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The gray spots of different sizes on the surface of galvanized seamless steel pipes are the color difference of galvanizing, which is a problem in the current galvanizing industry. It is mainly related to the trace elements contained in the steel pipe itself and the components in the zinc bath. The stains do not affect the anti-corrosion performance of the steel pipe, but only differ in appearance. On the surface of each galvanized seamless steel pipe, there are gradually obvious raised marks, which are all zinc. The galvanized seamless steel pipe is taken out of the zinc pot, and the zinc liquid flows down the pipe wall and then cools and solidifies.

There are traces of grinding and painting near both ends of each galvanized seamless pipe. During hot-dip galvanizing, the pipe should be fixed on a special steel frame and immersed in zinc liquid together with the steel frame. Ba marks will be left where it is fixed after galvanizing. For the sake of beauty, it will be polished and zinc sprayed. Some customers will use grooved connections to press grooves during the use of galvanized seamless pipes. Because the zinc layer of hot-dip galvanized seamless pipes is thicker, part of the galvanized layer will crack and peel off under the action of destructive external forces, which has nothing to do with the quality of the galvanized seamless pipes themselves.
Some customers will report that there is yellow liquid on the galvanized seamless pipe (this liquid is called passivation liquid), which can passivate the metal surface. It is generally used for post-plating treatment of galvanized, cadmium and other coatings. The purpose is to form a surface state on the coating surface that can prevent the normal reaction of the metal, improve its corrosion resistance, and increase the aesthetics of the product. It can effectively improve the corrosion resistance of the steel pipe and extend the service life of the workpiece.
Characteristics of seamless pipes:
1. Domestic seamless steel pipes and carbon structural steels supplied according to organizational characteristics shall be manufactured according to Grade A steel in GB/T700-88 (but the sulfur content and phosphorus content shall not exceed 0.050% and 0.045% respectively), and their physical properties shall comply with the standard values specified in GB8162-87.
2. Domestic seamless steel pipes supplied according to pressure tests need to ensure the pressure test specified in the specification.
3. The mechanical property test of imported seamless steel pipes shall be carried out in accordance with the relevant specifications agreed in the contract.
Precision seamless pipes are a kind of high-precision steel pipe material after cold drawing or hot rolling. Because there is no oxide layer on the inner and outer walls of precision steel pipes, there is no leakage under high pressure, high precision, high finish, no deformation when cold bending, and no cracking when expanding and flattening, it is mainly used to produce pneumatic or hydraulic components, such as cylinders or oil cylinders, which can be seamless pipes or welded pipes.
Compared with solid steel such as round steel, seamless steel pipes are lighter in weight under the same bending and torsional strength. It is an economical cross-section steel widely used in the manufacture of structural parts and mechanical parts. Precision steel pipe inherits the advantages of seamless steel pipe and has its own characteristics. The precision manufacturing of ring parts can improve material utilization, simplify the manufacturing process, save materials and processing time, such as rolling bearing rings, jack sleeves, etc. This has been widely manufactured by precision steel pipe.