How many types of steel pipes are there?
1. According to the production method, it can be divided into two categories: seamless steel pipe and seamed steel pipe. The seamed steel pipe is called straight seam steel pipe for short.
2. Steel pipes can be divided into carbon pipes, alloy pipes, stainless steel pipes, etc. according to the pipe material (ie steel type).
3. Steel pipes can be divided into two types according to the connection method of the pipe ends: plain pipe (without thread at the end of the pipe) and threaded pipe (with thread at the end of the pipe).
4. Steel pipes can be divided into black pipes (not coated) and coated pipes according to the surface coating characteristics.
5. Steel pipes can be divided into round steel pipes and special-shaped steel pipes according to the cross-sectional shape.
Specification:
(1) Specifications: The specification requirements of spiral steel pipes should be specified in the import and export trade contracts. Generally, it should include the standard grade (category code), the nominal diameter, nominal weight (mass) of the steel bar, the specified length, and the tolerance value of the above indicators. Chinese standards recommend spiral steel pipe series with nominal diameters of 8, 10, 12, 16, 20, and 40 mm. The supply length is divided into two types: fixed length and double length. The range of choice for the length of rebar exported from my country is 6-12m, and the range of choice for length of rebar made in Japan is 3.5-10m.
(2) Appearance quality:
① surface quality. Relevant standards stipulate the surface quality of rebar, which requires that the end should be cut straight, and the surface should not have cracks, scars and folds, and there should be no harmful defects in use, etc.;
②Permissible value of external dimension deviation. The requirements for the bending degree of rebar and the geometric shape of the steel bar are stipulated in the relevant standards. As stipulated in the national standard, the bending degree of straight steel bars is not more than 6mm/m, and the total bending degree is not more than 0.6% of the total length of the steel bars.
