Performance of repair welds on aged Cr-Mo piping girth welds

This article documents the results of an industry survey of weld repair practices and describes the results of experimental evaluations performed on service-aged 21/4 Cr-1Mo steel piping using SMAW with both conventional postweld heat treatments and temper bead repair techniques. The overall results of this program provide substantial evidence that service-aged piping systems can be successfully weld repaired with and without postweld heat treatments and that life extension by several decades is achievable under the right design and repair conditions. Weld repairs performed on degraded exservice welds resulted in restoration or improvement of tensile and creep properties. Microhardness test results within the heat-affected zone of each weldment indicated that the temper bead weld repairs produced only slightly higher peak hardness values than those measured for the fully postweld heat treated repairs. Finally, in terms of toughness, temper bead weld repairs consistently produced higher impact properties than those measured for the postweld heat treated weldments. Gas tungsten arc weld repairs with postweld heat treatment resulted in the best combination of tensile strength, uniform microhardness distribution across the weld, Charpy toughness, and creep rupture life.