Degree Of Deoxidation Research Articles

Thermodynamic investigations of steel deoxidation process with calcium and barium

The use of alloys with alkaline earth metals (AEM) it possible to optimize the processes of deoxidation and refining of steel from non-metallic inclusions. The technologies of ladle treatment of the melt with the use of AEM complexes to obtain high-quality metal products even if it is impossible to use expensive equipment (vacuumers, tribe apparatus, etc.), which is often typical for small steel foundries. At the same time, a number of issues related to the mechanisms implemented during the refining of liquid steel with calcium and barium require further study. In the course of this work, the authors constructed state diagrams of double (CaO–BaO) and ternary (FeO–CaO–BaO) oxide systems and carried out thermodynamic modeling of equilibria in the Fe–Ca–Ba–C–O system. It is noted that in this system there is an extensive equilibrium region of the oxide melt with solid solutions of CaO-based oxides. The solubility surfaces of components for the temperatures of steel ladle treatment (1550–1600 °С) and for different carbon contents (0; 0,1; 0,4 % С) are constructed for the studied system. A comparative analysis of the constructed diagrams suggests that a change in the carbon content within the indicated limits does not significantly affect the type of the diagrams. It follows that the revealed patterns will be maintained in the production of a wide range of economically alloyed low-carbon steels. It is shown that during the deoxidation of steel without aluminum, and with a calcium content typical for real production processes (about 30 ppm), the expected active oxygen content is about 30 ppm (log[O] = –2.5), which does not meet modern requirements for purity become. At the same time, a change of the barium content has practically no effect on the degree of deoxidation of the metal. Thus, it is shown that the main role of calcium and, especially, barium in the processing of liquid steel is modification and removal of non-metallic inclusions from the melt

Pyrolysis of different types of waste cooking oil in the presence/absence HZSM-5 catalyst: Influence of feedstock characteristics on aromatic formation

In this study, aromatics were prepared by continuous microwave pyrolysis experiment in the presence and absence of HZSM-5 using different types of waste cooking oil (corn oil, rice oil, rapeseed oil, sunflower seed oil, soybean oil, blending oil, peanut oil, palm oil), and the effects of raw material characteristics on pyrolysis products were compared. The results showed that the fatty acid composition of waste cooking oil affects the composition of pyrolysis products. For example, linoleic acid promotes naphthene and inhibits olefin formation; oleic acid is easy to form C9 and C10 compounds; compared with oleic acid and linoleic acid, palmitic acid is not conducive to deoxidation. In addition, the deoxidation degree of waste cooking oil is related to the raw material H/Ceff, and the order from high to low is corn oil > rapeseed oil > sunflower seed oil > peanut oil > soybean oil. The yield of the oxygen-containing compounds is inversely proportional to it. With the use of HZSM-5 catalyst, the content of toluene and xylene in liquid products is significantly increases, especially the content of xylene. The catalytic effect of rice oil is the most significant, with xylene content increased by 19.2% compared with the non-catalytic pyrolysis. This provides a reference for the efficient treatment of waste oil and the production of aromatics in the future.

