Answers

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  Why is the surface of galvanized angle steel rough?

  The thickness of the zinc coating directly affects the roughness of the surface of the galvanized angle steel. When the zinc layer is thicker, due to the difference in thermal expansion and contraction between the zinc and the steel substrate, the zinc layer is prone to forming microcracks during the cooling process, resulting in a rough surface. This phenomenon is more obvious when the zinc layer is thicker.
  
  During the hot-dip galvanizing process, the roughness of the surface of the angle steel will also be affected to a certain extent during the period from the time the angle steel is taken out of the zinc bath to the end of cooling. If the cooling process is too rapid, the atomic structure on the surface of the zinc layer cannot be completely smooth, resulting in a rough surface. In addition, if the angle steels are stacked together without being properly isolated after hot-dip galvanizing, the heat generated by friction will aggravate the roughening of the surface of the zinc layer.
  
  In addition, the composition and surface conditions of the steel used also affect the roughness of the galvanized layer. Different steel compositions and surface treatment methods will result in different parameters such as the bonding strength and surface flatness of the zinc layer and the steel substrate, which will in turn affect the final appearance of the galvanized layer. Impurities such as scale and oil on the surface of the steel will increase the roughness of the zinc layer and affect its flatness.

  
  
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  What are the main differences between TP304 stainless steel pipe and 304 stainless steel pipe?

  TP304 and 304 are the same material, but the expression method is different.
  TP304 is the expression method of the American standard. TP is the abbreviation of tube and pipe, which means stainless steel pipe used for piping. It is mainly used in the field of piping, especially in occasions requiring high corrosion resistance, such as water treatment and heat exchange tubes.
  304 is the expression method of the international standard and also the brand of the Chinese national standard, called 0Cr18Ni9. Due to its good comprehensive performance, it is widely used in the manufacture of equipment and parts that require these characteristics.
  
  In actual use, TP304 and 304 have some gaps in their chemical composition. According to the provisions of the American standard and the Chinese national standard, the carbon content, phosphorus content, sulfur content, etc. of TP304 and 304 have certain range requirements. Among them, the chromium content of TP304 is higher, reaching more than 18%, while the chromium content of 304 is required to be between 17% and 19%. This makes TP304 more corrosion-resistant than 304, but also more expensive.
  
  In addition to TP304 and 304, there is a stainless steel pipe called 304L. It is a variant of 304 stainless steel pipe. The main difference is that it has a lower carbon content, less than or equal to 0.03%. The purpose of this is to improve its welding performance. Because the lower the carbon content, the less carbides are produced during welding, and the risk of intergranular corrosion can be avoided.
  
  TP304 and 304 stainless steel pipes are the same material, but the expression method is different. They both have good comprehensive properties and are suitable for various occasions. However, there are still some differences in chemical composition, mainly reflected in the chromium content. TP304 is more corrosion-resistant than 304, but also more expensive. Which type of stainless steel pipe to choose depends on the specific application scenario and needs.

  
  
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  What is the maximum diameter of welded steel pipe?

  The diameter range of large-diameter welded pipes is relatively wide. Generally speaking, the diameter of large-diameter welded pipes is usually above 500 mm. In some specific engineering fields, the diameter can reach several meters or even larger.
  
  In some large oil pipeline projects, the diameter of large-diameter welded pipes may reach more than 1000 mm.
  
  In urban water supply and drainage projects, the diameter of large-diameter welded pipes is usually between several hundred millimeters and one or two meters, and is used to transport large amounts of domestic water and sewage.

  
  

  Welded steel pipe, also known as spiral welded pipe, is a steel pipe made by welding steel plates or strips after curling and forming. Welded steel pipe has a simple production process, high production efficiency, many varieties and specifications, and low equipment investment, but its general strength is lower than that of seamless steel pipe. The maximum diameter of spiral steel pipe is currently produced to 4020mm.
  Due to the limitations of the manufacturing process, the diameter of the spiral pipe cannot be increased indefinitely. The maximum diameter of the spiral pipe can reach 4020mm. As the diameter increases, the thickness of the steel pipe will also increase accordingly to withstand greater pressure and provide stronger support. Therefore, a balance needs to be achieved between the length and diameter of the spiral pipe.