1) Selection of proper electrodes is a most important factor in order to secure good mechanical properties in arc-welded high manganese steels. Both 18Cr-8Ni and 16Mn-16Cr electrodes produced the most successful results; the oints welded with use of these electrodes showed the tensile strengths of 40kg/mm2 and above, with esnsiderable elongation. Other types of electrodes gave poor results; especially the mild steel electrode was found impracticable. Some improvements of mechanical properties could be expected by water-cooling each pass or welding with straight beads to avoid heat concentration. But arc welding did not particularly injure the mother metal, for the hardness of heat-affected zone was found not so high and the area was much limited. 2) Mn-Ni electrodes were superior to 18-8 and Mn-Cr electrodes for arc-welding high manganese steels and the following chemical content of deposited metal was recommended: C0.3% Mn 17% Ni 3.5% 3) Gas welding was inapplicable for welding high manganese steels because of very inferior mechanical properties of gas-welded joints as compared with those of arc welding. This is attributed to the existence of harder and remarkably wider heat-affected zones in the case of gas welding.
Welding heat Q and welding heat per unit deposition Q/w for recent electrodes were measured under some practical conditions by special water calorimeters. The experimental values obtained are shown in Table I and the tendency of Q and Q/w due to the type of electrodes is discussed in the frequency distribution diagram, Fig. 2.
This report states the results of the experiment attempted by the author to make clear the reasons wily each compound of metals having similar atomic weights shows wide difference in arc voltage (see Report 1, Fig. 1). The main points thus clarified are as follows: 1) Between instant arc voltage at constant arc lengh produced in oxides or carbonates (to be referred hereafter simply as instant arc voltage of compounds) and atomic weight of metal element of these compounds the same relations are observed as were shown in the experiment of the stationary arc voltage by coated electrodes, to which the author earlier referred in Report I (to be mentioned hereafter simply as stationary arc voltage of compounds) concerning the periodic law group to which the metal belongs. 2) Curvilinear relations are observed between instant or stationary arc voltage and effective radius of metal ions of compounds, excepting those liable to decomposition at low temperatures. 3) Instant or stationary arc voltage has also curvilinear relations with the distance between the two atoms of metal element and of oxygen element in the compounds, excepting those liavle to decomposition at low temperatures. 4) From the above observations inferred that instant or arc voltage is closely related with electron ionization.
Following the last report, the authors studied on another function of cover plate from the standpoint of elastic stability of thin circular plate heated at the centre. The differential equation for defic tion surface is approximately solved in the form of converging series. The critical load and the critical temperature are respectively shown in Figs 3 and 4. As seen in Fig 4 the critical temperature decreases as h/a decreases, where Ii and a denote thickness of plate and radius of heated zone respectively. It became clear that cover plate is used for prevention of buckling.