Corrosion-electrochemical behavior of zirconium in molten alkali metal carbonates

The corrosion and electrochemical characteristics of zirconium during its interaction with molten lithium, sodium, and potassium carbonates containing from 1 to 5 wt % additives to the salt phase are studied in a temperature range of 500–800°C using gravimetry, corrosion potential measurement, and anodic polarization. The substances decreasing the corrosion losses due to the strengthening and thickening of an oxide film (lithium, sodium, potassium hydroxides) are used as passivators. Sodium chloride, fluoride, and sulfate serve as corrosion stimulators (activators).     

Corrosion-electrochemical properties of the anodic oxide films formed on aluminum in a chloride-nitrate melt in a 0.5 M Aqueous NaCl solution

The corrosion-electrochemical behavior of aluminum is studied in a chloride-nitrate melt containing 50 wt % eutectic mixture of cesium and sodium chlorides and 50 wt % sodium nitrate in the temperature range 790–900 K in an argon atmosphere.     

Filtration efficiency in casting of a complexly alloyed nickel melt

The use of a cellular ceramic filter is shown to be effective for casting nickel superalloys in vacuum, including superalloys cast using wastes. As a result of filtration, the volume fraction of nonmetallic inclusions and their sizes and quantity in a metal decrease.     

Corrosion-electrochemical behavior of Me23C6 type carbides in sulfuric acid

Conclusions Full anodic potentiostatic curves have been constructed for iron-chromium carbides in dilute H₂SO₄ solutions. The effects of alloying with iron, nickel, and molybdenum, temperature, and acid concentration upon the corrosion resistance of the carbides have been determined.Translated from Poroshkovaya Metallurgiya, No. 4 (124), pp. 50–54, April, 1973.     

Density and surface tension of a concentrated lead melt in nickel

The influence of a lead impurity on the properties of metallic melts in the composition range that obeys Henry’s law is studied. The formation of the structural and physicochemical properties of real concentrated melts can be traced from changes in the temperature and concentration dependences of structure-sensitive properties, namely, density and surface tension. The surface properties of a solution depend on its volume properties and differ from them in enhancement effect. The lead saturation of the nickel melt is found to be accompanied by a compression effect (decrease in the melt volume), which is enhanced to a certain lead concentration. As this concentration is exceeded, the compression effect weakens because of volume separation and the appearance of an excess lead phase. As the lead content in a nickel base increases, the surface tension decreases, a second phase forms, and the melt undergoes separation.     

The role of melt pool behavior in free-jet melt spinning

The influence of melt pool behavior on the competition between the nucleation of crystalline solidification products and glass formation is examined for an Fe-Si-B alloy. High-speed imaging of the melt pool, analysis of ribbon microstructure, and measurement of ribbon geometry and surface character all indicate upper and lower limits for melt spinning (MS) rates for which fully amorphous ribbons can be achieved. Comparison of the relevant time scales reveals that surface-controlled melt pool oscillation may be the dominant factor governing the onset of unsteady thermal conditions accompanied by varying amounts of crystalline nucleation observed near the lower limit. At high rates, the influence of these oscillations is minimal due to very short melt pool residence times. However, microstructural evidence suggests that the entrapment of gas pockets at the wheel-metal interface may play a critical role in establishing the upper rate limit. An observed transition in wheel-side surface character with an increasing MS rate supports this contention.     

Spout eyes formed by an emerging gas plume at the surface of a slag-covered metal melt

This article deals with the spout eyes developing, at the surface of a metal melt, in the ladle during argon stirring. Cold model experiments involving a mercury bath with an oil layer as slag and industrial experiments on a 350 t steel ladle have been carried out. The eye geometry as measured with a video technique is highly dynamic. The time average of the free surface area and the time fraction of complete coverage have been determined and are represented with dimensionless correlations.     

4J50铁镍合金在空气中的氧化行为

研究4J50铁镍合金在500~520℃空气中、22%~60%湿度范围内的氧化规律和氧化动力学,利用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射(XRD)对氧化膜的形貌和相组成进行分析。结果表明:在氧化初期,基体表面生成不连续的氧化膜,其主要成分为Fe2O3;氧化时间为10~15 min时,生成均匀的氧化膜,其主要成分为Fe2O3和Fe3O4;提高氧化温度和相对湿度可加快4J50铁镍合金的氧化过程,相对湿度高于60%会显著降低氧化膜的粘附性。     

Nucleation kinetics of a solidifying metal under an external action

A mathematical model is developed for the nucleation kinetics of metal solidification under an external action using nonequilibrium thermodynamics. The onset characteristics of nonequilibrium solidification are analyzed. The prenucleus metastable growth time is a function of the prenucleus shape, the physicochemical properties of the melt, and the particle volume. The external action energy intensifies the formation of stable nuclei with sizes smaller than the critical equilibrium size in a shorter metastability period than that during conventional solidification.     

