Fractional Gas Analysis Research Articles

Development of a methodology for determining the content of non-metallic inclusions in steel

As part of the study, a method was proposed for assessing the metal purity for non-metallic inclusions using optical emission spectrometry. To assess the content of non-metallic inclusions in the slabs, two columns of metal were selected from two slabs of low-alloy metal deoxidized with aluminum. Each column was divided into seven samples in the direction from the small radius of the continuously cast ingot to the large one. We studied these samples to assess metal contamination with non-metallic inclusions using quantitative optical metallography according to ASTM E1245-03, fractional gas analysis (FGA) and optical emission spectral analysis PDA. Analysis of the samples according to ASTM E1245-03 standard showed that in all samples the percentage of oxides and sulfides is on average 10 and 90 %, respectively. According to the results of FGA, it was concluded that such non-metallic oxide inclusions as aluminates predominate in the metal samples of both ingots. A comparison was made between the results of the determination of oxygen in non-metallic inclusions obtained by FGA method and the number of sparks in inclusions at the analysis by PDA method; analysis of the dependencies showed that there are two clearly defined point distributions. To carry out PDA analysis, a program was deve­loped that allows determining the number of inclusions of various types and calculate their volume fraction.

Application of Fractional Gas Analysis to Control the Production of 22GYu Steel

Application of Fractional Gas Analysis to Control the Production of 22GYu Steel

Database Clustering after Automatic Feature Analysis of Nonmetallic Inclusions in Steel

Non-metallic inclusions (NMIs) in steel have a negative impact on the properties of steel, so the problem of producing clean steels is actual. The existing metallographic methods for evaluating and analyzing nonmetallic inclusions make it possible to determine the composition and type of NMIs, but do not determine their real composition. The analysis of single NMIs using scanning electron microscope (SEM), fractional gas analysis (FGA), or electrolytic extraction (EE) of NMIs is too complicated. Therefore, in this work, a technique based on the automatic feature analysis (AFA) of a large number of particles by SEM was used. This method allows to obtain statistically reliable information about the amount, composition, and size of NMIs. To analyze the obtained databases of compositions and sizes of NMIs, clustering was carried out by the hierarchical method by constructing tree diagrams, as well as by the k-means method. This made it possible to identify the groups of NMIs of similar chemical composition (clusters) in the steel and to compare them with specific stages of the steelmaking process. Using this method, samples of steels produced at different steel plants and using different technologies were studied. The analysis of the features of melting of each steel is carried out and the features of the formation of NMIs in each considered case are revealed. It is shown that in all the studied samples of different steels, produced at different steel plants, similar clusters of NMIs were found. Due to this, the proposed method can become the basis for creating a modern universal classification of NMIs, which adequately describes the current state of steelmaking.

Interaction of rail steel melt with refractory lining

The rail steel properties are adversely affected by rigid non-metallic inclusions, containing aluminum oxides. Therefore, aluminum content is limited to 0.004 % wt. in rail steel grades. Aluminum can get into steel from charge materials and refractory lining. In this work, we’ve analyzed how the chemical composition of refractories used in rail steel making influence steel quality on example of one domestic enterprise. To determine the main types of non-metallic inclusions created in E76F rail steels, we have performed fractional gas analysis of the samples taken in various process steps. It was found that the slag composition after degassing changes insignificantly, while the most part of non-metallic inclusions in rail steel is represented by aluminates.

Application of Some Modern Analytical Techniques for Characterization of Non-Metallic Inclusions in a Fe-10mass%Ni Alloy Deoxidized by Ti/Zr and Ti/Mg

