SAE 6150 Steel
SAE 6150 is a chromium-vanadium alloy steel (0.80–1.10% Cr, 0.15% V minimum, 0.48–0.53% C) noted for its outstanding fatigue resistance and toughness at high hardness levels. The vanadium addition forms fine carbides that pin grain boundaries, producing a refined austenite grain that significantly improves fatigue crack initiation resistance. This makes 6150 the preferred choice for springs, leaf springs, torsion bars, and highly stressed shafts subject to cyclic loading where fatigue life governs the design.
SAE 6150 is typically heat treated to 190,000–210,000 psi tensile strength for spring applications, with good ductility and toughness retained at this strength level. The fine carbide dispersion resulting from the vanadium addition also provides excellent wear resistance when the steel is induction or case hardened.
Product Forms & Size Range of SAE 6150 Steel
SAE 6150 round bar per AMS 6448 is available in diameters from 0.375 inch to 8.000 inches. Bar is produced in the annealed condition for machining and spring coiling operations. Forging quality grades are available for crankshafts, axles, and structural forgings. Cold-drawn bar is available for shafts and precision machined parts.
SAE 6150 round bar per AMS 6448 is available in diameters from 0.375 inch to 8.000 inches. Bar is produced in the annealed condition for machining and spring coiling operations. Forging quality grades are available for crankshafts, axles, and structural forgings. Cold-drawn bar is available for shafts and precision machined parts.
HEAT TREATMENT OF SAE 6150 STEEL
Austenitize SAE 6150 at 1550–1600°F (843–871°C), oil quench, and temper at 700–900°F (371–482°C) for spring applications targeting 190,000–210,000 psi. The tempering temperature must be carefully controlled — too low (below 600°F) risks tempered martensite embrittlement. Shot peening of formed spring surfaces after heat treatment induces compressive residual stresses that double or triple the fatigue life of finished springs. Stress relief at 450°F after shot peening stabilizes the beneficial compressive stress field.
SAE 52100 Steel
High-carbon bearing steel for rolling contact applications — outstanding hardness to 66 HRC and contact fatigue life for precision bearings.
SAE 8620 Steel
Ni-Cr-Mo carburizing steel for case-hardened gears and shafts — hard wear-resistant case over a tough, impact-resistant core.
Certified Material for Critical Service
SAE 6150 steel is supplied to AMS 6448 (bars and forgings) and AMS 6455 (sheet, strip, plate). Material certifications document composition including minimum vanadium content and mechanical properties per heat and lot. Fatigue testing of finished spring components is typically required per the applicable aircraft or military spring specification.