Journal ArticleDOI
The effect of alloy composition and welding conditions on columnar-equiaxed transitions in ferritic stainless steel gas-tungsten arc welds
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In this article, columnar equiaxed transition was investigated in full penetration gas-tungsten arc (GTA) welds on ferritic stainless steel plates containing different amounts of minor elements, such as titanium and aluminum, for a range of welding conditions.Abstract:
The columnar-equiaxed transition (CET) was investigated in full penetration gas-tungsten arc (GTA) welds on ferritic stainless steel plates containing different amounts of minor elements, such as titanium and aluminum, for a range of welding conditions. In general, the fraction of equiaxed grains increased, and the size of the equiaxed grains decreased with increasing titanium contents above 0.18 wt pct. At a given level of titanium, the equiaxed fraction increased, and the size of the equiaxed grains decreased with increased aluminum content. The CET was ascribed to heterogeneous nucleation of ferrite on Ti-rich cuboidal inclusions, since these inclusions were observed at the origin of equiaxed dendrites in the grain refined welds. Titanium-rich cuboidal inclusions, in turn, were found to contain Al-Ca-Mg-rich inclusions at their centers, consistent with observations by previous investigators for other processes. The welding conditions, in particular, the welding speed, were observed to affect the occurrence of the CET. Increasing the welding speed from 3 to 8 mm/s increased the equiaxed fraction noticeably, but a further increase in speed to 14 mm/s had a smaller additional effect. A finite element model (FEM) of heat transfer was used to examine the role of the welding conditions on the local solidification conditions along the weld pool edge. The results are compared with existing models for the CET.read more
Citations
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Prediction of Grain Structures in Various Solidification Processes
TL;DR: In this article, a physically based cellular automaton (CA) model was coupled with finite element (FE) heat flow computations and implemented into the code3-MOS. This CAFE model, which allows the prediction and visualization of grain structures during and after solidification, is applied to various solidification processes: the investment casting of turbine blades, the continuous casting of rods, and the laser remelting or welding of plates.
Journal ArticleDOI
Effect of inclusions on the solidification structures of ferritic stainless steel: Computational and experimental study of inclusion evolution
TL;DR: In this paper, the effect of oxide and nitride inclusions in a steel melt on the formation of the equiaxed grain structure during solidification of ferritic stainless steel has been investigated.
Journal ArticleDOI
Mechanisms of equiaxed grain formation in ferritic stainless steel gas tungsten arc welds
TL;DR: In this article, the authors examined the properties of providing nuclei for equiaxed grains in gas tungsten arc welds in ferritic stainless steel and found that adding TiN particles in commercial steels could act as heterogeneous nucleation sites.
Journal ArticleDOI
Finite element analysis and simulation of welding: a bibliography (1976 - 1996)
TL;DR: In this paper, a bibliographical review of the finite element methods (FEMs) applied to the analysis and simulation of welding processes is presented. But the authors do not provide a detailed discussion of the application of FEMs to welding processes.
Journal ArticleDOI
A sensitivity analysis of the columnar-to-equiaxed transition for Ni-based superalloys in electron beam additive manufacturing
Michael Haines,Alex Plotkowski,Curtis Lee Frederick,Edwin J. Schwalbach,S. Suresh Babu,S. Suresh Babu +5 more
TL;DR: In this article, the columnar-to-equiaxed transition (CET) model was used to evaluate the influence of alloy composition on columnar to equiaxing transition.
References
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Journal ArticleDOI
Steady state columnar and equiaxed growth of dendrites and eutectic
TL;DR: In this article, an analysis for the growth of equiaxed grains ahead of the columnar front during directional solidification is presented, and the model considers both single-phase and eutectic growth.
Journal ArticleDOI
The effect of carbide and nitride additions on the heterogeneous nucleation behavior of liquid iron
TL;DR: In this paper, a systematic study of carbide and nitride additions on the heterogeneous nucleation behavior of supercooled liquid iron was undertaken, and it was found that titanium nitride and titanium carbide were very effective in promoting heterogenous nucleation.
Journal ArticleDOI
Distribution of the heat and current fluxes in gas tungsten arcs
N. S. Tsai,Thomas W. Eagar +1 more
TL;DR: In this article, the distribution of heat flux on a water-cooled copper anode as a function of welding process parameters has been determined experimentally following an experimental technique developed previously, and the results indicate that arc length is the primary variable governing heat distribution and that the distribution is closely approximated by a gaussian function.
Journal ArticleDOI
Grain refinement in magnetically stirred GTA welds of aluminum alloys
B. P. Pearce,H. W. Kerr +1 more
TL;DR: The mechanisms of grain refinement have been examined for magnetically stirred gas tungsten arc (GTA) welds completely penetrating thin sheets of several aluminum alloys in this article.