Dual-Frequency Spot Welding Equipment for High-Tension Steel
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Solution Overview
Problem
Existing spot welding equipment struggles to efficiently heat the outer peripheral region of nuggets in metallic materials, particularly in high-tension steel plates, due to the limited space around the electrodes, making it difficult to achieve stable strength and toughness in welds.
Innovation Solution
The equipment employs a dual-frequency heating system where a low-frequency power source and a high-frequency power source are used in conjunction with electrodes, allowing independent control of heating regions within the nugget and its periphery, enabling efficient heating of the outer periphery using the high-frequency power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-tension steel plates are used to reduce vehicle weight and enhance strength, then the strength of the base material increases, but the spot-weld region becomes extremely hard and brittle, making it difficult to obtain desired strength stably
Solution Approach 1:
The invention applies preliminary heating to the outer peripheral region of the nugget before or during the spot welding process. This pre-heating prevents the weld region from becoming excessively hard and brittle by controlling the thermal history, thereby maintaining stable weld strength while using high-tension steel plates with enhanced base material strength
Solution Approach 2:
The invention changes the thermal parameters by applying localized heating to the outer peripheral region of the nugget. This creates a controlled temperature distribution that modifies the microstructure and hardness of the weld region, preventing brittleness while maintaining the high strength of the base material
2Reliability
If tempering is performed by post-energization using existing welding equipment, then the effect of tempering can be achieved, but the process time per stroke exceeds the one-second limit required for vehicle assembly
Solution Approach 1:
The invention performs the tempering effect during or immediately after the welding process itself, rather than as a separate post-processing step. By applying controlled heating to the outer peripheral region during the welding cycle, the tempering effect is achieved within the one-second process time limit
Solution Approach 2:
The invention merges the welding process and the tempering process into a single operation. The heating means is integrated into the welding equipment, allowing simultaneous or sequential execution of welding and tempering within the same time cycle, thereby achieving both functions without extending the process time
3Shape
If the current density of the welded region decreases as the energized area increases after nugget formation, then the nugget can grow to the required size, but efficient heating cannot be caused in a short time
Solution Approach 1:
The invention applies heating locally to the outer peripheral region of the nugget rather than distributing energy uniformly across the entire welded area. This localized heating approach maintains high current density in the target region, enabling efficient heating and rapid tempering while the nugget grows to the required size
Solution Approach 2:
The invention segments the heating function by separating the heating of the nugget core (which occurs through resistive heating during welding) from the heating of the outer peripheral region (which occurs through the integrated heating means). This segmentation allows independent control of heating in different regions, maintaining efficiency while achieving the required nugget size
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 allows for rapid and flexible heat treatment of the outer peripheral region of spot welds, improving the strength and toughness of welds while maintaining the efficiency of the welding process.
Implementation Method 1
heating is performed by applying electric power from a low-frequency power source and a high-frequency power source to metallic materials 9
Implementation Method 2
A large current on the order of kA is then fed to the electrodes 52 while the pressurized state is maintained to melt the compressed portion of the steel plates 50 instantaneously by Joule heat
Data Source
AI summary
A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.