4130 Chromoly Steel Specs

Written by alan edwards
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4130 Chromoly Steel Specs
4130 chromoly steel is used to a great extent in the racing industry. (formule 1 de 1981 image by cachou34 from Fotolia.com)

Steel comes in many forms and formulas. The steel formula (what alloys are in it) determines what that particular steel is best used for. 4130 chromoly steel is used to a great extent in the aviation and racing industries due to its ease of fabrication and weldability. 4130 is an excellent choice when strong but lightweight steel tubing is needed.

Chemistry Data for 4130 Chromoly Steel

The specification of 4130 chromoly steel is like a recipe. The difference is, if properly made, the recipe for steel will meet the standard of AISI. AISI is the acronym for the American Iron and Steel Institute. AISI sets standards for the content of alloyed iron that becomes steel. The base metal for AISI 4130 chromoly steel is iron. Under the standard, carbon may make up 0.28 to 0.33 per cent of the finished material. Chromium quantities range from 0.8 to 1.1 per cent and manganese ranges from 0.7 to 0.9 per cent of the product contents. Molybdenum ranges from 0.15 to 0.25 per cent of the finished product. Phosphorus content may not exceed 0.035 per cent. Silicon limits are 0.15 to 0.35 per cent and sulphur is allowable to a maximum of 0.04 per cent. Iron makes up the balance of the product.

AISI 4130 Physical Data

When alloyed, AISI 4130 steel has to meet the following standards; density (lb/cu.in.) of 0.238, specific gravity 7.8, specific heat (Btu/lb/Deg F - [32-212 Deg F]) of 0.114, melting point (Deg. F) 2610, thermal conductivity 22.3, mean co-efficient thermal expansion 7 and modulus elasticity tension of 29.

Principal Design Features

AISI 4130 with a carbon content that is nominally 0.30 per cent is a low alloy steel that has the strengthening agents molybdenum and chromium. Due to its relatively low carbon content this alloy is excellent for fusion welding. The alloy, if subject to heat treatment can be hardened.


After hardening there is a loss of ductility (the ability of being hammered out thin or drawn out into wires). To restore some of the lost ductility alloy 4130 is tempered at between 750F and 1050F. The lower the tempering temperature, the greater the alloy's strength.

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