Electric Melting Research Articles

A Review of Swedish Bearing Steel Manufacturing and Quality Assurance of Steel Products

Abstract The Swedish bearing steel industry dates back a century. Already in the early days, Swedish bearing steels were characterized by an exceptionally high quality due to the availability of pure iron ores that made it possible to produce bearing steels by the acid open-hearth processes. Development of the ladle furnace process using inductive stirring made it possible to use the much more flexible and cost effective electric arc melting process. The strive to produce ever better steel products has been strong, driven by increasing demands on final product performance. Developments in steel processing technology, process know-how, and understanding of the complex relationships governing steel cleanliness are worth noting. Methods used have undergone vast improvements in recent times and the development continues. The same situation is valid for the quality assurance methods employed in the manufacturing of steel products.

A Novel Fabrication Method for Poly(propylene)/Clay Nanocomposites by Continuous Processing

AbstractSummary: It is well known that poly(propylene)/clay (PP/clay) nanocomposite forms an exfoliated structure when mixed with maleic anhydride‐functionalized polypropylene (MAPP). This can be easily achieved by melt processing, however, the use of functionalized chemicals like MAPP costs a lot preventing its commercial application. Recently, it was reported that the exfoliated structure of PP/clay nanocomposite could be obtained without using any compatibilizer such as MAPP when exposed to the electric field. They could regulate the degree of dispersion and exfoliation by controlling the amount of clay loading, the strength of electric field, the time exposed to the electric field, etc. However, this was accomplished by applying the electric field on a rheometer for a long time. It will be practically attractive if we produce PP/clay nanocomposites via continuous processing like extrusion. A new design concept is required for this purpose. In this study, we present a novel method to continuously produce PP/clay nanocomposites using the electric melt pipe equipped with a twin‐screw extruder. Rheology, XRD, and SEM measurements confirm the formation of nanocomposites. Thermal‐ and dynamic‐mechanical analysis also shows the enhancement of the properties. Though, in this study, only a partial intercalation was achieved through continuous processing, it shows a possibility to produce nanocomposites by this approach. As this is a physical process that can be adapted to the conventional extrusion, the approach suggested in this study may be extended to other polymer/clay nanocomposite systems as well.Schematic diagram of electric melt pipe equipped with a twin‐screw extruder.magnified imageSchematic diagram of electric melt pipe equipped with a twin‐screw extruder.

CONSULTING EXPERT SYSTEM FOR CORELESS INDUCTION FURNACES CONTROL

This paper treats a consulting expert system, working as “operator adviser” in the last stage of the melt. The expert system is intended for determination of heating electric power and melting time for reaching to needed melt temperature. The system is realized at 10t coreless induction furnace for counter-pressure steel casting. The evaluation of the minimal needed power and current heat losses is performed by multiple-criterion hierarchical structure with six input parameters for appearance and action with slag cover, quantity and type of alloying elements and alloying time. The knowledge base of the expert system is formalized by fuzzy sets methods and the inference engine realizes pessimistic variant of evaluation on purpose to melt overheating prevention, melting time minimization, energy saving, refractory materials and crucible lifetime extension and production quality guaranteeing.

Heat stress evaluation and worker fatigue in a steel plant.

This study assessed fatigue in electric arc melting workers (ER) and continuous casting workers (CC) in a steel plant and evaluated their physiological response to different levels of heat stress. Fifty-five men participated in the study. The ER group (mean, standard deviation [SD]=41.6, 7.4 years) was significantly older than the CC group (34.9, 6.4 years). The wet bulb globe temperature (WBGT) index of the workplace was measured. Workers' subjective fatigue symptoms were investigated by a 30-item constructive questionnaire, and physiological conditions and response time were measured before and after work for 2 consecutive days. WBGT ranged from 25.4 approximately 28.7 degrees C and 30.0 approximately 33.2 degrees C for the CC and ER areas, respectively. After age adjustment the ER group had significantly higher prevalence rates in subjective symptoms and slower response time than the CC group. The response "thirsty" was the highest after work (75 and 60% for the 2 ER interview days, respectively). A high prevalence (over 40%) of "eyes feel strained," "perception of shoulders stiff," or "feel waist pain" also was observed. Average pre- and postwork ER group systolic pressures were 129.1+/-11.4 mmHg (mean+/-SD) and 126.1+/-12.1 mmHg, 132.5+/-11.4 and 130.6+/-11.2 mmHg for the CC group. Continuous heat-strain monitoring data from one ER and one CC worker indicated that average working heart rate and body temperature were well below 150 beats/min and 38 degrees C. Faster response in critical flicker fusion was found after work than before work, but the differences were not statistically significant (p>.05). Response time for the falling bar grasp was faster at the beginning of work, declined with working time, and rebounded at the end of work. Workers exposed to a hot environment are inclined to subjective fatigue, and their fatigue symptoms increase with the heat exposure levels. However, low resting heart rate and systolic pressure are two characteristics for high heat exposure workers.

