Recently the smaller and light product is interested in the industry application that increasing demand for thin plate joints of 1.0 mm or less in thickness using friction stir welding. In this study, high frequency spindle form 3500 rpm to 6500 rpm was introduced for thin friction stir welded plate. Weldability tests are performed for butt-joint method of Al5052-H32 alloy having 1.0 mm thickness under spindle revolution of 3500 rpm ~ 6500 rpm and welding speed of 250 mm/min ~ 400 mm/min. The optical microscope was analyzed bid structure of welded zone and stir zone. Then tensile-strength and hardness of welded zone were measured.
High-rigidity structure with high-speed spindle and tapered bearing, and vacuum chuck, it is easy to bond aluminum material of 1.0 mm thickness at 6500 rpm at tool rotation speed of 3500 rpm and 400 mm / min at bonding speed of 250 mm / min. I was able to. From these conditions, it was possible to obtain the effect of improving the bonding efficiency by the high speed friction stir welding.
The tensile strength values of the aluminum 5052-H32 alloys were 60-70% of the tensile strength of the bonding material under all joining conditions. The elongation was 30 ~ 40% of the base material. Especially, at 6500 rpm, the tensile strength increased with increasing bonding speed, and the tensile strength was similar to the tensile strength at 3000 rpm or less. Through this, it was confirmed that the high tensile strength of the tool can be maintained under fast bonding speed.
The variation of the hardness value does not appear much with the variation of the tool rotation speed 3500 to 6500 rpm. Also, as in the case of joining at 3000 rpm or less, both the joint and the heat affected part have a lower tensile strength value than the material and have a lower heat heat part than the joint part. Also, the hardness value of the backward part was higher than that of the forward part.
As a result of observing the microstructure when the heat input is low, only the portion where the probe and the shoulder directly bend are thinly and locally stirred, and the heat affected portion is also thin. Also, the fluidity of the bonded material is low and the occurrence of burr is small, and the thickness of the bonded portion is hardly changed. When the heat input is high, the agitation part is formed thick and wide and the heat affected part is formed widely. As the fluidity increases, the burrs generated by the centrifugal force increase and the thickness of the joint becomes thinner.