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To the GB standard of steel pipes, many people in the industry know that the difference between GB/T8163 and GB9948 is not big, even close. And even if it is used, it will not be easy to detect the defects. But their difference is real, and the essential difference is the scope of application. The steel pipe of GB/T8163 is working in ordinary environment, and the application environment of GB9948 steel pipe is more complicated and more complicated. If applied improperly, it will have very serious consequences. GB/T8163-1999 Seamless steel pipe for conveying fluid: general seamless steel pipe for conveying fluid. GB9948-88 seamless steel pipe for petroleum cracking: suitable for seamless pipes of furnace tubes, heat exchanger tubes and pipelines in petroleum refineries.
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Items |
GB/T8163 Steel Pipe |
GB9948 Steel Pipe |
Marks |
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Allowable deviation of outer diameter and wall thickness
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Out diameter D＞10～30 |
Normal level |
High level |
外径≤30 |
±0.20 |
Cold drawn (rolled) tube |
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±0.40 |
±0.20 |
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Wall thickness S＞1～3 |
＋15％ |
＋12.5％ |
壁厚≤3 |
＋12％ －10％ |
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－10％ |
－10％ |
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Steel grade and chemical composition
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GB/T8163 C:0.07~0.13％ Mn: 0.35~0.65％ C:0.17~0.23％ Mn: 0.35~0.65％ |
GB9948 C:0.07~0.14％ Mn: 0.35~0.65％ C:0.17~0.24％ Mn: 0.35~0.65％ |
Carbon steel: #10
#20 |
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Delivery conditions |
Hot rolled tube in hot rolled, cold drawn (rolled) tube in heat treated state (generally annealed) |
Hot rolled tube finishing, cold drawn tube normalizing |
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Mechanical properties |
#10 |
σb=335~475MPa σs≥205MPa (s≤16) δ5≥24％ |
σb=330~490MPa σs≥205MPa δ5≥24％ |
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#20 |
σb=410~550MPa σs≥245MPa (s≤16) δ5≥20％ |
σb=410~550MPa σs≥245MPa δ5≥21％ |
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Hydrostatic test |
The pipe shall be hydraulically tested one by one, the maximum pressure shall not exceed 19 MPa, and the withstand voltage time shall not be less than5s, P=2SR/D |
The steel pipe shall be hydraulically tested one by one, the maximum pressure shall not exceed 20 MPa, and the withstand voltage shall not be less than 10 s, P=2SR/D |
Suppliers can use ultrasonic testing and eddy current testing instead of hydraulic test |
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Flattening test |
Steel pipe with outer diameter >22-400mm and wall thickness/outer diameter ≤10% |
Out diameter＞22～400mm |
No cracks are allowed on the specimen after the flattening test |
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Flaring test |
Wall thickness ≤ 8mm can be done, (the two sides agreed) |
Wall thickness≤8mm & out diameter≤159mm |
No cracks or cracks shall appear on the specimen |
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Bending test |
Out diameter ≤ 22 can be done, (the two sides agreed) |
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No cracks in the bend |
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Surface quality |
The inner and outer surfaces of the steel pipe shall not have cracks, folds, rolling, separation, crusting and hairline defects. Other defects that do not exceed the negative deviation of the wall thickness are allowed to exist. |
The inner and outer surfaces of the steel pipe shall not have cracks, folds, rolling, separation, crusting and hairline defects. Other defects that do not exceed the negative deviation of the wall thickness are allowed to exist. |
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Nondestructive testing |
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Steel pipes should be ultrasonically tested one by one |
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