Undercarriage Weld Metal Composition to Suppress Red Rust
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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 carefully controlled to include specific ranges of C, Si, Mn, Al, and Ti, with balanced coexistence of Al and Ti, and optimized welding conditions such as nozzle diameter, gas flow rate, and distance between nozzle and base metal to prevent red rust, ensuring excellent strength and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Si content in weld metal is increased to improve strength, then strength is improved, but insulating Si slag forms causing painting defects and red rust
Solution Approach 1:
The invention changes the chemical composition parameters of the weld metal by strictly controlling Si content to 0.04-0.20% and Mn content to 0.50-3.00%, while also controlling the ratio of Si/Mn to be 0.08-0.80. This parameter optimization prevents excessive Si slag formation while maintaining adequate strength, thereby eliminating painting defects and red rust issues.
Solution Approach 2:
The invention creates a composite chemical composition system in the weld metal that balances multiple elements (C, Si, Mn, Al, Ti, etc.) rather than relying on a single element. This composite approach allows the weld metal to achieve both strength and corrosion resistance by synergistic interaction of elements, preventing Si slag formation while maintaining mechanical properties.
2Ease of manufacture
If arc welding is performed on steel members to manufacture undercarriage parts, then manufacturing capability is achieved, but corrosion resistance deteriorates due to painting defects and red rust in joint portions
Solution Approach 1:
The invention applies preliminary action by optimizing the weld metal composition before welding occurs. By pre-controlling the chemical composition (Si: 0.04-0.20%, Mn: 0.50-3.00%, Si/Mn ratio: 0.08-0.80), the welding process inherently produces slag-free welds that are ready for painting without subsequent corrosion issues, eliminating the need for post-weld treatment.
Solution Approach 2:
The invention changes the chemical parameters of the welding consumable to achieve both manufacturability and corrosion resistance. By adjusting Si and Mn content and their ratio, the weld metal produces adequate slag that does not interfere with painting, thereby maintaining both ease of manufacture and long-term corrosion resistance.
3Shape
If painting is performed on welded parts to improve appearance, then appearance is improved, but corrosion resistance deteriorates when painting defects occur
Solution Approach 1:
The invention applies preliminary anti-action by preventing the formation of insulating Si slag at the source through controlled composition. By limiting Si content to 0.04-0.20% and controlling the Si/Mn ratio to 0.08-0.80, the weld metal inherently avoids creating surface defects that would cause painting failures, thereby protecting against future corrosion before painting is even applied.
Solution Approach 2:
The invention changes the chemical composition parameters to create a weld metal that is inherently paint-friendly. By optimizing Si and Mn content and their ratio, the weld surface achieves adequate smoothness and chemical stability, enabling successful painting that provides both appearance and corrosion protection.
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 approach results in weld metals with enhanced strength and corrosion resistance, as evidenced by the suppression of red rust in cyclic tests, maintaining integrity under tensile loads and environmental exposure.
Implementation Method 1
gas shielded arc welding or the like
Implementation Method 2
performing arc welding on a plurality of steel members using welding wires
Implementation Method 3
suppressing the formation of insulating Si slag
Implementation Method 4
corrosion resistance after painting in a weld or a vicinity thereof
Data Source
Figure 1~2
Figure 3
AI summary
An automobile undercarriage part of the present invention has a welded joint formed by base steel plate, wherein the chemical composition of a weld metal contains, with respect to a total mass of the weld metal, by mass%, C: 0.02% to 0.30%, Si: 0.10% to less than 1.0%, Mn: 1.2% to 3.0%, 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%, the following formula (1A), formula (1B), formula (2), and formula (3) are satisfied, and slag in a toe portion of the fillet weld satisfies a formula (4). A1+Ti>0.05 Ti/A1>0.9 7×Si+7×Mn−112×Ti−30×A1≤12 2.0<Si+Mn Ticontentonslagsurface>Sicontentonslagsurface