in a free body that had no external forces or constraints acting on its boundary.

Before the engineer or metallurgist commits to measuring residual stress in some component or work piece, one must be sure that the reason for the measurement is clearly understood. According to the Handbook of Residual stress and deformation of steel (Ruud, 2002), the major reasons for residual stress are:

1. Failures that are suspected as being caused by fatigue, stress corrosion, corrosion fatigue or hydrogen embrittlement.

2. Assessment for the continued serviceability of a component, for example, life assessment which is usually focused on a concern for in-service

It finds greater benefits to the real time application of steel components in automotive and armament industries. Some of the components are axle shafts, crankshafts, connecting rods, gears, rifle barrels, crown wheel and pinion.

2.0 Mechanism of Cryogenic Treatment Most researchers and scientists believe that the shallow and deep cryogenic treatment improves hardness and wear resistance of steels.

Conventional Heat Treatment

In the general sense, heat treatment may be defined as an operation or combination of operations involving the heating and cooling of a metal or alloy in the solid state for the purpose of attaining certain desirable conditions or properties. The conventional heat treatment procedure is explained by Kamenichny (1969). It consists of heating metals and alloys to a certain temperature, holding and cooling them at various rates with the aim of altering their structure and properties. Each of the heat treatment process comprises the following operations.

1. Heating to a prescribed temperature

2. Soaking for certain period to complete the structural changes

3. Cooling at a prescribed