Seamless Steel Pipe Wall Thickness Tolerance

Take the seamless steel pipe as an example, pipe wall thickness tolerance affect the quality. Pay attention to this, you will get a better pipe. As ASTM A106 and ASTM A530 standards:
The wall thickness at any point should be within the following tolerance table.

NPS/ DN/ OD Permissible Variations in Outside Diameter
Over Under
in. mm in. mm
NPS 1/8 to 1½, incl
DN 6 to 40
OD 10.3 to 48.3, mm
1/64 0.4 1/64 0.4
Over 1½ to 4, incl
DN 40 to 100
OD 48.3 to 114.3, mm
1/32 0.8 1/32 0.8
Over 4 to 8, incl
DN 100 to 200
OD 114.3 to 219.1, mm
1/16 1.6 1/32 0.8
Over 8 to 18, incl
DN 200 to 450
OD 219.1 to 457, mm
3/32 2.4 1/32 0.8
Over 18 to 26, incl
DN 450 to 650
OD 457 to 660, mm
1/8 3.2 1/32 0.8

According to the production method, seamless pipes are divided into hot rolled pipes, cold rolled pipes, cold drawn pipes, extruded pipes, jacking pipes, etc. The maximum diameter is 650mm and the minimum diameter is 0.3mm. Depending on the application, there are thick-walled tubes and thin-walled tubes. Seamless steel tubes are mainly used as petroleum geological drilling tubes, cracking tubes for petrochemical industry, boiler tubes, bearing tubes, and high-precision structural steel tubes for automobiles, tractors, and aviation. In the plate, Q345B seamless steel pipe belongs to low alloy series. 

Among the low alloy materials, this kind of material is the most common. The outer diameter of hot-rolled seamless pipe is generally greater than 32mm, the wall thickness is 2.5-200mm, the outer diameter of cold-rolled seamless steel pipe can be 6mm, the wall thickness can be 0.25mm, the outer diameter of thin-walled pipe can be 5mm, and the wall thickness is less than 0.25mm, cold rolling has higher dimensional accuracy than hot rolling.

Note: seamless and welded pipe: The difference in the basic manufacturing method is obvious from the names. Seamless tube is extruded and drawn from a billet while welded tube is produced from a strip that is roll formed and welded to produce a tube


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