Introduction to Tension and Roll Straightening of Titanium Rod Titanium Tube

- Nov 06, 2018-

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.