Effect of tempering on the strength and toughness of 2 1/4 Cr-1 Mo steel weldments

Hardness, tensile, and Charpy V-notch impact tests were performed on samples prepared from submerged-arc weldments of 2 1/4 Cr-1 Mo steel. The intent was to explore the effect of tempering on the strength and ductility of the alloy in order to assess the potential for developing a high-strength alloy for gasifier pressure vessel service to 300/sup 0/C. Results indicated that good weld metal strength and toughness could be achieved. Limited work on the heat-affected zone of the base metal did not reveal any major problems. We concluded that qualification of a quenched-and-tempered version of 2 1/4 Cr-1 Mo steel with ultimate strength in the range 620 to 758 MPa (90 to 110 ksi) will be difficult for welded gasifier pressure vessels because of a narrow time-temperature tempering window. A minimum ultimate strength requirement of 585 MPa (85 ksi), however, would be much easier to achieve because of the larger window.