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 penetrati...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.展开更多
Over the past decade, researchers demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance. In this paper, in-situ NbCp reinforced Fe-based wear-resistance coatings with...Over the past decade, researchers demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance. In this paper, in-situ NbCp reinforced Fe-based wear-resistance coatings with different designed NbC contents were produced by laser cladding. The formation mech- anism of NbC particle was analyzed. The effects of NbC content on the microstructure and mechanical properties of coatings were investigated. It was revealed that α-（Fe, Cr）, （Fe, Cr）7C3, NbC existed in all coatings. NbC particles formed by the chemical reaction of Nb and C dissolved in the molten pool. The increase of designed NbC content led to the growth of the porosity amount, and the increase of the size and the area ratio of the particle, as well as the transformation of the NbCp morphology from quadrangle to petaloid shape. Moreover, the micro-hardness and the wear resistance of the coating were improved with the increase of NbC. When NbCp content was 30 wt%, the mechanical properties decreased slightly. Copyright @ 2015, The editorial office of Journal of Materials Science ＆ Technology. Published by Elsevier展开更多
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...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.展开更多
基金The authors would like to acknowledge the financial sup-port from the 973 State Key Fundamental Research Project:Fundamental Research of New Generation Iron and Steel Ma-terials(No.G1998061500).
文摘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.
基金the National Natural Science Foundation of China under grant(10009012201203)
文摘Over the past decade, researchers demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance. In this paper, in-situ NbCp reinforced Fe-based wear-resistance coatings with different designed NbC contents were produced by laser cladding. The formation mech- anism of NbC particle was analyzed. The effects of NbC content on the microstructure and mechanical properties of coatings were investigated. It was revealed that α-（Fe, Cr）, （Fe, Cr）7C3, NbC existed in all coatings. NbC particles formed by the chemical reaction of Nb and C dissolved in the molten pool. The increase of designed NbC content led to the growth of the porosity amount, and the increase of the size and the area ratio of the particle, as well as the transformation of the NbCp morphology from quadrangle to petaloid shape. Moreover, the micro-hardness and the wear resistance of the coating were improved with the increase of NbC. When NbCp content was 30 wt%, the mechanical properties decreased slightly. Copyright @ 2015, The editorial office of Journal of Materials Science ＆ Technology. Published by Elsevier
基金supported by the foundation of Xi'an Jiaotong UniversityNational'973'Project Foundation of China under grant No.G1998061500
文摘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.
