Special Casting Research Articles

Effect of Mold Electromagnetic Stirring Position on Flow Field and Solidification Behavior of Four‐Hole Nozzle Arc Continuous Casting Large Round Bloom

For the special casting environment of large round bloom mold with four‐hole nozzle, the reasonable choice of mold electromagnetic stirring (M‐EMS) location is of great significance to the quality control of bloom. In this study, the four‐hole nozzle arc continuous casting of φ600 mm‐large round bloom is taken as an example, a 3D mathematical model of liquid steel flow is built, and the solidification and heat transfer under M‐EMS is established. The optimum M‐EMS position was obtained as Z = 600 mm, which is enhanced flow rates, shell uniformity, and brittle interval width, and offers valuable insights for improving casting quality.

On the reliability of steel frame joints in earthquake zones exposed to low temperatures

The paper analyzes the existing construction solutions of steel frames with a box-section column and an I-beam crossbar in order to use them in earthquake zones, including areas with low temperatures. Such solutions will allow the structure to accept the seismic inertial forces, while maintaining its bearing capacity throughout the entire period of operation. In order to solve this problem, the study proposes to use steel frame joints, which can be used both for the entire frame of the building and on individual floors, thereby creating a “flexible story” effect. The authors studied articles, books and patents issued in Russia, the United States, Japan, China and Iran, analyzed the factors that reduce the reliability and performance characteristics of the joints. The main factor consists in a welded joint, which is used to attach the crossbars to the columns, transverse ribs in the column body, and to form the box section of the column from sheets, angles or channels. The reliability of the welded joint is reduced even more under conditions of seismic zones with low temperatures in Russia. However, units without welded joints require special cast parts or structures, thereby reducing their availability. In this regard, the task consists in developing new original construction solutions for joints that meet the requirements of reliability and availability.

Growth and transition of dendrites in steel strands under different electromagnetic stirring methods

In the industrial continuous casting process, some central defects such as shrinkage cavity, porosity, segregation and crack are generated especially at the final solidification zone of steel strands because of the poor fluidity and feeding ability of molten steel in the center of strand, especially for the special steel strand. In this paper, a new type of vertical linear electromagnetic stirring (V-LEMS) was proposed to apply in the casting of Incoloy 825 alloy ingot and investigate the growth and transition of dendrites, distribution of Ti in the special steel, and compare its effect with the generally conventional industrial rotary electromagnetic stirring (R-EMS). The results shown that the growth direction of primary dendrite under R-EMS is perpendicular to the mold wall, but the primary dendrite growth under V-LEMS have present an upstream dendrite growth state. It proves that the V-LEMS can generate a longitudinal circulation convection in the height direction of ingot, which can strengthen the temperature and composition mixing of the upper and lower melts of the ingot and promote the homogenization of the overall melt temperature and composition. The radial macrosegregation of Ti under V-LEMS is slightly higher than that of R-EMS, but R-EMS tends to increase the longitudinal macrosegregation of Ti element. The longitudinal macrosegregation degree of Ti element under V-LEMS is less than that without EMS and with R-EMS. V-LEMS makes the longitudinal distribution of Ti element in Incoloy 825 alloy ingot more uniform. The research results give some beneficial suggestions for improving the central quality of special steel continuous casting billet.

Optimizing a Polycarboxylate Superplasticizer Molecular Structure to Reduce Apparent Viscosity of Cement Paste at Higher Environmental Temperatures

A high environmental temperature can increase the apparent viscosity of high-performance concrete mixtures, causing difficulties in mixing, transporting, pumping, and molding the mixtures. Although polycarboxylate ether–based superplasticizers (PCEs) have been proven effective in reducing the apparent viscosity of cement pastes, little work has focused on how PCEs with various molecular structures affect the apparent viscosity of high-performance concrete mixtures when environmental temperature increases. In this study, a PCE (T54C3.5), which was synthesized by reacting acrylic acid (AA) and isoprenyloxypoly (ethylene glycol) ether macromonomer (TPEG) (mw=2,400 g/mol) with a ratio equal to 3.5∶1, was used as the control group. Variations on the molecular structure of T54C3.5, including different carboxylate-to-macromonomer ratios, backbone lengths, backbone compositions, side-chain lengths, and side-chain compositions, were made to investigate the effectiveness of the various PCEs in changing the apparent viscosity of an ordinary portland cement paste with the water-to-cement ratio of 0.23 at different environmental temperatures. A rotational viscometer was used to measure the apparent viscosity of cement pastes containing different PCEs, and the working mechanisms for the effective PCEs were discussed. Results showed that reducing the backbone length was more effective than the other variations in improving the viscosity-reducing ability of PCEs at all tested temperatures. The PCEs containing ester bonds were able to retain or slightly decrease the viscosity of their cement pastes when the environment temperature increased from 20°C to 40°C. Reducing the backbone length and introducing ester groups are two effective ways of improving the viscosity-reducing ability of PCEs at a high environmental temperature. Using PCEs with these structures can significantly simplify the manufacturing processes of the cement mixtures with a low water-to-cement ratio when the environmental temperature increases from 20°C to 40°C, without any special mixing or casting method.

