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Thephy sicalfoundations of the innovativemethodofwave (quantum) therapy of herniatedintervertebraldiscsarereviewed. Thismethodisbasedontherestorationofhomeostaticregulationandregenerationoftheaffectedorganusingwavemixingandresonantsuppressionofpathogenicelectromagneticemissionfrequenciesintheorganusinghigh-temperaturesuperconductivityandpre-resonanceexcitationoforgantissuesatfrequenciesinthecentimeterwavelengthrange. Themethod, ascomparedwithitsanalogue (waveshocktherapy), makesitpossiblenotonlytorelievepainbutalsotorestoretheinitialstructureoftheintervertebraldisc.

Laboratory experiment and thermodynamic calculation for the Ti-containing 24 mass pct Cr ferritic stainless steel with a CaO-SiO2-Al2O3-MgO system slag were performed to investigate the effect of slag addition on the inclusion characteristics in molten steel. The morphology, composition, and size evolution of inclusions in steel samples were analyzed in three-dimensional by the electrolytic extraction method and in two-dimensional by the automatic analysis method. The results showed that the Ti content significantly decreased after the slag addition. However, the change of the Si content showed an opposite tendency. The decrease of the Ti content in steel was due to the reduction of SiO2 and Al2O3 in the slag by dissolved Ti in steel. An increase of the TiO2 content in the slag can decrease the Ti loss in steel based on the slag-steel kinetic analysis. The total O content in the steel melt decreased from 62 to 26 ppm, and the steel cleanliness was improved, since the number density of inclusions decreased after the slag refining. The results of a kinetic analysis showed that the rate-determining step of the oxidation of Ti in the steel and the reduction of SiO2 in the slag were the mass transfer on the slag side. In addition, high Ti2O3-containing inclusions were found to be transformed to Cr2O3-Ti2O3-Al2O3 and Cr2O3-Ti2O3-SiO2 system inclusions after the slag addition. The Al2O3 contents in inclusions increased while the Ti2O3 contents decreased with time. However, there were some amount of high melting point inclusions with high Al2O3 content, which were not what we expected. When plotted on logarcxithmic scales, the mole ratio $$X_{{{\text{Al}}_{2} {\text{O}}_{3} }} /(X_{{{\text{Ti}}_2 {\text{O}}_{3} }} \cdot X_{{{\text{Cr}}_{2} {\text{O}}_{3} }} )$$ X Al 2 O 3 / ( X Ti 2 O 3 · X Cr 2 O 3 ) values of the inclusions were expressed as a linear function of the $$a_{\text{Al}}^{2} /(a_{Ti}^{2} \cdot a_{\text{Cr}}^{2} \cdot a_{\text{O}}^{3} )$$ a Al 2 / ( a Ti 2 · a Cr 2 · a O 3 ) values of the steel melts with a slope of unity, which was theoretically expected.

This research focuses on providing a detailed characteristic of non-metallic inclusions (NMIs) in 316L stainless steels with and without Ca treatment after machining using different cutting speeds. ...

Chromium is normally added to liquid alloy in the form of different grades of ferrochromium (FeCr) alloys for the requirement of different alloy grades, such as stainless steels, high Cr cast iron, etc.. In this work, inclusions in two commercially produced alloys, i.e., high-carbon ferrochromium (HCFeCr) and low-carbon ferrochromium (LCFeCr) alloys, were investigated. The FeCr alloy/liquid iron interactions at an early stage were investigated by inserting solid alloy piece into contact with the liquid iron for a predetermined time using the liquid-metal-suction method. After quenching these samples, a diffusion zone between the alloys and the liquid Fe was studied based on the microstructural characterizations. It was observed that Cr-O-(Fe) inclusions were formed in the diffusion zone, FeO x inclusions were formed in the bulk Fe, and an “inclusion-free” zone was detected between them. Moreover, it was found that the HCFeCr was slowly dissolved, but LCFeCr alloy was rapidly melted during the experiment. The dissolution and melting behaviors of these two FeCr alloys were compared and the mechanism of the early-stage dissolution process of FeCr alloys in the liquid Fe was proposed.

Nb is an important microalloying element in steelmaking. Its interaction with liquid Fe during an early stage of the alloying process has a considerable influence on the Nb recovery. In the present ...

