The role of molybdenum and its substitute elements in carburized layer has been examined. Among substitute elements, chromium and manganese are effective to raise case hardenability. Chromium is also effective to raise surface carbon content. Boron suppresses over-carburizing. Silicon enhances structure anomalies.
Based on these results, five kinds of molybdenum-saving case hardening steels have been designed. These steels showed good carburizing properties.