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Friction stir welding (FSW) is a new welding process developed at The Welding Institute in Cambridge, U.K. This process uses a non-consumable rotating third body to generate frictional heat and create forging to facilitate continuous solid-state joints. In this paper, the current state of the art of FSW is discussed. A preliminary description of the process is provided, followed by the results of some relatively simple thermal modeling. The modeling results are used to provide a description of temperature distributions in FSW, as well as illustrate the effects of variations in process conditions. Representative microstructures of FSW on an Al 6061 alloy are then presented. Properties of these friction stir welds are then discussed and compared to those of both the base metal and to comparable GTAW welds. Some discussion is then given to the effects of section thickness on FSW. Examples are given of friction stir welds on aluminum alloys ranging from 2 to 30 mm in thickness.

Resistance welding control systems utilizing secondary current feedback receive widespread utilization both in Europe and Japan. However, these types of control systems are only beginning to be used in any extended basis in this country. Currently, two variants of these systems are available; so called “self-teaching” systems, and “learning curve” systems. Either system has been shown to be capable of providing a stable secondary resistance welding current within two cycles. Recent work has indicated, however, that the self-teaching type control systems may be adversely affected by non-optimum set-up conditions, particularly poor fit-up and the introduction of organics (sealers or adhesives) at the faying surface. This work examines the performance of learning curve type constant current control systems under these adverse set-up conditions. Six conditions were selected for study; three degrees of progressively poorer fit-up, with and without an organic sealer.

This study was conducted to examine the effect of flashing conditions on the resulting temperature profile during flash welding automobile door frames. Previous work on temperature profiles of flash welds has shown that at some point in the welding cycle a steady state temperature is reached, minimizing the need for further flashing. The indication of such a minimum flashing time allows flashing conditions for any application to be optimized. Unfortunately, previous work has been limited to rather heavy section materials, and the results could not be directly applied to the flash welding thin sections typical for door frames. This program was a preliminary study to examine the effects of initial flashing velocity and flashing acceleration on the resulting temperature profiles in U-shaped channel sections. Work was done on a cam driven flash welding machine supplied. Flashing conditions were varied by using cams with different profiles.

This paper is a continuation of previous work on the effects of tap setting and percent heat on the weldability of galvanized steel. A previous work dealt with changes in current range behavior. This paper considers changes in nugget development. Six separate tap settings were selected for study corresponding to a range of off-times in the current wave form at expulsion. Welds were then made at each tap setting for increasing weld times and sectioned metallographically. It was found that the change in off-time led to significant changes in the morphology, size and rate of weld growth. These results were explained in some degree through changes in the mechanism of resistance heating for various off-times.

This study examined the effect of primers containing a conductive pigment on the resistance spot weldability of hot-dip galvanized steel. The pigment used was ferrophos, essentially Di-iron phosphide. Basically, two types of tests were used in this work. Current range tests were used to establish the effect these primers have on the effective ranges of weldability. Limited electrode life tests were used to infer the long term performance of the hot-dip galvanized steels with and without this paint. It was found that the addition of the Ferrophos bearing paints had pronounced effects on weldability. Typically, required current levels were reduced by several thousand amps, and effective current ranges were increased by 50 to 100 percent. During electrode life testing significant reductions were also noted both in the rates of electrode face diameter increase, and the degree of electrode pitting.