Selecting the Correct Steel

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Selecting the Right Steel

The current standards for engineering steels contain several hundred specifications. This presents a wide and sometimes confusing choice to the designer or steel specifier. The harmonization of European Steel Standards has led to the introduction of a further range of steels which, until such time as they have fully replaced national standards, may add to the problem.

In practice, a relatively narrow range of specifications is in general use for the majority of mechanical engineering applications. Impact Ireland (Metals N.I.) Ltd stock range, which is based on a demand pattern built up over many years, includes most of these steels, full details of which are contained within the product details on this site.

To assist users in the selection of steel, the main product groups are shown below together with a selection of the relevant BS 970 specifications. Where applicable, details are also given of the harmonized European and American SAE/AISI steels. A comment is also made on the characteristics of the steel and typical application to which they may be applied. Engineering steel bars are available bright drawn, turned or ground and black hot-rolled, the choice depending on the size and type of component, machining operation, surface finish, production run or other considerations.

Low Carbon Freecutting Steels

The most popular type of steel for the production of turned parts and lightly stressed components. Commonly used where machinability, surface finish and output are important factors.

European Standard BS EN 10277-3, the principal BS 970 specification is 230M07 either leaded or unleaded. Steel name 11SMn30 and 11SMnPb30. American AISI/SAE 1213. 12L14.

Low Carbon Steels

A group that includes the generic term mild steels. Used for many lightly stressed components and depending on the condition and form of supply, for welding, bending, forming and engineering applications.

European Standard EN 10083-1, the principal BS 970 specification is BS970: 040A10, 045M10, 080A15, 070M20, American AISI/SAE 1010, 1016, 1020.

Carbon and Carbon Manganese Case-Hardening Steels

Chosen for applications where it is necessary for the components to have a hard wear-resisting surface with a tough supporting core, but tensile strength is not specified. After machining it is necessary to carburize and harden the parts when figures of 59/62 HRC are attainable.

Typical specifications – European Standard EN 10084, BS 970: 045A10, 045M10, 080M15, 210M15, 214M15, European Standard C15E, C16E, 10S20, 15S14, American AISI/SAE 1010, 1016, 1117, 1118.

Medium Carbon & Carbon Manganese Steels

Offering greater strength than mild steels they respond to heat treatment and include types suitable for induction and flame hardening. Depending on the analysis and ruling section, a tensile strength in the range 850-1000 N/mm2 may be attained although 700-850 N/mm2 is more common. Free cutting grades are available. Applications include gears, racks, pinions shafts, rollers, bolts, studs, nuts etc.

Specifications include- European Standard EN 10083-1, BS970: 080M30, 080M40, 080A42, 080M50, 070M55, 150M36, c40e, c45e, c50e, c35e, 28mN6,American AISI/SAE 1030, 1040, 1042, 1335.

Alloy Case-Hardening Steels

As in the case of carbon case-hardening steels, alloy grades are specified when a hard wear-resisting surface is required. As a result of the alloying elements, superior mechanical properties are achieved after heat treatment. The choice of steel will depend on the ruling section and the properties required for the component. Typical applications include gears, cams, rollers, transmission components and other highly stressed parts.

Specifications include – European Standard EN 10084, BS970: 635m15, 655m13, 665m17, 805m20, 832m13. 16MnCr5, 16NiCr4, 15NiCr13, 20NiCrMo2-2.American AISI/SAE 3415, 4615, 8620.

Alloy Direct Hardening Steels

Steels in this group contain two or more of the alloying element nickel, chromium, molybdenum, vanadium. Bars can be supplied in the softened condition where, after machining the components can be hardened and tempered to the required mechanical properties or supplied in the finally heat-treated condition where the components can be put into service without further heat treatment. Direct hardening alloy steels are used for applications where high strength and resistance to shock is an important requirement. For increased surface hardness many of the specifications are suitable for surface hardening.

Typical specifications – European Standard EN 10083-1 BS 970: 605M36, 708M40, 817M40, 826M40. 41Cr4, 42CrMo4, 34CrNiMo6. American AISI/SAE: 4140, 4340.

Stainless Steels

There are three main types of stainless steel: Martensitic – Ferritic – Austenitic.

Free cutting grades of Martensitic and Austenitic are available which offer considerable machining advantages, particularly for the production of repetition turned parts. Either selenium or sulphur is normally used as the free cutting additive.

Martensitic stainless steels can be hardened and tempered to give tensile strength in the range 550-1000N/mm2. Typical applications include fasteners, valves, shafts, spindles, cutlery, and surgical instruments.

Specifications include- European Standard EN 10088-3 BS 970: 410S21, 420S29, 420S45, 431S29.
Freecutting grades 416S21, 416S41, 416S37, 441S49.

Ferritic stainless steels are more common in strip and sheet form where applications include domestic and automotive trim, food processing and catering equipment, exhaust systems etc. They have good ductility and are easily formed.

Typical specifications BS 970: 403S17, 430S17.

Austenitic stainless steels cover a wide range of specifications. Austenitic grades offer the highest resistance to corrosion and are used for components in the food, chemical, oil & gas, medical, surgical, pharmaceutical as well as domestic and general. Austenitic grades are non-magnetic and cannot be hardened and tempered in the normal manner but do work harden.

Specifications include – European Standard EN 10088-3, BS 971: 302S31, 304S15, 316S11, 316S31, 320S31, 321S31, Freecutting grades include 303S31, 325S31, 303S42, 326S36.