Hot Rolling of Large Size Molybdenum Plate
Hot Rolling of Large Size Molybdenum Plate
The 650 mm wide milling machine can do hot rolling for large size molybdenum plate. During the rolling process, a hydrogen-filled furnace provides a purified environment for the process of annealing the large size molybdenum plate. A regular size of finished cold rolled plate is about 0.4~0.5 x 700~800 x 2000~3000 mm. Therefore, the hot rolled plate used to roll to cold rolled plate needs to be much bigger in width, height and length of the finished cold rolled plate. Additionally, depending on the required size of the rolled plate, either a single-roll or double-roll process can be used. Usually, the 2.9-3.1mm thick finished plate doesn’t have any defects on its surface.
Cold Rolling of Large Size Molybdenum Plate
A regular cold milling machine with a width of 550mm can roll out 400~510mm wide large size molybdenum plates. On the other hand, a four-rolls reversible cold milling machine with a width of 1200 mm can roll out 700~800mm wide molybdenum sheet. Therefore, the four-rolls reversible cold milling machine can ensure the desired size for a large rolled plate.
According to our experience, some defects such as peeling and delamination usually appear during the progress of reversible cold rolling. Therefore, a cold rolling process needs to avoid or reduce the problems caused by the peeling and delamination as much as possible.
After many deformation tests under different rolling rates, we found various superficial defects such as cracked edges, peelings and delamination in the head and tail area of the finished plate. Additionally, the internal structure of molybdenum sheet will change based upon various rolling rates. For example, when the rolling rate is low there will be a short, thick and uneven “fibrous tissue” along the rolling direction. When the rolling rate is high, there will be a slender and uniform “fibrous tissue” along the rolling direction. The changes of internal structure will result in anisotropy in the subsequent deformation of the large size molybdenum plate. The anisotropy will adversely affect the subsequent deformation. In order to reduce this disadvantage, the molybdenum blank should be rolled in reverse after a moderate deformation.
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