Transient Behavior of Inclusion Chemistry,Shape, and Structure in Fe-Al-Ti-O Melts: Effect of Titanium/Aluminum Ratio

Metallurgical and Materials Transactions B - During ladle processing of interstitial-free (IF) steel melts, it is possible for transient titanium-containing oxides to be formed if the local...     

Transient Behavior of Inclusion Chemistry, Shape, and Structure in Fe-Al-Ti-O Melts: Effect of Gradual Increase in Ti

During the processing of liquid steels, nonmetallic inclusions precipitate and evolve under conditions that often involve transient changes in chemistry or temperature, which could be reflected in the final products unless sufficient time is provided for equilibration to be established. The current study is focused on documenting the changes that inclusions undergo in terms of chemistry, shape, and structure when Ti is added in smaller batches, to avoid reactions caused by locally high Ti concentrations and result in a final melt chemistry with a Ti/Al ratio of 1 in the melt corresponding to the chemistry of interstitial free (IF) steel melts in the ladle furnace. When Ti was added in two increments, the inclusion composition was altered from spherical and irregular Al₂O₃ to mostly irregular inclusions that included both Al and Ti after the first addition. The second addition did not cause any change, but with time, the inclusion chemistry reverted back to Al₂O₃ with the morphology change remaining. For the case when Ti was added in four increments, however, the inclusion chemistry was modified largely after the first Ti addition, but the inclusion morphology did not change to the irregular-dominant case until the second Ti addition was made. Part of the Ti-containing inclusions was the result of the dissolution of TiO _x into Al₂O₃. It seems that a critical Ti/Al ratio exists in between 1/4 and 1/2, which determines the morphological change. This finding might be coincident with the required increase in Ti and the decrease of local oxygen, which causes a precipitation of a new TiO _x phase as opposed to dissolution of TiO _x in Al₂O₃. Prolonging the interval between each Ti addition would allow the inclusion change in composition, reverting from the Ti-containing dominant stage to primarily Al₂O₃, but not in morphology.     

Transient Behavior of Inclusion Chemistry,Shape, and Structure in Fe-Al-Ti-O Melts: Effect of Titanium Source and Laboratory Deoxidation Simulation

During ladle processing of interstitial-free (IF) steel melts, it is possible for transient titanium-containing oxides to be formed if the local titanium/aluminum (Ti/Al) ratio is locally and temporarily increased after aluminum killing. The phase stability diagrams suggest that if the Ti/Al ratio is increased, then Al₂TiO₅ and/or a liquid Al-Ti-O region can become stable, and eventually at even higher Ti/Al ratios, Ti₃O₅ becomes stable. In this study, the Ti/Al ratio was successively altered to investigate (1) how the inclusions evolved after titanium addition to aluminum-killed iron melts and (2) whether the inclusions present after sufficient time were those predicted by thermodynamics. When the Ti/Al ratio was maintained at 1/4, such that Al₂O₃ is the only thermodynamically stable oxide, the results show that transient titanium-containing oxides exist temporarily after titanium addition, but with time, the predominant inclusion was Al₂O₃, which would generate little shape change and produce transient stage inclusions with less titanium contents. When the Ti/Al ratio was increased to 1/1 (Al₂O₃ still being the only thermodynamically stable oxide), the results show a more distinct increase in the titanium content of the transient inclusions. The transient reaction was, in this case, accompanied by an irreversible shape change from spherical to irregular inclusions. When the Ti/Al ratio in the melt was increased to 15/1 within the Al₂TiO₅ stable phase region, the inclusion population evolved from spherical-dominant ones to irregular ones. It was found that the final inclusion chemistry has more titanium but less aluminum content compared with the expected from the Al₂TiO₅ chemistry. Besides, the transmission electron microscopy (TEM) results showed the existence of Ti₂O. When the Ti/Al ratio in the melt was increased such that Ti₃O₅ is the thermodynamically stable inclusion (Ti/Al ratio of 75/1 or ∞), the inclusions evolved after titanium addition toward TiO_x inclusions, which is accompanied by a shape change from spherical to irregular. The TEM results revealed and confirmed the existence of metastable Ti₂O besides the thermodynamically stable Ti₃O₅, and it was consistent with the results based on oxidation studies of thin layers of titanium with Al₂O₃ substrate. It was discovered that Ti₂O has the tendency of transforming into the thermodynamically stable phase Ti₃O₅ under certain conditions.     