A comparative study of iron, cobalt or cerium micro-alloying on microstructure and apparent viscosity of Al-5Ni alloy

The micro-alloying is promising in improving the mechanical properties, thermal conductivity, and castability of the near-eutectic Al-Ni alloys, enabling them to be formed via the special casting or additive manufacturing technique. But the rheological behavior of the molten near-eutectic Al-Ni alloys is not clear. The present work investigates the effect of three kinds of micro-alloying agents (iron, cobalt, and cerium) at 0.3 wt% on the solidification and rheological behaviors of the Al-5Ni alloy. Results indicate that the addition of the micro-alloying element can significantly refine the α-Al grains in the Al-5Ni alloy, leading to the improvement of the thermal conductivity and mechanical properties. The cooling curves thermal analysis suggests that the incorporated micro-alloying element can notably change the cooling rate of the melts during the solidification course. Phase-field simulations illustrate that the different cooling rates cause the change of the shape factor and the fraction of α-Al grains during the solidification course of the alloy, leading to the remarkable difference of the viscosities at different temperatures and shear rates of the Al-5Ni melts. This work provides an in-depth understanding of the correlation between the solidification route and rheological behavior of the Al-5Ni melts with micro-alloying treatment.

A Newly Designed High-Strength Tool Steel with High Wear and Corrosion Resistance

In this study, a newly developed high-strength cast Fe81Cr15V3C1 (wt%) steel with a high resistance against dry abrasion and chloride-induced pitting corrosion is presented. The alloy was synthesized through a special casting process that yielded high solidification rates. The resulting fine, multiphase microstructure is composed of martensite, retained austenite and a network of complex carbides. This led to a very high compressive strength (>3800 MPa) and tensile strength (>1200 MPa) in the as-cast state. Furthermore, a significantly higher abrasive wear resistance in comparison to the conventional X90CrMoV18 tool steel was determined for the novel alloy under very harsh wear conditions (SiC, α-Al2O3). Regarding the tooling application, corrosion tests were conducted in a 3.5 wt.% NaCl solution. Potentiodynamic polarization curves demonstrated a similar behavior during the long-term testing of Fe81Cr15V3C1 and the X90CrMoV18 reference tool steel, though both steels revealed a different nature of corrosion degradation. The novel steel is less susceptible to local degradation, especially pitting, due to the formation of several phases that led to the development of a less dangerous form of destruction: galvanic corrosion. In conclusion, this novel cast steel offers a cost- and resource-efficient alternative to conventionally wrought cold-work steels, which are usually required for high-performance tools under highly abrasive as well as corrosive conditions.

Computational and experimental determination of parameters of laser hardening zones of cast iron

The paper presents the results of metallographic studies and tribotechnical tests of samples of special cast iron of the "C" brand for passenger train brake pads. Regression equations for determining the depth and width of laser quenching zones were obtained using a full factorial experiment. The response surfaces of the system are constructed and the patterns of change are determined the size of the quenching zones depends on the processing modes. It is shown that the greatest influence on the depth and width of the hardening zones was exerted by the radiation power and the scanning speed of the beam. The use of transverse vibrations of the laser beam increased the productivity of the processing process. The microhardness in the zones of laser quenching from the liquid state was significantly higher than the zones of hardening from the solid state in all the studied processing modes. Tribotechnical tests were carried out according to the scheme "plane (wide side of a flat sample of special cast iron grade "C") – the annular surface of the sleeve of the counter-tile (wheel steel grade 2) with the use of semi-liquid lubricant "PUMA". The load and sliding speed varied discretely. The wear resistance of laser–hardened samples was 2.4 - 2.9 times higher than the base material, depending on the area of the hardened tracks. The friction coefficients paired with the wheel steel of the samples with laser hardening decreased slightly, which will allow the use of laser hardening for passenger train brake pads without changing their design.

