Analysis On X65 Pipeline Steel Flash Welding Temperature Field And Research On The Performance Of Welded Joint

X65 pipeline steel with high strength and resistance to ductile fracture is good, high grade pipeline in gas transmission pipeline, pipeline transport as the main body, the welding quality of pipeline transportation plays an important influence. A significant advantage in the pipeline welding flash butt welding technology, but with the strength of high strength pipeline steel increases, the high strength steel flash on quality and safety issues have become increasingly prominent the welding head, become the bottleneck of flash butt welding technology in high grade pipeline application development. The pipeline of flash butt welding parameters have certain influence on the mechanical properties, and the quality of the welding joint therefore, correct choice of technical parameters is the key to ensure the welding quality, this paper will start the process in different speed flash on the distribution of temperature field and properties of the joint were performed to study the effect of flash welding of pipeline.Firstly, using the image processing technology of X65 pipeline steel in the process of flash butt welding pipe mouth gathered in the formation process of molten metal residue monitoring; analysis of its forming process, molten metal residue obtained in the welding process, the area time curve, provide accurate boundary conditions for the simulation of the temperature field of the next step.The coupling model of flash butt welding pipe electro thermal finite element of X65 pipeline steel, flash butt welding, flash flash:excitation stage, stable stage of accelerated stage in different phases of flash welding end temperature field numerical simulation. The model considered the effects of phase change material and temperature on the thermal physical properties of material coefficient, to solve the problem by using flash burn unit "and" technology, through the element entity layered loading to solve the contact resistance problem, summarize the flash butt welding of X65 pipeline steel in different stages of the temperature field distribution. In the process of welding in the welding process and welding temperature with infrared thermal imager and real-time measurement, test results show that:temperature measurement and calculation results, the numerical model can accurately reflect the actual welding process.Finally, the different speed flash welding joint are obtained under the test of mechanical properties, including tensile, bending, Nick break test, analyze the performance of the joint is better than that of second groups of flash rate under the other two contrast, that flash rate has an important influence on the formation of flash butt welding process welding temperature field; flash rate is too slow or too fast are difficult to weld end forming a layer of molten metal, the heat source in time is reduced, so that the welding port temperature is relatively low, the welding deformation of hot regional narrow port, the tensile strength of welded joints can bend, poor performance, and will form a large number of gray leaf spot defects in welding seam. Selection of mechanical properties of second groups of joints better metallographic microstructure analysis by using metallographic observation, microstructure of joints of X65 pipeline steel was the discovery of flash butt welding joint microstructure of weld zone is close to the larger the grain size, the weld zone grain size reaches the maximum, the joint microstructure along the axial line is gradually increasing. Distance from the fusion line, more far, welding heat input is relatively reduced, the welding heat cycle curve of each point in the region difference of grain. This is the base metal heat affected zone and weld zone grain is coarsening reason.