Low-alloy Cast Iron Research Articles

Design and Manufacturing of Air Conditioning Coil

This paper consists of the detail design process of a cooling coil which is used in Evaporator of VARC System for given cooling load. The process consists of designing a part using the calculation and various other parameters. The stability of long-term materials is becoming increasingly important as the demand for air conditioning systems in commercial and residential applications grows. Because of temperature variations and heat flow, materials in air conditioning systems can fail, reducing the cooling effect of the system. Low thermal transitions through the coil's material cause a significant amount of heat to be wasted in the evaporator coil, which lowers the system's overall efficiency. This paper outlines the methodology used to choose the right material for the evaporator coil in an air conditioning system using the CES Granta design software. Based on design and functional requirements, nickel-chromium alloys, pure titanium, copper, low alloy steel, cast iron, and pure titanium are the candidates that made the shortlist for evaporator coils. The best candidates are low alloy steel, titanium, and stainless steel.

Improving the Abrasion Resistance of Nodular Cast Iron Castings by Remelting Their Surfaces by Laser Beam.

This paper presents the results of research conducted in the field of the technology of surface hardening of castings from unalloyed and low-alloy nodular cast iron using the laser remelting method. The range of studies included macro- and microhardness measurements using Rockwell and Vickers methods as well as metallographic microscopic examinations using a scanning electron microscope. Moreover, abrasive wear resistance tests were performed using the pin-on-disk method in the friction pair of nodular cast iron-SiC abrasive paper and the reciprocating method in the friction pair of nodular cast iron-unalloyed steel. Analysis of the test results shows that the casting surface layer remelting by laser for unalloyed nodular cast iron results in a greater improvement in its resistance to abrasive wear in the metal-mineral system, as compared to low-alloy cast iron. Additionally, carrying out the laser hardening treatment of the surface layer made of the tested grades of nodular cast iron is justified only if the tribological system of the cooperating working parts and allowable dimensional changes during their operation are known.

Preprocessing of Laser-Induced Breakdown Spectra of Low Alloy Steels and Cast Irons Using Partial Least-Squares Regression Analysis

Preprocessing of Laser-Induced Breakdown Spectra of Low Alloy Steels and Cast Irons Using Partial Least-Squares Regression Analysis

Development and properties of austempered low alloyed white cast iron

Abstract This study examined the response of low-alloy white cast iron to austempering heat treatment. In addition, it investigated the microstructure and mechanical properties of austempered low-alloy white cast iron. The low-alloy white cast iron specimens were austenitized at 900 °C, followed by quick quenching into a salt bath at 375 °C, and held there for 15 to 120 minutes for austempering heat treatment. Microstructural features were studied by optical, scanning electron microscopes, and XRD analysis. The mechanical properties were determined by hardness and unnotched Charpy impact toughness tests. As a function of those austempering times, a microstructural map was constructed to show how the transformation products develop, quantitatively. The experimental results showed that the austempering heat treatment produced a microstructure consisting of eutectic carbides + ausferritic structure in low-alloy white cast iron. It can be concluded that the low-alloy white cast iron can be austempered, similar to ductile cast irons. Improved hardness and impact toughness values have been obtained in austempered low-alloy white cast iron.

Interaction of N with White-solidified Cast Iron Model Alloys: The Effect of Mn and Cu on the Formation of Fe and Si Nitrides

Surface remelting and subsequent nitriding improves the surface properties of cast irons. Upon remelting, a white-solidified surface layer forms, which contains coarse Si-free eutectic cementite (θ) and Si-enriched ferrite, pearlite or martensite in the intercarbidic regions between the eutectic θ. Nitriding produces a compound layer at the surface, which is composed of ε and γ’-iron (carbo)nitrides and enhances the corrosion resistance. Nitriding of white-solidified Fe-C-Si alloys, being model materials for remelted low-alloy ferritic cast irons, has shown that Si dissolved in α-Fe notably affects the formation of ε and γ’ in intercarbidic regions while Si simultaneously precipitates as amorphous nitride, X. Under process conditions only allowing for the formation of γ’ in pure Fe, Si dissolved in α-Fe promotes the formation of ε over the formation γ’, whereas Si-free eutectic θ transforms into nitride following the sequence θ → ε → γ’. The present work studies the nitriding of white-solidified Fe-3.5wt.%C-3wt.%-M alloys with additions of M = 1 wt.% Mn, 1 wt.% Cu or 1 wt.% Mn + 1 wt.% Cu, serving as model materials for remelted pearlitic cast irons. The presence of Mn and/or Cu causes notable deviations from the nitriding behavior known from Fe-C-Si alloys. Mn accelerates the precipitation of X in intercarbidic regions and obstructs the transformation of ε formed from Si-free θ into γ’. Cu promotes the formation of γ’ in Si-rich intercarbidic regions, surpassing the ε-promoting effect of Si.

