Official Answer
Answer
Carbon steel (SAE 1070) undergoes a 'Ductile-to-Brittle Transition' (DBT) at low temperatures. Below the transition temperature, the material's impact toughness drops sharply, and it can no longer plastically deform to relieve stress. In subsea oil and gas applications (which can reach near-freezing or even lower in Arctic conditions), any shock load can cause the ring to shatter. Engineers mitigate this by using austenitic stainless steels (300 series) or nickel alloys (Inconel), which do not exhibit a DBT and remain tough and ductile even at cryogenic temperatures.
