Research On The Characteristics Of Laser Spot Weldbonding

Laser spot weldbonding is a new and efficient hybrid joining technology, which uses both laser spot welding and adhesive bonding.The fatigue performance of laser spot welding is poor, the fatigue properties of adhesive bonding is good, but the strength of adhesive bonding is low, so taking the laser spot welding and adhesive bonding combined could integrate the advantages of both, overcome the shortcomings of their own, and get a joint with good comprehensive mechanical properties.In present paper, low carbon steel and three kinds of adhesive, Terokal-5089, AD-1301 and J-11, are used to research the laser spot welding process, the influencing factors, the microstructures and mechanical properties of the joints.Process tests showed that the adhesive layer under the action of the laser decomposes, the out-gas will affect the welded spot forming. The effect of the layer's viscosity, thickness, the laser power and defocusing on the process stability was researched. Using the appropriate precess parameters, laser power and the special waveforms, the spatter problem caused by adhesive decomposition was solved sucessfully.A carbon residue left by the layer decomposition can infiltrate C to the solder joints and heat affected zone. In present paper, the microstructures of laser spot welding and laser spot weldbonding was analysed, the microstructures change of laser weldbonded spot and heat affected zone caused by carburzing was researched. Through the metallographic observation, a interfacial reaction zone in the edge of laser weldbonded spot was found. The composition and microstructure of the region was researched, as well as the reasons for its formation.The shear test, three-point bending test, T-peel test and fatigue test was carried on the adhesive bonded, laser spot welded and laser spot weldbonded joints, respectively.Shear test showed that: in the three kinds of adhesive, Terokal-5089 adhesive bonded joint has optimal performance; the strength of double solder joint is higher than single solder joint; the spot size influence the joint strength; the strength of laser spot weldbonding is a little higher than the adhesive bonded and laser spot welded joints; the fracture way of laser spot weldbonded joint is that layer fractures firstly, then solder joint tears; the joint fracture is a combination of laser spot welding and adhesive bonding, so the energy it absorbed increased significantly.Three-point bending test showed that: the bending strength of laser spot weldbonded joints is highest, followed by the adhesive bonded joints', the laser spot welded joints'is smallest; the bending strength of J-11 adhesive bonded joints is higher than Terokal-5089 adhesive bonded joints'. T-peel test showed that: the peel strength of laser spot weldbonded joints is roughly same with the laser spot welded joints', the peel strength of adhesive bonded joints is very low. Fatigue test showed that the fatigue life of laser spot weldbonded joints is much higher than the laser spot welded joints'.