The Effect of Seven Etching Solutions used for the Differentiated Visualization of Complex Microstructures in Low-Alloyed Cast Iron

Abstract For numerous steel grades, detailed descriptions of different etching techniques and etching times for microstructural analysis are available. However, there are only few reference works for low-alloyed cast iron. Particularly for complex microstructures with combined fractions of bainite, ferrite, pearlite, retained austenite, carbides and martensite, there are only few detailed collections. In addition, the effects of the etchants are rarely investigated for the same image section. Therefore, this study will exclusively compare identical microstructural regions and the effect of different etchants on them. Two specific sample areas were selected in a low-alloyed cast iron and the effect of both surface removal etching and tint etching reagents on them was examined under a reflected light optical microscope and a scanning electron microscope. The results of the study have shown that some etchants for complex microstructures are only suitable in case potentially present phases are already known. However, the combined use of two etching solutions in particular, led to a very detailed and highcontrast image, capable of revealing and resolving microstructures with a variety of phases.

Microstructure and wear resistance of red mud iron alloy with chromium and titanium

Red mud is a solid waste in the production of alumina from bauxite. Red mud iron alloy (RMIA) is prepared from the red mud and laterite nickel ore via the high-temperature carbothermal reduction smelting and refining. Herein, by adjusting the contents of chromium (Cr) and titanium (Ti) in RMIA, low alloy cast iron with high hardness and wear resistance was obtained. Optical emission spectrometer, optical microscope, scanning electron microscopy, and hardness and two-body wear test were used for characterization. The results show that the addition of either Cr or Ti element can lead to carbide formation and refining of graphite. With an increase in the content of Cr or Ti, the hardness and the wear resistance of the alloy were enhanced, and the effect of Cr element was better than that of Ti element. The optimal microstructure and properties of the alloy were obtained at 4.8%Cr0.36%Ti, at which stage, the network eutectic carbide structure disappeared and evenly distributed in the matrix, and meanwhile, the graphite morphology was refined. The hardness of the alloy was higher than high chromium cast iron (HCCI), and the wear resistance of the modified alloy was better than HCCI under low load. The aim of this work is to provide a reference for the preparation of wear-resistant ferroalloys from the red mud directly via high-temperature carbothermal reduction.

Ударостійкий чавун для молольних тіл

A study of the dynamic strength (impact resistance) of grinding bodies cast from low-chromium cast iron in a multi-seat chill mold depending on the chromium content in the alloy is carried out. As a starting point, cast iron of the following composition was used: carbon – 3,0%, silicon – 1,6%, manganese – 0,4%, sulfur – 0,05%, phosphorus – 0,06%. For the study, several batches of balls with a diameter of 60 mm were cast with different chromium content in cast iron, from 0 to 1%. Cast iron was smelted in a medium-frequency induction furnace, such as IChT, with the main lining on a charge of pure pig iron and steel low-carbon scrap. The temperature of cast iron production was 1500 °C. Liquid cast iron was subjected to alloying with medium carbon ferrochrome. Balls were cast in multi-seat chill molds. When tested for impact resistance, the grinding ball received a striking blow of mass 50 kg, falling from a height of 0,5 m. The frequency of application of dynamic loads was 10 beats per minute. Impact resistance was determined by the average number of impacts sustained by the grinding body prior to destruction. An increase in the impact resistance of ball castings has been established with an increase in the mass fraction of chromium in cast iron up to 1%. Moreover, the greatest increase in dynamic strength is observed with an increase in the mass fraction of chromium from 0,3% to 0,5%. With a further increase in the chromium content, the impact resistance of white low-alloy cast iron increases less noticeably, and in the presence of chromium 0,7-0,8% reaches a maximum. The difference in hardness from the surface (~ 52 HRC) to the center of the ball (~ 42 HRC) is a value of about 10 units. The established impact resistance of grinding bodies made it possible to conclude: when grinding solid rocks with high content of solid quartz, the use of low chromium cast iron as a material for grinding media is the most effective, as in terms of achieve high impact resistance, and to ensure cost-effective performance.

