SAE 4130 Steel
SAE 4130 is a low-alloy chromium-molybdenum steel (0.80–1.10% Cr, 0.15–0.25% Mo, 0.28–0.33% C) that offers an outstanding combination of strength, weldability, formability, and toughness. Its relatively low carbon content makes it significantly more weldable than higher-carbon alloy steels, and it can be readily gas-welded, arc-welded, or resistance-welded without preheat in thin sections — an essential requirement for aircraft structural fabrication.
In the normalized condition SAE 4130 develops approximately 97,000 psi tensile strength. Quenched and tempered, strengths of 125,000 to 150,000 psi are achievable with excellent notch toughness. This balance of properties has made 4130 one of the most broadly used aerospace structural steels for over seven decades.
Product Forms & Size Range of SAE 4130 Steel
SAE 4130 round bar is available per AMS 6345 in diameters from 0.250 inch through 14.000 inches. Bar is supplied in the annealed, normalized, or quenched and tempered condition. Cold-finished bar is available in smaller diameters for close-tolerance machined parts. Forging quality bar is produced to restricted hardenability requirements where specified.
Seamless mechanical tubing per AMS 6346 is available in outside diameters from 0.375 inch to 10.500 inches with wall thicknesses from 0.028 inch to 2.000 inches. SAE 4130 tubing is widely used for aircraft structural members, push-pull control tubes, and hydraulic lines. Its thin-wall capability and weldability make it ideal for fabricated airframe structures.
Sheet, strip, and plate per AMS 6345 are available in thicknesses from 0.010 inch to 3.000 inches and widths up to 60 inches. Sheet and plate are furnished in the annealed condition for forming and welding, or in the normalized condition when dimensional stability under heat is required.
HEAT TREATMENT OF SAE 4130 STEEL
SAE 4130 is austenitized at 1575–1625°F (857–885°C), quenched in oil or polymer, and tempered between 400°F and 1200°F (204–649°C). Higher tempering temperatures reduce tensile strength and increase ductility and impact toughness. For maximum strength in thin sections, 400°F tempering is used; for weldments and fabricated structures, 1000–1100°F tempering is standard. Post-weld stress relief at 1050°F (566°C) minimizes residual stresses and prevents delayed cracking.
SAE 4140 Steel
Higher-carbon Cr-Mo alloy achieving tensile strengths up to 200 ksi Q&T — ideal for bolts, shafts, and structural fittings.
SAE 4340 Air Melt
Premium Ni-Cr-Mo structural steel achieving 200–260 ksi for the most demanding aerospace airframe and landing gear applications.
Certified Material for Critical Service
SAE 4130 steel for aerospace applications is supplied to AMS 6345 (sheet, strip, plate), AMS 6346 (seamless tubing), and MIL-S-6758 (bars, forgings, rings). Certified mill test reports document heat chemistry and mechanical properties. Full heat-lot traceability is maintained per AS9100 and NADCAP requirements.