Study On Signal Acquisition System Of Electron Beam Welding And Its Characteristics

High vacuum electron beam has been widely used in many fields,such as electronic devices,aerospace and pressure vessels,because of its advantages of large unit energy,precise control of heating position and radius.As a method of welding Hard-to-weld materials,EBW can obtain stable weld quality and weld strength under the condition of good process monitoring.If the control is not good,the weld quality and weld strength can not be guaranteed.Therefore,real-time collection and monitoring of the process and weld quality of EBW is particularly important.First of all,this paper designed and developed a set of electronic beam dynamic welding acquisition system,including 2 parts of hardware and software,in which the hardware part included 2 modules of sensor detection module and signal processing module.The sensor acquisition module was responsible for collecting space charges at 8 positions at the top of the weld and forming a micro current signal.The signal conditioning module was a signal control cabinet equipped with 8 sets of non sense resistance and micro signal amplification circuit,which was responsible for converting the current signal into a voltage signal and amplification.The software part was the display and analysis module software,including the landing interface,acquisition interface and query interface 3 interfaces,responsible for the real-time display and storage of the voltage signal,for calling and processing analysis conveniently.In order to 'verify the feasibility of the system,from 0 to 4mA,the electron beam with an interval of 0.2mA was added to the aluminum alloy plate.The space charge acquisition system of electron beam was used to collect the current data of the 8 space,which was the sum of the space charge collected.According to the conservation law of the total electron number,the current generated by the space electron and the current on the plate are approximately equal to the original beam,which verified the feasibility of the whole system.Then,the whole electron beam dynamic welding acquisition system was used in the monitoring test of 6061-T6 aluminum alloy welding process.The butt welding plate was welded with different welding parameters and divided into 3 groups:1)weld plate defect test experiment;2)focus position experiment;3)welding speed experiment.Observed the change of voltage waveform in dynamic welding process,and connected and compared the obtained voltage waveform with the whole welding process and weld quality,finally get the weld criterion rule table,including the following 4 criteria:1)the smooth degree of ladder waveform shape overall reflect the stability of weld;2)under the premise of no penetration,high reaction heat input weld waveform of the weld;3)under the direction of 2,6 and 4,8 position weld waveform comparison reaction of homogeneity and symmetry;4)welding joint direction before and after 1,5 and 3,7 position change reaction raised waveform welding direction on the weld penetration depth change.Finally,aiming at 4mm thick 6061-T6 aluminum alloy plate,the weld quality criterion table and the weldability of aluminum alloy were analyzed comprehensively,and the high-quality weld seam and its corresponding voltage waveform were obtained through adjustment and optimization.The feasibility of judging the weld quality by the weld quality criterion table was verified.In addition,the weld quality obtained by optimizing the welding parameters was confirmed by studying the microstructure and mechanical properties.The hardness of the weld was lower than the hardness of the base material by the tensile and the hardness test,and the tensile strength is about 68%of the base material.It was observed that the weld center is the ISO-axis crystal through the microscopic metallographic diagram,and the dendritic columnar structure appears in the area near the center of the weld.Near the weld line,there was a cellular crystal growing along the heat dissipation direction near the weld area.It had successfully verified the previous weld judgement and the feasibility of the whole acquisition system and weld criterion table.