Mechanical Properties and Microstructure, in welded joints of Low and Medium Carbon Steels, Applying Rotary Friction
International journal of recent technology and engineering
The effect of friction welding (FRW) in joints of medium and low carbon steels on its mechanical properties and microstructure was studied. AISI 1020 and 1045 steel bars of 12 mm diameter were used. Welding was carried out on a lathe with coupling to control the process parameters. For 1045/1045 joint, the following parameters were used: n = 1400 rpm, Friction pressure Pf = (0.8 - 1.0) MPa; Friction time (Tf) = 8 sec; Upsetting pressure (Pr) = 5 MPa; Upsetting time (Tr) = 5 sec, were used. For
... ec, were used. For 1020/1045 joints the parameters that only varied were: n = (1000 - 1400) rpm; Pf = (0.7-0.8-1.0) MPa. Tensile tests were carried out on the IMSTRON UNIVERSAL machine under ASTM E8 standard. Microhardness tests were carried out on (HV) 0.5 scale, making a longitudinal and transverse scanning profile. Microscopy at the optical (OM) and electronic SEM levels, with analysis (EDS) was revealed. It was found for similar joints: a higher value of (Pf) increases the mechanical resistance (σrm), but for dissimilar joints decreases it. Welding efficiency of similar joints was 94% and for dissimilar joints 97.5% with regard to 1020 and 74% with regard to 1045. For dissimilar joints, a higher speed "n" increases σy, and σrm, with little effect on "ɛ". In similar joints the microhardness is maximum in the center, and for the dissimilar ones it is not. Longitudinal and transverse microhardness profiles do not follow a defined pattern with respect to Pf. For both types of joints, the microstructure shows, that FDRZ joint zone, has variable thickness and has a fully recrystallized fine-grain structure. TMAZ deformation zone, a structure of deformed grains and dark grains is observed, the latter, due to the excess carbon produced by diffusion. In both cases, no intermetallic compounds have been produced, and perlite colonies is not observed in these two zones.