軟ろうの濡れ易さと接触角について

抄録

Contact angle is an important factor which influences wettability of brazing alloy to base metal. Relation between wettability and contact angle was examined in this paper. Brazing alloys were set upon the horizontal base metal plates in vacuum as the first method. After brazing alloys were melted, the shapes of alloys spreading over base metals were photographed in phorizontal direction. Alloys which have eutectic point in their diagrams, such as Sn-Pb and Sn-Bi, have minimum contact angle to Cu at the composition a little nearer to Sn than eutectic. Alloys having nonmetalic element such as P, As have very small contact angles. Contact angle also decreases when alloy have small amount of base metal element.
As second method, following experiment was done. Slitts, composed of parallel base metal plates, were preheated in soldering flux. After holding them several miniutes at test temperature, the slitts were inserted vertically into molton brazing alloy under flux. Rights of the capillary rises and contact angles wera measured from X-ray radiographs. Contact angles and their decreases with temperature rise were very small in flux compared to in vacuum. It was obtained from the shape of sessile drop that surface tension of Sn in ZnCl₂ at 300°C was smaller than in vacuum about 30%. Hight of capillary rise increases with test temperature increasing. Though this phenomenon is considered largely due to decrease of contact angle, authers could not determine it with X-ray radiographs.