4340 Steel Round Bar | EN24 Steel Round Bar | 34CrNiMo6 Steel Round Bar
4340 steel is an ultra-high strength steel classified a medium-carbon, low-alloy steel. 4340 steel has high strength, ductility, toughness, creep resistance, and fatigue resistance relative to most other steels. Hardness ranging from 24 to 53 HRC can be achieved, depending on the heat treatment.
Designation by Standards
Chemical Composition (%)
Mechanical Properties
Typical Mechanical Properties - Hot Rolled Condition
Heat Treatment
ASTM 4140 alloy steel is heated at 842°C followed by quenching in oil. Before hardening, it can be normalized by heating it at 914°C for a long period of time, followed by air cooling.
Forging
ASTM 4140 alloy steel is forged at 925 to 1205°C
Hot Working
ASTM 4140 alloy steel can be hot worked at 818 to 1037°C
Cold Working
ASTM 4140 alloy steel can be cold worked using conventional methods in the annealed condition.
Annealing
ASTM 4140 alloy steel is annealed at 871°C followed by slowly cooling in the furnace.
Tempering
ASTM 4140 alloy steel can be tempered at 205 to 650°C depending upon the desired hardness level. The hardness of the steel can be increased if it has a lower tempering temperature. For example, a tensile strength of 225 ksi can be achieved by tempering at 317°C, and tensile strength of 130 ksi can be achieved by tempering at 539°C.
Hardening
ASTM 4140 alloy steel can be hardened by cold working, or heating and quenching.