Papers by Keyword: Deoxidation

Abstract: This article presents the optimal method of melting the 35XGCL (analog is JIS G 5111) low alloy steel alloy in DSP-2.0 2000 kg electric arc furnace. All the main stages of melting in an electric arc furnace are considered. In addition, analytical data on the study of the slag mode during the fluidization of the alloy are presented. The results of the evaluation of oxygen activity in metal depending on the chemical composition of slag oxidation and reduction cycles in the furnace are presented. Graphs of oxygen activity in the alloy depending on the total amount of iron, silicon, and manganese oxides in the slag are presented. Moreover, the effect of constant and additional deoxidizing aluminum content in the alloy on the impact strength of low alloy steel alloy is presented. The impact strength is improved when the constant aluminum content is in the range of 0.05-0.07%.

Abstract: Sticking of alumina as well as spinel inclusions inside the sub entry nozzles (SEN) as well as tundish nozzle is perennial problem during continuous casting of aluminum killed steel through billet casters. This results in restriction or completely blockage of flow of liquid steel through the nozzles eventually leading to abortion of sequence in billet casters and stopping of continuous casting machine. Nozzle clogging not only restricts the productivity by restraining the casting sequence, intermittent extrication of clogged alumina particles or dislodged refractory materials are a significant source of non-metallic macro-inclusions in the cast sections of billet casters. If these inclusions are not removed completely during secondary refining of steel they causes excessive clogging mainly in low carbon Al killed steels. In other grades of Al killed steel cogging is also very prominent if the deoxidation and secondary refining is not carried out properly. IISCO Steel Plant (ISP), Burnpur a new, modernised unit of Steel Authority of India Limited (SAIL) was facing problems of nozzle clogging in low carbon, low Si, Al killed grade (EWNR –electrode quality grade) resulting in premature abortion of casting sequence leading to huge productivity loss. To solve the problem of nozzle clogging in low carbon Al killed grades and other grades at ISP, optimisation of various steelmaking parameters viz. amount of Al addition & its sequence, purging regime in ladle furnace, optimisation of Ca treatment process etc has been carried out which has resulted in improvement in castability of Al Killed Steel in billet caster of ISP.

Abstract: In connection with the need to improve the quality characteristics of metal products, metallurgists are faced with the task of finding new effective methods for secondary steel processing. It is known that the use of simple, two-component materials does not significantly improve the quality of the metal. Complex modifiers with alkaline-earth elements are increasingly used for the modifying processing of steel. These modifiers allow to influence both the metal structure and the shape, phase composition and physical properties of nonmetallic inclusions. At the same time, it is known that barium and strontium practically do not dissolve in steel and are removed from the alloy in the extremely short time. The ability of barium and strontium alloys to deoxidize and desulphurize is low because of the large atomic mass of these elements. The modifying effect of alkaline-earth elements on the properties of steel is undeniable. This effect can be explained by the ability of barium and strontium to affect the magnitude of inter-phase tension in the event of contact with the phase boundary. The purpose of this work was to generalize the industrial experience of using multicomponent alloys with alkaline-earth elements for modifying of steel. Data on the effects of alloys with alkaline-earth elements on the properties of metals are given, as well as technological features of the use of complex alloys with alkaline-earth metals in steelmaking. Thus, it is noted that in conditions of large-scale steelmaking, a very important factor is the limited time in time of the modifying effect of alloys with alkaline-earth metals, which dictates the necessity of transferring the process of modification directly to casting.

Abstract: The thermodynamic characteristics of processes in the liquid metal system Fe–Y–Cr–C–O are considered as applied to low-carbon and low-alloy metal. The critical parameters for the state diagram of the oxide system Y₂O₃–Cr₂O₃ were established based on the values quoted in literature. The temperature dependence of the melting reaction constant Y₂O₃·Cr₂O₃ was determined. The coordinates of eutectic transformation points for the system Y₂O₃–Cr₂O₃ were calculated. In accordance with subregular solution theory, the energetic parameters which are necessary to calculate the activities Cr₂O₃ and Y₂O₃ of oxide melts in the system Y₂O₃–Cr₂O₃ were determined. The energetic parameters of subregular solution theories for the oxide system FeO–Cr₂O₃–Y₂O₃ were determined based on the values for the binary systems FeO–Y₂O₃, FeO–Cr₂O₃ and Y₂O₃–Cr₂O₃. The view of this diagram, as coupled with the existence domain of liquid metal within the framework of the quaternary system Fe–Y–Cr–O–С, suggests that low-carbon chromic liquid metal when injected with yttrium can form the following non-metallic inclusions: |Cr₂O₃|, |Y₂O₃|, |FeO·Cr₂O₃|, |Y₂O₃·Cr₂O₃| or oxide melt (FeO, Y₂O₃, Cr₂O₃). Oxide melt may contain up to 2 % of divalent chrome (Cr2+). The equilibrium constants for the main reactions of steel deoxidation with the formation of liquid, solid and gas products of chemical reactions were also established. The activity of components dissolved in metal was calculated using interaction parameters. The set of derived expressions for the activity of components and the dependences of equilibrium constants of chemical reactions and phase transformations allowed us to diagram the surface of component solubility in liquid metal (SCSM). SCSM diagrams show the compositions of liquid metal and indicate oxide phases which are in equilibrium with liquid metal.

