Straightening is divided into hot straightening and cold straightening, with hot straightening generally carried out at 650-1000 °C. Cold straightening is widely used to straighten various types of steel and steel pipes, and also used for supplementary straightening of medium and thick plates. Straightening methods are roll straightening (including straight roll straightening and inclined roll straightening), tension straightening, tensile-bend straightening, and pressure straightening.
Roll straightening is the correction of shape defects caused by repeated bending when the rolled material passes between the upper and lower rows of staggered rollers. Roll straighteners are widely used for the straightening of plates, strips and profiles, while inclined roll straighteners are used for the straightening of tubes and bars.
The straightening mainframe internal straightening method is generally divided into two types, the first is the rotary hub type rotary straightening, and the other is the parallel roller type roller straightening.
Most of the rotating straightening blocks are installed inside the rotating hub straightening mechanism, and through high-speed rotation and staggered arrangement of straightening blocks, the wire is bent several times in the process of moving forward and gradually straightens. This straightening method straightens the steel bar with good linearity and high speed, but it causes damage to the surface of the steel bar.。
Coil bars are straightened by meshing two interlocking rows of multi-wheel rollers, which directly deform the bars to be straightened. This straightening method is slightly slower than the rotary straightening equipment, but the straightness of the bar meets the requirements of construction use, and this straightening method does not hurt the bar.
Tension straightening is the correction of shape defects achieved by applying a longitudinal tensile force beyond the yield limit of the material to the rolled part to produce plastic extension, also known as tensile straightening.
It is mainly used for straightening thin plates and thin-walled pipes with thickness less than 0.6mm.
The principle of tensile-bend straightening is to straighten the strip by applying tensile force to the strip as it is repeatedly bent on a small diameter roll, which causes the strip to elastically extend. Tensile-bend straightening machines are generally used to straighten a variety of strips, including high-strength and very thin strips, on continuous lines.
Pressure straightening is generally used only as supplementary straightening for large steel and medium thick plates after roll straightening, or for straightening large steel beams, rails and large diameter steel pipes and thick plates. The main disadvantage of pressure straightening is the complexity of the operation and low productivity, so it is rarely used.