Large diameter seamless steel pipe

      At present, China's large-diameter seamless steel pipe, the main production process is hot-rolled large-diameter seamless steel pipe and heat-expanded seamless steel pipe, thermal expansion of seamless steel pipe can produce non-national standard size, thermal expansion seamless pipe is what we often say Expanding pipe, a low-density steel pipe with a very low density but a very large shrinkage process is a rough pipe finishing process in which the diameter of the pipe is expanded by a cross-rolling method or a drawing method. In a relatively short period of time, the steel pipe is thickened, and non-standard, special-type seamless pipes can be produced, and the cost is low and the production efficiency is high, which is the development trend of the international rolling pipe field. 

　 GB5310 shall specify a steel pipe with an outer diameter greater than or equal to 76 and a wall thickness of ≥14 mm. The Charpy V-type longitudinal impact test shall be carried out at 20 °C; the average value of the impact energy of the three samples shall not be less than 40 J, allowing one sample. The impact energy is below the average but not below 70% of the average. 

  The outer diameter of the seamless steel pipe>219.1mm, and the steel pipe with wall thickness ≥25mm can be replaced by the transverse mechanical property test instead of the longitudinal mechanical property test. Charpy V-type transverse impact test is carried out at 20 °C, and it is convenient to test the transverse mechanical properties of large-diameter pipes. 
　　The seamless steel pipe standard was first released in May 1998. This standard replaces GB/T17395-1998 "Seamless steel pipe size, shape, weight and tolerance" This standard specifies the size, shape, weight and tolerance of seamless steel pipe. This standard is applicable to the selection of dimensions, shape, weight and allowable deviation when formulating flat end seamless steel pipe standards for various purposes. Compared with GB/T17395-1998, the main changes of this standard are as follows: 
　　———The outer diameter of ordinary steel pipe is increased by 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 thickness of ordinary 
　　steel; --- modified tables 1 theoretical weight per unit length of 
　

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　2; --- table 3 The wall thickness of the steel pipe with the outer diameter of 25 or less is increased by 0.5, 0.6, 0.7, 0.8, 0.9; 　　--- The total length tolerance is increased by +150 
mm;
　　--- the "ovality" with "roundness", increasing the "roundness" of the calculation 
　　formula; --- upper limit is generally the length of the original "12000mm" to 
　　"12500mm"; --- The allowable deviation specification of the actual weight and the theoretical weight was modified. 
　　Seamless steel tubes are divided into hot-rolled (extruded) seamless steel tubes and cold drawn (rolled) seamless steel tubes due to their different manufacturing processes. Cold drawn (rolled) tubes are divided into two types: round tubes and shaped tubes. Seamless steel pipe implementation standard　　
         1, seamless steel pipe for structure: GB8162-2008 
　　2. Ground seam steel pipe for conveying fluid: GB8163-20083 
　　3. Seamless steel pipe for low and medium pressure boiler tube boiler: GB3087-2008 
　　4. High pressure seamless for boiler Pipe: GB5310-2008 (ST45.8-III type) 
　　5. High-pressure seamless steel pipe for fertilizer equipment: GB6479-1999 
　　6. Seamless steel pipe for geological drilling : YB235-70 
　　7. Seamless steel pipe for oil drilling: YB528-65 
　　8. Seamless steel pipe for petroleum cracking: GB9948-88 
　　9. Special seamless pipe for oil drill collar: YB691-70 
　　10. Seamless steel pipe for automobile semi-axle: GB3088-1999 
　　11. Seamless steel pipe for ships: GB5312-1999 
　　12 , cold drawn cold rolled precision seamless steel pipe: GB3639-1999 
　　13, various alloy tubes 16Mn, 27SiMn, 15CrMo, 35CrMo, 12CrMov, 20G, 40Cr, 12Cr1MoV, 15CrMo　
　　In addition, there are GB/T17396-1998 (hot rolled seamless steel pipe for hydraulic props), GB3093-1986 (high pressure seamless steel pipe for diesel engine), GB/T3639-1983 (cold drawn or cold rolled precision seamless steel pipe), GB /T3094-1986 (cold drawn seamless steel pipe shaped steel pipe), GB/T8713-1988 (precision inner diameter seamless steel pipe for hydraulic and pneumatic cylinders), GB13296-1991 (stainless steel seamless steel pipe for boilers and heat exchangers), GB/T14975 -1994 (stainless steel seamless steel pipe for structure), GB/T14976-1994 (stainless steel seamless pipe for fluid transportation) GB/T5035-1993 (seamless steel pipe for automobile semi-axle casing), API SPEC5CT-1999 (casing and oil pipe) Specification) and so on.

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