Solubility of Aluminum in Cryolite-Based Melts

The solubility of aluminum in NaF-AlF₃-Al₂O₃ melts was investigated between 800 °C and 960 °C. The amount of dissolved metal in rapidly cooled samples was analyzed by the reaction with hydrochloric acid under the formation of hydrogen—the volume of which then was determined. Four thermodynamic models that describe the high-temperature equilibrium of aluminum reactions with the NaF-AlF₃ melt were proposed. The best fit for the experimental data was obtained by assuming the existence of a monovalent aluminum species, AlF and $ {\text{AlF}}_{ 2}^{ - } , $ as well as elemental sodium.     

Effect of the Porous Skeletal Iron Structure on the Infiltration of Aluminum Melts

Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was...     

Role of Vanadium in Aluminum Electrolyzer Melts

Metallurgist - The article provides results of testing excess introduction of vanadium into a molten aluminum cell through baked anodes. This stage of special technology is preliminary and required...     

Effect of Inclusion and Filtration on Grain Refinement Efficiency of Aluminum Alloy

Metallurgical and Materials Transactions A - It is well known that the filtration efficiency of ceramic foam filters (CFF) on aluminum melt can be significantly reduced by the addition of grain...     

Oxidation of Aluminum Melts with Rare-Earth Metals

Thermogravimetry studies show that the oxidation of aluminum–rare-earth metal (R) melts obeys a parabolic law. The true oxidation rate of the melts is on the order of 10^–4–10^–3 kg/(m² s). In the Al–R systems, the minimum oxidation rate corresponds to the compositions of intermetallic compounds. The oxidation rate of a melt is shown to increase with temperature. It is found by IRS (infrared spectroscopy) and XRD (X-ray diffraction) that the melt oxidation products consist of γ-Al₂O₃, R₂O₃ (R = La, Ce, Pr, Nd, Y, Sc), CeO₂, and rare-earth metal monoaluminates RAlO₃ (CeAlO₃, LaAlO₃, NdAlO₃).     

Influence of the Magnetic Field on the Crystallization of Aluminum Melts

In order to control the crystallization of metals consciously with the purpose of forming the specified ingot microstructure, various physical fields are used. They vary the internal state of the melt and, consequently, the crystallization kinetics when affecting the melt. In this article, the thermodynamic and kinetics of the crystallization of aluminum under melt processing with the magnetic field is described. A rather simple experimental setup which makes it possible to investigate the magnetic-field effect on the melts of aluminum or other metals and alloys is designed. It consists of several main units: (1) the electrical furnace, (2) the water-cooled copper crystallizer combined with an electromagnetic coil, (3) mechanical facility for the rapid motion of a crucible with the aluminum melt, (4) the monitoring and control system of the melt temperature, and (5) the electronic part for recording and processing information. It is established experimentally that the magnetic field varies the temperature of the melt–crystal phase equilibrium, latent heat of the phase transition, and supercooling temperature of the melt during crystallization. It is shown that the variation in these parameters leads to a decrease in the radius of critical nuclei and an increase in their nucleation rate. The temperature–temporal dependences of crystallization are found. It is established experimentally that the crystallization time shortens under the aluminum melt treatment with the magnetic field. The analysis of aluminum samples formed under the magnetic-field effect showed that their structure is finer grained when compared with the samples not subjected to such treatment.     

