AISI 4140 is a chromium molybdenum alloy steel specification widely used in the oil and gas industry. Similar to grade AISI 4130 but with a slightly higher carbon content. The higher carbon content of AISI 4140 gives greater strength and heat treatment capabilities in comparison to AISI 4130.

AISI 4140 is commonly used for a variety of applications in the oil and gas sector. Typical applications include components such as connection rods, collets, conveyor pins, gears, stem assemblies, pump shafts and tool holders.

Preheat the steel carefully, then raise the temperature to 1150-1200°C for forging. Do not forge below 850°C.

Heat the AISI 4140 slowly to 800-850°C and allow enough time for the steel to be thoroughly heated. Cool slowly in the furnace to 480°C followed by air cooling.

AISI 4140 steel is usually supplied ready heat treated to 18-22HRC. If further heat treatment is required annealed AISI 4140 should be heated slowly to 840-875°C and after adequate soaking at this temperature quench in oil. Temper as soon as the tools reach room temperature.

Heat the AISI 4140 carefully to a suitable temperature selected by reference to a tempering chart or table (usually between 550-700°C, soak at the temperature for 2 hours per 25mm of ruling section, then allow to cool in air. Tempering between 250-375°C is not advised as tempering within this range will seriously reduce the impact value.

Chemical Composition

Steel Grades C Mn Si P S Ni Cr Mo
AISI 4140 0.38-0.43%
0.75-1.00%
0.10-0.35%
0.035% max
0.040% max
0.25% max
0.80-1.10%
0.15-0.25%

Mechanical Properties

Steel Grades
Tensile KSI
0.2% Proof Stress KSI
Elongation %
Reduction of Area %
Hardness HRc
Hardness Brinell

AISI 4140
100-130 80-110 min 20 min 40 18-22 217-235