Strip Edge Tapering for Electric Resistance Welded Pipe
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Solution Overview
Problem
Electric resistance welding pipes often suffer from inadequate toughness and strength of welds due to the presence of oxides, known as penetrators, which are not effectively discharged during the welding process, leading to reduced performance, especially in low-temperature applications.
Innovation Solution
The method involves shaping the strip edges with a tapering angle of 25° to 50° and a distance of 20% to 40% of the strip thickness to facilitate the discharge of melting steel and remove penetrators, using a combination of cutting or shaving rolls and finpass rolling to ensure efficient tapering without reducing production efficiency, even with varying strip thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If straight or planar tapering with uniform slope is used to shape strip edges, then the strip edge can be easily shaped, but defects such as oxides (penetrators) are not adequately discharged along with melting steel
Solution Approach 1:
The invention applies curvature to the strip edge by forming a rounded shape with a specific radius of curvature (R1 at the apex, R2 at the base) instead of using straight or planar tapering. This curved geometry facilitates the discharge of melting steel and penetrators during electric resistance welding, resolving the contradiction by maintaining ease of shaping while significantly improving penetrator discharge effectiveness.
2Reliability
If cutting or shaving means is used to shape tapering on strip edges, then penetrators can be discharged, but production efficiency is reduced due to adjustment requirements for varying strip thicknesses
Solution Approach 1:
The invention performs preliminary shaping of the strip edge into a rounded form with specific radius of curvature before the electric resistance welding process. This preliminary action ensures that penetrators are properly positioned for discharge during welding, maintaining reliability while eliminating the need for repeated adjustments during production, thereby preserving productivity.
Solution Approach 2:
The invention changes the geometric parameters of the strip edge from linear dimensions (tapering angle, tapering length) to a curvature parameter (radius of curvature). This parameter transformation creates a more effective geometry for penetrator discharge that is less sensitive to variations in strip thickness, reducing adjustment requirements and maintaining production efficiency.
3Productivity
If conventional electric resistance welding is used without edge shaping, then production efficiency is maintained, but weld toughness and strength are insufficient due to retained penetrators
Solution Approach 1:
The invention introduces a rounded edge shape with specific radius of curvature (R1 at the apex, R2 at the base) to the strip edges before welding. This curved geometry fundamentally improves the welding process by facilitating the discharge of melting steel and penetrators, thereby significantly enhancing weld toughness and strength while maintaining production efficiency through a streamlined process.
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 electric resistance welding pipes with improved toughness and strength of welded seams, as demonstrated by Charpy test results showing higher impact strength and lower brittle fracture surface ratios, while maintaining production efficiency.
Implementation Method 1
electric resistance welding
Implementation Method 2
induction heating section
Data Source
Figure 1~2
Figure 3A~4B
Figure 5~6B
AI summary
A method of efficiently manufacturing electric resistance welding pipes having excellent characterization of welded seams is provided, by which each lateral edge of a rounded strip immediately before electric resistance welding is securely shaped with desired tapering flexibly in response to change in strip thickness, so that welding quality may be kept to be excellent. A method of manufacturing electric resistance welding pipes, in which a strip 20 is subjected to forming, then edges thereof are confronted, and then the edges are subjected to electric resistance welding to form a pipe 30, includes a process that an edge and an edge opposed thereto at one of an upper-surface side and a lower-surface side of the strip are shaped with tapering before the forming by means of cutting or shaving 3, or finpass forming 4.