Cryogenic properties of austenitic weld metals deposited by covered electrodes vary widely from grade to grade. Within any specific grade, optimum properties may be obtained if weld metal is: low in ferrite (preferably 0 FN); low in nitrogen (preferably < 0.05%); low in carbon (preferably < 0.04%); high in nickel - (maximum permissible); and deposited by a lime-type electrode.Nickel was the only element investigated that improved weld metal toughness at cryogenic temperatures, suggesting that the nickel content of any specific grade should be maintained as high as possible.Thus, nickel, nitrogen, ferrite, and carbon contents combine as prime factors to be controlled for maximum toughness of SMA weld metal at cryogenic service temperatures. The type of electrode covering is of importance particularly if it is necessary to maximize properties.Regression analysis of the wide variety of materials tested at - 196°C (−320°F) resulted in the following model formulae.Toughness of weld metal deposited by lime-type electrodes:Lateral expansion (CVN) = 36.55 − 133.8 (%C) − 0.20 (%Mn) − 1.13 (%Cr) + 1.72 (%Ni) − 2.34 (%Mo) − 177.2 (%N) mils (1)Toughness of weld metal deposited by titania-type electrodes:Lateral expansion (CVN) = 33.72 − 133.8 (%C) − 0.20 (%Mn) − 1.13 (%Cr) + 1.72 (%Ni) − 2.34 (%Mo) − 177.2 (%N) mils (2)(Conversion factor: 1 mil = 25.4 μm). For known weld metal compositions, these models enable weld metal toughness at - 196°C (−320°F) to be reliably predicted.Regression analysis formula for lateral expansion calculations had a standard deviation of ± 0.17 mm (± 6.5 mils). This means that a calculated value of 0.56 mm (22 mils) was essential to reasonable assure a lateral expansion of 0.381 mm (15 mils) after testing at - 196°C (−320°F). If compositions are restricted to the ranges of AWS A5.4–69, low nitrogen heats of core wire become mandatory. Such stainless steel is not always readily available, posing a problem for the filler metal producer.