Search

This document is a special issue of the journal "Materials" that focuses on the recent progress in the structure transition, processing, characterization, and applications of metallic materials. The issue includes research papers on various topics such as the development of dispersion-strengthened copper alloys, the characterization of carbide precipitation in steel, the effect of magnetic fields on aluminum bronze, and the enhancement of impact toughness in cast iron through heat treatment. The issue aims to provide comprehensive and up-to-date information for researchers, engineers, and industry experts in the field of metallic materials. [Extracted from the article]

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. [ABSTRACT FROM AUTHOR]

The paper provides a discussion on the results of studies of the effect exerted by combined degradation factors typical of four types of wear: abrasion, impact–abrasion, tribocorrosion, and impact–abrasion–corrosion, conducted for chain wheels made of Ni-Cu alloyed austempered ductile iron. The studies consisted of determining the content of retained austenite in the structure of the cast irons in question, establishing the measures of wear following wear testing, and identifying the basic surface degradation mechanisms observed in the chain wheels tested following multifactorial wear processes. The chain wheels made of ADI were found to have sustained the greatest damage under the impact–abrasion–corrosion (three-factor) wear scenario, while the wear was least advanced in the abrasion (one-factor) wear case. Another observation derived from the studies is that the combined effect of dynamic forces, corrosion, and quartz sand-based abrasives causes increased surface degradation in the cast iron grades taken into consideration compared to processes characterised by a reduced number of degradation factors (i.e., one- or two-factor wear processes). Additional hardness tests and XRD analyses revealed that a distinctive effect attributable to combined degradation factors on the surface hardness increased value and implied that bench testing was followed by phase transition. [ABSTRACT FROM AUTHOR]

The preparation process and composition design of heavy-section ductile iron are the key factors affecting its fracture toughness. These factors are challenging to address due to the long casting cycle, high cost and complex influencing factors of this type of iron. In this paper, 18 cubic physical simulation test blocks with 400 mm wall thickness were prepared by adjusting the C, Si and Mn contents in heavy-section ductile iron using a homemade physical simulation casting system. Four locations with different cooling rates were selected for each specimen, and 72 specimens with different compositions and cooling times of the heavy-section ductile iron were prepared. Six machine learning-based heavy-section ductile iron fracture toughness predictive models were constructed based on measured data with the C content, Si content, Mn content and cooling rate as input data and the fracture toughness as the output data. The experimental results showed that the constructed bagging model has high accuracy in predicting the fracture toughness of heavy-section ductile iron, with a coefficient of coefficient (R2) of 0.9990 and a root mean square error (RMSE) of 0.2373. [ABSTRACT FROM AUTHOR]

This paper presents an optimized design approach using nonlinear dynamic analysis and finite element methods to ensure the structural integrity of square-shaped containers made from ductile cast iron for intermediate- and low-level radioactive waste packaging. Ductile cast iron, with its spherical graphite structure, effectively distributes stress throughout the material, leading to a storage capacity increase of approximately 18%. Considering the critical need for containers that maintain integrity under extreme conditions like earthquakes, the design focuses on mitigating stress concentrations at the corners of square structures. Nonlinear dynamic analyses were conducted in five drop directions: three specified by ASTM-D5276 standards and two additional directions to account for different load patterns. Fractures were observed in four out of the five scenarios. For each direction where fractures occurred, equivalent loads causing similar displacement fields were applied to linear static models, which were then used for multi-load topology optimization. Three optimized models were derived, each increasing the volume by 1.4% to 1.6% compared to the original model, and the design that best met the structural integrity requirements during drop scenarios was selected. To further enhance the optimization process, weights were assigned to different load conditions based on numerical analysis results, balancing the impact of maximum stress, average stress, and plastic deformation energy. The final model, with its increased storage capacity and enhanced structural integrity, offers a practical solution for radioactive waste management, overcoming limitations in previous designs by effectively addressing complex load conditions. [ABSTRACT FROM AUTHOR]

Austenitic nodular cast iron is a versatile material that offers a unique combination of properties, making it suitable for use in a wide range of applications where high strength, ductility, toughness, corrosion resistance and wear resistance are required. This material is commonly used in a variety of applications in the chemical and petrochemical industries, in the automotive and aerospace industries, as well as in marine and offshore applications. For the experiments, one of the most common austenitic nodular cast irons (alloyed with nickel and manganese) was chosen. The aim of this paper is to evaluate the corrosion resistance of this austenitic nodular cast iron and compare it with other (nonaustenitic) types of nodular cast iron (SiMo- and SiCu-type). Corrosion resistance was determined by an exposure immersion test and an electrochemical potentiodynamic polarization test. Both tests were performed in a 3.5% NaCl solution (to simulate seawater) at ambient temperature. Experimental results prove that austenitic NiMn-nodular cast iron has a higher corrosion resistance than SiMo- and SiCunodular cast iron. Moreover, austenitic nodular cast iron has better plastic properties (higher elongation and absorbed energy) but worse strength and fatigue properties (lower tensile strength, hardness and fatigue limit) than the other types of nodular cast iron. [ABSTRACT FROM AUTHOR]

