HB 250 - 285 AISI 4340 Alloy Steel Fatigue Resistance With Fair Weldability

AISI 4340 Alloy is a high-performance, low-alloy steel renowned for its exceptional strength, toughness, and fatigue resistance. This material is commonly used in demanding applications where high mechanical properties and reliability are required, particularly in aerospace, automotive, and heavy machinery industries.

• Carbon (C): 0.38-0.43% - Provides high strength and hardness while maintaining good toughness
• Manganese (Mn): 0.60-0.80% - Enhances hardness and tensile strength
• Chromium (Cr): 0.70-0.90% - Increases corrosion resistance and wear resistance
• Nickel (Ni): 1.65-2.00% - Adds toughness and impact resistance
• Molybdenum (Mo): 0.20-0.30% - Enhances high-temperature strength
• Silicon (Si): 0.15-0.35% - Improves strength and mechanical properties
• Phosphorus (P): ≤0.035% - Maintains toughness and reduces brittleness
• Sulfur (S): ≤0.040% - Enhances machinability and strength

• Tensile Strength: 740-930 MPa (after heat treatment)
• Yield Strength: ≥500 MPa
• Elongation: ≥15%
• Density: 7.85 g/cm³
• Hardness: HB 250-285 (as annealed)
• Impact Toughness: High resistance to dynamic loading

• Annealing: Improves machinability and ductility
• Normalizing: Refines grain structure for enhanced strength
• Quenching and Tempering: Increases hardness and strength
• Carburizing: Adds surface hardness while maintaining tough core

• Aerospace: Aircraft components, landing gear, fasteners
• Automotive: High-performance engine parts, crankshafts, camshafts
• Heavy Machinery: Gears, shafts, axles
• Oil & Gas: Downhole tools, drill collars
• Tooling: Dies, molds, cutting tools

AISI 4340 Alloy Steel combines exceptional strength, toughness, and fatigue resistance with good ductility and impact resistance. Its balanced chemical composition and versatile heat treatment options make it ideal for critical applications in aerospace, automotive, heavy machinery, oil and gas, and tooling industries.