Tensile test of steel – insight into the mechanical properties

The tensile test is one of the most important methods for determining the mechanical properties of steel. It provides essential characteristic values that are of great importance for the selection and processing of steel products.

Procedure of the tensile test

In the tensile test, a standardized test rod is subjected to a uniaxial tensile load in stages until it fails. During the test, the applied force and the resulting elongation are continuously recorded. Various mechanical properties can be derived from this.

There are different specimen shapes for the tensile test:

• Flat tensile test: Used for sheet metal and flat products.
• Round tensile test: Used for rods, tubes and other rotationally symmetrical components.

A key result of the tensile test is the stress-strain curve, which graphically represents the mechanical behavior of the material. It shows the elastic and plastic deformation up to fracture and helps to determine the various characteristic values.

Important characteristic values of the tensile test

• Yield strength (Re): The stress at which the steel begins to flow plastically, i.e. it deforms permanently. This value is used in the European standard (EN).
• 0.2% proof stress (Rp0.2): The stress at which a plastic strain of 0.2% occurs. According to ASTM / ASME, this value is used instead of the yield strength if there is no pronounced yield strength.
• Tensile strength (Rm): The maximum stress that the sample can withstand before it breaks.
• Elongation at break (A5 or A10): The percentage change in length of the sample after fracture, a measure of ductility.
• Modulus of elasticity (E): Describes the stiffness of the steel and indicates how much the material deforms elastically under a certain load.

Standards for the tensile test

The tensile test is carried out in accordance with various international standards in order to ensure uniform comparability of the results:

• EN ISO 6892-1: European standard for the tensile test at room temperature.
• ASTM A370 / ASME SA-370: Standard test method for mechanical testing of steel products, including the tensile test.
• ASTM E8 / E8M: American standard for tensile testing of metallic materials.
• ASME Section II, Part A: Contains requirements for the tensile test in relation to pressure-bearing components.

Importance of the tensile test for the steel industry

The results of the tensile test are essential for quality assurance and material selection. Depending on the area of application – whether in steel and bridge construction, mechanical engineering or tank and apparatus construction – steels must meet specific mechanical requirements. The tensile test helps to check and guarantee these requirements.

Conclusion

The tensile test is an indispensable test method in materials engineering. It provides fundamental information about the behavior of steel under load and contributes to the safe and efficient use of this versatile material.