The application of low pressure vacuum carburizing technology and equipment under deep carburizing conditions were introduced,and It is pointed out that as a quick deep carburizing technology it can reduce process time and production cost as well as increase productivity substantially.

This paper searches the relation between the effective hardening layer and depth of carburizing case measured by the metallographic method.

The results show that the difference between the metallographic method and hardness method is small, so we can adopt the metallographic method during heat treatment inspection of 20Cr steel; and the depth of carburizing case can be calculated from the outside face to where the pearlite contents are 50% when using metallographic method.

This paper compared several testing methods of carburized depth of high air pressure drill and evaluafed their accurately and practicality.

Induction voltage values of the eddy current testing coil with different carburized depths are calculated.

By using a nonlinear reducing of the data, a carbon distribution model and a mathematical model referring to the relationship between the case depth and the electromagnetic characteristics are built.

The kinetics of austenite grain growth,structure and mechanical property of carburized case were studied on rare\|earth deep carburizing steel 20Cr2Mn2MoRE and were compared with 20Cr2Mn2Mo.