Low-Carbon Steel 1018

General Characteristics of Low-Carbon Steel 1018

C1018 is a general purpose carbon steel that is easily machined and welded and may be hardened by carburizing and by other surface-hardening methods.

Chemical Analysis
C Carbon
Mn Manganese
0.60/0.90 max
P Phosphorus
0.040 max
S Sulfur
0.050 max


This grade of steel is used for forged motor shafts, hydraulic shafts and pump shafts, as well as machinery parts. It would be used for such applications in a surface-hardened condition.


C1018 is forged from around 2300ºF down to a temperature in the region of 1650ºF
(1260ºC down to 900ºC.). 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.

Heat treatment

A significant amount of this grade of steel is used in the as- forged condition, since its machinability in this condition has been found to be better than that in the normalized condition.
Little is to be gained, at this carbon level, by a quenching treatment.

At this carbon level, annealing after forging may not be necessary, and depending upon the hardness after forging and the complexity of the part being forged, machining may be carried out on the as-forged parts. If parts are of complex shape and hence there are structural variations throughout the part, then normalizing is in order.


Normalizing is seldom carried out on carbon contents at this level, but may be used prior to surface hardening. The normalizing temperature range for this grade is typically 1650-1700ºF (900 – 925ºC.) followed by air cooling.


This grade of steel is not normally subjected to hardening and tempering treatments as the hardness obtained from such treatments would not warrant their being performed. Carburizing might be carried out at 1620-1690ºF (880-920ºC,) and carbonitriding at 1470 -1600ºF (800-875ºC.)

Hardening of the carburized case would be performed at 1430-1500ºF (780-820ºC) followed by a water quench and a tempering treatment at 300-400ºF (150-200ºC) to improve case toughness with a minimum effect on its hardness. Case hardness values of Rc 58 may be obtained on carburized C1018.


This grade of steel may be welded by all normal methods: low-carbon electrodes are recommended.

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