JIANGSU MITTEL STEEL INDUSTRIAL LIMITED
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AISI 4340 steel (UNS G43400) is an ultra-high strength medium carbon low alloy steel, which combines deep hardenability, high ductility, toughness and strength, and has high fatigue resistance and creep resistance. It is not particularly affected by tempering and embrittlement, and exhibits good strength retention at high temperatures and is not easily softened. In thin sections, this steel is air-hardened. In practice, it is usually oil quenched.
The following tables and lists give 4340 alloy steel datasheet and specification including chemical composition, physical properties and mechanical properties, heat treatment, welding, etc.
AISI 4340 steel material chemical composition is listed in the following table based on cast analysis.
| 4340 Chemical Composition, % | ||||||||||
| ASTM | Steel Grade (UNS) | C | Si | Mn | P (≤) | S (≤) | Ni | Cr | Mo | Notes |
| ASTM A29/A29M | 4340 alloy steel (UNS G43400) | 0.38-0.43 | 0.15-0.35 | 0.60-0.80 | 0.035 | 0.04 | 1.65-2.00 | 0.70-0.90 | 0.20-0.30 | Steel Bars, Carbon and Alloy, Hot-Wrought |
| ASTM A322 | Steel Bars, Alloy, Standard Grades | |||||||||
| ASTM A519/A519M | Seamless Carbon and Alloy Steel Mechanical Tubing | |||||||||
| ASTM A646/A646M | Premium Quality Alloy Steel Blooms and Billets for Aircraft and Aerospace Forgings | |||||||||
The tables below list AISI 4340 steel properties, including physical and mechanical properties.
4340 alloy steel physical properties are given in the following lists, including density, thermal expansion, elastic modulus, thermal conductivity, specific heat capacity and electrical resistance.
Notes:
| Physical Properties | ||
| Density, g/cm3 (lb/in.3) | 7.85 (0.284) | Conditions |
| Melting point, °C (°F) | 1505 (2740) | – |
| Specific heat capacity, J/kg·K (Btu/lb ·°F) | 475 (0.114) at 20℃ | – |
| Modulus of Elasticity, GPa (ksi) | 205 (29700) | – |
| Bulk Modulus, GPa (ksi) | 140 (20300) | – |
| Poisson’s Ratio | 0.29 | – |
| Shear Modulus, GPa (ksi) | 80 (11600) | – |
| Thermal conductivity, W/m·K (Btu/ft · h ·°F) | 44.5 (25.73) | – |
| Coefficient of thermal expansion, 10-6/K (μin./in. ·°F) | 12.3 at 20-100 ℃ (68-212 °F) | Oil hardened, tempered 600 °C (1110 °F) |
| 12.7 at 20-200 ℃ (68-392 °F) | ||
| 13.7 at 20-400 ℃ (68-752 °F) | ||
| 14.5 at 20-600 ℃ (68-1112 °F) | ||
| 11.2 at -100 to 20 °C (-148 to 68 °F) | Oil hardened, tempered 630 °C (1170 °F) | |
| 10.4 from -150 to 20 °C (-238 to 68 °F). | ||
| 12.4 at 20-200 ℃ (68-392 °F) | ||
| 13.6 at 20-400 ℃ (68-752 °F) | ||
| 14.3 at 20-600 ℃ (68-1112 °F) | ||
4340 steel mechanical properties are listed in the following tables.
| AISI 4340 Mechanical Properties | ||||||
| Steel | Condition | Tensile strength, MPa (ksi), ≥ | Yield strength, MPa (ksi), ≥ | Elongation in 50 mm (2 in.), ≥ | Reduction in area, %, ≥ | Hardness, HB, ≤ |
| 4340 | Normalized at 870 °C (1600 °F) | 1282 (186) | 862 (125) | 12.2 | 36.3 | 363 |
| Annealed at 810 °C (1490 °F) | 745 (108) | 470 (68) | 22.0 | 50.0 | 217 | |
| Oil quenched from 800 °C (1475 °F) and tempered at 540 °C (1000 °F) | 1207 (175) | 1145 (166) | 14.2 | 45.9 | 352 | |
Typical applications for this grade include:
Company can meet the following specifications for this grade:
supplies 4340 steel bar in a variety of sizes ranging from 1/2”-15”. The shapes available for this grade include: