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| Specification | Value |
|---|---|
| UNS Number | G43400 |
| Tensile Strength | 1080–1240 MPa |
| Yield Strength | 860–1100 MPa |
| Density | 7.85 g/cm³ |
| Hardness | 28–34 HRC |
| Max Service Temperature | 425°C |
| Element | Composition (%) |
|---|---|
| C | 0.38–0.43 |
| Ni | 1.65–2.00 |
| Cr | 0.70–0.90 |
| Mo | 0.20–0.30 |
| Mn | 0.60–0.80 |
| Si | 0.15–0.35 |
| P | ≤0.035 |
AISI 4340 fasteners derive their strength from a carefully balanced alloy composition containing nickel, chromium and molybdenum. Nickel enhances toughness and impact resistance, while chromium improves hardenability and wear resistance. Molybdenum reduces temper embrittlement and stabilises mechanical properties at elevated temperatures. Carbon content, typically around 0.40%, provides the hardness required after quenching and tempering. Manganese and silicon act as deoxidisers and further contribute to hardenability, ensuring consistent through-thickness strength in larger fastener sections.
This alloy composition gives 4340 fasteners exceptional tensile and yield strength, high fatigue resistance and excellent toughness even at low temperatures. Its deep hardenability allows uniform mechanical properties in thick bolts and studs, while moderate corrosion resistance can be improved through coatings or plating. Good heat resistance up to 425°C makes it suitable for structural, automotive, aerospace and heavy machinery fastener applications where high strength-to-weight ratio and reliability under dynamic loading are essential.
Specifications
AISI 4340 Fasteners are high-strength alloy components defined by their mechanical properties, dimensional tolerances, and technical data for demanding service conditions. Their specifications typically emphasize tensile strength, hardness, and size options, with material performance supporting reliable fastening in critical structural and mechanical applications.
| Property | Value |
|---|---|
| Tensile Strength | 1080–1240 MPa |
| Yield Strength | 860–1100 MPa |
| Elongation | 10–14% |
| Reduction of Area | 40–50% |
| Hardness | 28–34 HRC |
| Modulus of Elasticity | 200 GPa |
| Thermal Expansion | 12.3 µm/m°C |
| Thermal Conductivity | 44.5 W/m·K |
| Density | 7.85 g/cm³ |
| Melting Range | 1420–1460°C |
| Heat Treatment | Quenched & Tempered |
| Max Service Temperature | 425°C |
| Specification | Details |
|---|---|
| Bolt Standard | ASTM A490, ASME B18.2.1 |
| Stud Bolt Standard | ASTM A320, MSS SP-75 |
| Nut Standard | ASTM A194, ASME B18.2.2 |
| Washer Standard | ASME B18.21.1 |
| Thread Form | UNC, UNF, Metric Coarse/Fine |
| Diameter Range | M6–M100 / 1/4"–4" |
| Length Range | 10mm–500mm |
| Available Forms | Bolts, Studs, Nuts, Washers |
| Custom Sizes | Available on request |
| Manufacturing Standards | ISO 898-1, DIN 267 |
| Inspection Standards | ASTM A370, NACE MR0175 |
| Surface Finish | Plain, Zinc, Hot-Dip Galvanised |
Applications
