Stainless Steal
General information:
What does stainless steel mean ?
The stainless steel it's fundamentally a steel with with the lowered content of carbon, in which chrome is at least 10% of weight. Exactly this content of chrome is a factor assuring the stainless character of steel. Reaction of the chrome contained in steel with oxygen makes for creation of a very thin (approx. 1/1000 mm), permanent, not visible and stainless layer of the chromium oxide on the surface. This layer is passive i.e. does not react with other substances. In the event of physical or chemical damage this layer automatically regenerates, under condition if there's constant access to a small quantity of oxygen. That′s why the knives performed from stainless steel can be sharpened and polished many times and will never get rusty. Unique proprieties of stainlesss steel can be improved by adding of a greater quantity of chrome and an addition of other components such as molybdenum, nickel. In the fact there's 60 different alloys of stainless steel , but the main partition embraces five groups of steel:
-
chrome - hardenabled with marternisitic structure - this type of steel is hardenabled by effect of high temperature, similar as conventional steels.
-
chrome - non hardenabled with ferritic structure; this alloy consists of not only chrome but also of titanium or aluminum. It is very often used in building constructions.
-
chrome - nickel, non hardnabled with austenitic structure; This alloy consists of less coal than other groups. It is often used in cold environment e.g. for production of beer, wine, in freezers or cold stores.
-
chrome - nickel capable to hardnable, martensitic structure, semi-austenitic or austenitic depends on nickel content. It is capable to hardnable in low temperature.
-
chrome - nickel, non hardenabled, 50% ferritic and 50% austenitic structure. Long resistance, used in chemical industry; hardenable in cold environment.
Discovery
The inventor of stainless steel, Harry Bearleey, was born in 1871 in Sheffield, England. His father was a metallurgist. For the lack of competency, aged 12 he's been forced to abandon school and undertake work in a chemistry laboratory where he washed bottles and containers. Within the next years, he learnt individually and undertook education at an evening-school. This way Harry Bearleey's became an expert, resolving problems connected with metallurgy. Being a well-known expert in the range of metallurgy, in 1908 Bearley's founded Brown Firth Laboratories, which were financed by two smelting works, leading at that time.
In 1912 Bearleey began works over firmer steel, non-eroding under influence of temperature as quickly as conventional steel. One of the experiments which he realized was adding of an admixture of chrome having the higher melting-point to the alloy of steel. He's made many tests, adding from 6% to 15% of chrome conjointly with various content of carbon. So, exactly on 13 August 1913 the first true stainless steel's been made . It contained 0,24% of carbon and 12,8% of chrome at that time . However, the creator was'nt exactly aware of his own success. Not till the next experiments, when Bearley investigated the molecular structure of steel, exposing it to the activity of strongly corrosive acids, it appeared that new steel did not change the structure under the influence of these compounds. Within one year from Bearleey's discovery, Krupp company in Germany passed experiments on the alloys of metals adding nickel. This way they have created a steel more easy in the tooling, more resistant on the activity of acids. Exactly these two explorations gave rise to stainless steel. But only after the I World War experiments of adding various combinations of chrome and nickel to the alloys were started.
The most of today′s kinds of steel have been discovered between 1913 and 1935 in England, Germany, France and America. After the II World War the production of stainless steel became more and more effective, every now and again new varieties began to come into being, more resistant on the activity of acids and with better ratioes of the endurance to the mass. The values of stainless steel become sighted more and more often, it increases the range of uses.
Benefits of stainless steel
-
Corrosion resistance - Lower alloyed grades resist corrosion in atmospheric and pure water environments, while high-alloyed grades can resist corrosion in most acids, alkaline solutions, and chlorine bearing environments, properties which are utilized in process plants;
- Fire and heat resistance - Special high chromium and nickel-alloyed grades resist scaling and retain strength at high temperature;
- Hygiene - The easy cleaning ability of stainless makes it the first choice for strict hygiene conditions, such as hospitals, kitchens, abattoirs and other food processing plants.
- Aesthetic appearance - The bright, easily maintained surface of stainless steel provides a modern and attractive appearance;
- Strength-to-weight advantage - The work-hardening property of austenitic grades, that results in a significant strengthening of the material from cold-working alone, and the high strength duplex grades, allow reduced material thickness over conventional grades, therefore cost savings;
- Ease of fabrication - Modern steel-making techniques mean that stainless can be cut, welded, formed, machined, and fabricated as readily as traditional steels;
- Impact resistance - The austenitic microstructure of the 300 series provides high toughness, from elevated temperatures to far below freezing, making these steels particularly suited to cryogenic applications.
- Long term value - When the total life cycle costs are considered, stainless is often the least expensive material option;
- Value - Stainless steel is more expensive to buy, but also has a greater value later in re-sale;
- Environment protection - There is no problem with utilizing stainless steel. This is a recyclable material.