Average Size Of Inclusions Research Articles

Numerical simulation and application of argon blowing from tundish cover for bloom continuous casting

During the continuous casting process, the remaining oxygen in the tundish can be significantly decreased by argon blowing from the tundish cover(ABTC). As a result, the effect of protective casting can be obviously improved, which helps decrease the reoxidation of molten steel in tundish. In the present work, numerical models for ABTC of a six-strand continuous casting machine were established and verified by the measured oxygen mass fraction in tundish during ABTC. The results indicate that the best conditions of ABTC are installing the argon pipes on either side of the tundish cover holes, sealing the baking holes, and keeping stopper rod holes open. The argon flow rate should be ?120m3/h during the period of empty tundish and ?60m3/h during the period of normal casting. Industrial trials of ABTC based on the calculation results were carried out. The results indicated that the increased nitrogen in steel(?w[N]) from the end of RH to tundish decreased by 21.5% from 8.78?10-6 to 6.89?10-6, and the amount of inclusions except for MnS in bloom (scanned size: 8mm?8mm) decreased by 21.3% from 13.43 to 10.57, and the average size of inclusions decreased by 19.0% from 9.27?m to 7.51?m.

Effect of Cooling Rate and Sulfur Content on Sulfide Inclusions in Invar Alloy

Invar alloy has been widely used in modern industry for its extremely low coefficients of thermal expansion (CTE). Sulfide inclusions have a significant influence on the mechanical performance and corrosion resistance of Invar alloy. To improve the mechanical properties of this alloy, which are significantly influenced by the existing sulfide inclusions, a good understanding of the characteristics, including the morphology, size, distribution, and formation mechanism of sulfide inclusions, is required. This study outlines three different cooling modes, water cooling (43.1 K/s), air cooling (16.8 K/s), and furnace cooling (3.1 K/s), to examine the characteristics of calcium sulfide (CaS) inclusions. In addition, a variety of initial sulfur contents under air cooling conditions were investigated. Both laboratory experiments and thermodynamic calculations support the research foundation. The sulfide inclusion particles were extracted through non-aqueous solution electrolysis for further morphology analysis. From the results, we conclude that the cooling rate affects the sulfide inclusion size through the local solidification time. The faster the cooling rate, the larger the average inclusion size. The cooling rate also indirectly influences the morphology of calcium sulfide inclusions that precipitated during the solidification process. In addition, the precipitation of CaS takes precedence over MnS under any circumstances. MnS can only precipitate when there is excessive S content. The different initial S content derived separate supersaturation during CaS precipitation and growth, further influencing the inclusion morphologies.

Effect of Lanthanum Addition on Formation Behaviors of Inclusions in Q355B Weathering Steel.

The effect of lanthanum addition on the formation behaviors of inclusions in Q355B weathering steel was investigated by laboratory experiments and thermodynamic calculations. The results demonstrate that the main inclusions in weathering steel without La addition are large-sized irregular Al2O3 and MnS, with an average size of about 5.35 μm. As La content increases from 0.0075 to 0.0184 wt.%, the dominant inclusions transform from MnS, LaAlO3, and Al2O3-LaAlO3 into MnS, La2O3, and LaAlO3-La2O3. Meanwhile, the average size of inclusions significantly decreases from 3.4 to 2.48 μm and the distribution is more dispersive. When the La content increases to 0.0425 wt.%, the original MnS and Al2O3 inclusions are completely modified into La2O2S and La2O3 but the inclusions demonstrate serious agglomeration and growth. The thermodynamic calculations indicate that Al2O3 and various lanthanum-containing inclusions are formed in the liquid phase. As the La content in molten steel increases from 0 to 0.0425 wt.%, the Al2O3 inclusion is inclined to be modified into lanthanum oxide and lanthanum oxysulfide and the modification process is Al2O3 → LaAlO3 → La2O3 → La2O2S, which is very consistent with the experimental observations.

