Features and advantages and disadvantages of hot-rolled seamless pipes
The advantages of hot rolled seamless tubes are many. It can destroy the ingot's casting structure to refine the grain of the steel, and at the same time eliminate the defects of the microstructure. The mechanical properties of the steel structure are also greatly improved.
The disadvantage of the hot-rolled seamless pipe compared to other pipes is. After hot rolling, the non-metallic inclusions in the steel are pressed into thin slices and delamination occurs. Layering reduces the ability of the steel to pull in the thickness direction, and there is the possibility of interlaminar tearing as the weld seam shrinks. Welding residual stress is the internal self-phase equilibrium stress without external force. Hot rolled steel of various sections has such residual stress, and the residual stress is larger in the cross-section size.
Although the residual stress is self-balanced, it still has some influence on the performance of steel components under external forces. Such as deformation, stability, anti-fatigue and other aspects may have an adverse effect. Hot-rolled seamless pipes are not easy to control in terms of thickness and width. We are familiar with thermal expansion and contraction, because at the beginning of hot rolling, even if the length and thickness are up to standard, there will still be a certain negative difference after cooling. The thicker the thickness, the wider the width of the negative edge becomes.
The delivery length of the hot-rolled seamless pipe is specified so that the steel pipe is generally delivered in normal length. Usually the length should comply with the following provisions: hot-rolled pipe: 3000-12000mm; the length of the hot-rolled short-length pipe is not less than 2m, and the length of the cold-rolled short-length pipe is not less than one meter. The length of the cut length and length of the doubler should be within the normal length range, and the allowable full-length deviation is divided into three levels.