Induction Bending of Thick-Walled Pipes
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Solution Overview
Problem
The existing method of induction bending for large-diameter, high-wall-thickness pressure-resistant pipes causes structural changes in the heat-affected zone, making subsequent heat treatment necessary, which negatively affects the mechanical properties of straight tangent sections, requiring their replacement and increasing material costs.
Innovation Solution
Subjecting all pipe sections, including tangents, to the same heat treatment as the bend section by coordinating the movements and temperatures of the induction device and feed unit, ensuring uniform heat exposure without counteracting forces during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tangent sections are replaced to maintain strength values, then the mechanical strength is preserved, but the work amount and construction time increase significantly
Solution Approach 1:
The patent performs preliminary controlled heating of the pipe bend section during the forming process itself, preparing the material structure in advance. This preliminary action reduces the need for extensive subsequent heat treatment and eliminates the requirement to replace tangent sections, thereby maintaining both strength and productivity.
Solution Approach 2:
The patent extracts the heat treatment requirement from the entire pipe structure and applies it only to the specific pipe bend section that needs it. This extraction eliminates the unnecessary heat treatment of tangent sections, preventing strength degradation and avoiding the need for replacement while maintaining construction efficiency.
2Strength
If higher-strength steels or greater wall thicknesses are used, then the minimum strength values are retained after post-heat treatment, but the material costs increase considerably
Solution Approach 1:
The patent applies heat treatment only to the pipe bend section where structural homogenization is needed, rather than treating the entire pipe including tangent sections. This localized approach preserves the strength of original material without requiring expensive higher-strength steels or increased wall thicknesses.
Solution Approach 2:
The patent converts the potential harm of heat treatment affecting tangent sections into a benefit by precisely controlling the heating zone. The heat treatment process, which could have degraded tangent strength, is instead used selectively to improve the pipe bend structure, eliminating the need for more expensive material alternatives.
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
This approach prevents the negative influence on strength values of tangent sections, reducing material waste and costs by maintaining mechanical strength without the need for tangent replacement, thus simplifying and accelerating the construction of complex tube structures.
Implementation Method 1
Such solid tubes can only be formed by inductively heating a narrow ring zone to a forming temperature of more than 850°C
Implementation Method 2
In the heat-affected zone, structural changes occur in the material
Implementation Method 3
the pipe bend is often subsequently heat-treated at a temperature of around 600°C
Data Source
Figure 1
Figure 2a~2c
Figure 2d
AI summary
The invention relates to a method for induction bend forming a compression-resistant pipe (1) having a large wall thickness and a large diameter. According to said method, in an initial phase t1, an initial tangent (3) of the pipe (1) is heat-treated by pushing the initial tangent (3) through the inductor (20) without the intervention of the bending lock (31). At the end of the initial tangent (3) the advance of the pipe is stopped at a time t2, and the inductor (20) is moved along the pipe (1) counter to the advance direction while the bending lock (31) is closed on the pipe (1). In order to induce the bending process in a phase t3, the movement speed of the inductor (20) is reduced to zero and the latter is moved to its bending position; at the same time, the advance of the pipe (1) is started. In a phase t4, a pipe bend (4) is produced at a constant process advance speed of the pipe (1). In a phase t5, the advance speed of the pipe (1) is reduced and the inductor (20) is accelerated counter to the advance direction while the bending lock (31) is opened. In a phase t6, a final tangent (5) is heated by further advancing the inductor in the opposite direction.