Typical non-metallic inclusions in two industrial low-carbon steels for oil pipelines were investigated as three-dimensional objects on film filters after electrolytic extraction and filtration of metal samples. A method of soft chemical extraction using a 10%AA electrolyte was used to study the initial corrosion process in the steel matrix surrounding various non-metallic inclusions. To determine and compare “corrosive” inclusions and their influence on the initial stages of corrosion of the adjacent layer of the steel matrix, quantitative parameters (such as the diameter of the corrosion crater (Dcr) and pit (Dpit), and the relative dissolution coefficient of the metal matrix (KD) around various inclusions) were determined after chemical extraction. It was found that CaO-Al2O3-MgO oxides and TiN inclusions did not cause an initial corrosion of the steel matrix surrounding these inclusions. However, tensile stresses in the steel matrix occurred around CaS inclusions (or complex inclusions containing a CaS phase), which contributed to the initiation of corrosion around these inclusions.

Several stainless-steel slags have been successfully employed in previous studies as substitutes for lime in the treatment of industrial acidic wastewaters. This study deepens the knowledge of such application, by analyzing the neutralizing capacity of different slags related to their mineral compositions. To do so, firstly the chemical and mineral compositions of all the slag samples are assessed. Then, 0.5 g, 1 g, 2 g of each slag and 0.25 g and 0.5 g of lime are used to neutralize 100 g of 0.1 M HCl or HNO3 solutions. After the has neutralization occurred, the solid residues are extracted and analyzed using XRD spectroscopy. Then, the solubility of the minerals is assessed and ranked, by comparing the XRD spectra of the residues with the obtained pH values. The results show that minerals such as dicalcium silicate and bredigite are highly soluble in the selected experimental conditions, while minerals such as merwinite and åkermanite, only partially. Moreover, Al-rich slags seem to perform poorly due to the formation of hydroxides, which generate extra protons. However, when the weight of slag is adequately adjusted, Al-rich slags can increase the pH values to higher levels compared to the other studied slags.

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.

Samples taken from laboratory-produced 3rd generation advanced high-strength steels, solidified at a low cooling rate, have been investigated to study the characteristics of non-metallic inclusions. Two steels, containing 2 and 5 pct Mn content, were produced for this purpose. A higher number of total inclusions were observed in 5 pct Mn steel. The four main types of inclusions observed were Al2O3, AlN, MnS, and AlSiMn-oxide. These classes were divided into subclasses according to variations in their chemistry. The major subclasses of AlN inclusions are either plate-like or regular in shape and have different size distributions. Thermodynamic calculations suggest that plate-like AlN inclusions are formed at the initial stage of solidification, while faceted/regular-shaped inclusions are precipitated toward the end of solidification. Moreover, it was found that the size of nitride inclusions is related to their N content. This phenomenon is discussed from the viewpoint of nucleation theory.

Different stainless steel slags have been successfully employed in previous experiments, for the treatment of industrial acidic wastewaters. Although, before this technology can be implemented on an industrial scale, upscaled pilot experiments need to be performed. In this study, the parameters of the upscale trials, such as the volume and mixing speeds, are firstly tested by dispersing a NaCl tracer in a water bath. Mixing time trials are used to maintain constant mixing conditions when the volumes are increased to 70, 80 and 90 L, compared to the 1 L laboratory trials. Subsequently, the parameters obtained are used in pH buffering trials, where stainless steel slags are used as reactants, replicating the methodology of previous studies. Compared to laboratory trials, the study found only a minor loss of efficiency. Specifically, in previous studies, 39 g/L of slag was needed to buffer the pH of the acidic wastewaters. To reach similar pH values within the same time span, upscaled trials found a ratio of 43 g/L and 44 g/L when 70 and 90 L are used, respectively. Therefore, when the kinetic conditions are controlled, the technology appears to be scalable to higher volumes. This is an important finding that hopefully promotes further investments in this technology. QC 20220322

Laboratory scale alloying experiments were carried out by the addition of a commercial low carbon ferrochrome (LCFeCr) alloy to 430-grade ferritic stainless steel. The inclusions in FeCr alloys as well as in the steel samples before and after alloy addition were investigated using an electrolytic extraction (EE) technique. The results show that the Ti content decreases after the FeCr alloy addition. MnCr2O4 inclusions from FeCr alloys are transformed into Ti2O3-Cr2O3 based liquid inclusions and Ti2O3-rich solid inclusions. They are formed due to the reactions between MnCr2O4 and either TiN or dissolved Ti, which needs to be further studied. The ratio of Ti/Al in the steel melt has a direct influence on the evolution of the inclusions. The present study aims to contribute for understanding the impurities in FeCr alloys and their effect on the inclusion characteristics for the stainless steel production.

