| CPC B21C 25/02 (2013.01) | 7 Claims |

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1. A system for preparing large-size rare earth magnesium alloy ingot without tail shrinkage by back pressure plastic deformation, comprising a male mold installed on an upper workbench of a press machine, a female mold installed on a lower workbench of the press machine, a recoverable discard block and a back pressure plate connected with a pushing cylinder of the press machine, wherein the female mold is provided with an upper mold cavity and a lower mold cavity, an upper part of the upper mold cavity is configured for placing blanks, the recoverable discard block and the male mold, and a lower part of the upper mold cavity is inclined inward to form an extrusion deformation area in communication with the lower mold cavity;
the recoverable discard block separates the blanks from the male mold, the recoverable discard block is made of deformable material, and the recoverable discard block is configured to be deformed to fill the extrusion deformation area and restored by reshaping;
an upper part of the back pressure plate is located within the lower mold cavity, a molding cavity is formed between the upper part of the back pressure plate and the upper mold cavity, the back pressure plate comprises an upper surface that is raised in a middle portion of the back pressure plate to form an angle, and the recoverable discard block is made of a mixture of fluorite powder and graphite.
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