Thermo-mechanical properties of welds in stainless steel is substantially improved by the implementation of a post weld heat treatment that iliminates sigma phase in the heat treated zone and favors niobium carbonitride precipitate formation in a desirable size range. In most cases, post weld heat treated material can be employed in pressurized devices at temperatures exceeding 550° C., which is currently regarded the upper safe temperature limit, and material according to the inventive subject matter was tested at temperature of up to 850° C. without reheat cracking.