Behavior of refractory compounds in alkali metal media

Conclusions An analysis of published data has shown that refractory compounds can be regarded as potentially useful materials for direct energy conversion devices. Further work would appear to be desirable in the following directions: 1) development of polycrystalline materials of increased purity (for example, pyrolytic coatings) whose adsorption properties could be regulated by varying their composition and hence the spectrum of chemisorption binding; 2) synthesis of single crystals, which may open up wide possibilities for the selection of faces with optimum emission-adsorption characteristics. The existence of such a choice is due to a pronounced anisotropy of properties, brought about by the strongly heterodesmic atomic interactions in single crystals of refractory compounds — a result of the presence of metal- nonmetal and nonmetal-nonmetal bonds as well as of metal-metal interactions.Deceased.Translated from Poroshkovaya Metallurgiya, No. 2(158), pp. 49–55, February, 1976.     

Formation of alloy coatings by no-current diffusion saturation of nickel by ytterbium in an LiCl-KCl-YbCl3 melt

Gravimetry is used to study the effect of the temperature and time of no-current diffusion ytterbium saturation of nickel in a molten mixture of the LiCl-KCl eutectic with YbCl₃ on the specific change in the nickel sample weight w = Δm/s, where Δm is the change in the sample weight and s is the sample surface area. The dependences of w on the process time are obtained in the temperature range 773–973 K. The experimentally formed alloy Ni-Yb coatings on nickel are examined by chemical analysis, X-ray fluorescence analysis, and X-ray diffraction. The experimental results demonstrate the presence of one structural zone, which consists of a Laves phase, in the diffusion layer.     

Distribution of metal particles in a slag during argon blowing of a melt in a ladle

The distribution of metal particles in a slag is studied during argon blowing of steel in a ladle. It is established that the fraction of the metallic phase in the top slag layer is 3.5–5 times smaller than that in the middle and bottom layers. A microscopic analysis of the fraction composition and the geometric shape of the metallic particles show that all portions of the slag part of samples contain significantly larger amounts (by a factor of approximately 4–5) of irregular plane particles along with fine spherical particles.     

Corrosion behavior of a Kh30N45YuT alloy and 20Kh23N18 steel in a lithium and potassium carbonate melt during anode polarization

The effect of temperature, the gas phase composition, and the addition of sodium peroxide on the corrosion behavior of a Kh30N45YuT alloy and 20Kh23N18 steel in a eutectic Li₂CO₃-K₂CO₃ melt is studied by measuring the corrosion potential and during steplike anode polarization.     

赤铁粉矿在H2气氛中的闪速还原行为

通过高温下的动力学实验对铁粉矿在H_2气氛中的闪速还原行为进行了研究.采用XRD、SEM和金相显微镜对反应后铁粉矿的物相组成和单个粉矿颗粒表面及内部微观形貌的演变规律进行了分析,采用化学分析法获得了反应后赤铁粉矿的还原度.结果表明:铁粉矿高温下发生的闪速还原仍然遵循Fe_2O_3→Fe_3O_4→FeO→Fe的逐级还原规律.粉矿颗粒的剖面由未反应核和产物层构成,符合未反应核模型的描述.采用模型函数配合法得出铁粉矿与H_2在高温下发生闪速还原反应的限制性环节是界面化学反应,进一步基于动力学模型计算得到,闪速还原的表观活化能为311 kJ/mol.     

Height of the spout of a gas plume discharging from a metal melt

In the present investigation, the height of the spout of a gas plume discharging from the surface of a metal melt has been measured in a laboratory model involving mercury and in real steel ladles. The spout geometry strongly fluctuates with time. This has to be taken into account in the measuring method and data evaluation. Long-term averages of the spout profile and momentary maximum height values have been determined, and it has been found that their nondimensional values are of similar size in the model and in the steel ladle. An engineering formula is presented for the estimation of maximum spout height in argon stirring.     

Transformations of non-metallic inclusions formed during interaction in a cupreous melt containing nickel and oxygen

The values of thermodynamic parameters, which characterize thermodynamic features for interaction processes in the Cu-Ni-O system under the conditions of cupreous-melt and condensed-oxide-phase coexistence, were obtained. The solubility surface of components in metal is constructed for the Cu-Ni-O system at temperatures of 1100–1300°C. The structure and form of oxide inclusions formed during interaction in a cupreous melt containing nickel and oxygen were experimentally investigated.     

Interaction of refractory compound nanoparticles with a surfactant in a nickel melt: I. Heterophase interaction

The interaction of nanoparticles of refractory compounds Al₂O₃ and TiN with a model nickel melt containing a surfactant (sulfur) is studied. The choice of the type of nanoparticles for their interaction with the metal at 1873 K and possible versions of sulfur removal from the melt in the form of S₂, SO₂, and H₂S are grounded. A technique for the preparation of an Ni-Al₂O₃ (TiN) compact and its introduction into the melt is developed. The character of the change in the sulfur content in the metal after introducing the compact is determined, and the effect of the isothermal holding time of the melt on sulfur removal is revealed.