Steel Degassing Research Articles

Steel degassing in continuous steel melting units

The requirements for the quality of steel products dictate the need to increase the share of evacuated steel. In addition, the growing cost of fuel, as well as the desire of society and the state to decarbonize various industries, including ferrous metallurgy, requires companies to reduce fuel costs and switch to more modern and cleaner technologies. Reducing the specific fuel consumption, and, accordingly, emissions, is possible due to the transition to continuous production, minimizing the cost of heating the equipment and maintaining the set temperature in the degasser during technological downtime. The article deals with the issues of steel melt degassing in U-type continuous degassers in continuous steel making units. Aim. To consider the influence of rarefaction of a gas bubble on the characteristic size over the melt, speed and time of its surfacing in a U-type degassing unit. Based on the obtained dependences, to determine the characteristic size of a vacuum chamber and energy effect of switching to a continuous vacuumization. Methods.. Results. The authors have determined a bubble characteristic size in a steel melt under vacuum of different degrees. They studied the effect of vacuum on vacuumization speed and the degassing unit dimensions. The energy effect of switching to continuous vacuumization was determined. The proposed methodology is valid for liquid media, the calculations are presented on the example of molten steel. Based on the conducted calculations, the depression influence on molten steel vacuumization was determined. The vacuum chamber dimensions, comparable with RH-vacuum cleaners presented at the market of similar productivity and quality of finished products, as well as reducing energy consumption for steel degassing in a continuous vacuum degasser, compared with the existing circulating installation, were determined.

Research regarding the vacuuming of liquid steel on steel degassing

When the liquid steel comes in contact with the atmosphere of the elaboration aggregates, a process of gas diffusion into the metal bath takes place on the one hand, and on the other hand a process that allows them to pass from the metal bath into the atmosphere. The meaning of these processes is determined by a number of factors as follows: the quality of raw and auxiliary materials (moisture content, oils, etc.), the boiling intensity, the evacuation duration, the properties of used slags, the values of the casting ladle processing parameters (bubbling, vacuuming, etc.). The research was carried out at an electrical steelwork, equipped with an electric arc furnace type EBT (Electric Bottom Tapping) capacity 100t, LF (Ladle-Furnace) and VD (Vacuum Degassing) facilities, establishing some correlations between the vacuuming parameters from the V.D.facility and the amounts of hydrogen and nitrogen removed from the metal bath, as well as their removal efficiency, were taken into consideration. The obtained data was processed in MATLAB calculation program, the established correlations form was presented both in analytical and graphical form. The validity of these correlations was verified in practice, being particularly useful in research.

Prediction of Zinc and Lead Behavior During Steel Electric Smelting

The balance of zinc and lead is calculated during steel smelting in an electric arc furnace (EAF). It is shown that the main proportion of zinc and lead is removed from metal during charge melting in an EAF, and the remaining amount evaporates during steel degassing. With an increase in the proportion of galvanized steel in a charge, dust formation and zinc and lead contents in EAF discharges increase considerably. In order to determine a strategy for treating zinc-containing dust, it is necessary to monitor its content in all production stages.

Modern vacuum systems for steel degassing units

The operating principles, the technical characteristics of the main types of modern vacuum pumps used in steel degassing units, and the peculiarities of using vapor-et and mechanical pumps in industrial practice are considered. It is noted that, in recent years, mechanical pumps are used to provide a higher evacuation rate and degree of evacuation and to reach a decrease in the operating costs on their maintenance and steel degassing.

Modern Vacuum Pumps for the Vacuum Degassing of Steel in Small and Large Vacuum-Degassing Units