This paper deals with the austempering of ductile iron (ADI) and clarifies the influential austempering parameters during the production of ADI. During the austempering process, the heat treatment parameters can be varied, thus influencing the final microstructure and, of course, the mechanical properties of ADI. To appropriately conduct experiments and obtain good results, an experimental plan was developed using the Design Expert 13 software. Along with the heat treatment parameters, the influence of the copper content on the ADI toughness, tensile strength, and elongation was determined. The obtained results from this experiment were used to develop unique mathematical models which describe the influences of heat treatment and copper content on the observed mechanical properties of ADI samples. These mathematical models can be applied to predict the analysed mechanical properties of ADI in the dependence of heat treatment parameters and copper content in base ductile iron. For the multi response optimisation of toughness, tensile strength, and elongation, a hybrid grey-fuzzy technique was presented as a significant contribution to the enhancement of the analysed mechanical properties. Consequently, the copper content and heat treatment parameter levels that resulted in the maximal mechanical properties' functions were defined. [ABSTRACT FROM AUTHOR]

This paper presents a comparative analysis of ausferritic ductile cast iron matrix obtained through heat treatment and in its raw state. Ausferrite without heat treatment was achieved by modifying the chemical composition, while nodular graphite was produced using Inmold technology. The presence of compacted graphite in the as-cast ausferritic cast iron was attributed to elements that impede the crystallization of nodular graphite. This study demonstrates that an ausferritic matrix in ductile cast iron can be achieved by incorporating molybdenum in conjunction with nickel or copper. Thermal and derivative analysis (TDA) revealed a minor thermal effect during the transformation of austenite into bainitic ferrite in as-cast ausferritic cast iron. Furthermore, the transformation of austenite in cast iron containing nickel was observed to occur at a temperature of approximately 60 °C higher than in cast iron with copper. The structure of bainitic ferrite platelets in as-cast ausferritic ductile cast iron resembled that of Austempered Ductile Iron (ADI). It was revealed that the amount of austenite in as-cast ausferritic ductile cast iron is more than double that in ADI. The carbon content of austenite was estimated theoretically, revealing that alloying additives in the as-cast ausferritic ductile cast iron reduce the solubility of carbon in austenite, thereby significantly influencing the properties of the cast iron. [ABSTRACT FROM AUTHOR]

The production of high-quality castings without foundry defects at minimal production costs is a constant priority for foundries. Innovation and optimization of production processes are key to achieving this goal. Computer simulation of foundry processes offers a modern alternative to expensive and time-consuming experiments in real foundries and provides a reliable representation and analysis of casting and solidification processes. A detailed analysis of the casting and solidification simulation results allows the prediction of various risks that can cause defects in cast castings, thereby reducing their quality and, last but not least, the cost of their production. This paper deals with the analysis of a computer simulation of the casting of a brake disc in a Slovak foundry. This brake disc has had shrinkages and micro shrinkages that reduce the internal quality of the casting. These defects occurred in the ribs in the upper part of the casting under the feeders. A computer simulation of the casting and solidification of this casting was made according to the real conditions. It turned out that the designed gating system with a system of feeders was not sufficient to eliminate the emerging defects. A new layout for the feeders was proposed, which ultimately eliminated the occurrence of defects based on the results of the computer simulation. The input parameters were set to be as close as possible to the actual needs of the foundry. Moreover, 3D models of the assemblies were designed in SolidWorks Premium 2015 x64 Edition CAD software, and the filling and solidification simulations were performed using the NovaFlow & Solid CV 4.6r42 simulation program. [ABSTRACT FROM AUTHOR]

The sleeve sealing ball seat is one of the important components in the multistage fracturing process of horizontal wells. The erosion and wear of the surface will decrease the sealing performance of the fracturing ball and the ball seat. This leads to pressure leakage during the fracturing process and fracturing failure. In this paper, combined with the actual ball seat materials and working conditions during the fracturing process, the erosion tests of ductile iron and tungsten carbide materials under different erosion speeds, angles, and mortar concentrations are carried out. Then the erosion test results were analyzed by mathematical fitting, and a set of erosion models suitable for sliding sleeve setting ball seat materials were innovatively established. For the first time, this paper combines the erosion model obtained from the experiment and the computational fluid dynamics (CFD) with Fluent software to simulate the erosion of the ball seat. Based on the simulation results, the morphology of the sliding sleeve seat ball after erosion is predicted. Through analysis of the test and simulation results, it is showed that the erosion rate of tungsten carbide material is lower and the wear resistance is better under the condition of small angle erosion. This research can offer a strong basis for fracturing site selection, surface treatment methods, and prediction of failure time of ball seats. [ABSTRACT FROM AUTHOR]

