Definition
Stainless Steel is a sub-category of alloy steels, Stainless steel is made by adding a certain amount of chromium (Cr) to the carbon steel.In the field of materials science, the chromium (Cr) content greater than 10.5%, and corrosion resistance and stainless steel as the main use of a series of iron-based alloys called stainless steel.
When the chromium content in the steel is higher than 10.5%, chromium reacts chemically with the oxygen in the corrosion medium.Chromium produces a thin, passive and self renewable layer of chromium oxide on the surface of the steel. This layer prevents any further corrosion on the inside or the outside of the surface. This property is what distinguishes stainless steel from other steels.
Development History
Stainless steel has gone through 3 main stages of development
The invention of stainless steel
Discovery of the stainless steel goes back to early 1900's in Sheffield, England. In 1912, the British metallurgist Harry Brearley in the smelting test found that chromium-iron alloy has the characteristics of corrosion resistance, stainless steel was invented.
Stage one：Small-scale production
From the early 20th century to the early 1950s, Britain, the United States, Germany and other countries, gradually carried out theoretical research on stainless steel, product development and small-scale production. During this period, the application of stainless steel mainly in some special requirements of corrosion resistance, high-temperature resistant fields.
Stage two：Large-scale development
From the 1950s to the mid-1980s.The stainless steel smelting technology represented by off-furnace refining, continuous casting technology and multi-roller cold rolling mill technology have been developed successfully, promoting the development of the world's stainless steel scale. In this period, the application of stainless steel gradually civilianization, began to enter the common people's homes.
Stage three：High growth
From the mid-1980s to the present.The rapid development of the consumption of stainless steel, especially the rapid economic development of China and other Asia-Pacific countries, as well as the large number of stainless steel into the civilian sector, led to the rapid growth of the world's stainless steel production, global stainless steel production 52.218 million tons in 2019, continued to record high.
Stainless steel has been one of the fastest growing industries over the past 100 years. Since 1950, global production has expanded from about 1 million tons to more than 50 million tons in 2018, a 5.5% year-over-year increase.
Composition
Usually,stainless steels contain Iron (Fe), Chrome (Cr), Carbon (C), Silicon (Si), Manganese (Mn) and Nickel (Ni).
Depending on the grade of stainless steel, chromium (Cr), carbon (C), nickel (Ni), molybdenum (Mo), silicon (Si), manganese (Mn), copper (Cu), titanium (Ti), sulfur (S), niobium (Nb) and other elements are also added or removed.
In our next article What are the components used in stainless steel? we will also discuss in detail the different components of stainless steel and how they affect stainless steel.