Development of Welding Procedures and Filler Materials for Joining High Strength Low Alloy Steels

The object of this program was to develop welding procedures and filler materials for joining martensitic and bainitic steels in the 180 to 200 ksi yield strength range. Martensitic steels studied were HP 9-4-20, HP 9-4-25, AMS 6435, Vasco Jet X-2, and D6AC. The HP 9-4-XX steels were successfully joined using the TIG process without a subsequent post-heat. Reduced porosity and improved mechanical properties were obtained in weldments in the HP 9-4-20 steel by making additions of Ti and Al to filler wires of base metal composition. D6AC steel TIG weld joints were of acceptable strength, but a definite lack of ductility was present and porosity in the weld deposits occurred often. The AMS 6435 and Vasco Jet X-2 steels could not be successfully joined without post-heat. Bainitic steels examined consisted of HP 9-4-45 1/2-in. plate and 0.090-in. sheet and D6AC 1/2-in. plate. In no instance did welds in the HP 9-4-45 steel plate yield tensile properties comparable to that of the parent metal. Acceptable strength was obtained in the sheet material, but low ductility was present. D6AC steel was successfully TIG welded, but, the heat-affected zones were weak.