| I. Introduction ESR(Electro-Slag Remelting) was, as you know well invented in USSR in about 1954 and industrialized. In Japan, at the end of 1961 (according to my memories), one trading company introduced us the license of this ESR process (telling us that this invention was already patented in Sweden, France, D.F.R., England, USA and Canada). In 1963/1964, USSR MACHINO EXPORT recommended to bind the technical license with Japanese companies through the other trading company (In these duration Kobe Steel Co. contacted directly with USSR about ESR). But license fee was too expensive than we expected So that, in Japan Special Steel Co., we decided to design and to establish the ESR furnace by ourselves, and began to construct the test furnace, at first 20㎏, then in succession 100㎏ capacity, utilizing and reconstructing the old one ton capacity electric arc furnace which was installed in casting shop. We had many difficult experiences to make clear the optimum conditions to obtain the good ingots. Our little paper listed in TETSU-TO-HAGANE, Vol. 50 (1964), No. 11, p. 1780 is the first report of the technical operation data which was published upon ESR in Japan. After these bitter practical test researches Japan Special Steel Co. established 1 Ton and then in succession 4 Ton capacity ESR furnaces by our own designs and constructors. In the other side, about the patent of this process, USSR made an application in Nov. 2. 1961, and after the judgement the content of this application was officially notified in Nov. 30. 1966. The protests continued between USSR and us till Nov. 14, 1969, when they withdrew their application in Japan after 8 years in total. In about 10 years from our first test furnace construction, not only in Japan but also almost all over the world, ESR process made much progress and still now is being studied very vigorously, of course the number of furnaces installed by the professional furnace makers increased very much. 2. Classification of ESR The kinds of steels produced by ESR are; (1) The high alloy special steels, for example, tool steels, stainless and heat-resistant super alloy steels. (2) The construction steels. (3) The high tensile strength steels and other special purpose steels. The ingots produced by ESR are; (a) Relatively smaller round or square ingots which are to be forged or rolled (generally <1-5Ton). (b) Relatively larger round or rectangular ingots for the large forgings by press-forge(generally <15-25 Ton or more). (c) The giant slab ingots for the extra large forgings or for the extra heavy ultra-thick plates, for example, to be used for the reactor vessels (generally <150 Ton or more). And ordinarily (a) is applied for (1), but (b) and (c) for (2) or (3), particularly (c) is a new trend of ESR and now adapted or being investigated by the large steel makers, for example, USSR (Dnieprospetzstahl), Rheinstahl (Heraeus), Bo¨hler, Consarc Corp., Nippon Steel Corp., Kobe Steel Co., etc. Of course, to produce these large ingots, the multiple-bifilated electrodes are used. But I want here to talk mainly about(1)-(a)-monofilar system. 3. Characteristics of ESR. ESR is often compared with VAR (Vacuum Arc Remelting). The same points are: (1) The molten baths are protected from the contamination of the atmosphere, that is, in VAR, by the vacuum and in ESR, by the molten flux. (2) The molten baths coagulate layer by layer from the bottom in the water cooled Cu-moulds. The inner structures of the ingots due to this process improve the material qualities. Next the characteristic points of ESR different from VAR are; (1) The heat-source is the electrical resistance heat of the molten flux. So that we can control the electric power of melting continuously to zero. This perfects the hottop effect to remove the shrinkage cavities. (2) Almost complete metal-slag reactions at their boundary surfaces when the droplets of molten steels drop through the molten fluxes. In the consequence |
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