The Analysis of Mechanical Behavior of Special Concentrically Braced Single-Story Frames With Ductile Casting Steel Connectors

Background: The special concentrically braced frame (SCBF) is an aseismic structure, but its bracing system exhibits brittle failure and premature buckling connected with the weld fracture of the gusset plate and the post-buckling of the braces; thus, maximizing the role of energy dissipation is difficult. Methods: Here, this paper proposes a system of special concentrically braced single-story frames with ductile casting steel connectors. The large inelastic deformation of the bracing system is mainly concentrated in the ductile casting connectors under the earthquake, and the degree of buckling can be reduced. The finite element model of a single-story frame with special central support and casting steel connectors was established by ABAQUS. Monodirectional loading simulations were conducted on 12 groups of specimens with different parameters, then the deformation trend, stress distribution, initial stiffness, and ductility of the specimens were analyzed. Results: The seismic behavior of the frames was evaluated by the variable parameters of the width-thickness ratio of the energy dissipation plate and stiffener, the length of the energy dissipation segment of the casting connectors and the overstrength coefficient. The casting steel connector conducts the main connectors that exhibit good ductile and initial stiffness. Conclusion: The study results provided direct evidence that the seismic performance of specimens is closely associated with the length of the energy dissipation segment of the casting connector and the overstrength coefficient of axial force. Also, the stress distribution, initial stiffness, and ductility of the members can be independently controlled by reasonably designing the casting connector.

Some aspects of stage performances of musicals at Kyiv National Operetta Theatre in 2005-2021

The article is devoted to the peculiarities of staging musicals in the Ukrainian musical theatre of the beginning of the 21st century. Using the example of Kyiv National Operetta Theatre, the author analyses the problems faced by the theatre while staging a musical, investigates practical ways to solve problematic issues, and considers the prospects for further presentation of musicals to the audience. The author pays attention to the motivation of the theatre and production groups during the selection of material for the stage performance: the creative ability of the team, the relevance of the subject, etc. The article examines a creative potential of the theatre, in particular a special cast of a team necessary for the realization of the musical: qualification requirements for soloists, choir, ballet and orchestra. The author draws a special attention to differences between staging a musical and an operetta, focusing on the peculiarities of working with a team who is engaged in both of these genres. The article examines the issue of copyright protection, difficulties faced by Ukrainian theatres working with foreign rights holders. One of the key aspects of the article is the analysis of the experience of cooperation with foreign directors and creation of co-productions. The author also touches the issue of a technical support of the stage as an important condition for creating a high-quality stage product in the musical genre. The conclusion of the study was resulted in generalization of outputs of the conducted analysis.

Solution combustion synthesis of high-entropy metal spinel oxide as oxygen evolution reaction catalyst

High-entropy metal spinel oxide (HEO) is proved to be a promising oxygen evolution reaction (OER) catalyst with high catalytic performance and stability. A short routine synthesis process based on solution combustion synthesis was proposed to prepare (Co0.25Ni0.25Mn0.25Zn0.25)Fe2O4 spinel HEO in this work. During the process, the products were rapidly synthesized and melted due to the high-temperature reaction, and then quickly crystallized on the surface of nickel foam to form a nano-structure coating. With the aid of nano-scale spinel structure, the overpotential of non-activation HEO electrode reaches 276 mV at the current density of 10 mA·cm−2, and after 100 h i-t test, it can be further reduced to 230 mV, which proves the high activity of OER catalysis. The promotion of OER catalytic performance can be attributed to the surface reconstruction caused by the selective element leaching and the boost of oxygen vacancy, leading to the formation of nano-scale flocculation around spinel core after the long-term OER process. This work indicates a special casting process for functional materials and explores the application of rapid crystallization.

Thermo-mechanical behaviour analysis of slab corner during special steel continuous casting

ABSTRACT The corner crack is an important issue during special steel continuous casting. To comprehensively investigate the heat transfer, stress, and shrinkage behaviours of slab corner, a full-scale thermo-mechanical model of a slab and its mould was developed, the inverse algorithm was applied to the model. The model was validated by comparing the calculated data with the measured data in the plant trials. The results showed that the thermo-mechanical behaviours of the slab corner showed a similar tendency but were not the same, which reflected the necessity of building a full-scale model. There exists ‘hot spots’ at the slab off-corner region, and its position moved away from the corner along the casting direction, which affects the temperature and stress distributions. The maximum stress value reached approximately 16 MPa at the mould exit. The model provides an in-depth understanding of slab corner during special steel continuous casting.