In this study, a complete and comprehensive analysis of non-metallic inclusions (NMI) in an Fe-10%Ni alloy was done by using two modern analytical methods that complement each other: Electrolytic Extraction (EE) of inclusions from metal samples followed by investigations by using Scanning Electron Microscopy (SEM) and Fractional Gas Analysis (FGA). The composition, morphology, size and number of different NMIs and clusters were investigated in metal samples taken after deoxidation by additions of Ti, Ti/Zr and Ti/Mg. The obtained results were discussed with respect to formation, modification and removal of NMIs and clusters depending on the type of deoxidations and the holding time. It was found that the peaks of oxygen reduced from different oxide inclusions obtained by the FGA measurements corresponded well to the main types of inclusions and clusters observed by using the EE + SEM method. More specifically, the total O content in oxide inclusions (ONMI) increases by 10% after a Zr addition and then decreases linearly by 40% during 5 min of holding due to flotation of NMIs and clusters. However, after a Mg addition in the melt deoxidized by Ti, the ONMI content decreases drastically by 63% during 5 min of holding, due to a fast floatation of NMIs caused by bubbles of vaporized Mg.

Influence of introduction of carbon and fluorine additives to fluxes made of silicomarganese slag

The authors have carried out the investigations of fluxing agent containing silicomanganese slag with a flux additive based on gas treatment dust of aluminum production. Influence of carbon-fluorine-containing additive introduction on total oxygen and hydrogen content in weld metal has been studied, as well as its influence on impact strength at positive and negative temperatures. For fluxing agent manufacture, silicomanganese slag was used as a base, and aluminum production electrostatic precipitators dust was used as additive. Silicomanganese slag is produced by the West Siberian Electrometallurgical Plant; dust is from aluminum production electrostatic precipitators (carbonfluorine- containing adding) of RUSAL Co. Samples were welded on ASAW-1250 welding tractor. Chemical composition of studied welded samples was investigated according to GOST 10543 – 98 by atomic emission method on DFS-71 spectrometer and by X-ray fluorescence method on XRF-1800 spectrometer. Fractional gas analysis was performed using LECO TS-600 analyzer. Welded samples were tested for impact strength at positive and negative temperatures using impact pendulum-type testing machine according to GOST 9454 – 78. When using a carbon-fluorine-containing flux additive in welding flux based on silicomanganese slag, amount of oxygen and hydrogen in weld metal decreases, while impact strength increases at positive and negative temperatures. Dependences of the amount of oxygen and hydrogen in weld metal and impact strength on the amount of introduced carbonfluorine- containing flux additive were constructed.

Effect of Carbon and Fluorine Added to Silicomarganese Slag Fluxes

A welding flux containing silicomanganese slag with a flux additive based on dust taken from gas cleaning facilities of aluminum industry has been studied. The following has been studied: the effect of a carbon-and-fluorine-containing additive exerted on the content of total oxygen and hydrogen in the welding seam’s metal, as well as on the impact strength in the positive and negative temperature range. To make the welding flux, silicomanganese slag produced by the West Siberian Electrometallurgical Plant has been used as a base. Also, a flux additive has been used to make carbon-and-fluorine containing dust taken from the electrostatic precipitators of RUSAL’s aluminum-producing enterprises. The samples have been welded using an ASAW-1250 welding tractor. The chemical composition of the welded samples under study has been determined according to GOST (State Standard) 10543–98 by means of an atomic emission technique using a DFS-71 spectrometer and by means of means of an X-ray fluorescence technique using an XRF-1800 spectrometer. Fractional gas analysis has been performed using a LECO TC-600 analyzer. The welded samples have been tested for impact strength in the positive and negative temperature range using a pendulum impact testing machine according to GOST (State Standard) 9454–78. Upon using a carbon-and-fluorine-containing flux additive in the welding flux based on silicomanganese slag, the amount of oxygen and hydrogen in the welding seam’s metal exhibits a decrease. At the same time, the impact strength in the positive and negative temperature range exhibits an increase. The curves for the amount of oxygen and hydrogen in the welding seam’s metal, as well as for the impact strength depending on the introduced amount of carbon-and-fluorine-containing flux additive, are plotted.

Development of digital twins and optimization of resource-efficient steelmaking technologies

In this study, mathematical models, algorithms and software for dynamic simulating of processing technologies in a ladle furnace and vacuum degassers were developed, and a new method for optimizing ladle processing technologies for various steel grades was created. Physicochemical models were developed based on the laws of conservation of mass and energy, as well as the principles of non-equilibrium thermodynamics. The developed software allows us to calculate the basic characteristics of steel refining processes, such as temperature and chemical composition of slag and steel melts, kinetics of refining processes, economic indicators, energy and resource efficiency of technologies. To validate the software, the results of industrial hits and the results of the control of metal and slag were used. Nonmetallic inclusion analysis procedures have been developed using the fractional gas analysis method to control of steel cleanness and to detect and adjust the sources of inclusions formation at all stages of ladle furnace steel processing. For various steel grades, it was shown that it is possible to successfully optimize technologies using a combination of developed modeling software and fractional gas analysis. A mathematical model for the interaction of a high chromium iron base melt with a low temperature plasma was developed. Comparison of the experimental results in DC arc furnace with calculating data is in a good agreement.

CONTENT MODIFICATION OF DIFFERENT TYPES OF NONMETALLIC INCLUSIONS DURING LOW-CARBON IF STEEL LADLE TREATMENT

Development of advanced materials for the automotive industry allows us to produce a lighter body without losing strength characteristics of the structure. It became possible by the creation and subsequent introduction into the production of such steel grades as IF (Interstitial Free) – steel with no interstitial solute atoms to strain the solid iron lattice and IF-BH (Bake Hardening) – steel with hardening during hot drying. The article provides a brief overview of the history of the emergence of IF steel and the current situation in the production of it in Russia. One of the quality criteria for steels of IF grades is purity of the metal by non-metallic inclusions (NMI), which negatively affect the plastic properties of the material, lead to the formation of surface defects of flat rolled products and reduce the manufacturability due to a decrease in the casting speed of steel, as they cause overgrowing of steel casting nozzles. The article presents investigation results of the content, composition, size and morphology of non-metallic inclusions (NMI) in the metal samples taken at all stages of ladle treatment and casting of IF steel grade production using quantitative metallographic analysis, electrochemical dissolution (ED) followed by X-ray microanalysis of isolated inclusions, Auger electron spectroscopy and fractional gas analysis (FGA). As a result of the analysis of inclusions in the studied samples using a scanning electron microscope, according to morphological features, five characteristic types of inclusions were identified, which reduce the performance properties and strength cha racteristics of the materials produced from them. Results of the analysis of nonmetallic inclusions in metal samples obtained by the ED method are in good agreement with the results of the determination of oxide nonmetallic inclusions by the FGA method. The method of fractional gas analysis shows the dynamics of changes in the content of various types of oxide nonmetallic inclusions during the secondary (ladle) treatment of steel. It is shown that application of the FGA method allows to make analysis of causes of the harmful NMI formation in the metal and to correct operations at ladle treatment.

Concentration of Oxygen and Forms of It in TaC Nanopowders

Nanocrystalline powders with average particle sizes of 20 to 40 nm are obtained via the high-energy milling of microcrystalline TaC powder. The phase composition, morphology, specific surface area, and particle size of nanopowders are analyzed by means of X-ray and laser diffraction, SEM, and BET. The experimental dependence of the concentration of oxygen in nanopowders on their specific surface area is obtained. Thermodynamic simulation and fractional gas analysis show that oxygen in TaC nanopowders is mainly in the chemisorbed state and forms 5–7 monolayers of the Ta2O5 oxide phase on the surfaces of particles, regardless of their size. It is established that in contrast to microcrystalline powders, the heating of TaC nanopowders can be accompanied by considerable decarbonization and a change in phase composition.

