In the hydrometallurgical processing of vanadium slags and the recovery of vanadium pentoxide from the slag, the main phase of the slags -the spinellide -is the phase of the greatest interest from a commercial standpoint.Experience shows that the amount of spinellide which is present varies widely from one heat to the next -from 43 to 78%. This index affects not only the composition of the pig iron being made, but also the specifications of the chosen oxidant, the composition of the additions, the temperature of the pig, and other characteristics.To establish the relationship between the chemical composition of the converter slag and the concentration of spinellide, we statistically analyzed the results from a chemical analysis of a large number of slags. We analyzed about 30 railcars of converter slag that arrived at the shop over a period of 2-2.5 months. Chemical composition was determined by sampling the slag in accordance with the method adopted at the plant: crushing, followed by separation of metallic iron in the form of inclusions, scrap, and dispersed iron. To perform a petrographic analysis, five small samples of slag up to 80 mm in size were taken from each railcar load during the crushing operation. The results of the analysis were then averaged.The slags were divided into three groups based on the concentration of spinellide: nominally, 50%, 60%, and 70%; the actual concentrations were 51.3, 59.99, and 69.7%. The ranges of spinellide concentration in the different groups were 43.4-56.1, 57.2--62.0, and 65.1-78.8%, respectively. The chemical composition of the slags in each group was averaged over 10, 12, and 8 tests (Table 1).It can be seen from the table that metallic inclusions have the greatest effect on the concentration of spinellide. The mechanism of this effect is still unclear, but it can be stated that converter slag which contains no more than 19% metallic inclusions will have a spinellide content in the range 65-75%. A relationship was found to exist between spinellide content and the content of vanadium oxides, but it was not as explicit as had been expected. No relationship was found between spinellide content and the other components of the slag.The presence of spinellide in the slag is not by itself sufficient to be able to fully extract the vanadium in the slag during hydrochemical treatment. An equally important factor is the size of the spinellide grains that are formed. According to process specifications, the optimum grain size is within the range 10-15 Bm. Under production conditions, up to 60-70% of the total mass of spinellides consists of grains of 2.5-5.0 Bin. We assumed that spinellide grains were formed not only during the formation of the slag in the converter, but also during its cooling in air after tapping. To confirm this, we conducted an experiment to establish the effect of cooling time on the granulometric composition of the spinellides in converter slag; vanadium slag from recent commercial heats was used in the experiment. After being discharged from the furnace, ...
The constantly increasing need for quality ferroalloys requires an improvement in existing production processes and the use of progressive technologies. This problem is being given serious attention at the Chusovoi Metallurgical Plant. Its ferroalloys shop, which has been in existence since 1936, had ceased to satisfy the country's needs for ferroalloys. Thus, following a decision by the national government, the plant began the construction of ferroalloys shop No. 2 at the beginning of the 1960s. The shop was designed by the institute "Giprostal'" (in Kharkov). The technology and equipment were chosen with allowance for the experience gained in the operation of shop No. 1 and the most progessive designs used by similar concerns in Russia and by foreign vanadium producers, such as Otanmyaki (Finland) and the plant in Vitkovitz, Czechoslovakia. The initial data that was used consisted of information from researchers at the Chusovoi plant, scientists at the Central Scientific Research Institute of Ferrous Metallurgy (TsNIIchermet), Ural Polytechnic Institute (in Sverdlovsk), and other organizations.The plan devised for the shop included the following elements, which were intended to improve the production process: 9 crushing of slag to a fineness of less than 100 mesh, making it possible to more completely expose the grains of iron-vanadium spinelide; 9 air separation of the charge, making it possible to increase the recovery of vanadium; 9 the installation of equipment providing for complete and uniform mixing of the charge materials before roasting, in order to stabilize the composition of the charge; 9 the installation of a line to process metal screenings, including separation of the slag portion, in order to further increase the recovery of vanadium; 9 the use of rotary drum-type roasting furnaces with a length of 42 m and a special expanded part to increase the degree of conversion of vanadium to soluble forms; 9 the use of active acid leaching, with complete recycling of all intermediate solutions, in order to more fully recover vanadium in solution and reduce the consumption of sulfuric acid and soda; 9 secondary precipitation of vanadium from waste water, to increase vanadium recovery while rendering the water harmless; 9 the use of hydrochloric acid in a precipitation technology that yields high-purity vanadium pentoxide; 9 comprehensive automation of production processes; 9 installation of gas-cleaning and aspiration systems. Ferroalloys shop No. 2 began operation on July 1, 1964. Since the shop had to reach its design capacity as quickly as possible, some errors were made in substantiating certain stages of its initial operation. The attendant problems hurt the performance indices of the shop. However, the changes that were made to its plan of operation were necessitated mainly due to mistakes made by the designers, due to their lack of experience in designing such facilities and their lack of familiarity with the relatively sophisticated equipment that was to be used. As a result, a mechanical system wa...
A new class of progressive steels, called low-hardenability (LH) steels, has been developed and come into broad industrial use in Russia. These steels are intended for use in a new method of strengthening important heavily loaded machine parts -bulk-surface quenching (BSQ).The fact that a lower hardenability is obtained in making these steels compared to structural carbon steels makes it possible to use their rapid quenching by fast-moving water to obtain a high-strength (HRC 60), ultrafine-grained surface layer and a strengthened core in the cross section of parts being given the strengthening treatment. For many heavily loaded machine parts, having such a cross section makes it possible to attain record high strength properties and a more durable, more reliable part.Several automobile and tractor plants are successfully using LH steels as a replacement for alloy steels that must be subjected to length, labor-intensive treatment when used for such parts as pinions, spiders in universal joints, and heavy-duty shafts.The metallurgical industry of the USSR produced 130,000 tons of steels of this type in 1990. In the machine-building sector, the trend was toward increasingly broader application of LH steels. However, there was no accompanying expansion of the range of LH steels produced, due to the sharp decline in machine production.The Chusovoi Metallurgical Plant, supported by the Kama River Automobile Factory (KAMAZ), has implemented an important and timely program to further the production and commercial use of LH steels.Although three grades of steel of this class (58-55PP, 47GT, and ShKh4) have already been incorporated into the existing GOSTs, only recently has the full potential of these materials begun to be realized in industry.The use of LH steels for heavily loaded machine parts is efficient from technical and economic standpoints due to the following factors, which do not entail material expenditures by industry.The need to reduce the hardenability of the steel for the BSQ process and the limitingly high cooling rate used in this case make it necessary to sharply reduce the concentration of alloying elements in the steel. Table 1 shows some typical compositions of LH steels that were made in the course of introducing the given quenching operation at the Chusovoi plant.The high structural strength and durability of parts made of these steels can be attributed to two factors. First of all, a unique industrial technology for making LH steel was developed. That technology ensures an extremely low probability of austenite grain ~owth during the strengthening heat treatment. For example, the technology for making LH steel that was developed and introduced at the Chusovoi plant makes it possible to obtain a grain size corresponding to 11-12 points in heat-treated parts (the average area of the grains is 60--30 btm2). Conventional steels in the same state have a grain size corresponding to 7-8 points (average area of the grains 500--1000 ~tm 2, i.e., the grains are t0-15 times coarser). The existence of such ...
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