The requirements specified within various pressure vessels and piping codes are mostly due to the chemical makeup and thickness of the material.[1] Codes such as ASME Section VIII and ASME B31.3 will require that a specified material be post weld heat treated if it is over a given thickness.[1] Codes also require PWHT based solely on the micro-structural make-up of the material.[1] A final consideration in deciding the need for PWHT is based on the components' intended service, such as one with a susceptibility to stress corrosion cracking.