Arc Welded Joint Geometry for Fatigue and Corrosion Resistance
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Solution Overview
Problem
Existing arc welded joints in automobiles face challenges in maintaining fatigue strength and resisting corrosion, particularly due to the formation of welding slags which reduce the effectiveness of corrosion resistance and lead to a decrease in fatigue strength.
Innovation Solution
The solution involves specifying a flank angle of 100° or more at the weld toe and controlling the slag-covered area ratio to 50% or less, using a shielding gas with a specific composition and short-circuiting the welding wire and steel sheets during the welding process to reduce stress concentration and slag formation, thereby enhancing fatigue properties and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding slags are reduced to improve corrosion resistance, then corrosion resistance is improved, but fatigue strength may be compromised due to changes in weld shape
Solution Approach 1:
The invention changes the geometric parameters of the weld toe by controlling the flank angle to be 100° or more, which fundamentally alters the stress distribution pattern. This parameter change allows the weld to maintain high fatigue strength while accommodating reduced slag coverage, as the optimized geometry reduces stress concentration regardless of slag presence
Solution Approach 2:
The invention applies local quality control by specifically optimizing the flank angle region (the local geometry at the weld toe) while allowing other parts of the weld to have varying slag coverage. This localized geometric optimization ensures that the critical stress concentration area has favorable shape characteristics independent of slag coverage
2Reliability
If electrodeposition coating is applied to improve corrosion resistance, then corrosion resistance is improved, but welding slags inhibit the coating process
Solution Approach 1:
The invention extracts or removes the harmful element (welding slags) from the weld surface by optimizing welding parameters and geometry, thereby eliminating the barrier that prevents electrodeposition coating adhesion. This extraction approach allows the coating process to proceed effectively on the weld surface
3Strength
If high strength steel sheets are used to improve member strength, then static tensile strength is improved, but fatigue strength in corrosive environments deteriorates
Solution Approach 1:
The invention changes the geometric parameter of the weld toe (flank angle ≥100°) to create a more favorable stress distribution pattern. This geometric parameter change compensates for the reduced fatigue resistance of high strength steel in corrosive environments by minimizing stress concentration at the weld toe, thereby maintaining high fatigue strength
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 results in an arc welded joint with improved fatigue strength and reduced corrosion, maintaining the weld shape even in corrosive environments, effectively addressing the limitations of previous techniques.
Implementation Method 1
a weld formed by arc welding of an overlap of at least two steel sheets
Implementation Method 2
using a shielding gas including Ar gas and an oxidizing gas
Data Source
AI summary
An arc welded joint and an arc welding method. The arc welded joint has a weld formed by arc welding of an overlap of at least two steel sheets. The weld has a specified flank angle θ. In a region extending 2.0 mm from a bead toe of the weld in a weld metal direction and also extending 2.0 mm from the bead toe in a base material direction, a slag-covered area ratio is 50% or less.