(1) Specifications: The specifications of spiral steel pipes should be specified in the import and export trade contract. Generally, it should include the standard grade (type code), nominal diameter of steel bars, nominal weight (mass), specified length, and allowable values of the above indicators. The Chinese standard recommends spiral steel pipe series with nominal diameters of 8, 10, 12, 16, 20, and 40mm. There are two types of supply lengths: fixed length and double length. The selection range for the length of Chinese exported rebar is 6-12m, while the selection range for the length of Japanese produced rebar is 3.5-10m.
(2) Appearance quality:
① Surface quality. The relevant standards specify the surface quality of threaded steel, requiring that the end should be cut straight, the surface should not have cracks, scars, or folds, and there should be no harmful defects in use;
② The allowable deviation of external dimensions. The requirements for the curvature of threaded steel and the geometric shape of steel bars are specified in relevant standards. According to Chinese standards, the bending degree of straight steel bars shall not exceed 6mm/m, and the total bending degree shall not exceed 0.6% of the total length of the steel bars.