Advantages and Disadvantages of Hot Rolled Seamless Steel Pipe

Compared with the cold rolling, the cold rolling is lower than the rolling recrystallization temperature, and the hot rolling is carried out at a higher recrystallization temperature.



Advantage:

Hot rolling seamless steel tube can destroy the casting structure of ingot, refine the grain of steel, eliminate the defects of structure, make the steel structure compact and improve the mechanical properties. This improvement is reflected in the rolling direction, so the steel is no longer isotropic to some extent. Bubbles, cracks and osteoporosis formed by pouring under high temperature and pressure can also be welded together.


Disadvantages:


1. After hot rolling, the non-metallic inclusions (mainly sulfides, oxides and silicates) inside the steel are pressed into pieces, and delamination (lamination) occurs. As a result of tensile properties, the delamination of the steel in the thickness direction is significantly deteriorated, and may occur in the welding shrinkage interlaminar tear. The local strain caused by welding shrinkage is often several times of the yield point strain, which is much larger than the load caused;


2. The thickness and edge width of hot rolled steel products are poorly controlled. We are familiar with thermal expansion and contraction. Even if the start of hot rolling is standard length and thickness, there will be some negative final thickness after cooling. The wider the negative differential edge width, the better the thickness performance. More obvious. Therefore, for large steel, the width, thickness, length, angle and sideline of the steel do not need to be too precise


3. Residual stress caused by uneven cooling. The residual stress is the internal self-equilibrium stress without external force. All kinds of hot-rolled steel sections have residual stress, so the larger the section size is, the greater the residual stress is. The residual stress is self-equilibrium, but the performance of steel members is affected by external forces. Such as deformation, stability, fatigue resistance may be adversely affected.