Fundamental Research on the Mechanism of High-Speed Welding Undercut

2011 ◽  
Vol 287-290 ◽  
pp. 2152-2155 ◽  
Author(s):  
Peng Fei Huang ◽  
Chao Tang ◽  
Zhen Yang Lu
Keyword(s):  
Temperature Gradient ◽  
High Speed ◽  
Active Element ◽  
Flow Direction ◽  
Surface Flow ◽  
The Other ◽  
Welding Pool ◽  
Surface Active Element ◽  
Fundamental Research ◽  
Surface Active

Undercut is one of the most important problems which restrict welding speed. The research indicated that surface flow direction of welding pool near the periphery is the most important reason of undercut occurred. When the existence of surface active element (e.g. the content of S is about 0.02-0.04% in steel) change the sign of surface tension temperature coefficient to positive, undercut always occurs in TIG moveless welding, and not occurs when the content of S in iron is very low( e.g. S% is less 0.01%). Temperature gradient is the most important factor which influences the depth of undercut. The depth of undercut is bigger with the increase of temperature gradient when the other parameters are the same. When filling metal into welding pool, it restrained the molten metal movement from periphery to the pool center. So it can reduce the tendency of undercut, and eliminate undercut as increasing of filling metal ultimately.

Study on Interfacial Tension and Flammability of Mg-Ca-Ce Alloy Melt

2011 ◽  
Vol 418-420 ◽  
pp. 383-386 ◽  
Author(s):  
Xian Kuo Meng ◽  
Wei Min Zhao ◽  
Jian Ding
Keyword(s):  
Interfacial Tension ◽  
Composite Film ◽  
Flame Retardant ◽  
Ignition Temperature ◽  
Active Element ◽  
Mg Alloy ◽  
Ignition Point ◽  
Surface Active Element ◽  
Surface Active

The Mg-Ca-Ce ignition-proof Mg-alloy with high ignition temperature was developed based on the synergy of flame retardant role of Ca element and Re element ,and the flame retardant mechanism were investigated. The interfacial tension of Mg-Ca-Ce alloy melt was measured with the maximum bubble method. The interfacial tension is found to be remarkably lowered with the increase of Ce element that is a kind of surface active element to Mg-Ca alloy. The results also showed that the compact composite film composed of Ce2O3,CaO and MgO could be formed and reduce the flammability significantly when the Ca content and Re content were 1.2wt.% and 1.5 wt.% respectively, which prevented alloys from oxidation further and raised the ignition point nearly 150°C.

scholarly journals Interfacial phenomena between molten iron and molten slag–Effect of nitrogen on the Marangoni convection

2021 ◽  
Vol 56 (13) ◽  
pp. 7811-7822
Author(s):  
Taishi Matsushita ◽  
Ilja Belov ◽  
Dimitrios Siafakas ◽  
Anders E. W. Jarfors ◽  
Masahito Watanabe
Keyword(s):  
Marangoni Convection ◽  
Sessile Drop ◽  
Active Element ◽  
Slag System ◽  
Molten Iron ◽  
Interfacial Phenomena ◽  
Surface Active Element ◽  
Gas System ◽  
Surface Active ◽  
Calculated Velocity

Abstract In order to investigate the influence of the surface-active element on the interfacial phenomena between molten iron and molten Al2O3-CaO-SiO2 slag, a mildly surface-active element, nitrogen, was introduced, and the interfacial phenomena were directly observed using an X-ray sessile drop method. The multiphysics model was employed to calculate the velocity of the Marangoni convection caused by the surface/interfacial tension gradient along with the contour of the sessile drop. Movement of the sessile drop was observed in the experiment, and the driving force of the movement was discussed from the distribution of surface tension active element viewpoint. The calculated velocity of the Marangoni convection in the droplet was reasonably agreed with the literature data for the metal-gas system, and thus, the same model was applied for the metal-slag system. The velocity of the Marangoni convection for the metal-slag system becomes ten times lower compared to that of metal-gas system. Graphical abstract

Effective Permeability of a Layered Porous Cavity

2000 ◽  
Vol 123 (3) ◽  
pp. 512-519 ◽  
Author(s):  
J. C. Leong ◽  
F. C. Lai
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
System Approach ◽  
Effective Permeability ◽  
Flow Direction ◽  
The Other ◽  
Heat Transfer Analysis ◽  
Arithmetic Average ◽  
Porous Cavity ◽  
Wide Range

The feasibility of using a lumped system approach in the heat transfer analysis of a layered porous cavity is numerically investigated in this paper. Two layered cavities are considered; in one case the sublayers are perpendicular to the imposed temperature gradient while in the other case they are parallel to the imposed temperature gradient. Numerical calculations have covered a wide range of parameters (i.e., 10⩽Ra1⩽1000,0.01⩽K1/K2⩽100, and L1/LH1/H=0.25, 0.5 and 0.75). The results are presented in term of the effective Rayleigh number which is defined based on the effective permeability. Two averaging techniques are used for the evaluation of the effective permeability; one is arithmetic average and the other is harmonic average. The results show that the lumped system approach can provide a fairly accurate prediction in heat transfer if the permeability is correctly characterized. Also found is that the effective permeability of a layered porous cavity is strongly dependent on the orientation of sublayers and the primary heat flow direction.

scholarly journals An experimental study of the inclusion behavior during maraging steel processing

2019 ◽  
Vol 116 (5) ◽  
pp. 517
Author(s):  
Rayan Bhar ◽  
Julien Jourdan ◽  
Vincent Descotes ◽  
Alain Jardy
Keyword(s):  
Electron Beam ◽  
Maraging Steel ◽  
Sulfur Content ◽  
High Speed ◽  
Flow Direction ◽  
Marangoni Effect ◽  
Surface Active Element ◽  
Liquid Metal Surface ◽  
Steel Processing ◽  
Time Observation

Two maraging steel rods with different sulfur content, deliberately seeded with alumina (Al2O3) inclusions, were remelted in an electron beam furnace. The aim was on one hand to highlight the emergence of non-metallic inclusions at the liquid metal surface and on the other hand to study the effect of the presence of a surface active element (sulfur) on their behavior. The in situ real time observation of Al2O3 clusters was possible using both high-speed video and infrared thermography. The inclusions emerge and tend to collide and quickly agglomerate into rafts. A semi-quantitative analysis confirmed that almost 100% of inclusions are captured at the free surface. The electron beam creates large thermal gradients in the impingement zones; this induces thermocapillary convection (Marangoni effect). The flow direction depends on the sulfur content. This tendency was well-observed by following the trajectories of inclusion rafts.

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