Seamless steel pipe is a steel pipe without welds made by hot processing methods such as perforation hot rolling. If necessary, the hot-processed pipe can be further cold-processed to the required shape, size, and performance. At present, seamless steel pipe (DN15-600) is the most widely used pipe in petrochemical production equipment.
(I) Carbon steel seamless steel pipe
Material grades: 10#, 20#, 09MnV, 16Mn, a total of 4 types
Standards:
GB8163 “Seamless steel pipe for fluid transportation”
GB/T9711 “Technical conditions for delivery of steel pipes for petroleum and natural gas industry”
GB6479 “High-pressure seamless steel pipe for fertilizer equipment”
GB9948 “Seamless steel pipe for petroleum cracking”
GB3087 “Seamless steel pipe for low and medium pressure boilers”
GB/T5310 “Seamless steel pipe for high-pressure boilers”
GB/T8163: Material grades: 10#, 20#, Q345, etc. Scope of application: oil products, oil and gas, and public medium with design temperature less than 350℃ and pressure less than 10MPa.
GB6479: Material grades: 10#, 20G, 16Mn, etc. Scope of application: oil products, oil, and gas with a design temperature of -40～400℃ and design pressure of 10.0～32.0MPa.
GB9948: Material grades: 10#, 20#, etc. Scope of application: occasions where GB/T8163 steel pipes are not suitable.
GB3087: Material grades: 10#, 20#, etc. Scope of application: superheated steam, boiling water, etc. of low and medium-pressure boilers.
GB5310: Material grades: 20G, etc. Scope of application: superheated steam medium of high-pressure boilers
Inspection: general fluid transportation steel pipes must undergo chemical composition analysis, tensile test, flattening test, and water pressure test. In addition to the tests that must be conducted on steel pipes for fluid transportation, steel pipes of GB5310, GB6479, and GB9948 standards also require expansion tests and impact tests; the manufacturing inspection requirements for these three steel pipes are relatively strict. GB6479 standard also makes special requirements for the low-temperature impact toughness of materials. In addition to the general test requirements for steel pipes for fluid transportation, steel pipes of GB3087 standard also require cold bending tests. In addition to the general test requirements for steel pipes for fluid transportation, steel pipes of GB/T8163 standard require expansion tests and cold bending tests according to the agreement. The manufacturing requirements of these two pipes are not as strict as the first three.
Manufacturing: Steel pipes of GB/T8163 and GB3087 standards are mostly smelted in open furnaces or converters, and their impurity components and internal defects are relatively high. GB9948 is mostly smelted in electric furnaces. Most of them have added refining processes outside the furnace, and the components and internal defects are relatively low. GB6479 and GB5310 standards themselves specify the requirements for refining outside the furnace, with the least impurities and internal defects and the highest material quality.
The manufacturing quality levels of the above steel pipe standards are in the order from low to high: GB/T8163<GB3087<GB9948<GB5310<GB6479
Selection: In general, steel pipes of GB/T8163 standard are suitable for oil products, oil and gas and public medium conditions with a design temperature of less than 350℃ and a pressure of less than 10.0MPa; for oil products and oil and gas media, when the design temperature exceeds 350℃ or the pressure is greater than 10.0MPa, steel pipes of GB9948 or GB6479 standard should be selected; for pipelines operating in the presence of hydrogen or working in an environment with a tendency to stress corrosion, GB9948 or GB6479 standard should also be used. All carbon steel pipes used at low temperatures (less than -20℃) should adopt the GB6479 standard, which is the only one that specifies the requirements for low-temperature impact toughness of materials. GB3087 and GB5310 are standards specifically set for boiler steel pipes. The Boiler Safety Supervision Regulations emphasize that all pipes connected to the boiler are subject to supervision, and the application of their materials and standards should comply with the provisions of the Boiler Safety Supervision Regulations. Therefore, the public steam pipes (supplied by the system) used in boilers, power stations, heating, and petrochemical production equipment should adopt GB3087 or GB5310 standards. It is worth noting that the price of steel pipes with good quality standards is also relatively high. For example, the price of GB9948 is nearly 1/5 higher than that of GB8163 materials. Therefore, when selecting steel pipe material standards, comprehensive considerations should be made based on the use conditions, and both reliability and economy should be considered. It should also be noted that according to GB/T20801 and TSGD0001, steel pipes of GB3087 and GB8163 standards shall not be used for GC1 pipelines (unless each pipe is ultrasonically tested and the quality is not less than L2.5 level, it can be used for GC1(1) pipelines with a design pressure of no more than 4.0Mpa).
(II) Low alloy steel seamless steel pipe
In petrochemical production equipment, the commonly used chromium-molybdenum steel and chromium-molybdenum-vanadium steel seamless steel pipe standards are GB9948 “Seamless steel pipe for petroleum cracking” GB6479 “High-pressure seamless steel pipe for fertilizer equipment” GB/T5310 “Seamless steel pipe for high-pressure boiler” The chromium-molybdenum steel material grades included in GB9948 are 12CrMo, 15CrMo, 1Cr2Mo, 1Cr5Mo, etc. The chromium-molybdenum steel material grades included in GB6479 are 12CrMo, 15CrMo, 1Cr5Mo, etc. The chromium-molybdenum steel and chromium-molybdenum-vanadium steel material grades included in GB/T5310 are: 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12Cr1MoVG, etc. Among them, GB9948 is more commonly used, and the selection conditions are as above.
(III) Stainless steel seamless pipes
Common stainless steel seamless pipe standards include GB/T14976, GB13296, GB9948, GB6479, and GB5310, a total of five standards. Among them, the last three standards only list two or three stainless steel material grades, and they are uncommon material grades. Therefore, when stainless steel seamless pipe standards are selected in engineering, GB/T14976 and GB13296 standards are selected.
GB/T14976 “Stainless steel seamless pipes for fluid transportation”: Material grades: 304, 304L, etc., a total of 19 types suitable for general fluid transportation.
GB13296 “Stainless steel seamless pipes for boilers and heat exchangers”: Material grades: 304, 304L, etc., a total of 25 types.
Among them, ultra-low carbon stainless steel (304L, 316L) has excellent corrosion resistance. Under certain conditions, it can replace stable stainless steel (321, 347) to resist medium corrosion; ultra-low carbon stainless steel has low high-temperature mechanical properties and is generally only used under conditions below 525°C; stable austenitic stainless steel has both good corrosion resistance and high high-temperature mechanical properties, but the Ti in 321 is easily oxidized and lost during welding, thereby reducing its corrosion resistance and its price is relatively high. This type of material is generally used on more important occasions. 304 and 316 have general corrosion resistance and are cheap, so they are widely used.
Post time: Oct-30-2024