The effect of Ce addition on purification and inclusion modification of CoCrFeNiMn high entropy alloy

This study focuses on purification and inclusion modification mechanism of equiatomic CoCrFeNiMn high entropy alloys with addition of various cerium (within the range of 0–0.0445 %) smelted by Vacuum Arc Melting (VAM), It was found that there are three types of inclusions in CoCrFeNiMn alloys: Mn(S, Se), AB2O4 spinel type, mixed type (Mn(S, Se) wraps AB2O4), and the average size of the three types of inclusions are 1.1 µm, 5.6 µm, and 4.8 µm, respectively. The addition of cerium can significantly reduce the oxygen content, as well as the sulfur content and selenium content are declined, the inclusions are refined and spheroidized simultaneously. The oxygen content, sulfur content and selenium content were reduced from 150 ppm, 46 ppm, and 105 ppm to 5–7 ppm, 22 ppm, and 80 ppm, respectively. When the cerium content is 0.0012 %, some of the inclusions are modified into three types of inclusions: Mn(S, Se) + Ce2O3, Mn(S, Se) + CeCrO3 and Mn(S, Se) + Ce2O3 + CeCrO3, while the average size of some unmodified AB2O4 spinel inclusions was reduced to 3.1 µm, and the average size of mixed inclusions was dropped to 2.6 µm. When the cerium content is 0.019 %, the inclusions in the alloy are completely modified into Ce2O2(S, Se) + Ce2(S, Se)3. Furthermore, the number density and area fraction of the inclusions are descended from 216.92 mm−2 and 0.1150 % of no cerium alloys to 121.64 mm−2 and 0.0602 %, the inclusions are well spheroidized, and the average size of cerium inclusions is 2.2 µm. Finally, the mechanism on the modification by cerium was discussed based on the composition evolution of inclusion during solidification with Factsage calculation and experimental results. The compositions of inclusions were also analyzed based on the inclusion evolution model.

JM-20, a Benzodiazepine-Dihydropyridine Hybrid Molecule, Inhibits the Formation of Alpha-Synuclein-Aggregated Species.

Studies showed that JM-20, a benzodiazepine-dihydropyridine hybrid molecule, protects against rotenone and 6-hydroxydopamine neurotoxicity. However, its protective effects against cytotoxicity induced by endogenous neurotoxins involved in Parkinson's disease (PD) pathogenesis have never been investigated. In this study, we evaluated the ability of JM-20 to inhibit alpha-synuclein (aSyn) aggregation. We also evaluated the interactions of JM-20 with aSyn by molecular docking and molecular dynamics and assessed the protective effect of JM-20 against aminochrome cytotoxicity. We demonstrated that JM-20 induced the formation of heterogeneous amyloid fibrils, which were innocuous to primary cultures of mesencephalic cells. Moreover, JM-20 reduced the average size of aSyn positive inclusions in H4 cells transfected with SynT wild-type and synphilin-1-V5, but not in HEK cells transfected with synphilin-1-GFP. In silico studies showed the interaction between JM-20 and the aSyn-binding site. Additionally, we showed that JM-20 protects SH-SY5Y cells against aminochrome cytotoxicity. These results reinforce the potential of JM-20 as a neuroprotective compound for PD and suggest aSyn as a molecular target for JM-20.

Modeling of Tensile Test Results for Low Alloy Steels by Linear Regression and Genetic Programming Taking into Account the Non-Metallic Inclusions

Štore Steel Ltd. is one of the biggest flat spring steel producers in Europe. The main motive for this study was to study the influences of non-metallic inclusions on mechanical properties obtained by tensile testing. From January 2016 to December 2021, all available tensile strength data (472 cases–472 test pieces) of 17 low alloy steel grades, which were ordered and used by the final user in rolled condition, were gathered. Based on the geometry of rolled bars, selected chemical composition, and average size of worst fields non-metallic inclusions (sulfur, silicate, aluminium and globular oxides), determined based on ASTM E45, several models for tensile strength, yield strength, percentage elongation, and percentage reduction area were obtained using linear regression and genetic programming. Based on modeling results in the period from January 2022 to April 2022, five successively cast batches of 30MnVS6 were produced with a statistically significant reduction of content of silicon (t-test, p < 0.05). The content of silicate type of inclusions, yield, and tensile strength also changed statistically significantly (t-test, p < 0.05). The average yield and tensile strength increased from 458.5 MPa to 525.4 MPa and from 672.7 MPa to 754.0 MPa, respectively. It is necessary to emphasize that there were no statistically significant changes in other monitored parameters.

