Steel pipes are divided into circular, square, rectangular and special-shaped steel pipes according to their cross-sectional shapes; According to the material, it is divided into carbon structural steel pipe, low alloy structural steel pipe, alloy steel pipe and composite steel pipe. According to the purpose, it is divided into steel pipes for pipelines, engineering structures, thermal equipment, petrochemical industry, machinery manufacturing, geological drilling and high-voltage equipment. According to the production process, it is divided into seamless steel pipe and welded steel pipe, in which seamless steel pipe is divided into hot rolling and cold rolling.
Extended information:
The elements of steel pipe are:
1. deviation
In the production process, the actual size is difficult to meet the requirements of the nominal size, that is, it is often larger or smaller than the nominal size, so there is a difference between the actual size and the nominal size specified in the standard. Positive difference is called positive deviation and negative difference is called negative deviation.
2. Delivery length
The delivery length is also called the length required by the user or the contract length. Universal length (also called non-fixed length): Any length without fixed length requirement within the length range specified by the standard is called universal length.
3. Ellipticity
The cross section of circular steel pipe has the phenomenon of unequal outer diameters, that is, there are maximum and minimum outer diameters that are not necessarily perpendicular to each other, and the difference between the maximum and minimum outer diameters is ellipticity (or roundness). In order to control ellipticity, some steel pipe standards stipulate the allowable index of ellipticity, which generally does not exceed 80% of the outer diameter tolerance.