The focus of the study was to define the origin of the inclusions in production-scale electro-slag remelting, (ESR) and electro-slag remelting under a protected pressure controlled atmosphere, (PESR), ingots. The inclusion characteristics in production samples were studied using both polished sample surfaces (two-dimensional (2-D) investigations) and inclusions extracted from steel samples by electrolytic extraction (three-dimensional (3-D) investigations) using SEM in combination with EDS. The results were compared to results from previously reported laboratory-, pilot-, and production-scale trials including electrode, remelted, and conventional ingots. The results show that primary, semi-secondary, and secondary inclusions exist in the remelted ingots. The most probable inclusion to survive from the electrode is a MgO-Al2O3 (spinel). It was also found that the ESR/PESR process slag acts in a similar way to a calcium treatment modification of alumina inclusions. On the whole, the most significant finding is that the overall cleanliness of the electrode including the inclusions in the electrode has an influence on the inclusion content of the ESR and PESR ingots.

Inclusions in steels and alloys are known to lower the resistance to deformation, as well as to lower the mechanical, corrosion and other properties. Studies of inclusions in nickel-based alloys are important since these materials could suffer from corrosion degradation in harsh operational conditions. This, in fact, could lead to a pitting initiation around the inclusions. Two industrial Ni-based alloys (alloy 718 and EP718) were investigated to determine the harmful effects of different inclusions on the corrosion resistance of Ni-based alloys. Specifically, the inclusion characteristics (such as composition, morphology, size, number and location) were determined for inclusions collected on film filters after electrolytic extraction and dissolution of a metal matrix around different inclusions on surfaces of metal samples after electrolytic extraction (EE). It was found that both Ni-based alloys contain various inclusion types: carbides (large size NbTi-C and small multicomponent carbides), nitrides TiNb-N and sulphides (TiNb-S in EP718 alloy). The most harmful effects on the corrosion resistance of metal were detected around sulphides and small carbides containing Mo, W, Cr. Dissolution effects were also observed around large carbides and nitrides, especially around inclusions larger than 10 &micro, m. Moreover, the dissolution of a matrix around inclusions and clusters located on the grain boundaries were found to be 2.1&ndash, 2.7 times larger compared to inclusions found inside of grains of the given alloy samples.

Inclusions in steels and alloys are known as factors that could lower deformation, mechanical, corrosion and other properties. Study of inclusions in nickel based alloys is important since these materials could suffer from corrosion degradation in harsh operational conditions, where inclusions could lead to a pitting initiation. For estimation of a harmful effect of different inclusions on corrosion resistance of Ni-based alloys, inclusion characteristics (such as composition, morphology, size, number and location) on film filter and dissolution of metal matrix around different inclusions on surfaces of metal samples after electrolytic extraction (EE) were investigated in two samples of industrial Ni-based alloys (alloy 718 and EP718). It was found that both Ni-based alloys have various inclusions: carbides (large size NbTi-C and small multicomponent carbides), nitrides TiNb-N and sulfides (TiNb-S in EP718 alloy). The higher harmful effect on corrosion resistance of metal was detected around sulfides and small carbides containing Mo, W, Cr. Dissolution effect was also observed around large carbides and nitrides, especially around inclusions having size more than 10 µm. Moreover, the dissolution of metal matrix around inclusions and clusters located on the grain boundaries is 2.1-2.7 times larger compared to that for those inclusions inside of grains of the given alloy samples.

The characteristics of different shapes of nonmetallic inclusions (NMIs) aredetermined using different methods. In this respect, various shapes of NMIs,including spherical, octahedral, elongated, bar-like, plate-like, polyhedral, andirregular inclusions, are observed in different steels and ferroalloys. The inclu-sions are investigated using three methods: 1) 2D investigations on a polishedcross section (2D method); 2) 3D investigations on afilmfilter after electrolyticextraction andfiltration (EE method); and 3) 3D investigations on a metal surfaceafter electrolytic extraction (MS method). In addition, scanning electron micro-scopy (SEM) with an energy-dispersive spectrometer (EDS) is used for thedetermination of the chemical composition of inclusions. The advantages andlimitations of different methods for investigations of different shaped inclusionsare discussed. The results show that the 2D method is less precise to detectthe morphology, size, and number of inclusions; however, the EE and MSmethods are used to determine a more accurate morphology. Furthermore, theMS method is found to be more advantageous in detecting large-sized inclusions.This study also shows that the results on both thefilmfilter and metal surfaceshould be grouped together to obtain more comprehensive information of theinclusion characteristics. QC 20210511

Nowadays, the existing evaluation methods of chip breakability in industry are based on subjective visual evaluations of the chip formation during cutting or on a chip chart made after the tests. H ...

