Undercarriage Weld Metal Composition for Strength and Corrosion Resistance
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Solution Overview
Problem
Existing techniques for enhancing corrosion resistance in automobile undercarriage parts with welded joints struggle to maintain high strength, particularly in joints requiring a tensile strength of 780 MPa or higher.
Innovation Solution
The development of an automobile undercarriage part with a welded joint that utilizes a specific chemical composition for the weld metal, including C, Si, Mn, Al, Ti, and other elements, to achieve both excellent strength and corrosion resistance. This composition is carefully balanced to satisfy specific formulas and ensure appropriate slag distribution, thereby suppressing red rust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Si content is reduced to suppress insulating Si slag formation and improve corrosion resistance, then corrosion resistance is improved, but weld metal strength cannot be secured
Solution Approach 1:
The patent changes the chemical composition parameters of the weld metal by precisely controlling the content ranges of Si (0.03-0.80%), Mn (1.50-3.00%), Ti (0.03-0.30%), and Al (0.03-0.30%). This parameter optimization allows the weld metal to achieve both high strength (780 MPa or higher) and good corrosion resistance by balancing the deoxidation effect with strength enhancement, preventing excessive Si slag formation while maintaining adequate strength.
Solution Approach 2:
The patent creates a composite chemical composition system in the weld metal that combines multiple elements (Si, Mn, Ti, Al) in specific proportions. This composite approach allows the synergistic effects of different elements: Si and Mn for deoxidation and strength, Ti and Al for slag control and strength enhancement, achieving both high strength and corrosion resistance simultaneously.
2Shape
If painting is performed on welded undercarriage parts, then appearance is improved, but painting defects occur on weld metal surface leading to poor appearance and deteriorated corrosion resistance
Solution Approach 1:
The patent applies preliminary action by optimizing the weld metal composition before painting to prevent painting defects. By controlling Si content (0.03-0.80%) and adding Ti (0.03-0.30%) and Al (0.03-0.30%), the weld metal surface quality is improved in advance, reducing insulating slag formation and creating a surface that is more suitable for painting adhesion, thereby preventing subsequent painting defects and corrosion issues.
3Strength
If arc welding is performed to join steel members, then structural integrity is achieved, but red rust occurs in joint portions due to poor corrosion resistance
Solution Approach 1:
The patent changes the chemical parameters of the weld metal to achieve both structural integrity and corrosion resistance. By optimizing C (0.02-0.30%), Si (0.03-0.80%), Mn (1.50-3.00%), Ti (0.03-0.30%), and Al (0.03-0.30%) content, the weld metal achieves high strength (780 MPa or higher) while reducing insulating slag formation that causes red rust, thereby resisting corrosion in joint portions.
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 proposed solution effectively achieves excellent strength and corrosion resistance in the weld metal of automobile undercarriage parts, even in high-strength applications, by controlling the chemical composition and slag distribution in the welded joints.
Implementation Method 1
slag in a toe portion of the fillet weld satisfies a formula (4): [Ti content on slag surface]>[Si content on slag surface]
Data Source
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).[Al]+[Ti]>0.05 Formula (1A)[Ti]/[Al]>0.9 Formula(1B)7×[Si]+7×[Mn]−112×[Ti]−30×[Al]≤12 Formula (2)2.0<[Si]+[Mn] Formula (3)[Ti content on slag surface]>[Si content on slag surface] Formula (4).