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Large thin-walled molybdenum crucible spinning process and numerical simulation

Date:2016/06/30

Molybdenum is a rare earth smelting crucible furnace, quartz furnaces and even sapphire single crystal growth furnace important container, especially in the sapphire single crystal manufacturing process, quality molybdenum crucible can directly affect the quality of the sapphire single crystal. With the development of LED industry, the demand for quality and yield of single crystal sapphire increasing as consumables molybdenum crucible requirements are also increasing. Traditional methods for preparing molybdenum crucible can not meet the growing demand, the results of the use of spinning ways to solve the problem molybdenum crucible was prepared to provide a new technical approach.
 
Using conventional spinning and spinning complex with strong spin mode, drawing on the experience of existing hot refractory metal spin forming, numerical simulation and process test, the successful use of the spinning process for preparing a molybdenum crucible, molybdenum material obtained pure Pu with strong spin-spin process parameters required to match, and theoretical analysis of molybdenum spinning process we have an objective summary of the law.
 
 
By performance of pure molybdenum materials analysis, numerical simulation of pure molybdenum materials spinning process, and the specific process test, the successful preparation of a molybdenum crucible, and reached the following three conclusions:
 
(1) pure molybdenum material because of its poor plasticity, can not be completed spinning at room temperature. By high temperature tensile tests, stress-strain curves analytically pure molybdenum materials at high temperatures, at temperatures higher than 600 ℃, pure molybdenum materials demonstrated plasticity sufficient to complete the spinning process, at temperatures higher than 900 ℃, recrystallization grains produced grain growth phenomenon occurs, it will affect the preparation of a molybdenum crucible performance. Therefore, pure molybdenum materials For spinning, you must use an external heating tool heated to between 600-900 ℃. Also through simulation, spinning process, the thinning rate can not pass more than 40%, otherwise the material is easy to accumulate in front of the spinning. In the spinning process, the feed ratio can not exceed 1.0mm / r, otherwise there are differences during deformation strain rate throughout the material, the material likely to cause instability, shaping the product results are not satisfactory.
 
(2) Since the molybdenum crucible wall thickness requirements change, tapered, taking into account the cost. Optimal Spinning molybdenum crucible process scheme is: molybdenum crucible required size requirements, by an equal volume of pure molybdenum method to calculate the diameter of the circle and the thickness of the slab, hot-rolled pure molybdenum selection round blank slab, this plate billet multi-pass conventional spinning molding, when the entire spinning process the workpiece and the desired product taper bottom of the crucible same size, spinning stop using multi-pass strong spin, spin to the wall of the workpiece size of product requirements, It shall be carried out under heating.
 
(3) spinning process, equipment, tooling, measuring instruments will affect the quality and geometric precision molded products. Molybdenum crucible spinning process, the spinning machine must have the ability to spin Spinning and strong, the heating process must be aerobic - acetylene flame or an electromagnetic induction heating equipment. Spinning tooling needs including rotary wheel, mandrel, the top end and other auxiliary tooling, spinning process in a molybdenum crucible, the conventional spinning process due to changes in product taper, the taper mandrel must match the mandrel, in large molybdenum crucible conventional spinning process, using three different tapered mandrel to ensure that the final product after forming the taper; knob fillet diameter will directly affect the quality of the process of spinning and spin to obtain the product, considering the shape and size of the blank , spinning process parameters, the choice of a molybdenum crucible in preparation large rounded Cape rotary knob; the top end in the spinning process of the metal flow has a rigid constraint, select the top end inappropriate prone to bulge phenomenon spun process, according to the size of the molybdenum crucible bottom and top tight power requirements, the use of small diameter conventional spinning process to ensure that the bottom end of the top shape and size, strong spin process using large-diameter top end of the metal flow constraints, to ensure product quality molding. Meanwhile, throughout the process, the temperature of the workpiece to be real-time monitoring.
 
The main innovations:
 
(1) of the refractory metals molybdenum materials spinning process of inquiry. Molybdenum materials due to the performance of its high melting point, high strength, and is not suitable for processing plastic forming manner, usually for molybdenum material casting, sintering method, preparation of parts to sheet metal, wire mostly single part shape. To the processing of complex shaped parts, traditional methods of material utilization is low, the processing method is complicated, high energy consumption. The results of the analysis of molybdenum mechanical properties at high temperatures, and the use of numerical simulation of mechanical model of molybdenum material flow spinning. Analysis of the results that can spin and spin-molybdenum and molybdenum materials P material, strong rotation required technical conditions and the successful use of the legal system had pure molybdenum thin-walled spinning rotors in the country for processing and molybdenum material in the forefront.
 
(2) Spinning strengthen Rotary composite spinning method applied in the preparation of thin-walled parts of varying wall thickness. Taking into account the characteristics required for preparing a molybdenum crucible thin-walled rotor, linearly varying wall thickness, usually single shear spinning or spinning general, the process is more difficult to implement, difficult to simultaneously achieve the above two technical requirements. Considering the strong spin and spin using the S & P composite, for slab Spinning processed geometry, strong spin guaranteed wall thickness. Spinning with strong spin simultaneously, varying wall thickness prepared thin-walled rotors.
 
The main practical significance:
 
(1) as previously described, molybdenum crucible has a very important role in the sapphire single crystal growth furnace, and quality molybdenum crucible will affect the quality of growth is sapphire single crystal. Molybdenum crucible traditional production methods in utilization of raw materials to obtain the performance indicators molybdenum crucible, the complexity of processing methods and other aspects of the existence of certain deficiencies. Spinning production of molybdenum crucible material utilization, basically do not waste raw materials; obtained while molybdenum crucible surface accuracy and the shape and size to meet the requirements, but also has good mechanical properties and extend the life of a molybdenum crucible; spinning Preparation of a molybdenum crucible processing cycle is short, simple process, it is possible to improve production efficiency molybdenum crucibles.
 
(2) For the molybdenum crucible spinning method to process the inquiry, carried out for the subsequent spinning of refractory metal, composite spinning method research to provide technical support and theoretical guidance. Broaden the refractory metal applications; some good material for processing, to provide processing ideas; design of some models take into account the bad parts processing, new processing methods by reference.


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