Examination of the Strength of Oxide Skins on Aluminum Alloy Melts

The strength of solid oxide skins on Al melts was determined by measuring the maximum force that a skin extended between two moving dies can tolerate before cracking. Two apparatuses were constructed, one with linear motion of plate-shaped dies and one with a rotating disk inside a ring. Using the linear method, individual crack processes can be studied under defined stress conditions with a moderate reproducibility of ± 25 pct. With the rotating method a relative strength parameter is measured with an accuracy of ± 3 pct. By relatively simple tests the effect of melt temperature, oxidation time, and alloy additions can be determined. Examples are given for pure and primary Al, pure Al with Be, Na, Li, Ca, and Si additions, and for some commercial AlMg and AISi alloys. W. Kahl, formerly Ph.D. Student at the Max-Planck-Institut.     

Thermodynamic Calculation of Inclusion Formation in Mg-Al-Si-O System of 430 Stainless Steel Melts

 A phase diagram was drawn through thermodynamic calculation to understand the equilibrium conditions of 2MgO·SiO2, MgO·Al2O3, 3Al2O3·2SiO2, and 2MgO·2Al2O3·5SiO2 formation in Mg-Al-Si-O system of 430 stainless steel melts at 1873 K. Further, the thermodynamic formation and transformation conditions of MgO·Al2O3 inclusion were discussed. The following results are obtained when wSi=026% and wO=10×10-5 in molten steel. The uniphase cordierite inclusion is difficult to exist stably; MgO·Al2O3 inclusion cannot be formed in case of wAl being less than 1×10-6; 3Al2O3·2SiO2 would change to MgO·Al2O3 and 2MgO·SiO2 in turn with increasing the Mg content when wAl is above 17×10-6; with the formation of MgO·Al2O3 inclusion, Al content increases with increasing Mg content when wMg is over 17×10-9. For equilibrium condition and calculated steel composition, 2MgO·SiO2 inclusion would be formed ultimately and MgO·Al2O3 is almost inexistent.     

铝对高碳铬轴承钢氧含量和夹杂物的影响

本文通过运用详实的工艺试验研究及大生产的统计数据，对影响高碳铬轴承钢冶金质量的主要因素进行分析讨论，重点阐述了在不同工艺条件下的加Al量、加Al方式、加Al时间对轴承钢氧含量和夹杂物的影响。     

脱氧合金化工艺对高铝钢中夹杂物的影响

在1873K条件下采用Φ70mm×100mm MgO坩埚在MoSi₂电阻炉上开展了3炉含1.5%Al的高铝钢脱氧实验。实验炉次获得了较高的脱氧率和较低的终点全氧含量。Mn+Nb-Ti-Al-Ca脱氧工艺获得了最高的脱氧率和最低的全氧含量,分别为84.1%和0.0007%。在Al加入钢水中后,夹杂物平均直径和数量均迅速增大。在终点钢中夹杂物均以尺寸为0～3μm的含Al₂O₃的复合夹杂物为主,大部分夹杂物外围包裹CaS或MnS。     

淬火介质因素对7075铝合金厚板残余应力的影响

就淬火介质因素(不同介质浓度、温度)对7075铝合金厚板残余应力的影响进行研究。结果表明：淬火残余应力随着介质浓度和温度增加而减少。即在浓度30％、温度40℃的AQ25l聚合物和乳液介质中淬火，与同温度下水淬相比，残余应力分别降低64．2％和83．5％，而板材显微硬度只降低5％和7％。     

挤压铝材夹杂物的检测鉴别方法研究

由通过采取X荧光光谱仪的半定量成分分析和电镜能谱仪(SEM-EDS)的微区分析相结合的方法,对挤压铝材的夹杂物和参考样品进行了综合比对检测分析,鉴别出夹杂物的种类及来源。此方法证实有效,能协助改善铝材铸造和挤压环节工序中夹杂防控的疑难。     

Liquid Inclusion Distortion by Lens Shape Effect: In Situ Observation and Quantification on LCAK Steels Using HT-CSLM

Metallurgical and Materials Transactions B - Because of interfacial and surface tension, micron-sized liquid oxide droplets are expected to change from spherical (when fully immersed in liquid...