Processing technology of Rhenium plates and Rhenium foil

The rhenium foil is processed by cold rolling directly on a two-high mill and proper intermediate annealing. After the sintered strips are cut into a certain length of rolling and forming strips by an electric comb saw, they are annealed in a hydrogen molybdenum wire furnace at 1500℃ for 30 minutes to eliminate the processing stress, and then rolled laterally in a two-high mill (with a roll diameter of 350 mm).Within the range of 12 ~ 2 mm thickness, the processing rate between each annealing shall be controlled between 15 ~ 25%.Generally rolling 20%, but due to the mill pressure limit, as the thickness of the plate decreases, the processing rate decreases gradually.

Due to the extremely fast processing and hardening of metal Rhenium, in order to make full use of the plasticity after metal annealing, the first cold rolling of annealed rhenium plate must be put under great pressure, so that the first pressure reduction amount reaches 8-10% or so, especially when the plate is relatively thin, attention should be paid to control. In the mill pressure allowed under the best control of annealing processing in less than 10 times. If the first few lines of cold rolling do not give large pressure, and make the plate processing hardened, even if the number of processing increases dozens of times can not make the total processing rate of 20%.

After the plate is cold-rolled, clean the lubricating oil on the surface with carbon tetrachloride, then scrub the remaining dirty carbon tetrachloride with anhydrous alcohol, and then put it into the molybdenum box for furnace annealing. The surface quality of plate is greatly affected by the cleaning before annealing and the protection of molybdenum box. If the plate does not remove oil before annealing, a layer of gray-black film will be formed on the surface after annealing. If it is not cleaned up by grinding wheel, it cannot be cleaned during subsequent processing and annealing, which will seriously affect the processing performance and surface quality of the plate. Before annealing, if the plates do not use alcohol to scrub carbon tetrachloride or the scrubbing is not clean, various patterns will be left on the surface of the plates after annealing. In the subsequent processing annealing can not be removed, directly affect the surface quality of the plate. The sheet must be coated tightly with molybdenum box or molybdenum sheet during annealing to prevent oxidation during annealing cooling, which will affect the surface quality of the product.

The annealing temperature is 1500°C±30° C in a horizontal molybdenum wire furnace. Annealing heat preservation time depends on the amount of rhenium board, general heat preservation 30 ~ 60 minutes. Annealing temperature was determined by Tungsten - rhenium thermocouple.

2.0-2.7mm thick plates are rolled on a four-high universal mill (150mm working roller diameter), the total processing rate of annealing room is controlled at 20%, the annealing temperature is controlled at 1450°C±30°C, and the annealing holding time is 60 minutes.

The 0.7 ~ 0.2 mm thick plate is rolled on a four-high universal mill (working mixing diameter 75 mm), the total processing rate is controlled at 15% in the annealing room, and the annealing temperature is controlled at 1400°C for 60 minutes.

0.2 ~ 0.02 mm thick foil rolled with tension on a 20-talk rolling mill. The diameter of the working roll is 10 mm, the length of the working strip is 130 mm, and the working roll is 0.03 mm. The total processing rate between annealing is controlled at about 35%, and the annealing temperature is 1200 ~ 1300°C for 60 minutes. In order to prevent bonding and oxidation of the surface of foil during annealing, the annealing is carried out in the vacuum molybdenum foil furnace. The vacuum degree should be controlled above 1×10-4 mm hg.

Due to the limited length of the plate, the steel lead strip is welded by spot welder on the two ends of the 20-roll mill. The thickness of the lead strip is about 2 times of the thickness of the rhenium foil, and the width of the lead strip should be slightly larger than the width of the rhenium foil. Welding must ensure that the lead band and rhenium foil on the same center line or parallel. Do not allow the eye can find twists and turns, otherwise the rhenium foil in the tension when rolling easy to fracture wrinkly and scrap.

Controlling the tension of rhenium foil during rolling has a direct impact on the surface quality and machining efficiency of the foil. Especially, when the thickness of the sheet is less than 0.05 mm, the tension is too large, which easily causes fracture of the foil and a large number of dispersed fine mesh for the scrap of the sheet. If the tension is too small, it cannot be rolled down and the required processing rate cannot be guaranteed. According to our experience, the tension is generally controlled within the range of 10~15/ kg².The thinner the foil, the lower tension should be chosen.

After rolling, the chemical analysis of the box material showed that the main element susceptible to contamination was increased from 0.4 to 6PPm molybdenum, from 0.4 to 1.3PPm nickel, and from 1.2 to 11.0PPm iron. The remaining elements remain basically unchanged, and the purity of foil is still greater than 99.99% rhenium.