Dimensional specifications of structural seamless tubes and allowable deviations of outer diameter a

Structure with a seamless sizes of 
Name Value 
outer diameter and wall thickness should be consistent with GB / T17395 <seamless steel pipe > predetermined 
length 1. The hot rolling (extrusion, expansion) steel pipe 3 ~ 12m2. Drawing (bar) Steel 2~10.5m 
bending degree 1. When the wall thickness is ≤15mm, it shall not be greater than 1.5mm/m2. When the wall thickness is >15~30mm, it shall not be greater than 2.0mm/m3. When the wall thickness is >30mm or the external wall is ≥351mm, it shall not be greater than 3.0mm/ m 
diameter and wall thickness of the kind of steel pipe size tolerances allowable deviation 
ordinary advanced stage 
hot rolling (extrusion, pressing) the tube outer diameter D <50 ± 0.50 mm ± 0.40mm 
≧ 50. 1% ± 0.75% ± 
wall thickness of <4 ± 12.5 % (minimum ± 0.40mm) ± 10 % (minimum ± 0.30mm) 
≥ 4~20 +15%-12.5% ± 10 % 
>20 ± 12.5% ± 10% 
cold drawn (rolled) tube outer diameter 6~10 ± 0.20 mm ± 0.10 mm 
>10~30 ± 0.40 mm ± 0.20 mm 
 >30~50 ± 0.45 mm ± 0.25 mm 
>50 ± 1 % ± 0.5 % 
Wall thickness ≤1 ± 0.15 mm ± 0.12 mm 
>1~ 3 + 15 %, - 10 % ± 10 % 
>3 + 12.5, - 10 % ± 10 %


Note: For thermal expansion tubes with an outer diameter of not less than 351 mm, the allowable deviation is ± 18 % afterwards.