| At present, rail welding includes flash welding, gas pressure welding, thermit welding and arc welding. But, flash welding is still limited to the use of field; rail section processing requirement is strict relatively for gas welding; the weld of thermit welding is a cast structure, the strength and toughness in weld are limited; In recent years, Arc welding of rails has been developed quickly. For example, forced forming arc welding and narrow gap arc welding of full automatic by self shielded flux cored wire.The topic have used the method of the ultra-narrow gap welding for rail joint. Having Designed the torch of ultra-narrow gap welding and flux strip with plug, at the same time, the setting of groove angle before rail welding by a lot of experiments, that is, the setting of reverse deformation angle.it is also the key whether the normal rail welding.and doing some process experiments on the basis of these researches, including effect on cold crack form preheating temperature, hardness test, impact test and An analysis on metallography structure. The specific research contents are as follows:First of all, having a design of novel torch of ultra-narrow gap welding, and studying the stability of welding process. The clamping mechanism of torch can adjust the clamping force for wire by the conductive nozzle,and has a reliable conductivity.In different speed of wire feeding, the torch can meet the requirements of ultra-narrow gap welding.Secondly, having developmented the flux strips with plug, tests found that the flux strips can constraint arc effectively, while can prevent flowing of molten metal in welding end, so that the height of inner bead surface in the groove is matched with the bead surface in end.Once again, the setting of reverse deformation angle. Testing out the match with welding parameters,testing a predetermined reverse deformation angle by reasonable parameters. Getting the relationship of welding defor-mation and welding heat input, the plate thickness.Finally, Having used groove gap of4mm,groove angle of2degrees, plate thickness of3mm,implementing the ultra-narrow gap welding for rail butt. Experiments show that the preheating temperature of400degrees, interlayer temperature not lower than400degrees, can realize the ultra- narrow ga p weldi ng.The wi dt h of HAZ is ver y na rrow a nd hardnes s highly,is about390HV; I n the ca s e of usi n g c onvent ional H08Mn2Si wi re, wit h-out the a dditi on of all oy c o mponents, the har d ness of welds is the levelmat chi ng with base metal, is about300HV, the i mpact energy of i ntegr alweld of welded joint in ul tra-narrow ga p weldi ng is27J, fa r higher t han t hatof6J. |
