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Effects of Surface-Active Elements Sulfur on Flow Patterns of Welding Pool

Journal of materials science & technology 2005年第3期21卷 408-414页

作者： yuzhen zhao, yongping lei and yaowu shi school of materials science and engineering, beijing university of technology, beijing 100022, china school of materials science and engineering Beijing University of Technology Beijing 100022 China

A 3D mathematical model is developed to calculate the temperature and velocity distributions in a moving gas tungsten arc (GTA) welding pool with different sulfur concentrations. It has been shown that, the weld penetration increases sharply with increasing sulfur content. When sulfur content increases beyond 80 × 10-6, the increase in sulfur content does not have an appreciable difference on the welding pool size and shape, and the depth/width remains constant. Sulfur changes the temperature dependence of surface tension coefficient from a negative value to a positive value and causes significant changes on flow patterns. The increase in soluble sulfur content and the decrease at free surface temperature can extend the region of positive surface tension coefficient. As sulfur content exceeds 125×10-6, the sign of surface tension coefficient is positive. Depending upon the sulfur concentrations, three, one or two vortexes that have different positions, strength and directions may be found in the welding pool. The contrary vortexes can efficiently transfer the thermal energy from the arc, creating a deep welding pool. An optimum range of sulfur content is 20-150×10-6.

关键词： Surface-active elements Sulfur Plow patterns Depth/width

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Numerical Analysis of Two-Way Interaction between Weld-Pool and Arc for GTA Welding Process

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Journal of materials science & technology 2001年第1期17卷 171-172页

作者： yongping lei Xianghua GU yaowu shi Welding Research Insttute School of Mechanical EngineeringXi’an Jiaotong UniversityXi’an 710049China beijing Polytechnic university

A mathematical model to describe the heat transfer and fluid flow in the mutually coupled weld pool and arc by an interactive free surface of the pool for a stationary gas tungsten arc welding (GTAW) is developed. The two sets of governing equations and auxiliary formulas, controlling the weld pool and plasma arc systems respectively, were solved by a finite difFerence method. A boundary-fitted coordinate system was adopted because the free surface has a curved and unknown shape during welding. The results of this work provide a fundamental basis for predicting the behavior of an integrated' weld pool and arc system from first principles.

关键词： TUNGSTEN

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Numerical Simulation of Direct Current Flash Butt Welding Process and HAZ Structures for A 400MPa Ultra Fine Grain Reinforcing Steel Bar

Numerical Simulation of Direct Current Flash Butt Welding Pr...

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第二届先进钢铁结构材料国际会议

作者： WANG Weibin shi yaowu lei yongping LI Xiaoyan(school of materials science & engineering beijing university of technology 100 Ping Le Yuan Chaoyang District beijing 100022 PR china)

＜正＞FEM of axial symmetry was used to simulate the process of DC Flash butt welding. Element live-death method was adopted to simulate metal melt. The temperature field of the weld joint via this method was computed. Thermal rigid-viscoplastic finite element method and Monte Carlo simulation technology were adopted in this work. After considering the coupling effect of electricity, heat and forging and the loss of mass in the flashing process, welding deformation, weld formation and austenite grain growth in the HAZ were simulated. The simulations give out the evolution of grain structure, grain size distribution in HAZ of the ultra-fine grain steel bar and block effect of grain growth by temperature gradient. The research provides the effective analyzing way of establishing welding parameters and improving the welding properties of ultra fine grain steel and the quality in the welded joints.

关键词： Ultra-fine Grain Steel Bar DC Flash Butt Welding Monte Carlo Method Micro-structure Simulation FEM

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