Electroplastic Drawing of Thin-Walled Alloy Pipe to Prevent Cracking
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Solution Overview
Problem
Current pipe forming processes face challenges with metals having low plasticity and high work hardening capacity, as they tend to crack or fracture during large deformation, and there is a lack of research on electrically assisted drawing processes for pipes.
Innovation Solution
An electrically assisted forming process and device for high-strength metal alloy thin-walled pipes, involving multi-pass drawing using electro-plastic forming, with the introduction of pulse current to reduce forming force and work hardening, and the use of a low-melting point metal filler for annealing and recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional drawing forming is used for high-strength metal alloy pipes with low plasticity, then the process is simple, but cracks and tensile fracture easily occur during large deformation
Solution Approach 1:
The patent replaces traditional mechanical drawing forming with electroplastic forming, where pulse current is applied during the drawing process. The electrical field interacts with the metal material to reduce internal resistance and enhance plasticity, allowing large deformation without cracks or tensile fracture while maintaining process simplicity
Solution Approach 2:
The patent changes the physical state of the metal material by applying pulse current during drawing. The electrical parameters (current density, pulse duration, frequency) are controlled to temporarily alter the material's mechanical properties, increasing plasticity and reducing forming force requirements, thereby preventing cracks and fracture during large deformation
2Manufacturing precision
If multi-pass drawing is performed to achieve thin-walled pipe with high reduction rate, then the target dimensions are achieved, but serious work hardening occurs
Solution Approach 1:
The patent uses electroplastic forming instead of traditional mechanical drawing for multi-pass reduction. The pulse current reduces work hardening by modifying the material's flow stress characteristics during deformation, enabling high dimensional accuracy to be achieved while maintaining lower work hardening levels and improving formability
Solution Approach 2:
The patent applies periodic pulse current during each drawing pass and between passes. This periodic electrical stimulation helps reset the material's work hardening state, allowing multiple passes with high reduction rates (total processing rate >50%) to be performed while controlling cumulative work hardening and maintaining ductility
3Ease of manufacture
If low-melting point metal filler is used during drawing, then the forming process is assisted, but additional processing steps are required
Solution Approach 1:
The patent merges the drawing process with annealing by using low-melting point metal filler that melts during the drawing operation itself. The filler melts and coats the inner surface of the pipe, providing forming assistance and simultaneous annealing effect, thereby eliminating the need for separate annealing equipment and reducing overall process complexity
Solution Approach 2:
The patent utilizes the phase transition (melting) of low-melting point metal filler during drawing. The filler transitions from solid to liquid state under the combined effect of drawing friction heat and applied current, enabling it to flow and coat the pipe interior, providing lubrication and annealing effects during the forming process itself
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 process effectively reduces forming force, improves metal plasticity, and enhances formability of high-strength metals, while also improving production efficiency and reducing costs through fusible metal recovery during annealing.
Implementation Method 1
introducing a pulse current to the high-strength metal alloy pipe during the drawing, so as to reduce the forming force of the material, reduce the work hardening rate, improve the metal plasticity
Implementation Method 2
the low-melting point metal filler in the thin-walled pipe segment is melted and flows into a groove of the vacuum heat treatment furnace under an action of gravity
Implementation Method 3
vertically placing the thin-wall pipe segment in a vacuum heat treatment furnace for annealing treatment
Data Source
AI summary
An electrically assisted forming process and device for a high-strength metal alloy thin-walled pipe includes a die sleeve, wiring terminals, a pulse power supply, a die seat, sealing baffle plates, a drawing die, and a cooling water circulation chamber. A process for forming a high-strength metal alloy thin-walled pipe includes first, graphite or fusible metal, i.e., an aluminum rod, is introduced into a high-strength metal alloy pipe to be drawn to fill the whole pipe; and then, pulse current is introduced into a plastic deformation area of the thin-walled pipe. A cooling device can be provided to achieve a good cooling effect. The thin-walled pipe with corresponding length is cut according to a production requirement after processing is completed, and annealing treatment is performed in a vacuum heat treatment furnace.