抄録
To examine the practically useful properties of chromium and chromium-molybdenum steels now in current use as non-nickel case-hardening steels and to find the higher strength steels in substitution for the high nickel-chromium case-bardening steels (Ni4-5%F, Cr0·5-1%), iuvestigations were made on the mechanical properties, mass effect and carburizing characteristics of chromium and chromiwu-manganese steels with 1-3% Cr. The results obtained were summarized as follows:
(1) 1-1·2% manganese increases the tensile strength of the 1% and 2% chromium-molybdenum steels without decreasing the tenacity, but more manganese diminishes the Charpy impact value while increasing the tensile strength.
(2) Some kinds of alloy steels containing 3% Cr were found to be more excellent in the mechanical properties and the mass effect than 2% Cr-Mn steels, especially the 3% Cr-Mo steels were proved to have more superior mechanical properties than 2/2% Cr-Ni-Mo steel or 3/2% Cr-Ni-Mo steel whichcontains 1-2% Ni.
(3) From the viewpoint of mass effect, the 3% Ni steel may be substituted by steels with 1% Cr or 1·5%Mn, and the 4% Ni-Cr steel by those with 2% Cr and 1% Mn.
(4) These kinds of alloy steels are apt to be subjected to over-carburizing, forming a globular carbide zone on the carburized surface which makes the case brittle. Some especially compounded carburizing agents proved to be effective in preventing the over-carburizing.
