A brief discussion on the proper selection of seamless steel pipes
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Seamless steel pipes are steel pipes without welds, manufactured using hot processing methods such as piercing and hot rolling. If necessary, the heat-treated tubes can be further cold-worked to achieve the desired shape, size, and properties. Currently, seamless steel pipes (DN15–600) are the most widely used pipes in petrochemical production facilities. (1) Carbon steel seamless pipes: Material grades include 10, 20, 09MnV, and 16Mn – a total of 4 grades. Standards applicable: GB8163 \"Seamless pipes for fluid transport\", GB/T9711 \"Technical requirements for pipes used in the oil and gas industry\", GB6479 \"High-pressure seamless pipes for fertilizer equipment\", GB9948 \"Seamless pipes for petroleum cracking\", GB3087 \"Seamless pipes for low- and medium-pressure boilers\", GB/T5310 \"Seamless pipes for high-pressure boilers\". GB/T8163: Material grades include 10, 20, Q345, etc. Application range: Oils, oil-gases, and utility media with a design temperature of less than 350°C and a pressure of below 10 MPa. GB6479: Material grades: 10, 20G, 16Mn, etc. Application range: Oil and gas with a design temperature of –40 to 400°C and a design pressure of 10.0 to 32.0 MPa; standard GB9948: Material grades: 10, 20, etc. Application scope: Situations where GB/T8163 steel pipes are not suitable. GB3087: Material grades: 10, 20, etc. Application range: superheated steam, boiling water, etc. in low and medium pressure boilers. GB5310: Material grade: 20G, etc. Application range: Superheated steam medium in high-pressure boilers. Inspection: Steel pipes used for general fluid transportation must undergo chemical composition analysis, tensile testing, flattening testing, and hydrostatic testing. For steel pipes governed by the GB5310, GB6479, and GB9948 standards, in addition to the tests required for pipes used in fluid transportation, flaring tests and impact tests are also mandated ； The manufacturing and inspection requirements for these three types of steel pipes are quite strict. Standard GB6479 also sets specific requirements for the low-temperature impact toughness of materials. For steel pipes in accordance with GB3087 standard, in addition to the general test requirements for steel pipes used in fluid transportation, a cold bending test is also required. For steel pipes in accordance with the GB/T8163 standard, in addition to the general test requirements for steel pipes used in fluid transportation, flaring tests and cold bending tests are carried out as specified by the agreement. The manufacturing requirements for these two types of pipes are not as strict as those for the first three types. Manufacturing: Steel pipes in accordance with GB/T/8163 and GB3087 standards are often produced through open-hearth or converter smelting, resulting in relatively higher levels of impurities and internal defects. GB9948 is mostly smelted using electric furnaces. Most have adopted the secondary refining process, resulting in relatively fewer compositional impurities and internal defects. The GB6479 and GB5310 standards specify the requirements for off-ferrous refining, resulting in the lowest levels of impurities and internal defects as well as the highest quality of material. The manufacturing quality grades of the aforementioned steel pipe standards, from lowest to highest: GB/T8163
When selecting seamless steel pipes, it is first necessary to choose the appropriate material grade and standard based on the operating environment and load requirements. If high pressure or high temperature must be withstood, steel pipes for high-pressure boilers specified in GB5310 or high-pressure seamless steel pipes for fertilizer equipment specified in GB6479 should be selected. For general fluid transportation, seamless steel pipes in accordance with GB8163 standard can be selected. At the same time, the manufacturing methods and inspection requirements for steel pipes must also be considered to ensure that their quality and performance meet the needs of the project. .
The post shared by the original author is very detailed. However, I have a few personal opinions that I’d like to share and discuss with friends: 1. Carbon steel doesn’t quite align with the subsequent standards; was this based on the relevant standards for pressure vessels? In the current standards, 09MnV and 16Mn have either been removed or modified…… 2. The national standard has been changed from a mandatory standard to a recommended standard, i.e., GB/T“” ； 3. It’s not only GB/T 6479 that has low-temperature performance; this property is primarily related to the characteristics of the material itself. For example, GB/T 8162 and GB/T 8163 apply to Q345D material, while GB/T 18984 applies to 16MnDG material, and so on ； Of course, in the chemical industry, the GB/T 6479 standards for materials such as Q345D and Q345E are those that are used most frequently. Therefore, I believe that the statement you made, “anything below -20°C…” is not precise.