Large-caliber steel pipes are mainly completed by tension reduction and continuous rolling of hollow base material without mandrel.Under the premise of ensuring the quality of the spiral steel pipe, the spiral steel pipe as a whole is heated to a high temperature above 950℃, and then rolled into seamless steel pipes of various specifications by a tension reducer.The standard-setting documents for the production of large-caliber steel pipes show that deviations are allowed in the manufacture and production of large-caliber steel pipes.：

Allowable deviation of length: The allowable deviation of the length of the steel bar when it is delivered according to the fixed ruler shall not be greater than +50mm.
Curvature and ends: The bending deformation of straight steel bars should not affect normal use, and the total curvature should not be greater than 40% of the total length of the steel bars; the ends of the steel bars should be cut straight, and the local deformation should not affect the use.

Length: Steel bars are usually delivered according to the length of a fixed ruler, and the specific delivery length should be specified in the contract; when steel bars are delivered in coils, each plate should be one steel bar, and 5% of the number of plates in each batch is allowed to be composed of two steel bars.The weight and diameter of the disk shall be negotiated and stipulated by both supply and demand.