Features of GSTM1, GSTT1 and GSTP1 Genetic Polymorphism in Nizhny Tagil Metallurgical Plant Workers with Cardiovascular Diseases

Background: The development of cardiovascular diseases is determined not only by working conditions but also by genetic characteristics of employees. Genetic GSTM1, GSTT1 and GSTP1 variations contribute to individual differences in responses to industrial chemicals and carcinogens. Objective: To study the features of the genetic polymorphism of the GSTM1, GSTT1, and GSTP1 genes in metallurgical plant workers with diseases of the cardiovascular system in the town of Nizhny Tagil, Sverdlovsk Region, Russian Federation. Materials and methods: The case cohort included 61 men aged 33 to 61 years (mean: 48.15 ± 7.50 years), working in the converter shop and suffering from heart diseases. The control cohort consisted of 29 conditionally healthy male employees, aged 23–56, of the same iron and steel works having no signs of a cardiovascular disease. The DNA was isolated from peripheral blood using a standard technique. Deletion polymorphism of GSTM1 and GSTT1 genes was determined by quantitative PCR; Ile105Val polymorphism of the GSTP1 gene was established by qPCR using a commercial test kit. Results: We observed no statistically significant differences between the cohorts for any of the studied genes. The frequency of occurrence of the combination of GSTM1 (0/0) and GSTT1 (0/0) in the cases and controls was 14 % and 11 %, respectively, but the difference was negligible. Conclusions: Our findings demonstrate that the presence of null genotypes of GSTM1, GSTT1, as well as the mutant GSTP1 allele and the associated loss of enzyme activity contribute little to the development of cardiovascular diseases in workers exposed to occupational hazards.

Hydrogen removal in circulating vacuum degasser under conditions of PJSC “NLMK”

For high­quality steel smelting, stage­by­stage production is required, which has a complex of metallurgical units capable for producing products with high performance properties and low content of harmful impurities. One of the harmful impurities is hydrogen, so it is important to limit its content in the metal. To ensure the specifed hydrogen content, the metal in the steel out­of­furnace treatment at Converter Shop No. 2 (CS­2) of PJSC “Novolipetsk Metallurgical Plant” (“NLMK”) is subjected to vacuum treatment in a circulating vacuum degasser. Despite the prevalence of circulating vacuum derassers, theoretically, mechanism of hydrogen removal in these metallurgical units has been insufciently studied. To increase efciency of hydrogen removal, theoretical calculations were performed to remove it from the metal. There are several mechanisms for hydrogen removing: direct transfer of hydrogen from metal to the surrounding space; formation of gas bubbles in metal and their direct ascent; nucleation of hydrogen bubbles at the border of refractory wall and metal; removal of hydrogen by metal blowing with neutral gas (argon). It is shown that the main ways of hydrogen removal in a circulating vacuum degasser are direct transfer of hydrogen from metal to the surrounding space and blowing of melt with transporting gas. In the CS­2 of PJSC “NLMK”, both ways are implemented at a circulating vacuum degasser. Vacuum pumps provide pressure in a vacuum chamber of less than 101.3 Pa (0.001 atm.). It promotes intensive removal of hydrogen from the metal surface. To ensure circulation of metal, transporting gas argon is supplied to the inlet pipe of the RH degasser, which also takes part in removal of dissolved gases by transferring hydrogen to neutral gas bubbles. Additionally, performed calculations have shown that the main way of degassing in conditions of CS­2 of PJSC “NLMK” is removal of hydrogen into the bubbles of carrier gas.

Application of the shotcreting method to restore the working layer of the lining of steel-pouring ladles of the oxygen-converter shop of PJSC MMK

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Development of Supplements Prevention System in Oxygen Converter Process in Order to Increase the Economic Efficiency of Steel Melting

The article analyzes the work of the oxygen-converter shop of PJSC «ArcelorMittal Kryvyi Rih». It is shown that almost half of the total number of blowing supplements (~ 44%) is carried out by temperature. In order to improve the conditions of steel smelting and reduce resource costs, calculations were performed and new technological solutions were found in steel smelting to reduce the number of additives. The study of real smelters demonstrated the need for corrective operations in the smelting of steel using scrap metal of different types. Scrap smelts have a clear relationship between the amount of scrap in the charge and the temperature of the melt in the first dump. The addition of «goat» scrap to the charge has a number of uncontrolled effects on the process due to significant fluctuations in the chemical composition of this type of metal charge. An economic analysis with introducing the developed control mechanism over the course of steel smelting into the software system for conditions PSJC «ArcelorMittal Kryvyi Rih» was performed.

