Cross Section Of Ingot Research Articles

Devising manufacturing techniques to control the process of zonal segregation in large steel ingots

A method of physical modeling was applied to study the effect of external actions on the processes of crystallization and the formation of the structure of ingots. A brief review of existing hypotheses about the evolution of physical, structural, and chemical heterogeneities in large steel ingots is given. The parameters of the structure and the two-phase zone have been determined, as well as the nature of the distribution of segregated materials along the cross-section of ingots, depending on the conditions of their curing. The decisive importance of convective and capillary mass transfer in the interdendritic channels of hardening ingots on the formation of a zonal heterogeneity at their cross-section has been proven. Experimentally, when crystallizing a model environment (camphene), it has been visually confirmed that the flow of segregated materials in interdendritic channels occurs when a certain amount of impurities accumulates in them. A clear dependence of the speed of this flow on the rate of melt crystallization has been established. With an increase of the hardened part of the melt, the rate of segregated material movement (Vl) increases while the rate of crystallization (R) decreases due to worsening heat release conditions. At a certain distance from the ingot’s surface, these rates become equal, and impurities are carried to the curing border, which is the main cause of the formation of zonal segregation. The results reported here show that the evolution of zonal segregation in ingots can be controlled using various techniques involving external influence on the hardening melt. This study has demonstrated that the adjustable intensity of heat removal from an ingot, as well as the addition of external excess pressure on the hardening melt, could be used as such tools. In the study, to obtain ingots with a minimum level of chemical heterogeneity, it would suffice to provide the following conditions for the curing of the alloy: a value of the alloy crystallization speeds at the level of Rcr ≥ 9·10–2 mm/s, or external pressure on the free surface of ingots Рext. ≥ 135 kPa. The industrial implementation of the reported results could make it possible to improve the technology of obtaining large blacksmith ingots, provide savings in materials and energy resources, increase the yield of a suitable metal, and improve its quality

К использованию тепловизоров в решении актуальных задач теплофизики на металлургическом предприятии

This paper formulates and substantiates the list of topical problems of thermal physics in relation to hazardous production facilities that constantly arise and require prompt solutions at a metallurgical enterprise. Many problems can be successfully solved using optoelectronic equipment, such as a thermal imager. Thermal imager allows to scan the entire object completely without contact. Topical tasks that can be solved with the help of a thermal imager: monitoring and evaluation of the probability of trouble-free operation of the steel ladle lining during its heating, wear resistance of the converter during oxygen purging of the metal melt, spills of the metal melt from the converter, damage of the exit edges of the nozzles of gas-air burners, determination of the surface temperature of the walls of various furnaces, etc. In the converter, electric steel-making and other workshops, with the help of a measuring thermal imager or pyrometer, it is possible to monitor heat leaks from the production premises, to obtain the distribution of the local heat transfer coefficient on various parts of the thermal surface. It is also possible to predict the temperature condition in emergency situations, confirm the requirements for the thermal mode of the operated object, identify and control ingots and billets with regard to their grain size and uniformity in the ingot cross-section, etc. Paper presents the examples of thermograms obtained both for the steel ladle and for other objects. Formulated list and experimentally confirmed solutions of thermal problems clearly show that with the help of a thermal imager it is possible to quickly, efficiently, and reliably solve the complex problems of heat exchange and heat transfer in the subdivisions of a metallurgical enterprise.