Effect of Reoxidation on Inclusions Characteristic During Casting in Al‐Killed Steel Containing Rare Earth

To investigate the effect of reoxidation on inclusions characteristic during casting in Al‐killed steel containing rare earth, two industrial heats, including one of steady casting and the other of reoxidation, are performed with sampling from Rheinstahl Heratus, tundish, submerged entry nozzle, and slab. In the present study, air absorption occurs at the submerged entry nozzle and caused the reoxidation of molten steel. As a result, the number of inclusions increases significantly, and nearly spherical Ce2O2S inclusions are transformed to clustered‐like CeAlO3, which increases the average size of inclusions from 3.92 to 9.21 μm, thereby resulting in serious nozzle clogging and slab defects. The results of thermodynamic calculation show that Ce2O2S is transformed to CeAlO3 with total oxygen content increases under different Ce additions, and this transformation of inclusions can be inhibited by controlling the value of [Ce]/[O] above 2.12. Based on the experimental results and the theoretical analysis, the evolution mechanism of inclusions during reoxidation is clarified. This study can provide theoretical guidance to alleviate the harm of reoxidation to Al‐killed RE‐steel from the inclusion‐controlling perspective.

Effect of Rare Earth Cerium Content on Manganese Sulfide in U75V Heavy Rail Steel

To study the effect of Ce on the morphology of manganese sulfide, we added different contents of Ce into U75V heavy rail steel. The composition and morphology of sulfide in steel were analyzed. The inclusions’ number, size, and aspect ratio were analyzed by automatic scanning electron microscope ASPEX. The results show that the inclusions in heavy rail steel without Ce are elongated MnS and irregular Al-Si-Ca-O inclusions. With the increase of Ce from 52 ppm to 340 ppm, the composition of main inclusions changes along the route of Ce2O2S-MnS → Ce2O2S-MnS-Ce2S3 → Ce2O2S-Ce3S4-Ce2S3 → Ce2O2S-Ce3S4-CeS. Ce has a noticeable spheroidization effect on MnS, which can make inclusions finely dispersed. When Ce content is 139 ppm, the average size of inclusions is the smallest. The mechanism of Ce-modified MnS was discussed by combining experimental results with thermodynamic calculations. Finally, the effect of Ce treatment on inhibiting MnS deformation was verified by simulated rolling.

Effect of alloy element on microstructure and properties of heat-affected zone

In the present study, the influences of general composition (GC steel), magnesium deoxidation treatment (MT steel) and magnesium deoxidation treatment with high vanadium (MVT steel) content on the inclusions, microstructure and low-temperature toughness of the welding heat affected zone of EH36 steel were studied. The thermal cycle process of the heat-affected zone (HAZ) was simulated by a thermal simulator, and then microstructure and impact properties were tested and analyzed. Obtained results show that Magnesium deoxidation treatment and magnesium deoxidation treatment with higher vanadium content decrease the number and average size of inclusions. Compared with GC steel, the austenite grain size of MT and MVT steel reduces at high temperatures so that the nucleation temperature of acicular ferrite in HAZ microstructure increases. Compared with GC steel, the low-temperature impact toughness of HAZ by MT steel and MVT steel increases.

Improve fatigue and mechanical properties of high carbon bearing steel by a new double vacuum melting route

AbstractA new double vacuum melting route (conventional second refining + vacuum arc refining [CSR + VAR]) with 33% lower production cost than the traditional VIM + VAR route has been tried. Compared with the CSR route, the CSR + VAR route reduces the average inclusion size from 27.1 ± 12.3 μm to 13.7 ± 2.4 μm, and the CSR + VAR steel processes a 13.1% higher rotatory bending fatigue (RBF) fatigue strength ( ) and a 3‐timeslonger RCF L10 life. The crescent‐shaped granular bright facet (GBF) zone, normally found in high‐strength steels' very high cycle fatigue regimes beyond 107 cycles normally under a much lower stress amplitude, appears around inner inclusions on the CSR + VAR steel RBF fracture surfaces in high cycle fatigue regimes beyond 3 × 105 cycles. The development of GBF zones is estimated to account for 79%–90% of the RBF fatigue life. The average crack propagation rate (da/dN) for GBF zones varies from 1.3 × 10−12 m/cycle to 24 × 10−12 m/cycle and increases with the stress amplitude.

