Special steel, referred to as special steel, is a collective name for various kinds of steel with certain specific strength, certain chemical composition, certain mechanical properties and certain technological properties. Compared with common structural steel (such as steel bar, round steel, angle steel, steel belt, etc.), special steel has different chemical components, physical and mechanical properties, technological properties and uses, and requires a higher level of production craftsmanship.
Generally speaking, special steel refers to steel with Carbon content (Ccontent) greater than 0.80%, Alloy elements greater than 5.65%, manganese content (Mncontent) greater than 0.45%, silicon content (Silicon) greater than 0.50%, sulfur content (S content ) Larger than 0.05%, phosphorus content (P content) greater than 0.05%, Cu content greater than 0.35%, Ni content greater than 0.35%, Cr content greater than 0.35%.
The types of special steel is very much, it can be divided into the ferrous metal and non-ferrous metal . With respect to the steel, it mainly includes: carbon structural steel, alloy structural steel, low-alloy high strength steel, stainless steel, spring steel and tool steel.
Carbon structural steel mainly contains C and Mn. The main components of carbon-manganese steel are carbon, manganese, iron and a small amount of impurities. Carbon-manganese steel often contains a small amount of Cu, Si, P, S and other elements, the content of these components is very low, generally not more than 0.20%. In addition, some special purpose carbon-manganese steels also contain a small amount of rare elements such as boron, niobium and other components. Carbon structural steel is divided into low carbon steel (carbon content not exceeding 0.25%), medium carbon steel (carbon content between 0.25% and 0.60%), high carbon steel (carbon content greater than 0.60%) )。
Alloy structural steel generally contains one or more alloying elements, the purpose of which is to improve the performance of the steel itself. The most common alloy elements used in alloy structural steel are Molybdenum (Mo), Chromium (Cr), Nickel (Ni), Vanadium (V), Titanium (Ti), Copper (Cu), etc., as well as rare earth elements such as lanthanum, cerium and so on. Also special provisions for the addition of certain elements in the steel, such as Cr + Mo or Cr + Mo + V alloy structural steel, etc.
Low alloy high strength steel is also known as weathering steel, which is low carbon equivalent content compared with ordinary low carbon steel, and a small amount of alloying elements are added to improve its strength and yield strength. In addition, some of the alloying elements can react with the atmospheric oxygen in the air to form a protective film, giving it a unique corrosion resistance. At present, there are many types of low alloy high strength steels, such as Q265, Q345, Q420, Q460, Q550 and so on.
Stainless steel is an alloy steel composed of more than 10.5% chromium as the main alloy element, in addition to the addition of some rare elements such as molybdenum, nickel, nitrogen, etc. It has the advantages of high temperature resistance, corrosion resistance, oxidation resistance and so on. Stainless steel can be divided into three categories: austenitic stainless steel, ferritic stainless steel, martensitic stainless steel and so on.
Spring steel is a kind of alloy steel which is mainly composed of carbon and other alloying elements. Spring steel has high hardness and elasticity and can withstand repeated heavy loads. Generally speaking, spring steel is divided into medium carbon steel with Carbon content between 0.60% and 0.86%.
Tool steel is mainly used to manufacture tools, and its main performance requirements are wear resistance, hardness, red hardness and torsion strength. Commonly used tool steel is carbon tool steel, alloy tool steel and high speed tool steel.
Above is the introduction of special steel, the property of the special steel is much higher than the common steel, so, the special steel are extensively used in many fields, such as in the aerospace, military industry, automobile industry and so on. The demand for special steel is increasing in foreign countries and home, and the special steel industry is blooming.
