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　　First, the thicker the wall thickness of the product, the more economical and practical it is. The thinner the wall thickness, the higher its processing cost will be. Second, the technology of the product determines its limited performance. Generally, the precision of seamless pipe is low: uneven wall thickness, low luminance inside and outside the tube, high fixed-scale cost, and the inner and outer surface is also high. It is difficult to remove pock marks and black spots; third, its detection and plastic processing must be off-line. Therefore, it manifests its superiority in high pressure, high strength and mechanical structure.

　　Generally, API 5L GR. B Carbon Steel Seamless Pipe is made by hot rolling or cold rolling of high quality carbon-bonded steel 16Mn, 5MnV and other low alloy structural steels such as 10, 20, 30, 35, 45, or 40Cr, 30CrMnSi, 45Mn2, 40MnB. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. Seamless pipes made of medium carbon steels such as 45 and 40Cr are used to make mechanical parts, such as the stressed parts of automobiles and tractors. Generally use seamless pipe to ensure strength and flattening test. Hot rolled seamlessl pipes are delivered in hot rolling or heat treatment; cold rolling is delivered in heat and heat treatment. Seamless pipes for low and medium pressure boilers: used for manufacturing various low and medium pressure boilers, superheated steam pipes, boiling pipes, water wall pipes, superheated steam pipes for locomotive boilers, large smoke pipes, small smoke pipes and arch brick pipes, etc.

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