Official Answer
Answer
Carbon steels like SAE 1070 undergo a ductile-to-brittle transition (DBTT) at low temperatures. In cryogenic applications (below $-40^\circ C$), the fracture toughness $K_{Ic}$ drops precipitously, making the ring prone to shattering under impact or even during installation. For these applications, austenitic stainless steels like 302 or 316, or nickel alloys, must be used as they retain their face-centered cubic (FCC) structure and toughness down to absolute zero.
