High Slag Research Articles

Viscosity Determination of High Oxidizability Refining Slag and Its Buildup Solution

The principal purpose of this paper are to determine the viscosity of refining slag with the features of high crystallinity and strongly oxidizability, and to solve the problem that slag sticked onto the RH immersion tube during the RH refining process. Then, the fluid length method was used to determine the viscosity, and the effect of compositions on melting point and viscosity of refining ladle slag was studied. Overall, the relationship between viscosity and fluid length was acquired, and it achieved the slag with lower melting point and good fluidity which can avoid slag building-up on RH immersion tube by adjusting the basicity of refining slag to 4-5, the content of Al2O3 to 14-15% with additives.

High Intensity Glassed-Block Was Prepared by Fluid Cinder

High temperature fluid slag was used as main material, and high intensity glassed-block was prepared though internal latent heat. The influence of prepared process conditions on products characteristic was inspected, and the reaction phenomena were rationally explained. The rational process conditions were finally available, fluid cinder glassed-block was obtained, and it has such excellence as: high hardness and intensity, low water absorption, good acid fastness and alkali tolerance.

Mineralogy and Initial Chlorination of Water Granulated High Titania Slag

Water granulation of high titania slag causes oxidation of some of the trivalent titanium in the slag to the tetravalent form; in smaller granules, some iron is also oxidized to ferric. Oxidation changes the phase constitution of the slag, with more rutile present (containing some iron oxide in solution). The chlorination rate (in a mixture of nitrogen, chlorine and carbon monoxide at 980 °C in a fluidized bed reactor) is similar for the granulated and conventionally-produced (block-route) slags, except in the case of the smaller, more oxidized granules, where chlorination of the ferric-containing phase is slower. The temperature increase during chlorination (exothermicity) is smaller for the granulated slags, in line with prior oxidation of trivalent titanium to the tetravalent form during granulation.

Mineralogy and Initial Chlorination of Water Granulated High Titania Slag

Mineralogy and Initial Chlorination of Water Granulated High Titania Slag

Influence of operational parameters on silicon in hot metal from Corex

Quality steel production at low cost demands superior quality of hot metal (HM) with low silicon (Si) and sulphur. High silicon is undesirable for its subsequent treatment during steelmaking, making the process costlier and less productive, hence there have been constant efforts to lower the silicon content in HM. Corex is the only commercially established and proven smelting reduction ironmaking technology alterative to conventional blast furnace (BF) ironmaking. While the mechanism of silicon transfer is largely understood in the BF, the Corex process still requires further operational guidance for its control. A statistical analysis of more than one year plant data has been carried out to understand the parameters influencing the silicon content and to provide directions for its prediction and control. Based on the understanding of the parameters affecting the silicon in HM, regression analysis was carried out and equations have been developed to predict the silicon in Corex HM. The present paper discusses the various parameters involved, the regression output for silicon prediction, its validation and its interrelation with operating parameters. The analysis indicates that high fuel rates due to high moisture, poor metallisation, high volatile matter, high slag volume, high coal fines and low production, along with high basicity and alumina in slag lead to high silicon in HM.

Heating and melting mechanism of stainless steelmaking dust pellet in liquid slag

The heating and melting mechanisms of the pellets immersed in liquid slag were investigated, and the effect of the pellet heating and the melting conditions were studied. The results show that the dust component in the pellet is melted from the surface and no metallic elements are melted before the dust component, the time for the pellet completely melted is reduced as the iron powder content increases since the metallic iron has high thermal conductivity. These are four stages of heating and melting of pellet in liquid slag, they are the growth and melt of solid slag shell, penetration of liquid slag, dissolving of dust component and melting of reduced metals. The lifetime of the solid slag shell is in the range of 7–16 s and increasing the pre-heating temperature of the pellet and the slag temperature can shorten the slag shell lifetime. The time for the dust component in the pellet to be melted completely is in the range of 20–45 s and increasing the pre-heating temperature, especially in the range of 600–800 °C, can obviously reduce the melting time. A higher slag temperature can also improve the pellet melting and the melting time is reduced by 10–15 s when the slag temperature is increased from 1 450 to 1 550 °C. The pellet with higher content of iron powder is beneficial to the melting by improving the heat conductivity.