Development of welded structure of 5-nozzle lance heads in converter shop of PJSC “Dneprovsky metallurgical combine”

For the upper blasting lances of 250-tons oxygen converters at PJSC «DMС» (Kamenskoe, Ukraine) the author has proposed a number of welded structures of 5-nozzle lance heads with increased resistance. A set of industrial studies of their operation made it possible to establish that the devices which provide cooling of the areas back from the nozzle zone of the tip have the highest resistance. Measures to increase the values of the average cooler speeds in welded structures of the lance heads and their rigidity also turned out to be quite effective. The transfer of copper welds holding the nozzle inserts in the copper tip from its outer surface to the inner proved to be ineffective from the point of increasing resistance of the lance head (the average resistance of the heads increased by only 7 heats – from 78 to 85 heats). This allows us to assert the need for complete elimination of copper welds in the head (both external, exposed to high-temperature and mechanical stresses, and internal) that hold nozzle inserts in the holes of the welded tip and lance head collector. Thus, in spite of all the measures taken to transfer the welds from the outer surface of the tip to its inner surface, to improve cooling of the tip and its back from the nozzle zones, which also include sections of copper welds around the nozzles, as well as to increase the rigidity of the blast welded structure heads, this led, although to positive, but still to relatively low results. The data obtained indicate that welds made of copper around the nozzle inserts, which are held by this in the tip (also in the collector) of the head, are the limiting link that does not significantly increase the resistance of welded lance heads, and it is urgently necessary to back off its use.

Smelting of steel semi-product in BOF and EAF under magnesian slags

Basics for the development of a rational composition of the main magnesian slags and technological methods for their formation according to the periods of BOF bath blowing and the periods of smelting in EAF are the results of fundamental studies of the slags physicochemical properties. Implementation in the converter shop of OJSC “EVRAZ NTMK” of a developed set of technological methods of magnesian slags formation in the main period of blowing and a wearresistant skull on the basis of magnesian final slags ensured record durability of converter linings. These slags have low aggressive effect on the lining of converters, while maintaining high refining properties. The durability of the converters’ lining exceeds 7000 heats, while maintaining high technological and technical-economic indicators of the process. During heats of low manganese cast irons in 350-metric ton heavy converters of JSC “EVRAZ ZSMK” under magnesian slags, the features of slag formation and changes in chemical composition of the slag were studied by the periods of the BOF bath blowing. During the process stage of phosphorous cast irons in 300-metric ton BOF at JSC “ArcelorMittal Temirtau”, a set of technological methods was developed for the formation of magnesian slags of the recommended chemical composition by the periods of phosphorus cast irons blowing and wear-resistant skulls based on final magnesian slags of moderate basicity. The implementation of the developed technological methods ensured the lining stability of BOF of more than 5 000 heats while maintaining high technological, technical and economic indicators of phosphorous process stage. In the EAF shop of PJSC “Seversky Pipe Plant” a technology for the formation of magnesian slags of rational composition was developed over the smelting periods in EAF-135. Introduction of the technology ensured the record resistance of the refractory lining of the furnace up to 1900 heats per campaign and high level of technological and technical-economic indicators of the process.

Smyslova Simulation modeling of logistic system for liquid iron transportation at metallurgical plant

During the study of technological data of the process of liquid iron transportation, it was found that the number of locomotives and mixers depending on the duration of operations and especially on the inter-operational downtime does not always ensure normal rhythm of the main production. It leads to significant production losses, therefore, the work of the producing and transport complex is not effective enough. The authors have developed a simulation model of a logistics system for transporting liquid iron at a metallurgical plant. The study and construction of the model was performed using AnyLogic. Real data from production, namely the schedule of blast furnace smelting for a three-week period, was used as the initial data. To prove adequacy of the model, the results were compared with the actual tact of the mixers movement, as well as with the theoretical need of the converter shop. Values of the liquid iron weight delivered to the converter shop were obtained during the simulation and were related to the theoretical ones. Efficiency of the model is achieved by automatically collecting in real time of statistical values of the parameters of simulation objects. The system analyzes the collected data and makes decisions based on them for a short period of time (less than one second). In default operation mode of the simulation model, motion of the mixers is controlled automatically without participation of the dispatcher, which improves efficiency, as well as decision-making speed. Such model provides simulation of failures in operation of the converter shop. According to the simulation results, it can be concluded that the system delivers less liquid iron to a converter shop, but retains its rhythm. After resuming the operation of all converters, the tact of transportation reaches the required level.