Zn-Coated Steel Weld Bead Geometry for Blowhole-Tolerant Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The generation of blowholes during arc welding of hot dip Zn-based alloy coated steel sheets leads to reduced weld strength, particularly in heavy-weight sheets with excellent corrosion resistance, where the pulsed arc welding process does not completely inhibit blowhole formation.
Innovation Solution
The solution involves setting the cross-sectional width and blowhole occupancy of the weld bead within specific ranges (2T≤W≤6T and Br≤50%) during pulsed arc welding, ensuring the weld bead has adequate shear strength and corrosion resistance, using a pulsed arc welding process with appropriate welding conditions to control the formation of the weld bead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot dip Zn-based alloy coated steel sheets are arc-welded, then the sheets can be joined together, but blowholes are excessively generated and weld strength is reduced
Solution Approach 1:
The patent applies pulsed arc welding instead of continuous arc welding. The welding current is supplied in pulses with peak current (IP) and base current (IB) alternating, which periodically stirs the molten pool and presses it down to become thin, facilitating discharge of Zn vapor and reducing blowhole generation
Solution Approach 2:
The patent optimizes specific welding parameters including peak current (IP), base current (IB), peak period (PP), and pulse period (PF) to control the welding process. By adjusting these parameters, the molten pool behavior is controlled to reduce blowhole formation while maintaining weld strength
2Reliability
If heavy-weight hot dip Zn-based alloy coated steel sheets are used for long-term durability, then corrosion resistance is improved, but the amount of Zn vapor generated increases and blowholes are excessively generated
Solution Approach 1:
The pulsed arc welding process periodically stirs the molten pool during welding of heavy-weight coated sheets. This periodic stirring action facilitates the discharge of Zn vapor generated from heavy coating, reducing blowhole formation while maintaining the corrosion resistance benefits of heavy coating
Solution Approach 2:
The patent establishes a relationship between coating weight and welding parameters. By measuring or determining the coating weight, appropriate welding parameters (IP, IB, PP, PF) can be selected to optimize the welding process for that specific coating weight, ensuring both corrosion resistance and reduced blowhole generation
3Object-generated harmful factors
If pulsed arc welding process is used to inhibit spatters and blowholes, then blowhole generation is reduced, but blowholes cannot be completely inhibited in heavy-weight sheets
Solution Approach 1:
The patent optimizes the welding parameters (IP, IB, PP, PF) specifically for pulsed arc welding to achieve the best balance between reducing blowholes and maintaining weld bead strength. The optimized parameters ensure that even in heavy-weight sheets, blowhole generation is minimized while weld strength is maintained
Solution Approach 2:
The patent accepts that some blowholes may still occur in heavy-weight sheets but controls them to an acceptable level. The focus is on reducing blowhole generation to a程度 that maintains weld bead strength, rather than attempting to completely eliminate all blowholes
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 a welded member with enhanced shear strength and corrosion resistance, preventing the weld bead from breaking prematurely and maintaining designed joint strength, even with the presence of some blowholes.
Implementation Method 1
the hot dip Zn-based alloy coated steel sheets are arc-welded to each other
Implementation Method 2
a pulsed arc welding process in which a welding wire is used as an electrode
Implementation Method 3
a molten pool (which is a weld bead part before solidification) is stirred by a pulsed arc, and the molten pool is pressed down to become thin
Implementation Method 4
The boiling point of Zn (approximately 906° C.) is lower as compared with the melting point of Fe (approximately 1538° C.), and therefore Zn vapor is generated during arc welding
Implementation Method 5
a weld bead which is a part obtained when a part of a base material and a deposited metal melt together during welding and then solidify by cooling
Data Source
AI summary
A welded member includes a hot dip Zn-based alloy coated steel sheet as a base material and has excellent corrosion resistance and weld bead shear strength. In the welded member in which a lower sheet and an upper sheet, which are hot dip Zn-based alloy coated steel sheets, are stacked and arc-welded together, a weld bead is formed so that a cross-sectional width W satisfies the following formula 2T≤W≤6T, and a blowhole occupancy Br represented by the following formula becomes not more than 50%: Br=(Σdi/L)×100, where T represents a thickness of the hot dip Zn-based alloy coated steel sheet, di represents a length of an i-th blowhole observed in X-ray radiography, and L represents a length of the weld bead.