Novel Corrosion‐Resistant Tool Steels with Superior Wear Properties

This work presents the novel high‐strength cast steels Fe81Cr15Mo1V2C1 and Fe80Cr15Mo1V3C1 (wt%) with high resistance against abrasion and acid corrosion. By means of a tailored alloy design and a special casting technique, implying high solidification rates, multiphase microstructures composed of martensite, austenite and a complex arranged carbidic network are formed. The increase of the vanadium concentration by 1 wt% results in an enhanced content of martensite and a decreased fraction of metastable retained austenite as detected by X‐ray diffraction and magnetization studies. This affects significantly the deformation, strengthening and wear behavior of the presented cast steels. Nevertheless, both steels achieve very high compressive (>4500 MPa) and tensile strengths (>1100 MPa) already in the as‐cast state. Furthermore, a distinctly higher abrasive wear resistance than the conventional X90CrMoV18 cold‐work steel was determined for the novel alloys. In conclusion, the results of the microstructural, mechanical, tribological and corrosive characterizations illustrate the impact of alloy design and special solidification conditions on the microstructure and resulting properties for the newly developed cast steels. In addition, the high potential of Fe81Cr15Mo1V2C1 and Fe80Cr15Mo1V3C1 as materials for high‐performance tools, requiring high strength besides high resistance against abrasive wear and acid corrosion, is demonstrated.

X-ray computed tomography reveals special casting techniques used with unusual bronze objects unearthed from the Sanxingdui site

Scholars in a wide range of disciplines are interested in the casting techniques used to create the extraordinary bronze objects unearthed from the two pits of the Sanxingdui site. Although researchers have carried out a number of studies on this topic, many technical details remain unclear. This paper offers the first examination of bronze objects from the Sanxingdui site using industrial computed tomography (CT) and provides direct evidence for interpretation of the complicated casting process involved. We show that multiple pouring and various joining techniques were widely used during the casting of bronze objects from the Sanxingdui pits. The precast parts were mechanically connected with one another by the later pouring, which was the crucial technique for the casting of complicated objects. Representative features include the cast-on cramp device of the sun-shaped objects and the tenon connection with dowel found inside many branches of the bronze trees. This paper also describes evidence of core rods made of different materials, which is the earliest example of this technique in ancient China.

ВЛИЯНИЕ СТАРЕНИЯ НА ФАЗОВЫЙ СОСТАВ И МЕХАНИЧЕСКИЕ СВОЙСТВА ВАНАДИЙСОДЕРЖАЩЕЙ ВЫСОКОАЗОТИСТОЙ СТАЛИ

Complex solid solution hardening of austenitic chrome-manganese steels by nitrogen and carbon is one of the most effective ways of production of high-nitrogen austenitic steels (HNS) without using special casting methods. To enhance the solubility of interstitials in the metal liquid state and suppress undesired secondary phases of Cr2N and Cr23C6, the carbide-forming elements (for instance, vanadium) are added to the HNS composition. By now, there are no experimental works on the age-hardening of ultrahigh-interstitial vanadium steels (more than 1 % wt.). In the present work, the authors used the X-ray structure analysis method, electron microscopy, and the uniaxial static tensile tests to study the effect of temperature (600 °С and 700 °С) and duration (0.5 h, 5 h) of age-hardening on the structure and mechanical properties of ultrahigh-interstitial vanadium-containing Cr–Mn steel (Fe–22Cr–26Mn–1.3V–0.7C–1.2N, N+C=1.9 % wt.). The experiments demonstrated that due to the complex decomposition (by intermittent and continuous mechanisms) of austenite saturated by interstitials, the aging at 600 °С and 700 °С is accompanied by a solid-solution hardening of the austenitic phase by carbonitrides Cr2(N, С) and (V,Cr)(N,С). The study identified that the increased temperature and prolongation of age-hardening stimulate the movement of intermittent decomposition front from the boundaries to the center of austenitic grains. (V,Cr)(N,С) particles formed by the continuous decomposition in the austenitic grains hinder the propagation of the reaction front, meanwhile, the large spherical (V,Cr)(N,C) and Cr2(N,C) particles, not dissolved after quenching, have little effect on its movement. At the chosen age-hardening modes, the yield strength of steel increases, and the fracture elongation decreases.

City and war

And two thousand years of war.The war without any special cause.“The star called the Sun” (band Kino)Throughout its history, humanity has been fighting almost constantly. Cities were designed either as fortresses capable to hold the fort, or as permeable structures, which can be quickly restored after destruction. People, whose profession is meant for war, have always been a special caste and evoked a special attitude. We are witnessing an unprecedented process: the war changes its character, becomes undeclared, invisible, hybrid. How will a city, its appearance and functions respond to the new concepts of the war? How should we preserve, study and comprehend the military experience of the previous eras, the experience of educating “people of war” embodied in architecture of military schools?Not so long ago, historic Irkutsk lost the complex of Red Barracks related to the history of Port Arthur. The place is troubled again. While there is no problem with the building of the military school (the Ministry of Defense took it under their wing and is transforming it into the Suvorov School), there is a real war for preservation of exactly the same building of the cadet corps, which is fought in courts and public structures. As usual, we don't try to take these issues off the table or to hide away from inconvenient topics, but start discussing them in a series of articles.

