Tutorial: Modulus of elasticity of steel – Materials science

Basic knowledge

Steel is an important material in modern industry and is used for a variety of applications. A crucial property to consider when using steels is their elasticity. The modulus of elasticity or Young’s modulus indicates how much stress is needed to achieve a certain degree of elongation. In this article we will look at the different types of steels and their respective elastic moduli.

What is steel?

Steel consists mainly of iron (Fe) and carbon (C), but other elements can also be added to improve or adapt its properties.

Most commercially available grades have a carbon content between 0.2% and 2%. The exact composition varies depending on the manufacturer and intended use of the material.

Today, thanks to modern technologies and research results, steel grades can be produced that have an impressive combination of properties. These properties are the result of targeted addition of alloy elements such as chromium, molybdenum or nickel in certain proportions.

The accompanying elements in steel also play an important role in determining its physical and chemical properties. Carbon, for example, increases the hardness of the material, while sulphur makes it brittle.
In addition, the crystal structure of the steel after deformation and its heat treatment condition are also decisive for its final mechanical and thermodynamic properties. Controlled cooling or heating processes can achieve a desired condition.

What grades of steel are there?

There is a wide range of different grades of steel, which are manufactured for different purposes. Some of the most common types are carbon steel, alloy steel and stainless steel.

Carbon steels have a high carbon content and are often used for construction elements such as beams or bridges. They can also be used in machine tools because they are hard enough to perform cuts. Due to their high strength and hardness, carbon steels are a popular material in special machine construction. They are particularly suitable for components that are subject to high loads, such as gear wheels or shafts.

In addition to iron, alloy steels also contain other elements such as chrome or molybdenum. These additives improve the strength of the material and its corrosion resistance to water or humidity. In special machine construction, alloy steels are used, for example, in the production of machine tool parts. In the production of special equipment for mining and tunnel construction as well as in the construction of cranes, alloy steels are also often used.

Rust-free (stainless) steels are characterised by their high resistance to rust - hence their name "rust-free". This makes it ideal for use outdoors and in environments with moisture exposure such as kitchen utensils or medical equipment. Rust-free steels and stainless steels are indispensable in special machine construction. They offer high corrosion resistance, which is especially beneficial in wet or aggressive environments.

In addition to these three main types, many other specialised steel grades are available on the market: High-temperature steels, for example, are used in extremely hot conditions; electrical steels, in turn, enable higher energy efficiency in electrical transformers; spring steels are used primarily in the construction of springs.

What is the modulus of elasticity for steel?

The elasticity modulus (e-modulus, tensile modulus) of a material describes the elastic behaviour of the material. It indicates how much tension is needed to achieve a certain elongation.

The elasticity modulus of steel varies depending on the type and composition of the material. In general, alloy steels have a higher e-modulus than non-alloy steels.

The dimension of the modulus of elasticity is the mechanical tension; E is common as the formula character. Pascal (Pa) or Newton per square metre (N/m²) is used as the unit.

How is the modulus of elasticity determined for steel?

The elasticity modulus for steel is determined experimentally by means of a tensile test.

The tensile test (DIN EN ISO 6892-1) is a standardised procedure that serves to determine the mechanical properties of materials. These can vary greatly depending on the area of application and range from the determination of the elongation limit and tensile strength to elongation at break or other important characteristic values.

Standardised samples with a defined cross-sectional area are elongated to breakage point. During the test, the elongation or distance is increased evenly and without impact, while maintaining a low speed.

The measured values are entered in the stress-strain diagram - the measured strain in the X-axis and the tensile stress in the Y-axis.

When elongated, the material undergoes the following phases:

(1) - Elastic elongation, with straight lines by Hooke’s law
(2) - Flow zone
(3) - Solidification
(4) - Constriction
(5) - Breakage

The modulus of elasticity is defined by the linear range in the stress-strain diagram.

With uniaxial load in the tensile test, this linear range can be easily recognised: The higher the applied tensile force, the more the material expands - but always proportional to the force. The slope of this linear-elastic region then results in the modulus of elasticity of the material.

From this derivation, Hooke's Law applies with:

E - Modulus of elasticity
σ - Tensile stress
ε - Strain

E-modulus of different steel types

It is important to note that the e-modulus not only depends on the chemical composition of the material, but is also influenced by the manufacturing process and the mechanical properties such as hardness or strength.

The higher the e-modulus of a particular grade of steel, the more robust the constructions made with it under load influences.

Elastizitätsmodul (E-Modul) für typische Metallmaterialien.
Material	[N/mm²]
Baustahl (z.B. SS400 / EN 1.0038 Equiv.)	ca. 210 x 10³
Maschinenbaustahl (S50C / EN 1.1206 Equiv.)	ca. 210 x 10³
Vorgehärteter Stahl (SCM440 / EN 1.7225 Equiv.)	ca. 203 x 10³
Werkzeugstahl (SKD11 / EN 1.2379 Equiv.)	ca. 210 x 10³
Messing	ca. 63 x 10³
Kupfer	ca. 105 x 10³
Aluminium (Reinaluminium)	ca. 68 x 10³
Aluminiumlegierung (7xxx) "Duraluminium"	ca. 73 x 10³

Properties of plastics – Which plastics are suited for mechanical engineering?

Technical plastics are an indispensable part of modern industry. In custom machine construction in particular, they find a wide range of applications because they have a high degree of flexibility and formability. It is important to know what properties plastics must have in components and standard parts in custom machine construction. This article describes the most important applications for plastics in mechanical engineering.

Basic knowledge

4 Minutes read

Milled parts as freely configurable components through Make-to-Order – Flexibility in contract manufacturing

Make-to-Order (MTO) is the classic production process for customised production. Make-to-Order means contract manufacturing. In this process, production takes place according to individual customer requirements and only begins after the customer has placed an order. Unlike Make-to-Stock (MTS), where production and stock levels are pre-determined, MTO components are only manufactured after receipt of a customer order.

Basic knowledge Construction

7 Minutes read

Intrinsic Vibration Behavior of Springs

In mechanical engineering, tension and compression springs are an important part of the design of mechanical systems, applications and uses. The properties of springs, such as their return force and spring constant, influence the performance and functionality of machines. In order to understand these properties and the vibration behavior of spring systems, we look in this article at the physical relationships between spring systems and the relationship between the natural frequency and resonance.

Basic knowledge Damping

7 Minutes read

Turned parts – Precisely configurable Make-to-Order (MTO) components

Make-to-Order (MTO) turned parts and components are an important part of the modern manufacturing industry. Make-to-Order means contract manufacturing. This means that production only begins when a specific order is available. In contrast to Make-To-Stock (MTS), where products are produced for stock, MTO components are only manufactured after order receipt.