System for vacuum degassing of open-hearth steel: From construction to mastery of the technology

Abstract

An essential element of any modern technology for the production of metal for transport vehicles --including railroad wheels --is treatment of the metal outside the furnace and its vacuum degassing. There are several methods of vacuum degassing in use, each having its advantages and disadvantages. The ladle method was chosen for the open-hearth shop at the Nizhnedneprovsk Pipe Plant, due to the specifics of OH steelmaking and the limited potential for obtaining a low-sulfur product on the one hand and, on the other hand, the increasing demand for low-sulfur steel in the world market.The following must be done for successful vacuum degassing: prevent furnace slag from entering the ladle or remove it if it does; provide for additional heating of the metal to compensate for the substantial heat loss from degassing and allow additional desulfurization with the introduction of slag-forming materials; correct the chemical composition of the metal, if necessary. The degassing system also provides for blowing of the metal with argon.These operations are performed on a "furnace-ladle" unit. The nature of the operations described above shows that the vacuum-degassing unit is actually a complex of equipment which in addition to the basic components includes a high-voltage substation with a filter-compensation unit, a water recycling system, a waste-beat boiler, a draft system for removing and cleaning outgoing gases, a section for monitoring the concentrations of gases dissolved in the metal, and other important components. The plant contracted with the Mannesman--Demag company to build such a system at its facility. The equipment layout was the responsibility of Ukrgipromez (Ukrainian State Institute for the Planning of Metallurgical Plants).In order to fit the equipment into the open-hearth shop, OH furnace No. 1 was taken out of service, while OH furnace Nos. 2 and 3 were provided with oscillating chutes to control the distribution of metal and divert the furnace slag. All of the equipment of the complex was supplied by subcontractors of Mannesman--Demag.Except for a few operations, the entire complex is completely automated. All of its components can be controlled from the central control post. Accomplishing this required the use of special programs, sophisticated computer technology, and debugging routines. The contract provides for two levels of system automation. All information on the condition of the controlsystem components and the measured process parameters is displayed on three monitors positioned in front of the operator. The computer keyboard is used to retrieve needed data to the monitor screen and control the system elements. The first level of the system provides for visual recording of process parameters, while the second level records the parameters in the memory of a special computer, retrieves cumulative data to the screen at the operator's request, and prints it out on demand.The process equipment and the hardware and software of the automatic control system (ACS), delivered, installed, and now being ...

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“…- (Gulyj et al, 1996). Η επεξεργασία στο θερµαινόµενο κάδο γίνεται προκειµένου να «καθαριστεί» το µέταλλο.…”