Composition Of Nonmetallic Inclusions Research Articles

The effect of complex extra-furnace treatment of metal melts on the formation of non-metallic inclusions in large-sized ingots

Abstract The article presents the results of studying non-metallic inclusions (NI) after extra-furnace treatment of the 13Cr9Mo2Co1NiVNbNB steel melt to produce large-sized ingots. The objects of the study were laboratory samples (the first batch), and samples obtained after melting in industrial furnace, followed by modification and double vacuuming (the second batch). Previously, using the Fact Sage software, modeling of the NI formation processes was carried out. The data were obtained on the possible NI composition and amount in this steel. The composition, the contamination index, parameters of NI in samples have been studied. It was established that in the samples of the first batch, the main part of the NI consisted of chromium- and manganese-containing oxides, which occupy more than 94% of the total area of the NI. In the samples of the second batch, the main part of the NI was represented by aluminum containing systems. It was shown that the average size of NI in the samples after extra-furnace treatment differs slightly (5%–12%), however, the contamination index in industrial samples after vacuum treatment and especially after modification and repeated vacuum treatment was reduced by more than 10 times. The results obtained allow to recommend vacuum treatment and complex modification with calcium and boron as measures to prevent the formation of NI and to improve metallurgical quality when smelting large ingots using complex alloy steels.

METALLOGRAPHIC ANALYSIS OF NON-METALLIC INCLUSIONS IN SEMI-KILLED STEEL (GRADE 25G2S) DEOXIDIZED WITH A COMPLEX ALLOY Fe-Si-Mn-Al

This study presents a metallographic analysis of non-metallic inclusions in steel samples obtained from six different heats of the oxygen converter shop at JSC «Qarmet» and under laboratory conditions at the Karaganda Industrial University. The investigation focused on semi-killed steel samples deoxidized using traditional technology under industrial conditions and with a complex alloy containing Fe-Si-Mn-Al under laboratory conditions, aiming to identify the types and assess the level of contamination by non-metallic inclusions. The results revealed the presence of various types of non-metallic inclusions, such as corundum, chromite spinel, chromium oxides, as well as titanium nitrides and carbonitrides. The degree of contamination by non-metallic inclusions ranged from 2 to 3 points. The analysis showed that the use of a complex Fe-Si-Mn-Al alloy instead of traditional deoxidizers can affect the quantitative and qualitative composition of non-metallic inclusions. It was established that the complex alloy promotes the formation of more stable inclusion phases, which can positively impact the mechanical properties of the steel. It was also found that different production technologies and the use of deoxidizers can significantly influence the quantity and types of non-metallic inclusions, requiring further study and optimization of technological processes. Therefore, the results of this study can be valuable for metallurgical enterprises in selecting optimal steel deoxidation methods and improving steel quality, as well as for further scientific research in the fields of metallurgy and materials science.

The Analysis of the Effect of Mischmetal Addition on the Formation of Non-Metallic Inclusions in Liquid Steel

The study focuses on the effect of rare earth elements (REM) in mischmetal on the morphology and chemical composition of non-metallic inclusions in pre-oxidised steel. Calculations were carried out using the WYK_STAL computer program according to two calculation models, considering/ignoring the sulphur partition coefficient at the liquid steel-liquid slag interfacial boundary. It was found that the chemical composition of the resulting precipitates is a consequence of the order in which deoxidising additives were admixed. Simulations confirmed the presence of Ce oxides and sulphides. This was also confirmed by the analysis of samples taken from the steel ingot after laboratory melting. Non-metallic inclusions Ce2O3 and CeS, and the complex of precipitates: La2O3-Ce2O3 was also identified in the steel. Introduction of mischmetal in the final stage refining is the most effective method. Therefore, the oxygen content is reduced below 0.001%, and the sulphfur content can be reduced to 0.004%.