Хімічна і фізична неоднорідності та гази у великому сталевому зливку

For creation of the high-tech equipment that is used in energy, heavy engineering, chemistry and transport, the unique large-sized steel products are required. In the manufacture of such products, large forging ingots in the mass to 600 tons are used. However, an increase in the mass of the ingots leads to the formation of chemical and physical heterogeneity, enlargement and unfavorable distribution of non-metallic inclusions, of the development of segregation defects in them, which reduce the strength and exploitation characteristics of the metal. In this connection, the quality forgings and finished parts are not always meet the producing demands and the loss of metal, in the form of technological waste and rejects are reaching significant values. It is known that eccentric zonal segregation, especially it’s the most dangerous variety - cords, significantly reduce the quality and properties of products from large steel ingots. In connection with the continuous expansion of the production of large ingots, the problem of creating optimal technologies for their formation, which reduce or exclude the possibility of the formation of chemical heterogeneity and cords in steel during crystallization, it is currently important and relevant. In this paper it are presented the results of studies of the structure, gas distribution, physical and chemical heterogeneities in the cross section and height of an ingot in the mass of 140 tons, which was casted in vacuum from steel 25KHN3MFA. It is shown that depending on the temperature and time conditions of ingot hardening, among which the crystallization interval (due to the chemical composition of steels), cooling intensity in different volumes in height and cross section of ingot, temperature gradient before the crystallization front, solubility of alloying elements and gas content in the melt, etc. Based on this, when developing technology for large ingots to ensure their quality, optimal structure and properties should take into account not only their dimensions, but also the combination of these thermokinetic parameters on the crystallization process, dendritic structure formation, manifestations of liquation in different ingot volumes. Keywords: ingot, segregation strip and inclusions, dendrites, structure, oxygen, oxides, sulfides.

INFLUENCE OF MODIFICATION OF STEEL 45 ON THE CHEMICAL COMPOSITION AND CONTAMINATION WITH NON-METALLIC INCLUSIONS

The article presents the results of research on the effect of modification on the chemical composition and contamination by non-metallic inclusions along the length and cross-section of ingots modified with a fine mixture of powders. It was found that the introduction of a modifier reduces the heterogeneity of the cast structure structure Changes the chemical and phase composition of non-metallic inclusions, reduces their size.

INFLUENCE OF METAL OXIDATION AND FEATURES OF VACUUMING ON THE FORMATION AND LOCATION OF NONMETALLIC INCLUSIONS IN LARGE STEEL INGOTS 38ХН3MФA

The article deals with the influence of steel oxidation and features of vacuuming on the processes of formation and distribution of non-metallic inclusions in large ingots and forgings intended for power engineering. It is shown that the distribution of sulfides and oxysulfides across the ingot cross-section is inversely related to each other, due to changes in oxygen and sulfur concentrations during the crystallization of the melt. Under the influence of intensification of degassing process at vacuum casting of ingots at the expense of purging of a jet of metal argon, the formed nonmetallic inclusions had the minimum sizes, more favorable distribution that caused increase in plastic characteristics of the received forgings on the average for 15-20 %

The modification of hypereutectic high-alloy silumins — prospects for the development of technology for producing materials with a low linear expansion coefficient

This article discusses the possibilities of using hypereutectic silumins and the problems that impede their wider distribution. The known methods of manufacturing products from hypereutectic silumins of high quality are shown. A method for producing casting blocks from hypereutectic silumins by direct chill casting is considered. The possibility of milling primary silicon crystals by introducing modifiers and master alloys of Al-Si-P, Al-Cu-P systems, inorganic carbon and phosphorus compounds is shown. The tendency of copper-doped silumins to hot shortness is shown. The technology of impact on the melt of ultrasonic cavitation is considered together with the introduction of additional active modifiers made of master alloy rods to obtain casting blocks from hypereutectic high-alloy silumins using the method of direct chill casting with a primary silicon crystal size of no more than 10 µm. Technological principles for reducing the grain size of α-solid solution, uniformly distributed over the ingot cross-section, are proposed.

Application Of Ni-Mg-Ce Master Alloy Scrap For Inoculation Of Copper-Nickel Alloys

<p class="TTPAbstract">The problems of production of copper-nicckel alloys ingots by semicontinuous casting method are analysed. The requirement of grain size refinement in cast alloys macrostructure is shown. It is necessary to reduce the probability of hot cracks formation and increase the fabricability of cast bars during plastic working. The reasonability of fine fraction of Ni-Mg-Ce master alloy application for inoculation of copper-nickel alloys is established. The results of laboratory experiments on the study of master alloy quantity influence the structure and hardness of Cu-5Ni-1Fe, Cu-10Ni-1Fe-1Mn and Cu-30Ni-1Fe-1Mn copper-nickel alloys are presented. On the basis of industrial experiments it is revealed that inoculation of Cu-5Ni-Fe alloy ingots of diameter 200 mm by Ni-Mg-Ce master alloy leads to considerable reducing of macrograin size. It allows to improve mechanical properties of ingots and ensure their uniform distribution in cross section of ingots. It is established that residual magnesium content in alloy must be in range from 0,02 to <br />0,06 wt. %. The use of Ni-Mg-Ce master alloy makes it possible to increase the processability of copper-nickel alloys during plastic working and utilize the fine fraction master alloy scrap inevitably formed during its production.</p>

