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On welding, metals science and metallurgy in the scientist heritage or on present status and future of special electrometallurgy.

On 29th of March 2006 uncommon man and prominent welder-scientist, metal scientist and metallurgist, academician of the NAS of Ukraine Boris I. Medovar (1916--2000) would have been 90. Bibliographic publication, issued in 1986 to his 70th anniversary, rather fully represents life and creativity of the scientist . Last 14 years of his life the scientist continued to work selflessly, first of all over the main topic of all his scientific activity--ESR. ESR and the whole range of scientific and practical problems connected with his favorite work remained till the end of life of B.I. Medovar the backbone of his scientific interests. Despite idle talks that ESR is not needed by state-of-the-art metallurgy, he continued purposeful investigations in this field, because he understood well both world trends in development of special electrometallurgy and place of ESR in production of steels and alloys for so called <<critical application>>.

In the ocean of steel, which is annually produced by mankind, share of the electroslag metal makes up only 800 ths t. In other words, a little bit less than 0.1 %. But the fact that without this seemingly negligibly small volume, a drop in the ocean of metal, state-of-the-art engineering, first of all power engineering, is impossible, was understood by the scientist as far back as in early 1970s of the previous century. Already at that time B.I. Medovar publicly stated that ESR had great prospects, because only ESR ensured the highest local rate of solidification in comparison with other processes of special electrometallurgy and, as a result, higher hot plasticity of super alloys--alloys, which determined progress in power engineering and the whole life activity of people.

Really, after short-term reduction of volumes of production and investments, caused by termination of cold war, stable growth in special electrometallurgy (including ESR) has been continued for 10 years. In particular, production of metals using remelting processes has been annually increased within this period on average by 4--5 %. This growth is achieved due to maximally efficient use of available capacities and construction of new furnaces.

So, according to different sources, within these 10 years more than 10 ESR furnaces were built in industrially developed countries, firs of all furnaces of chamber type, designed for production of super-alloys and high-alloy steels of <<energy designation>>. Moreover, Austrian colleagues were able to implement on commercial scale developed in PWI under guidance of B.I. Medovar process called by him ESR DC (ESR with double-circuit scheme of power supply) in which one power supply circuit is a traditional chain represented by the transformer--short circuit--consumable electrode--slag pool--metal pool--ingot--bottom plate-short circuit--transformer, and second power supply circuit is represented by the second transformer--short circuit--current carrying mould--slag pool--metal pool--... and than may be implemented one of numerous versions of a circuit closure both on the mould proper, on an ingot--bottom plate--transformer and using any other physically possible method.

In Figure 1, a the most tested by now scheme of ESR DC implementation is presented.

Peculiar feature of the ESR DC process is break of rigid ratio between supplied to the metal being re-melted power and rate of the ingot build-up. So, implementation of ESR DC allows performing melting of alloys, which are especially sensitive to various kinds of segregation processes, first of all super-alloys, under much more favorable conditions than in classical processes of remelting.

In Figure 1, b longitudinal section of an ingot molten from practically flat form of bi-phase zone is presented as example of ESR DC possibilities. We assume that exactly these works of B.I. Medovar have nowadays principal significance for power engineering industry and energy safety of the country. Because, as showed course of science and technology development, nowadays and in near future power plant engineering industry will need big forged pieces from high-alloy steels and alloys for rotors and disks of steam and gas turbines. In particular, for heat-electric generation plants of Ukraine and CIS countries temperature of live steam 540--550 [degrees]C is characteristic as before, while developed countries transfer their heat power stations at working temperatures 625-650 [degrees]C. For using such temperatures steels with base composition 12 % Cr--1.5 % W are needed. Rotors of steam turbines from such steels are manufactured nowadays only from ESR ingots of 100 t and higher mass. Moreover, flat solidification front, ensured by ESR DC, allows implementing old ideas of developing a rotor of changeable over its length chemical composition.


But steam turbines are just a part of state-of-the-art power engineering industry, in which gas power engineering turbines acquire ever growing significance. Metal for gas turbines is also mainly the metal produced by the methods of special electrometallurgy. What is special electrometallurgy (SEM) nowadays? In which form is it and will be connected with power engineering in near future? In Figure 2 * interconnection of main SEM technological processes and principal possibilities of enterprises of Ukraine in production of billets of rotors and state-of-the-art turbine disks are shown.

