SAE 4335 Steel
SAE 4335 is a nickel-chromium-molybdenum alloy steel with a nominal composition of 1.65–2.00% Ni, 0.70–0.90% Cr, 0.20–0.30% Mo, and 0.33–0.38% C. The elevated nickel content relative to standard 4130/4140 provides superior hardenability in large section sizes and significantly improved low-temperature impact resistance. Tensile strengths of 180,000–240,000 psi are achievable depending on tempering temperature.
SAE 4335 is well suited to applications requiring a high-strength alloy steel in thick sections (greater than 3 inches) where simpler Cr-Mo grades may not develop full hardness through the cross-section. Its combination of hardenability, fracture toughness, and fatigue resistance makes it an effective choice for aerospace structural forgings and pressure-bearing components.
Product Forms & Size Range of SAE 4335 Steel
SAE 4335 round bar and forging stock per AMS 6429 is available in diameters from 0.750 inch to 14.000 inches. Bar is supplied annealed for machining or in the normalized condition. Large-diameter forging billet is commonly used for aircraft bulkhead forgings and thick structural fittings where section size exceeds the through-hardening capability of 4130 or 4140.
SAE 4335 round bar and forging stock per AMS 6429 is available in diameters from 0.750 inch to 14.000 inches. Bar is supplied annealed for machining or in the normalized condition. Large-diameter forging billet is commonly used for aircraft bulkhead forgings and thick structural fittings where section size exceeds the through-hardening capability of 4130 or 4140.
HEAT TREATMENT OF SAE 4335 STEEL
Austenitize SAE 4335 at 1525–1575°F (829–857°C), oil quench, and temper at 350–1100°F (177–593°C). The higher nickel content increases hardenability, so full through-hardening is achievable in larger sections than comparable 4130 or 4140. For aerospace structural applications, double tempering is recommended to ensure complete martensite transformation and full dimensional stabilization. Tempering at 600°F produces approximately 220 ksi UTS; at 1000°F, approximately 170 ksi with significantly higher toughness.
SAE 4330 Steel
Ni-Cr-Mo-V alloy structural steel with vanadium for maximum fracture toughness at 180–220 ksi — a common design alternative to 4335.
4340 Air Melt Steel
The most widely specified Ni-Cr-Mo structural steel for aircraft primary structure — routinely achieves 200–260 ksi.
Certified Material for Critical Service
SAE 4335 steel is supplied to AMS 6429 (bars, forgings, mechanical tubing) and AMS 6430 (sheet, strip, plate). Certified mill test reports document composition and mechanical properties per heat and lot. Fracture toughness testing per ASTM E399 is available on request for fatigue-critical applications.