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An assessment is made of the electroslag remelting (ESR) and plasma arc melting (PAM) technologies used in the United States in manufacturing a variety of materials and sizes of ingots. Significant metal quality improvements in surface condition, mechanical properties, solidification, structure cleanliness, and yield over air-melted material have accelerated ESR usage, particularly abroad. PAM has potential in recycling scrap, producing complex alloys, large monocrystals of refractory metals and their alloys, and independent control of heat input and metal feed. ESR has found steels, providing features such as desulfurization, retention of volatile alloying elements, and the capability to produce shaped ingots and castings.
The book describes the method of remelting consumable electrodes with an electric are burning between the surface of a liquid slag bath and a consumable electrode in a water-cooled copper mould. The method combines the possibilities of treatment of liquid metal with the electric arc in the gas atmosphere and the liquid slag and the advantages of plasma-arc and electro slag remelting. The technological possibilities, design features of melting systems and results of experimental and industrial melting trials of steels and alloys are described. In addition to remelting structural steels, special attention is given to the possibility of alloying the metal with nitrogen from the gas phase, without using expensive nitrogen-bearing nonmetallic compounds, e.g. silicon nitride. It is shown that arc slag remelting can also be used efficiently in producing ingots of titanium and its alloys. The results obtained in this method are compared with electro slag remelting and plasma arc remelting. Data on energy consumption and metal quality are also presented.
Dr. Boris Medovar, a member of the Soviet Academy of Sciences, is a promi nent member of the E.O. Paton Electric Welding Institute in Kiev, one of the pre-eminent institutes of the USSR. The Paton Institute, internationally famous for its entrepreneurial efforts in electrical welding processes, is also famous for its application of electrically based processes in melting and remelting of high alloy and high-temperature materials. These include the ESR (electroslag re melting) process, the ESC (electroslag casting) process, skull remelting based on electron-beam processes, plasma arc processes, and electric arc processes. Along with the ESR process for ingot production is the commercial plasma arc remelt process for specialty steels, particularly where high nitrogen contents may be desired, as in austenitic stainless steels. Major industrial centers are now scattered throughout the USSR and are a major factor in high-alloy, high strength, low- and high-temperature materials. The ESR process was developed in response to the Western development of the VAR (vacuum arc remelting) process for producing very highly alloyed materials during the growth period of the jet engine age. The V AR and ESR processes utilize different purification and refinement processes that are extremely critical in very highly, complexly alloyed superalloys and high-speed tool steels. In water-cooled remelt systems, they also achieve relatively rapid (directional) solidification, minimizing segregation and coarse phase separation of undesir able impurity elements or elements that tend to form coarse brittle phases.
Vacuum plasma-arc melting has the following advantages over vacuum arc melting with the consumable electrode: the possibility of the remelting of lump, noncompact charge; the possibility of the velocity control of melting, maintaining metal in the molten state and, therefore, its additional degassing; and, simpler vacuum equipment. Plasma-arc melting in vacuum (0.4-0.5 mm Hg.) has advantages over plasma-arc melting in weakly rarefied atmosphere (75-100 mm Hg.): the higher degree of degassing of melt; the higher thermal efficiency of process; the less consumption of working gas; the possibility of using low-voltage current sources for vacuum arc furnaces.
One of the largest, most complicated and expensive environmental problems in the United States is the cleanup of nuclear wastes. The US Department of Energy (DOE) has approximately 4,000 contaminated sites covering tens of thousands of acres and replete with contaminated hazardous or radioactive waste, soil, or structures. In addition to high-level waste, it has more than 250,000 cubic meters of transuranic waste and millions of cubic meters of low-level radio-active waste. In addition, DOE is responsible for thousands of facilities awaiting decontamination, decommissioning, and dismantling. DOE and its predecessors have been involved in the management of radioactive wastes since 1943, when such wastes were first generated in significant quantities as by-products of nuclear weapons production. Waste connected with DOE's nuclear weapons complex has been accumulating as a result of various operations spanning over five decades. The cost estimates for nuclear waste cleanup in the United States have been rapidly rising. It has recently been estimated to be in a range from $200 to $350 billion. Costs could vary considerably based on future philosophies as to whether to isolate certain sites (the ""iron fence"" philosophy), or clean them up to a pristine condition (the ""greenfields"" philosophy). Funding will also be based on Congressional action that may reduce environmental cleanup, based on budget considerations.