Spotwelding and Seamwelding the Aluminum Alloys 370130
THE potential economies that are possible in electric-resistance-welding structural parts made from the aluminum alloys have been realized to a limited extent. Considerable development work already has established the fundamental equipment requisites for making welds, and the characteristics of the various alloys from the standpoint of strength and corrosion resistance of the welds.
Some of the applications from which satisfactory service is being obtained with spotwelded and seamwelded parts include airplane and bus gasoline and water tanks, bridge flooring, cooking utensils, radio-equipment racks - in fact, the process is adaptable to the assembly of any parts with a section thickness of less than 3/16 in. which, in past practice, have been riveted.
Proper equipment is essential to obtain sound, consistent welds in the shop. For general work we have found that a machine with a 42-in. throat that will deliver a current of 42,000 amp. at the tips can be adapted to a varied jobbing production. Pressure is applied pneumatically up to a maximum of 1200 lb. at the tips. Full electronic timing is desirable for spotwelding and is essential for seamwelding. Good spotwelding results also can be obtained with vacuum-tube or mechanically controlled contactors for some classes of work.
The strength of welds in the various aluminum alloys is dependent on the alloy being welded and on the temper and gage of the material. The static shear strength and the resistance to vibration or fatigue loading of spotwelds are comparable to rivets. Salt-spray and atmospheric-corrosion tests have indicated that the corrosion resistance of the welds is substantially as good as the parent material. Complete data on all combinations of gages and alloys have not as yet been collected. Tables and curves on some of the commonly used alloys are shown in the paper.