There are different types and kinds of steel, which differ in chemical composition, structure, physical and mechanical properties.
According to chemical composition steel can be divided into carbon and alloy. Carbon Steel along with iron and carbon contains manganese (0.1-1.0%), silicon (0.4%). Steel also contains harmful impurities (phosphorus, sulfur gases – nitrogen and oxygen are unrelated). Phosphorus makes steel brittle (cold brittleness) at low temperatures, reduces the ductility when heated; while sulfur causes the fracture at high temperatures (hot brittleness). For welded constructions is used mainly carbon steel of ordinary quality.
In order to add or change some steel properties (mechanical, electrical, magnetic, corrosion resistance, etc) it is necessary to add the so-called alloying elements, usually metals: chromium, nickel, molybdenum, aluminum, etc. such steel is called alloy. The properties of steel can be changed by applying different methods of processing: thermal (quenching, annealing), chemical and thermal (nitriding), thermo-mechanical (rolling, forging). When processing steel to produce the desired structure using the property of polymorphism, were inherent in the same way as their basis – iron.
By application of steel it is divided into structural, instrumental and steel with special properties. Structural steel is used for the manufacture of building structures, machine parts and mechanisms, ship hulls and car and steam boilers. Tool steels are used for the manufacture of cutting tools, dies and other cutting, stamping and shock measuring instruments. Steels with special properties include electrical, corrosion, acid, etc.
It is necessary to point stainless steel that is resistant to corrosion in air, water, and other environment influence. The most common are chromium-nickel (18% Cr b 9% Ni) and chromium (13-27% Cr) stainless steel, often with the addition of Mn, Ti and other elements. The addition of chromium increases the resistance of steel to oxidation and corrosion, and such steel retains its strength at high temperatures. (Smith, 2006)
Reliability of components made of stainless steel is much higher than other building materials, and their appearance does not change throughout the decades. Stainless steel has much higher heat resistant properties than any other steel, that is why it is used in all spheres of human activity, ranging from heavy engineering, electronics and finefinishing mechanics. It is widely used in:
”˘ Construction and architecture.
”˘ Food industry.
”˘ household appliances.
”˘ Chemical and petrochemical industries.
”˘ Pulp and paper production.
”˘ Environmental Protection.
Steel is the hardest material with the very stable characteristics. It is undoubtedly the most powerful weapon in the hands of the engineers and constructors. Due to its properties, steel allows to create and design machines, bridges and skyscrapers and other constructions reliable even under the most severe operating conditions. For a number of reasons steel is one of the most extensively used building material, as it is uniform, resilient, and is almost adequate to the ideal of structural mechanics. Steel becomes indispensable in all cases of particularly complex construction practices. (Smith, 2006)
Steel is the most important construction material for engineering, transport, construction and other industries.
Every year the world produces 500 million tons of steel. About half of this impressive amount accounts for low-carbon, mild steels. (Smith, 2006)
It is known that very important are the chemical composition of the material, methods of melting, casting and heat treatment. About 62% of the world’s steel is obtained by the open-hearth method which was proposed in 1867, and now there are two kinds of open-hearth steel – boiling and reassured. Boiling open-hearth steel is cheaper, so as soon as its boiling point is poured into a special bucket, which completes the process, but its quality is lower, as there are a lot of dissolved gases, including such pests as nitrogen. At some point, such as welding, it can play a negative role, that’s why for important welded structures is used reassured open-hearth steel. As for the converter steel, its purity is even lower than the boiling open-hearth steel, which greatly limits the possibilities of its application.
But along with its undeniable qualities as a building material, steel also has shortcomings that severely limit its scope of use. The big downside is, for example, susceptibility to weathering – corrosion. Each year, corrosion is doing great damage, as steel construction left without any coverage for a short time become a corroded skeleton, ready to collapse at any moment, against which there is no single recipe. Steel structures require constant care, they need to be regularly covered with the anti-corrosion compounds over the entire lifetime. Also steel is exposed to high temperatures, that is the cause of considerable internal stresses in the elements of steel structures. (Smith, 2006)
It also should be noted that the steel is an expensive material. Its production is associated with significant investment, it involves a complex process cycle and the availability of highly skilled professionals. Production of steel structures is a complex process, because it material must be processed by special machines in the factory.
Bugayev, K.; Konovalov, Y.; Bychkov, Y.; Tretyakov, E.; Savin, Ivan V. Iron and Steel Production. The Minerva Group, 2001
“Iron and steel industry”ť. Britannica. Encyclopaedia Britannica. 2007. Web. Accessed 8 June 2011
Smith, William F.; Hashemi, J. Foundations of Materials Science and Engineering (4th ed.). McGraw-Hill, 2006
Hyde, C. K. Technological Change and the British iron industry. Princeton , 1977