Characterization of perlite and expanded perlite from West Sumatera, Indonesia

As a volcanic country, Indonesia is rich in natural mineral resources. One of them is perlite that is spread across several provinces in Indonesia. One of the companies with a mining business permit (IUP) for perlite is CV Abdi Bersaudara, located at Padang Pariaman Regency, West Sumatra Province. Perlite rock can be processed through comminution and heating method. Crushed perlite can be used as sandblasting, slag coagulant, source of silica, foundry and steel industry, special casting sand and metal finishing. Meanwhile, the expanded perlite is a product of heated perlite with a temperature of 700⁰C-900⁰C. This research aimed to investigate the characters of perlite and expanded perlite from West Sumatra. Qualitative and quantitative analysis was conducted by laboratory experiments and testing, such as atomic absorption spectrophotometry (AAS), X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and optical microscope (OM). Based on the results of this study, West Sumatera perlite can be used as adsorbents, filter media, filler materials and planting media applications.

Dynamic analysis of connecting rod of piston machine used in oil industry

The paper analyzes the stress and deformations for the connecting rod made of steel materialor special cast iron by applying pressure on it in structural analysis, performed on ANSYS software. The analysis of static stress and damages due to the application of pressure is presented and analyzed. Reviewing the analysis results, we can decide whether our designed connecting rod is safe or not under applied load conditions. Investigation of complex problems with respect to friction and wear (clearances), stresses and strains phenomena in connecting rod of piston machines allows to solve the problems of increasing the durability of these machines.

Simulation of surface work-hardening process during controlled inertial impact treatment of parts made of high strength cast iron

The paper deals with the results of simulation of elastoplastic impact of the deforming ball with the surface during inertial impact treatment. The deforming ball is made of hardened steel ShKh15 (GOST 801-78), and special high strength spheroidal graphite cast iron is used as the treated material. The paper provides recommendations on conditions for inertial impact treatment of surfaces.

Hot tearing behavior of NZ30K Mg alloy under progressive solidification

Progressive solidification is usually considered an effective strategy to reduce the hot tearing susceptibility of a cast component. In this study, special constrained plate castings with progressive changes in cross-section were designed, which enabled progressive solidification. The hot tearing behavior of a newly developed NZ30K Mg alloy (Mg-3.0Nd-0.2Zn-Zr, wt.%) was studied under progressive solidification using various mold temperature distributions and constraint lengths. Of these, a homogeneous mold temperature distribution is found to be the best option to avoid hot tearing, followed by a local low mold temperature distribution (with a chiller), then a gradient mold temperature distribution. Unexpectedly, compared with the homogeneous mold temperature distribution, adding a chiller does not provide any further reduction in the hot tearing susceptibility of the NZ30K Mg alloy. A high mold temperature and a short constraint length increase the hot tearing resistance of cast Mg alloys. Progressive solidification is not a sufficient and necessary condition to avoid the formation of hot tearing. The two key factors that determine the occurrence of hot tearing under progressive solidification are the maximum cooling rate and the constraint length. Decreasing these values can reduce the incidence of hot tearing.

PROGRESSIVE TECHNOLOGIES OF FOUNDRY PRODUCTION OF COMPLEX DETAILS

The authors present the results of consideration of advanced technologies of foundry production of complex parts. In mechanical engineering, about 50% of the mass of machinery and machinery is cast, in machine tools - about 80%. This is explained by the number of advantages of foundry production in comparison with other methods of obtaining blanks or finished products. The molds are provided with blanks of both simple and very complex shape with internal cavities, which are impossible or very difficult to obtain in other ways. Some special casting methods allow castings to be obtained with a high surface cleanliness and precision in size, which reduces or completely eliminates subsequent machining. Special casting methods allow you to partially and sometimes completely abandon the use of molding and core mixtures, to carry out complex mechanization and automation of the whole process. In the foundry industry, the following technological processes are progressive: casting in shell molds and smelting models under vacuum conditions, which prevents oxidation of the metal; casting of single-crystal workpieces from heat-resistant alloys by vacuum suction method; casting by gas models; spray molding; modelless casting