THERMODYNAMIC MODELING OF PHASE EQUILIBRIA DURING DEOXIDATION OF THE LOW AND MEDIUM CARBON STEELS BY SILICOMANGANESE

To create digital twins of steelmaking production, it is necessary to develop programs for calculating all stages of smelting and secondary treatment of steel and alloys, including the process of deoxidation. The aim of this work was to construct a phase stability diagram in the form of a surface of solubility of components in a metal (SSCM) of the Fe–Si–Mn–O–C system for carbon concentrations [C] = 0; 0.1; 0.4 wt. % and a temperature of 1600 °C. SSCM will make it possible to establish the stability boundaries of non-metallic inclusions (NI) formed during deoxidation and the degree of deoxidation of low- and medium-carbon steel, depending on the introduced concentrations of silicon and manganese. It is noted that in the system under study, during absence of carbon ([C] = 0 wt. %) an oxide melt of variable composition (FeO, MnO, SiO2) with a minimum concentration of iron oxide prevails as nonmetallic inclusions. With the appearance of carbon in the melt, the region of equilibrium of the liquid metal with the gas phase {CO, CO2} was established, and with an increase in the concentration of carbon, this region increased. For low-carbon steels ([C] = 0.1 wt. %) at industrially significant concentrations of silicon (0.1–0.3 wt. %) and manganese (about 1.0 wt. %), NI in steel also represent oxide melt. In medium-carbon steels ([C] = 0.4 wt. %) at the same silicon and manganese concentrations, the deoxidation product is in the gas phase. In the course of modeling, the isotherms of oxygen solubility in the system under study were also constructed. The simulation results are in good agreement with the literature data. The constructed SSCM can be used to create a digital twin of the deoxidation process of steels.

Thermodynamic model and mechanism of non-alloyed hydrogen deoxidation of GCr15 bearing steel

ABSTRACT A new method of non-alloyed hydrogen deoxidation is proposed, and the hydrogen deoxidation of GCr15 is studied using thermodynamic modelling. Deoxidation by blowing hydrogen is dominated by hydrogen molecular, and the degree of deoxidation depends on , which is independent of [H]. Carbon and hydrogen will compete for deoxidation during the blowing of hydrogen. The deoxidation mode depends on the relationship between the actual and the critical . The system pressure has a great influence on the carbon / hydrogen deoxidation equilibrium. Under vacuum conditions, carbon has a stronger deoxidation ability than hydrogen. Finally, a new process for hydrogen deoxidation was proposed. In the later stage of converter smelting, hydrogen was blown to reduce the excess oxygen → tapping, and hydrogen was blown to alternate deoxidation of carbon and hydrogen → sufficient carbon powder was added into the ladle → RH treatment, and hydrogen was stopped to blown, and carbon deoxidation occurred.

Evolution of Chemical Composition and Modeling of Growth Nonmetallic Inclusions in Steel Containing Yttrium.

The programs WYK_Stal and Bi-Growth, developed at AGH-UST, Kraków, Poland, were used for simulating the refining process, the formation of non-metallic inclusions, and their growth. The Fe-Y-Al-O-S-Ca system in pre-oxidized steel was analyzed, where yttrium formed precipitates from both O and S. When first Al and second Y were added to steel, the proportion of Al2O3 inclusions remained constant. This resulted in higher yttrium losses for oxide formation, whereas the sulfur content promoted sulfide phase formation. The introduction of yttrium at the end of refining contributed to reducing the consumption of this element in the non-metallic phase formation. The addition of aluminum and then calcium were sufficient to achieve a high degree of deoxidation and desulfurization. Calculations performed with WYK_Stal for both (a) and (c) versions of the model showed that the sulfide phase was constituted by CaS and FeS (model c) and CaS (model (a)). The participation of the calcium sulfide phase turned out to be dominant in the inclusions. Their presence was also identified in the slag phase. Simulations of the growth of complex oxide and oxo-sulfide inclusions using the Bi_Growth program showed that the yttrium content of the steel has a decisive role in the formation of complex oxide inclusions and the final oxygen content of the steel. In contrast, for the growth of oxide-sulfide inclusions, the character of growth is determined by the sulfur content of steel.

Influence of the Salt Bath Deoxidation Degree on Change in Hard Alloys Properties during Heat Treatment

