Formation Of Non-metallic Inclusions Research Articles

Structure and properties of 17G1S-U low-carbon pipe steel microalloyed by boron

The results of analysis of the influence of boron microalloying on structure and properties of 17G1S-U pipe steel are given in the paper. Studies of metal structure were performed by electron microscopy and local X-ray spectral analysis. It has been established that metal containing 0.006 % of boron is characterized by an increased volume concentration to 0.029 % of oxide (OS) and oxysulfide (OSB) inclusions, whose content in metal without boron reaches 0.006 %. Separate sulphide inclusions (CB), whose concentration does not exceed 0.004 % against 0.029 % in a metal without boron, containing 0.01 % S is practically absent in the metal with boron containing 0.003 % S. The microalloying of pipe steel by boron has ensured the preferential formation of small nonmetallic inclusions, evenly distributed in the volume of metal. The proportion of nonmetallic inclusions with size less than 2 (rm is 76.1 %, whereas in steel without boron it is only 58.5 %. In this case, large nonmetallic inclusions of more than 10 rm are practically absent in the sample with boron. Their share does not exceed 0.6 %, which is 22 times less than their amount in the sample without boron. The structure of the sample without boron consists mainly of ferrite and a small amount of perlite, and the sample with boron is represented by a dispersed ferritic-bainitic structure. Increasing the microhardness of both ferrite and pearlite 80 and 100 HV10, respectively, is observed by adding boron to steel. The mechanical properties of 10 mm hot rolled metal from boron-containing 17G1S-U pipe steel are characterized by increased strength properties with preservation of plastic characteristics, due to the formation of predominantly small nonmetallic inclusions and a finely dispersed ferritic-bainitic structure. The absolute values of the yield stress and the time resistance of pipe steel containing in mass %: 0.006 B and 0.003 S are achieved without heat treatment at 585 and 685 MPa, respectively, and meet the X80 strength class, while retaining sufficiently high plastic characteristics. The pipe steel without boron containing 0.01 % of S belongs to the X70 strength class and is characterized by tensile strength lowered to 540 and 610 MPa and a temporary resistance, respectively.

Understanding the Role of Inclusions on the Dynamic Fracture Toughness of High Strength Lightweight FeMnAl Steels

High manganese lightweight steel alloys in the Fe–Mn–Al–C system are promising alternatives to quenched and tempered Cr and Mo steels for transportation and military applications. The understanding of nonmetallic inclusion formation and their effect on the mechanical properties is of extreme importance for further alloy development. Sharp and brittle AlN forms prior to the liquidus and has been shown to decrease notch toughness. Controlled additions of sulfur may promote soft and globular MnS that precipitates around AlN during solidification, thus mitigating their detrimental effect. The effect of controlled sulfur additions from 0.004 to 0.042%S was studied in a Fe–30%Mn–9%Al–1%Si–(0.9–1.2)%C–0.5%Mo steel. The main inclusions observed were AlN, MnS, and AlN-cored MnS. Charpy impact toughness was evaluated in the solution treated condition and in specimens aged to 329–340 HBN. Toughness is a function of the overall inclusion population. In aged specimens, same was true only for steels with 0.9% carbon; above 1%C the toughness was below 15 J for any sulfur content.

Analysis of Non-metallic Inclusions in Continuously Cast Low-Carbon Steel

In the present research, the physics and chemistry tests were conducted, and microstructural analyses were made on the cracked regions of the bar after cold forging by using a SUPRA 35 scanning electron microscope (SEM) equipped with a Oxford energy dispersive spectrometry (EDS) microanalysis. The formation of nonmetallic inclusions during metallurgical process is investigated. The results have shown that the internal defects such as shrinkage porosity and square segregation, etc do not result in cracking phenomenon occurring during cold forging. Nonmetallic inclusions lead to significant stress concentration. The presence of them in continuously cast low-carbon cold forging steel is the basic reason for the cracks. Some of film non-metallic inclusions consisted of MnS and CaS. They are related to the desulphurization of hot metal. A lot of film non-metallic inclusions are mainly composed of magnesia alumina spinel (MgO·A12O3). Magnesia alumina spinel (MgO·A12O3) is considered to be from the tundish lining collapse, which results in exogenous inclusions. It is necessary for low-carbon cold forging steel during continuous casting to strengthen the tundish quality.

