AISI 1020 Low-(Mild)-Carbon Steel

Introduction [i]

AISI 1020 is a general purpose low tensile low hardenability carbon steel generally supplied in the cold drawn or turned and polished condition, with a typical tensile strength range 410 – 790 Mpa, and Brinell hardness range 119 – 235.

Characterised by excellent weldability, very good machinability with reasonable strength and very good ductility.

AISI 1020 due to its very low hardenability will through harden only in very small sections to relatively moderate strength levels, and is therefore generally used in the cold drawn or turned and polished condition. It can however be carburised achieving case hardnesses over Rc 65 with smaller sections, reducing as section size increases. Core strength will remain as supplied for all sections. Alternatively it can be carbonnitrided offering some advantages over standard carburising.

It will not respond satisfactorily to flame or induction hardening due to its low carbon content, nor to nitriding due to a lack of suitable alloying elements.

1020 is used extensively by all industry sectors for applications requiring good machinability or excellent weldability when high strength is not required plus lightly stressed carburised parts. It is also often used un-machined as supplied, its bright cold drawn or turned and polished finish being acceptable for many applications.

Typical applications are: Axles, General Engineering Parts and Components, Machinery Parts, Shafts etc. or Carburised: Camshafts, Light Duty Gears, Gudgon Pins, Ratchets, Spindles, Worm Gears etc.

Chemical Composition [ii]

Chemical Composition
  Min. % Max. %
Carbon 0.15 0.25
Silicon 0 0.35
Manganese 0.30 0.90
Phosphorous 0 0.05
Sulphur 0 0.05
Typical Mechanical Properties – Cold Drawn and Turned and Polished Condition
Cold Drawn Size mm   up to 16mm 17 – 38mm 39 – 63mm Turned & Polished (All Sizes)
Tensile Strength Mpa Min 480 460 430 410
Max 790 710 660 560
Yield Strength Mpa Min 380 370 340 230
Max 610 570 480 330
Elongation in 50mm % Min 10 12 13 22
Hardness HB Min 142 135 120 119
Max 235 210 195 170


Heat to 1100 oC – 1200 oC maximum, hold until temperature is uniform throughout the section and commence forging. Do not forge below 900 oC Finished forgings may be air cooled. 

[ii] Heat Treatment Data


Heat to 870 oC – 910 oC hold until temperature is uniform throughout the section, and cool in furnace.


Pack, salt or gas carburise at 880 oC – 920 oC, holding for sufficient time to develop the required case depth and carbon content, followed by a suitable refining/hardening and tempering cycle to optimise case and core properties.

Core Refine

Slow cool from Carburising temperature and re-heat to 870 oC – 900 oC, hold until temperature is uniform throughout the section and quench as required in oil, water or brine.

Case Hardening

Following core refining, re-heat to 760 oC – 780 oC, hold until temperature is uniform throughout the section and quench in water.

Temper immediately while still hand warm.

Tempering – After Carburising, Core Refining and Case Hardening

Re-heat to 150 oC – 200 oC, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm of section and cool in still air. NB. Tempering will improve the toughness of the case with only slight reduction in case hardness. It will also reduce the susceptibility to grinding cracks.


Heat to 890 oC – 940 oC hold until temperature is uniform throughout the section, soak for 10 – 15 minutes and cool in still air.

Stress Relieving

Heat to 650 oC – 700 oC hold until temperature is uniform throughout the section, soak for 1 hour per 25mm of section, and cool in still air.

Notes on Heat Treatment

Heating temperatures, rate of heating, cooling and soaking times will vary due to factors such as work piece size/shape, also furnace type employed, quenching medium and work piece transfer facilities etc.

Please consult your heat treater for best results.


1020 in the bright cold drawn or turned and polished as supplied condition has very good machinability and all operations such as turning, drilling, tapping, milling etc. can be carried out satisfactorily as per machine manufacturer’s recommendations for suitable tool type, feeds and speeds.


1020 has excellent weldability in the cold drawn or turned and polished as supplied condition, and can be readily welded by any of the standard welding processes.

NB. Welding in the carburised or heat treated condition is not recommended.

Welding Procedure

Low carbon electrodes are recommended.

Please consult your welding consumables supplier for suitable electrodes etc.

A pre-heat or post-heat is not generally required, however pre-heating larger sections can be beneficial as can a post-weld stress relieve if this is possible.

HddJetNozzle/Cherrington LLC (HDDJN/CLLC) believes the information provided is accurate and reliable. However no warranty of accuracy, completeness or reliability is given, nor will any responsibility be taken for errors or omissions.

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Chemical Composition(s) for materials used to manufacture the parts referenced in this website and/or by the Seller can be obtained by the Buyer requesting from the Seller a (lot specific) “Material Test Report”.