Seamless steel pipe is classified as hot-rolled and cold-drawn seamless steel pipe.


Defects of seamless steel pipe:
1. After hot rolling, non-metallic inclusions (mainly sulfides, oxides and silicates) in steel are pressed into the plate to form layered (interlayer) phenomenon. Layering of steel significantly reduces the tensile properties of thickness and may be caused by interlayer tearing between shrinkage seams. The welding strain caused by strain contraction at yield point is usually several times larger than that caused by load.
2. Non-uniform cooling constitutes residual stress. Stress is normal stress. Without excessive stress such as external force balance of cross section of self-rolling steel, the larger the size of cross section of steel, the greater the excess stress. Although income comes from pressure balance, it is reflected in the steel body and is now subject to external forces or certain reactions. It can play a beneficial role in changing the shape, stability and fatigue resistance of seamless steel tube.
The bad side of thickness and width is dominant in hot rolled steel plate. We are familiar with thermal expansion and shrinkage. As the end of hot rolling, even if the length and thickness are standard, there will be some negative differences after final cooling. The larger the negative differences, the wider the performance is. Because steel is very large, there is no legal requirement for very precise edges for the width, thickness, length and angle of steel edges.




Advantages of seamless steel pipe:
It will damage the ingot, refine the grain size, eliminate structural defects, make the steel structure compact and deteriorate the mechanical properties. This deterioration is mainly reflected accurately along the rolling position, so a certain degree of steel is no longer isotropic, and casting bubbles, cracks and looseness are also welded together under high temperature and pressure.