Performance characteristics of hard-alloy tools are largely depends on the structure. The hard-alloy tool structure can be influenced by various factors. The main factors influencing the structure and properties of hard alloys at heat treatment are ВаCl2 salt bath deoxidation degree, heating temperature, holding time, rate of cooling and cooling medium, temperatures and holding time. Oxidation at temperatures more than 500-600оС and relatively low thermal conductivity of λ = 27.214 W/(m×K) are characteristic for hard alloys under heating.In this regard, it became necessary to study the salt baths deoxidation processes occurred in the course of heat treatment. Insufficient study of hard alloy heat treatment processes is associated with peculiarity of their structure and large assortment, difficulty of setting heat treatment modes.Research of hard alloy sample heating with the subsequent air cooling (normalization) was carried out in a salt baths in thermal area of tool shop.X-ray diffraction analysis was performed by Williamson-Hall method. In our experiments, coherent scattering regions size and WC phase micro-distortions magnitude were defined using MD-10 microdiffractometer. It was found out that phase structure of hard alloys is not change as a result of heat treatment. There are only reflections from carbide phase planes in the diffraction pattern. A quantitative analysis of diffraction reflection broadening using Williamson-Hall method showed that size of the coherent scattering regions for VK8 and T14K8 hard alloys subjected to hardening procedure is more than for sintered alloys.Relevance of the study is due to the fact that heat treatment involved heating in salt baths can be a promising method of improving mechanical and operational properties of hard alloys. This approach ensures necessary strength and performance characteristics of hard alloys without significant economic expenses.The purpose of this paper is to define effect of ВаCl2 salt bath deoxidation degree on physical and mechanical properties of VK8 and T14K8 hard alloys.

Activating Precursors for Brazing Processes that Deposit Two Layers through Melting

We present the manufacturing process, by melting in a controlled environment, of specific alloys that have a benefic effect on the diffusion phenomena’s in the base material of the addition coated rods for brazing. The friable precursors obtained by melting are grinded with the purpose of integrating them in the coat of the rods, namely the addition material. The metallurgic activation activity of the precursors is enhanced by using them as nano-powders in the coat of the rods.Of major importance for deep joint capillary brazing are the fluidity and superficial tension of the melt - addition material, or, in case of non-ferrous alloys, the degree of de-oxidation of base materials. In order to improve the above mentioned characteristics, we made precursors type: 5o% Cu-45% Sn-5% P (CIF); 92% Cu-2% Si 6% P- (RAV). The batch design was done by two distinct melting processes, in high frequency currents (CIF) and electric arc (RAV) in a controlled environment. The melts were cast in graphite forms as loose briquettes. The briquettes thus obtained were analyzed structurally and sclerometrically, and after testing, they were grinded in planetary mills until we obtained nano-powders. The resulting powders will be used, as required, to prepare brazing sheaths.

ALUMINOBAROTHERMIC SYNTHESIS OF HIGH-NITROGEN STEEL

High-nitrogen austenitic steels are promising materials, combining high strength, plasticity and corrosion resistance properties. However, to produce high-nitrogen steel by conventional metallurgical methods under high nitrogen pressure, powerful and complex metallurgical equipment is required. From energy-saving viewpoint, an alternative and simpler method for producing high-nitrogen steels can be aluminothermy (reduction of metal oxides by metallic aluminum) under nitrogen pressure. Thermodynamic modeling of aluminothermic reactions in a nitrogen atmosphere was carried out by the authors. Aluminothermy under nitrogen pressure was used to produce high-nitrogen nickel-free Cr – N and Cr – Mn – N stainless steels with a nitrogen content of about 1 %. Microstructure (X-ray diffraction, metallography and transmission electron microscopy techniques) and mechanical properties were examined. Thermodynamic analysis has shown that the aluminothermic reduction reactions do not go to the end. The most important parameter of the synthesis is the ratio of Al and oxygen in the charge, the correct choice of which provides a compromise between completeness of oxides reduction, content of aluminum and oxygen in steel (the degree of deoxidation), and its contamination with aluminum nitride. Cr – N steel ingots in the cast state had the structure of nitrogen perlite (ferrite-nitride mixture), and Cr – Mn – N steel – ferrite-austenite structure with attributes of austenite discontinuous decomposition with Cr2 N precipitations. Quenching resulted in complete austenization of both steels. The compliance of the austenite lattice parameter obtained from the diffractograms for quenched Cr – Mn – N steel with the parameter predicted from the known concentration dependence for Cr – Mn – N austenitic steels indicated that all alloying elements (including nitrogen) were dissolved in austenite during aging at quenching temperature and fixed in the solid solution by quenching. Study of the mechanical properties of quenched Cr – Mn – N steel has shown a combination of high strength and ductility. It is concluded that by the aluminothermic method a high-nitrogen steel can be obtained, which, by mechanical properties, is not inferior to industrial steel – analog manufacted by electroslag remelting under nitrogen pressure.