Effect of tellurium on microstructure of low-alloy cast iron deposited by electroslag method in current-carrying mold

Effect of tellurium on microstructure of low-alloy cast iron deposited by electroslag method in current-carrying mold

Влияние теллура на микроструктуру низколегированного чугуна, наплавленного электрошлаковым способом в токоподводящем кристаллизаторе

Влияние теллура на микроструктуру низколегированного чугуна, наплавленного электрошлаковым способом в токоподводящем кристаллизаторе

Ползучесть жаропрочного чугуна ЧНХМД при изгибе и сдвиге

Ползучесть жаропрочного чугуна ЧНХМД при изгибе и сдвиге

Coupled Electro-Chemical-Soil Model to Evaluate the Influence of Soil Aeration on Underground Metal Pipe Corrosion

A mechanistic understanding of the process of underground corrosion is important for modeling pipeline deterioration. In this study, a time-dependent multiscale numerical model incorporating electrochemistry and soil hydrology is developed. The model realistically simulates soil moisture and aeration conditions and their influence on anodic/cathodic activity without prior definition. In this manner, both micro- and macrocell corrosion and their evolution with time are simulated along with the effects of differential aeration. The model was validated with low-alloy cast iron corrosion data from the United States National Bureau of Standards corrosion exposure study. The effect of soil aeration in controlling soil corrosiveness was simulated with suitable boundary conditions. It was demonstrated that macrocells arising due to differential aeration can lead to elevated levels of corrosion in pipelines, especially in fairly aerated soils.

Fracture mode identification of low alloy steels and cast irons by electron back-scattered diffraction misorientation analysis

The fracture modes of low alloy steels and cast irons under tensile and fatigue conditions were identified by electron back-scattered diffraction (EBSD) misorientation analysis in this research. The curves of grain reference orientation deviation (GROD) distribution perpendicular to the fracture surface were obtained by EBSD observation, and the characteristics of each fracture mode were identified. The GROD value of the specimen fractured in tension decreases to a constant related to the elongation of corresponding specimen in the far field (farther than 5mm away from the fracture surface). The peak exhibits in GROD curves of two smooth specimens and a notched specimen near the fracture surface (within 5mm away from the fracture surface), and the formation mechanisms were discussed in detail based on the influences of specimen geometries (smooth or notched) and material toughness. The GROD value of fatigue fractured specimen is close to that at undeformed condition in the whole field, except the small area near the crack path. The loading conditions (constant stress amplitude loading or constant stress intensity factor range △K loading) and the EBSD striation formation during fatigue crack propagation were also studied by EBSD observation parallel to the crack path.

Direct preparation of low Ni-Cr alloy cast iron from red mud and laterite nickel ore

Based on the chemical composition requirements and enhancing the utilization value of the products, this work put forward a direct preparation method for low Ni-Cr alloy cast iron from red mud and laterite nickel ore by high-temperature carbothermal reduction smelting and refining. X-ray fluorescence (XRF), optical emission spectrometer (OES), scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS) analysis, hardness and polarization tests were used in the characterization process. The results show that low Ni-Cr alloy cast irons contain 1.50–2.00wt.% Ni and 0.70–0.80wt.% Cr have been prepared as the mass ratios of red mud to laterite nickel ore vary from 80:20 to 70:30, in which the recovery were 93.70% for Fe and 99.83% for Ni, respectively. The alloy cast iron was consisted of ledeburite and cementite matrix with evenly distributed Ni and Cr elements and block and flake graphite precipitated phase. With the increasing of Ni and Cr contents, the hardness and corrosion resistance of the alloy cast irons improved.

Effect of rapid solidification on the microstructure and microhardness of BS1452 grade 250 hypoeutectic grey cast iron

Containerless solidification of low alloyed commercial grey cast iron in two different cooling media (N2 and He) using a 6.5 m high vacuum drop-tube have been investigated. Both the conventionally cooled, as-cast alloy and the rapidly cooled drop-tube samples were characterized using SEM, XRD and Vickers microhardness apparatus. The estimated range of cooling rates are 200 K s−1 to 16,000 K s−1 for N2 cooled droplets and 700 K s−1 to 80,000 K s−1 for He cooled droplets (in each case for 850 μm and 38 μm diameter droplets respectively). Microstructural analysis reveals that the as-received bulk sample displayed a graphitic structure while the rapidly cooled samples display decreasing amounts of α-Fe as the cooling rate increases. At moderate cooling rates α is replaced with γ and Fe3C, while at higher cooling rates with α′. Microhardness increase with cooling rate but cannot be mapped uniquely onto cooling rate, suggesting undercooling also influences the mechanical properties.

Effect of Heat Treatment Parameters on the Toughness of Unalloyed Ausferritic Ductile Iron

Abstract Studies were carried out to determine the effect of heat treatment parameters on the plastic properties of unalloyed ausferritic ductile iron, such as the elongation and toughness at ambient temperature and at – 60 °C. The effect of austenitizing temperature (850, 900 and 950°C) and ausferritizing time (5 - 180 min.) at a temperature of 360°C was also discussed. The next step covered investigations of a relationship that is believed to exist between the temperature (270, 300, 330, 360 and 390 °C) and time (5, 10, 30, 60, 90, 120, 150, 180, 240 min.) of the austempering treatment and the mechanical properties of unalloyed ausferritic ductile iron, when the austenitizing temperature is 950°C. The “process window” was calculated for the ADI characterized by high toughness corresponding to the EN-GJS-800-10-RT and EN-GJS-900-8 grades according to EN-PN 1564 and to other high-strength grades included in this standard. Low-alloyed cast iron with the nodular graphite is an excellent starting material for the technological design of all the ausferritic ductile iron grades included in the PN-EN-1624 standard. The examined cast iron is characterized by high mechanical properties stable within the entire range of heat treatment parameters.