Three-Dimensional Imaging of Non-metallic Inclusions in Steel Using Ionoluminescence

Obtaining information on the morphology, size, distribution, and chemical composition of non-metallic inclusions in steel helps control the steel production process and the quality of the steel products. Two-dimensional analysis is commonly used to acquire this information; however, more accurate data can be obtained through three-dimensional analysis, leading to a better control of the quality of steel products and their production process. Currently, several techniques are proposed for the three-dimensional analysis of non-metallic inclusions; however, they are time consuming. Herein, the author presented a method to rapidly obtain three-dimensional images of non-metallic inclusions in steel using ionoluminescence (IL). A three-dimensional image of MgO·Al2O3 spinel inclusions was constructed based on two-dimensional IL images obtained every 10 min during argon–ion bombardment. The proposed IL imaging can cover an oval-shaped area of 1.17 mm × 0.26 mm on the semi-major and in the semi-minor axes, respectively, at a single measurement. Three-dimension images of MgO·Al2O3 spinel inclusions with sizes more than 20 μm can be obtained within 4 hours. Therefore, the IL imaging proposed here can provide a precise and rapid account of the effects of non-metallic inclusions on steel products and the steel production process.

Темір-көміртекті қорытпалардағы негізгі элементтермен және металл емес қосындылармен сирек жер металдарының әрекеттесуін зерттеу

The proposed article is devoted to the study of the interaction of rare earth metals with basic elements and non-metallic compounds in iron-carbon alloys. The article discusses the method of modifying iron-carbon alloys with rare-earth metals, the nature and mechanisms of interaction of alloy components. The influence of rare earth metals and non-metallic mixtures on the properties of the material is analyzed. The qualitative composition of nonmetallic inclusions formed in steel grades 09G2FB and 17G1SU modified with yttrium and without the introduction of yttrium-containing material (SIITMISH-1) was studied by the X-ray spectral method. With the formation of complex compounds by the introduction of rare earth metal, as a result of which the alloy is purified from non-metallic compounds. Research in this area makes it possible to develop new materials with improved characteristics and optimize the processes of their production and processing

Study of the Microstructure of 08PS Steel Deoxidized with Standard Ferroalloys and Prospects for Replacing Them with Complex Deoxidants

The annotation This research work is devoted to the study of the microstructure of 08PS steel deoxidized using standard ferroalloys and the prospect of replacing them with complex deoxidifiers. The purpose of the study was to determine the impact of the deoxidation process on the microstructure of steel and to assess the replacement with complex deoxidants. Research methods included metallographic analysis of steel samples and energy dispersion analysis (EDX) to determine the composition of non-metallic inclusions. The analysis was carried out on steel samples before and after deoxidation, the microstructure, the size of non-metallic inclusions and their composition were studied.

Revealing the kinetics of non-metallic inclusion reactions in steel using in-situ high temperature environmental scanning electron microscopy

The kinetics of solid-state reactions involving non-metallic inclusions (NMIs) in steel is a topic of growing interest due to the need to understand the effects of heat treatments on NMI composition and stability. In this study, a High Temperature Environmental Scanning Electron Microscope (HT-ESEM) is utilized to conduct in-situ observations of various types of NMIs, including calcium aluminate complex, CaS, MgAl2O4-CaS, MnS, and TiN, in steels at temperatures of 800 °C and 900 °C for different holding times. The observed morphological variations in the NMIs indicate a decrease in the fractions of CaS and MnS, promoting void formation and ferrite–austenite phase transformation. To estimate the NMI reactions with the residual atmosphere in the sample chamber during experiments, HT-ESEM-driven thermodynamic calculations have been performed using FactSage 8.2 software. These calculations provide valuable insights into the interpretation of the experimental data, facilitating a better understanding of the complex NMI reactions in steel.

