What is AISI 4140 Steel?

AISI 4140 alloy steel round bar sheet plate belongs to medium hardenability steel.AISI 4140 steel has high fatigue strength and low notch sensitivity. Low-temperature impact toughness is also very high, no obvious temper brittleness. AISI 4140 steel round bar is mainly used after quenching and tempering state. it is used to manufacture high-strength parts under impact loads and the fittings with large cross-sections and other stressed members. Such as the horizontal eccentric shaft of the horizontal forging machine, the crankshaft of the forging press, and etc.
Its equivalent grade is JIS SCM440 and DIN 1.7225. The properties and composition of 4140 steel round bar sheet plate as below.

ASTM 4140 Steel Application

4140 steel is medium hardenability steel with good strength and good comprehensive mechanical properties after heat treatment. It has good manufacturability. The maximum temperature of use is 427 °C. It can be used to make turbine fastener, tool bodies, forming dies, brake dies and etc. And it also as the material of Oil deep well drill pipe joints and fishing tools below 2000m.

4140 Steel Round Bar Sheet Plate Heat Treatment

Machinability
At the annealed condition, 1.7225 alloy tool steel has good machinability.

Forming
DIN 1.7225 steel has high ductility. It can be formed using conventional techniques in the annealed condition. It is required more pressure or force for forming because it is tougher than plain carbon steels.

Welding
1.7225 alloy steel can be welded using all advanced techniques. But, the mechanical properties of it will be affected if it is welded in the heat treated condition, and post weld heat treatment should be performed.

Heat Treatment
1.7225 tool steel is heated at 845°C(1550°F) followed by quenching in oil. Before hardening, it can be normalized by heating at 913°C (1675°F) for a long period of time followed by air cooling.

Forging
It is forged at 926 to 1205°C(1700 to 2200°F)

Hot Working
4140 steel can be hot worked at 816 to 1038°C(1500 to 1900°F)

Cold Working
1.7225 steel can be cold worked using conventional methods in the annealed condition.

Annealing
Heat it to 800℃ – 850℃, hold until temperature is uniform throughout the section and cool in furnace.

Normalizing
Heat 1.7225 alloy steel to 870℃ – 900℃, hold it until the temperature is uniform throughout the section, soak for 10 – 15 minutes and cool in still air.

Tempering
DIN 1.7225 steel can be tempered at 205 to 649°C (400 to 1200°F) depending upon the desired hardness level. The hardness of the steel can be increased if it has lower tempering temperature. For example, tensile strength of 225 ksi cab be achieved by tempering at 316°C (600°F), and tensile strength of 130 ksi can be achieved by tempering at 538°C (1000°F).

Hardening
DIN 1.7225 alloy steel can be hardened by cold working, or heating and quenching.

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