Ti Welding Wire Surface Composition for Stable Long MIG Arcs
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Solution Overview
Problem
Long-time MIG welding of Ti-based materials experiences unstable arcs due to non-uniform distribution of metal compounds, leading to welding defects in multi-layer or extensive welding processes.
Innovation Solution
A wire rod with an oxygen-enriched surface layer and strategically formed cracks filled with alkali or alkaline earth metal compounds, ensuring a specific area ratio and distribution for improved arc stability, where the metal compounds are present in concentrations of 0.002 to 0.050 mass % and the cracks have an extension depth of 20 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-purity inert gas such as pure Ar gas is used as shielding gas, then oxidation of bead surface is prevented and ductility is maintained, but cathode spot during arc discharge becomes unstable
Solution Approach 1:
The invention applies local quality by creating an oxygen-enriched layer only on the surface of the wire rod, while the interior remains as high-purity Ti or Ti alloy. This localized oxygen concentration gradient allows the surface to provide arc stability through oxide formation, while the interior maintains the high ductility characteristic of pure Ti, thus resolving the contradiction between cathode spot stability and welded portion ductility.
Solution Approach 2:
The invention changes the oxygen concentration parameter from uniform (conventional) to non-uniform with an oxygen-enriched surface layer. This parameter change allows the surface to have high oxygen content for arc stability while the bulk material maintains low oxygen content for ductility, resolving the contradiction between these two requirements.
2Ease of operation
If groove is formed on surface of welding wire and metal compound of alkali metal or alkaline earth metal is held in groove, then feedability and arc stability are improved, but arc becomes unstable during long-time welding
Solution Approach 1:
The invention extracts the metal compound from the groove structure and redistributes it through the oxygen-enriched layer across the entire wire rod surface. This extraction from localized grooves and redistribution ensures uniform availability of arc-stabilizing elements during long-time welding, preventing the arc instability that occurs when metal compound is confined to grooves.
Solution Approach 2:
The oxygen-enriched layer is formed in advance on the wire rod surface, creating a reservoir of oxygen that will gradually release during welding. This preliminary action ensures that arc stability is maintained throughout long-time welding processes, as the oxygen is already distributed and ready to form stabilizing oxides when needed.
3Stability of the object's composition
If oxygen-containing gas is used as shielding gas, then arc stability is improved, but bead surface is oxidized and ductility of welded portion is lowered
Solution Approach 1:
The oxygen-enriched layer acts as an intermediary between the high-purity inert gas shielding environment and the arc discharge process. It provides the necessary oxygen for arc stability locally at the wire surface while allowing the bulk material to remain protected from oxidation by the inert gas shield, thus resolving the contradiction between arc stability and prevention of oxidation.
Solution Approach 2:
The invention creates a local oxygen-enriched environment only at the wire rod surface where it is needed for arc stability, while the rest of the welding system operates with high-purity inert gas to prevent oxidation. This spatial differentiation of oxygen concentration resolves the contradiction between needing oxygen for arc stability and avoiding oxidation for ductility.
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 solution stabilizes the arc during long-time welding, preventing welding defects and ensuring reliable weld quality over extended lengths, as demonstrated by the evaluation of arc stability in various examples.
Implementation Method 1
Oxygen in the oxygen-enriched layer can stabilize generated arc
Implementation Method 2
Oxygen in the oxygen-enriched layer can stabilize generated arc and at the same time lower surface tension of a leading end of the wire rod that is melted, so that generated droplets are easily released from the leading end of the wire rod
Implementation Method 3
since a boiling point and an ionization voltage of the alkali metal or the alkaline earth metal are lower than a melting point and the ionization voltage of Ti, the alkali metal or the alkaline earth metal is present as metal vapor ionized in a field of the generated arc before a base material (Ti or Ti alloy) is melted by arc heat
Implementation Method 4
the alkali metal or the alkaline earth metal is present as metal vapor ionized in a field of the generated arc
Data Source
AI summary
This wire rod for forming a molten metal is composed of Ti, or a Ti alloy, has an oxygen-enriched layer on a surface thereof, and contains a metal compound having at least one metal selected from the group consisting of an alkali metal and an alkaline earth metal such that the total mass of the alkali metal and/or alkaline earth metal is set to 0.002-0.050 mass % with respect to the total mass of the wire rod. Cracks filled with the metal compound are formed on the surface, and the area proportion of the cracks is 4-25%.