Mechanical properties of metals and alloys

The carbon content determines the mechanical qualities of steels, the most characteristic of which is the hardness obtained by the quenching process. Depending on this carbon content, a distinction is made between mild steels (C22) and semi-hard steels (C35 and C45). The carbon content also determines the weldability of a metal. A carbon rate greater than 0.40% requires taking precautions. The more carbon steel has, the harder it is, the lower its degree of weldability.

Other properties had to be researched to meet the needs of the industry—for example, elasticity.

Elasticity is the property that metal has to undergo a temporary deformation under the action of an appropriate force. Then to return to its initial dimensions, Steel Supplier Singapore has to remove this force. It is thanks to the elasticity of metals that we can use tools without permanently deforming them. The elastic limit represents the point from which the part is permanently deformed.

Mechanical tests

If by inheritance of know-how or habit, the user knows which steel to use, it remains too empirical in many applications. Thus, various mechanical tests make it possible to determine the steel suitable for a defined use. Some tests measure the ability of a material to bend, to stamp … Other tests measure:

– The resistance of a metal to penetration forces (hardness test).

– Its elasticity (tensile test)

– Its impact resistance (toughness) and its fragility (impact test)

It should be noted that today the manufacture of steel is controlled. The Mild Steel Supplier Singapore knows with precision their behaviour and, therefore, their physical constants, which have been established by a multitude of tests. Also, steels are isotropic materials: they react in the same way to stresses made in all observation directions.

Hardness testing: Brinell indentation or penetration methods

The test consists of balling a metal, i.e., driving an extra hard steel ball onto its surface, measuring the imprint left by the ball using a ruler, and reading its hardness on aboard. The hardness of a metal, symbolized by the letter H is the resistance it offers to penetration efforts. This test has the benefit of being possible in workshops. The device used to measure hardness is a durometer.

Other hardness measurement methods also exist in the Vickers method (a diamond replaces the ball) used for very hard metals or the Rockwell method (HR).

Tensile strength tests

A simple way to characterize the behaviour of the steel is to perform a tensile test. The concept of resistance translates both the concept of resistance to deformation and the tensile strength.

The test consists of stretching a sample of metal called a test piece, measuring its elastic limit point, and its elongation until it breaks. When you stretch steel, you first enter its elastic zone: the metal can return to its original dimensions. Then, Metal Supplier Singapore reaches the point of the elastic limit (Re). Beyond that, the metal deforms, hardens, micro cracks appear: the elongation ceases to be temporary and becomes permanent. The metal is work hardened. It is in the so-called plasticity zone.