Free-Cutting Cr–Ni–Mo Steel

The paper presents theoretical and practical study of formation of non-metallic inclusions in a medium-carbon free-cutting structural steel. FactSage software package was used for thermodynamic modelling of inclusion behaviour. Formation temperature and the amount of aluminium oxides, boron nitrides, manganese sulphides and aluminium nitrides were calculated. Inclusions in the steel form in the sequence Al2O3 > BN > MnS > AlN. The object of practical research was a cast billet of A38KhGMAR grade steel. It was melted in a laboratory induction furnace; boron and nitrogen were introduced after deoxidation of the melt with primary aluminium. Quality analysis included determination of chemical composition, macro-and microstructure, type and shape of non-metallic inclusions. Fine and uniformly distributed boron nitride inclusions were obtained throughout the metal matrix; their distribution was studied both qualitatively and quantitatively. Beside isolated particles, boron nitrides are also presented as a component of complex inclusions with manganese sulphides. Inclusion morphology is mostly spherical. The size of BN inclusions varies from 0.41 to 7.23 μm.

Formation of Non-metallic Inclusions of Si-killed Stainless Steel during GOR Refining Process

AbstractThe formation mechanism of inclusions in Si-killed 304 stainless steel was studied by industrial experiments during GOR refining process and thermodynamic calculations. A lager number of CaO-SiO2-MgO-Al2O3-MnO-CrOx liquid spherical inclusions with different size (from 1 μm to 22 μm) had been found after deoxidization of FeSi alloy in 10 minutes. The calculation result of FactSage 6.3 software assisted in confirming that the inclusions in size of less than 5 μm that had less than 30 % CaO mainly came from the deoxidation of FeSi alloy with Ca and Al. The inclusions in size of more than 5 μm that had more than 30 % CaO mainly came from the modification of involved slag droplets through the oxidation of Si and Al and the collision with deoxidation-type inclusions, and the degree of change was bigger for smaller inclusions. The MgO in slag and refractory was reduced by Si and Al in steel, which leaded to the unceasingly increase of Mg content in steel. Subsequently, SiO2, MnO and CrOx in inclusion were reduced by Mg, which resulted in the increase of MgO content in inclusion and the degree of increase of MgO content was greater for the larger size of inclusions.

Prediction of Nonmetallic Inclusion Composition and Amount During Low-Alloy Pipe Steel Production

Thermodynamic modeling is provided for nonmetallic inclusion formation during extra-furnace treatment and solidification of low-alloy low-carbon steels intended for use in corrosion-active media. Relationships are established for the effect on inclusion composition of alloying element additives, a periclase lining, calcium-containing materials, and presence of sulfur within a melt. Conditions are determined for a reduction in the amount of corrosion-active nonmetallic inclusions.

Calculation model of formation of nonmetallic inclusions of multilayer morphology in weld metal

Calculation model of formation of nonmetallic inclusions of multilayer morphology in weld metal

Расчетная модель формирования неметаллических включений многослойной морфологии в металле сварного шва

Расчетная модель формирования неметаллических включений многослойной морфологии в металле сварного шва

КЛАССИФИКАЦИЯ СПЛАВОВ СИЛИКОКАЛЬЦИЙБАРИЯ И ИХ ПРИМЕНЕНИЕ ДЛЯ КОВШЕВОЙ ОБРАБОТКИ СТАЛИ

The paper presents the results of the investigation of of silicocalcium-barium alloys for the determination of primary, intermediate, eutectic and base phases in them, and their effect on steel during its out-of-furnace treatment. For the first time, a polygonal diagram of the state of the Si–Ca–Ba system has been constructed, which makes it possible to systematically classify silicocalcium-barium alloys. The mechanism of the formation of primary nonmetallic inclusions in the deoxidization of steel with barium alloys with the formation of silicate or oxide of Ca-Ba is presented and proposed a mechanism for their modification into globular eutectic composition such as Rankinite A comparative analysis of the efficiency of deoxidation of steel with alloys of silicon, calcium and barium has been performed.

Effect of modification on the formation of nonmetallic inclusions in kp-t wheel steel

Effect of modification on the formation of nonmetallic inclusions in kp-t wheel steel

Modeling Inclusion Formation during Solidification of Steel: A Review

The formation of nonmetallic inclusions in the solidification process can essentially influence the properties of steels. Computational simulation provides an effective and valuable method to study the process due to the difficulty of online investigation. This paper reviews the modeling work of inclusion formation during the solidification of steel. Microsegregation and inclusion formation thermodynamics and kinetics are first introduced, which are the fundamentals to simulate the phenomenon in the solidification process. Next, the thermodynamic and kinetic models coupled with microsegregation dedicated to inclusion formation are briefly described and summarized before the development and future expectations are discussed.

