Hot-rolled seamless steel pipe characteristics

In the case of hot-rolled seamless pipes, cold-rolled seamless pipes are made below the recrystallization rolling temperature, but hot-rolled seamless pipes are rolled or subjected to recrystallization temperatures.


Advantages: ingot can damage the organization, grain refinement, the elimination of tissue defects, so that the dense steel, mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer a certain degree of isotropic body, resulting in the pouring bubbles, cracks and loose, but also under high temperature and pressure welding.


Disadvantages:
1. Non-metallic inclusions (mainly sulfides and oxides, and silicates) in hot-rolled seamless steel pipes of hot-rolled steel pipe producers are pressed into plates and delaminated (laminated). Stratification in the thickness direction significantly deteriorates the tensile properties of the steel and may result in shrinkage of the interlayer tear seam. The local strain caused by welding shrinkage reaches the yield point strain, which is usually several times greater than the strain caused by the strain;


2. Residual stress caused by uneven cooling. Residual stress In the internal self-equilibrium stress without external force, there are various sections of the residual stress in hot-rolled steel, the larger the general steel cross-section size, the greater the residual stress. Although the residual stress is self-balancing, it still has some influence on the performance of steel structural members under load. Deformation, stability, fatigue and other aspects may have adverse effects.


Third, hot-rolled steel thickness and width in this area poor control. We are familiar with thermal expansion and contraction, since the beginning of the hot rolling, even if the length and thickness are standard, after the final cooling or there will be some negative difference, the negative width of the wide side, the more obvious thickness. So for large steel, steel edge width, thickness, length, angle, there is no law requires too thin edge.