In certain cases, steel during heat treatment when heated above 650o C, decarburizing or loss of carbon from the surface of steel takes place resulting in loss of mechanical properties like fatigue strength. The defect of this nature is termed as Decarburizing of steel. If the presence of oxygen and water vapors, the tendency of carbon towards oxygen and vapors increases above 650oC and carbon from the steel surface starts reacting with environmental gases resulting in depletion of carbon from the steel surface. This depletion of carbon from the steel surface is a function of temperature, time and furnace atmosphere.