Spot Welding Electrode Speed Control to Prevent Splash and LME
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Solution Overview
Problem
The increase in nugget diameter during spot welding leads to local overheating and melting of steel sheets, resulting in splash and a decrease in weld quality, which in turn reduces joint strength and increases the risk of liquid metal embrittlement (LME) cracking.
Innovation Solution
Limiting the speed at which the electrodes approach each other during spot welding to 12.0 mm/s or slower, from the start of energization to the end of force maintenance, to prevent excessive indentation and splash, allowing the nugget to solidify before strong pressure is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the nugget diameter is increased to improve joint strength, then the welding strength is improved, but local overheating and splash occur causing a decrease in weld quality
Solution Approach 1:
The electrode approach speed is dynamically adjusted during the welding process, specifically limited to 12.0 mm/s or slower during the period from start of energization to end of energization. This dynamic speed control prevents excessive indentation and splash while allowing the nugget to solidify before strong pressure is applied, thereby maintaining both joint strength and weld quality
Solution Approach 2:
The invention changes the parameter of electrode approach speed from a constant or high value to a controlled value of 12.0 mm/s or slower during critical welding phases. This parameter change allows the nugget to solidify before strong pressure is applied, preventing splash and indentation while maintaining large nugget diameter for high joint strength
2Productivity
If the electrode approach speed is increased to improve productivity, then the welding speed is improved, but large indentation and splash occur reducing joint strength
Solution Approach 1:
The electrode approach speed is dynamically controlled at 12.0 mm/s or slower during the critical period from start of energization to end of energization, and also during the period from end of energization to end of force maintenance time. This dynamic speed limitation prevents large indentation and splash that would reduce joint strength, while still maintaining acceptable welding productivity
3Ease of operation
If the electrode approach speed is not limited, then the welding process is simple and fast, but the nugget does not solidify before pressure is applied causing splash and indentation
Solution Approach 1:
A specific parameter limit of 12.0 mm/s is imposed on the electrode approach speed during critical welding phases. This parameter change ensures the nugget solidifies before strong pressure is applied, preventing excessive indentation while maintaining relatively simple operation through a clear speed threshold
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 reduces indentation and splash, enhancing the strength of the welded joint and preventing LME cracking in galvanized steel sheets, even when larger nugget diameters are formed.
Implementation Method 1
overlapping surfaces of steel sheets are heated and melted by energization heating using the electrodes
Implementation Method 2
clamping the plurality of steel sheets between a pair of electrodes, and energizing the plurality of steel sheets while pressurizing the plurality of steel sheets
Data Source
AI summary
This spot welding device is a spot welding device for performing spot welding on a plurality of steel sheets overlapping with each other by clamping the plurality of steel sheets between a pair of electrodes, and energizing the plurality of steel sheets while pressurizing the plurality of steel sheets, in which a speed at which the pair of electrodes approach each other is limited to at least 12.0 mm/s or slower during a period from start of the energization to end of the energization.