T.O.  1-1A-9 TABLE 2-15.  WELDING CHARACTERISTICS - GENERAL, STEELS OTHER THAN STAINLESS (CONT'D) 6150 EAO18G MIL-R-5632 6152 Class 2 8615 E9018G MIL-R-5632 200°-300F Normalize Low hydrogen 8617 Class 2 type electrodes 8620 particularly when low pre- heat and inter- pass tempera- tures are em- ployed are generally used for welding this group. 8735 E10018G MIL-R-5632 200°-300F Normalize Class 2 8630 E9018G MIL-R-5632 300°-500°F Stress Relief Shielded-arc- 1100-1200F carbon moly- or Normalize. bdenum elec- trodes are re- commended. Bare electrodes produce brittle welds. D-6-A ------ ---------- 450°-550°F 575-625, 1-1/2 Weldable in hr cool in still heavy section air to 300F fol- using normal lowed by immedi- techniques re- ate stress relief. quired for Alternate, trans- welding high fer to furnace at hardenable preheat temp and medium carbon normalize at 1725- low alloy steel. 1775, 30 minutes Sections less air cool. than 0.125 in some instances may be welded by the tungsten inert gas pro- cess without pre-heating. 2-144.    The  medium  carbon  (AISI/SAE)  grades  of  the  low  alloy  steels  are  more  difficult  to  weld  than  the  low  carbon grades.    If  welding  of  this  series  is  to  be  successful,  close  control  of  procedures  is  required.    Preheating  is  necessary except for thin 8630-4130,  and even for these grades if shape of part/assembly is complicated.  The medium carbon grades  in  the  as-welded  condition  are  inherently  brittle  and  require  normalizing/stress  relieving  or  heat  treatment  for successful welding.  In some instances for the welding of heavy section, intermediate stress relief is used by heating to stress relief temperature from the pre-heat temperature, holding for 5-6 hours, and then lowering to preheat temperature to complete the weld.  After weld is completed, part is given a final stress relief or heat treated.  For best results, stress relief  or  heat  treatment  should  be  accomplished  immediately  after  welding  before  material  is  allowed  to  cool  below minimum  interpass/preheat  temperature  (for  some  alloys  this  is  a  mandatory  requirement),  and  in  any  case  before material is allowed to cool to room or atmosphere temperature.  Although thin material in grades 4130 and 8630 can be welded without preheat, a preheat temperature of 200°-300°Fis recommended for best results. 2-86