               Ioan Sorin Leoveanu 1,a , Gheorghe Zgura 2,b 1 Transilvania University Brasov, Romania. 2 Polytechnic University Bucharest,Romania a leoveanui@yahoo.co.uk b ghzgura@yahoo.com  keyhole weld shape, phase’s interaction, welding sources, MHD  The paper proposes a numerical method for analyzing the complex phenomena’s that appear in the case of keyholes welded pool geometry. Present model consist in a succession of analyses steps, needed to solve the interaction between the liquid/solid, liquid/protection gaze and liquid/MHD welded arc for arc welding, or electrons, or electromagnetic waves. The liquid/solid geometry result by dissipation of the welding power source in a matrix of many point sources. This process gives a first approximation of temperature fields and a good approximation of the digit 3D position, and information about the vaporization area.   The welding by fusion is an important manufacturing technique that is being used more frequently in the modern manufacturing of various areas. In the last decade, the knowledge about fusion welding processes has attained the level of maturity that imposes a special attention. The physical processes that take place during fusion welding, are in the field of Magneto Hydro Dynamics for the Shield Arc Modeling and in the area of heat transfer, melting, Marangoni convection, electromagnetic and buoyancy forces for the welded pool in the fluid state. In the actual approach, the models for establishing the weldment characteristics are appearing well documented in papers [1, 6]. Convection in the weld pool is recognized as one of the important processes that determine weld pool characteristics such as size and shape [1,2,5]. The studies in the area of that type of sources are limited. That new shape is known in literature as keyholes and this mathematical estimation with classical methods give unacceptable errors. Studies of those types of sources have been made previously using numerical methods. The Marangoni condition takes a great complexity, given by gradients of temperature and concentration. In the current paper, we use matrix/distributed point sources to establish the heat flow and give the key/hole formation. The heat flow is given in a three/dimensional approach and the temperature field obtained in the melt is used to establish the heat and fluid advection. The pressures of arc and gazes are considerably stationary and have no variations in the process analysis. Based on MAC techniques, the shape of free surface is obtain from longitudinal section of weld and from the transverse section positioned in the arc/welded source. From the experimental verification, based on various welded joints, this approach of the complex process is in agreement with the proposed model.    Figure 1 shows the model for the present study. The inlet position is located at welding arc point in the section where the droplets arrive in the welded melt pool. The staggered grid is adopted in the finite volume approach, which forms the basis of the MAC method. Materials Science Forum Vols. 580-582 (2008) pp 443-446 online at http://www.scientific.net © (2008) Trans Tech Publications, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 92.81.138.54-28/04/08,17:05:12)