51 steel pipe network provides: China's large diameter seamless steel pipe is how to define the current China's large diameter seamless steel pipe, the main production process for hot-rolled large diameter seamless steel pipe and thermal expansion of seamless steel pipe, thermal expansion seamless steel pipe for the largest specifications 1220 is 120 in thickness, thermal expansion seamless steel pipe can produce non-GB size, hot expansion seamless pipe is what we often say hot expansion pipe, the pipe with low density but strong contraction is expanded by oblique rolling method or drawing method Pipe diameter diameter of a barn finish rolling process. The thickening of steel pipes in a short period of time can produce non-standard and special models of seamless pipes with low cost and high production efficiency. It is the current trend in the field of international pipe rolling.
For GB5310 steel pipe with outer diameter greater than or equal to 76 and wall thickness ≥ 14mm, Charpy V-type longitudinal impact test shall be carried out at 20°C; the average value of impact energy of three samples shall not be lower than 40J, allowing one sample The impact energy is lower than the average but not lower than 70% of the average. Seamless steel pipe diameter> 219.1mm, and the wall thickness ≥ 25mm steel pipe can be used in place of the longitudinal mechanical properties test. The Charpy V-type transverse impact test was conducted at 20°C, and the large-diameter tube was more convenient for the transverse mechanical test.
The standard for seamless steel tubes was first released in May 1998. This standard replaces GB/T17395-1998 "Seamless steel pipe size, shape, weight and allowable deviation" This standard specifies the seamless steel pipe size, shape, weight and allowable deviation. This standard applies to the development of flat-end seamless steel pipe standards for various purposes, select the size, shape, weight and allowable deviations. Compared with GB/T17395-1998, the main changes are as follows:
--- Increased the outer diameter of ordinary steel pipes 232, 267 (267.4), 302, 318.5, 368, 419, 473, 699, 711, 720, 762, 788.5, 813, 864, 914, 965, 1016;
--- Modify the upper limit of the wall thickness of ordinary steel pipe;
--- Modify the theoretical weight per unit length;
- The wall thickness of steel pipes with an outer diameter of 25 or less is increased by 0.5, 0.6, 0.7, 0.8, or 0.9;
--- Increased full-length allowable deviation +150mm level;
--- Change the "ellipticity" to "out-of-roundness" and increase the calculation formula of "out-of-roundness";
--- usually the upper limit of the length range from the original "12000mm" to "12500mm";
--- Modify the allowable deviation of the actual weight and theoretical weight.
Because of its different manufacturing processes, seamless steel tubes are divided into hot rolled (extrusion) seamless steel tubes and cold drawn (rolled) seamless steel tubes. Cold drawn (rolled) tube is divided into two kinds of round tube and shaped tube.