Studies on Cold Pressure Welding (Report 1)

On the Cold Pressure Butt-Welding for Aluminium

Abstract

A method enabling metals to be welded at room temperature, called cold pressure welding has recently been developed.
This unique welding process without the use of heat or electricity, requiring only the simplest tools and permitting the use of unshilled operators, is evoked considerable interst thronghout industry.
The writers' study herein introduced, aimed at the cold pressure butt-welding for aluminium used for electrical industry.
The results of the experiment are summarized as follows :
(1) For the pressure welding, a cleaning method of the surface to be joined is most important. According to our experiments, the motor-driven rotary wire scratch-brushing treatment is most suitable for this purpose.
(2) The breaking strength of the butt-joint is depend upon the working degree of the specimens prepared for, that is, joint efficiency of cold pressure welding for annealed material is over 100%, but for cold drawn one is not so good. For example, the efficiency for 67% cold drawn specimen is about 97%.
(3) The "Figure of Merit" used to classify weldability for aluminium to aluminium is about 30. This values are same order to A. B. Sowter's data obtained from lap welding, reported in the Materials and Methods, Nov., 1948.
(4) The distance from sleeve end to the cleaned surface to be joined is affected on the breaking strength of the welded specimen for tension or torsion test. It was found that the longer distance is necessary to be obtained stable and complete welding and the suitable distance is about similer to the diameter of specimen.
(5) Distribution of micro-hardness of cold butt welds is measured. In case of cold drawn meterials, the hardness value of the portion separated 2-3 mm from the weld interface is lower than the value of specimen itself. It is thought that the cause of this phenomena is related to the "Bauschinger Effect".