Study on the Porosity in Al-Zn-Mg-Cu High Strength Alloy DC Ingot

An Al-Zn-Mg-Cu high strength alloy ingot produced by Direct-Chill casting was used in this study. The distribution of porosity in the cross section of the DC ingot was investigated by the precision density method (Archimeds’ principle), also X-ray microtomography technique was used to quantitatively analyze porosities in typical positions. The pattern in the cross section as well as in the thickness and width direction was obtained. The results show that: in the cross section of the ingot, porosity was increasing gradually from the surface to the center of the ingot; porosity shows an overall escalating trend from the surface to the center of the ingot both in thickness direction and in width direction; porosity was closely related to the cooling rate in the ingot; oxide inclusions have an effect on the formation of porosity to some extent.

Characterization of the loss of the dislocation-free growth during Czochralski silicon pulling

The loss of the dislocation-free growth (structure loss) during Czochralski (Cz) silicon pulling can have a strong negative impact on the production yield of the Cz photovoltaic industry. As almost no publication has been dedicated to this phenomenon in the past, this paper aims at investigate in detail the loss of the dislocation-free growth and its origin by characterizing an industrial-scale n-type Cz silicon ingot exhibiting such issue. After the occurrence of a perturbation, generation and propagation of slip dislocations in the already grown crystal have been observed. These dislocations, generated over the whole ingot cross-section, propagate with the solidification front during further growth. Additional small perturbations seem then to be responsible for their multiplication together with the transition to a multicrystalline structure. Investigations were conducted to find the perturbation causing the structure loss in the ingot. A pinhole, small gas bubble of 0.5mm diameter, was identified as the main cause for the generation of dislocations.

Prediction of Carbon Liquation in Steel Forging Ingot Cross Section

Published experimental data about steel forging ingot chemical inhomogeneity with different steel weight and composition are summarized. An equation is obtained for calculating the carbon liquation factor over an ingot cross section in relation to weight and configuration (H/D ratio), and also on original carbon and sulfur content in cast steel.

Effect of permanent magnetic stirring on the solidification microstructure and ingot quality of Al-Cu alloys

A permanent magnetic stirring (PMS) facility which was fabricated for investigating the influence of PMS on the solidification of Al-4Cu and 2024 Al alloys is described. It was found that PMS can effectively refine the grain structures of these alloys with the finest grain structure about 100μm in grain diameter. PMS at 600rpm has a similar grain refining effect to adding grain refiner. At the stirring rates over 600rpm, too big gas holes are induced into the ingots. The cracks on the ingot side surface and elongated holes on the ingot cross section caused by unidirectional PMS can be avoided by applying a direction-reversing PMS. PMS can lead to a slightly more uniform eutectic phase distribution in 2024 Al alloy without changing eutectic phase types. A new nucleation mechanism based on the big-bang nucleation theory is proposed to explain the grain refining effect and limit of PMS.

Microstructures of As-cast and Homogenized Hypereutectic Nb62Ti16Ni22 Alloy

The microstructures of hypereutectic Nb62Ti16Ni22 alloy after subjecting as-cast and homogenizing treatment were investigated in detail by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM), respectively. The Nb62Ti16Ni22 alloy was prepared by vacuum arc melting, and then homogenized at 950 °C for 8 h. The results show that bcc-Nb, fcc-Ni, B2-NiTi, TiNb, Ni carbides (NiCx) and NbNi3 phases can be found in the as-cast alloy, but TiNb and NbNi3 phases dissolved during homogenizing. Following the cross section of ingot, the fine equiaxed grain, the dendritic grain and the coarse equiaxed grain can be distinguished from surface layer to interior of the ingot, respectively. With homogenizing, the white long granular bcc-Nb phase was precipitated, and embedded in the gray B2-NiTi matrix phase. The coexistence of bcc-(Nb,Ti) phase and eutectic NiTi phase was affected by the diffusion of Nb element. The Vicker’s hardness of the homogenized alloy was higher than that of the as-cast alloy.