This article discusses a new design for Roots pumps and screw pumps which uses hermetically sealed motors. The new pump is easy to maintain, alleviates wear, and increases safety, which makes it more reliable than traditional Roots pumps. The screw vacuum pumps operate within a wide range of pressures. Thanks to the absence of friction in the vacuum chamber and the use of special coatings on the working elements, these units can be used in place of water-ring and rotary vane pumps for the high-vacuum evacuation of gases and vapors of liquids (including aggressive liquids). In this case, the gas being pumped is not contaminated by water vapor or oil. The absence of friction elements in the vacuum chamber means that the unit requires almost no maintenance. The use of standardized pre-equipped modular building blocks reduces fabrication and installation/startup costs, makes the equipment more compact, and saves power, oil, and water compared to other systems. The small size of both types of pumps – which can be used in any configuration – not only shortens delivery times and simplifies spare-parts management but also facilitates equipment assembly or (if necessary) replacement. Attainment of the pumps’ rated productivity is assured by parallel connection of several compact modules. The mechanical pumps can be used for VID, VIM, VD, RH, VIT (vacuum ingot teeming), and VAR (vacuum-arc remelting) units, including units that perform vacuum-oxygen decarburization. The pumps’ design incorporates measures to protect against dust and water-vapor condensation, which can lead to the formation of acidic liquids. The pumps can be used in all types of vacuum processes – including processes that involve the injection of oxygen – while observing existing safety standards. The low inertial mass of the pumps helps them respond rapidly to frequency control, which facilitates the evacuation process. Redundant operation is provided for in all the pumping-unit configurations.

Physicochemical grounds for the substitution of nitrogen for argon during out-of-furnace treatment of high-carbon steel

Physicochemical grounds for the possibility of replacing of argon with nitrogen during blowing a metal in the course of degassing and in a ladle-furnace unit are obtained using a mathematical model of degassing steel for out-of-furnace treatment. According to the data of examining the model for adequacy, the calculation error does not exceed 1%. A numerical experiment demonstrates that the replacement of argon with nitrogen during degassing of steel does not lead to any increase in the nitrogen content in it. Blowing in a ladle-furnace unit can be performed using an argon-nitrogen mixture taken in the proportion (2–3): 1. The replacement of argon with nitrogen allows the cost of the out-of-furnace treatment of steel to be decreased.

Economic aspects of the vacuum treatment of steel by VDF/VODF technology

Calculations are performed to determine the economic benefit from changing over to the traditional VD/VOD technology for the vacuum degassing of steel in ladles to the new VDF/VODF technology. A vacuum-degassing unit currently in use at the Severstal Metallurgical Combine is used as an example.

Economical vacuum degassing of steel with the use of mechanical pumps

If greater use is to be made of vacuum technologies in out-of-furnace treatments of steel within Russia, more stringent requirements will have to be met in regard to the reliability, productivity, and efficiency of the pieces of equipment used to create the vacuum-the vacuum pumps. Unfortunately, Russian-made vacuum pumps do not presently meet these requirements.

Steel Detritiation by Melting with Gas Bubbling

ABSTRACTThe waste management is a challenge for any future fusion facility including ITER. Detritiation could allow easier procedures since the practices in different countries already limit tritium contents and releases for disposal in nuclear waste storage. The experience developed in steel-making processes, for liquid steel degassing by gas injection, has been applied for modeling of tritium removal. A numerical model, initially developed at IRSID (USINOR’s Process Research Center) for hydrogen removal, is adapted to determine detritiation efficiency.The hydrogen isotope transfer between liquid metal and injected gas occurs in two elementary steps, liquid phase mass transfer and interfacial reaction driven by Sievert’s law for H2 and T2. In the gas phase, H2 and T2 react to give HT, according to the thermodynamic equilibrium and the isotopic exchange. The model takes into account the change in bubbles swarms (sizes and velocities) as they ascent from the bottom of the vessel to the metal free surface.It is thus possible to predict the tritium content evolution during the treatment as a function of process parameters. Duration and inlet gas mixture, which have the major influence on detritiation efficiency, must be set according to the tritium initial concentration and the activity expected in the final waste.

Service of refractories in a combined installation for steel degassing in magnitogorsk metallurgical works

An installation with a removable hearth for out-of-furnace steel degassing which can be used for batch and circulation degassing is described. The most stable refractories are chosen for operation in various zones of the lining. The outer lining of the chutes is made of a low cement corundum concrete.

Refractories for vacuum degassing of steel

New equipment for outside-the-furnace vacuum degassing of steel includes argon-oxygen refining units, circulation flow vacuum degassing units, and units for steel degassing in the ladle with electric arc heating. The refractories developed for use in this equipment include magnesia, periclase-carbon, corundum, alumina, periclase-lime, magnesia-dolomite, forsterite, and unformed and vibrocompacted refractories. The refractories were selected for heat resisting and thermal insulation applications. This paper reviews at length the raw material base, production processes, and applicable properties of these refractories under degassing conditions, including slag and silicate resistance, temperature and phase behavior, permeability, compression strength, service life, and wear behavior. In addition, specifications are given for a wide range of refractories and their applications in specific pieces of equipment. Savings in refractory and power consumption are discussed.