Abstract: The parameters of calcium and oxygen interaction in liquid iron are revised. The Vagner parameter values of several hundreds or dozens are proved to be wrong. The recommended value for the constant for the reaction of dissolved calcium and oxygen forming solid calcia is /CaO/=[Ca]+[O] is: lgK/CaO/=-34100/T + 13.46. Vagner parameter for the interaction of Ca and O in liquid iron should be expressed in units (we used =–1.41), not in hundreds. The equilibrium diagram of calcium and oxygen content in liquid iron is calculated at 1550-1700 °C and 0.00001-0.1 mass % Ca. The minimum oxygen content possible to be achieved at 1550 °C and 1 atm is about 0.001 mass %.

Abstract: Fusibility curves of FeO–La₂O₃–Al₂O₃, FeO–Ce₂O₃–Al₂O₃, La₂O₃– Ce₂O₃–Al₂O₃ oxide systems are created based on the literature data and modern thermodynamic theories of oxide and metal melts. Admitting the oxide systems conjugation with the area of metal melts existence, we define oxide phases, which can maintain the equilibrium with metal melts of Fe–Ce–Al–O, Fe–La–Ce–Al–O systems. The surfaces of component solubility are created for above mentioned metal melts. For Fe–Ce–Al–O system it is established that the following phases can be at equilibrium with metal: Al₂O₃, Сe₂O₃, FeO∙Al₂O₃, Сe₂O₃∙11Al₂O₃, Сe₂O₃∙Al₂O₃, and the oxide melt (FeO, Al₂O₃, Сe₂O₃, СeO₂). For Fe–La–Ce–Al–O system the following oxide phases can be at equilibrium with the liquid metal: La₂O₃, Al₂O₃, Сe₂O₃, La₂O₃∙Al₂O₃, Сe₂O₃∙11Al₂O₃, Сe₂O₃∙Al₂O₃, and the oxide melt (FeO, La₂O₃, Al₂O₃, Сe₂O₃, СeO₂). Diagrams of active components consumption, which are used to establish the possibility of chosen equilibrium, are created for iron deoxidation with cerium and aluminium as well as with Ce and La at fixed Al content (0.01 wt. %).

Abstract: This paper analyzed the deoxidation principle of new-type compound deoxidizer, Si-Al-Fe alloy during stainless steel refining, summarized related studies on deoxidizer behavior, deoxidation products, alloying treatment by workers in the metallurgical in recent years, analyzed to solve a series of problems caused by deoxidation product with high melting point, and pointed out that it was a trend for large-scale production of "zero" inclusions steel or rendering inclusions harmless and functional.

Abstract: Submicron tungsten carbide (WC) powder is obtained with ammonium tungsten bronze (ATB). The samples are characterized by laser particle size analyzer and scanning electron microscope (SEM). The analysis confirms that submicron tungsten powder is obtained with ATB through the deoxidation process in the hydrogen gas (Rate of purity: 99.99 %, dew point: -40 °C). And then submicron tungsten powder is carbonized in the hydrogen gas. The volume percent content of submicron WC powder between 0 μm and 1 μm is 83.7 %. Therefore, ATB is advantageous to prepare submicron WC powder via the conventional deoxidation and carbonization processes.

Abstract: Abstract: The present experiment was conducted to a steel, Fe-20%Cr-10%Mn-6%Ni, in a 25kg intermediate frequency vacuum induction furnace at 1873K under protection of 0.08 MPa nitrogen gas. The inclusions in the steel were studied both before and after Al, Mg was added. The results revealed that the inclusions were removed more efficiently after treated by Al, Mg and the cleanness of metal was promoted to a higher level. The Al treated inclusions had more Mn, Cr and Fe at the core and a significant amount of Al around periphery according to line scanning analysis. After Mg was introduced, it concentrated at the surface of inclusions. The remaining Al content was as low as 0.01% which was lower than expected. The reaction between the Al and MgO crucible should be responsible for it and trace amount of Mg was found in the Al treated inclusions.

Abstract: The effect of the refining slag composition on the total oxygen content and inclusions in steel was investigated in 100 t UHP Electric Furnace – LF – Billet CC process. The test steel was 77B hard wire steel and Si-Mn alloy was used as the deoxidizer. Three types slag were used in the industrial tests, which including CaO-CaF2, CaO-CaF2 adding CaC and CaO-Al2O3 refining slag. The results shown that the lowest total oxygen contents of rolled bar can be gained using the CaO-CaF2 refining slag adding CaC, which is 0.0036%, while the total oxygen contents of rolled bar using CaO-Al2O3 refining slag is higher a little than the heats using CaO-CaF2 refining slag. The CaO-SiO2 and CaO-Al2O3-SiO2 compound inclusions with the size of about 5 μm are the main inclusions in the heats refining by the CaO-CaF2 refining slag in the rolled bar, but the pure, indeformable Al2O3 inclusion can also be found with the size of about 10 μm. The CaO-Al2O3-SiO2 and Al2O3-SiO2-MnO compound inclusions are the main inclusions in the heats refining by the CaO-CaF2-CaC refining slag, but most of the inclusion shape is irregular with bigger size of about 10 μm. Similar with the heat using CaO-CaF2 refining slag, the pure Al2O3 inclusion with edge angle can be found in the rolled bar. The inclusions in the rolled bar treated by CaO-Al2O3 refining slag are CaO-Al2O3-SiO2 compound inclusions, most of which are nearly globular shape with the relative small size of about 5 μm. All of the inclusions in rolled bar lie on the low melting zone in the CaO-Al2O3-SiO2 ternary phase diagram in the heats using CaO-Al2O3 refining slag. The similar condition appeared on the most of the inclusions in the heats using CaO-CaF2 and CaO-CaF2 refining slag adding CaC, while part of which are lied on the high melting zone. Therefore, considering of the plastic deformation ability, the CaO-Al2O3 refining slag is the best slag for the melting process of hard wire steel.