Rolled metal: groups, physical characteristics

Rolled steel is made from various alloys that can be divided into two groups:

1. Ferrous metals. Includes iron and alloys with iron as the main constituent.
2. Nonferrous metals. This group includes copper, aluminum, tin, lead, and gold alloys.

All metals and alloys have a crystal structure. Each crystal has a particular shape. When the alloy solidifies, the molecules form a special structure in the form of a strong lattice. If you draw lines between the atoms of such a crystal, you get a lattice of parallelepipeds.

Features of the atomic structure of metals

The iron atoms form a lattice of squares – the perimeter of these squares is very small. When these components come together, a grain is formed. All metals and alloys used to make parts are made up of a large number of grains.

The crystal structure of a metal or alloy can be seen using x-ray equipment. You can see the location of the lattice elements and even determine the distance between them.

The distance between the atoms in such a lattice is extremely small – in the order of angstroms.

What happens when the lattice structure of a metal changes?

In some metals, the lattice changes state. This is called allotropy. This group of metals includes iron, nickel, tungsten, and others. When the crystal lattice changes its structure, the physical properties of the metal also change. If you heat iron to a temperature of 770 C, it will have a three-dimensional and centered lattice that has magnetic properties (it attracts steel and iron parts).

When heated to a temperature of 1400 degrees, the structure becomes face-centered and the magnetic properties disappear. If the temperature is raised above 1400 degrees, the lattice becomes bulky and face-centered again. The transformation of the lattice structure occurs in leaps and bounds.

What should you consider when choosing a metal?

In the process of metalworking, the strength, ductility, and other properties of the metal should be taken into account. The decision is based on the atomic structure of the product. A solid retains its properties due to the attraction of atoms. The attraction force can be calculated.

If we compare the calculations with physical properties, the strength of a metal product is always ten times lower than the theoretical calculations. A wire made of iron should have a tensile strength of 1 ton, but it is unlikely to withstand a load of 40 kg. The reasons for this are defects in the metal structure, grain structure, boundaries, additives, and other factors.

Given the requirements of the metal to be machined, its mechanical capabilities are tested. Based on the results of the test, a decision is made as to whether the part meets the customer’s requirements and can be used for specific purposes. It is important to select high quality raw materials that contain a minimum of impurities, as these change the physical properties of the metal at the molecular level.