Influence of Mineral Admixtures on Crack Resistance of High Strength Concrete

As high strength concrete (HSC) is widely used in construction, more and more attention has been paid to crack resistance of it. In order to improve crack resistance of HSC, we study the influence of mineral admixtures (ground slag, silica fume and fly ash) on brittleness and characteristic length as crack resistance’ indexes. Testing researches shows, without admixture, crack resistance of HSC is the lowest; when one of the three mineral admixtures added, crack resistance increases dramatically; when two of the three mineral admixtures are added in the concrete, crack resistance increases a little more and it does not change very much no matter which two are mixed; crack resistance comes out the highest when the three mineral admixtures are added in concrete. Mechanism analysis shows, Adding fine and high active ground slag, silica fume and fly ash into concrete can greatly improve microstructure of transition zone, decrease Ca(OH)2, ettringite and porosity in concrete, increase C-S-H gel and greatly reduce the original micro-cracks in the transition zone.

Aluminium Recycling and Environmental Issues of Salt Slag Treatment

Environmental friendly recycling is the trend toward total recycling of aluminium metal. In the secondary aluminium industry, due to the complexity of compositions and contaminants in the various types of aluminium scraps, an understanding of the behavior of different scraps during melting is crucial in the recycling process. Salt slags are the byproducts of the secondary aluminium industry, which should be recycled and processed in a proper way by taking the environmental impact into consideration. This article provides qualitative assessment on 10 different commercial aluminium scraps for their relative recyclability via well-designed and controlled laboratory experiments. It confirms that more nonmetallic contaminants, smaller size, and higher ratio of surface area to body volume generally lead to a lower metal recovery. Recycling the scraps with lower recyclability normally generates more salt slags. High slag viscosity leads to more fine aluminum metal entrapped in the salt slag and thus increases the load of salt slag recycling. It was found that viscosity of the salt flux is increased with the amount of entrapped nonmetallic components, which affect the settling of heavier materials. In addition, the slag samples from the melting tests were leached and analyzed to evaluate the behavior of carbon containing scrap. The elevated carbon content in the scrap resulted in more carbide formation in salt slags and thus more methane generation in salt slag recycling with a higher environmental impact.

Factors affecting nickel recovery from slags produced during platinum smelting

Nickel is recovered as a by-product of the platinum-producing process operated by Anglo Platinum. The metal is mined mainly as sulphide minerals contained in platinum ores. These pass through the concentrating, smelting and converting process route and nickel is finally recovered by electrowinning. Smelting of the concentrated ore in the electric furnace produces a melt with a high slag to matte ratio. The resulting furnace slag is granulated and later milled and floated to recover matte. A project was initiated to investigate the distribution of nickel in the slag in order to improve recovery. Slag samples were examined using a combination of chemical and mineralogical techniques. The granulated slag was found to consist mainly of a silicate glass phase, which reflects the composition of the molten slag in the furnace. Nickel occurs as free matte granules, as matte phases locked inside the glass, and in the glass phase itself. Whereas nickel in the matte is as sulphide, most of the nickel in the glass phase appears to be oxide-bound (i.e. in solid solution). Milled slag as flotation feed showed recovery-limiting features such as free matte with oxidised surfaces and unliberated matte inclusions in the slag. The biggest nickel losses, assuming no tapping problems, are in the glass phase solid solution. Only around 40% of nickel would be recovered from the slag, even under ideal conditions. Spoon and pot slag samples were also examined to see if casting and crushing would improve recovery. Although larger and, therefore, more easily recovered matte phases formed, nickel partitioned into crystalline silicate phases, limiting the maximum theoretical nickel recovery to 70%.

Effect of FeO in Dripping Slag on Drainage Ability of Slag

Japanese iron and steelmaking industry has to reduce CO2 emission by 11.5% in 2010 relative to the level of emissions in 1990. Stable blast furnace operation is required to reduce energy consumption and CO2 emission in iron and steelmaking industry. For the stable blast furnace operation, precise controlled drainage is one of the important factors. However, there are many unrevealed phenomena in the hearth to perform the stable operation. Therefore, in this work, the effect of iron and slag dripping pattern, FeO concentration in the dripping slag on the iron and slag surfaces, thermal properties of refractory and brick on drainage temperature, temperature distribution in the hearth, temporal variation of iron and slag drainage rates and interfaces shapes were investigated by using tree-dimensional mathematical model.The results indicate that more than 2 mass% FeO in dripping slag will cause deterioration of slag drainage ability due to high slag viscosity around tapholes. Continuous monitoring of FeO concentration in the tapping slag is effective to prevent deterioration of slag drainage ability. The trends of the other side of tapping taphole temperature were varied dramatically according with FeO concentration in the dripping slag. Even in the case of 0 mass% FeO in the dripping slag, there is a solidified slag near the hearth wall except around the tapholes. A peripheral distribution pattern will result in a stable drainage. Slag, which dripped on near the other side of the tapping taphole, stays around the taphole, and does not drain from the tapping taphole located opposite side.

