According to EN 13458-2:2023, material selection for cryogenic piping systems must account for notch toughness at minimum design temperatures as low as -196°C. Austenitic stainless steels like 304L and 316L are common choices due to their face-centered cubic structure, which retains ductility at cryogenic temperatures. However, welding introduces challenges: heat input control is critical to avoid sensitization and maintain toughness in the heat-affected zone.
A key requirement is impact testing of weld metal and HAZ at the design minimum temperature, typically -196°C for liquid nitrogen or LNG service. EN 13458-2 mandates Charpy V-notch values of at least 27 J average, with no single value below 20 J. Welding procedure qualifications must include these tests, and filler metals should match or exceed base metal toughness.
For thicker sections, PWHT is often prohibited for austenitic stainless steels to avoid carbide precipitation. Instead, careful interpass temperature control (max 150°C) and low heat input (below 1.5 kJ/mm) are used to prevent hot cracking and maintain corrosion resistance. Post-weld acceptance criteria follow EN ISO 5817 level B for highest integrity.
What strategies do you use to verify cryogenic toughness in production welds?
Source: EN 13458-2:2023