Seamless steel pipe classification and characteristics

Seamless steel tube classification is hot-rolled cold drawn seamless steel pipe.


The shortcomings of seamless steel pipe:
1. After hot rolling, non-metallic inclusions (mainly sulfides, oxides and silicates) in the steel are pressed into the sheet to form a layered (sandwich) phenomenon. Stratification of the steel significantly degrades the tensile properties of the thickness and may result from interlayer tears between the shrinkage of the weld. Weld strain caused by the yield point strain shrinkage is often several times larger than the load induced strain;
2. Uneven cooling constitutes residual stress. Stress is the normal stress without external force balance of self-rolling steel cross-section such an excess stress, the greater the size of the steel cross-section, the greater the excess stress. Although the income from the pressure balance, but manifested in the steel body, now subjected to external forces or a certain response. For the change of seamless steel pipe shape, stability, anti-fatigue, etc. can play a beneficial role.
Hot rolled steel, the thickness and width of the bad side to dominate. We are familiar with thermal expansion and contraction, as the end of the hot rolling even if the length and thickness are standard, after the final cooling or there will be some negative differences, the negative difference is bigger, the wider the more obvious performance. Because steel is large, there is no legal requirement for very precise edges for the width, thickness, length, angle of the steel edge.


The advantages of seamless steel pipe:
It can damage the ingot, refine the grain, eliminate the defects of the structure, make the steel structure dense and the mechanical property deteriorate. This deterioration is mainly accurately reflected along the rolling position, so that a certain degree of steel is no longer isotropic, and the cast-in bubbles, cracks and looseness are also welded together under high temperature and pressure.