Porous magnesite plugs for degassing of steel through the ladle bottom

We have developed a technique for production of porous magnesite plugs with coal as the combustive additive. Such plugs are suitable for degassing of steel with argon supplied through the ladle bottom. They can withstand 3–4 degassing cycles. Degassing of steel with argon through porous magnesite plugs fabricated by the Magnezit Plant permits a reduction in hydrogen content by 1.0–2.5 cm3 per 100 g of metal and a fourfold or fivefold reduction in the content of nonmetaliic oxide inclusions in ball-bearing and structural steels smelted in the usual manner.

The significance of the circulation rate on the vacuum treatment of liquid steel with the RH process

The RH Vacuum Process is in operation in more than 30 steel plants all over the world, especially for the vacuum treatment of liquid steel, ie vacuum metallurgy, steel refining as well as steel degassing. In the RH process the circulation rate is of great importance, since it exerts a controlling influence on degassing velocity, time of exposure of the liquid steel to vacuum (residence time), alloy addition rate as well as mixing of the steel in the ladle The dependence of circulation rate on the suction tube diameter and lift-gas rate was determined. The influence of the circulation rate on process variation, residence time and mixing in the ladle were also investigated. It can be concluded that suction velocities of 125 cm/sec are attained by lift-gas injection. Based on this lifting mechanism, a circulation rate of 45 t/min can be achieved with suction tube diameters of 330 mm. If ladle size and treatment time require it then the circulation rate can be increased without difficulty by enlarging the suction tube diameter. Such process conditions create residence times which will meet the requirements of the reaction variation and the dissolution of added alloys. In order to obtain short mixing times in the ladle, run-off velocities of more than 150 cm/sec were chosen, so that in a 100 ton ladle a homogeneous distribution of degassed steel or added alloys may be achieved in less than 2 minutes.

1173. Steel degassing. Part V. The Gero process: J D Clark,Marconi Instrum, 39 1966, 466–468.

1173. Steel degassing. Part V. The Gero process: J D Clark,Marconi Instrum, 39 1966, 466–468.

Vacuum degassing of steel outside the furnace

Vacuum degassing of steel outside the furnace

1597. Steel degassing by the process of the Bochumer Verein

1597. Steel degassing by the process of the Bochumer Verein

The Use of Steam Ejectors for the Vacuum Degassing of Steel

Steam ejectors have now become the established pumping system for degassing molten steel because of their high gas handling capacities at low pressures. The stream and ladle degassing processes are described including plant required in addition to the ejectors. Theoretical consideration is given to the operation of a steam ejector, and the design requirements for a complete multi-stage plant to operate at less than 1 torr are discussed. Finally the economies and benefits derived from the processes are outlined and future trends indicated.

863. Steel degassing. Part 3: The Ruhrstahl-Heraeus process: J D Sharp, Iron Steel, 38, June 1965, 334–336

This paper investigates the usefulness of the Hazard and Operability technique, (HAZOP) as a tool for predicting relevant accident scenarios by applying this technique, together with a specific design analysis technique, in a Dutch steelworks. Adaptation of the hazop guide words to the steelworks process functions enables the identification of possible production deviations in the newly built ladle arc furnace and in the transport to and from the furnace. The deviations, which are all related to disturbances in the production process, are clustered on a common consequence base and by assigning high and low incidence grades to the clusters, 13 accident scenarios can be formulated. Reviewing 16 months of experience with the ladle arc furnace shows that 58% of actual deviations can be brought under the defined production-related accident scenarios. Another 28% can be explained by introducing three additional maintenance-related accident scenarios.

1000. Ladle-to-ladle vacuum stream (steel degassing): W H McClure,, Trans Vac Metall Conference, 1964, Amer Vac Soc, Boston, Mass, (1965), pp 465–475

1000. Ladle-to-ladle vacuum stream (steel degassing): W H McClure,, Trans Vac Metall Conference, 1964, Amer Vac Soc, Boston, Mass, (1965), pp 465–475

Physical considerations in the stream degassing of steel

Physical considerations in the stream degassing of steel