Silicomanganese production from manganese rich slag

Manganese rich slag produced by the appropriate treatment of high manganese pig iron has a high manganese content and results in low fines, is low cost and gives low excess oxygen. Manganese recovery from this slag in the form of manganese ferroalloys compensates for the excess cost of the treatment process. Manganese rich slags produced from the injection of high manganese pig iron under at optimum conditions have levels of (Mn)>35 wt-%, (Mn)/(Fe)>7.65, (Mn)/(Si)>2 and (Mn)/(P)>285, which satisfy requirements for use as raw material in silicomanganese alloy production. Various experiments were carried out to smelt high manganese slag resulting from the treatment of high manganese pig iron to produce silicomanganese in a bench scale submerged electric arc furnace. Use of such manganese rich slag in the proportion of 40% of the blend has been found to be optimum to obtain a silicomanganese alloy with the highest metallic yield and highest manganese recovery. The silicomanganese alloy produced satisfies the standard chemical specifications, with manganese and silicon contents 68 and 18%, respectively.

Demanganisation of high manganese pig iron to produce high manganese slag

Pig iron with a high manganese content makes further processing to steel using converter technology difficult and unprofitable. In the present study, external demanganisation of high manganese pig iron before the oxygen converter process has been investigated. Pilot plant experimental heats were designed and carried out to optimise the demanganisation process, to produce hot metal adequate for the conventional LD converter, and high manganese slag suitable for the production of silicomanganese. Various high manganese pig irons with different [Si]/[Mn] contents were treated by injection of various oxidisers at varying temperatures, slag basicities and injection rates. The optimum conditions for the demanganisation process have been attained by injection of an oxygen gas–manganese ore mixture at the injection rate of 6.8 L min-1kg-1 into molten high manganese pig iron with a [Si]/[Mn] ratio of 0.3 at an initial temperature of 1350°C and slag basicity of 0.3–0.4.

Use of Ground Granulated Blast Furnace Slag for Reduction of Expansion Due to Delayed Ettringite Formation

Abstract Two cements, with a demonstrated tendency in mortars to suffer expansion related to delayed ettringite formation when cured at high temperatures ≥75°C, were tested after substitution of 5, 17.5, and 30 % with a ASTM C 989 Grade 100 ground granulated blast furnace slag. The two cements are here characterized as a “highly expansive” and a “moderately expansive” portland cement, according to the tendency of each to expand when stored in limewater after curing at elevated temperatures >75°C. Expansion was reduced or delayed, but not eliminated, with 5 % slag substitution, but completely absent when 17.5 % slag substitution was used. Compressive strengths were measured on cubes cured at ambient temperatures and at 90°C. Test results indicated that no strength penalty was experienced in mortars with high slag substitution, cured at 90°C; in fact, the compressive strengths were superior for the 30 % slag mixes, at all ages tested (from 1–28 days of hydration). The conclusion is tentatively reached that the use of blast furnace slag to reduce proclivity to DEF is effective, and does not involve any sacrifice in mortar compressive strength, at least to 28 days of hydration.

The permeability and strength of green high performance concrete

The permeability, alkali-silica reaction, workability and strength of GHPC (green high performance concrete) were studied in this paper. The results show that GHPC has an excellent durability and the effects of mass ratio of flyash to high calcium slag, water-binder ratio, content of water reducer, and crushed coarse aggregate type on the workability and strength of GHPC were considerably evident. A new path for the concretes continuous development was put forward.

Thermal Shock Resistance of a Special Mullite Based Refractory for Molten Metal Handling Application

Mullite is a strong material for advanced structural and functional applications owing to its low thermal expansion, low thermal conductivity, excellent creep resistance, good chemical stability and high temperature resistance. The material occurs very rarely in nature and hence synthetic mullite is a promising candidate for most of the advanced refractory applications.The main requirement of the product is high thermal shock resistance and high temperature slag resistance in presence of molten metal. A typical range of porosity and sufficiently high strength are the parameters required to achieve the above properties.In this work, a special mullite composition has been developed and characterized by measuring density, porosity, thermal expansion, modulus of rupture and modulus of elasticity. A quench test in conjunction with strength measurement has been done on uniaxially pressed test pieces to check the thermal shock resistance of the material which is a prime requirement of the material for its use in molten metal applications. It has been observed that the thermal shock resistance of the material is excellent as analyzed from the strength data after each quench. The paper analyzes these data in conjunction with other mechanical properties such as bend strength and modulus of elasticity.