Eccles Legacy Bridge, Salt Lake City, Utah

This bridge, completed in December 2001, is a single pylon cable-stayed pedestrian overpass on the sloping campus of the University of Utah. It served as a key element in mobility planning for the 2002 Winter Olympics, linking the Olympic Village with major sports venues on the campus. It now links the old 19th century campus with the contemporary main campus. The eastern abutment walls are faced with red sandstone to match the old campus while the western approach has formal stairs and a sweeping plaza to link with the contemporary side. The bridge also has a glass elevator, custom handrails with integrated lighting, and an in-situ electric snow melting system. Details of the bridge design, seismic analysis, and construction and stay stressing are described.

Heat Stress Evaluation and Worker Fatigue in a Steel Plant

This study assessed fatigue in electric arc melting workers (ER) and continuous casting workers (CC) in a steel plant and evaluated their physiological response to different levels of heat stress. Fifty-five men participated in the study. The ER group (mean, standard deviation [SD]=41.6, 7.4 years) was significantly older than the CC group (34.9, 6.4 years). The wet bulb globe temperature (WBGT) index of the workplace was measured. Workers' subjective fatigue symptoms were investigated by a 30-item constructive questionnaire, and physiological conditions and response time were measured before and after work for 2 consecutive days. WBGT ranged from 25.4∼28.7°C and 30.0∼33.2°C for the CC and ER areas, respectively. After age adjustment the ER group had significantly higher prevalence rates in subjective symptoms and slower response time than the CC group. The response “thirsty” was the highest after work (75 and 60% for the 2 ER interview days, respectively). A high prevalence (over 40%) of “eyes feel strained,” “perception of shoulders stiff,” or “feel waist pain” also was observed. Average pre- and postwork ER group systolic pressures were 129.1±11.4 mmHg (mean±SD) and 126.1±12.1 mmHg, 132.5±11.4 and 130.6±11.2 mmHg for the CC group. Continuous heat-strain monitoring data from one ER and one CC worker indicated that average working heart rate and body temperature were well below 150 beats/min and 38°C. Faster response in critical flicker fusion was found after work than before work, but the differences were not statistically significant (p>.05). Response time for the falling bar grasp was faster at the beginning of work, declined with working time, and rebounded at the end of work. Workers exposed to a hot environment are inclined to subjective fatigue, and their fatigue symptoms increase with the heat exposure levels. However, low resting heart rate and systolic pressure are two characteristics for high heat exposure workers.