Increase in Corrosion Resistance in Aqueous Media of Low-Alloy Steel Used as the Main Layer of Corrosion-Resistant Bimetals

The article is devoted to a study of corrosion resistance of low-alloy steels, in relation to chemical composition, heat treatment conditions, other steel properties, and heat treatment regimes. The effect of chemical composition, degree of deoxidation, and steel cleanliness with respect to nonmetallic inclusions on steel corrosion resistance is demonstrated, including those that may be used as a main layer in corrosion-resistant bimetals.

Optimisation of the Deoxidation Degree and Modification on the Cast Steel Properties Improvement at Low Temperature

Abstract Industrial conditions of obtaining thick-walled and shaped castings intended for operations at temperatures: minus 40÷60°C are presented in the paper. The selection of a cast steel grade is based on known studies [1,10,14], however due to castings wall thickness (70-240mm), the way of preparing liquid metal (deep deoxidation and modification, argon stirring in a ladle) and conditions of filling mould cavities (gating system assuring quiet filling, directional solidification and avoiding a formation of inessential heat centres), were developed to assure the required impact strength. Maintaining these parameters as well as the selection of heat treatments for the produced massive castings allowed to achieve the impact strength over 50 J/cm2 at minus 40°. This value was obtained for walls of various thickness

Catalytic hydroprocessing of fast pyrolysis bio-oil from Chlorella

Catalytic hydroprocessing of the bio-oil obtained through fast pyrolysis of Chlorella was carried out in a bench-scale continuous-flow fixed-bed reactor equipped with a Ni-Co-Pd/γ-Al2O3 catalyst. The effects of the hydrogenation temperature and the H/oil molar ratio on the moisture content, calorific value, viscosity and cetane number of the refined bio-oils were investigated at the pressure of 2×106 Pa, It was shown that the yield of the refined oil reached 89.6%, and the calorific value and cetane number were increased by 17.94% and 71.2% respectively, while the viscosity was decreased by 66.32% at the temperature of 300°C, the pressure of 2×106 Pa and the H/oil molar ratio of 120. The elemental analysis and GC-MS analysis results of the bio-oil before and after hydrogenation show that the H/C atomic ratio was increased from 1.55 to 1.97, while the oxygen, nitrogen and sulfur contents were significantly decreased. The deoxidation degree reached 80.46%. The amounts of organic acids, esters, ketones and aldehyde in the refined oils were obviously decreased, while those of alcohols and alkanes were markedly increased.

Manufacture of high-nitrogen corrosion-resistant steel by an aluminothermic method in a high-pressure nitrogen atmosphere

The conditions of aluminothermic synthesis of high-nitrogen Cr-N and Cr-Mn-N steels in a high-pressure nitrogen atmosphere are studied by thermodynamic simulation and metallurgical experiments. Thermodynamic analysis shows that the aluminothermic reduction reactions are incomplete. The most important synthesis parameter is the ratio of the aluminum to the oxygen content in a charge, and its optimum value ensures a compromise between the degree of oxide reduction, the aluminum and oxygen contents in steel (degree of deoxidation), and steel contamination by aluminum nitride. An analysis of experimental heats demonstrates good agreement between the experimental results and the data calculated by a thermodynamic model. As-cast ingots have the structure of nitrogen pearlite, and quenched ingots have an austenitic structure.

Effects of Cr - Ni 18/9 Austenitic Cast Steel Modification by Mischmetal

Abstract This paper presents the results of Cr - Ni 18/9 austenitic cast steel modifications by mischmetal. The study was conducted on industrial melts. Cast steel was melted in an electric induction furnace with a capacity of 2000 kg and a basic lining crucible. .The mischmetal was introduced into the ladle during tapping of the cast steel from the furnace. The effectiveness of modification was examined with the carbon content of 0.1% and the presence of δ ferrite in the structure of cast steel stabilized with titanium. The changes in the structure of cast steel and their effect on mechanical properties and intergranular corrosion were studied. It was found that rare earth metals decrease the sulfur content in cast steel and above all, they cause a distinct change in morphology of the δ ferrite and non-metallic inclusions. These changes have improved mechanical properties. R02, Rm, and A5 and toughness increased significantly. There was a great increase of the resistance to intergranular corrosion in the Huey test. The study confirmed the high efficiency of cast steel modification by mischmetal in industrial environments. The final effect of modification depends on the form and manner of placing mischmetal into the liquid metal and the melting technology, ie the degree of deoxidation and desulfurization of the metal in the furnace.

Production of DMR 249A Steel at SAIL, Bokaro Steel Plant

Low alloy steels are an attractive option for high performance structural applications due to cost and availability factors. A low carbon low alloyed steel, DMR 249A, was developed for strategic applications by Indian Navy at Steel Melting Shop II, Bokaro Steel Plant (SMS II, BSL). This paper enumerates the detail process variables modified for this development. DMR 249A grade was having the specified gas contents of hydrogen <2 ppm in final product for the avoidance of detrimental phenomenon like “Hair Line Cracks”. So the Hydrogen content of liquid steel was to be less than 3 ppm and this demand vacuum treatment of the steel. In absence of any Degassing unit at SMS II, BSL, making of DMR 249A steel was a challenging task. The hydrogen content of steel was controlled through restriction of hydrogen in input raw materials, control in degree of deoxidation during tapping, slag basicity at ladle furnace, argon rinsing regime and cooling of slabs i.e. control over diffusion of H2. The steel was produced with the existing infrastructure at Bokaro Steel Plant with various alloying elements and processed suitably to obtain the desired yield strength, toughness and gaseous content. The control was exercised at various stages of steel making and hot strip rolling to enable achievement of a higher degree of consistency in mechanical properties and microstructure. Quality fulfillment was a great challenge without vacuum degasser unit but Bokaro successfully made the steel with 100% customer satisfaction.

Evaluating the quality of a square semifinished section based on the degree of deoxidation of the metal

Evaluating the quality of a square semifinished section based on the degree of deoxidation of the metal

Efecto del contenido de azufre y del grado de desoxidación sobre la ductilidad en caliente de aceros inoxidables austeníticos resulfurados en estado de solidificación

The manufacture of free machining austenitic stainless steels features a specific drawback derived from their high sulphur content, which is needed for generating, into the austenitic matrix, inclusions to optimize the different machining operations. However, sulphur has a harmful effect on hot workability. This paper deals with assessing the effect of sulphur content and deoxidation level on the hot ductility of resulphurized austenitic stainless steels in as cast condition. Hot tensile tests were conducted on a Gleeble machine, at temperatures between 1,150 and 1,250°C, studying a ductility factor as a function of sulphur content, deoxidation degree, as well as type, size and distribution of sulfides. Results point out the harmful effect of increasing sulphur and oxygen contents on the hot workability of resulphurized austenitic stainless steels, and the need to control carefully the level of oxides of these steels.

