Supermartensitic stainless steels have been widely used for line pipe application because of their high strength and excellent corrosion resistance in corrosive conditions. However, field failures due to stress corrosion cracking (SCC) near the fusion line of girth weld joints were found in early applications. Post weld heat treatment (PWHT) was effective to eliminate sensitivity of SCC. In this paper, the effect of PWHT temperature on SCC behavior of low C-13 %Cr steels weld joints in hot acid environments is examined. Low C-13 %Cr-2%Mo supermartensitic stainless steel was welded by GMAW using superduplex stainless steel wire. PWHT temperature was changed from 550 degree C to 850 degree C. Lower PWHT temperature leads to cracking near fusion line of girth weld joints. Higher PWHT temperature leads to environmental cracking in weld metal due to sigma phase precipitate. Adequate PWHT temperature range seems to be from 600 degree C to 700 degree C.
Martensitic stainless steels have been widely used for Oil Country Tubular Goods (OCTG) because they have high strength and excellent corrosion resistance in CO2 gas wells TM. Much attention has been paid to line pipe application of supermartensitic stainless steels as a partial substitute for 22%Cr duplex stainless steels 15-24. Recently assessment of cracking near the fusion line of girth weld joints in field service has been published 25. PWHT at 650 degree C seemed to be effective to prevent cracking 21. Considering practical field PWHT applications, guidance on a range of PWHT temperature will be required. This study will also be effective to understand the mechanism of cracking near fusion line in hot acid environments.
In this paper, the effect of PWHT temperature on SCC behavior of low C-13%Cr-2%Mo supermartensitic stainless steels weld joint manufactured by Gas Metal Arc Weld-Surface Tension Transfer (GMAW-STT) and Pulsed Gas Metal Arc Welding (P-GMAW) methods using superduplex wire in hot acidic production environments is examined.
