ERW Metal Tube Weld Geometry to Stop Bend-Induced Cracking
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Solution Overview
Problem
Electric resistance welded pipes experience cracking during severe processing like 90° bending due to the decreased toughness of discharged metal from welded portions, which can propagate to the base material.
Innovation Solution
The method involves butting and welding the side ends of a metal strip such that the inclined surface remains on the excess metal, preventing the discharged metal from being welded to the excess metal, thereby avoiding cracking propagation to the base material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electric resistance welding is performed on metal strip side ends, then the metal strip can be joined to form a pipe, but cracking occurs in the discharged metal during severe processing such as 90° bending
Solution Approach 1:
The invention segments the welded portion into distinct zones: discharged metal, excess metal, and base material. By creating this segmentation through controlled welding parameters, the crack propagation path is interrupted at the excess metal zone, preventing cracks from reaching the base material even when the discharged metal cracks during severe processing.
Solution Approach 2:
The invention applies local quality by creating a specific structural configuration at the welded portion where excess metal forms a protective layer between the discharged metal and base material. This local structural modification ensures that the base material maintains its integrity while the discharged metal zone can undergo cracking without compromising overall pipe reliability.
2Manufacturing precision
If the discharged metal is welded to the excess metal, then the welded portion appears complete, but cracking propagates from the discharged metal to the base material through the excess metal
Solution Approach 1:
The invention extracts the harmful function of the excess metal by preventing it from serving as a crack propagation pathway. By controlling the welding parameters to create a distinct boundary between the discharged metal and excess metal, the excess metal is effectively removed from the crack propagation chain, even though it remains physically present in the welded structure.
Solution Approach 2:
The excess metal acts as an intermediary barrier that interrupts crack propagation. By maintaining a specific structural relationship where the excess metal is positioned between the discharged metal and base material, it serves as a mediator that absorbs or stops crack propagation before it can reach the base material, while still allowing the welded portion to appear complete.
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 configuration effectively prevents cracking propagation to the base material even when cracking occurs in the discharged metal, especially useful for high-strength metal strips with tensile strength above 700 MPa, and allows for improved bendability and hardenability through specific chemical composition adjustments.
Implementation Method 1
welding the side ends by means of high frequency heating
Data Source
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AI summary
Provided is a method for manufacturing an electric resistance welded metal pipe by butting side ends of a metal strip against each other and then welding the side ends by high frequency heating to manufacture an electric resistance welded metal pipe, each side end being provided with an inner surface side corner portion located on an inner surface side of the electric resistance welded metal pipe, wherein the method comprises a step of forming an inclined surface at the inner surface side corner portion before butting the side ends of the metal strip; and wherein the side ends are butted and welded to each other such that the inclined surface remains on an excess metal of the metal pipe after electric resistance welding and a discharged metal is not welded to the excess metal.