1I represents a kind of steel: belongs to carbon steel

Fe Ⅰ (carbon steel): Q235, 20 #, 20g, 20R, L210, S205, HP265, etc.

I represents a class of steel: belongs to carbon steel

Fe Ⅰ (carbon steel): Q235, 20 #, 20g, 20R, L210, S205, HP265, etc.

Steel with carbon content less than 1.35% (0.1% -1.2%), excluding iron, carbon and silicon, manganese, phosphorus, sulfur and other impurities within the limit, excluding other alloy elements. Carbon content. Compared with other steel types, the use of carbon steel starts with low cost, wide performance range, and the largest amount. It is suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure PN ≤32.0MPa and temperature of -30-425 ℃. Common grades are WC1, WCB, ZG25 and high-quality steel 20, 25, 30 and low alloy structural steel 16 Mn.

Class II steel

Ⅱ represents the second class steel: it belongs to low alloy steel

FeⅡ (low alloy steel): 16MnR, 12Cr1MoV, 20MnMoD, S240, L245, HP295, etc.

Alloy steel with less than 5% total alloying elements is called low alloy steel. Low alloy steel is relative to carbon steel. On the basis of carbon steel, in order to improve one or several properties of steel, one or several alloy elements are intentionally added to the steel. The amount of alloy added exceeds When the general content of the normal production method of carbon steel has, this kind of steel is called alloy steel.

When the total amount of alloy is less than 5%, it is called low alloy steel. Alloy content between 5-10% is called medium alloy steel; more than 10% is called high alloy steel.

Ⅲ types of steel

Ⅲ represents three types of steel: martensitic stainless steel, ferritic stainless steel, chromium-molybdenum steel

FeⅢ (martensitic, ferritic stainless steel): 1Cr5Mo, 0Cr13, 1Cr17, 1Cr9Mo, etc.

Standard martensitic stainless steels are: Types 403, 410, 414, 416, 416 (Se), 420, 431, 440A, 440B, and 440C, which are magnetic; the corrosion resistance of these steels comes from “chromium” and ranges from 11.5 to 18%, the higher the chromium content of the steel, the higher the carbon content to ensure the formation of martensite during heat treatment. The above three 440 stainless steels are rarely considered for applications requiring welding, and the 440 composition Melt-filled metals are not easily available.

Ferritic stainless steel (400 series) has a chromium content of 15% to 30% and has a body-centered cubic crystal structure. This type of steel generally does not contain nickel, and sometimes contains a small amount of elements such as Mo, Ti, and Nb. This type 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 produce atmospheric resistance. , Water vapor, water and oxidizing acid corrosion parts.

The price of ferritic stainless steel is not only relatively low and stable, but also has many unique characteristics and advantages. It has been proved that in many applications that originally believed that only austenitic stainless steel (300 series) can be used, ferritic stainless steel is an extremely An excellent alternative material, ferritic stainless steel does not contain nickel. The main elements are chromium (> 10%) and iron. Chromium is a particularly corrosion-resistant element of stainless steel, and its price is relatively stable.

Ⅳ types of steel

Ⅳ represents four types of steel: austenitic stainless steel, duplex stainless steel

Fe Ⅳ (Austenitic, duplex stainless steel) Austenitic stainless steel refers to stainless steel having an austenite structure at normal temperature. When the steel contains Cr about 18%, Ni 8% ~ 10%, and C about 0.1%, it has a stable austenite structure.

Austenitic chromium-nickel stainless steel includes the well-known 18Cr-8Ni steel and high Cr-Ni series steel developed by adding Cr, Ni content and adding elements such as Mo, Cu, Si, Nb, Ti.

Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low, it is impossible to strengthen it by phase transformation, and it can only be strengthened by cold working. Free cutting.

Duplex Stainless Steel (DSS) refers to ferrite and austenite each accounting for about 50%, and generally the stainless steel with a minimum phase content of at least 30%. In the case of low C content, Cr content is 18% ~ 28%, Ni content is 3% ~ 10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti, and N.

This type of steel has the characteristics of austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, and has significantly improved intergranular corrosion resistance and welding performance, while maintaining iron. The 475 ° C brittleness and high thermal conductivity of plain stainless steel are characterized by superplasticity.

Compared with austenitic stainless steel, the strength is high and the resistance to intergranular corrosion and chloride stress corrosion is significantly improved. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel.