Optimization of residual welding stresses in austenitic steel piping: prooftesting and numerical simulation of welding and postwelding processes

The development/modification and qualification of welding technology for generating compressive stresses in austenitic stainless steel piping welds are discussed. The following welding processes are considered: 1. A modified, orbital gas tungsten arc (GTA) narrow-gap welding process with significant improvements over conventional and standard narrow-gap orbital pipe welding, 2. The heat sink welding (HSW) process with internal cooling of the pipe with water or liquefied CO2 gas, and 3. The postwelding process. Last pass heat sink welding (LPHSW) for altering residual stresses in an existing weld. Residual stresses have been measured by using the so-called ring-core as well as radiographic procedures. In support of experimental work required to qualify these welding techniques a numerical simulation effort was undertaken.