Cyclic-deformation system for the reduction of continuous-cast slabs

Introducing systems capable of profound reduction in a casting and rolling module improves the product quality, on account of the intense working of large continuous-cast slabs over the whole cross section and the production of uniform fine-grain structure of the metal, and also increases the cross section of continuous- cast billet. Analysis of the formation of nonmetallic inclusions and segregation in the axial zone of the thick rolled sheet is followed by analysis of the nonuniform deformation over the slag height in the reduction of large continuous-cast slabs at the 5000 mill at OAO Magnitogorskii Metallurgicheskii Kombinat. The structure of a cyclic-deformation system for preliminary deformation of large continuous-cast slabs is described, and its capabilities are explored. Hammers for preliminary deformation of large continuous-cast slabs are considered. Experimental data are presented for the deformation of continuous-cast steel 45 and 12Kh18N10T steel billet. The structure of the continuous-cast billet is assessed in the course of reduction on the cyclic-deformation system. The basic parameters of the system for preliminary deformation of large continuous- cast slabs are determined. The capabilities of the cyclic-deformation system are outlined in terms of increase in sheet quality. On that basis, the use of the cyclic-deformation system in the continuous-casting line for preliminary reduction of large continuous-cast slabs is recommended: it permits matching of the speed of continuous-casting and cyclic-deformation processes; and ensures 45–90% reduction in a single pass so as to obtain well-worked cast structure over the whole slab cross section. When using the cyclic-deformation system in the continuous-casting line, the continuous-cast slabs are reduced by means of the heat of the cast metal, thereby greatly reducing the energy consumption in billet production. The cyclic-deformation system may be used with thick-sheet and broad-strip mills for preliminary single-pass reduction of the hot slab, with improvement in sheet quality and reduction in the number of passes in the mills.

Effects of Zr, Ti, and Al Additions on Nonmetallic Inclusions and Impact Toughness of Cast Low-Alloy Steel

A microalloying of the low-carbon and low-alloy cast steel was conducted with Zr, Ti, and Al that were added to the steel in four combinations. After heat treatment, the samples were tested for impact toughness at room temperature using the Charpy method. The highest values of impact toughness were obtained in the group treated with Zr, while Zr-Ti and Zr-Ti-Al groups showed moderate toughness values; the lowest values were observed in the Zr-Al group. Difference among the treatment groups was observed in the fracture mechanisms, morphology, and area distribution of the inclusions. High toughness values achieved in the trials treated with zirconium corresponded with smooth ductile fracture. The metal treated with a combination of zirconium and titanium had a relatively small area occupied by inclusions, but its toughness was also moderate. Lowest impact toughness values corresponded with the larger area occupied by the inclusions in the trials treated with aluminum. Also, a connection between the solubility product [Al][N] and impact toughness was established. The study also provides a qualitative description and quantitative analysis of the nonmetallic inclusions formation as a result of microalloying treatment. The precipitation sequence of the inclusions was described based on the thermochemical calculations for the nonmetallic compounds discovered in the experimental steel. A description of the size distribution, morphology, and composition was conducted for the oxides, nitrides, sulfides, and multiphase particles.

The Study of Nonmetallic Inclusions Formation for Kaplan Blades during the Solidification Process

The exploitation durability of Kaplan hydraulic turbines blades is first of all determined by their structure, by the steel elaboration technology, respectively by the content of non-metallic inclusions and later by the physical-chemical parameters of the exploitation environment.This paper presents a study regarding the situations in which the elaboration-casting technology of Kaplan blades using alloyed austenitic stainless steel, X5CrNiMo17-13-3 which has an important role in the quality of castings. Thus, the authors verify the formation of sulfides and of oxi-sufides during the steel elaboration process, treatment during a liquid state and their influence in the castings behavior to wearing. It is a well known fact that the presence of sulfides and oxi-sufides in the cast blades structure accelerates the corrosion process in contact with river waters.

Effect of Acid-Soluble Aluminum on the Evolution of Non-metallic Inclusions in Spring Steel

The content of acidic soluble aluminum in molten steel ([Al]s) is of significance to the control of total oxygen (TO), the formation of non-metallic inclusions, and the improvement of the surface quality of billets. Industrial trials and thermodynamic calculations were performed to study the effects of [Al]s content on the TO and the evolution of non-metallic inclusions in 60Si2Mn-Cr spring steel that was deoxidized by Si-Mn ((low aluminum process (LAP)) and Si-Mn-Al (high aluminum process (HAP)). The results show that the [Al]s contents in billets are within 0.0060 to 0.0069 mass pct in the LAP and 0.016 to 0.055 mass pct in the HAP. The TO content at each station of the LAP is higher than that in the HAP; the inclusions of billets were mainly of the CaO-Al2O3-SiO2 type in the former, and of the CaO-Al2O3-MgO and CaS-Al2O3-MgO types in the latter. A tendency is found that the higher the [Al]s, the easier it is to deviate from the low melting point region of the inclusion distribution and the larger the size of the inclusions. The relationships between [Al]s and the melting point of the oxide inclusions and the Al2O3 content in the oxide inclusions are also discussed in terms of experiment and calculation.

