The rate at which a manufacturer cools steel can affect its strength at the molecular level. The time during which steel is held at critical temperatures during the cooling process also plays an important role. Two steel sheets with the same alloy content may have different grades depending on the heat treatment process. Our ancestors have long noticed: “Iron and steel come out of the same furnace: one becomes a sword, the other becomes a horseshoe.”
Steels are classified according to chemical and structural composition, quality, degree of deoxidation and the nature of metal hardening, as well as by purpose. In this article, we will consider the four main, most popular groups: carbon, alloyed, stainless steel and instrumental.
The most popular type of steel: its share in total production is about 90%. It is characterized by the fact that, in addition to carbon and iron, it contains only trace amounts of other elements. Carbon steel is divided into three main subgroups depending on the carbon content in the metal: low-carbon steels (mild steels) — up to 0.3% carbon, medium carbon steels — 0.3-0.6% carbon, and high-carbon steels — more than 0.6% carbon.
Low production costs and sufficient strength for use in construction are the two main reasons why carbon steel ranks first in the total volume of all steels produced. Its scope of application is the manufacture of various kinds of tools, elements of complex metal structures, machines and mechanisms, cold-formed and hot-forged products. The main condition: these products will not be used in an aggressive environment.
It is created by adding nickel, copper, chromium and aluminum to iron, carbon and manganese. These elements make it possible to increase strength and corrosion resistance, impart ductility, and improve machinability.
Alloy steel is used in the oil industry, power engineering and the chemical industry, and is also used to create special structures that are in conditions of strong contrast in operating temperature and its significant changes.
It contains 10-20% chromium as an alloying element, as well as other metals: nickel, silicon, manganese and carbon. This type of steel is characterized by high corrosion resistance and high suitability for use in outdoor structures, as it has an increased ability to withstand harsh weather conditions.
Stainless steel is also widely used in medicine and the food industry.
Due to the presence of tungsten, molybdenum, cobalt and vanadium in the composition, which increase heat resistance and overall durability, these steels are used in cutting and drilling equipment. They also retain their shape under heavy use, making them the perfect material for most hand tools.
In addition to the above, steels can be structural, special-purpose, boiling, quiet and others — we will definitely talk about them in the following materials.
