3.1. Domestic seamless pipe supplied according to the performance of the mechanism. Ordinary carbon steel is made according to GB/T700-88 Class A steel (but the sulfur content must not exceed 0.050% and the phosphorus content does not exceed 0.045%). The performance shall comply with the values specified in the table of GB8162-87.

3.2. The domestic seamless pipe supplied according to the hydraulic test must guarantee the water pressure test specified in the standard.

3.3. The physical property test of the imported seamless pipe shall be carried out in accordance with the relevant standards stipulated in the contract.

2, use 2.1, seamless pipe is widely used. The general-purpose seamless pipe is rolled from ordinary carbon structural steel, low-alloy structural steel or alloy structural steel, and has the largest output, and is mainly used as a pipe or structural part for conveying fluid.

2.2, according to the use of three types of supply: a, according to chemical composition and mechanical properties; b, according to mechanical properties; c, according to water pressure test supply. Steel pipes supplied in categories a and b, if used to withstand liquid pressure, are also subjected to hydrostatic testing.

2.3. Special-purpose seamless pipes include boiler seamless pipes, geological seamless pipes, and petroleum seamless pipes.

3, type

3.1. Seamless steel pipes can be divided into hot rolled pipes, cold rolled pipes, cold drawn pipes and extruded pipes according to different production methods.

3.2. According to the shape, there are round tubes and special-shaped tubes. In addition to the square tube and the rectangular tube, the special-shaped tube has an elliptical tube, a semi-circular tube, a triangular tube, a hexagonal tube, a convex-shaped tube, a plum-shaped tube, and the like.

3.3, according to different materials, divided into ordinary carbon structural tube, low alloy structural tube, high quality carbon structural tube, alloy structural tube, stainless tube and so on.

3.4. According to special purposes, there are boiler tubes, geological tubes, oil pipes, etc.