Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 3. The picture of bath blowing at application two-level oxygen lances

Further increase of resources- and energy-saving efficiency of BOF processes is unthinkable without development of new methods of blowing and designs of blowing devices. It requires information on the real physicochemical phenomena in the converter cavity accompanying the blowing of the converter bath using new designs of oxygen lances in order to assess the possible risks in the mastering of the proposed developments in industrial conditions. The paper presents the results of video filming of the top blowing of a 80-kg converter bath by groups of multi-pulse supersonic and sonic oxygen jets formed, respectively, by Laval and cylindrical two-level nozzles of two designs equipped with double-row tips with a circular arrangement of Laval nozzles and cylindrical ones and upper block with cylindrical nozzles. Previously unknown information was obtained on the picture of the bath blowing with the formation of a reaction zone of interaction of supersonic and sonic oxygen jets with a metal melt with a flow of carbon monoxide going out the bath and afterburning of CO to CO2 under conditions of a counter-directed double curtain of sonic oxygen jets at different levels of location of the foamed slag-metal emulsions. It was established that in the initial period of blowing during slag formation most of the thermal energy of CO to CO2 combustion flares is transferred to the surface of the bath with lumps of added lime, and the rest is transferred by forced convection to the converter walls and gases escaping from the bath to the neck. In the case of the location of the foamed slag level at the upper tier of the cylindrical nozzles of the lance, heat transfer from high-temperature flares of localized afterburning of CO to CO2 within a limited in size near-lance flow of exhaust gases from the reaction zone is carried out according to the laws of submerged combustion and is completed completely in foamed slag-metal emulsion with the prevention of aggressive action of afterburning flares and volumes of overheated slag on the converter lining. Revealed and recorded by video recording modes of blowing the converter bath, contributing to the development of such undesirable phenomena during smelting as the appearance of intense emissions of slag-metal suspension from the facility, coagulation of the slag with the cessation of dephosphorization of the metal melt, the development of intense dust formation and the removal of small metal particles and slag with the formation of crust on the lance barrel. A variant of the final stage of blowing with a transition to supplying nitrogen instead of oxygen through cylindrical nozzles of two-level lances was experimentally tested, which provides an effective reduction in the level of foamed slag-metal emulsion before the converter turning down. The data obtained were used in the development of an industrial design of a two-level lance with a double-row tip, blowing and slag modes of blowing a converter bath with its use.

Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 1. Facility and methodology of the study

Interaction of the upper oxygen jets with the BOF bath considerably effects the hot metal refining flow. To optimize the lances designs and methods of BOF bath blowing, information is needed on the actual physical and technical phenomena taking place during top blowing of BOF bath by groups of ultrasonic and sonic oxygen jets. It was shown that obtaining the information is possible at high temperature simulation of the BOF bath blowing by application oxygen lances of various designs and video registration. Results of previous studies by filming of the blowing in a BOF and OHF presented. Description of modern facilities of high temperature simulation within a multi-purpose 160 and 60‒80 kg BOFs, equipped by special manholes for observation and registration by video camera the physicochemical processes taking place on the surface of the bath presented. In particular the manholes made it possible to observe the processes taking place at various methods of top and combined blowing of the BOF bath by application regular, two-circuit and double-flow oxygen lances. A methodology of test heats carrying out presented, which ensured obtaining important practical information on forming and variation of dimensions of the reaction zone. In particular, information was obtained about the interaction of ultrasonic and sonic oxygen jets with the metal melt, development of afterburning, emission out of reaction zone C to CO2 in the subsonic and sonic oxygen jets with forming high temperature flares directed on the BOF bath surface or penetrated in the foamed slag, emissions of slag-metal suspension out the BOF, forming of metal-slag sculls on the lance tube during the blowing with various level of foamed slag-metal emulsion.

To the Use of Thermal Imagers in Solving the Topical Problems of Thermal Physics at a Metallurgical Enterprise

This paper formulates and substantiates the list of topical problems of thermal physics in relation to hazardous production facilities that constantly arise and require prompt solutions at a metallurgical enterprise. Many problems can be successfully solved using optoelectronic equipment, such as a thermal imager. Thermal imager allows to scan the entire object completely without contact. Topical tasks that can be solved with the help of a thermal imager: monitoring and evaluation of the probability of trouble-free operation of the steel ladle lining during its heating, wear resistance of the converter during oxygen purging of the metal melt, spills of the metal melt from the converter, damage of the exit edges of the nozzles of gas-air burners, determination of the surface temperature of the walls of various furnaces, etc. In the converter, electric steel-making and other workshops, with the help of a measuring thermal imager or pyrometer, it is possible to monitor heat leaks from the production premises, to obtain the distribution of the local heat transfer coefficient on various parts of the thermal surface. It is also possible to predict the temperature condition in emergency situations, confirm the requirements for the thermal mode of the operated object, identify and control ingots and billets with regard to their grain size and uniformity in the ingot cross-section, etc. Paper presents the examples of thermograms obtained both for the steel ladle and for other objects. Formulated list and experimentally confirmed solutions of thermal problems clearly show that with the help of a thermal imager it is possible to quickly, efficiently, and reliably solve the complex problems of heat exchange and heat transfer in the subdivisions of a metallurgical enterprise.

Influence of dispersed particles of tungsten carbide on the microstructure of 12Kh18N10T steel obtained by centrifugal casting

The development of new technologies in various industries, such as fast neuron reactors, require a new level of operational properties from steels and raise the issues of resistance to neutron radiation, radiation swelling, embrittlement and creep, and the level of residual activation. The principal way to increase these properties is to adjust the chemical composition, and rearrange the crystal structure of the metal. The authors propose to achieve this by introducing finely dispersed particles into the melt and controlled by them to “reinforce” the crystal lattice, grinding the metal structure. During the work, using the FactSage software package, thermodynamic modeling of the interaction of dispersed particles with a 18Х18Н10T steel melt was carried out, showing that the particles will interact with the metal melt, which can lead to their complete dissociation, and at the next stage of crystallization, regardless of the degree of dissolution of tungsten carbide, the formation of carbide phases based on titanium carbide with an FSS structure, as well as a carbide phase based on chromium carbide with the formula M23C3, will become. According to the simulation parameters, experiments were conducted, experimental blanks with different contents of the introduced tungsten carbide were obtained, and heat treatment was carried out. The study of microstructures showed that the introduced particles of tungsten carbide completely dissociate when interacting with a metal melt and contribute to an increase in ferrite in the microstructure of the workpiece. Studies of microhardness confi rmed the significant effect of the introduced carbide on the properties of the material: the maximum values of microhardness are achieved at a high concentration of refractory particles in the areas of their maximum concentration (outer edge of the workpieces). Carrying out heat treatment reduces microhardness, while aligning the gradient of properties with the volume of castings. This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation within the framework of the federal target program under Agreement No. 075-15-2019-1711 (internal number 05.608.21.0276) dated December 04, 2019 (unique project identifier RFMEFI60819X0276).