Effect of in situ observation of cooling rates on acicular ferrite nucleation

Abstract The effect of cooling rates on acicular ferrite (AF) nucleation was observed in situ by laser scanning confocal microscopy. The precipitation characteristics of TiN–MnS inclusions, the austenite grain size, and the content and morphologies of AF were analyzed and compared under different cooling rates. The results indicated that with the increase of the cooling rate, the size of TiN–MnS inclusions precipitated in the test steel gradually decreased while the inclusion number increased. When the cooling rate increased from 0.2 to 10°C·s−1, the average inclusion size decreased from 2.7 to 1.3 µm. The austenite grain size decreased gradually with the increase of the cooling rate, and the larger the cooling rate was, the more uniform the grain size distribution. The AF proportion increased first and then decreased, it reached the maximum when the cooling rate was 5°C·s−1, which accounted for 82.6%. Meanwhile, the dendrite size decreased gradually, the average length decreased from 30 to 5 µm, and the average width decreased from 2.8 to 0.7 µm when the cooling rate increased from 0.2 to 10°C·s−1.

Evolution of Inclusions in Incoloy825 during Electroslag Remelting

Fifty kilogram-scale electroslag remelting (ESR) experiments using slag with different TiO2 contents in an electroslag furnace were performed to investigate the size, amount and types of inclusions in an electrode and remelted ingots. The results show that the contents of aluminum and titanium increased and decreased, respectively, compared to those in a consumable electrode. The inclusions in the consumable electrode were TiS, TiN and Al2O3 surrounded by a TiN layer, and the inclusions in the remelted ingots were TiN, MgO-Al2O3 and MgO-Al2O3 surrounded by a TiN layer. With the increase in the height of the ingots, the average size of inclusions increased from 2.5 to 4.4 μm. Increasing the TiO2 content in the slag promoted the formation of MgO-Al2O3 and made the inclusions larger in the remelted ingots. To make the size of inclusions in remelted ingots of Incoloy825 smaller, the TiO2 in the slag should be decreased. The TiS in the electrode was removed during ESR. Part of the TiN dissociated during the reaction between the liquid metal and slag by molten slag, and most of the TiN inclusions originated from the consumable electrode. The Al2O3 inclusions surrounded by a TiN layer in the consumable electrode were finally transformed to MgO-Al2O3 and MgO-Al2O3 surrounded by a TiN layer in the remelted ingots.

Mechanism of improving transverse corner cracks of peritectic steel slab based on control of inclusions and microstructures with magnesium treatment

In this paper, in order to clarify the mechanism of improving the transverse corner crack of peritectic steel slab with Mg treatment, the inclusions and microstructure characteristics at the slab corner of Al deoxidized (S-Al), (Al+Ca) deoxidized (S-Ca) and (Al+Mg) deoxidized (S-Mg) peritectic steels were studied. The inclusions in S-Al sample are mainly Al2O3, Al2O3 · MnS and MnS inclusions. The S-Ca sample mainly contains Al2O3 inclusions and their complex inclusions. In the S-Mg sample, the number of Mg containing inclusions increase sharply. The S-Mg sample has the smallest average size of inclusions and the largest number of inclusions with the size smaller than 1 µm. The brittle structures are dominant in S-Al sample, which basically disappear in S-Ca sample and S-Mg sample. Mg treatment refines the size of grains at the slab corner, reduces the size of the proeutectoid ferrite films, and restrains the crack propagation along the grain boundary. More IAF microstructures are formed in S-Mg sample. IAFs take MgO · Al2O3 · MnS, MgO · Al2O3 · TiN · MnS and other complex inclusions as the nucleation cores, which diverge and grow outward from the inclusions. Thus, IAFs form a fine crack resistant microstructure, improving the microstructure at the slab corner to prevent the occurrence of transverse corner cracks.

