For welding wire,there are in uaually four types of metals that to be welded
2022-09-17
Many friends think that as long as a worker is a welder, he can weld anything. But this is not the case. There are specialized welders in each field, and their work is mainly divided into welding four types of steel. Which are there?
I represents a class of steel: belongs to carbon steel
The carbon content is less than 1.35% (0.1%~1.2%), and it does not contain other alloying elements except iron, carbon and impurities such as silicon, manganese, phosphorus and sulfur within the limit. The properties of carbon steel mainly depend on the carbon content.
When the carbon content increases, the strength and hardness of the steel increase, and the plasticity, toughness and weldability decrease. Compared with other steels, carbon steel is the earliest used, with low cost, wide performance range and the largest amount.
It is suitable for media such as water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure PN≤32.0MPa and temperature of -30℃~425℃. Commonly used grades are WC1, WCB, ZG25 and high-quality steel 20, 25, 30 and low-alloy structural steel 16Mn.
Ⅱ represents the second-class steel: it belongs to low-alloy steel
Alloy steel with less than 5% of 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 more properties of steel, one or more alloying elements are intentionally added to steel, and the amount of alloy added exceeds When carbon steel has a general content in the normal production method, this steel is called alloy steel.
When the total alloy content is less than 5%, it is called low alloy steel; when the alloy content is between 5% and 10%, it is called medium alloy steel; if it is greater than 10%, it is called high alloy steel.
Ⅲ represents three types of steel: it belongs to martensitic stainless steel, ferritic stainless steel
The 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, which ranges from 11.5%~ 18%, steel with higher chromium content requires higher carbon content to ensure the formation of martensite during heat treatment. The above three Type 440 stainless steels are seldom considered for applications requiring welding, and the type 440 composition is not readily 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 Mo, Ti, Nb and other elements. 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 in the manufacture of atmospheric resistance. , Parts corroded by water vapor, water and oxidizing acid.
The price of ferritic stainless steel is not only relatively low and stable, but also has many unique features and advantages. It has been proved that ferritic stainless steel is an extremely high-quality stainless steel in many applications that were originally considered to be only austenitic stainless steel (300 series). 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 for stainless steel, and its price is relatively stable.
Ⅳ represents four types of steel: austenitic stainless steel, duplex stainless steel
Austenitic stainless steel refers to stainless steel with austenitic structure at room 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 well-known 18Cr-8Ni steel and high Cr-Ni series steel developed on this basis by increasing the content of Cr and Ni and adding Mo, Cu, Si, Nb, Ti and other elements.
Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low, and it is impossible to strengthen it through phase transformation. It can only be strengthened through cold working. If elements such as S, Ca, Se, Te are added, it has good Machinability.
Duplex Stainless Steel (DSS for short) refers to stainless steel with about 50% of ferrite and 50% of austenite, and generally less than 30% of the content of the less phase.
In the case of low C content, the Cr content is 18%~28%, and the 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 both austenitic and ferritic stainless steels. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, and significantly improved intergranular corrosion resistance and welding performance. The 475 ℃ brittleness and high thermal conductivity of element stainless steel have the characteristics of superplasticity.
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 pitting corrosion resistance and is also a nickel-saving stainless steel.
