Types of arc in inert gas welding
The gas metal arc welding (MSG), optionally as an MIG (metal welding with inert gases, EN ISO 4063: Process 131) or MAG welding (metal welding with active, ie reactive gases, EN ISO 4063: Process 135), is an arc welding process in which the melting welding wire is continuously tracked by a motor with variable speed.
The wire is melted by the arc in different ways depending on the process variant and the welding parameters set. A distinction is made between different types of arcs.
Arc types
With increasing welding current and voltage, the forms of the material transition in MIG / MAG welding change and continuously merge, the boundaries are blurred. As the arc voltage rises, the drop volume increases and the material transition becomes short-circuit-free. If the arc length is too great, the arc will break after the material transition. The number of drops increases with increasing current strength. At the same time, their volume decreases.
Short arc
The arc length changes cyclically. This is associated with shifts in the operating point of the welding current and welding voltage. In the phase of droplet detachment, as the droplet approaches the melt, the arc voltage is reduced until the droplet passes into the weld pool. A short circuit occurs, the current increases with a delay according to the inductivity of the welding circuit up to the maximum short circuit current. The rate of increase in current of the power source largely determines the type of droplet detachment. After the arc is re-ignited, the voltage increases sharply. The welding current falls again and adjusts itself according to the position of the arc operating point on the power source characteristic. The course of the momentary welding current is essentially determined by the dynamic properties of the welding power source. During the drop short circuit, the voltage does not completely collapse, as the heated free length of wire has a significant, dynamically changing resistance.
Pulsed arc
When welding with a pulsed arc, an increased pulse voltage is regularly superimposed on a basic voltage, whereby a basic current and a pulsed current alternate with a given frequency and pulse time. During the basic current phase, the arc burns with low power, the filler metal is melted, the weld pool is kept liquid. During the impulse phase, a large drop forms, which is detached by the growing magnetic constriction ( pinch effect ). Depending on the wire diameter and electrode material, the setting values must be selected in such a way that a drop is generated and detached with each current pulse.
Pulse welding has become widely accepted today because of various advantages. The heat input can be reduced and controlled, thin sheets can be welded with thicker wires, the deposition rate is higher, and spatter can be greatly reduced. When welding thin sheet metal, it is particularly important to introduce as little heat as possible into the component because of the heat distortion. For this reason, various manufacturers of welding power sources have developed processes to reduce the welding power while maintaining the same deposition rate and to keep spatter formation low by using special pulse shapes and controlling the wire feed.
Individual evidence
- ↑ DIN 1910-100: 2008-02: Welding and related processes - Terms - Part 100: Metal welding processes with additions to DIN EN 14610: 2005.
- ↑ PanGas: Welding connects - welding, cutting and shielding gases , information sheet 099.7305.2012-11.V2.3000.UD ( Memento of the original from October 6, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked . Please check the original and archive link according to the instructions and then remove this notice.
