Quenching Crack-Sensitive Steels – Effects of Hardenability and Quench Rate

Many parts that require high strength and/or high wear resistance are quench hardened from steel grades that are sensitive to cracking during quenching.  A relatively simple bushing geometry was prone to cracking along one side which had been ground flat.  The cooling during the quench was not uniform circumferentially because of this wall thickness difference.  Computer simulation of this bushing geometry was undertaken to investigate the effect of quench rate, steel hardenability and fracture resistance on susceptibility to cracking.  Quench rates ranged from low pressure to high pressure gas quenching, to oil quenching.  Steel chemistries included grades 1040, 4140 and 52100.