Specifications and appearance quality of steel pipes

(1) Specifications: The specifications of spiral steel pipes should be stated in the import and export trade contract. Generally, it should include the standard grade (type code), the nominal diameter of the steel bar, the nominal weight (mass), the specified length and the tolerance value of the above indicators, etc. Chinese standards recommend spiral steel pipe series with nominal diameters of 8, 10, 12, 16, 20, and 40mm. The length of supply is divided into two types: fixed length and double length. The fixed length selection range of rebar exported from China is 6~12m, and the fixed length selection range of rebar produced in Japan is 3.5~10m.
(2) Appearance quality:
① Surface quality. Relevant standards stipulate the surface quality of rebar, requiring that the ends should be cut straight, the surface should be free of cracks, scars, folds, and defects harmful to use.
② Allowable value of overall dimension deviation. The requirements for the curvature of rebar and the geometry of steel bars are stipulated in relevant standards. As stipulated by Chinese standards, the curvature of straight steel bars shall not be greater than 6mm/m, and the total curvature shall not be greater than 0.6% of the total length of the steel bars.