4340 steel is one of the most widely used materials in the industry. It belongs to alloy steel, due to it has alloy element in it. Adding alloy element to change the properties of it to make it satisfy the needs of industry requirement.
4340 Steel Properties
Because of the certain alloy elements be added, it has high strength and toughness. And has great hardenability and temper brittleness. But the weldability is bad. It needs a high temperature to preheating before welding. And after welding, must eliminate stress, could be used after quenching and tempering.4340 Steel Application
It is a good material for the important fittings with high strength and good plasticity. And it could be used to manufacture important parts with special functional requirements after nitriding treatment. Such as shafts, gears, fasteners and etc.And used as important tempering fittings which requiring good toughness, high strength with big size. For example:
heavy machinery high-load shafts
The dia is bigger than 250mm of turbine shafts
rotor shafts for helicopters
turbine shafts for turbine jet engines, blades, high load transmissions
crankshaft fasteners
It also can be as high strength steel to use after low-temperature tempering or after isothermal quenching.
4340 Steel Composition
C: 0.37%-0.44%
Si: 0.17%-0.37%
Mn: 0.50%-0.80%
Cr: 0.60%-0.90%
Mo: 0.15%-0.25%
W: 0.50%-0.80%
S: 0.030%
Ni: 1.25%-1.65%
The intensity of Tension: ≤980MPa
Yield Strength: ≤835MPa
Percentage Elongation: ≤12%
Reduction of Cross-sectional Area: ≤55%
Notched Bar Impact Strength: ≤98 J/cm²
4340 Steel Heat Treatment Processing
Hammered
Normalizing
Annealing
Rough Machining
Austenitizing
Finish Machining
Nitriding (optional)