USING CAST ELECTROSLAG BLANKS INSTEAD OF FORGINGS IN FLANGE PRODUCTION

Ring blanks of flange type are widely used in oil refining and the chemical industry for connecting various pipelines, which are made in accordance with GOST 12820-80 and GOST 12821-80 from steels 20, 09G2S, 10G2, 08Kh18N10T, and so on. These flanges work at high pressures and under severe climatic conditions with sharp temperature swings in the transporting media and therefore they are subject to inspection by the State Mining, Safety and Health Inspectorate. These products are usually made by forging, pressing, and casting by traditional techniques (open melting methods) followed by mechanical treatment. These standard technologies have advantages and shortcomings. The advantages of ones cast by traditional methods (open induction melting, electric arc melting) include highly accurate casting with minimal tolerances for subsequent machining and high metal use factors. Shortcomings of cast blanks are poor quality in the metal and difficulty in obtaining dense blanks, since on melting and pouring the metal, it becomes saturated with gases, nonmetallic inclusions, and harmful impurities; it also has structural and chemical inhomogeneity. For those reasons, casting is hardly ever used to make components performing critical functions. Components made by forging have higher quality metal, although they may inherit defects from cast items. Major defects of that technology are the high cost of the blanks, on account of the numerous intermediate operations (forging castings, cutting them into blanks, piercing the blanks, and finishing), as well as a low metal use factor and the need for expensive forging and rolling equipment. Hot deformation in making flange blanks is thus forced upon one in order to avoid the low quality of casting. A promising way of resolving this problem is to replace forged blanks by high-quality castings with minimal tolerances for subsequent machining. As these components have central through holes, it is best to use a new technology: centrifugal electroslag casting CESC [1]. The essential point is electroslag melting of an electrode in a melting vessel providing for accumulating the liquid metal and slag in appropriate amounts, with subsequent pouring into a rotating mold. The metal may be consumable electrodes of any shape and section. That technique has been used in making flange blanks for important uses. The electrode is melted under a flux, which is a mixture of calcium fluoride, electrocorundum, magnesite, and silica. That flux purifies the liquid metal in the vessel by removing sulfur and phosphorus and preventing environmental action, and also provides considerable fluidity with high cooling rates [2].

Investigation of Discharge Channel Elongation under Thermal Dielectric Breakdown

A mathematical model of the expansion of a discharge channel due to a growing electrothermal instability in a solid dielectric material under constant voltage is considered. The model describes temperature dynamics, electric field strength, discharge density, and melting of the dielectric. The paper reports the results of a numerical investigation of the discharge-channel expansion during the breakdown of ceramic BeO in a point-to-plane electrode configuration.

Dielectric behavior in electric meltingquartz glass irradiated by γray

Dielectric behavior and optical absorption of quartz glasses before and after irradiating were investigated. Experimental results demonstrate that complex dielectric function of quartz glasses is changed by the irradiation. Its magnitude is decreased by the irradiation. In addition, the change in the dielectric function does not relate to the hydroxyl group in quartz glasses. Experiments also show that dielectric function is relating to the color centers in quartz glasses. Contribution of color center to dielectric function is dependent on its sort and amount in quartz glasses. Dielectric constant decreases with increasing the density of color center

Effect of electric arc vitrification of bottom ash on the mobility and fate of metals.

Increasing amounts of municipal solid waste incineration (MSWI) residues are treated prior to landfilling or reuse. In Japan, electric arc melting is used for bottom ash vitrification that generates a glasslike slag. The objective of this paper was to assess this pretreatment technique with respect to its effect on metal mobility and metal content. Both bottom ash and slag were sampled and analyzed on total solids (TS), fixed solids (FS), particle density (pp), specific BET surface area, particle size distribution, and total element content. A six-step wet sequential extraction procedure was used for assessing metal mobility. The results were qualitatively verified by scanning electron microscopy. The major conclusion was that the availability of various metals was affected differently by electric arc vitrification. Metals were solidified, stabilized, and/or separated from the slag. The mobility of Cr, Cu, Zn, Pb, and Ca was reduced. In slag, majorfractions of these elements were found in moderately reducible phases or in the residual slag lattice. The approximately three-fourths of Pb [174 +/- 7 mg (kg of FS)-1] and half of Zn content [676 +/- 352 mg (kg of FS)-1] were most likely removed from bottom ash through evaporation. The total content increases of Al, Cr, Ni, and Cd (51 +/- 3, 621 +/- 27, 138 +/- 19, and 99 +/- 32%, respectively) were probably caused by the wear of furnace refractories.

Current characteristics and microstructure in a multifilamentary Nb-37Ti-22Ta superconductor

The 210-filamentary superconductor based on Nb-37Ti-22Ta, wt.% alloy was obtained by using the electric arc melting and deformation processing. During alloy drawing we used four isochronal intermediate heat treatments at the temperature 425/spl deg/C. The total heat treatment duration was varied from 50 to 1000 hours. The true plastic strain value between heat treatments was 0.4 and after the final treatment was 3-5. The kinetics of phase transformation in the ternary alloy was investigated by the method of transmission electron microscopy. The J/sub c/ value increases with an increasing quantity of the precipitated alpha-phase in medium magnetic fields. The J/sub c/ (5 T, 4.2 K) value reaches 3000 A/mm/sup 2/ or more. In high fields, J/sub c/(10.4 T, 2.05 K) for the given superconductor was equal to 1600 A/mm/sup 2/. The parameters responsible for the shape of pinning force curve are determined for different treatment conditions.

The Effect of Process Parameters on the Stability of Molybdenum Electrodes in Glass-Melting Furnace

An integrated estimate of raw materials, batches, and compositions of container glass is carried out with respect to their efficiency in electric melting. A substantial effect of the redox parameters of the materials and the batch on the glass-melting process and the corrosion of molybdenum electrodes is demonstrated. Recommendations for the improvement of container glass production technology are given.

Ceramic innovations in the 20th century

Ceramic innovations in the 20th century

High temperature oxidation of LaB 6–ZrB 2 eutectic in situ composite

LaB 6–ZrB 2 eutectic in situ composites are interesting candidates for manufacture of turbine blades because of their excellent mechanical properties. The oxidation behavior of LaB 6–ZrB 2 eutectic in situ composites prepared by electric arc melting was studied in a temperature range of 916–1223°C and in a pressure range of 1.5×10 4–7.2×10 4 Pa. The specific weight change of the LaB 6–ZrB 2 eutectic obeys the Arrhenius equation below the oxidation temperature of 1094°C and appears to obeya paralinear equation above this temperature. The rate of weight change is described by k p=9.71×10 −3 exp(−31 000/ RT) mg 2/cm 4 min in the range 916–1094°C. Above 1094°C, rapid oxidation kinetics were observed, La 2O 3·B 2O 3 and La 2O 3·3B 2O 3 being the primary scale constituent with ZrO 2 deficiency in the outer scale. The oxidation increases with P O 2 up to 3.9×10 4 Pa, above which the trend is reversed due to the active oxidation of ZrB 2. The oxidation appears to be controlled by oxygen diffusion through the scale and the oxidized layers consist mainly of La 2O 3·B 2O 3, La 2O 3·3B 2O 3 and trace of ZrO 2.

Use of converter type apparatus for vitrification of salt-saturated solutions of radioactive wastes

Thrce methods may be considered for reprocessing and burial of radioactive wastes with high radionuclide content: storage in tanks, burial in boreholes, and reprocessing into glass followed by stockpiling. Experience has been accumulated within the Mayak Combine on vitrification of wastes on an industrial scale using an electric melting furnace. The listed methods each have their own characteristic features. In our opinion, the most promising method is a one-step procedure. However, the reliability of the apparatus and their low throughput make it difficult to widely use them on an industrial scale. At the Gas Institute (Academy of Sciences of Ukraine), a converter type melting apparatus for reprocessing saltsaturated solutions was developed and studied at the end of the 1960's. A basic feature of this apparatus is that it burns the fuel (gas) directly in the melt, so a specific throughput is achieved which is many times higher than the throughput of tank melting furnaces. These apparatus have been successfully operated within various production processes. Because of the high specific throughput of the apparatus, in 1970 it was decided to conduct experiments on one-step reprocessing of high-level radioactive wastes in the form of solutions with salt concentrations up to 500 g/liter. A remote-controlled TOROS apparatus was developed to carry out the process (TOROS is the Russian acronym for thermal treatment of radioactive wastes by vitrification). In Fig. 1, we show the installatiOn on which the experiments were conducted for developing the TOROS apparatus, and also on which the characteristics of different types of gas-purifying devices were studied. The results of the investigations were then used to design a system to remove aerosols from waste gases for the vitrification electric furnace of the Mayak Industrial Association. Solutions of borosilicate and phosphate composition were used as model solutions. The work was done at the Mayak Industrial Association. The tests were done with a flow rate of 200-350 liters/h of the model solution, containing sodium and aluminum nitrates, phosphoric acid, and also 137Cs (0.01 mCi/liter), 9~ (0.1 mCi/liter), l~ (0.01 mCi/liter). In order to increase the concentration of these elements, the following stable isotopes were introduced into the solution (rag/liter): cesium 200, strontium 100, ruthenium 30-70. Before introduction into the model solution, the radionuclides and stable isotopes were converted to the chemical compounds in which they axe found in industrial solutions: cesium and strontium were converted to nitrates, ruthenium was converted to nitrosonitrates. The specific throughput of the apparatus was 0.8-1 m 3 of solution per square meter of the melt surface per hour. When performing the investigations on the pilot apparatus TOROS-2, data was obtained on the degree of fixation of the elements by the glass as a function of the design features of the melting apparatus, the glass founding technology, the level of the melt, and the conditions for feeding the solution into the melting chamber. It was established that the glass-former materials are taken up by 85-99%, cesium by 82-95%, strontium by 80-97%, ruthenium by 10-70%. The meltings allowed us to work up a design for the converter and the melt discharge unit water, to determine the flow rate for the coolant and the composition of the frit coating for creating a reliable lining, and also to determine the generation conditions and the characteristics of the aerosols formed. The experiments confLrrned the feasibility in principle of reprocessing wastes by vitrification in a converter type apparatus. Based on these data, it was decided to develop an industrial-scale model of the apparatus, TOROS-3k, which was considerably self-contained with longer operating life and allowed for remote control of the process of melting and discharge of the melt and the possibility of replacing the individual design elements (in particular, the torch), and also resulted in reduced entrainment of aerosols.

