(1) specifications: the specifications of spiral steel pipe should be listed in the import and export trade contract. Generally should include the standard grade (type code), the nominal diameter of steel, nominal weight (quality), the length of the specifications and the allowable difference between the above indicators. China's standard recommended nominal diameter of 8, 10, 12, 16, 20, 40mm spiral steel pipe series. The supply length is divided into two kinds: foot length and foot length. The selection length of export screw steel in China is from 6 to 12M, and the selection length of Japanese thread steel is 3.5 ~ 10m.
(2) appearance quality: surface quality. On the steel surface quality standard stipulates the requirements ends shall be cut straight, the surface shall not have cracks, scarring and folding, there shall be no use of harmful defects; the size deviation allowable value. The requirements for the bending of the thread steel and the geometry of the steel bar are specified in the relevant standards. As our standard stipulates, the bending of bars is not greater than 6mm/m, the total bending is not greater than 0.6% of the total length of the reinforcement.