After the cold-rolled titanium sheet and titanium strip are coiled into coils, the circumferential local bulge on the surface of the coil is called ribbing. For pure titanium strips, tendons mostly occur in specifications with a thickness less than 0.8mm, and most of the manifestations are single ribs. The direct result of ribbing is that the strip will produce additional waves, which will affect the shape and surface quality of the strip, resulting in product degradation. In severe cases, it will even be cut and divided into coils. It not only reduces the quality of the product, but also causes waste of raw materials and reduces production efficiency. The rolling test found that different batches of hot-rolled coils with the same specifications have different ribbing amounts and ribbing probabilities after cold rolling, indicating that the hot-rolled raw materials themselves have a greater impact on cold-rolled ribbing. In the hot-rolled incoming materials, defects such as scratches, cambers, and cracks are common, which have a certain impact on the generation of various defects in the subsequent cold-rolling process. Although the influence of the local high point of the hot-rolled incoming material on the cold-rolled strip is limited to the high point and a small range nearby, it is enough to cause the local uplift of the strip to "bead" or even form local waves and uplifts for extremely thin strips. Serious quality defects intertwined.
At present, the production of pure titanium plate and strip is mainly rolled by other multi-roll mills such as six-roll, ten-roll and twenty-roll. In Japan, where the production technology of titanium strips is the most advanced, 20-high rolling mills are used for rolling, with a thickness of 0.3-3mm. The production efficiency is high, and the dimensional accuracy, shape, and surface quality are very good. However, in the actual production process, especially in the production process of large-volume heavy and wide-width thin strips, there are still quality problems such as ribbing and wave shape. Among them, ribbing is the most serious, which has a negative impact on the quality of products and the benefits of enterprises, and is a product quality problem that needs to be solved urgently. Through the trial rolling of the same tension of different shape curves and different tensions of the same shape curve, it is found that under the same tension and different shape curve settings, when the shape curve is set with reference to the stainless steel strip, the ribbing The probability is high, and the strip shape curve is set to be adjusted for trial rolling, and the probability of ribbing and the amount of ribbing are greatly reduced.Under the conditions of the same shape curve and different tension setting conditions, the probability of ribbing in rolling with large tension and rolling with small tension is high, but the difference between the probability of ribbing and the amount of ribbing in rolling with large and small tensions is not obvious. From this we know that the traditional stainless steel strip High tension rolling is not suitable for rolling pure titanium strip. Through the analysis of the above test rolling results, the circumferential uplift of ribbing is the result of the joint action of various factors such as strip shape control and tension control. From a mechanical point of view, ribbing is a kind of axial force. the result of.
On the basis of field test and theoretical analysis, the mathematical model of the critical condition of ribbing is established according to the characteristics of actual production. Under the premise that the width-to-thickness ratio remains unchanged, by appropriately reducing the front tension, changing the rolling lubricating oil or padding paper at the winding end The occurrence of ribbing defects can be effectively suppressed by means of increasing friction.
Although the rolling speed is very slow when the titanium strip is cold-rolled, if the saponification value of the lubricating liquid is not good or the nozzle is blocked, it will lead to uneven lubrication and uneven stress distribution in the deformation zone, resulting in axial component force. In the rolling deformation zone, the axial component force generated by the offset of the neutral plane may be small, but it has a certain influence on the tightening of the center of the plate. In the rolling deformation process, local high points or local hardness will lead to uneven stress distribution in the deformation zone and generate axial component force. The interaction of equipment vibration and uneven tension will produce axial component force, and the mutual superposition effect of small center deviation, uneven thickness and pore deviation between layers will produce axial component force during winding.