A model for the silicon-manganese deoxidation of steel weld metals

From an analytical and theoretical study of flat and out-of-position gas metal arc (GMA) C-Mn steel welds containing varying additions of silicon and manganese, we conclude that the buoyancy effect (flotation obeying Stokes’ law) does not play a significant role in the separation of oxide inclusions during weld metal deoxidation. Consequently, the separation rate of the particles is controlled solely by the fluid flow pattern in the weld pool. A proposed two-step model for the weld metal deoxidation reactions suggests that inclusions formed in the hot, turbulent-flow region of the weld pool are rapidly brought to the upper surface behind the arc because of the high-velocity flow fields set up within the liquid metal. In contrast, those formed in the cooler, less-turbulent flow regions of the weld pool are to a large extent trapped in the weld metal as finely dispersed particles as a result of inadequate melt stirring. The boundary between “hot” and “cold” parts for possible inclusion removal is not well defined, but depends on the applied welding parameters, flux, and shielding gas composition. As a result of the intricate mechanism of inclusion separation, the final weld metal oxygen content depends on complex interactions among the following three main factors: (1) the operational conditions applied, (2) the total amount of silicon and manganese present, and (3) the resulting manganeseto-silicon ratio. The combined effect of the latter two contributions has been included in a new deoxidation parameter, ([pct Si][pct Mn])−0.25. The small, negative exponent in the deoxidation parameter indicates that control of the weld metal oxygen concentrations through additions of silicon and manganese is limited and that choice of operational conditions in many instances is the primary factor in determining the final degree of deoxidation to be achieved.

The composition and temperature dependence of the sulfide capacity of metallurgical slags

The concept of optical basicity and its applicability as a means of correlating the available data on the sulfide capacity of metallurgical slags has been reviewed. An excellent correlation based on very extensive data at 1500 °C, which was discussed in a previous paper, is combined with good correlations based on considerably less data at 1550 °C and 1650 °C to quantify the effect of temperature on the sulfide capacity of slags. The combined effects of slag composition and temperature have been expressed in the equation, logCs = [(22690 – 54640A)/7] + 43.6A − 25.2. Use of this equation permits the calculation of the sulfide capacity of a slag at any temperature between 1400 °C and 1700 °C simply from a knowledge of its chemical composition, and can be employed for virtually any oxide slag of interest in the field of iron and steelmaking. This, in turn, permits calculation of the equilibrium distribution of sulfur between this slag and iron or steel, provided that the oxygen potential is known or can be calculated from the degree of deoxidation applied.

Statistical relationship between the mechanical properties and grain size of structural steels

1. Statistical relationships were obtained between the yield strength and ductile—brittle transition temperature and the grain size of ferrite in commercial structural steels differing in strength. 2. The use of an equation of the Hall-Petch type makes it possible to calculate the effect of individual hardening mechanisms on the yield strength of steels. 3. The variation of the ductile—brittle temperature with grain size is satisfactorily described by equations of the type 1/Tcr=A+Blnd−1/2 and Tcr=M−Nlnd−1/2, derived from the Cottrell-Petch transition criterion (transition to brittle fracture). 4. A formal analysis leads one to expect a reduction of the cold resistance of ferrite with refining of the subgrains. The existing experimental data do not contradict this assumption. 5. The difference in the cold resistance of carbon steel differing in degree of deoxidation but with the same grain size is largest for coarse-grained steels and smallest for fine-grained steels. The cold resistance is associated with the substructure, which is more highly developed in the steel deoxidized to a lesser extent. 6. The increasing cold resistance as one passes from carbon steel to low-alloy steel to high-strength steel is due to grain refining of ferrite. With the same grain size, carbon steel is not inferior to low-alloy steel in its cold resistance and may even be superior due to its lower strength.

The Effect of Deoxidation Degree and Heat Treatment on High Temperature Strength of Cr-Mo-V Cast Steel

Cr-Mo-V cast steel was subjected to high temperature tensile tests, creep rupture tests and thermal fatigue tests to investigate the effect of aluminium deoxidation, cast block size and heat treatment on its high temperature properties (Its tensile strength, rupture strength and thermal fatigue resistance).The tensile test data show that the austenitizing temperature and the cooling rate are primary factors for the tensile strength of Cr-Mo-V cast steel. They show also that the strong deoxidation (Al 0.9kg/ton) reduces not only variation of the tensile test data owing to elimination of microporosities, but slightly decreases the ultimate strength and the 0.2% proof stress.Strong deoxidation impairs the rupture strength and ductility of Cr-Mo-V cast steel, normalized and tempered. Its double step heat treatment, however, improves its rupture ductility, although it reduces its rupture strength.The result of the thermal-fatigue tests of Cr-Mo-V cast steel shows its superior thermal-fatigue resistance to that of Cr-Mo cast steel.