The Research On Key Technologies Of Ultra-Narrow Gap Gas Metal Arc Welding

In order to meet the thick plate with high welding quality, low production cost requirements in modern industry. This paper designed, development and manufactured an ultra-narrow gas metal arc welding equipment independent. This paper focused on ultra-narrow gap welding in-depth study, a number of key technologies was solved such as sidewall fusion, height tracking and horizontal tracking, it provided technical guarantee for indusial application.This paper used a new technical program that bending welding wire drive arc lateral swing in order to solve ultra-narrow gap GMAW sidewall fusion problem. Temperature field was calculated under the condition of swinging arc by using finite element analysis software. In three-dimensional temperature field calculation, the welding heat source path will be divided into four paragraph in accordance with the swing movement position in a cycle based on the actual welding carriage movement, the swinging heat source dynamic equation was given by applying rotation transformation of coordinates in a cycle, the thermal cycle curve was shown the five measured points on the base metal, the five points temperature variation curve above were recorded by using K type thermocouple temperature measurement device, which proved the Calculation accuracy. The results showed that the thermal cycle curve of measuring point present double-peak form in the swing arc conditions. The temperature rising speed is much fast compared with usual GMAW welding. Process parameters were given to meet the plate fusion conditions.A set of ultra-narrow gap GMAW bend welding wire mechanism was designed by using the results of finite element analysis, bend wire mechanism consist of machine controller, servo motor,gear, rack and other devices, the welding wire bend amplitude was adjusted by changing motor speed, pause time at limit position and bend stroke. Experimental results on multiple regression analysis found that bending stroke is the biggest factor of bend welding wire amplitude, the single factor regression formula between bending amplitude and bending stroke was given, the typical bending wire amplitude was set to make surfacing test. The results showed that the weld pool width was in to the increasing trend with the increase of bend wire amplitude, the weld surface forming present concave shape trend, the initial weld width is larger than the back width with the same bend welding wire.The paper discussed the relationship between welding torch height and welding current in ultra-narrow GMAW. The results showed that the welding current and torch height is in linear relationship within the scope of certain when the power was fixed, the fitting expression between welding current and welding torch height was given by the Hall sensor installed in power to measure the current and torch height, an adaptive welding torch height control system was designed, one-dimensional laser sensor was to measure the weld height and high degree digital signal filtering algorithm was applied to adjust welding torch for ensuring constant distance to the weld, the algorithm is verified efficient and noise immunity. The torch height control system consists of control cabinets, machine controllers, car motor, elevation motor, ball screw and other components.A floating elastic torch is designed in order to ensure the torch at the center of the weld all the time when the bend wire is used, Before and after the welding torch position in the arrangement of the same spring and roller, the torch maintain the floating in the weld by the elastic between roller and sidewall. The analysis of four typical weld groove proved the feasibility of the design in theory, the experiments have also been proved the program.Three low-alloy high strenth steel have been weldinged by the designed ultra-narrow gap GMAW system the results found this technology have many advantages in access such as productivity, production efficiency and so on. Meanwhile, the welding joints have been tested in strength, ductility, toughness and hardness. The results showed that the parameters of joints have reached theearly expectations.