Penetration Phenomena of Organic Solid

Interfacial Tention Theory on the Phenomena of Arc Welding (Chapter 11)

Abstract

The author has discusssed about various phenomena in penetration with paraffin and stearic acid in case of the heat source directly contacting them, and concludes as follows:
1. Strong convection flowing within the molten pool is caused by the strong surface flow due to the difference of surface tension by heating a part of molten surface.
2. The type of convection changes according to the shape of heat source, heat input, heating time and the kind of material, and this determines the shape of penetration.
The same shape of penetration is obtained by the same type of convection regardless of its cause.
1) There occurs a very little convection if the surface of molten pool is immovable.
In this case, the shape of penetration is a semicircle which seems to be explained by "Heat Conduction Theory".
2) "Pa" type penetration by point heat source and peripheral penetration by disk heat source have a strong resemblance to the shape of penetration with mild steel by fixed TIG arc, and all of these penetration shapes seem to be brought about by the same cause.
3) Deep simple penetration shape with mild steel can not be explained by the surface tension convection radially flowing from center part. For explaining this type of penetration, the existence of another type of convection such as flows vertically at center part may be necessary.
3. As for the temperature, it is the highest at the center part of vortex, and goes gradually down toward the surface of penetration, when the convection due to surface tension exists in the molten pool.
4. From the results of various measurements on the angle of penetration and the shape of molten drop, the reasonable contact angle of molten paraffin and stearic acid as well as of solid state is estimated. This fact shows that the shape of penetration can be anticipated from the contact angle of the material.