Today, titanium is often used in steelmaking not only for deoxidation but also for micro-alloying and alloying for a wide range of steel grades. Therefore, many studies are focused on investigation ...

Ferroalloys are one of the most important raw materials widely used in the steelmaking processes. Depending on the cleanliness of used ferroalloys, they can be an inevitable source of impurities a ...

Corrosion rate in different steel grades (including oilfield pipeline steels) is determined by the presence of non-metallic inclusions (NMI) in steels. Specifically, the effect of different inclusions on the quality of steels depends on their characteristics such as size, number, morphology, composition, and physical properties, as well as their location in the steel matrix. Therefore, the optimization and control of NMI in steels are very important today to obtain an improvement of the material properties of the final steel products. It is well known that a Ca-treatment of liquid steels in ladle before casting is an effective method for modification of non-metallic inclusions for improvement of the steel properties. Therefore, the NMI characteristics were evaluated in industrial steel samples of low carbon Ca-treated steel used for production of oil-pipelines. An electrolytic extraction technique was used for extraction of NMI from the steel samples followed by three-dimensional investigations of different inclusions and clusters by using SEM in combination with EDS. Moreover, the number and compositions of corrosion active non-metallic inclusions were estimated in hot rolled steel samples from two different heats. Finally, the corrosion resistance of these steels can be discussed depending on the characteristics of non-metallic inclusions present in the steel.

Recycling of steelmaking slags has well-established applications, such as their use in cement, asphalt, or fertilizer industries. Although in some cases, such as the electric arc furnace (EAF) high-alloyed stainless-steel production, the slag&rsquo, s high metal content prevents its use in such applications. This forces companies to accumulate it as waste. Using concepts such dematerialization, waste management, industrial symbiosis, and circular economy, the article drafts a conceptual framework on the best route to solving the landfilling issue, aiming at a zero-waste process re-design. An experimental part follows, with an investigation of the use of landfill slag as a substitute of limestone for the neutralization of acidic wastewater, produced by the rinsing of steel after the pickling process. Neutralization of acidic wastewater with both lime and slag samples was performed with two different methods. Two out of four slag samples tested proved their possible use, reaching desired pH values compared to lime neutralizations. Moreover, the clean waters resulting from the neutralizations with the use of both lime and slag were tested. In terms of hazardous element concentrations, neutralization with slag yielded similar results to lime. The results of these trials show that slag is a potential substitute of lime for the neutralization of acidic wastewater.

In this study, the composition, size, and number of large non-metallic inclusions (g20μm) are investigated in a commercial refined FeTi70R alloy, which is used for deoxidation and alloying o ...

Evaluation of Agglomeration Mechanisms of Non-metallic Inclusions and Cluster Characteristics Produced by Ti/Al Complex Deoxidation in Fe-10 mass%Ni Alloy

Iron ore pellets undergo mechanical wear during handling, transportation and use in a blast furnace. This results in a loss of valuable raw materials and causes environmental problems in form of du ...

Fly ash and waste lime are solid wastes generated in pulp and paper mills. Due to high CaO contents, these secondary lime materials can be potentially utilized in the steelmaking process to partially replace primary lime. In this study, fly ash and waste lime from Swedish pulp and paper mills were made into briquettes and for the first time utilized as slag formers to replace primary lime in a pilot-scale Argon Oxygen Decarburization (AOD) stainless steelmaking process. The purpose was to evaluate how these CaO-containing materials could affect the AOD process and the steel quality. The results show that the S, P and CaO contents in the fly ash and waste lime are important concerns for metallurgical application. Firstly, due to lower CaO contents (61.5% CaO in fly ash and 90.6% CaO in waste lime versus 95.2% CaO in primary lime), utilization of these secondary lime materials could lead to higher slag amounts in the AOD converter. Secondly, due to higher S and P contents (0.40% S and 0.26% P2O5 in fly ash, 0.11% S and 0.75% P2O5 in waste lime versus 0.08% S and 0.01% P2O5 in primary lime), utilization of these secondary lime materials could increase the S and P contents in the steel. The S content in the steel can be controlled during the reduction and desulfurization stages; however, the P content in the steel increases with an increased use of these secondary lime materials. Thirdly, the metallurgical performance of fly ash and waste lime is as good as primary lime when considering the aspects that: (a) utilization of fly ash and waste lime doesn’t have negative effects on the decarburization stage nor on the reduction stage during the AOD process; and (b) fly ash and waste lime are as efficient desulfurization agents as primary lime. In future industrial applications, the alkali content and the variations of chemical compositions (especially with respect to S, P and CaO) of these secondary lime materials need to be carefully controlled to ensure a sound metallurgical operation.

