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Modelling of transport phenomena in gas tungsten arc welding

100%

Farzadi A. , Serajzadeh S. , Kokabi A. H.

2007

tom Vol. 28, nr 7

417-420

Purpose: Since numerical heat transfer and fluid flow models have provided significant insight into welding process and welded materials that could not been achieved otherwise, there has been an important interest in the quantitative representation of transport phenomena in the weld pool. On the other hand, the temperature and velocity distributions of the molten metal as well as the cooling rate after welding operation affect the weld geometry, the microstructure, and the mechanical properties of weld zone. This work demonstrates that the application of numerical transport phenomena can significantly add to the quantitative knowledge in welding and help the welding community in solving practical problems. Design/methodology/approach: The temperature and velocity fields are simulated using the solution of the equations of conversation of mass, energy and momentum in three-dimension and under steady-state heat transfer and fluid flow conditions. Findings: The weld pool geometry and various solidification parameters were calculated. The calculated weld pool geometries were in good agreement with the ones obtained using the experiments. The solidification parameters of G and G/R are determined. It is found that as the welding speed increases, the value of G/R at the weld pool centerline decreases. Research limitations/implications: Welding process used is this study is gas tungsten arc (GTA) welding and base metal is commercial pure aluminum. This model can be investigated to simulate other materials and welding processes. Also the results of this study such as the temperature field can be used in the simulation of microstructure, mechanical properties, etc of welding zone. Originality/value: In this research the solidification parameters of G, R and G/R can be used for prediction of the solidification morphology and the scale of the solidification structure.

GTA remelting of surface spot defects

100%

Klimpel A. , Luksa K. , Kik T.

2007

tom Vol. 25, nr 2

73-76

Purpose: A statistical model that explains the interaction between cross-section dimensions of a GTA remelted spot area and remelting parameters is presented. It will be utilized in the repair of an investment casting made of nickel-based superalloys. Design/methodology/approach: An experimental design of response surface was used to elaborate the model of GTA remelting. Results of experiments were verified experimentally. Findings: The dimensions and volume of a remelted area are a linear function of the GTA welding process parameters. It is possible to remelt small surface defects and keep a smooth surface. Research limitations/implications: Research results are limited to the tested range of parameters and base material properties. Changes in thermal conductivity can strongly influence the presented results. Crack sensitivity of material can restrict the range of parameters. Practical implications: Results of the research will help in the repair of surface spot defects of nickel-based superalloys. The proposed method of repair can help to minimize the number of rejected parts. Originality/value: A new approach to welding technology is presented. A statistical model of GTA remelting process could be a useful tool for the precise selection of process parameters.

Zrobotyzowane spawanie GTA złączy zakładkowych i spoin grzbietowych blach ze stali S235JRG2 i X5CrNi18-10

80%

Luksa K.

2008

tom R. 80, nr 12

13-16

Przedstawiono wyniki badań technologii spawania zrobotyzowanego GTA (TIG) złączy blach o grubości 1 mm bez dodatku spoiwa. Celem badań było uzyskanie możliwie dużej prędkości spawania złączy zakładkowych i spoin grzbietowych. Uzyskane prędkości spawania wynoszące 7-12 mm/s dla złączy stali S235JRG2 i 10-16 mm/s dla złączy stali X5CrNi18-8 są zbliżone do prędkości uzyskiwanych przy spawaniu plazmowym.

The article offers a presentation of robotised GTA welding (TIG) of metal sheets 1 mm thick without filler metals. The research works focussed on achieving the maximum possible travel speed of overlapping and edge joint welding. The results demonstrated that welding speeds ranging from 7 to 12 mm/s for S235JRG2 steel welds and from 10 to 16 mm/s for X5CrNi18-8 steel welds were similar to those obtained by means of plasma-arc welding.