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Weld transference modes identification through sound pressure level in GMAW process

100%

Cayo E. H. , Absi Alfaro S. C.

tom Vol. 29, nr 1

57-62

Purpose: One of the most used processes in the industry is GMAW, in this welding process there is physical phenomena such as the temperature, electromagnetic field, luminosity and sound pressure. It is known that GMAW weld specialized techinicisian combine visual and sound at the work to garantee the process stability. It is important to improve the final weld quality; therefore, the quantification of electrical and acoustical behaviour-within the audible bands, offer an information that is important to comprehend his impirical rules. Design/methodology/approach: With these he can identify the transfer mode, instabilities in the process, determine defects and evaluate the weld quality along the weld bead. The sound signal is captured simultaneously with the arc voltage and current signals. Was proved that first derived from the instantaneous power of the electrical arc presents a behaviour similar to the acoustical with a delay, because the measured sound is airborne. Findings: This relation was corroborated by the comparison between the sound pressure level calculated by electrical signals and by acoustical signals. This relation presented a similarity between the calculated signals greater than that between the sound and the power first derived. Practical implications: Besides that, with the sound pressure level it is possible to identify process instabilities that is not so trivial to realize with the sound pressure signal. In spite of it, the identification of instabilities for the globular and spray tranfer modes displays greater difficulty than that for the short circuit transfer mode. It was shown that the acoustical weld sensing offers information about the behaviour of the tranfer mode and the process stability. Originality/value: The sound quantification would be applied as a control variable for the weld process. Thus, it would be possible to develop similar control strategies as those applied by specialized workers.

Susceptibility for extrusion welding of AlMg alloys

84%

Leśniak D. , Wassermann A. , Dziki M. , Zaborowski K. , Jurczak H.

2019

tom Vol. 19, no. 1

20--31

The extrusion of hollow profiles from high strength aluminium alloys through porthole dies causes serious problem in practice. Mainly, this is due to low weldability of these alloys and high extrusion force. The present paper discusses the investigations undertaken to determine the weldability of hard AlMg alloys using the original method and device. Main advantage of the proposed method is that it allows for the reflection of real welding conditions occurring in a welding chamber of the porthole die. Weldability tests were performed for alloys: 5754 (3.5% Mg), 5083 (4.5% Mg), 5019 (5.6% Mg) and 5xxx (7.1% Mg) in a wide range of temperature, unit pressure (normal compressive stress) and duration of welding. Microstructure and strength properties of the welds were examined. Most favourable welding conditions for the tested alloys, allowing for obtaining high strength welds were defined. To validate the laboratory experiments the extrusion trials were performed in the industrial conditions, in which the round tubes from 5754 alloy were produced using the porthole dies. The tensile strength of the welds in the extruded tubes is comparable to that for the solid material. Strength of the welds as well as of the solid material strongly increases with magnesium content in the alloy.