Steel

42CrMoS4 IM is a steel quality developed by Corus. The letters IM stand for "Improved Machinability". The improved machinability results in significantly less tool wear. This favourable feature is achieved, among other things by treating the steel in the liquid state with calcium. By this addition, harmful inclusions such as hard aluminumoxide, are modified to soft inclusions, surrounded by manganese sulfide. The lack of hard inclusions leads to improved machinability. In addition, if the cutting speed exceeds a certain value, the modified inclusions will soften and form a protective layer on the tools, which improves the machinability even more.

 

Of the alloyed steel grades, the 42CrMo4 is the most widely used quality in both the mechanical engineering and the automotive industry as a material for gears, shafts and the like. Due to the addition of chromium, this quality has a reasonably low cooling speed and therefore good hardenability. In a refined condition, 42CrMo4 has a fairly high strength and good resistance to varying loads (the so called high fatigue strength). Due to the high carbon content, welding should be avoided as much as possible. If welding is necessary, precautions must be taken to prevent cold tears.