Arc Welded Joint Structure with Zn Plated Steel Sheets
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Solution Overview
Problem
During arc welding of Zn-based plated steel sheets, the development of blowholes and pits in the starting and terminal end portions leads to reduced joining strength and impaired appearance, as existing methods fail to effectively reduce blowhole occupancy throughout the entire welding section.
Innovation Solution
The implementation of an inter-sheet gap in a predetermined range, combined with tailored welding conditions such as varying welding speed, heat input, and voltage in the starting and terminal end portions, and stopping the electric arc at the terminal end portion, facilitates gas discharge and reduces blowhole development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an inter-sheet gap is provided to allow gas escape, then blowhole development is reduced, but welding strength and appearance are impaired in starting and terminal end portions
Solution Approach 1:
The patent applies different welding conditions to different regions of the weld bead. The starting end portion and terminal end portion use different welding speeds and heat inputs compared to the central portion. This local differentiation allows optimal blowhole control at endpoints while maintaining overall weld quality
Solution Approach 2:
The patent dynamically adjusts welding parameters during the welding process. By varying welding speed and heat input based on position (starting end, central, terminal end), the system adapts to local conditions to prevent blowholes while maintaining strength
2Productivity
If welding speed is increased to improve productivity, then welding efficiency improves, but blowhole formation increases due to reduced gas escape time
Solution Approach 1:
The patent uses periodic variation in welding speed throughout the welding process. The speed is adjusted in different segments (starting end, central, terminal end) to create optimal conditions for gas escape at each location while maintaining overall productivity
Solution Approach 2:
The patent changes welding parameters (speed, heat input) based on position. By modifying these parameters in the starting and terminal end portions compared to the central portion, the system controls blowhole formation without sacrificing overall welding efficiency
3Object-affected harmful factors
If heat input is increased to reduce cooling rate and prevent blowholes, then blowhole development decreases, but welding time increases
Solution Approach 1:
The patent applies higher heat input locally at the starting end and terminal end portions where blowholes are most problematic, while using standard heat input in the central portion. This localized approach prevents blowholes without unnecessarily extending overall welding time
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 significantly decreases blowhole occupancy in the starting and terminal end portions, enhancing the welding strength and appearance by allowing effective gas escape and slowing down solidification, thereby reducing the overall blowhole formation in the weld bead.
Implementation Method 1
heat is applied while a welding wire is supplied between the Zn-based plated steel sheets which are materials to be welded. Thereby, they are joined. Consequently, the Zn-based plated steel sheets as materials to be welded are exposed to heat generated by electric arc during arc welding of them
Implementation Method 2
Zn vapor may be generated during welding because the boiling point of Zn (906°C) in the plating layers is lower than that of Fe in the steel sheets. The vapor may enter into a welding section when it is in a molten state, and may be trapped after it is solidified to create cavities (blowholes) inside the welding section
Implementation Method 3
Provision of a space (gap) between welding members is effective. Patent Document 1 proposes a method in which a gap of about 0.5 mm is provided between overlaid members to be welded, thereby allowing a generated gas to escape to the opposite side of a welding section
Implementation Method 4
The vapor may enter into a welding section when it is in a molten state, and may be trapped after it is solidified to create cavities (blowholes) inside the welding section
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
The present application realtes to an arc welded joint assembly (8) obtained by a method of arc welding Zn-based plated steel sheets (1, 2), in which a blowhole occupancy over the entirety of the welding length is less than 30%. This arc welding method sets the gap between plates (1, 2) to 0.2 - 1.5 mm and includes a first step for moving a welding means from a welding initiation point at a first welding speed and performing welding by applying a first welding heat input, a second step following the first step for moving the welding means at a second welding speed and performing welding by applying a second welding heat input, and a third step following the second step for stopping the movement of the welding means and performing welding for 0.1 - 2 seconds at that stopped position. The first step includes welding performed on a welding unit under conditions wherein the first welding speed is less than the second welding speed and the first welding input heat exceeds the second welding input heat. In the third step, welding is performed at a welding current and a welding voltage lower than those in the second step.