Introduction to Tension and Roll Straightening of Titanium Rod Titanium Tube
Tension straightening is the application of a longitudinal tensile force beyond the yield limit of the workpiece to the plastic extension to achieve shape defect correction, also known as drawing straightening. At the time of straightening, the tensile stress of the titanium rod, the titanium wire, and the titanium tube, which often have wave shape defects, is applied to the tension leveler before and after the material exceeds the yield limit of the material. The tensile stress is superimposed on the original residual stress of the titanium bar. At the residual stress (ie, the wave with the original extension), a part of the tensile stress is cancelled, so that the actual deformation stress is reduced, and the plastic extension is small when straightening. At the residual tensile stress (ie, where the extension is small), the actual deformation stress increases due to the superposition of the tensile stress, and the plastic elongation is large when straightening. As a result, after the tension-straightened workpiece, the parts were evenly extended, and the wavy-shaped defects were thus obtained by eliminating the titanium tube and straightening the titanium rod on the inclined roller type straightening machine. Usually used in conjunction with pressure straightening, the workpiece with a large degree of curvature is first straightened by a pressure straightener and then straightened by a skew roll. The workpieces that need to be straightened are sent to the corresponding straightening machine, and then straightened in sequence according to the order after starting, and one straightening one by one. The straightening quality depends mainly on the straightener pressure and the roll angle. The amount of pressure depends on the type of alloy and the degree of curvature. In the case of a titanium alloy having a high strength, the straightening pressure should be larger when the degree of curvature is large, and vice versa. The size of the stick inclination depends on the diameter of the workpiece, and the workpiece with a large diameter should be larger than the small straightening angle. After the straightening is completed, the unqualified workpiece should be returned and re-straightened. Titanium tubes that cannot be straightened should be straightened by a tension straightener.
Multi-roll straightening with a number of rolls greater than 4 (usually 5 to 29 rolls) is widely used in production for simple cross-section workpieces. The working principle is to continuously repeat the three-point bending of the workpiece by each roller, thereby gradually reducing the variation range of the residual curvature of the workpiece.
The basic principles of roller straightening are:
(1) Generally, the smaller the roller diameter and the larger the number of rollers, the higher the straightening accuracy; the smaller the roller pitch value of 5 is beneficial to the biting of the workpiece and the establishment of the straightening process.
(2) The main function of the roller before straightening is to reduce the difference of the residual curvature of the workpiece along the length direction. The main function of the latter rollers is to reduce the residual curvature which tends to be uniform.
(3) The quality of the straightening quality depends mainly on the reasonable determination of the reverse bending rate of the workpiece under each roller. A large reverse bending rate is selected on the first few rolls (second and third rolls), and the reverse bending rate on the subsequent rolls is determined by exactly correcting the maximum residual curvature at the adjacent adjacent rolls.
(4) The harder the coefficient of hardening 7 is, the more difficult it is to straighten the material. In this case, a larger reverse bending rate and a larger number of straightening rolls and a smaller roll diameter are used.