SAE 52100 Steel
SAE 52100 is a high-carbon chromium bearing steel (0.98–1.10% C, 1.30–1.60% Cr) specifically engineered for outstanding hardness, wear resistance, and contact fatigue life. When through-hardened, it achieves surface hardness up to 66 HRC with a hard, uniform martensitic microstructure throughout the cross-section. These properties make 52100 the world standard bearing steel for precision rolling element bearings, aerospace bearing races, and ball-bearing components.
The combination of high carbon content and chromium provides a fine dispersion of carbide particles that resist wear and maintain dimensional stability under cyclic contact loads. SAE 52100 is produced to tightly controlled cleanliness requirements (AMS 2301) for aerospace applications, as non-metallic inclusions are the primary fatigue crack initiation sites in rolling contact applications. Premium VAR grades offer further improvement in inclusion cleanliness for the most demanding aerospace bearing applications.
Product Forms & Size Range of SAE 52100 Steel
SAE 52100 round bar per AMS 6440 is available in diameters from 0.250 inch to 6.000 inches, typically in the spheroidize-annealed condition to provide optimal machinability for bearing component manufacture. Bar is produced to tight dimensional tolerances and surface quality standards. Wire rod for ball manufacture is available in diameters from 0.188 inch to 2.000 inches.
SAE 52100 seamless tubing per AMS 6440 is available for bearing outer ring blanks and large hollow bearing components. Tubing minimizes material removal compared to bar stock for ring-type bearing components, providing significant cost and material efficiency advantages for large-diameter bearing production.
HEAT TREATMENT OF SAE 52100 STEEL
SAE 52100 bearing components are austenitized at 1500–1550°F (816–843°C) for a controlled time to dissolve carbides while avoiding grain growth, then oil quenched and tempered at 250–350°F (121–177°C) to achieve hardness of 60–66 HRC. A cryogenic treatment at -100°F (-73°C) or below after quenching and before tempering minimizes retained austenite, improving dimensional stability in precision bearing applications. Secondary hardening does not occur in 52100.
SAE 8620 Steel
Ni-Cr-Mo carburizing steel for case-hardened gears and shafts where a hard case with tough core is required instead of through-hardening.
SAE 6150 Steel
Chromium-vanadium alloy with excellent fatigue resistance — used for springs, leaf springs, and torsion bars in aerospace and defense applications.
Certified Material for Critical Service
SAE 52100 steel is supplied to AMS 6440 (bars, wire, forgings, tubing) and AMS 6444 (bars and forgings, premium grade). Aerospace-grade 52100 must comply with AMS 2301 inclusion cleanliness requirements. Material certifications document composition, hardness, and cleanliness per heat and lot.