Shape Accuracy of Iron Precision Castings in Terms of Ceramic Moulds Physical Properties Anisotropy

Abstract While analyzing shape accuracy of ferroalloy precision castings in terms of ceramic moulds physical anisotropy, low-alloy steel castings ("cover") and cast iron ("plate") were included. The basic parameters in addition to the product linear shape accuracy are flatness deviations, especially due to the expanded flat surface which is cast plate. For mentioned castings surface micro-geometry analysis was also carried, favoring surface load capacity tp50 for Rmax = 50%. Surface load capacity tp50 obtained for the cast cover was compared with machined product, and casting plate surface was compared with wear part of the conveyor belt. The results were referred to anisotropy of ceramic moulds physical properties, which was evaluated by studying ceramic moulds samples in computer tomography equipment Metrotom 800

Influence of vanadium and chromium additions on the wear resistance of a gray cast iron

A low-alloy gray cast iron containing hard carbide-forming elements, such as vanadium and chromium, was cast by sand mould casting. Its wear resistance was compared with that of an untreated gray cast iron. Three different loading conditions were tested under a constant speed. It was observed that this alloy could reduce the wear loss of standard gray cast iron by up to 89%, which was much greater than what was achieved in previous reports. Scanning electron microscopy (SEM) was used to determine the predominant wear mechanism of both the alloys. In a mild wear regime, the oxidative mechanism was predominant; however, in a severe wear regime, this mechanism was not predominant and the adhesive mechanism was involved. EDX analysis was conducted to evaluate the quantitative amounts of elements in the tribochemical films formed on the wear tracks.

Software Development for Specific Geometry and Safe Design of Isotropic Material Multicell Beams

Comparison of analytical results with finite element results for analysis of isotropic material multicell beams subjected to free torsion case is the main idea of this paper. Progress in the fundamentals and applications of advanced materials and their processing technologies involves costly experiments and prototype testing for reliability. The software development for design analysis of structures with advanced materials is a low cost but challenging research. Multicell beams have important industrial applications in the aerospace and automotive sectors. This paper explains software development to test different materials in design of a multicell beam. Objective of this paper is to compute the torsional loading of multicell beams of isotropic materials for safe design in both symmetrical and asymmetrical geometries. Software has been developed in Microsoft Visual Basic. Distribution of Saint Venant shear flows, shear stresses, factors of safety, volume, mass, weight, twist, polar moment of inertia and aspect ratio for free torsion in multicell beam have been calculated using this software. The software works on four algorithms, these are, Specific geometry algorithm, material selection algorithm, factor of safety algorithm and global algorithm. User can specify new materials analytically, or choose a pre-defined material from the list, which includes, plain carbon steels, low alloy steels, stainless steels, cast irons, aluminum alloys, copper alloys, magnesium alloys, titanium alloys, precious metals and refractory metals. Although this software is restricted to multicell beam comprising of three cells, however future versions can have ability to address more complicated shapes and cases of multicell beams. Software also describes nomenclature and mathematical formulas applied to help user understand the theoretical background. User can specify geometry of multicell beam for three rectangular cells. Software computes shear flows, shear stresses, safety factors etc in all members of three cell beam, analyzes safety of proposed design and provides output with highlighted comments and graphics, in cases where safety factor in any element of multicell beam falls below 1.5. Results of this software were compared and verified with analytical calculations and Microsoft Excel spreadsheet. Development and use of this software provides an easy to use tool, for quick verification of different design cases in three cell beams composed of advanced isotropic materials. Furthermore, the methodology proposed is also useful for similar cases of research in reliable design studies and material analysis.

Effect of alloying elements on thermal shock resistance of gray cast iron

The effect of some alloying elements on the thermal shock resistance of low alloyed gray cast iron was investigated. Alloying of molybdenum, chromium, nickel and tin to the gray cast iron ingot with specified composition was performed to identify optimum composition of alloyed gray cast irons for the best thermal shock resistance. Tensile and thermal shock tests were conducted to investigate the relationship between those two parameters. Scanning electron microscope was used to observe the morphology of cracks which were occurred during thermal shock tests on the surface of specimens. Eventually the results showed that the thermal shock resistance of the gray cast iron, containing (wt.%) 0.8 Mo, 0.2 Cr and 0.08 Sn of alloying elements was enormously increased in comparison with unalloyed and other low alloyed gray cast irons.