Slag resistance of refractories in the lining of an arc steel melting furnace

The interaction of refractories of various grades with liquid slags whose samples were taken in different stages of melting from an electric furnace are investigated by wetting for temperatures ranging from 20 to 1550°C. The compositions of the slags differed in the CaO/SiO2 proportion and the content of chromium oxide. It has been established that the olivinite refractory has advantages under the conditions of electric melting, which seems to be explainable by its chemical composition and specific pore structure. The results of the investigation were used to develop compositions of gunite powders for torch guniting of linings of the slag belt of an arc steel melting furnace.

合成マイカの化粧品への応用

Fluormicas have been synthesized by an internal resistance electric melting method. Because of their sizes and stable structures of the crystals those synthetic micas had a potential for cosmetic use. In them, synthetic fluorphlogopite(FPG)has been studied to be the best mica for cosmetics.The fluorphlogopite is chemically pure, and has a excellent lubricity and adhesiveness. The authors established the methods of its synthesis and pulverizing for cosmetic use. UV absorption is the most important item for cosmetics for e.g. protecting sunburn and suntan. The authors newly developed a method to synthesize an iron-rich fluorphlogopite which is more efficient to absorb UV-rays than common fluorphlogopite. It has presently been used in some commercial cosmetics.

Electromelted corundum of Northern Onega bauxites and refractories based on it

Corundum suitable for production of corundum and high-alumina refractories may be obtained by reduction electric melting of Northern Onega bauxites in arc furnaces. The cost of such corundum is 25–30% less than of corundum melted from commercial alumina, and the total energy consumptions taking into consideration the production of alumina are a third. It would be desirable to organize production of large production lots of corundum from bauxites using the existing facilities of the abrasive industry for reduction melting of bauxites in arc furnaces. Development of the melting method, more accurate determination of the scales of use of corundum in refractory production, and organization in the future of production of corundum from bauxites in one of the refractory plants are necessary.

New solutions in lining of domestic electric arc steel melting furnaces

New solutions in lining of domestic electric arc steel melting furnaces

Automated pulling from the melt — an effective method for growing large alkali halide single crystals for optical and scintillation applications

The diameter of single crystals growing from the melt can be monitored directly and periodically using a previously designed electric contact melt level sensor. Automatic control of the melt temperature based on data from these measurements allows one to achieve better diameter stability in the process of the automated growth of large optical and scintillation alkali halide single crystals. Crystals having a diameter of up to 600 mm and a mass over 400 kg have been grown.