RESEARCH AND DEVELOPMENT OF NEW CARBON-FLUORINE-CONTAINING ADDITIVES FOR WELDING FLUXES

Experimental study of the effect of the introduction of carbonfl uorine additives containing 14,01 – 22,72 % Al; 13 – 22,04 % F; 13,16 – 21,34 % C; 8,27 – 13,4 % Na; 0,09 – 0,14 % K; 0,66 – 1,09 % Ca; 26,11 – 42,35 % SiO2 ; 1,15 – 1,86 % FeO; 0,07 – 0,12 % MnO; 0,001 – 0,1 % MgO; 1,47 – 2,38 % S; 0,03 – 0,05 % P into oxidative fl uxes AN-348, AN-60, AN-67 when welding of steel 09G2S and aluminate-base OK Flux 10.71 fl ux at welding of steel 10HSND has been carried out. In the experiments it has been shown that from the point of view of the exclusion of formation in the weld of non-metallic inclusions, it is optimal to use carbon as a deoxidizer, as formed with the participation of gaseous carbon compounds (CO and CO2 ) are easily removed and do not contaminate the weld metal with non-metallic inclusions. The studies have shown that the carbon-fl uorine-containing additive in the composition of the fl uxes has a positive effect on the quality of the weld. It has been found out that when using the analyzed additives in the amount of 4 - 6% in the data fl uxes the overall oxygen content in the weld reduces. Fractional gas analysis revealed that the largest number of aluminates and silicates adversely affect the physico- chemical properties of welded joints, contained in the submergedarc welding of AN-60 and OK Flux 10.71, with the introduction of additives the reduction of these compounds has been observed, while in AN-348 and AN-67 fl uxes changes have been insignifi cant. When using the proposed additives the required mechanical properties, as well as impact strength at low temperatures by reducing contamination of the weld with oxide non-metallic inclusions increase, and the concentration of carbon in the weld remains at the level of the base metal.

Concentration and state of light elements in titanium carbide nanopowders

We have studied the effect of process parameters (temperature) in the reduction of titanium oxide with calcium hydride and calcium carbide on the concentrations and state of light elements (H, O, N, C, and S) in the reaction product and identified the oxygen-containing phases present in the titanium carbide (TiC) nanopowders obtained by reducing TiO2 with calcium hydride and calcium carbide. The oxygen present in the powders can be divided qualitatively and quantitatively into oxygen in adsorbed water, oxygen in organic compounds on the surface, and oxygen in the oxide layer on the surface of the carbide nanoparticle. We have performed fractional gas analysis for carbon in the titanium carbide nanopowders and assessed the effect of synthesis temperature on the average particle size and oxygen content of the nanopowders.

Production of carbide and hard-alloy mixture nanopowders with low-temperature plasma

The processes to produce nanosized tungsten carbide powders as well as other transition metal carbides have been investigated with the use of plasma-chemical reduction synthesis. The basic regularities of producing powders of specified dispersion and composition have been determined. Characteristic particle sizes of carbides are 40–80 nm. For the purpose of homogeneous WC–Со nanopowders mixture production with exact mass content, a technique of cobalt sedimentation onto tungsten carbide powder with simultaneous adding of retardant-carbides such as chromium, va- nadium, and tantalum carbides has been developed. The produced nanopowders have been examined with modern methods including high-reso- lution SEM and fractional gas analysis.

Preparation of nanopowders of carbides and hard-alloy mixtures applying low-temperature plasma

The preparation of nanodimensional powders of tungsten carbides, as well as other transitionmetal carbides, using plasma-chemical reduction synthesis are investigated. The main regularities of preparing powders of specified dispersity and composition are revealed. Characteristic particle sizes of carbides are 40–80 nm. In order to prepare a homogeneous mixture of WC-Co nanoparticles with an exact weight content, the procedure of deposition of cobalt on the tungsten carbide powder with the simultaneous introduction of an additive of inhibitor carbides such as carbides of chromium, vanadium, and tantalum is developed. The prepared powders were investigated using modern methods, including high-resolution scanning electron microscopy and fractional gas analysis.

Effect of a pipe-steel killing technology on the composition and number of nonmetallic inclusions

Pipes made from steels 19G, 17GS, 17G1S, 10G2FBYu, 13G1S-U, and 20KT of various manufacturers and technologies are studied. Electron microprobe and fractional gas analyses are used to determine the main types and number of nonmetallic inclusions (NIs). The effect of a modification procedure on the oxidic cleanness of steel 20KT (produced at JSC “Volzhskii Pipe Works”) is studied. The use of a silicocalcium-filled wire is shown to increase the total contamination of the steel by nonmetallic, in particular, calcium aluminate and magnesium spinel inclusions, which are conditionally related to corrosion-active nonmetallic inclusions (CANIs). Fractional gas analysis is shown to allow the number of oxide inclusions of various types to be accurately determined in pipe steels. No correlation is found between the volume fraction of oxide inclusions determined by fractional gas analysis and the number of CANIs determined by a metallo-graphic method.

