The mainly used aluminium alloys in automobile industry are AlMg alloys. Because of the significant difference in the evaporation temperatures of aluminium and magnesium, the process of metal transfer through the welding arc is often very unstable. This has an influence on the droplet behaviour as well as on the physical properties of arc plasma. Understanding the physical phenomena in AlMg droplets in MIG welding helps to have a better control of the welding process. This paper presents the results of study of a task concerning volumetrical evaporation and behaviour of droplets in pulsed MIG welding of AlMg alloys. A simplified 1-D model for studying the phenomena of droplet behaviour in pulsed MIG welding of AlMg alloys is proposed. The used boundary conditions are nonlinear and solved in external modules using mathematical models of binary alloy evaporation. The calculations were made for AlMg3 alloy at a mean welding current I=60 A and j=7,000 A/cm2. During the impulse phase of pulsed MIG welding, the surface of filler metal heats up to the boiling point of the AlMg3 alloy, in approximately 0.3 ms. Due to the de-enrichment of magnesium at the surface of the molten filler metal, the boiling point of the alloy rises up to the boiling point of pure aluminium (about 1 ms), which leads to an increase of the surface temperature of the alloy. The selective evaporation and de-enrichment of magnesium takes place at the surface of the molten filler metal (0. 01 mm deep). Behind the de-enriched area the overheated area is located (0.01-0.25 mm deep, T is overheated to about 400 K above Tb). This leads to volumetrical overheating of the alloy and the free surface becomes very unstable and explodes, which is demonstrated in experiments.


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    Titel :

    Task of volumetrical evaporation and behaviour of droplets in pulsed MIG welding of AlMg alloys


    Beteiligte:
    Reisgen, U. (Autor:in) / Mokrov, O. (Autor:in) / Zabirov, A. (Autor:in) / Krivtsun, I. (Autor:in) / Demchenko, V. (Autor:in) / Kisnyi, O. (Autor:in) / Semenov, I. (Autor:in)

    Erschienen in:

    Welding in the World ; 57 , 4 ; 507-514


    Erscheinungsdatum :

    2013


    Format / Umfang :

    8 Seiten, 11 Bilder, 1 Tabelle, 11 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch




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