Advantages and disadvantages of precision steel tube rolling at recrystallization temperature

Precision steel tube: hot rolling is relative to cold rolling, which is rolled below the recrystallization temperature, and hot rolling is rolled above the recrystallization temperature.

Advantages of precision steel tube rolling at recrystallization temperature:

It can destroy the casting structure of steel ingot, refine the grain of steel, and eliminate the defects of microstructure, so that the microstructure of steel is compactness and mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to some extent; The bubbles, cracks and looseness formed during pouring can also be welded together under high temperature and pressure.

GPC inspector check the dimensions of the precision tube in HAIHAO

Disadvantages of precision steel tube rolling at recrystallization temperature:

1. After hot rolling, the steel internal non-metallic inclusions (mainly sulfurization and oxides, and silicates) are pressed into thin sheets, layered (sandwich) phenomenon. Lamination greatly deteriorates the tensile properties of the steel along the thickness direction, and interlaminar tearing may occur during weld shrinkage. The local strain induced by weld shrinkage is often several times of the yield point strain, which is much larger than the strain caused by load.

2. Residual stress caused by uneven cooling.The residual stress is the internal self-balancing stress under no external force action. All kinds of sections of hot rolled steel have this kind of residual stress. Generally, the larger the section size is, the larger the residual stress is.Although the residual stress is self-balancing, it still has some influence on the performance of steel members under the action of external forces. Such as deformation, stability, anti – fatigue and other aspects may have an adverse effect.

3. The thickness and side width of hot-rolled steel products are not well controlled.We are familiar with thermal expansion and cold contraction. At the beginning, even if the length and thickness are up to the standard after hot rolling, there will still be a certain negative difference after cooling. The wider the side width is, the thicker the thickness is, the more obvious it is.So for large steel, for the steel side width, thickness, length, Angle, and edge line can not be too precise.