This study aimed to elucidate the effect of a sulfur addition on the formation and behavior of CaS inclusions in steel melts during a secondary refining process without a Ca-treatment. Samples were taken during production for two different steel grades, namely a low-S steel (S = 0.005%) and a high-S steel (S = 0.055%). Thereafter, the inclusion characteristics were determined using an SEM combined with an EDS. The results show that the CaO content in the inclusions decreased and the CaS content increased after a sulfur addition during an RH process for the high-S steel. Furthermore, CaS-covered inclusions were frequently detected in the high-S steel samples after the S addition. Thermodynamic calculations were also performed to compare the CaS formation behavior in the two steels. The results showed that a CaS phase can thermodynamically be formed in the high-S steel melt even without a Ca-treatment. Also, it was indicated that a CaS phase can be formed in two ways, namely a reaction between Ca and S and a reaction between CaO in inclusions and S. From the viewpoint of interfacial features, inclusions covered by a CaS phase are thought to possess low contact angles to steel melts. Therefore, CaS-covered inclusions tend to remain in a steel melt. According to the results of this study, CaS inclusions can be formed and deteriorate the castability of high-S containing steels even without a Ca-treatment.

The effect of injection of nepheline syenite (NS) together with CaC 2 and C on the iron losses in form of metal droplets in a slag during desulphurization of hot metal is investigated in industrial trials. The characteristics of different metal droplets (such as morphology, number, size and composition) in slags of trials without and with injection of a NS are investigated using SEM. All metal droplets in the slag are classified into three groups according to morphology: Type A-spherical/oval; Type B-spherical/irregular; Type C-irregular. It is found that the addition of NS influences the compositions of hot metal, slag and metal droplets in slag. As a result, the amount (area fraction) and size of metal droplets decreased for Type A and B and increased significantly for Type C droplets present in the slag. The effect of injection of nepheline syenite together with CaC 2 and C on the iron losses in form of metal droplets in a slag during desulphurization of hot metal is investigated in industrial trials. The characteristics and behavior of different metal droplets in slags of trials without and with injection of a nepheline syenite are investigated.

The interest of gaining on-line information related to non-metallic inclusions during the steelmaking process has recently increased due to the development as well as the promising results of the Pulse Distribution Analysis with Optical Emission Spectroscopy method (PDA/OES). Even though, the time from sampling to presented results on inclusions is only about 5-10 minutes, the method has also shown limitations with respect to the determination of some inclusion characteristics.Therefore, a first step was to perform a study on other methods such as the cross-section method (CS) on a polished sample surface, the cross-section after etching method (CSE), the bromine-methanol extraction method (BME), and the electrolytic extraction method (EE). This study focused on the evaluation of these methods with respect to the time consumption for preparation and analysis of a sample, the analyzed volume and the determination of inclusion and cluster characteristics such as size, number, particle size distribution (PSD) and composition. The CS and CSE methods were found to be suitable in the determination of the largest cluster in a sample which can be recommended in order to select proper extraction parameters for further studies. The BME method was considered to be fast with the possibility of analyzing a large volume. However, the used solution is chemically stronger compared to electrolytic extraction solutions, which can affect the results. In most aspects, the EE method was found to be the most stable, reliable and accurate method with some limitations regarding the time aspect.Based on this conclusion, the EE method was selected for a comparative study with the PDA/OES method. Reliably detected size ranges by using the PDA/OES method were defined for two low-alloyed steel grades. These are 2.0-5.7 μm and 1.4-5.7 μm for steel samples taken before and after a Ca-addition during the secondary steelmaking, respectively. Moreover, agreements between the EE and PDA/OES methods were observed in the average size and number of detected inclusions when only inclusions with the size > 2 μm were considered. Also, a theoretical minimum size and a maximum number ofinclusions present in the steel sample, which can be detected by using the PDA/OES method, were estimated.The work continued by successfully applying the EE method to study correlations between inclusions observed in the liquid steel samples and in a clogged nozzle (clogging material). It was found that the average sizes of spherical and non-spherical inclusions observed in the steel corresponded well with those observed in the clogging material. However, there were some differences in the frequencies of these inclusions. This was explained by a possible transformation of the present inclusions due to a reoxidation and a reaction with the nozzle refractory of the steel melt. The results of this study may contribute in the selection of proper process parameters or inclusion characteristics for future studies on the improvement and application of on-line methods.Finally, suggestions on how to present and interpret data obtained by the PDA/OES method during production of stainless steels were given in the present thesis. More specifically, the possibilities of defining operating windows with respect to inclusion composition and the use of a B-factor for Al (the total content of Al in inclusions detected by using the PDA/OES method) during the secondary steelmaking were discussed. In addition, a correlation study between B-factors for Al and numbers of inclusions (dV > 4 μm) obtained by using the PDA/OES method on process samples, and corresponding slivers indices from plate products was performed. The results showed a moderate correlation between these parameters as well as an increase of the slivers index with increased values of the chosen PDA/OES data. This indicates that it could be possible to predict when there is an increased risk of having slivers on the final rolled product at an early stage of the steelmaking process.

