departmental bulletin paper

Departmental Bulletin Paper

Text

Transactions of JWRI. 2011, 40(1), p. 25-29

Numerical Model of Gas Metal Arc with Metal Vapor for Heat Source in Welding

English

Text

2011-06

In gas metal arc (GMA) welding, an arc discharge is applied for melting and joining metals. An electric arc is established between a base metal cathode and a consumable wire anode. By the high heat flux from the arc plasma, a droplet forms at the tip of wire and a weld pool forms at the base metal. Arc plasma is composed of large amounts of metal vapor from the droplet and the weld pool. From past studies, it is known that a mixture of metal vapor affects the properties of the arc plasma, such as electrical conductivity and radiative emission coefficient. Numerical models need many assumptions and time for complicated calculations. Therefore, to reduce assumptions and calculation time, a simplified model of the GMA welding arcs ignoring metal transfer is built. In the present model, special account is taken of the amounts of metal vapor, enthalpy of droplet and wire melting rate. These are calculated simultaneously. And then, the present model assumes a steady state, and that arc length is constant. Therefore, the wire feed rate is equal to the calculated wire melting rate. And then, the wire feed rate and the wire melting rate are balanced to keep arc length constant. We study the effects of metal vapor on the heat source properties of GMA welding arcs by using this model. The calculated mole fraction distribution is in agreement with the observed optical image separating bright regions at the arc center, dominated by the metal vapor, and dark regions at the outer arc. The highest temperatures occur at the edge of the arc core. Higher welding currents lead to faster melting and feed rates of consumable wire because of larger heat inputs, such as thermal conduction from the arc plasma and ohmic heating at the wire. For balance of larger heat inputs and faster feed rates of the wire, temperatures of the tip of wire, namely droplet, are kept constant though higher welding currents. This result is experimentally known, however this model enable it to be understood as a physical phenomenon.

10.18910/6896

6896

Numerical Model of Gas Metal Arc with Metal Vapor for Heat Source in Welding

大阪大学接合科学研究所

English

2011-06

Transactions of JWRI

40

1

25

29

https://hdl.handle.net/11094/6896

10.18910/6896

https://doi.org/10.18910/6896