Back-Pressure Extrusion Mold for Tail-Shrinkage-Free Magnesium Ingots
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Solution Overview
Problem
Traditional forward extrusion methods for producing large-size magnesium alloys result in tail shrinkage, material waste, and high energy consumption due to uneven metal flow and the need for multiple heating and reheating cycles.
Innovation Solution
A mold design utilizing back pressure severe plastic deformation with a recoverable discard block and a back pressure plate to achieve continuous extrusion without tail shrinkage, reducing material waste, and minimizing the number of heating cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional forward extrusion is used, then the extrusion process is simple and production flexibility is high, but tail shrinkage occurs due to uneven metal flow
Solution Approach 1:
The patent inverts the traditional extrusion direction by applying back pressure from the lower mold cavity upward through the inclined upper mold cavity. This reverse extrusion approach transforms the metal flow pattern, ensuring uniform flow from the edge toward the center rather than the traditional center-to-edge flow that causes tail shrinkage
Solution Approach 2:
The patent introduces an inclined upper mold cavity that creates different deformation conditions at different locations. The inclination angle varies the compression force distribution, applying greater pressure to regions that need more deformation while reducing pressure on already-deformed areas, thereby achieving uniform metal flow throughout the extrusion process
2Productivity
If traditional forward extrusion with conical deformation zone is used, then extrusion can be performed, but discard is generated requiring cutting of head and tail
Solution Approach 1:
The patent changes the geometric parameters of the mold cavity from a traditional conical shape to an inclined cavity with specific angle ranges (30-60 degrees). This parameter modification eliminates the need for a conical deformation zone that generates discard, allowing the entire blank to be utilized in the final product
Solution Approach 2:
The patent converts the previously harmful discard into a beneficial feature by designing the inclined cavity so that the metal flow naturally fills the entire cavity space including the inclined portion. The area that would have been discard in traditional extrusion now becomes part of the usable product, eliminating the need for cutting operations
3Strength
If multiple heating, repeated extrusion and upsetting is used for large-size magnesium alloys, then strengthening and toughening effect is achieved, but energy consumption is high and production time is long
Solution Approach 1:
The patent implements continuous severe plastic deformation in a single extrusion operation rather than requiring multiple discrete heating-extrusion-upsetting cycles. The inclined cavity design enables the metal to undergo continuous deformation throughout the entire process, maintaining plastic flow and strengthening effect without interruption or reheating
Solution Approach 2:
The patent performs all necessary deformation and strengthening in advance during the single extrusion process. The inclined cavity is designed to create sufficient deformation zone length that accomplishes the cumulative strain effect of multiple cycles in one continuous operation, eliminating the need for subsequent reheating and processing steps
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the production of large-size rare earth magnesium alloy ingots without tail shrinkage, increases material utilization, reduces production time and energy consumption, and enhances the strengthening effect of the alloy.
Implementation Method 1
The recoverable discard block can be deformed to fill an extrusion deformation area, but can also be restored by reshaping
Implementation Method 2
back pressure severe plastic deformation
Implementation Method 3
back pressure severe plastic deformation
Implementation Method 4
The recoverable discard block is in a molten state at high temperature
Data Source
AI summary
A mold for preparing large-size rare earth magnesium alloy ingot without tail shrinkage by back pressure plastic deformation includes a male mold, a female mold, a recoverable discard block and a back pressure plate connected with a pushing cylinder of the press machine. 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. The recoverable discard block is configured to be deformed to fill an extrusion deformation area and subsequently restored into the initial state of the recoverable discard block.