Wyniki wyszukiwania - BazTech

1

Prediction of thermal loads and structure composition in elements welded by laser-ARC hybrid welding technique

Piekarska W., Kubiak M., Saternus Z.

Archiwum Technologii Maszyn i Automatyzacji

|

2011

|

vol. 31, nr 3

29-38

EN

The paper concerns numerical modelling of the temperature field with motion of liquid metal in the melted zone and estimation of the structure composition in the laser-arc hybrid welded joint. Coupled transport phenomena of heat transfer in butt welded plate and fluid flow in the melted zone were described respectively by the transient heat transfer equation with convective term and Navier-Stokes equation. Mathematical models describing electric arc and laser beam heat sources are presented in this study. The latent heat associated with of the material's state changes and latent heat of phase transformations in solid state were taken into consideration in a solution algorithms. On the basis of determined temperature field, structure composition in welded plate made of S355 steel was numerically estimated. Presented results of numerical calculations include temperature field, velocity field in the melted zone and structure composition of welded flat. The influence of chosen process parameters and liquid metal motion in the welding pool on the weld shape and size is analyzed.

PL

Artykuł jest poświęcony modelowaniu numerycznemu pola temperatury z uwzględnieniem ruchu ciekłego metalu w strefie przetopienia oraz prognozowaniu numerycznego składu strukturalnego złącza spawanego metodą hybrydową laser-łuk elektryczny. Sprzężone zjawiska transportu ciepła w spawanym doczołowo płaskowniku i ruchu cieczy w strefie przetopienia opisano odpowiednio równaniem nieustalonego przewodzenia ciepła z członem konwekcyjnym oraz równaniem Naviera-Stokesa. W artykule przedstawiono modele rozkładu mocy źródła ciepła: łuku elektrycz-

2

Numerical simulation of thermal phenomena and phase transformations in laser-arc hybrid welded joints

Piekarska W., Kubiak M., Bokota A.

Archives of Metallurgy and Materials

|

2011

|

Vol. 56, iss. 2

409-421

EN

The paper concerns mathematical and numerical modelling of temperature field with convective motion of liquid metal in the melted zone taken into account and numerical estimation of structure composition of a plate made of S355 steel, butt-welded by laser-arc hybrid welding technique. Coupled transport phenomena, including heat transfer and fluid flow in the melted zone, were described respectively by transient heat transfer equation with convective term and Navier-Stokes equation. Latent heat associated with the material's state changes and latent heat of phase transformations in solid state were taken into consideration in the solution algorithm. The kinetics of phase transformations and volumetric fractions of arising phases were calculated on the basis of the Johnson-Mehl-Avrami (JMA) and Koistinen-Marburger (KM) classic mathematical models. In modelling of phase transformations during heating continuous heating transformation (CHT) diagram was used, whereas continuous cooling transformation (CCT) diagram was used in modelling of phase transformations during cooling of welded steel. Transient heat transfer equation was solved using finite element method in Petrov-Galerkin formulation and Navier-Stokes equation was solved in Chorin's projection method. The solution algorithms were implemented in ObjectPascal programming language.

PL

Praca zawiera numeryczne modelowanie pola temperatury oraz prognozowanie numeryczne składu strukturalnego płaskownika wykonanego ze stali S355, spawanego doczołowo techniką hybrydową laser-łuk elektryczny. Model pola temperatury uwzględnia ruch ciekłego metalu w jeziorku spawalniczym. Sprzężone zjawiska transportu ciepła i cieczy w strefie przetopienia opisywane są rónaniem nieustalonego przewodzenia ciepła z członem konwekcyjnym i równaniem Naviera-Stokesa. W algorytmie numerycznym uwzględniono ciepła związane ze zmianą stanu skupienia materiału i ciepła przemian fazowych w stanie stałym. Kinetykę przemian fazowych w stanie stałym oraz algorytmy numeryczne wyznaczania ułamków objętościowych powstających faz oparto na równaniach Johnsona-Mehla-Avramiego (JMA) i Koistinena-Marburgera (KM). W modelowaniu przemian nagrzewania wykorzystano wykres ciągłego nagrzewania (CTPcA), natomiast w modelowaniu przemian chłodzenia wykorzystano spawalniczy wykres przemian austenitu (CTPc-S) spawanej stali. Do rozwiązania równania nieustalonego przewodzenia ciepła zastosowano metodę elementów skończonych w sformułowaniu Petrov-Galerkina, a równanie Naviera-Stokesa rozwiązano metodą projekcji Chorina. Algorytmy analizy rozważanych zagadnień zaimplementowano w języku programowania ObjectPascal.

3

Position welding using disk laser-GMA hybrid welding

Kim C.-H., Lim H.-S., Kim J.-K.

Journal of Achievements in Materials and Manufacturing Engineering

|

2008

|

Vol. 28, nr 1

83-86

EN

Purpose: Position welding technology was developed by using disk laser-GMA hybrid welding in this research. Design/methodology/approach: The effect of hybrid welding parameters such as the shielding gas composition and laser-arc interspacing distance were investigated for the bead-on-plate welding. The pipe girth welding was implemented and the adequate arc welding parameters were selected according to the welding position from a flat position to an overhead position. Findings: The optimized shielding gas composition and laser-arc interspacing distance for disk laser-GMA hybrid welding were 80% Ar-20% CO2 and 2mm, respectively for the bead-on-plate welding. The sound welds could be achieved even in the pipe girth welding, but the proper joint shape should be prepared. Research limitations/implications: The laser-arc hybrid welding was implemented for pipe girth welding as a kind of 3-dimensional laser welding and the process parameters could be optimized according to the various target materials and sizes. Practical implications: The optimized process parameters for the disk laser-arc hybrid welding can extend the application of the laser hybrid welding technology. Originality/value: This research showed the possibility of the disk laser-GMA hybrid welding as new pipe girth welding technique. The behaviour of molten pool and droplet transfer could enhance understanding of the hybrid welding.