Undercarriage Fillet Weld Composition for Rust-Resistant Joint Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Automobile undercarriage parts with welded joints face challenges in achieving both high strength and corrosion resistance, particularly in suppressing red rust at weld metal joints, which is exacerbated by painting defects and the formation of insulating slag.
Innovation Solution
The composition of the weld metal is optimized with specific ranges of C, Si, Mn, Al, Ti, P, S, Cu, Cr, Nb, V, Mo, Ni, and B to form a fillet weld with a chemical composition that satisfies certain formulas, ensuring excellent strength and corrosion resistance, including the coexistence of Al and Ti to suppress red rust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Si content is reduced to suppress insulating slag formation, then corrosion resistance after painting is improved, but weld metal strength deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Si content range (0.01-0.10%) and establishing specific relationships between multiple alloying elements (Mn: 1.50-3.00%, Al: 0.03-0.30%, Ti: 0.05-0.50%) to achieve both low slag formation and sufficient weld strength. This resolves the contradiction by finding an optimal parameter window where both corrosion resistance and strength requirements are met simultaneously.
Solution Approach 2:
The patent creates a composite chemical composition system where multiple elements work synergistically: Mn provides deoxidation and strength, Al and Ti control slag formation and morphology, and C provides base strength. This composite approach allows the weld metal to achieve both low Si content (for corrosion resistance) and high overall strength through the combined effects of multiple alloying elements.
2Strength
If welding is performed to join steel members, then structural strength is improved, but painting defects occur on weld metal surface
Solution Approach 1:
The patent changes the chemical composition parameters of the welding wire to produce weld metal with specific properties: low Si content (0.01-0.10%) reduces slag formation, controlled Mn (1.50-3.00%) ensures deoxidation and strength, and specific C content (0.15-0.40%) provides adequate base strength. These parameter changes result in weld surfaces that are free from painting defects while maintaining joint strength.
3Reliability
If arc welding is performed on steel members, then structural integrity is improved, but red rust occurs at weld joints
Solution Approach 1:
The patent applies parameter changes by controlling the chemical composition to suppress red rust: low Si content (0.01-0.10%) minimizes insulating slag that would trap moisture, adequate Mn (1.50-3.00%) provides deoxidation and corrosion resistance, and the specific C content (0.15-0.40%) ensures structural integrity. These parameter adjustments eliminate red rust while maintaining structural integrity.
Solution Approach 2:
The patent converts the potential harm of welding (which creates susceptible zones for corrosion) into a benefit by using the welding process to create a homogeneous metal composition with optimized alloying elements. The weld metal becomes more corrosion-resistant than the base metal through controlled deoxidation by Mn and reduced slag formation, turning the weld zone from a vulnerability into a protective feature.
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 optimized weld metal composition effectively enhances both the tensile strength and corrosion resistance of the weld metal, preventing red rust and ensuring the weld metal fractures from the base metal during tensile tests, while maintaining a stable bead shape and cracking resistance.
Implementation Method 1
it is considered that corrosion resistance after painting in a weld formed by gas shielded metal arc welding or a vicinity thereof can be enhanced by suppressing the formation of insulating Si slag
Implementation Method 2
Automobile undercarriage parts are usually manufactured by performing lap welding on a plurality of steel materials through gas shielded arc welding or the like
Data Source
AI summary
An automobile undercarriage part of the present invention is an automobile undercarriage part including a welded joint in which a first steel sheet and a second steel sheet are overlapped and a fillet weld is formed between an end surface of the first steel sheet and a surface of the second steel sheet, in which a chemical composition of a weld metal that forms the welded joint contains, with respect to a total mass of the weld metal, by mass %, C: 0.02% to 0.20%, Si: more than 0% to less than 0.10%, Mn: 0.3% to 2.0%, Al: 0.002% to 0.30%. Ti: 0.005% to 0.30%, P: more than 0% to 0.015%, and S: more than 0% to 0.030%, and the following formula (1) and formula (2) are satisfied.[Al]+[Ti]>0.05 Formula (1)7×[Mn]−112×[Ti]−30×[Al]≤4.0 Formula (2)