Formation of nonmetallic inclusions in the carburization of steel by high- and low-ash reagents

The solution of high-ash carburizing agents (dry-quenching dust, coke breeze) and low-ash agents (MU-95) in molten steel is studied. Relatively stable C–O and C–O–Fe complexes are formed on solution. When high-ash carburizing agents are introduced in the melt, the liberation of volatiles leads to decrease in their particle size, increase in the open pore volume, and faster exchange of carbon and iron between the phases. Carbon from low-ash carburizing agents dissolves mainly through the outer surface of the particles. The oxygen present forms CxOy complexes with the remaining carbon, on account of strong C–O bonds. Consequently, the assimilation rate of the carburizing agents is reduced. The solution of the inclusions may be accelerated by introducing optimal quantities of rare-earth elements that reduce the carbon–oxygen complexes.

Formation and Evolution of Non-metallic Inclusions in Medium Mn Steel during Secondary Refining Process

Formation and Evolution of Non-metallic Inclusions in Medium Mn Steel during Secondary Refining Process

Interpretation and Classification of Non-Metallic Inclusions

Abstract The non-metallic inclusions in steel are one of the most important parameters of metallurgical quality. Despite the extensive progress in thermodynamic description of non-metallic inclusions formation in the liquid and solidifying steel, a complete simulation of their evolution during secondary metallurgy, casting and solidification is impossible. The processes for non-metallic inclusion formation, growth and elimination, taking into account macro- and micro-segregation evolution, are too complicated. Therefore, a statistically reliable estimation of the amount, morphology, size distribution and chemical composition of non-metallic inclusions obtained by modern experimental approaches could be an important basis for understanding steelmaking technology. Automated feature SEM/EDS analysis of the chemical composition, size, and volume fraction of more than 600 non-metallic inclusions in rail steel was conducted. Analysis of these non-metallic inclusions' database by developed software found the following clusters of inclusions: (1) oxides, Al-Ca-Si-Mn-S-O; (2) predominantly sulfides, Mn-S-Al-Ti-O; (3) oxides and sulfides, Mn-S-O; and (4) complex non-metallic inclusions, Ti-Mn-O(N). All found compositions of non-metallic inclusions were placed on the ternary diagram Mn-Al-S and they lined up from the Al corner to the MnS point on the Mn-S axis. The chemical compositions of the non-metallic inclusions evolved from Al-Ca-Si-Mn-S-O to Mn-S-Al-Ti-O and, finally, to the Mn-S-O+Ti-Mn-O(N) system. Interpretation of the chemical composition of non-metallic inclusions by thermodynamic modeling revealed the nature of each cluster with correspondence to the secondary metallurgy stage where they were formed. This information could be useful for improvement of steelmaking technology. Accumulation of cluster analysis results for non-metallic inclusions in different steels could be a basis for the development of a universal classification of non-metallic inclusions produced by modern secondary metallurgy technologies.

Influence of rare-earth modification on the formation of nonmetallic inclusions in high-carbon steel

The content of nonmetallic inclusions when rail and wheel steel is produced by intensive modern technology and modified by rare-earth metals is analyzed. The composition, morphology, dimensions, and distribution of the inclusions in the steel are determined in the case without oxidation by aluminum or treatment by silicocalcium and also with treatment of aluminum-bearing steel by both rare-earth metals and silicocalcium. Modification with rare-earth metals reduces the content of oxide inclusions in the rail and wheel steel. That improves the plasticity and impact strength of the products.

Features of Nonmetallic Inclusion Formation and Evolution During Ladle Treatment and Continuous Casting of Special Alloy Steels

Features of nonmetallic inclusion formation and evolution in special alloy steels during ladle treatment and continuous casting are studied for special alloy steel 40Kh. The main differences in types, sizes, and morphology of nonmetallic inclusions in relation to steel deoxidation scheme are analyzed. It is established that the composition of more than 97% of oxide inclusions present belongs to CaO–Al2O3–SiO2, Al2O3–MgO–SiO2, CaO–Al2O3–MgO, CaO–Al2O3–MgO~5% SiO2, Al2O3–MnO–SiO2 systems. The main factors that affect the formation of aluminum-magnesium spinel are determined. It is shown that a non-optimal slag regime in a tundish leads to formation of silicate inclusions with cross section of more than 1000 μm2, even with a steel aluminum content more than 0.015 wt.%.