Development of an Integral Production Process for Manufacturing Machinery Billets Based on Computer Simulation

Examples are presented of using computer simulation for evaluating the effect of production parameters on billets' quality properties and development based upon this of rational production regimes. Criteria evaluated during simulation for solidification and forging criteria are described. The possibility is considered of using results obtained during simulation of solidification as starting data in modeling forging processes. One method of reducing the manufacturing cost of metal products, improving the level of mechanical properties of structural and functional materials, and also a way to reduce the scatter of these properties is prior simulation of production process stages and revelation of the optimum values of production parameters. In each stage of a production cycle, billet qual- ity is described by its own collection of criteria, whose values mainly govern features of the further conversion technology. In view of this, development of production processes (including the use of computer modeling) for each subsequent stage should be performed taking account of the maximum amount of billet-semiproduct quality characteristics achieved in the course of preceding stages. Questions of developing integral production processes based on computer modeling have been the subject of many publications, the last of which is work in (1-2). Modeling solidification. The first stage of the cycle for producing billets for engineering, whose technology may be developed on the basis of results of computer modeling, is ingot pouring and solidification. In order to model processes occur- ring in this stage, there is a considerable number of special program products, i.e., Procast, Magma, LVM-Flow, Thercast, and the domestic product Polion. At the Central Research Institute of Machine Building Technology (TsNIITMASh), a computer program of in-house development, called "Large Ingot" (4), and the ProCast commercial program are used for this purpose. The fundamental approach to developing technology for obtaining an ingot involves planning an orthogonal two- factor experiment with a study of the effect on ingot quality test characteristic, mainly parameters governing ingot solidifi- cation features to a considerable extent, i.e., conicity and ratio of ingot height to its central diameter (H/D). As variation parameters it is also possible to use the proportion of sinkhead and/or kumpel part of an ingot, thermophysical properties of the heat insulation materials used, mold wall thickness, etc. The dependence of a test ingot quality characteristic on these parameters is evaluated as a rule by a second order regression equation. The test characteristics considered are pore volume in the axial porosity zone, dimensions of this zone, concentra- tion of liquates over an ingot cross section (primarily, carbon, sulfur, and phosphorus), and distance between dendrite axes.

The Results of the Brass Refining Process in the Reducer Conditions

Abstract This article contains information concerning of the analysis the possibility of defining refinery qualities of the slag based thermo-physical and thermo-dynamical data. It was showed the brass refining with the many-carbide reagents introduced in to the slag. The paper presents the results of the structure analysis of the brass after carbide slag refining in the industrial conditions. The results of the macrostructure analysis have confirmed the argument on high reducing effectiveness of manganese and aluminium carbide used during CuZn39Pb2 alloy melting. The X-Ray microanalysis of the ingot cross-section has shown considerable discrepancies in the disposition of the inclusions. This effects showed on the great influence of reduction melting condition in to the brass melting.

Effect of chilling of the top part of a steel ingot on the conditions of its crystallization and the quality of forgings obtained from it

The crystallization of a steel ingot is physically modeled to determine features of its solidification and the growth of shrinkage defects. The modeling is done using ingots with a standard hot top and ingots with a chilled top. The results obtained in the modeling were substantiated by a study of the cast structure of actual ingots. The character of the development of carbon, sulfur, and phosphorus segregation over the cross section of ingots is determined along with the location and size of shrinkage defects in ingots cast with tops having different thermal properties. Results are presented from a study of the quality of the metal of tubular forgings obtained from experimental and control ingots.

