热轧无缝管是相对于冷轧无缝管而言的，冷轧无缝管是在再结晶温度以下进行的

Cold rolling the hot-rolled seamless tube with respect to the terms seamless, cold-rolled seamless tube is carried out at a temperature below the recrystallization rolling, and rolling the hot rolled seamless is performed above the recrystallization temperature. <br>Advantages: can destroy the cast structure of steel ingot, steel grain refinement of the microstructure and eliminate defects, so that the steel organization compacting, mechanical properties improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer certain extent isotropic body; bubbles, cracks and loose formed during casting, it may be welded together at an elevated temperature and pressure. <br>Disadvantages: 1. After hot rolling, the steel inside the non-metallic inclusions (mainly sulfides and oxides, and silicates) was pressed into a sheet, delamination (interlayer) phenomenon. The steel material layered in the thickness direction of the tensile performance deteriorated significantly, and may occur when the interlayer tear weld shrinkage. Inducing local strain weld shrinkage often amounting to several times the yield strain, the strain is much greater than loading induced; <br>residual stresses caused by uneven cooling 2. Residual stresses in the absence of an external force from the internal equilibrium stress, hot-rolled steel have various cross-sections such residual stresses, the greater cross-sectional dimension generally steel, the residual stress increases. While the residual stress is self-balanced, but the performance of the steel member by an external force or a certain influence. The deformation aspects, stability, anti-fatigue effects may adversely. <br>3. The hot-rolled steel products, the thickness in this area and poor edge width control. We are familiar with thermal expansion and contraction, due to the beginning of the hot rolling out even length, are standard thickness, and finally cooled or there will be some negative difference, this negative edge width, the wider the difference, the more clearly the thicker performance. So for large steel for steel edge width, thickness, length, angle, and no method requires very precise edges.

Hot-rolled seamless tube is relative to cold-rolled seamless tube, cold-rolled seamless tube is rolled below the recrystallization temperature, and hot-rolled seamless tube is rolled above the recrystallization temperature. <br>Advantages: Can destroy the casting of ingots, refine the grain of steel, and eliminate the defects of micro-tissue, so that the steel organization is compact, the mechanical performance is improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer anisotropic to a certain extent, the bubbles, cracks and looseness formed during pouring, can also be welded under high temperature and pressure. <br>Disadvantages: 1. After hot rolling, non-metallic inclusions (mainly sulphides and oxides, as well as silicates) inside the steel are pressed into thin sheets, resulting in layered (mezzanine) phenomena. The layering significantly worsens the performance of the steel being pulled in the thickness direction and may cause interlayer tearing as the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by load. <br>2. Residual stress caused by uneven cooling. Residual stress is the stress of internal self-phase balance without external force, and hot-rolled steel solders in various cross-sections have such residual stress, and the larger the size of the general steel section, the greater the residual stress. Although the residual stress is self-phase balanced, it still has some effect on the performance of steel components under external force. Such as deformation, stability, anti-fatigue and other aspects may have adverse effects. <br>3. Hot-rolled steel products, for thickness and edge width in this aspect is not good control. We are familiar with hot expansion and cold shrinkage, because at the beginning of hot rolling out even if the length, thickness are up to standard, the final cooling will appear a certain negative difference, this negative difference edge wider, thicker the expression of the more obvious. So for large steel, the edge width, thickness, length, angle, and edge of the steel can not be required to be too precise.

Compared with the cold rolled seamless pipe, the hot rolled seamless pipe is rolled under the recrystallization temperature, and the hot rolled seamless pipe is rolled above the recrystallization temperature.<br>Advantages: it can destroy the casting structure of the ingot, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel structure is dense and the 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 under the action of high temperature and pressure.<br>Disadvantages: 1. After hot rolling, the non-metallic inclusions (mainly sulfide and oxide, as well as silicate) inside the steel are pressed into thin sheets, resulting in delamination (interlayer). Delamination makes the tensile properties of the steel along the thickness direction deteriorate greatly, and it is possible that the interlaminar tear occurs when the weld shrinks. The local strain induced by weld shrinkage is often several times of the yield point strain, which is much larger than that caused by load;<br>2. Residual stress caused by uneven cooling. The residual stress is the internal self-equilibrium stress without external force, which exists in all kinds of hot-rolled sections. The larger the section size of general section, the greater the residual stress. Although the residual stress is self-equilibrium, it has a certain influence on the performance of steel members under external force. Such as deformation, stability, anti fatigue and other aspects may have adverse effects.<br>3. The thickness and edge width of hot rolled steel products are not well controlled. We are familiar with thermal expansion and cold shrinkage. Even if the length and thickness of hot rolling are up to standard at the beginning, there will be a certain negative difference after cooling. The wider the negative difference is, the thicker the thickness is. Therefore, for large-scale steel, the edge width, thickness, length, angle and edge line of steel cannot be too precise.<br>