Heat treating case hardened steel - to avoid forming a mixed grain size structure with corresponding poor mechanical properties

摘要

The steel, eiehter plan C or low alloy type, contains 0.009-0.02% N together with Al and/or Nb in an amt. 0.02-0.1%. The steel is heated to =1150 degrees C for =15 mins. dissociating Al and Nb cpds. and to produce a coarse austenite grain size. The steel is the hot worked at =1000 degrees C to produce a grain size equivalent to ASTM No. 5 grade, and the steel than pref. cooled at =2 degrees C/sec.