What is 4340 steel?
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.
AISI 4340 steel is a medium carbon, low alloy steel known for its toughness and strength in relatively large sections. AISI 4340 is also one kind of nickel chromium molybdenum steels. 4340 alloy steel is generally supplied hardened and tempered in the tensile range of 930 – 1080 Mpa. Pre hardened and tempered 4340 steels can be further surface hardened by flame or induction hardening and by nitriding. The 4340 steel has good shock and impact resistance as well as wear and abrasion resistance in the hardened condition. AISI 4340 steel properties offer good ductility in the annealed condition, allowing it to be bent or formed. Fusion and resistance welding is also possible with our 4340 alloy steel. ASTM 4340 material is often utilized where other alloy steels do not have the hardenability to give the strength required. For highly stressed parts it is excellent choice. AISI 4340 alloy steel can also be machined by all customary methods.
4340 Alloy Steel Datasheet
The following tables and lists give 4340 alloy steel datasheet and specification including chemical composition, physical properties and mechanical properties, heat treatment, welding, etc.
Chemical Composition
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 AISI 4340 Steel Properties
The tables below list AISI 4340 steel properties, including physical and mechanical properties.
Physical 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.
Due to availability the ASTM 4340 grade steel is often substituted with European based standards 817M40/EN24 and 1.6511/36CrNiMo4 or Japan based SNCM439 steel. You have the detailed data of 4340 steel below.
1. AISI Alloy 4340 Steel Supply Range
4340 Steel Round Bar: diameter 8mm – 3000mm (*Dia30-240mm in stock in annealed condition, immediate shipment)
4340 Steel Plate: thickness 10mm – 1500mm x width 200mm – 3000mm
4340 Steel Grade Square: 20mm – 500mm
Surface Finish: Black, Rough Machined, Turned or as per given requirements.
Welding of AISI 4340 Steel
AISI 4340 steel has good weldability. It can be easily gas or arc welded, but electrodes of the same composition should be used. Since 4340 alloy steel is air hardened, the welded parts should be either annealed or normalized and tempered shortly after welding.
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