TECHNIQUE OF SELECTING THE OPTIMUM MODES OF ELECTROCONTACT WELDING

The authors developed a technique of selecting rational parameters of electrical contact welding (ECW) to ensure the quality of coatings produced on the parts of agricultural machines during their restoration and/or hardening. They determined factors that have the greatest infl uence on the quality and properties of coatings – the ECW mode parameters: compression force of welding electrodes, welding current, welding pulse and pause duration, welding speed, material feed, or feed rate, and coolant fl ow rate. By means of the proposed method, the ploughshare from 65Г steel of GOST 1133-71 was strengthened with coating from У12A steel of GOST 2283-79. The following parameters of the EPW mode were obtained: a welding current value of 6.9 kA, a pulse time of 0.06 s, a pause duration of 0.08 s, and a coolant fl ow rate of 1.8 l /min, the overlap coeffi cient of weld spots in a row of 0.635, the overlap coeffi cient of weld spots between rows of 0.76, the coating area welded per pulse of 6.49 mm2, a welding speed of 0.986 m/min and the maximum performance of the ECW process of 22.48 cm2/min. The hardness of the obtained coatings was 60…62 HRCэ, and the relative wear resistance was more than 4 times higher than that of steel 45 (180 HB). The study has experimentally confi rmed the feasibility of using the developed technique for selecting rational EPW parameters to ensure
the quality of coatings produced on the parts of agricultural machines during their restoration and/or hardening.