1018 / A36 Steel

AISI 1018/ ASTM A36 belong to the family of low carbon steels (also called mild steels), the most commonly available grades in the world. This steel family has good strength, weldability, ductility, surface hardening quality, good mechanical properties and a very good machinability. 1018 and A36 are usually both not used for high performance applications and therefore can be combined or substituted easily. The raw material for 1018 is often produced cold-rolled, while A36 is often produced hot-rolled.

Cold drawing increases tensile and yield strength, torsional strength, surface hardness and wear resistance as well as better tolerances and improved smoothness compared to hot-finished steel.

Hot rolled it has good toughness, strength, ductility, formability, weldability and workability. In its annealed condition 1018/A36 can be easily formed.

Applications

Applications for these steel grades include: tool holders, spindles, sprockets, gears, jigs and fixtures.

Heat treatment

This steel grade is most often used in the as-forged condition, as machinability in this condition is better than in the normalized condition.

Hardening

Hardening can be done by any standard carburizing methods, followed by a heat treatment.

Quenching

1018/A36 is an unalloyed low-carbon steel with only 0.18% carbon content. It is difficult to quench, and is not usually used immediately after quenching.

Normalizing

Only occasionally used on 1018/A36, it may be normalized prior to surface hardening. For this, heat the work piece at 1634-1724°F (890-940°C) and then cool it in still air.

Tempering

To reduce grinding cracks or improve case toughness, temper the steel at 302-392°F (150-200°C), this process has little or no effect on the hardness of the work piece.

Annealing

Heat the material at 1598-1670°F (870-910°C) and then furnace cool.

Stress relieving

Heat to 932-1292°F (500-700°C), then cool the work piece in still air.

Case hardening

Heating the material should be carried out between 1436-1503°F (780-820°C), then it should be quenched in water.

Core refining

This  process is optional, heat 1018/A36 at 1436-1508°F (780-820°C) and moistened in oil or water.

Carburizing

Heat the material at 1616-1680°F (880-920°C) for about 8 hours, then furnace cool. Carburized steel offers a high surface hardness (up to 572 BHN (56 HRC)) and a soft core (lower than 277 BHN (30 HRC)) to the work pieces. It is used to improve drilling, machining, threading and punching processes and to prevent cracking in severe bends.

Carbonitriding

The temperature for carbonitriding is 1450-1650°F (790-900°C) followed by cooling the work piece in oil.

Hot working

This alloy has good hot forming characteristics and can easily be hot worked.

Cold working

In its annealed condition, the microstructure of this alloy consists of ferrite and a small amount pearlite, its strength and hardness are low, its plasticity and toughness are better. As a result, its cold formability is good and it can be cold-formed into shape by cold drawing, stamping, bending and crimping for example. To overcome the tendency to work hardening, intermediate annealing is required.

Machinability

Machining gives 1018/A36 low carbon steel a great finish, continuous and hard chips and it can be machined in all conditions.

Welding

Welding 1018/A36 can be done by most conventional practices, e.g. resistance, submerge melt, oxyacetylene and gas welding. It is not recommended to weld the material after carburizing or carbonitriding. Post- and pre-heating is not necessary; though pre-heating can be done for sections over 1³¹/₃₂ inches (50 mm) and post-heating can be stress-relieving.

Forging

Heat at 2102-2336°F (1150-1280°C) and hold until the temperature becomes constant. Then cool in air. Do not forge under 1652°F (900°C).