The optimal carbon content of high-speed steels

Abstract

1. The secondary hardness and red hardness of high-speed steels increase with the carbon content up to a specific concentration close to the "quasieutectoid", which is above that of standard steels, and decrease with further increase of the carbon content. 2. The highest hardness and red hardness occur at carbon concentrations around 1% for steels R18 and R12, around 1.15% for steel R12F3, and 1.05–1.10% for tungsten—molybdenum steels. The hardness reaches HRC 65.5-67 and the red hardness (at HRC 60) 625–635°C, i.e., values reached in high-vanadium steels R9F5 and R14F4, which take a poor polish. 3. In steels with an elevated carbon content, ferrite is absent on heating above the pearlitic transformation range, which ensures more complete solution of the carbides. In these steels the precipitation of carbides during tempering occurs in a narrow temperature range, due to which the carbides are more dispersed and more uniform in composition and size than in steels with a lower carbon content. 4. It is expedient to increase the carbon content to 1.0–1.05% in tungsten-molybdenum steels, particularly in R6M5 for use in place of high-vanadium steels with high productivity, since the mechanical properties are better as well as the surface finish.