ERW Pipe Weld Geometry for Better Double-Tube Fit
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Solution Overview
Problem
In electric resistance welded pipes or tubes used as outer pipes or tubes in double pipes or tubes, the convexity height of the cutting residual part after cutting the weld bead on the inner side can be high, leading to poor contact between the inner and outer pipes or tubes, especially around the convexly raised cutting residual part.
Innovation Solution
The convexity height of the cutting residual part is reduced by cutting the weld bead on the inner side only once, using a double V groove shape for the end surfaces before welding, and adjusting the frequency of the high-frequency current used in electric resistance welding to between 500 kHz and 5000 kHz, which narrows the heat-affected zone and reduces high-temperature deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the weld bead is cut off on the inner side of the electric resistance welded pipe or tube, then the fit between inner and outer pipes or tubes is improved, but the convexity height of the cutting residual part increases, causing poor contact
Solution Approach 1:
The patent applies parameter changes by adjusting the frequency of high-frequency current used in electric resistance welding to between 500 kHz and 5000 kHz. This frequency parameter change narrows the heat-affected zone and reduces high-temperature deformation, resulting in reduced convexity height of the cutting residual part while maintaining good fit between pipes or tubes
Solution Approach 2:
The patent applies local quality by creating a double V groove shape at the end surfaces before welding, which localizes the heat-affected zone and controls the deformation pattern specifically at the weld area, reducing convexity at critical locations
2Manufacturing precision
If the convexity height of the cutting residual part is reduced by changing the shape of the bead cutting blade, then the fit is improved, but resistance during cutting increases, causing chattering vibration and unstable cutting mark
Solution Approach 1:
Instead of changing the cutting blade shape, the patent changes the welding parameter (frequency of high-frequency current to 500-5000 kHz) to reduce convexity height at the source, thereby avoiding the harmful effects of blade shape modification on cutting stability
3Shape
If high-frequency current with frequency between 500 kHz and 5000 kHz is used, then the heat-affected zone is narrowed and convexity height is reduced, but welding process complexity increases
Solution Approach 1:
The patent utilizes a specific frequency range (500-5000 kHz) of high-frequency current that is technologically mature and can be implemented with standard equipment, balancing the benefit of narrowed heat-affected zone with acceptable process complexity
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 results in an electric resistance welded pipe or tube with a small weld bead on the inner side and a low convexity height of the cutting residual part, enhancing the fit between the inner and outer pipes or tubes when used as a double pipe or tube, while maintaining excellent weld portion toughness.
Implementation Method 1
electric resistance welding in which high-frequency current is used
Implementation Method 2
high-frequency current is used, the heat-affected zone can be narrowed
Data Source
AI summary
An electric resistance welded pipe or tube comprises a weld portion in a pipe or tube longitudinal direction, wherein a maximum value of a wall thickness distribution of the weld portion is less than or equal to 1.05 times an average wall thickness of the electric resistance welded pipe or tube, a width of a weld metal in the weld portion in a circumferential direction is 1 μm or more and 800 μm or less over an entire thickness of the electric resistance welded pipe or tube, and a ratio of a maximum value to a minimum value (=maximum value/minimum value) of the width of the weld metal is 1.0 or more and 2.5 or less.