Answers

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  What is the difference between cold-drawn wire and galvanized wire?

  Cold-drawn wire: The raw material is wire rod, which is what we often call rebar. It is processed by the cold drawing process. In this process, the metal wire is stretched through a drawing die at room temperature, so that its size is reduced and its strength is increased. Cold drawing usually does not change the chemical composition of the metal. The surface of cold-drawn wire is relatively smooth, and there is no obvious oxide scale. At the same time, during the drawing process, a variety of surface treatments can be performed, such as polishing, wire drawing, copper plating, sandblasting, etc. Cold-drawn wire has high strength but low plasticity. It can be used as a material for drawing high-carbon steel wire, and can also be used to manufacture carbon structural steel with small and medium cross-section sizes, as well as building structural steel and rebars.
  
  Galvanized wire: It is a process of coating a layer of zinc on the surface of the metal wire. It is usually carried out under the conditions of hot-dip galvanizing or electrogalvanizing. Galvanizing can prevent the metal wire from rusting and improve its corrosion resistance. There is a layer of zinc on the surface of the galvanized iron wire, which has a silver color. Galvanized wire has good toughness and elasticity, and has the characteristics of thick galvanized layer and strong corrosion resistance.

  
  
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  What causes cracking in stainless steel welding?

  Hot cracks refer to the hot cracks generated when the weld and heat-affected zone metal cools to the high temperature range near the solidus during welding.
  
  Cold cracks refer to the cold cracks generated when the weld joint cools to a lower temperature (i.e., below the temperature at which austenite begins to transform into martensite).
  
  Reheat cracks refer to the cracks generated when the stainless steel plate is heated again within a certain temperature range after welding (stress relief heat treatment or other heating process) and then produced.
  
  Stainless steel is a type of delayed crack steel. This type of steel has a lower thermal conductivity than ordinary carbon steel, a higher expansion coefficient, and slow heat conduction. It is easy to expand when heated and the expansion amplitude is large. Based on this property, many problems may occur in the welding process of stainless steel plates, such as undercut, pores, lack of fusion, cracks, etc.

  
  

  Factors that cause cracking in stainless steel after welding include improper welding process, influence of material properties, improper preparation and handling, and stress changes during operation.
  
  Stainless steel itself contains elements such as chromium and nickel, has excellent corrosion resistance and high temperature resistance, and is not easy to rust and deform during use. However, if the material quality is poor or impurities are mixed in, it will cause cracking during welding.
  
  From the perspective of welding process, inappropriate welding parameters, uneven heating speed, and lack of proper cooling conditions may all lead to cracking. Stress caused by thermal expansion and contraction during stainless steel welding is also one of the main causes of cracking. The heat capacity and thermal conductivity of the material will also affect the stress of welding. If the temperature and stress distribution are not properly controlled during welding, welding cracking will occur.

  
  
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  Analysis of the causes of steel fracture?

  The main components of steel are iron and carbon, but different types of steel also contain some other elements, such as manganese, silicon, etc. The content of these elements and the heat treatment method of steel will affect the properties of steel, and then affect its durability and tensile strength. A certain amount of one or more alloying elements must be added during the smelting of steel. After the material is formed, a simple heat treatment can be performed to obtain different microstructures, thereby changing the original properties of the steel; If the carbon content of steel is too high or the treatment method is improper, it will cause it to break easily.
  
  The production process of steel will also affect its properties. If the temperature, cooling rate and other factors in the production process are not properly controlled, defects will occur inside the steel, making it easy to break. In addition, if there are defects or unevenness on the surface of the steel, it will also affect its service life and safety.
  
  
  Because the defects generated during steelmaking and casting, especially concentrated defects (such as pores, inclusions, etc.) are extremely sensitive during rolling, and different changes occur between different furnaces of steel with the same chemical composition, and even in different parts of the same billet, thus affecting the quality of the steel.