Induction Heating Coil Positioning for Rail Weld Residual Stress
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Solution Overview
Problem
Existing methods for stress-relief heat treatment of welded rails are insufficient in effectively decreasing tensile residual stress in the weld zone, leading to increased durability challenges.
Innovation Solution
A stress-relief heat treatment apparatus using induction heating coils arranged on the lateral face of the rail, separated from the welding center by 20 mm to 300 mm, to heat the periphery faster and suppress temperature increase at the weld zone, thereby reducing residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the periphery of the weld zone is heated by a burner at a slow heating velocity, then the heating process is simple and easy to control, but the temperature of the weld zone increases excessively and residual stress cannot be sufficiently decreased
Solution Approach 1:
The patent replaces the conventional burner-based thermal heating method with induction heating technology. This substitution enables precise control of heating velocity and location through electromagnetic fields, preventing excessive temperature increase in the weld zone while effectively reducing residual stress. The induction heating coil can be positioned at specific distances (20-300 mm) from the welding center to achieve optimal heating control.
Solution Approach 2:
The patent changes the heating velocity parameter by using induction heating instead of burner heating. The induction heating system can control the heating velocity to be within a specific range (2.0-5.0° C./s), which is faster than burner heating but prevents excessive temperature increase in the weld zone. This parameter change resolves the contradiction between heating effectiveness and temperature control.
2Productivity
If induction heating coil is placed close to the welding center, then heating efficiency is high, but the temperature of the weld zone increases excessively
Solution Approach 1:
The patent applies local quality by positioning the induction heating coil at a specific distance (20-300 mm) from the welding center rather than directly at the weld zone. This localized positioning allows the heating to be applied precisely to the periphery of the weld zone, maintaining heating efficiency while preventing excessive temperature increase in the critical weld area. The heating is concentrated where needed without affecting the weld center.
3Device complexity
If conventional burner heating is used, then equipment complexity is low, but heating velocity is slow and residual stress reduction is insufficient
Solution Approach 1:
The patent replaces the mechanical burner heating system with an induction heating system that uses electromagnetic fields. This substitution significantly increases heating velocity (controllable at 2.0-5.0° C./s) while maintaining reasonable equipment complexity. The induction heating coil and power source provide rapid and controllable heating that effectively reduces residual stress within practical timeframes.
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 apparatus effectively decreases residual stress in the weld zone, enhancing rail durability by controlling the heating process to offset uneven stress distribution.
Implementation Method 1
an induction heating coil, wherein the induction heating coil is arranged at a lateral face of a web of the rail while being separated from a welding center of the rail by 20 mm to 300 mm in a longitudinal direction of the rail
Data Source
AI summary
A stress-relief heat treatment method for stress-relief heat-treating a rail which is welded includes arranging at least one pair of an induction heating coil to face the rail at both sides of a welding center along the longitudinal direction of the rail while being separated from the welding center of the rail by 20 mm to 300 mm in a longitudinal direction of the rail and being an axial direction of the induction heating coil parallel to the longitudinal direction of the rail. The method further includes flowing a current to the induction heating coil arranged at one side of the welding center and to the induction heating coil arranged at the other side of the welding center being opposite to each other, and induction heating the rail to a heating temperature of 400° C. or higher and 750° C. or lower.