AISI 1040: Forging Facts & Characteristics

Chemical Analysis
C Carbon
0.37 – 0.44
Mn Managanese
0.60 – 0.90 max
P Phosphorus
0.04 max
S Sulfur
0.050 max

C1040 is a medium carbon, medium tensile steel supplied as forged or normalized. This steel shows good strength, toughness and wear resistance.

C1040 is a medium-carbon engineering steel that is suitable for flame or induction hardening. It is a versatile forging material with mechanical properties that are appropriate for a full range of applications. The steel can be readily welded and machined providing correct procedures are followed.

Forging AISI 1040 Carbon Steel

C1040 is forged from 2100 – 2300 º F down to a temperature in the range 1600 – 1700 º F (1150*–1280 º C down to 870 – 925 º C.). The actual forging and finishing temperatures will depend on a number of factors, including overall reduction during forging and complexity of part being forged. Experience alone will determine near exact values for these two parameters. Parts are air cooled after forging.

Applications of AISI 1040

This grade of steel is used for forged parts where the strength and toughness of the material are appropriate. C1040 may be used for the manufacture of forged crankshafts and couplings, along with a range of parts where the properties of heat-treated C1040 are suited to the application.

Heat Treatment

Heat treatment is carried out on this grade to render it suitable for machining and to impart to it specified mechanical properties.


Full annealing of small C1040 forgings is carried out between 1450 and 1600 º F (840 – 890 º C) followed by furnace cooling at 50 º F (10 º C) per hour, to 1200 º F (650 º C) and air cooling.


The normalizing temperature range for this grade is typically 1550 – 1600 º F (840 – 870 º C,) Normalizing is followed by cooling in still air. When forgings are normalized before hardening and tempering or other heat treatment, the upper range of the normalizing temperature is used. When normalizing is the final treatment, the lower temperature range is used.


Hardening of this grade is carried out from an austenitizing temperature of 1510 – 1580 º F (820 – 860 º C) and oil or water quenching.

Flame and induction hardening may be carried out by heating quickly to the desired case depth and quenching in water or oil. This should be followed by a tempering treatment at 300 – 400 º F (150 – 200 º C) to reduce stresses in the case without affecting its hardness. A surface hardness of Rc 58 may be obtained by this treatment.


Tempering after normal hardening and oil or water quenching is carried out at 750 – 1260 º F (400 – 680 º C) to give the required mechanical properties as determined by practical experience.


Machinability of C1040 is good providing the full annealing cycle described above is used, ensuring a coarse lamellar pearlite to coarse spheroidite microstructure.


This grade is readily welded with the correct procedure. Welding in the through hardened or flame or induction hardened conditions is not recommended.

Low-hydrogen electrodes are recommended together with preheat at 300 – 500 º F (150 – 260 º C.) to be maintained during welding, Cool slowly and stress relieve where possible.

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