The influence of the cerium and silicon contents on the castability of a REM-alloyed stainless steel was investigated by using pilot scale experiments. The trials were carried out with three different silicon concentrations: i) low (LSi; Si

REM-oxide clusters extracted from 253MA stainless steel grade samples from a pilot trial were investigated using a 2%TEA electrolyte. The samples were taken from liquid steel at different holding t ...

Iron losses in slag during an intensive desulfurization of hot metal can reach 0.6-1.1% from the total amount of processed hot metal. The characteristics of different metal droplets (such as morpho ...

The interest of gaining on-line information related to non-metallic inclusions during the steelmaking process has recently increased due to the development as well as the promising results of the Pulse Distribution Analysis with Optical Emission Spectroscopy method (PDA/OES). Even though, the time from sampling to presented results on inclusions is only about 5-10 minutes, the method has also shown limitations with respect to the determination of some inclusion characteristics.Therefore, a first step was to perform a study on other methods such as the cross-section method (CS) on a polished sample surface, the cross-section after etching method (CSE), the bromine-methanol extraction method (BME), and the electrolytic extraction method (EE). This study focused on the evaluation of these methods with respect to the time consumption for preparation and analysis of a sample, the analyzed volume and the determination of inclusion and cluster characteristics such as size, number, particle size distribution (PSD) and composition. The CS and CSE methods were found to be suitable in the determination of the largest cluster in a sample which can be recommended in order to select proper extraction parameters for further studies. The BME method was considered to be fast with the possibility of analyzing a large volume. However, the used solution is chemically stronger compared to electrolytic extraction solutions, which can affect the results. In most aspects, the EE method was found to be the most stable, reliable and accurate method with some limitations regarding the time aspect.Based on this conclusion, the EE method was selected for a comparative study with the PDA/OES method. Reliably detected size ranges by using the PDA/OES method were defined for two low-alloyed steel grades. These are 2.0-5.7 μm and 1.4-5.7 μm for steel samples taken before and after a Ca-addition during the secondary steelmaking, respectively. Moreover, agreements between the EE and PDA/OES methods were observed in the average size and number of detected inclusions when only inclusions with the size > 2 μm were considered. Also, a theoretical minimum size and a maximum number ofinclusions present in the steel sample, which can be detected by using the PDA/OES method, were estimated.The work continued by successfully applying the EE method to study correlations between inclusions observed in the liquid steel samples and in a clogged nozzle (clogging material). It was found that the average sizes of spherical and non-spherical inclusions observed in the steel corresponded well with those observed in the clogging material. However, there were some differences in the frequencies of these inclusions. This was explained by a possible transformation of the present inclusions due to a reoxidation and a reaction with the nozzle refractory of the steel melt. The results of this study may contribute in the selection of proper process parameters or inclusion characteristics for future studies on the improvement and application of on-line methods.Finally, suggestions on how to present and interpret data obtained by the PDA/OES method during production of stainless steels were given in the present thesis. More specifically, the possibilities of defining operating windows with respect to inclusion composition and the use of a B-factor for Al (the total content of Al in inclusions detected by using the PDA/OES method) during the secondary steelmaking were discussed. In addition, a correlation study between B-factors for Al and numbers of inclusions (dV > 4 μm) obtained by using the PDA/OES method on process samples, and corresponding slivers indices from plate products was performed. The results showed a moderate correlation between these parameters as well as an increase of the slivers index with increased values of the chosen PDA/OES data. This indicates that it could be possible to predict when there is an increased risk of having slivers on the final rolled product at an early stage of the steelmaking process.