The pitting to uniform corrosion evolution process promoted by large inclusions in mooring chain steels

The corrosion affects the service life of mooring chain steels in marine environments. The evolution of the corrosion process on mooring chain steels in simulated seawater was investigated through in-situ experiments, and the effect of sulfide-oxide complex inclusions on the pitting initiation is discussed. The matrix surrounding sulfide-oxide complex inclusions is enriched in iron sulfide using secondary ion mass spectrometry. The local dissolution of matrix enriched in iron sulfide triggers pitting corrosion. With the immersion time increasing, the corrosion is developed on the matrix around pits to form corrosion rings, resulting in uniform corrosion when corroded areas are connected. Under corrosion product film, the matrix around inclusions is more severely corroded than other areas to form pits. The corrosion behavior of mooring chain steels is a repeating cycle of pitting to uniform corrosion transition. Large inclusions more promote the process of pitting corrosion initiation than small inclusions and increase the rate of transition from pitting to uniform corrosion. • The corrosion evolution process of mooring chain steels is a repeating cycle of pitting to uniform corrosion transition; • The matrix around inclusions is enriched in iron sulfide, which preferentially dissolves and triggers pitting corrosion; • The average size of sulfide-oxide complex inclusions is larger due to high Mn content in material; • Large inclusions more promote the process of pitting corrosion initiation.

Influence of Inclusions on the Nucleation of Acicular Ferrites in a Ti–Zr‐Bearing Steel

Laboratory experiments are conducted to study the influence of inclusions on the nucleation of acicular ferrite in Ti–Zr‐bearing steels. The ferrite transformation in steels with different Ti–Zr contents is observed using a high‐temperature confocal laser scanning microscope (HT‐CLSM). The average composition and size of inclusions and the information about the nucleation of acicular ferrite (AF) are analyzed using a scanning electron microscope. When the content of titanium in the steel increased from 70 to 370 ppm, the main composition in the inclusion transformed from Al2O3 to Ti2O3, the volume fraction of AF increased from 24.4% to 52.5%. The average content of ZrO2 in inclusions is 0%, 18.51%, and 90.39%, when the Zr content of steel is 0 80, and 140 ppm, the volume fraction of AF is 52.5%, 76.9%, and 56.8%. The relationship between the cosine of the contact angle at the inclusions‐ferrite interface and the diameter of inclusions is established based on experimental results, which is consistent with the results calculated based on the classic nucleation theory.

The relationship between inclusions characteristic parameters and bending fatigue performance of 20Cr2Ni4A gear steel

Common heavy-duty 20Cr2Ni4A gear steel is widely used in industrial systems, but there are still problems with its use, such as materials processing issues and a short fatigue life during use. These drawbacks prevent 20Cr2Ni4A from meeting the quality requirements for heavy-duty gear steel in modern industrial systems. Therefore, in practical engineering application, the fatigue life of steel will be predicted to ensure that the fatigue failure of gear steel will not occur in the normal service process. By analysis of the bending fatigue process of structural steel, researchers found that almost every failure is closely related to the size, location and mechanical state of inclusions in the steel. Therefore, in order to accurately characterize the impact of inclusions on fatigue performance, we first used ASPEX inclusion field detection instrument and nanoindentation analyser to make statistics of all inclusions in the two steels, and the contents, distribution, average size and mechanical properties of inclusions in 20Cr2Ni4A steel were accurately counted. Subsequently, the bending fatigue life of two differently processed steels was tested, and a P-S-N curve was drawn. Then, the fatigue fracture was analysed and four fatigue fracture models were summarized to determine the influence of inclusions in the fatigue process. Based on the models by Nisha S, the effects of the number, area, and types of the inclusions were added as corrections, and a new set of life prediction models was proposed. The model was verified by experiments, and the results have a high accuracy. Thus, this approach can be applied to the prediction of the fatigue life of 20Cr2Ni4A steel.