TOTAL OXYGEN CONTENT IN LIQUID STEEL AS A CRITERION FOR EVALUATING NONMETALLIC INCLUSIONS IN PIPE STEELS

A statistical analysis of the total oxygen content in samples of pipe steels at the stage of continuous casting at the continuous-casting machines of the casting and rolling complex of JSC “Vyksa Metallurgical Plant” was carried out. The microstructures of rolled samples were studied, and the chemical composition of non-metallic inclusions was determined by X-ray spectral microanalysis. A laboratory analysis of liquid steel samples and hot-rolled steel products of the casting and rolling complex was carried out using the method of reduction melting in an inert gas flow. Relationships have been constructed between the duration of metal presence in a steel-pouring ladle and the magnesium content in non-metallic inclusions, as well as between the average score of non-metallic inclusions in rolled metal and the total oxygen content in liquid steel at the stage of continuous steel casting.

Calcium-Treated Steel Cleanliness Prediction Using High-Dimensional Steelmaking Process Data

Control of calcium treatment in steel is challenging due to the reactivity of Ca and difficulty of measuring total oxygen of steel in-process to make actionable decisions. In this work, a method combining statistics and process engineering are developed using partial least squares regression (PLS) to predict non-metallic inclusion content (oxides and CaS) and composition at the end of ladle treatment and in the tundish using extensive process data and SEM/EDS-based non-metallic inclusion analysis. Total oxygen at the end of the ladle treatment can be predicted to an accuracy of 7 ppm, and the Mg/(Mg+Al) ratio in inclusions to an accuracy of 3at% providing enough data to recommend Ca addition based on a thermodynamic calculation for the Ca liquid window. Alternatively, the model can predict total inclusion fraction to 20 ppm accuracy, and accurately predict average CaS content and Ca/Al ratio of inclusions in the tundish. Model interpretability is hindered by high dimensionality and multicollinearity of the data. Non-metallic inclusion compositions correspond to the expected composition at the onset of CaS formation based on steel composition.

Исследование циклической трещиностойкости стали литых несущих деталей грузовых вагонов

Purpose: Carrying out complex experimental studies of cyclic crack resistance of molten steel which is used for load-bearing parts of freight wagon running systems with kinetic diagram building for fatigue failure. Methods: Method of mechanical testing of molten steel samples under cyclic loading conditions was applied, the method makes it possible to obtain quantitative estimates of stuff ability to resist fatigue failure on the stage of fatigue crack development (testing on cyclic crack resistance). To study the surface of fatigue failure, relief micrographic analysis was used. To study molten steel elemental composition and the mechanisms of fatigue crack development, X-ray micro-spectral analysis was used on fatigue failure various stages. Results: The results of the research of cyclic crack resistance of 20 GL molten steel, which is used for load-bearing parts of freight cars, are presented. Fatigue failure kinetic diagram has been built, detailed micrographic analysis of fatigue failure surface has been carried out and elemental composition of non-metallic inclusions has been studied. Practical significance: Based on the research results, it is possible to assess the performance of 20 GL steel with cracks and to predict survivability. The results obtained make it possible to improve the methods of resource projection of molten bearing parts for freight wagon running systems in order to increase their operational reliability. The research results are used by enterprises - manufacturers of molten parts to control technology stability and to improve product quality.

Analysis of Ancient Slag Inclusion-Metal Systems as a Method to Disclose Processing Thermo-chemical Parameters: The Case Study of a Medieval Lombard Steel Bar from Northern Italy

An archaeometallurgical characterization of a VI to VII century Lombard steel bar from Ponte di Val Gabbia I site (northern Italy) was performed to reconstruct its manufacturing process and extract processing thermochemical parameters (i.e., temperature and oxygen chemical potential) from the slag inclusion-metal systems. Metallographic observations by optical microscopy and Vickers microhardness measurements indicated that the steel bar was forged from a heterogeneous steel lump, most probably an iron bloom, which was cooled in the air after the forging process. The chemical composition of non-metallic inclusions was determined by scanning electron microscopy coupled with X-ray dispersive spectroscopy. A multivariate statistical analysis of the smelting-derived non-metallic inclusions chemistry allowed to conclude that the steel bar was obtained by the direct or bloomery method. Under the hypothesis of local near-equilibrium conditions for the slag inclusion-metal systems, a thermodynamic-based strategy was adopted to estimate the firing conditions in the bloomery furnace in terms of both temperature and oxygen chemical potential of the reducing gas atmosphere. In particular, the computed temperatures are in the range of 1003 °C to 1171 °C, whereas the values of oxygen chemical potential vary between − 447.47 and − 385.79 kJ/mol.

