The  structure  and  properties  of steel  with  three  kinds  heat  treatment  processes  -  quenched  at  880  ℃  for 30 min oil cooling + tempered at 600 ℃ for 60 min air cooling

normalized at 860 ℃ for 30 min air cooling and two-phase region  subcritical  treated  at  780  ℃  for  30  min  air  cooling

in  order  to  get  a  simplified  heat  treatment  process  of 40SiMnCrNiMo for rock drill tools. The results showed that the HV microhardness value at bainite region of subcritical heat treated steel lowed than that of normalized steel and V- notched impact energy was 30 J higher than that of normalized steel (12J)and  approached  to  that  of quenched  and  tempered  steel(40  J).  The  test  for  service  life  of rock  drill  tools  indicated  that as compared with average  10.78 m drill pace of advance of normalized steel tool

the average drill pace of advance of suberitical treated steel tools was  108.30 m to meet the requirement of use and to be available to replace quenched and tempered drill tools.