Thermal efficiency in electron beam processing of structural materials

The results of studying the interrelation that links the electron beam welding (EBW) thermal efficiency, thermophysical properties of the material, and welding speed are presented. Thermal efficiency was determined by a combined experimental and computational method based on measuring the penetration areas and evaluating the energy expenditure for melting with the known welding mode parameters. The study was carried out on a series of microsections prepared from welded joints of 5V titanium alloy, grade 40Kh13 steel, D16 duralumin, BrKh1Tsr bronze, and TsM2A molybdenum. It is shown that in EBW with deep penetration, its thermal efficiency increases with increasing the welding speed and decreasing the welded material thermal diffusivity. The experimental dependence of the thermal efficiency on the welding speed is approximated with sufficient accuracy by a logarithmic curve. Thus, in increasing the EBW speed from 20 to 120 m/h, the thermal efficiency increases from 54% to 67% for 5V titanium alloy, from 46% to 63% for 40Kh13 steel, and from 18% to 40% for D16 duralumin. The thermal efficiency in welding bronze (at an EBW speed of 30 m/h) and in welding TsMA molybdenum (at a speed of 20 m/h) was 15% on the average. An analysis of the thermal efficiency curve versus the dimensionless parameter vd/2a has shown that the thermal efficiency for all materials can be approximated by a single logarithmic dependence. An empirical relationship is proposed, using which the welding thermal efficiency can be determined as a function of welding speed and material thermal diffusivity.