Four types of steel
We all know whether it is a building or a vehicle or a tool for everyday use. Most have steel components in it. Therefore, steel is everywhere in our daily lives. Different steels are also in different places. So the steel is also divided into 4 types.
I stands for the first class steel: it belongs to carbon steel. Its carbon content is less than 1.35% (0.1%~1.2%), except for iron, carbon and limited impurities such as silicon, manganese, phosphorus and sulfur. Steel without other alloying elements. The performance of carbon steel depends mainly on the carbon content. As the carbon content increases, the strength and hardness of the steel increase, while the ductility, toughness, and weldability decrease. Compared with other steels, carbon steel is the earliest use, low cost, wide performance range and maximum dosage. It is suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure PN≤32.0MPa and temperature -30~425°C. The first class steel commonly used are WC1, WCB, ZG25 and high-quality steel 20, 25, 30 and low-alloy structural steel 16Mn.
II stands for the second class steel: it belongs to low alloy steel. Its alloying elements are less than 5% of alloy steel, and it is also called low alloy steel. Low alloy steel is relative to carbon steel and is based on carbon steel. In order to improve one or several properties of steel. And intentionally add one or several alloying elements to the steel. When the amount of the alloy added exceeds the general content of the normal production method of the carbon steel, the steel is referred to as an alloy steel. When the total amount of the alloy is less than 5%, it is called low alloy steel. Alloy content between 5-10% is called medium alloy steel and more than 10% is called high alloy steel.
III stands for the third class steel: Martensitic stainless steel, ferritic stainless steel. Standard martensitic stainless steels are: 403, 410, 414, 416, 416 (Se), 420, 431, 440A, 440B, and 440C, which are magnetic. The corrosion resistance of these steels comes from "chromium", which ranges from 11.5% to 18%. The higher the chromium content, the higher the carbon content required. This is to ensure the formation of martensite during the heat treatment. The above three types of 440 stainless steels are rarely considered as applications requiring welding, and the filler metal of the 440 type component is not easily obtained. Ferritic stainless steel (400 series) contains 15% to 30% chromium and has a body-centered cubic crystal structure. These steels generally do not contain nickel, and sometimes contain small amounts of elements such as Mo, Ti, and Nb. This kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance and excellent resistance to stress corrosion. It is mostly used to manufacture parts resistant to atmospheric, water vapor, water and oxidizing acids. The price of ferritic stainless steel is not only relatively low and stable, but also has many unique features and advantages. Tests have proven that ferritic stainless steel is an excellent alternative to many applications where austenitic stainless steels (300 series) were originally considered to be used. Ferritic stainless steel does not contain nickel, the main element is chromium (>10%) and iron, the chromium is a particularly corrosion-resistant element of stainless steel, and its price is relatively stable.
IV stands for the fourth class steel: austenitic stainless steel, duplex stainless steel. Austenitic stainless steel refers to stainless steel having an austenite structure at a normal temperature. When the steel contains about 18% Cr, 8%-10% Ni, and about 0.1% C, it has a stable austenite structure. Austenitic chromium-nickel stainless steel includes the famous 18Cr-8Ni steel and high Cr-Ni series steel which is added with elements of Cr and Ni and added with elements such as Mo, Cu, Si, Nb and Ti. Austenitic stainless steel is non-magnetic, although it has high toughness and plasticity, but its strength is low. Therefore, it is impossible to strengthen it by phase transformation, and it can only be strengthened by cold working. If S, Ca, Se, Te and other elements are added, it has good machinability. Duplex Stainless Steel (DSS) refers to about 50% of ferrite and austenite, and generally requires less than 30% of stainless steel. In the case of a lower C content, the Cr content is between 18% and 28%, and the Ni content is between 3% and 10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti, and N. This type of steel combines the characteristics of austenitic and ferritic stainless steels, compared with ferrite. Its plasticity, toughness, no room temperature brittleness, resistance to intergranular corrosion and welding performance are significantly improved. At the same time, it also maintains 475°C brittleness and high thermal conductivity of ferritic stainless steel, and it has superplasticity. Compared with austenitic stainless steel, it has high strength and resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel has excellent pitting resistance and is also a nickel-saving stainless steel.
I stands for the first class steel: it belongs to carbon steel. Its carbon content is less than 1.35% (0.1%~1.2%), except for iron, carbon and limited impurities such as silicon, manganese, phosphorus and sulfur. Steel without other alloying elements. The performance of carbon steel depends mainly on the carbon content. As the carbon content increases, the strength and hardness of the steel increase, while the ductility, toughness, and weldability decrease. Compared with other steels, carbon steel is the earliest use, low cost, wide performance range and maximum dosage. It is suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure PN≤32.0MPa and temperature -30~425°C. The first class steel commonly used are WC1, WCB, ZG25 and high-quality steel 20, 25, 30 and low-alloy structural steel 16Mn.
II stands for the second class steel: it belongs to low alloy steel. Its alloying elements are less than 5% of alloy steel, and it is also called low alloy steel. Low alloy steel is relative to carbon steel and is based on carbon steel. In order to improve one or several properties of steel. And intentionally add one or several alloying elements to the steel. When the amount of the alloy added exceeds the general content of the normal production method of the carbon steel, the steel is referred to as an alloy steel. When the total amount of the alloy is less than 5%, it is called low alloy steel. Alloy content between 5-10% is called medium alloy steel and more than 10% is called high alloy steel.
III stands for the third class steel: Martensitic stainless steel, ferritic stainless steel. Standard martensitic stainless steels are: 403, 410, 414, 416, 416 (Se), 420, 431, 440A, 440B, and 440C, which are magnetic. The corrosion resistance of these steels comes from "chromium", which ranges from 11.5% to 18%. The higher the chromium content, the higher the carbon content required. This is to ensure the formation of martensite during the heat treatment. The above three types of 440 stainless steels are rarely considered as applications requiring welding, and the filler metal of the 440 type component is not easily obtained. Ferritic stainless steel (400 series) contains 15% to 30% chromium and has a body-centered cubic crystal structure. These steels generally do not contain nickel, and sometimes contain small amounts of elements such as Mo, Ti, and Nb. This kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance and excellent resistance to stress corrosion. It is mostly used to manufacture parts resistant to atmospheric, water vapor, water and oxidizing acids. The price of ferritic stainless steel is not only relatively low and stable, but also has many unique features and advantages. Tests have proven that ferritic stainless steel is an excellent alternative to many applications where austenitic stainless steels (300 series) were originally considered to be used. Ferritic stainless steel does not contain nickel, the main element is chromium (>10%) and iron, the chromium is a particularly corrosion-resistant element of stainless steel, and its price is relatively stable.
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