The quality of spot welding of Aluminum alloys largely depends upon the surface condition of the faying surface of the materials. Therefore, the surface treatment is usually required in order to remove natural oxide films, for obtaining good spot welding quality. However, it has been said that the surface treatment contains many problems, such as, condition of laying surface, regulating the time up to the beginning of the welding after treatment, or control of treat solution, etc. Thus, new spot welding machine, in that good welding quality can be obtained without preparatory surface treatment, is devised and constructed. This report describes the process of studies have been made in designing this welding machine, also it gives some examples of the spot welding test results, or fabrication on Aircraft, from using this machine.
To obtain sound joints, it is considered that the vibration energy induced by transducer should be effectively transmitted to the contact face of materials to be joined so as to give enough relative motion (speed) to the contact face of materials. In this study, we have investigated about a relation between the joinability and the sheet length of materials to be joined, and obtained the following results. 1. In lap joining of aluminum with solenoid tip vibrating in the longitudinal direction of sheet length, good joints were obtained when longitudinal length of aluminum on tip side is an even times of 1/4 λ(λ : wave length in aluminum), if not so, successful joints are not obtained. However, we observed there is very little affect of sheet length of aluminum on anvil side on joining properties. 2. In lap joining of titanium with solenoid tip vibrating in the longitudinal direction of sheet length, we observed "hot spot and crack" near joined parts when titanium was a certain length.
Welding of steel with propane-oxygen flame became possible, when both the enriched oxygen flame and the welding rod containing sufficient deoxydizing elements were used. The objects of this investigation are to find out the proper ratio of volumetric flow rate of oxygen to propane in propane-oxygen flame for the greatest flame intensity to melt steel plate, and to find out another way to increase the intensity of the propane-oxygen flame. The intensity of flame was experimentally evaluated with the time to start meltintg in the same way described in the previous report. Three kinds of improved flames were examined as below. i) Thermal cracked propane-oxygen flame : propane begins to convert into hydrogen, methane, ethylene and propylen by thermal cracking at 600°C and is cracked completely at 900°C, ii) preheated propane-oxygen flame: the burning velocity of propan oxygen gas mixture becomes high by preheating under 550°C, and iii) propane-acetylene-oxygen flame: in place of a part of propane is added acetylen having higher burning velocity than propane. The results were shown as follows; 1) The effect of preheating on an increment of intensity of flame is the greatest of those of any other flames. The effect is obtained at lower preheating temperature than thermal cracking temperature. 2) Each minimum time to start melting of the propane-oxygen flame and three improved flames with various flow rate of oxygen is obtained at the location inside the inner cone with a stoichiometrical oxygen mixture for complete combustion.