Answers

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  What is the difference between galvalume steel sheet and stainless steel?

  1. galvalume steel sheet is designed to extend the service life of the steel sheet by covering its surface with a layer of zinc and aluminum to prevent corrosion. This thin steel sheet that has been galvalume is called galvalume steel sheet.
  The key to the production of galvalume steel sheet lies in the zinc-aluminum coating on its surface. This process effectively prevents the oxidation of the steel surface. Galvalumed steel sheet usually has the characteristics of small zinc flowers, and its surface presents a white tone.
  
  2. Stainless steel is known for its excellent corrosion resistance and can resist erosion by air, steam, water and various chemically corrosive media. The production of stainless steel depends on other metal elements added to the steel. Through the changes in the internal structure of these elements, the product has excellent rust resistance. For example, chromium stainless steel, chromium-nickel stainless steel, and chromium-manganese-nitrogen stainless steel are all common types of stainless steel. The surface of stainless steel is relatively smooth, without any decorations, showing its unique metallic texture.

  
  
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  How to prevent decarburization of thick-walled steel pipes?

  The service life of thick-walled steel pipes is related to the surface decarburization of precision tubes. If the surface is decarburized, the strength and wear resistance of the spiral tube will be reduced, which will directly affect the service life of the spiral tube. If the decarburized layer on the spiral tube is not cleaned, the surface hardness and wear resistance of the spiral tube will be reduced accordingly, and during the quenching process, the change in the volume of the inner and outer layers will cause cracks to form on the surface of the workpiece.
  
  To solve the problem of surface decarburization, it is mainly necessary to deal with the heat treatment process. Because decarburization and oxidation of the spiral tube are carried out at the same time, during the heat treatment process, the thick-walled steel pipe should be kept away from air as much as possible, which can improve the decarburization phenomenon. The media that cause decarburization on the surface of thick-walled steel pipes are mainly oxidizing gases such as oxygen, water vapor and carbon dioxide. When these gases come into contact with the heated spiral tube, they will cause oxidation and decarburization of the spiral tube. Therefore, it is also very important to control the ratio of carbon dioxide and carbon monoxide in the furnace. In fact, adding protective gas nitrogen into the thick-walled steel pipe forging furnace is also very effective. Nitrogen can disperse certain oxidizing gases and reduce the decarburization of the spiral tube.

  
  
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  What is the difference between precision drawn tube and precision rolled tube?

  Precision tube is a high-precision, high-brightness seamless steel tube produced by cold drawing or cold rolling. The inner and outer diameters can be accurate to within 0.2mm or even higher. The surface finish is high and suitable for occasions with high requirements for surface quality. It is light in weight and has excellent mechanical properties and processing properties while ensuring bending and torsional strength. Its mechanical properties and processing properties can be further improved by heat treatment processes such as normalizing, quenching, and tempering.
  
  The precision rolled tube is a seamless steel tube that uses a fine rolling process to ensure the surface smoothness and dimensional accuracy of the inner and outer walls of the tube meet international standard requirements. The outer diameter tolerance of conventional products can be controlled within ±0.05mm, and the wall thickness tolerance is within ±0.1mm; and special industries have higher requirements. It has excellent comprehensive performance, can withstand high pressure, and does not crack or wrinkle during deformation processes such as cold bending, flaring, and flattening. It can perform various complex deformations and mechanical processing, which improves production efficiency and product quality.

  
  

  Precision drawn tube is formed into a tube by mechanical force and drawing force. Specifically, precision-drawn tube is formed into tube by heating the billet from round to manufacturing temperature and then using multiple drawing machines in the pipeline. In this process, the billet is stretched and forged into tube. During the processing of precision drawn tube, the minimum diameter can reach 0.1 mm. The surface of precision drawn tube is smooth, without an oxide layer, and the shape and size of inner and outer walls are controlled very accurately.
  
  Precision rolled tube is made of tube by mechanical rolling. Specifically, the precision rolled tube is first rolled into a mother tube with billet in cooling state and then continuously rolled by multi-pass rolling mill to form it into tube with specified size and shape. Compared with cold drawing method, rolling method has faster processing speed and higher production efficiency.
  The surface of a precision rolled tube is relatively rough, but the inner and outer diameter size accuracy is easier to control, and the minimum diameter can reach 0.8 mm. Compared with precision drawn tube, precision rolled tube has lower production cost, but its product strength and dimensional accuracy are relatively low.