Grooved Steel Pipe Edges for Toughness
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Solution Overview
Problem
Existing methods for manufacturing electric resistance welded steel pipes struggle to achieve high toughness at ultracold temperatures due to uneven current density and oxide discharge issues, particularly in larger diameters where sealed welding becomes impractical.
Innovation Solution
A method involving the application of a tapered shape to the edges of steel strips before electric resistance welding, with real-time measurement and adjustment of welding power based on groove shape and oxide quantity to ensure consistent toughness, using laser slit light imaging and ultrasonic flaw detection for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sealed welding is used to reduce oxide in the welded portion, then the toughness at ultracold temperatures is improved, but the device complexity and manufacturing difficulty increase significantly for pipes with outer diameter larger than φ165 mm
Solution Approach 1:
The invention extracts and removes oxides from the welded portion through a groove structure that enables oxide discharge. The groove shape (U-shaped, V-shaped, or tapered) creates a pathway for oxides to be expelled from the weld zone during electric resistance welding, eliminating the need for complex sealed welding equipment while achieving low oxide content and high toughness at ultracold temperatures.
Solution Approach 2:
The invention changes the geometric parameters of the edge configuration by introducing grooves with specific shapes and dimensions. These parameter changes (groove depth, width, angle) optimize the current density distribution and facilitate oxide discharge, resolving the contradiction between simplicity and effectiveness.
2Productivity
If electric resistance welding is applied to join the edges of the open pipe, then the manufacturing efficiency is improved, but uneven current density in the strip-thickness direction causes temperature distribution unevenness and oxide discharge failure
Solution Approach 1:
The invention applies local quality by creating grooves at specific locations (edges of the open pipe) to modify the current density distribution locally. The groove geometry concentrates current at the groove root, ensuring adequate heating and melting in the critical weld zone while maintaining overall manufacturing efficiency through electric resistance welding.
Solution Approach 2:
The groove shape is prepared in advance before welding occurs. This preliminary action modifies the edge geometry to predetermine the current density distribution pattern, ensuring that when electric resistance welding is applied, the temperature distribution is optimized for complete oxide discharge and strong weld formation.
3Ease of manufacture
If the edges of the open pipe have a rectangular shape for conventional electric resistance welding, then the ease of manufacture is improved, but the current density is concentrated at outer and inner surfaces while the center portion has low current density, leading to temperature unevenness
Solution Approach 1:
The invention introduces asymmetric groove shapes (U-shaped, V-shaped, or tapered) at the edges of the open pipe. This asymmetric geometry breaks the symmetry of the rectangular edge, creating a controlled current concentration path through the groove root that ensures uniform temperature distribution and complete oxide discharge while remaining manufacturable.
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 stabilizes the manufacturing of electric resistance welded steel pipes with desirable toughness at ultracold temperatures by equalizing current density and minimizing oxide presence, even with dimensional variations in the steel strip, thus overcoming the limitations of sealed welding.
Implementation Method 1
measuring the groove shape by irradiating an edge of the open pipe with laser slit light
Implementation Method 2
high-frequency current is applied to the edges of the open pipe, thereby generating Joule heat, the edges are heated and melted with the Joule heat
Implementation Method 3
measuring the quantity of oxide at the welded portion after the electric resistance welding
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A method for manufacturing an electric resistance steel pipe having a good toughness at a welded portion is provided, the method being capable of stably manufacturing an electric resistance welded steel pipe having a desirable toughness at a welded portion although a steel strip serving as a base material has a dimensional variation. Groove shapes 5a and 5b are applied to edges 4a and 4b of an open pipe 4, an edge shape monitor 11 continuously captures images of the edges 4a and 4b immediately before electric resistance welding, and the captured images are input to an arithmetic processing unit 14 for image processing. Thus, a groove height h is measured, an optimum welding electric power is calculated on the basis of the measurement result, and the welding electric power from electric power generating equipment 6 is adjusted. Furthermore, an ultrasonic flaw detector 15 continuously measures an oxide distribution at the welded portion after the electric resistance welding. The optimum welding electric power is calculated on the basis of the measurement result, and the welding electric power from the welding power generating equipment 6 is adjusted.