On the comparative inclusion analysis in steels: Spark-DAT, ASCAT and optical microscopy

In the last decades, the control of amount, size, morphology, and chemical composition of non-metallic inclusions in steel has been investigated, particularly at the stage of steel refining, where endogenous and exogenous inclusions can affect the castability and the mechanical properties of the material, thus affecting the quality and performance of the process and final product. In this way, identifying the origin of inclusions and the steelmaking stages where they are formed is essential. The purpose of this study was to compare the results of methodologies for inclusions characterization and analysis using Spark-DAT, ASCAT and optical microscope systems, aiming to validate these systems for inclusions amount and size measuring control during steelmaking. Samplings of ultra-low (ULC) and medium (MC) carbon steels were carried out and both steels killed with silicon and/or aluminum. The MC steel presented higher concentration of inclusions with size in a range between 1 and 5 μm and this behavior is associated with calcium treatment. The total amount of inclusions per square area, presents significant difference between the measurement systems, however correlations could be noted. Spark-DAT and ASCAT showed better correlations. The study also showed the predominancy of oxide inclusions type. For sulfide inclusions there are a discrepancy between Spark-DAT and ASCAT, so that inclusions such as CaS and MnS are revealed but only ASCAT system showed the TiS inclusion type.

Composition of non-metallic inclusions and microstructure of electric arc coating formed using the flux-cored wire of Fe – C – Si – Mn – Сr – Ni – Mo system

The article considers the study of composition of the non-metallic inclusions and microstructure of the electric arc coating using the flux-cored wire of Fe – C – Si – Mn – Cr – Ni – Mo system. Formation of the electric arc coating was carried out using the ASAW-1250 automatic arc welding machine by the investigated wire. In order to influence the level of contamination of the deposited metal with non-metallic oxide inclusions, aluminum gas purification dust was introduced into the flux-cored wire (instead of amorphous carbon). Composition of the electric arc coating was determined using XRF-1800 spectrometer. Microstructure of the electric arc coatings was studied by optical microscopy. The phase and elemental compositions were studied using scanning electron microscopy on MIRA 3 LMH instrument. Non-metallic inclusions in the electric arc coating consist of oxides of silicon, fluorine, calcium, aluminum and magnesium oxides. The darker component in the inclusion, which looks like rectilinear crystals directed from the surface deep into the inclusion, has a similar phase composition, but differs somewhat in the content of chemical elements. A small dark component of a rounded shape (aluminum and magnesium oxides) is observed in the inclusion. Traces of sulfur are highlighted along the contour of the globules. Metallographic analysis of the deposited surface showed that the microstructure of the deposited layer is a coarse-needle martensite. The structure is uniform, has a dendritic (columnar) structure characteristic for cast metal. The results of the conducted investigations allow measures to be developed to reduce the content of non-metallic inclusions containing elements of fluorine, sodium and aluminum, which in turn may adversely affect the physical and mechanical properties of the deposited layer, for example, by using refining additives to reduce the contamination of the deposited layer with non-metallic inclusions.

