Types of seamless steel pipes with large diameters
Seamless steel pipes with large diameters can be classified into the following types:
1. Seamless steel pipes can be divided into hot rolled pipes, cold rolled pipes, cold drawn pipes and extruded pipes according to different manufacture methods.
2. They can also be divided into round pipes and special shaped pipes. Special shaped pipes include oval pipes, semicircular pipes, triangular pipes, hexagonal pipes and convex-shaped pipes besides square and rectangular pipes according to shapes.
3. They can be classified into ordinary carbon structure pipes, low alloy structure pipes, high quality carbon structure pipes, alloy structure pipes, stainless steel pipes, etc. according to different materials.
4. There are boiler pipes, geological pipes and oil pipes based on special applications.
 
The process flow
pipe blanks-inspection-peeling-inspection-heating-perforation-pickling-grinding-lubrication and drying-welding head-cold drawing-solution treatment-pickling-pickling and passivation-inspection-cold rolling-degreasing-cutting-drying-internal polishing-external polishing-inspection-marking-finished product packaging
 
Applications

1. Seamless steel pipes can be used for construction purposes such as extracting underground water when a building is built and hot water transportation for boilers.
2. Seamless steel pipes are applied to gas transmission, water power generation fluid pipelines.
3. Seamless steel pipes are used for anti-static pipes for wind power plants.

 
How to identify inferior seamless steel pipes?
1. Inferior seamless steel pipes with large diameters are easy to be scratched, because their manufacturers have simple equipment, which can easily produce burrs and scratch the surface of the steel. Deep scratches reduce the strength of steel.
2. Inferior seamless steel pipes don't have metallic luster, showing light red or similar to pig iron.
3. Inferior seamless steel pipes have thin and low cross ribs. In order to achieve great negative tolerances, the reduction of the first few passes of the finished product is too great. The iron type is too small, and the hole type is not filled well.
4. Inferior seamless steel pipes have elliptical cross-sections. The reason is that in order to save materials, the rolling reduction of the first two passes of the finished roll is too great. The strength of such hot rolled large diameter seamless steel pipe will decrease. And it does not meet the standard of the external dimensions of hot rolled large diameter seamless steel pipes.
5. Good hot rolled large diameter seamless steel pipes have uniform composition. The tonnage of the cold shear is high, and the end surface of the cutting head is smooth and tidy. However, because of poor material, the cutting end of the hot rolled seamless steel pipe often lacks materials, that is, the cutting end is uneven and has no metallic luster.
6. Inferior seamless steel pipes contain many impurities. The density of the steel is too small, and the size is severely out of tolerance. Therefore, it can be weighed and checked when there is no vernier caliper. Generally speaking, weighing mainly considers the problems of cumulative error and probability theory.