ERW Steel Pipe Seam Geometry for Formability and Torsional Fatigue
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Solution Overview
Problem
Existing electric resistance welded steel pipes do not adequately address the requirements for both high formability and torsional fatigue resistance, particularly in automotive applications like stabilizers, where bending and torsional stresses are prevalent.
Innovation Solution
Optimizing the inner peripheral shape near the electric resistance welded seam by controlling the feed position of the steel pipe during stretch reduction rolling, ensuring the seam avoids specific regions of the rolling rolls, and maintaining an r-value of 1.0 or greater in the base metal region, with specific ratios for wall thickness and diameter differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If stretch reduction rolling is performed on electric resistance welded steel pipe, then the inner peripheral shape near the welded seam changes, but the torsional fatigue resistance deteriorates due to unfavorable shape changes
Solution Approach 1:
The patent applies preliminary action by carefully positioning the welded seam at specific angular locations (0°±10° or 90°±10°) before the stretch reduction rolling process begins. This pre-positioning ensures that during subsequent rolling operations, the seam avoids critical stress zones and unfavorable deformation regions, thereby maintaining torsional fatigue resistance while achieving the desired inner peripheral shape changes.
Solution Approach 2:
The patent applies local quality by creating different geometric characteristics at different locations of the pipe cross-section. Specifically, the inner peripheral shape is intentionally differentiated between regions near the welded seam and regions away from it, with the seam region having controlled wall thickness and specific geometric parameters that optimize both formability and fatigue resistance locally.
2Shape
If the feed position of steel pipe during stretch reduction rolling is not optimized, then the inner peripheral shape deteriorates, but optimizing it requires precise control of seam position relative to rolling rolls
Solution Approach 1:
The patent applies parameter changes by establishing specific angular position parameters for the welded seam (0°±10° or 90°±10° relative to the rolling direction) and maintaining these parameters throughout the stretch reduction rolling process. By converting the complex positioning problem into simple angular parameter specifications, the patent achieves optimal inner peripheral shape without requiring complex real-time control systems.
3Productivity
If electric resistance welded steel pipe is used instead of steel bars, then productivity improves, but formability and fatigue resistance under bending and torsional stresses worsen
Solution Approach 1:
The patent applies parameter changes by optimizing multiple key parameters simultaneously: the welded seam positioning angle (0°±10° or 90°±10°), the r-value (1.0 or greater), and the wall thickness distribution (H/W ratio ≤ 0.10). These parameter optimizations enable electric resistance welded steel pipe to achieve formability and fatigue resistance comparable to steel bars while maintaining the productivity advantages of welded pipe 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 solution results in a steel pipe with enhanced formability and torsional fatigue resistance, suitable for automotive structural members, preventing galling and ensuring consistent performance under bending and torsional stresses.
Implementation Method 1
electric resistance welded steel pipe including a seam region and a base metal region, the seam region having a range of ±10° in a pipe circumferential direction with respect to an electric resistance welded seam
Implementation Method 2
stretch reduction rolling results in a change in an inner peripheral shape near an electric resistance welded seam of a steel pipe
Data Source
Figure 1~3
Figure 4(a)~4(b)
Figure 5~6
AI summary
An electric resistance welded steel pipe having excellent formability and torsional fatigue resistance is provided, and a method for manufacturing the same is provided. An electric resistance welded steel pipe 1 including a seam region 3 and a base metal region 6, the seam region 3 having a range of ±10 degrees in a pipe circumferential direction with respect to an electric resistance welded seam 2 formed in a pipe longitudinal direction, the base metal region 6 being a region other than the seam region 3, wherein the electric resistance welded steel pipe 1 has an r-value in the pipe longitudinal direction of 1.0 or greater, H (mm) and W (mm) satisfy formula (1) below, where H (mm) is a difference between Ts(MIN) (mm) and Tb(Ave) (mm) (Tb(Ave) - Ts(MIN)), Ts(MIN) (mm) is a minimum wall thickness value of the seam region 3, Tb(Ave) (mm) is an average wall thickness value of the base metal region 6, and W (mm) is an arc length of a pipe inner surface of the seam region 3, and Ts(MAX) (mm) and Tb(Ave) (mm) satisfy formula (2) below, where Ts(MAX) (mm) is a maximum wall thickness value of the seam region 3. H/W≤0.10 TsMAX/TbAve≤1.05