Types of stainless steel
Types of stainless steel
physical classification
microstructure of Austenitic Stainless Steel
in layman's terms, stainless steel is steel that is not easy to rust. In fact, some stainless steel has both rust resistance and acid resistance (corrosion resistance). The stainless and corrosion resistance of stainless steel is due to the formation of a chromium-rich oxide film (passivation film) on its surface. This rust resistance and corrosion resistance are relative. Tests show that steel is in weak media such as atmosphere, water and oxidizing media such as nitric acid. Corrosion resistance varies with steel the increase of chromium content increases. When the chromium content reaches a certain percentage, the corrosion resistance of steel will change suddenly, that is, from easy to rust to not easy to rust, and from never corrosion resistance to corrosion resistance. There are many ways to classify stainless steel. According to the tissue structure at room temperature, there are mars size, austenite type, ferrite and duplex stainless steel; According to the main chemical composition, it can basically be divided chromium stainless steel and chromium nickel two major systems of stainless steel; According to the purpose, there are nitric acid-resistant stainless steel, sulfuric acid-resistant stainless steel, seawater-resistant stainless steel, etc, according to corrosion resistance types can be divided into pitting-resistant stainless steel, stress-resistant stainless steel, intergranular corrosion-resistant stainless steel, etc.; According to the functional characteristics of the classification can be divided nonmagnetic stainless steel, free cutting stainless steel, Low temperature stainless steel, high strength stainless steel, etc. Due to stainless steel the material has excellent corrosion resistance, formability, compatibility and strength and toughness in a wide temperature range, so in heavy industry, light industry, it is widely used in the daily necessities industry and architectural decoration industry.[1]
ferritic stainless steel stainless steel with ferrite structure in use. Chromium content in11% ~ 30%, Has a body-centered cubic crystal structure. This kind steel General excluded nickel, sometimes also contains a small amount Mo, Ti, Nb wait for the element, this kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance, and excellent stress corrosion resistance. It is mostly used to manufacture parts that are resistant to atmospheric, water vapor, water and oxidizing acid corrosion. This kind steel exists defects such as poor plasticity, significantly reduced plasticity and corrosion resistance after welding limit its application. Out-of-furnace refining technology ( AOD or VOD) The application can greatly reduce the interstitial elements such as carbon and nitrogen, so this type of steel is widely used.
Austenite-- ferritic duplex stainless steel is a stainless steel with about half of austenitic and ferrite structures. In the presence C in the lower case, Cr the content is in18% ~ 28%, Ni the content is in3% ~ 10%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloying elements. This type of steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, and significantly improved intergranular corrosion resistance and welding performance, at the same time, it also maintains ferritic stainless steel.475℃ brittle and high thermal conductivity, with superplasticity and other characteristics. Compared with austenitic stainless steel, it has high strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel has excellent pore corrosion resistance performance, is also a nickel-saving stainless steel.
Martensite stainless steel through heat treatment can adjust its mechanical properties of stainless steel, in layman's terms, is a kind of hardenable stainless steel. Typical grades are Cr13 type, such2Cr13,3Cr13,4Cr13 etc. Quintessence the hardness is higher after fire, and different tempering temperatures have different combinations of strength and toughness. It is mainly used for steam turbine blades, tableware, and surgical instruments. According to the difference in chemical composition, martensitic stainless steel it can be divided into martensitic chromium steel and martensitic chromium nickel steel. According to the different structure and strengthening mechanism, it can also be divided into martensitic stainless steel, martensite and semi-austenite (or semi-martensite) precipitation hardening stainless steel and maraging stainless steel etc.