Modifying metal with nanopowder in a continuous bar-casting machine

The modification of metal by nanopowder is studied as a means of improving the quality of continuous-cast bar, complex components, and rebar. The introduction of TiCxNy-Fe nanopowder in the tundish of the continuous-casting machine reduces the liquation of the elements over the ingot cross section and the content of nonmetallic inclusions and also increases the structural and chemical uniformity. The use of nanopowder inoculators changes the structure of complex components (angle bar) and rebar, as well as the shape, size, and distribution of the nonmetallic inclusions, and also reduces the grain size and improves the mechanical properties.

Effect of cooling rate on microstructure formation during crystallization of aluminum alloy 1417M

The effect of cooling rate on the microstructure of alloy 1417M during crystallization with electromagnetic influence and without it is studied. It is revealed that alloy 1417N crystallization under electromagnetic influence with a cooling rate of 900 K/sec provides dispersion of structural components and increased uniformity of the their distribution through an ingot cross section, which promotes an improvement in mechanical properties.

Quantitative metallographic assessment of the electromagnetic casting influence on the microstructure of 7075 Al alloy

This study presents an attempt to obtain the better quality of an aluminum super-high strength alloy by application of electromagnetic field during the casting process. The conventional continuous casting process of aluminum alloys causes many defects, such as surface imperfections, grain boundary segregation, non-uniform grain size, and porosity. The better ingot surface along with the homogeneous fine-grained microstructure, and hence the better mechanical properties of the ingot, can be achieved by applying the electromagnetic casting process. The microstructure characterization, accompanied by quantitative metallographic assessment, reveals that it is possible to avoid or decrease many defects of as cast ingots during electromagnetic casting process. In this article, the microstructure of the samples of as cast 7075 aluminum alloy, obtained with and without electromagnetic field influence, was analyzed by optical microscope and the variation of key alloying elements content, i.e., Zn and Mg, through the ingot cross section was examined by chemical analysis. Besides, the microstructural parameters such as dendrite arm spacing, interdendritic space width, as well as eutecticum and intermetallic phases volume fraction, were measured using linear method. The electromagnetic field influence on the microstructure of the as cast 7075 Al alloy was evaluated based on measured quantitative metallographic data.

Simulation of slab solidification in the mold of a continuous-casting machine

The mold is a key component of continuouscast� ing machines. Its function is to extract heat from the melt and to create a reliable crust at the surface of the nascent billet, capable of withstanding the ferrostatic pressure of the liquid steel after the billet leaves the mold. The economic efficiency and viability of continu� ous casting largely depend on the performance and, in particular, the working life of the mold, which is deter� mined by its structure and the materials employed. The mold's working life also determines the repair fre� quency and hence the productivity of the continuous� casting machine. The state of the mold's working cav� ity and the cooling conditions affect the surface qual� ity of the continuouscast billet. Improving billet cooling in the mold zone will enhance the surface quality of the cast slab, extend mold life, and increase the productivity of casting. The mold design has the greatest influence on the heat transfer between the ingot and the mold. In the upper part of the mold, the liquid metal is in direct contact with the cooling wall. Since the solidifying crust is still thin and pressed tightly to the copper wall, the heatflux density is a maximum. With increase in thickness and cooling of the solid crust, thermal and phase shrinkage of the ingot is observed (especially at the broad face). Consequently, the ingot moves away from the mold wall to form a gap. As a result, heat transfer slows and the ingot crust becomes hotter. In the lower part of the mold, on account of the increased ferrostatic pressure of the liquid steel and the increase in temperature of the crust, it expands, and the ingot approaches the wall. In these conditions, increase in heat transfer is facilitated by a design of the mold's copper walls that ensures contact between the ingot's solid crust and the mold's working surface with minimum gap. To find such a design, we need to know the linear shrinkage of the ingot and, hence, the temperature at all points of the ingot's cross section.

Analysis of mass-transfer phenomena in the dendritic net of solidifying steel ingots. 2. Convective diffusion of the impurity in the dendritic net of solidifying ingots

An analysis of the interaction of the melt flow with the surface of dendritic crystallites has been performed using the concept of a diffusion boundary layer, and the regularities of the impurity distribution over the cross section of ingots and castings in the process of their solidification have been revealed.