ERW Steel Pipe Inner Shape Control for Torsional Fatigue
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Solution Overview
Problem
Existing electric resistance welded steel pipes lack sufficient torsional fatigue resistance, which is crucial for automotive stabilizers that undergo bending and torsional stresses.
Innovation Solution
Optimizing the inner peripheral shape near the electric resistance welded seam through stretch reduction rolling, by controlling the feed position of the steel pipe relative to the rolling rolls, to achieve improved formability and torsional fatigue resistance. This involves specific constraints on the wall thickness differences and arc lengths within the seam region, ensuring the r-value is 1.0 or greater, and the stretch reduction rolling is performed at a heating temperature of 650°C or greater with an accumulated stretch reduction ratio of 30% or greater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electric resistance welded steel pipe is used to replace steel bars for improving productivity and reducing weight, then productivity and weight reduction are achieved, but torsional fatigue resistance is insufficient
Solution Approach 1:
The patent applies local quality by creating a white layer with different properties (lower carbon content, lower hardness) specifically at the welded seam region, while maintaining different properties in the base metal region. This localized differentiation allows the seam region to have improved torsional fatigue resistance without compromising the overall pipe performance.
Solution Approach 2:
The patent changes material parameters by controlling the carbon content and hardness in the white layer region through specific welding parameters and heat treatment conditions. By adjusting these parameters, the patent achieves a balance between formability and torsional fatigue resistance in the welded seam area.
2Ease of manufacture
If high formability is required for bending operations, then formability must be improved, but this may compromise torsional fatigue resistance
Solution Approach 1:
The patent applies local quality by creating a white layer with different properties (lower carbon content, lower hardness) specifically at the welded seam region, while maintaining different properties in the base metal region. This localized differentiation allows the seam region to have improved torsional fatigue resistance without compromising the overall pipe performance.
Solution Approach 2:
The patent changes material parameters by controlling the carbon content and hardness in the white layer region through specific welding parameters and heat treatment conditions. By adjusting these parameters, the patent achieves a balance between formability and torsional fatigue resistance in the welded seam area.
3Ease of manufacture
If the inner peripheral shape near the welded seam is not optimized, then manufacturing is simpler, but torsional fatigue resistance is poor
Solution Approach 1:
The patent applies preliminary action by optimizing the inner peripheral shape near the welded seam during the stretching reduction rolling process before final pipe formation. This preliminary optimization of the seam region geometry prevents stress concentration and improves torsional fatigue resistance in subsequent service.
Solution Approach 2:
The patent changes geometric parameters by controlling the inner peripheral shape dimensions (H/W ratio) and wall thickness distribution in the seam region through the stretching reduction rolling process, achieving improved torsional fatigue resistance without significantly complicating manufacturing.
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
The optimized electric resistance welded steel pipes exhibit enhanced formability and torsional fatigue resistance, preventing galling and ensuring the pipes can withstand the required torsional stresses, making them suitable for automotive structural members like stabilizers.
Implementation Method 1
stretch reduction rolling is performed on the steel pipe by hot rolling
Implementation Method 2
the stretch reduction rolling is performed at a heating temperature of 650°C or greater
Data Source
AI summary
An electric resistance welded steel pipe having excellent formability and torsional fatigue resistance and a method for manufacturing the same. The electric resistance welded steel pipe includes a seam region and a base metal region, the seam region having a range of ±10 degrees in a pipe circumferential direction with respect to an electric resistance welded seam formed in a pipe longitudinal direction, the base metal region being a region other than the seam region. The electric resistance welded steel pipe has an r-value in the pipe longitudinal direction of 1.0 or greater, H (mm) and W (mm) satisfy a specified formula, and Ts(MAX) (mm) and Tb(Ave) (mm) satisfy a specified formula.