Study On The Joining Technology Of Low Plastic Metal Sheets

Non-ferrous metal materials have drawn wide attention because of their excellent properties. Joining technology is the key technology for the application of metal materials. Traditional welding technologies are not very suitable for joining non-ferrous metal materials due to their active chemical characteristics, easy to oxidation and high thermal and electrical conductivities. Mechanical joining technology can be used to joint non-ferrous metal sheets. However, existing mechanical joining technologies all have some deficiencies. For example, the low-plastic metal sheets must be preheated prior to the self-pierce riveting (SPR) of the sheets. Otherwise, it will cause the sheets to crack. In this paper, a new joining process—drill-pressing riveting (DPR) is proposed for joining low-plastic metal sheets, and the DPR process were systematically studied. The main studies and results are summarized as follows.1. The riveting principle of DPR process were carefully analyzed and studied, and the rivet and die were designed and made for DPR process. Through the joining tests of different metal sheets, DPR process was proved feasible, and could be used to join plastic metal sheets or low-plastic metal sheets at room temperature, and provide the joints with good appearance and superior mechanical performances. Therefore, DPR process is a type of mechanical joining technology that has extensive applicability.2. The effects of the geometrical parameters of rivets, the rivet rotating speed and the punch pressure on the quality and properties of the DPR joints were studied. The results showed that the rivet length had a significant influence on the mechanical properties of DPR joints, and the riveting effectiveness of DPR process was optimal when the rivet length was2to2.5mm longer than the total thickness of the riveted sheets; The punch pressure affected the mechanical properties of DPR joints obviously. The proper increase of the punch pressure could increase the mechanical properties of DPR joints. However, excessive punch pressure was not good for increasing the mechanical properties of DPR joints; The rivet rotating speed hardly affected the mechanical properties of DPR joints, thus DPR operation could be performed in a wide range of the rivet rotating speed. But, the use of a high rivet rotating speed could reduce the feed force and the riveting time.3. The DPR joints of2mm thick AZ31magnesium alloy sheets were produced at room temperature. The shear tensile and the fatigue properties of the DPR joints were studied and compared with those of the SPR joints, which were produced using the same sheet preheated at180℃. The results showed that the DPR operation of the AZ31magnesium alloy sheet at room temperature was feasible, and provided the joints with good and free-crack appearances; The shear tensile and fatigue properties of the DPR joints were all better than those of the SPR joints.4. The DPR joints of3mm thick cast A356aluminum alloy sheets were produced at room temperature. The shear tensile and fatigue properties of the DPR joints, and the effect of hot-humid environment exposure on the DPR joints were studied and compared with the bolt joints, which were produced using the same material sheet. The results showed that DPR operations of the low-plastic cast A356aluminum alloy sheets without preheating could be performed, and provided the joints with good quality; The shear tensile property of the DPR joints obviously better than that of the bolt joints. The fatigue properties of the DPR and bolt joints were comparable, but the stability of the fatigue life of the DPR joints was higher than the bolt joints. The hot-humid environment exposure had no noticeable influence on the shear tensile property of the DPR joints.5. DPR test of3mm thick wrought6063aluminum alloy sheet was carried out, and the mechanical properties of the produced joints were studied and compared with the SPR joints of the same sheets. The results showed DPR process was also suitable for joining the metal sheets with good plasticity and the shear tensile and fatigue properties of the DPR joints were all better than those of the SPR joints.