Arc-Welding Method for Galvanized Steel Porosity Control
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Solution Overview
Problem
Conventional arc-welding methods for galvanized steel sheets fail to effectively release zinc vapor, leading to increased porosity and spatter generation due to high molten pool thickness and zinc coating weight, which hinders penetration and results in blow holes and pits, affecting weld strength.
Innovation Solution
An arc-welding method and apparatus that alternately switch between short-circuit and arc states by controlling welding current and wire-feeding speed, reducing current during short-circuit detection and supplying pulse currents with higher peak values, and periodically reversing wire-feeding speed to expose the root part and facilitate zinc vapor release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional arc-welding methods are used on galvanized steel sheets, then welding can be performed, but zinc vapor cannot be released sufficiently leading to porosity and blow holes
Solution Approach 1:
The patent applies periodic action by alternating between short-circuit transfer welding and pulse welding in a cyclic manner. During short-circuit transfer welding, the wire feeds forward to build molten pool. During pulse welding, the wire feeds backward and high-current pulses are applied to generate strong arc force that pushes molten metal upward, exposing the root part and enabling zinc vapor release. This periodic alternation creates rhythmic molten pool agitation that effectively expels zinc vapor without compromising weld quality
Solution Approach 2:
The patent implements dynamics by making the wire-feeding speed variable rather than constant. The wire feed speed alternates between forward feeding during short-circuit transfer and backward feeding during pulse welding. Additionally, the arc force is dynamically adjusted through high-current pulses that create strong upward pressure on the molten pool, enabling real-time control of molten pool behavior to facilitate zinc vapor release
2Strength
If the thickness of objects to be welded is 2.0 mm or greater, then penetration is increased, but the thickness of molten pool increases hindering zinc vapor release
Solution Approach 1:
For thick workpieces (2.0 mm or greater), the patent uses periodic alternation between short-circuit transfer welding (which provides deep penetration) and pulse welding with backward wire feeding (which creates strong upward arc force). This periodic cycle allows the molten pool to periodically agitate and expose the root part, enabling zinc vapor release even in thick materials where continuous welding would trap vapor
Solution Approach 2:
The patent applies preliminary action by performing backward wire feeding and high-current pulse application during the pulse welding phase, which prepares the molten pool by generating strong upward arc force before the next short-circuit transfer phase. This preliminary agitation of the molten pool creates conditions favorable for zinc vapor release during the subsequent penetration phase
3Quantity of substance
If zinc coating weight is greater than 45 g/m2, then more zinc vapor is generated, but release of zinc vapor is hindered increasing porosity
Solution Approach 1:
The patent converts the harmful effect of high zinc vapor generation from thick galvanized layers into a beneficial process feature. By using backward wire feeding combined with high-current pulses, the strong upward arc force generated actually utilizes the zinc vapor generation to create more vigorous molten pool agitation and metal upward flow, which enhances zinc vapor release rather than allowing it to trap
Solution Approach 2:
The periodic alternation between short-circuit transfer welding and pulse welding with backward feeding creates rhythmic cycles that allow accumulated zinc vapor from high-coating-weight materials to be periodically expelled through strong arc force, preventing porosity even when large amounts of zinc vapor are generated
4Reliability
If pulse welding with backward feed is used to expose root part, then zinc vapor release is improved, but welding time increases
Solution Approach 1:
The patent optimizes the periodic cycle by carefully balancing the duration of short-circuit transfer welding (which provides penetration) with the duration of pulse welding with backward feeding (which enables zinc vapor release). This optimized periodic action achieves effective zinc vapor expulsion while minimizing the total welding cycle time
Solution Approach 2:
The patent applies partial action by using brief high-current pulses during the pulse welding phase rather than continuous high current. The backward wire feeding is also applied partially during specific portions of the cycle, providing just enough molten pool agitation and root exposure to enable zinc vapor release without unnecessarily extending the 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 effectively suppresses porosity and spatter generation by ensuring zinc vapor release from the molten pool, enhancing weld quality and strength by exposing the root part and reducing the thickness of the molten pool.
Implementation Method 1
any porosity 28 generated from the galvanized layer in the molten pool reaches the surface of the molten pool because of the flow of the molten pool and the buoyancy of porosity 28
Implementation Method 2
First period TL is a period of a current waveform in which first average arc force FL acts on the molten pool. Second period TH is a period of a current waveform in which second average arc force FH, which is larger than first average arc force FL, acts on the molten pool
Data Source
AI summary
An arc-welding method in welding by repeating a short circuit and an arc. When the sign of opening of the short circuit is detected, the welding current is reduced from a first current value at the detection of the sign to a second current value, which is lower than the first current value. When the opening of the short circuit is detected, a pulse current having a peak value higher than the first current value is supplied at a plurality of times in the arc period. This suppresses porosities and spatters when galvanized steel sheets are welded.