Composition of Non-Metallic Inclusions and Microstructure of Electric Arc Coating Formed Using the Flux-Cored Wire of Fe–C–Si–Mn–Cr–Mo System

Composition of Non-Metallic Inclusions and Microstructure of Electric Arc Coating Formed Using the Flux-Cored Wire of Fe–C–Si–Mn–Cr–Mo System

Development of Self-Shielded Flux-Cored Wires for Arc Welding of Low-Alloy Steels

Current aspects of the developing of modern self-shielding flux-cored wires composition for arc welding of low-alloyed steels are considered. Advantages and disadvantages of flux-cored wires of carbonate-fluorite, oxide and oxide-fluoride types of are shown in comparison. The effectiveness of gas shielding of molten metal at welding with self-shielding flux-cored wires of carbonate-fluorite type is analyzed considering the thermal properties of their cores. It is shown that to improve reliability of gas shielding at welding using the wires of this type it is important not only to ensure generation of sufficiently large volume of shielding gases at thermal destruction of the wire core, but also to control this process, providing gas evolution at all stages of heating and melting of the wire. The results of complex thermal analysis of the wire core mixtures containing, for example, lithium carbonate show substantially large heat losses for heating and melting of the wire core, which are accompanied by the development of energy-intensive processes of thermal destruction of core components. It is shown that the limitation of lithium carbonate content in the wire at the level of not more than 2 wt. % allows not only to preserve welding arc burning stability at the acceptable level but also to provide effective gas shielding of molten metal and easy separation of slag crust. The control of thermochemical reactions in the core is achieved by selection of its proper composition to ensure favorable melting of flux-cored wire and electrode metal transfer to the welding pool. Results of metallographic examinations of distribution and composition of non-metallic inclusions in metal of the welds made with wires of the oxide and oxide-fluoride types are presented. Main properties of the developed self-shielding flux-cored wires and recommendations on welding are given in conjunction with prospective fields of their application.

On the Chemical Composition of Non-Metallic Inclusions in Ultra-Clean Gear Steels

Abstract Fisheye failures due to non-metallic inclusions can lead to the reduced endurance fatigue limit of case-hardened, shot-peened gears. Various approaches for preventing crack initiation at non-metallic inclusions are conceivable. As one approach, steel manufacturers have invested much effort in the steelmaking process to produce ultra-clean gear steels. Such ultra-clean gear steels were investigated in a gear research project. For each steel batch, different measures were taken during steel production to avoid or bind off non-metallic inclusions in order to reduce or even suppress the harmful effect of the non-metallic inclusions. However, the influence of the measures taken on the chemical composition of non-metallic inclusions in such ultra-clean gear steels is not investigated in the gear industry in detail so far. Therefore, in the framework of this publication, the chemical composition of non-metallic inclusions in ultra-clean gear steels is investigated. Furthermore, a comparison of the chemical analysis with the crack-initiating inclusions from the experimental investigations is performed.

PROPERTIES OF AUSTENITE STAINLESS STEEL MICROALLOYED WITH TELLURIUM AND ZIRCONIUM

Stainless steel X8CrNiS18-9 (standard EN 10088-3: 2005) is the most commonly used austenitic stainless steel due to its good machinability. This steel has high mechanical and working properties thanks to complex alloying, primarily with the elements such as chromium and nickel. The content of sulfur present in the steel from 0.15 to 0.35% improves machinability. Microalloying with tellurium and zirconium (individually and in combination) in most cases leads to improved properties of this stainless steel, compared to melt without alloying additives, e.g. the melt microalloyed with tellurium and especially melt microalloyed with zirconium and tellurium has significantly better machinability compared to the melt without alloying elements. The addition of sulfur, which is the cheapest available additive for free machining, will impair not only the transverse strength and toughness but also the corrosion resistance. However, while sulfur improves machinability at the same time decreases the mechanical properties, particularly toughness. This work aims to test the machinability, corrosion resistance, and mechanical properties of the mentioned steel, as well as the chemical composition of non-metallic inclusions.