Cathodoluminescence (CL) Microscopy Application to Refractories and Slags

Refractories are ceramic materials possessing high thermal shock properties and slag corrosion resistance, as well as creep resistance at high temperatures. They are used in large quantities in steel making furnaces, metal smelting vessels, and glass melting tanks, and are made from very refractory minerals such as lime, periclase, corundum, spinel, and zirconia. Slags are residual vitreous materials generated during steel refining processes. They cover a wide range of compositions and may contain pure oxides, silicates, and sulfides as well as fluoride phases, depending on the melting and smelting processes. These minerals exhibit spectacular cathodoluminescence color when bombarded with electrons. Cathodoluminescence (CL) microscopy, therefore, is a very effective technique for the characterization of refractory corrosion by slags. Studies in this paper include: (1) reaction of fluorine containing mold slags with ZrO2-C nozzle refractories, promoting crystallization of cuspidine [Ca4Si2O7(F,OH)2], (2) corrosion of fusion cast refractories and formation of glass defects in TV panel glassmaking furnaces, and (3) densification of spinel-based castable in steel melting induction furnace.

The Relationship Between Microstructure and Mechanical Properties of Late 19th/Early 20th Century Wrought Iron Using the Generalized Method of Cells Model

ABSTRACTThe discovery of the RMS Titanic has led to a number of scientific studies, one of which addresses the role that the structural materials played in the sinking of the ship. Chemical, microstructural, and mechanical analysis of the hull steel suggests that it was state-of-the-art for 1912 with adequate fracture toughness for the application. However, the quality of the wrought iron rivets may have been an important factor in the opening of the steel plates during flooding. Preliminary studies of Titanic wrought iron rivets revealed an orthotropic, inhomogeneous composite material composed of glassy iron silicate (slag) particles embedded in a ferrite matrix. To date, very little is understood about the properties of wrought iron from that period. Therefore, in order to assess the quality of the Titanic material, contemporary wrought iron was obtained from additional late 19th/early 20th century buildings, bridges, and ships for comparison. Image analysis completed on the Titanic wrought iron microstructure showed a high slag content that is very coarse and unevenly distributed. To investigate how microstructure impacts the mechanical properties, and hence the quality of late 19th/early 20th century wrought iron, a detailed analysis of the relationship between the microstructural features and the mechanical behavior was completed. Here we present the first step in that process: the use of the Generalized Method of Cells (GMC) to predict the mechanical response of composites with variable microstructural properties. The GMC tool is used to generate the effective inelastic behavior of the composite from the individual constituent properties.

Albemarle Iron Works (1771–1772): Why did this operation fail?

In December of 1770 the Albemarle Iron Works, Albemarle County, Virginia, USA was formed to build a cold blast furnace for producing cast iron. This furnace was put into operation in September of 1771 but was closed permanently in June of 1772; no usable iron was ever produced. The reason for this failure is not clear, but it has been suggested that the cause was the use titaniferous iron ore. The presence of high Ti would result in a very high viscosity slag, which in turn would not allow for the separation of the iron from the slag and, thereby, slow down the operation of the furnace. Slag, recently taken from the site, has been analyzed by both PIXE and SEM, and the results confirm the high Ti content. Another indication that the furnace was having difficulties was that the slag was not typical glassy slag. Furthermore the iron prills entrapped in the slag showed a high phosphorus content which would result in an iron too brittle for practical use.

Rheo-Engineering Properties of Mixed SiO2/Al2O3 Suspensions and Related Materials. III. The Fused Quartz – Fused Corundum System

A corundum suspension at pH = 7 with a 58% volume concentration of the solid phase and a molding porosity of 20% is prepared. The properties of fused quartz + fused corundum mixed suspensions are studied. Based on a mixed binder of composition 50% SiO2 + 50% Al2O3 and a fused quartz filler, a castable is prepared which, heat treated at 1150°C, exhibited the following properties: open porosity — 13%, compressive — 80 MPa, temperature for strain onset under loading — 1250°C, thermal stability — 10 heat-cool cycles (1000°C – water). The new castable exhibits a higher slag resistance against the conventional quartz-based castable.

Production of high quality sinter for blast furnace burdens aiming the high pulverized coal rate operation

In order to achieve high rate pulverized coal injection into the blast furnace, it is important to keep the permeability of the lower part of the blast furnace. The reducibility and high temperature melting behaviour of the sinter must be improved. From this point of view, NKK has studied high reducibility sinter by decreasing SiO2 content. The behaviour of the sinter has been investigated under high rate pulverized coal injecting conditions. By using low SiO2 sinter with high RI value and low slag content, the Fukuyama No. 4 blast furnace can now achieve stable operation during high rate pulverized coal injection.