According to a 2025 technical review in Welding in the World, sensitization remains a critical metallurgical risk when welding austenitic stainless steels, particularly in the heat-affected zone (HAZ) of thicker sections.
Sensitization occurs when chromium carbides precipitate at grain boundaries during cooling through the 800°C to 500°C temperature range. This depletes chromium adjacent to the boundaries, making the HAZ susceptible to intergranular corrosion in service.
Key factors that increase sensitization risk include:
• Carbon content above 0.03% (use low-carbon L-grades or stabilized grades like 321 or 347)
• Prolonged exposure in the sensitization temperature range during multi-pass welding
• Thick sections with slow cooling rates that extend time in the critical zone
Per the same review, control measures are well established: limit heat input, use filler metals with lower carbon content, and apply solution annealing (1050°C to 1100°C) followed by rapid quenching when practical. For field welds where PWHT is not feasible, low-carbon or stabilized grades are the reliable choice.
Understanding these mechanisms helps welding engineers select materials and procedures that avoid costly corrosion failures.
How do you verify that your stainless steel welds are free from sensitization in critical service?
Source: Welding in the World, 2025