4140 is a 1% chromium-molybdenum medium hardenability general-purpose high-strength steel, usually hardened and tempered in the tensile range of 850-1000 Mpa (condition T). 4140 now have improved machinability, which greatly increases feed and/or speed, while extending tool life without affecting mechanical properties. The prehardening and tempering 4140 can be further case hardened by flame or induction hardening and nitriding.