Engineering steel grades explained

The grades of engineering steel are as diverse as the industries and projects they are used in. Choosing the wrong steel can spell disaster… and we don’t want that to happen!

The steel grades act as common guidelines that set out the composition, mechanical properties, tolerances on dimension, manufacture method and quality control provisions that are specific to each material.

At Edcon, we’re proud to provide a huge range of engineering steel, all of which can be found on our website.

Here, we outline the differences between engineering grades of steel and their best applications.

Choosing the right engineering steel grade

Working with the best engineering steel grade shouldn’t be treated as an afterthought.

Choosing the right grade requires a thoughtful approach and it’s vital to understand some key factors before making your final decision.

Some of the most common considerations for choosing the best engineering steel grade include:

Formability

One of the most important factors to consider is if the engineering steel has good formability. Some elements, such as chromium and boron, increase the steel’s hardenability.

Since most engineering steels are able to be hardened, forming is typically done in the annealed state of the material.

Engineering steels that are annealed and have lower amounts of alloys and carbon are typically more formable than those with higher amounts of carbon and other alloying elements.

Welding

If you’re using engineering steel for welding, there are also some unique factors to consider. Some of the elements added to engineering steels can be detrimental to welding. Be wary of additions of sulfur and boron if you plan to weld, as both can induce cracking.

Also, if the carbon content of the steel is high, care must be taken pre-heat the material and to slow the rate of cooling to avoid cracking.

Corrosion resistance

If corrosion needs to be inhibited (and coating is not an option) then it is important to find a grade that has increased corrosion resistance. Engineering steel grades with a higher amount of elements such as chromium, copper, nickel and molybdenum will generally have a greater resistance to corrosion.

Bright Mild Steel 1020

Bright Mild Steel (1020) is a carbon steel alloy which has the surface condition improved by drawing, peeling or grinding over the hot rolled finish supplied by the steel mill. Bright mild steel has low hardenability properties, is a low tensile carbon steel and is normally used in a turned, polished or cold drawn condition.

Due to its low carbon content, 1020 will not respond satisfactorily to flame or induction hardening, nor to nitriding, due to a lack of suitable alloying elements.

This makes bright mild steel a good choice for improved machining and improved dimensional tolerances and straightness. Bright mild is also suitable for mechanical and allied engineering applications that will not be heavily stressed, making it ideal for welding applications, studs, bolts, shafts, threaded bars, spindles, axles and machinery parts.

Free Machining 1214

Free Machining (1214) steel is a resulfurised carbon steel bright bar, characterised by low tensile and low hardenability, generally supplied in the cold drawn or turned and polished condition. It’s well known for its excellent machinability, reasonable strength and ductility.

Due to its very low hardenability, 1214 is generally used in the supplied condition. But it will not respond satisfactorily to flame or induction hardening due to its low carbon content, and it’s also not effective at nitriding, due to a lack of suitable alloying elements.

1214 also has a higher sulphur content, which can cause hot shortness and porosity during welding. For this reason, welding should be avoided.

Medium Tensile 1045

1045 steel is a medium tensile, low hardenability carbon steel. Medium tensile steel is characterised by its good weldability, machinability and high strength and impact properties in either the normalised or hot rolled condition.

Medium tensile steel has a low through-hardening capability with only sections of around 60mm in size, making it suitable for tempering and through-hardening. It can also be efficiently flame or induction hardened in the normalised or hot rolled condition to obtain surface hardnesses in the range of Rc 54 – Rc 60 based on factors such as section size, type of set up and quenching medium used.

However, 1045 steel lacks suitable alloying elements and so it does not respond to the nitriding process.

High Tensile 4140, 4340, EN26

High tensile 4140 steel is the most commonly used of the high tensile steels, with a wide range of applications in automotive, gear and engine construction, crankshafts, steering knuckles, connecting rods, spindles, intermediate gears, pump and gear shafts, axles, nuts and bolts.

4140 is a low alloy steel containing chromium, molybdenum and manganese. It’s an excellent material choice due to its toughness, high fatigue strength and abrasion and impact resistance. Not many grades can match the versatility and usefulness of 4140.

The addition of chromium and molybdenum promotes corrosion resistance. The molybdenum can be particularly useful when trying to resist corrosion due to chlorides. The manganese in 4140 steel is used to increase hardenability and as a deoxidiser. In alloy steels, manganese can also combine with sulfur to improve machinability and make the carburising process more effective.