EN8 Mild Steel

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The term Mild Steel applies to all low carbon Steel that does not contain any alloying elements in its makeup and has a carbon content that does not exceed 0.25%. The term “Mild” is used to cover a wide range of specifications and forms for a variety of Steel.

Mild Steel is used in mechanical engineering applications for parts that will not be subject to high stress.

When in its bright cold drawn condition the steel is able to endure higher levels of stress, particularly on smaller diameters.

Compared to normal Mild Steel, bright Mild Steel provides tighter sectional tolerances, increased straightness, and a much cleaner surface. The main advantage of cold drawn Steel is that Steel can be brought closer to the finished machine size, reducing machining costs. Another benefit of bright Steel bars is a marked increase in physical strength over hot rolled bars of the same section.

EN8: unalloyed medium carbon Steel (BS 970 080m40) has high strength levels compared to normal bright mild steel, due to thermo-mechanical rolling. EN8 is suitable for all round engineering purposes that may require a steel of greater strength.

Heat Treatment 

EN8 or 080m40 can be tempered at a heat of between 550 °C to 660 °C (1022 °F-1220 °F), heating for about 1 hour for every inch of thickness, then cool in oil or water.

Normalising of EN8 bright Mild Steel takes place at 830-860 °C (1526 °F-1580 °F) then it is cooled in air.

Quenching in oil or water after heating to this temperature will harden the steel. 

Chemical Composition of EN8 Steel

  C Mn Si P S Cr Mo Ni N
Min 0.35 0.60 0.05 0.015 0.015        
Max 0.45 1.00 0.35 0.06 0.6        

Welding En8 steel

Modern EN8 bright Mild Steel contains a lot less carbon than it used to, this means that it is possible to weld pieces up to 18 mm thick without preheating using MIG wire (SG2) or a 7018 electrode.

Over 18 mm would require a pre-heat of 100 °C (212 °F) in order to prevent cracking.

Anneal afterwards is recommended to prevent breaking.

Mechanical Properties of EN8 Steel

Condition Yield Stress

x 106 Pa

Tensile Stress MPa Elongation %
Normalised 280 550 16
Cold drawn (thin) 530 660 7