Blooming and rolling of molybdenum sheet
The quality of the slab with open edge at 1 300 ℃ and 1 400 ℃ is good. If the opening temperature is too high, it will not only make the grains coarse and waste resources, but also have a negative impact on the structure and properties of the finished molybdenum sheet (the mechanical properties of the molybdenum sheet produced by the low temperature blooming rolling process are superior to that of the high temperature blooming rolling molybdenum sheet, and the elongation rate is obviously improved under the condition of the same strength. The results show that the grain size of molybdenum sheet rolled at lower temperature is longer than that of molybdenum sheet rolled at high temperature. If the temperature is too low, it is easy to crack. When choosing the appropriate temperature, we should not only consider the past experience, but also consider the process fluctuation of powder metallurgy.
Initial pass deformation rate: set the blooming temperature at 1300 ℃ and select 30% ~ 35% and 35% ~ 40% deformation rates for cross rolling test. The microstructure of 2 mm thick molybdenum sheet produced by two rolling processes was studied. From 35% to 40%, it can be seen that the microstructure of molybdenum sheet is fiber like and slender grains and overlapped with each other. The grain arrangement is compact, the crystal boundary is relatively straight, and the holes are few. The contact surface between molybdenum grains is larger, so the interface bonding is more compact; however, the fiber structure of 30% - 35% rolled molybdenum sheet is coarser and shorter, the interface bonding is not compact, and there are holes in different degrees. Obviously, the microstructure of 35% ~ 40% molybdenum sheet is better. Therefore, the deformation rate of the first pass is selected 35%~40%.
Final rolling temperature of hot rolling: 1300 ℃ is selected as the starting temperature of hot rolling for the above two kinds of rolled molybdenum sheets, the deformation rate of the first pass is 35% ~ 40%, and the heating time is determined as 50 min according to the charging amount in the furnace. At the same time, the uniform annealing treatment of molybdenum slab is realized, and the final rolling temperature of hot rolling is 1000 ℃ and 1100 ℃. The same warm rolling and cold rolling annealing process is used in the follow-up process. The thickness of finished products is easy to compare in order to exclude the influence of other factors. The above slab size is 0.5mm thin molybdenum sheet.
The microstructure of molybdenum sheet rolled at 1000 ℃ with 35% ~ 40% hot rolling deformation rate is fine and uniform, and the distribution is dense in the thickness of the plate. However, the fiber structure of the molybdenum sheet rolled at 1100 ℃ is coarser and shorter, the grain interface is not too tight, and the deformation is uneven, which leads to the inhomogeneous physical properties and mechanical state of the molybdenum sheet, which makes the plasticity of the molybdenum sheet decrease and the elongation decreases. It can be seen that the microstructure of molybdenum sheet is better when the deformation rate is 35% ~ 40% and the final rolling temperature is 1000 ℃.
