Seeing the macro-structure of electro-slag welded Cr-Mo steels, its grain size is finer as compared with ASTM A 302 B. This is because the plate thickness of Cr-Mo steel is thinner and its cooling velocity is faster than ASTM A 302 B. grain growth of deposit-metal which is shortcoming of electro-slag welding becomes more remarkably in proportion to increase of thickness. On the otherhand, we decided to do experiment to apply normalized & tempered heat-treatment to electro-slag welded joint of Cr-Mo steels in view of special steel and to appy severe condition. As the result of normalized & tempered heat-treatment, impact value (especially notch toughness) has been increased. Improvement of deposit metal is most conspicuous among various structures of welded joint. Impact Vlalue of large size specimens which are 40 mm square show no difference between these steels and ASTM 302B as welded, but the former were as heat-treated. So that, to make conclusion from the impact value of 10 mm square specimen is supposed to be unreasonable. In near future, we are to make transiticn curves of these steels & ASTM 302B by large size impact specimens. Changes of mechanical properties of electro-slag welded, normalized and tempered Cr-Mo steels by wires and fluxes which were on sale, were studied and following were found. (1) Quantity of oxygen contained in electro-slag depositmetal increase according to its grain growth. (2) Tensile-strength of electro-slag welded joint normalized by cooling velocity of faster than 300°C/h and tempered is satisfied with the minimum value of specification. (3) Impact value increases according to the speed of cooling velocity in normalizing and its transition curve moves to lower temperature side. The best normalizing temperature of 1 Cr-0.5 Mo steel is 900°C (4) Bend test of electro-slag welded specimens shows no crack when normalized and tempered but crack as welded. (5) High temperature tensile strength of normalized and tempered welded joint is satisfied with specification as well as the strength of base metal. (6) Fatigue test result of electro slag welded joint at the same value of base metal are satisfactory.
The factors which decicde the character of the low pressure type gas welding or cutting torch are considered as follows : (a) the external factors the supplied oxygen pressure and the supplied acetylene pressure, (b) the inner factors the combinations of the parts of the injector, and the relations between the conditions of oxygen jet stream and the combinations of injector components. In the previous retort, authors investigated the influence of the external factors on the mixed ratio of the flame. In this report, the experiments were made on the effect of the two injector components which were defined in the report 1.-the diameter of the oxygen nozzle and length of the injecting part. The results of the experiments are as follows : the energy of the oxygen jet stream at the entrance of the mixing part had greater influence on the P4 pressure than the energy at the exit of the oxygen nozzl. Having the shortest injecting part or the smallest diameter of the mixing part, the injector could give the lower P4 pressure. In the next combinations of the injector components the lowest p4 pressure was given ; (i ) D=1.2mmφ, l=2.8-3.8mm, to d=0.46mmφ (ii) D=1.2-1.4mmφ, l=1.8mm to d=0.60mmφ (iii) D=1.2-1.4mmφ, l=1.8mm to d=0.99mmφ
Although it belongs to a very fundamental problem in spot welding, it is not yet definitely determined what percentage of the total energy supplied escapes to electrode tips. We investigated this problem on the spot welding of mild steel sheet of 0.6 mm to 3.2 mm thickness under the welding conditions specified by R.W.M.A. By measuring the welding current and voltage, the total supplied heat capacity was calculated by using H=0.24 IVt(cal.). By the amount of cooling water for electrode tips and its temperature rise in stationary condition, the calorie conducted to electrode tips was obtained. The calorie used in producing nugget and conducted to sheet from the peripheral of nugget was calculated from the temperature rise of the water in which the test piece had been dipped. Thus by determining the individual calorie escaping to each part and the total supplied calorie, the percentage of the calories escaping to electrode tips in the total calories supplied could be roughly estimated. The result proved that the heat loss to the electrode tips depends merely on the sheet thickness and has nothing to do with the welding conditions, A.B.C.