knowledges

Preparation Of Large Molybdenum Crucible Single Crystal Sapphire

2024-01-05 18:00:06

Molybdenum crucible is an important vessel in rare earth smelting furnace, quartz furnace and sapphire single crystal growth furnace. Especially in the preparation of sapphire single crystal, the quality of molybdenum crucible can directly affect the quality of sapphire single crystal. With the development of LED industry, the production and quality of sapphire single crystal demand is increasing, as a consumable molybdenum crucible requirements are also increasingly high. The traditional method of preparing molybdenum crucible can not meet the increasing demand. This result provides a new technical way for solving the difficult problem of preparing molybdenum crucible by means of spinning processing.

Molybdenum Alloy Crucibles of China

Using normal spin and strong spin from the experience of existing refractory metal hot spinning forming, through numerical simulation and process test, successfully used spinning processing method for the preparation of the molybdenum crucible, the normal spin molybdenum materials and strong spin takes matching process parameters, and through the theoretical analysis on molybdenum spinning process is an objective law.


Through performance analysis of pure molybdenum material, numerical simulation of spinning process of pure molybdenum material, and specific technological test, molybdenum crucible was successfully prepared, and the following three main conclusions were drawn:


(1) Due to its poor plasticity, pure molybdenum material cannot be processed by spinning at room temperature. Through high temperature tensile test, the stress-strain curve of pure molybdenum material at high temperature was analyzed. When the temperature was higher than 600℃, the plasticity of pure molybdenum material was enough to complete spinning processing. When the temperature was higher than 900℃, the grain generated during recrystallization would grow up, which would affect the performance of preparing molybdenum crucible. Therefore, to spin the pure molybdenum material, it is necessary to use external heating tools to heat it to 600-900 ℃. In addition, through simulation calculation, the pass thinning rate cannot be higher than 40% in the spinning process, otherwise the material is easy to accumulate in front of the spinning. In the spinning process, the feed ratio should not exceed 1.0mm/r, otherwise, the deformation rate of the material varies in the deformation process, which may easily cause material instability and the product forming result is not ideal.


(2) Because the molybdenum crucible requires the wall thickness to be changed and the taper to be taken into consideration the cost. Optimal spinning processing of molybdenum crucible process is: according to the required size requirements, molybdenum crucible by volumetric method to calculate the pure molybdenum circle diameter and thickness of the slab, slab, pure molybdenum blank choose hot rolled round on the slab multi-channel PuXuan forming, when the workpiece with taper of products, at the bottom of the crucible size required at the same time, stop PuXuan, by using multichannel strong spin, screw the wall thickness of workpiece to the size of the product requirements, the entire spinning process must be under heating conditions.


(3) During spinning processing, equipment, tooling and measuring instruments will affect the quality and geometric accuracy of the formed products. In the process of molybdenum crucible spinning, spinning machine must have the general spinning and strong spinning ability, heating process must be aerobic - acetylene flame or electromagnetic induction heating equipment. Spinning processing need tooling mainly includes the wheel, core mold, the tail and other auxiliary equipment, in the process of molybdenum crucible spinning, PuXuan process due to the change of product taper, the mandrel must be compatible with gradient of core modules, in the process of large molybdenum crucible PuXuan, using three different taper core modules to ensure that the final forming of the products after taper; The round corner and diameter of the spinning wheel will directly affect the spinning process and the quality of the spinning products. Considering the shape and size of the blank and the spinning process parameters comprehensively, the large round corner common spinning wheel is selected in the preparation process of the molybdenum crucible. Tail top of metal flow in the process of spinning has a rigid constraints, tail top choice unsuitable easy bulge phenomenon in the process of spinning, according to the bottom of the molybdenum crucible size and requirement of top force, PuXuan process to choose small diameter at the bottom of the tail cap to ensure the shape size, using large diameter end of the strong spin, to constraints of liquid metal, ensure the quality of products forming. At the same time, in the whole process of processing, must be real-time monitoring of workpiece temperature.


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