Effect of Mg, La and Ca addition order on inclusions and microstructure of Ti-bearing C–Mn steel

ABSTRACT The influence of addition sequence of Mg, La and Ca on the characteristics of inclusions and the formation of acicular ferrite (AF) were investigated. Results show that inclusions mainly consisted of La–Ca–Mg–Al–Ti–O+MnS in the steel. There was no change to types of inclusions while the layered structure of inclusions was different under different alloy elements addition sequence. The number density of inclusions was the largest in case of Mg was added first, while the average size of inclusions was the smallest. The main type of effective inclusions (nucleus of AF formation) was oxide with MnS shell. The statistical results indicated that the proportion of effective inclusions in case of Mg addition first was the largest among the three samples, which induced more AF formation.

Influences of deoxidation and VOD slag on the behavior of inclusions in Fe–21Cr ferrite stainless steel

The influences of deoxidation process and VOD slag compositions on the behavior of inclusions during refining of Ti–Nb bearing Fe–21%Cr ferrite stainless steels were studied in the present work. The results indicated that the main oxide inclusions by the Al–Si complex deoxidization were MgO·Al2O3. And the main inclusions after Ti addition were MgO·Al2O3–TiOx and Al2O3–TiN complex inclusions. After calcium treatment, the main inclusions became spherical MgO·Al2O3–CaO and Al2O3–SiO2–CaO combined with TiOx and TiN. As the basicity of refining slag was increased from 2.5 to 4.0, the number density of inclusions in the steel reduced, while the average particle size of inclusions increased. When the basicity of CaO–SiO2–(15–20%) Al2O3–10%MgO–5%CaF2 refining slag was 3.5, the number of large inclusions would decrease with the deceasing of the Al2O3 content in the refining slag, and the amount of inclusions in molten steel decreased and the size of most inclusions was distributed within 1–2 μm.

Evolution of Inclusions in Magnesium–Calcium-Treated Liquid Iron

With the development of clean steel technology, the control of non-metallic inclusions in steel is of increasing importance. Magnesium–calcium treatment can effectively balance the castability of molten steel and the control on inclusion size, which is an inclusion modification approach with application prospect. In view of this, how three addition methods (i.e., adding Mg before Ca, adding Mg after Ca, and adding Mg together with Ca) influenced the modification effect of inclusions in liquid iron was experimentally studied, and how these inclusions evolved with time was discussed in this paper. The results demonstrated that despite the sharp difference in their inclusion evolution, composite inclusions with a magnesium aluminate spinel (MAS) core and an outer CaO–Al2O3–MgO layer were formed by all the three addition methods, with the average inclusion size of 1–2 μm. Furthermore, thermodynamic calculation was adopted to reveal the transformation relationship between MAS and calcium aluminate in each of the three addition methods, and clarify the formation and disappearance mechanisms of the intermediate product CaS in the process of Mg–Ca treatment. The thermodynamic calculation results agreed well with the experiment data.

Correlation between Te inclusions and the opto-electrical properties of CdMnTe and CdMgTe single crystals

In this paper, the effects of Te inclusions on the optical and electrical properties of CdMnTe and CdMgTe crystals grown by the modified vertical Bridgman method were investigated. For CdMnTe ingot, the average size and density distribution of Te inclusions along axial direction were in the range of 12 ~ 29 μm and 1.53 × 104 cm−2 ~ 2.81 × 105 cm−2, respectively. For CdMgTe ingot, the average size and density distribution of Te inclusions were in the range of 6 ~ 20 μm and 8.17 × 103 cm−2 ~ 2.42 × 104 cm−2, respectively. The density and size of Te inclusions increased gradually from the first-to-freeze part to the last-to-freeze part for CdMnTe ingot, while that of CdMgTe ingot first decreased and then increased. For both CdMnTe and CdMgTe ingots, the resistivity, IR transmittance and FWHM of (D0, X) peak first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The middle-to-freeze parts of both ingots had the best crystal quality. For both CdMnTe and CdMgTe detectors, the energy resolution and (μτ)e value were first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The detectors fabricated by the middle-to-freeze parts of both crystals had the best performance and can could meet the requirements of room temperature radiation detection.PACS: 78.30.Fs; 78.55.Et; 81.40.Ef.