If the annealing temperature is set too high, the tape and roll will be bonded, which will slightly affect the surface quality of the product. In serious cases, it will cause the entire roll to be bonded and cannot be opened, resulting in waste products.
If the annealing temperature is set too low, the phenomenon of annealing will be opaque. Although the inner and outer layers of the coil meet the performance index requirements, the core product of the coil does not achieve the purpose of recrystallization annealing. The strength will exceed the standard and the grain ratio will be obvious. Small phenomena in the inner and outer layers. This will cause the performance of the entire volume to fluctuate greatly, making it unsafe to use.
In view of this situation, it is particularly important to formulate a reasonable annealing system to avoid bonding and avoid sandwiching.
The test materials were smelted, forged, slab prepared, hot rolled to 4.0~7.0mm hot coil, and cold rolled to 0.3~4.75mm. The coil slices were subjected to 720℃/30min for a single piece and 720℃/6h for the entire titanium strip. Heat treatment test, and then take samples from the core, outside and inside of the plate and titanium strip to compare the structure and properties of different locations of the plate and titanium coil.
The test found that titanium strip rolls with the same composition and thickness of 2.945mm were heat treated at 720°C/6h for the whole roll and 720°C/30min for the single piece. The tensile strength and yield strength values were basically consistent, and there was no significant difference in elongation. The same composition and 1.0mm titanium strip roll were heat treated at 720°C/6h for the whole roll and 720°C/30min for the single piece. The tensile strength and yield strength differed by about 10MPa, and the elongation was equivalent. The same composition and 0.5mm titanium strip roll were heat treated at 720℃/6h for the whole roll and 720℃/30min for the single piece. The tensile strength, yield strength and elongation were all equivalent.
Microstructure observation shows that: after heat treatment of 0.5mm strip and titanium strip at 720°C/6h, the head, middle and tail can obtain consistent vertical and horizontal structures. In order to compare the difference in the structure of the annealed strip coil and the single sheet, plates with the same composition and the same annealing regime were selected for sampling tests. It was found that under the same annealing regime, the titanium strip was annealed as a whole roll or as a single sheet. , both vertically and horizontally consistent structures can be obtained.