Production of steels and alloys for power engineering industry is based on triple or double remelting according to the scheme VIM--ESR--VAR or VIM-ESR or ESR of the open melting metal and out-of-furnace treatment, including vacuum one. Metallurgic basis of existing power engineering industry of Ukraine and majority of industrially developed countries was formed more than 30 years ago. The basis of power engineering metallurgy in the USSR and Ukraine had to become and became Kramatorsk Machine-Building Center--pride of national machine building industry Novo-Kramatorsk Machine-Building Works and Plant of Castings and Forged Pieces (LIP), which is called nowadays <<Energomashspetsstal>>. Unfortunately, it is impossible to start at present in Ukraine (or any CIS country) production of state-of-the-art steam and gas turbines from the national metal, because the metallurgists lack respective equipment. But in the works of our institute carried out under guidance of B.I. Medovar during last years of his life and proposed after his death scientific basis of ESR of steels and alloys for state-of-the-art power engineering industry was developed. Moreover, taking into account application in power engineering industry of more and more sensitive to zonal segregation alloys, in this works bases for the electroslag enlargement of ingots, practically to any needed by the power engineering industry workers size, was laid with a margin for future.

There are several especially favorite objects of investigation on long creative way of the academician.



Rather many of them are connected with welding, especially with welding of pipes of big diameter and welding of high-temperature austenite steels and alloys. But his approach to the metals science was based not just on deep theoretical knowledge, but also on real knowledge of the industry and understanding of its needs and trends of development. Having combined in one person experience and knowledge of a metals scientist, a welder and a metallurgist, talent of a researcher-experimenter, and sharp-sighted eye of an engineer, the academician dealt for the whole his life with the most acute problems in his field of science and engineering, being even not at the <<spearhead>>, but ahead of the <<spearhead>> of the main attack.

Indefatigable thirst of new, constant interest to new tasks, ability to infect colleagues with his vision of problems and ways of their solution attracted to the scientist not just his employees, but also colleagues from other SRI and industrial enterprises (Figure 3). They joked sometimes in PWI that B.I. Medovar made the whole institute to work for him. It is quite evident that it is impossible to implement in the research institute this kind of fruitful joined efforts by administrative measures. People, who try to work creatively, are united only by common ideas. And he was always rich in ideas and was not afraid to share them. In addition, the academician had good capacity for teaching and was able to find and target at the research work capable youth. It is not without reason that among his disciples there are about one hundred candidates and more than two dozen doctors of sciences. His fantastic work capacity charged with energy his colleagues who worked side by side with him.

There are many examples, which show how bravely the scientist went against settled concepts. Perhaps the most striking of them is refusal from ESR of conventional structural low- and medium-alloyed steels. Before eyes of his disciples and numerous national and foreign <<ESRists>> B.I. Medovar clearly formulated and substantiated the need of using ESR not for refining steels and alloys from harmful impurities, but for <<refining the metal structure>> and control of shape, size, and distribution of metal and nonmetal structures in the metal. Ideas, connected with control of solidification of steels and alloys, constantly worried restless and inquisitive mind of the researcher. Exactly on this way various technologies of the electroslag casting and even new class of metal materials with assigned anisotropy of structure (AAS) and properties were born--AAS-reinforced quasi monolithic and quasi-lamellar steels.

Wonderful vision of the metals science problems of metallurgy allowed B.I. Medovar implementing interesting technical solutions not just on the basis of numerous experiments and deep studies, but also, it would seem <<on the tip of a pen>>. In this way low-carbon armor plate and such at present ordinary method as hardening of low-alloy steels of 09G2S type or controlled rolling of conventional carbon steels were born. The list could be continued, but following style of the scientist we shall note only one thing: at present one may state with confidence that ESR and the whole range of the electroslag technologies born in our institute with direct participation of B.I. Medovar dynamically develop, and his long work is continued by his disciples and followers.



E.O. Paton Electric Welding Institute, NASU, Kiev, Ukraine

* In continuation and development of the article published to jubilee of B.I. Medovar in journal <<Avtomaticheskaya Svarka>>, 2006, No. 3.

* Krylov, V. (2006) On energy safety of the country, Ukrainian metallurgical science and ... life! Metally, 3, pp. 50--51.
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Author:Paton, B.E.; Medovar, V.Ya; Saenko, A.K.; Tsykulenko, B.B.; Shevchenko, N.T.
Publication:Advances in Electrometallurgy
Date:Apr 1, 2006
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