Compositional modification of nonmetallic inclusions in bloomery iron during post‐smelting treatments and its implication

AbstractThe chemical composition of nonmetallic inclusions in finished iron artifacts often holds key information on the smelting and post‐smelting processes applied during their production. This possibility was tested with special iron objects deemed product intermediaries from a royal tomb constructed at Gyongju, the former capital of the Silla state during the Korean Three Kingdoms period (c. 300–668 ce). Metallographic examination identified two distinct groups of inclusions with features unique to slags derived from smelting in (a) bloomery furnaces and (b) blast furnaces. Clear evidence was also noted that type ‘a’ inclusions, when subjected to an environment of high carbon activity as in a carburization process, underwent a significant change in chemical composition and microstructure to emulate the other type. This observation is expected to remove significant ambiguities encountered in connecting slag compositions to pertinent engineering processes.

EVALUATION OF THE EFFICIENCY OF USING SK30 WIRE IN STEEL PROCESSING AT THE LADLE FURNACE PLANT

The paper presents studies showing the effectiveness of the use of wire with SiCa filler in the out-of-furnace processing of steels. The efficiency of use was evaluated by calculating the contamination with non-metallic inclusions, as well as by determining the phase composition of non-metallic inclusions at the stages of out-of-furnace processing and casting. (installation bucket furnace→vacuum cleaner→continuous casting). The study found that the adjustment of the content of aluminum before casting leads to the formation of refractory inclusions of corundum - (AlO), spinels - (AlO·MgO), which are deposited on the walls of the steel filling path and worsen the spillability of steel. The use of SK30prov with SiCa filler at the final stages of extra-furnace processing (after the introduction of aluminum), leads to the modification of refractory inclusions in low-melting calcium aluminates of the type (CaO·AlO). The presence of low-melting inclusions is more preferable, since this type of inclusions is not deposited on the walls of the filling cup and does not have a negative effect on the contamination of the continuously cast billet and products obtained from them with inclusions.

Experience of application of calcium-containing cored wire with various fillers at steel ladle treatment

Treatment of mass production steels by cored calcium-containing wires is widely spread all over the world. Injection of several tens of gram of calcium per 1 t of the treated steel enables significantly improve its cast ability, increase the yield of CC billet, decrease rejection of rolled products by surface and internal defects, improve corrosion properties of steel and have similar effects. At the same time application of the technological method requires accurate forecasting of the purpose process conditions, strict following the technology parameters, application of quality injection equipment, as well as application of best calcium-containing cored wires. Taking into consideration, that the role of the filler in the cored wires is not discussed widely, the purpose of the work was summarizing of the experience of application of various calcium-containing materials. Mechanisms of calcium influence on steel quality considered. It was shown that it is possible to control not only chemical composition but also phase composition of nonmetallic inclusions by variation of calcium concentration in steel melt. Among others, liquid inclusions based on calcium aluminates which have high speed of surfacing, will be formed, thus ensuring deep steel refining for nonmetallic inclusions within a short time. Having high sulphur affinity, at the stage of continuous casting calcium forms sulfide and oxide-sulfide nonmetallic inclusions of micron and submicron size, uniformly distributed in the steel volume, which improves the structure of center zone of the continuously casted billet and that of the rolled product. It was shown that calcium-containing filler of a cored wire plays an important role in ensuring high and stable result. It was established based on the probes from tundish that the average recovery of fillers of electrolytic calcium is higher comparing with other fillers. Analysis of frequency distribution of the calcium recovery value showed that to ensure a guaranteed minimal content of calcium of 12 ppm at a CCM, it is required to inject aluminothermic calcium in the amount of 4.5 times bigger comparing with electrolytic calcium and ferrocalcium – 6 times bigger. Analysis of cast ability of steel treated by cored wires showed that to ensure a stable cast ability it is enough to add 55 grams of electrolytic calcium per 1 t of steel, at that addition of 83 grams of aluminothermic calcium does not ensure a stable casting from heat to heat. A dependence of rolled products rejection indices on calcium content in steel was noted, which indicated of a possibility of further increase of economic efficiency of technologies of steel mass production due to development of steel treatment by calcium.