Analysis of Defects in Titanium Sheet with Cold Rolling Process

Cold rolled titanium plate titanium belt in the roll into the volume, the cool surface of the surface of the local uplift, called the tendons. For the pure titanium belt, from the tendons occurred in the thickness of less than 0.8mm specifications, the main form of single-based. The direct consequence of the tendons is the addition of waves to the strip, which affects the plate and surface quality, resulting in degradation of the product, severe and even shear, sub-volume processing. Not only reduces the quality of the product, but also cause waste of raw materials, reducing production efficiency. Rolling test found that the same specifications of different batches of hot-rolled coil after cold rolling from the tendons and tendons with discrete probability, indicating that the hot-rolled raw material itself has a greater impact on the cold-rolled tendons. In the hot rolling, the existence of abrasions, sickle bending, cracks and other defects, the subsequent cold rolling process in the emergence of a variety of defects has a certain impact. Hot-rolled local high point on the impact of cold-rolled strip is limited to high and near a small area, but for very thin strip, enough to cause the strip uplift "up tendons" and even the formation of local waves and uplift Disjointed serious quality defects.

At present, the production of pure titanium plate is mainly used in six rolls, ten roller and twenty rolls and other rolling mill rolling. In the titanium plate with the most advanced production technology in Japan using 20 roll mill rolling, thickness 0.3 ~ 3mm, high production efficiency, dimensional accuracy, shape, the surface quality is very good. However, in the actual production process, especially in the large volume of thick and thin strip production process, there are still from the tendons, waves and other quality problems. Among them, to the most serious reinforcement, to the quality of the product and the benefits of the enterprise has brought adverse effects, is to be solved product quality problems. By means of the same tension of different plate shape curves and the same tension of the same plate shape curve, etc., in the same tension under different plate-shaped curve setting conditions, when the plate-shaped curve with reference to stainless steel strip set, the tendons The probability is high, the plate-shaped curve is set to adjust the test after rolling, the probability of the tendons and tendons from the sharp decline. Under the condition of different tension setting under the same plate-shaped curve, the probability of considerable tension rolling is higher than that of large tension rolling, but there is no obvious difference between the tendon and the amount of tendons. The result shows that the traditional stainless steel strip large tension rolling are not suitable for rolling of pure titanium strip. Through the analysis of the above test results, the uplift of the tendons is a consequence of the joint action of plate shape control and tension control. From the mechanical point of view, the reinforcement is an axial force the result of.

Based on the field test and the theoretical analysis, the mathematical model of the critical condition of the reinforcement is established according to the characteristics of the actual production. The acute stress of the buckling instability is proportional to the quadratic power of the strip thickness, which is inversely proportional to the square of the width. At the same time, the axial stress is affected by the tension of the anterior tension, the friction coefficient and the aspect ratio. Under the premise of constant width and thickness ratio, by changing the pre-tension, changing the rolling lubricating oil. to increase the friction and other means can effectively inhibit the occurrence of tendon defects.

Although the rolling speed of the titanium strip is very slow, if the sizing degree of the lubricating fluid is poor or the nozzle is clogged, the unevenness of the lubrication will result in uneven distribution of the stress in the deformation zone. In the rolling deformation zone, the neutral component of the axial component of the axial force, this component may be very small, but for the plate to the center of the tightening has a certain impact. In the process of rolling deformation, the local extreme point or local hardness will lead to uneven distribution of stress in the deformation zone and produce axial component force. When the vibration of the device interacts with the unbalanced tension, the axial component force will be generated. The superposition effect of the center will be generated when the center is trivial, the unevenness of the thickness and the deviation between the layers.