Nonmetallic inclusions in electric furnace steel ShKh15SG-V bars

The mechanisms of formation and the methods of controlling nonmetallic inclusions (NIs) in bearing steel are considered. The number and composition of NIs in electric furnace ShKh15SG-V steel bars made using various versions of heat and out-of-furnace treatment are studied by fractional gas analysis and number estimation according to State Standard GOST 801-79. A high calcium content is found to result in large globular NI numbers in the bars. Fractional gas analysis is shown to correctly determine the oxide inclusion content in steel.

Temperature-time melting conditions for a YuNDKT5BA magnetic alloy prepared from a rated charge of a given composition

Fractional gas analysis is used to study the behavior of the oxide and nitride phases in Al-Ni-Co-based alloys (YuNDKT) prepared from a rated charge of a given composition during high-temperature treatment of a melt (before its casting) at 1650–1750°C for 30, 120, and 300 s. The total oxygen and nitrogen contents in the alloys are found to vary periodically (wavelike increase and decrease) as the time of melt holding at a given temperature increases. It is ascertained that, for any given temperature in the range from 1650 to 1750°C, the melt holding time that results in the minimum oxygen and nitrogen contents can be determined. A sequence of the processes that proceed during holding a melt at a given temperature is suggested to explain wavelike variations in the contents of gas-forming impurities in these alloys. The results obtained can be used to improve the technology of melting of magnetically hard YuNDKT-type alloys using open induction furnaces and rated charge.

Analysis of various versions of the deoxidation of rail steel at OAO NTMK

The deoxidation of steel melted using various types of deoxidizers during out-of-furnace treatment is studied. The total oxygen and nitrogen content and the oxygen contents in the main types of oxide nonmetallic inclusions are determined by fractional gas analysis of steel samples taken from heats performed by various schedules. The main types of nonmetallic inclusions and their size distributions are found with qualitative and quantitative metallography. The oxygen content in the rail steel is minimal (5 ppm) when calcium carbide CaC2 is introduced into the metal in tapping of a converter. When the metal is deoxidized using a steel wire filled with calcium or a steel wire filled with silicocalcium, the oxygen content in rail steel is ≈8 and ≈11 ppm, respectively. A comparison of various processes of rail steel deoxidation under the OAO NTMK conditions shows that the limitation of the aluminum content (no more than 30 ppm) or the use of a wire with a calcium or calcium carbide filler is more effective than the use of a wire filled with silicocalcium.

Investigation of the oxidized layer of anisotropic electrotechnical steel by methods of layer-by-layer spectral and fractional gas analyses

Investigations of the surface layer of specimens of anisotropic electrotechnical steel (AETS) sampled after decarburizing annealing are performed. For this purpose, procedures of layer-by-layer spectral and fractional gas analysis (FGA) of the internal oxidation region of AETS are developed. The effect of controlling parameters of the layer-by-layer analysis of AETS specimens on an SA-2000 glow-discharge spectrometer (LECO) on the crater shape is investigated. The procedure for analysis of the internal oxidation region of AETS formed during decarburizing annealing with the use of a scanning electron microscope and preliminary ion etching on the SA-2000 glow discharge spectrometer is developed. It is shown that the use of FGA allows one to qualitatively identify the main oxide phases entering the internal oxidation region of electrotechnical steel. Using layer-by-layer spectral and fractional gas analyses, the effect of duration of decarburizing annealing of AETS specimens on the distribution of oxide phases and concentration profiles in the internal oxidation region is shown.

New possibilities of modern methods for determining gas-forming impurities in metals

The main tendencies in the development of methods for determining gas-forming impurities in metals and alloys, and the physicochemical laws of the fractional separation of oxygen are considered. Examples of the analysis of model alloys and steels show that the method of fractional gas analysis can be used for the quantitative determination of oxygen bound in inclusions.