Nowadays, an effective application of energy required for stainless steel production in the electric arc furnace (EAF) by a slag foaming practice and recycling of waste products play two of the most significant roles for a sustainable steel production. In this study, briquettes were used to obtain a combined slag foaming and waste product reduction in the EAF process. Briquettes with different densities produced partly from waste products were tested in an industrial scale to study slag foaming in the EAF process during stainless steel production. The slag foaming tendency was determined based on visual estimations of slag foaming, evaluations of the slag density before and after addition of different briquettes, and by calculating a foaming index. The influence of the main parameters of briquettes (composition, density) and the furnace slag (composition, basicity, and, etc.) on slag foaming was studied. It was found that both heavy and light briquettes can be used for slag foaming. The heavy briquettes, with FeCr, produce about half the amount of gas compared to the light briquettes, without FeCr. The main part of the gas, >80%, was generated during the first 2–3 min, Moreover, the highest slag foaming rate was obtained for slags with a basicity in the range of 1.31–1.49.

Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si–Cr–O and Cr–O oxides as well as intermetallic Cr–Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr–Mn–S, Cr–...

An efficient stainless steel making industry is defined by different factors such as an efficient utilisation of energy in the Electric Arc Furnace (EAF). This requires a good by slag foaming practice and an utilisation of waste products from own production facilities. In the following study, briquettes applied for a combined slag foaming and waste product recycling in the EAF were investigated in both laboratory and industrial scales. More specifically, briquettes were characterised and used for slag foaming in the EAF. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were defined and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500°C in an argon atmosphere in order to characterise the products (metal, slag and gas) produced by briquettes. The calculations were also compared to experimental data. Thereafter, briquettes with different densities and pet-coke addition were tested on an industrial scale to study slag foaming in the EAF process during a stainless steel production. The slag foaming tendencies were determined based on visual estimations of slag foaming, determinations of the slag density before and after additions of different briquettes, and by calculating a foaming index. Moreover, the influence of the main parameters of the briquettes (composition, density) and the furnace slag (composition, basicity and etc.) on slag foaming was studied. Investigation of briquettes made on laboratory and industrial scales provided the following main results: the density of briquettes can successfully be verified, briquettes have different mechanical properties depending on the materials used for production of briquettes, briquettes yield different amounts of metal and gas. Moreover, it was found that the heavy briquettes (containing FeCr) produce about half the amount of gas compared to the light briquettes (without FeCr). The main part of the gas was generated during the first 2-3 min. Also, the valuable metals can be recovered from briquettes; recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilisation of carbon. In addition, it was found that both heavy and light briquettes can be used for slag foaming. The highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49.

Clogging of high Si-containing stainless steel grades was studied by metallographic examinations of steel samples from clogged and non-clogged heats as well as by thermodynamic modeling using Thermo-Calc and FactSage. Morphology, composition, number and size of inclusions and clusters in the steel samples were determined on a polished surface of the steel samples by using a scanning electron microscope equipped with energy-dispersive X-ray spectrometer. The results showed that the content of Al in ferroalloys added during ladle treatment should be controlled to avoid a formation of spinel MgO-Al2O3 inclusions in liquid steel and a resulting clogging during casting. The thermodynamic calculations showed that the Al content in a melt during ladle treatment and casting should not be larger than 0.003% to obtain < 1% of MgO-Al2O3 inclusions in the liquid steel for a 1.9% silicon content. Moreover, calculations also showed that if the Si content increased from 1.9% (non-clogging heats) to 2.65% (clogging heats), the number of MgO-Al2O3 inclusions decreased slightly. Moreover, it was found that an increased amount of FeSi additions for correction of Si content in the melt increase the Al content. As a result, the number of spinels and clusters increases, which is the primary cause for clogging during casting of these steel grades.