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Table 2 . Mechanical properties ( typical ) of several grades of AWS A5.9 ER316L solid wire welded in PA position with GTAW .
Grade
Yield Strength MPa
Tensile Strength MPa
Elongation
Impact Toughness @ -196 o C
FN WRC92
316L 470 650 38 % > 32 J 7
OK Autrod 316L
Exaton 19.12.3 . L CRYO
470 600 33 % 75 J 7
410 610 38 % 90 J 3
products of the same stainless steel grade . The chemistry and microstructure of the Exaton 19.12.3 . L CRYO grade is such that it ensures a very low ferrite level of FN 2 – 3 ( WRC 92 ). This property significantly improves the resistance of the weld metal to micro-fissuring . Whilst the tensile and yield strength is around the same as the standard 316L , the biggest improvement is in the impact toughness at cryogenic temperatures , resulting in an increase to 90J @ -196 ° C , up from > 32J for a standard grade ( it should be noted that the current specification requirement for TUV approval of Charpy impact toughness @ -196 ° is 32J ; however , the typical requirement specified by an end user is 40J ). Further testing is currently in progress on the new cryogenic grade filler metal to obtain Charpy impact test results at -269 ° C . The objective is to prove the integrity in the weldments installed in liquid hydrogen equipment . This filler metal research is important , as hydrogen is another liquid gas
Figure 2 . The FCC atomic structure of austenite provides low-temperature toughness .
that is becoming more prevalent as a fuel source . For example , the UK Government has a strategy to develop 5GW of hydrogen production capacity by 2030 . The liquefaction temperature of hydrogen is -253 ° C , so the requirements for the mechanical properties and testing temperatures will necessitate that liquid helium will need to be used , which is a significant step up in the design parameters used for LNG .