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　　Seamless pipe is a kind of long steel with hollow section and no joint around. The seamless pipe has hollow section and can be used as the pipeline for conveying fluid, such as oil, natural gas, gas, water and some solid materials.

　　1. According to different production methods, seamless steel pipe can be divided into hot-rolled pipe, cold-rolled pipe, cold drawn pipe, extruded pipe, etc.

　　2. According to the shape classification, it can be divided into round pipe and special-shaped pipe. In addition to square pipe and rectangular pipe, there are oval pipe, semicircle pipe, triangle pipe, hexagonal pipe, convex pipe, plum shaped pipe, etc.

　　3. According to the different materials, it can be divided into ordinary carbon structure pipe, low alloy structure pipe, high quality carbon structure pipe, alloy structure pipe, stainless steel pipe, etc.

　　4. According to the special use, there are boiler pipe, geological pipe, oil pipe, etc.

　　The advantages of seamless steel pipe are high pressure resistance, good toughness, long pipe section and few joints. It is lighter under the same strength. Manufacturing ring parts can improve material utilization rate, simplify manufacturing process, and save material and processing time. The disadvantage is high price, easy to corrode, so the service life is short.

　　Seamless pipe is widely used. The seamless pipe for general use is rolled by common carbon structural steel, low alloy structural steel or alloy structural steel, with the largest output. It is mainly used as pipeline or structural parts for conveying fluid.

　　According to different uses, it can be divided into three types: A. supply according to chemical composition and mechanical properties; B. supply according to mechanical properties; C. supply according to hydraulic test. If the steel pipes supplied according to a and B are used to bear liquid pressure, hydrostatic test shall also be conducted.

　　There are many kinds of seamless pipes for special purposes, such as boiler seamless pipe, geological seamless pipe and petroleum seamless pipe.

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