1965 Volume 34 Issue 2 Pages 146-153
Authors investigated the influence of the various welding condition on the shape of penetration surface caused by TIG arc torch fixed perpendiculer to the mild steel plate. After discussing the results obtained we have come to the following conclusions.
(1) The surface of penetration obtained was roughly one of revolution and its sectional profile was clearly divided into three groups, that is, peripheral, central and simple type. Penetration in p type consists of deep peripheral groove and shallow and flat bottom at the center part. Much deeper center hollow is added to the former in case of c type. Sectional profile curve in s type is of simply concaved arc.
(2) Type of penetration changes abruptly from p to c as welding current is increased or arc length is decreased. Stype seems to be formed when the arc and mother drop is unstable.
(3) Authors proposed as a probable hypothesis that the deep peripheral groove in p type is originated from the strong outerward surface flow of over-heated molten metal caused by the difference of surface tension under the arc.
(4) If the contral depression of molten metal surface, caused by plasma jet stream or abovementioned surface flow, become deep enough to reach the bottom of penetration, then the direct action of the arc begins to act on the bare surface of base plate forming the central deep penetration
(5) If the contact angle of molten metal on the solid metal has a definit value being not zero, occurence of the bare surface is not continuous to the welding condition, jumping up to a certain wide range from zero, which may satisfactorily explain the discontinuity of the change of penetration type.