Analysis on spinning process of molybdenum crucible
Roller track:The roller track of molybdenum crucible is in the order of a → B → C → D → e → f → g → h → I → J → K. It is composed of five curves, namely, the forward cutter curve, the reverse cutter curve, the feed curve, the die sticking curve and the exit curve. The AB section is the positive cutter curve, which is used for the shape change of molybdenum plate, and belongs to the typical ordinary spinning; BC, CD and de sections are exit curves, which are used to adjust the initial position of the roller of the subsequent reverse cutting curve; EF section is the reverse tool curve, which is used for the shape change of molybdenum plate, which belongs to typical ordinary spinning; section is the feed curve, which is used to accurately form the "rudiment" of world collapse close to the core mold, with both shear deformation and flow deformation, belonging to the typical shear rheological composite spinning; GH, HL and segment K are exit curves, which are used to adjust the initial position of the roller in the follow-up molding curve; section K is the clamping curve, which is used for the wall thickness control and internal surface quality finishing of crucible, which belongs to typical flow spinning. Therefore, the continuous deformation of one section spinning curve of molybdenum metal is carried out by each roller track cycle.
Because the molybdenum crucible is formed by one-time spinning of molybdenum plate, there is no distinct spinning pass. The pass thinning rate and the feed rate of the roller pass are all in different curve segments of the roller track, which can be realized by adjusting the feed speed of the spindle and the rotation speed of the spindle.
Clearance of mandrel roller:The clearance between the mandrel and the roller includes the clearance between the straight section of the feed curve and the bus bar of the mandrel, and the clearance o between the JK and the bus bar of the mandrel. These two clearance values determine the wall thickness and inner surface roughness of molybdenum crucible, which can be adjusted empirically according to the elastic deformation of spinning machine, the concession of hydraulic system and the elastic springback of molybdenum metal. As molybdenum is a brittle metal, the clearance between mandrel and roller should be smaller as far as possible on the premise of ensuring the minimum wall thickness of molybdenum depletion. Under the experimental conditions, 8 and o are 0.9 ~ 0.95 times and 0.8 ~ 0.85 times of the wall thickness of molybdenum crucible respectively.
Pass thinning rate:In each roller curve, the pass deformation of forward and reverse cutter curves can be ignored, and the pass thinning rate V {"of feed curve depends on the clearance between feed curve and core die, the reverse plastic deformation of molybdenum metal, and the reduction of forward and reverse cutter curves. Feed curve die clearance can be preset. The local position of contact between the roller feed and molybdenum metal is similar to plane rolling. Under the rolling action of the roller, the left plastic flow is mainly produced and the right plastic flow is inevitable, which will lead to the increase of the thickness of molybdenum crucible. If the positive cutting curve is too large, the molybdenum plates pressed by the adjacent passes "support" each other to form an arch bridge. The reverse cutting curve is difficult to press and paste the extra metal arched to the surface of the core mold, and the feed curve has no effect at all; By adjusting the B point end of the positive knife curve (to reduce the inclination and reduction of the pass) and increase the number of positive curve (to reduce its deformation), the E of the molybdenum crucible can be obtained by raising the starting point of the reverse knife curve (increasing the press effect). The pass thinning rate YVP depends on the gap o between the clamping curve K and the mandrel bus and the reverse plastic deformation of molybdenum. Under the experimental conditions, when O and o are set as 0.9 ~ 0.95 times and 0.8 ~ 0.85 times of the crucible wall thickness respectively, and using the appropriate roller trajectory curve, the molybdenum plate with wall thickness of 4.5 mm can be spun into a molybdenum crucible side wall with a thickness of 2.8 mm. This pass thinning rate is formed by the first feed curve and the second die placement curve, which is in line with the plastic range of molybdenum metal with elongation of 10% 15% [21l] at 400 ~ 600 ℃.
