Not only the hardened zone is detected in the welded part of high carbon steel, but sometimes also the welding crack appears in them. In this research the author has studied to find the welding condition that is to mitigate hardening or to prevent weld crack.
Three kinds of high carbon steel contained: C 0.40%, 0.55% and 0.76% respectively, has been applied to various tests.
The weld hardening and the crack generation are mainly affected by the carbon content and cooling velocity. The more the carbon content in steel, the more the number of crack or the length of crack on bead. The cooling velocity, in welding practice, has two important factors that is to say electric current and welding speed.
The author has found two kinds of crack or fissure on-bead. Tlhe former is generated by shrinkage stress, transformation stress etc. and the latter is mainly caused by transformation stress as due to the local. formation of martensite at comparative low temperature. From the result of various tests it is cor.cluded for prevention of crack generation that is to apply such a welding condition as slow speed and low current as possible. Preheating is also effective on the above purpose.
As an example of practical application of the above tests, building up of worn tyres has been excuted as well as in the test condition and this repair practice has proved the superior results in the both side of theoretical tests and practical uses.
Since at the point of welding all temperatures may be present from that of liquid metal to steel at normal temperature, these effects may be quite complicated.
As one of the fundamental researches on the effect of welding heat, the hardness distributions, produced in high carbon steel specimens by short time heating in lead bath. and quenching in water or air cooling have been determined.
From these results, the heat effects in welded part may be approximately considered in the relation between the maximum heated temperature and hardness or microstructure.

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It is possible that the electrode metal transferee upward to the base metal in the particle form in some electrodes with the refractory coatings when the current is sufficiently large to produce the gas stream of high velocity, which is essential to generate the particles from the snout like tip of the coated electrode. See photographs No. 1-4.
In the case of flat welding, tiny explosions from the electrode tip are observable in some electrodes as Citogen, Teisan No. 18 (see Fig. 7), but the occurences of these explosions are rare in the over head welding. The reason of the above mentioned difference is supposed that the fresh metal and the slug are always on the surface of the molten tip in the case of the flat welding, due to the regular successive transference of the tip material.
The tip metal transferes only during the mechanical contact between the electrode and the base metal in the case of ordinary electrodes. Fig. 13 illustrates the typical motions of the molten base metal in relation to the making and breaking of the contact in the case of the bare electrode. See photographs No. 5-10 and the accompanying oscillograms. The authors suppose that the motion of the molten part is the result of the generation of gas or vapour inside the metal.
In the case of the coated electrodes of some type, the number of the short circuit occurrences is small and the duration of a short circuit is long, because the motion of the molten part is inactivated by the protecting action of the coating. Fig. 17 shows the short circuit durations of the bare electrode in the case of flat and over head welding, and Fig. 18 shows those of a coated electrode "Y". In the case of electrodes of slug shield type, the durations of the short circuit are short compared with thee bare electrode. See Fig. 23.Hilpert's report is supposed to correspond to this case.
Conrady says that the mechanism of the short circuit is explained by the reactin of the force acting on the cathode spot. Fig 33 is the illustration given by Conrady showing the motions of the electrode tip due to. the reaction force, but such motions are never observed by our clear photographs. As described preveously the authors suppose the motions are the result of the generation of gas or vapour inside the molten metal. We can see the motions of the base metal side in photos No. 5, 6, 7, and also in photos No. 10-13, and those of the electrode side in photos No. 24, 25 and others.
It is already reported in a preveous paper that the pinch effect has little effect on the phenomena of the material transference.
The phenomena of Fig. 31, which is indicated. and discussed by Hilpert and Conrady, are discussed and explained in the main report.

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