The paper indicates the significance of the problem of foundry processes parameters stability supervision and assessment. The parameters, which can be effectively tracked and analysed using dedicated computer systems for data acquisition and exploration (Acquisition and Data Mining systems, A&D systems) were pointed out. The state of research and methods of solving production problems with the help of computational intelligence systems (Computational Intelligence, CI) were characterised. The research part shows capabilities of an original A&DM system in the aspect of selected analyses of recorded data for cast defects (effect) forecast on the example of a chosen iron foundry. Implementation tests and analyses were performed based on selected assortments for grey and nodular cast iron grades (castings with 50 kg maximum weight, casting on automatic moulding lines for disposable green sand moulds). Validation tests results, applied methods and algorithms (the original system's operation in real production conditions) confirmed the effectiveness of the assumptions and application of the methods described. Usability, as well as benefits of using A&DM systems in foundries are measurable and lead to stabilisation of production conditions in particular sections included in the area of use of these systems, and as a result to improvement of casting quality and reduction of defect number. [ABSTRACT FROM AUTHOR]

Purpose: The foundry industry incurs additional costs as a result of defective castings. Shrinkage defects are a frequent problem in ductile iron castings. It is still essential to understand how shrinkage porosity varies in size when the ductile iron composition changes. This information can be used to produce high-quality cast parts and determine the best processing conditions. The objective of this research paper is to examine the effect of carbon equivalent and inoculation on the morphology of the shrinkage defect using thermal analysis. Design/methodology/approach: This study focuses on certain thermal analysis parameters, such as the angle of the first derivative curve at the solidus temperature, recalescence and its relationships to graphite nucleation and shrinkage tendency. The results of thermal analysis in terms of the cooling curve and its derivative parameters, and thorough characterizations of the shrinkage observed in cup castings produced with various melt compositions and inoculation are presented in the current study. Findings: The proportion of caved surfaces and macro shrinkage porosity defects has been reduced as the carbon equivalent of melt increases from hypoeutectic to a hypereutectic composition. The composition that is slightly hypereutectic has the lowest shrinkage propensity. Although inoculation reduces shrinkage, the importance of this parameter differs depending on the carbon equivalent. Originality/value: The percentage of macro shrinkage porosity and the angle that the cooling rate curve forms are strongly correlated. It is found that the macro shrinkage size decreases as the angle of the first derivative curve at the solidus temperature is reduced. Further, lower macroporosity is produced by a metal that has a higher nodule count in association with a greater cooling rate toward the end of the solidification process. [ABSTRACT FROM AUTHOR]

In this paper, a micromechanical model was developed to predict the residual stress–strain state that is generated around nodules of a ferritic ductile cast iron during solidification. A finite element analysis was performed on a reference volume element of the material to analyze the local strain development, having modeled both matrix and nodule as deformable bodies in contact. The behavior of the nodule was assumed linear–elastic because of the low stresses to which it is subjected during cooling. On the other hand, elasto-plastic viscous behavior was considered for the matrix, considering both the primary and secondary creep regimes. To make up for the lack of information on the physical–thermomechanical properties of the constituents, the available literature data were integrated with the results obtained from the CALPHAD methodology applied to both cast iron and the steel that constitutes its matrix. The micromechanical model was validated by comparing the resulting residual strains with experimental data available in the literature for a ferritic ductile cast iron. Then, it was used for analyzing the correlation between the solidification history and the mechanical response of cast iron in terms of the uniaxial stress–strain curve. [ABSTRACT FROM AUTHOR]

Remarkable casting properties and superior mechanical characteristics of cast iron make it an ideal material for a wide range of industrial applications. However, the production of cast iron components may result in the formation of cracks and defects, posing a significant threat to their structural integrity. Repair welding is a promising solution to resolve cast iron production defects. However, repair welding cast iron components poses unique challenges that stem from residual stress (RS) formation and the possibility of cracking during the repair process. Moreover, research on cast iron repair is scarce. To overcome these challenges, this paper presents a thermo-mechanical model validated by experiments to reduce RS in cast iron repair welding through the optimization of welding parameters and weld sequences as well as the geometry of the repair area. An experimental bead-on-plate weld is set up in order to validate the developed thermo-mechanical model. The temperature distribution in the weld is measured using thermocouples placed around the weld line. An X-ray diffraction technique is used to measure the axial and transverse RS at different points around the weld line. The developed finite element model is employed to simulate the repair welding process and analyze the effect of inter-pass temperature, the number of welding passes, welding sequences, and groove geometry on the RS. The numerical approach applied in this study provides a framework for repair welding optimization of cast iron and other materials, fostering the development of more efficient and reliable repair methods for industrial applications. [ABSTRACT FROM AUTHOR]

This paper presents the results of the abrasive wear resistance of selected types of nodular cast iron, including ADI, cooperating with quartz sand and 100 grit abrasive paper. It has been shown that carbides in nodular cast iron cause an increase in wear resistance of 6 to 12% depending on the surface fraction of the carbides and type of the matrix. For the same unit pressure the mass loss of the cast iron cooperating with quartz sand is many times larger than the cast iron cooperating with abrasive paper. For both abrasives the highest wear resistance showed nodular cast iron with upper and lower bainite and carbides. [ABSTRACT FROM AUTHOR]

This paper presents the effect of the addition of Ti to the zinc bath. Hot-Dip Galvanizing was carried out on a machined ductile cast iron substrate. The process was carried out at 550°C. Experimental baths A, B and C contained 0.01%, 0.05% and 0.1%Ti, respectively. Metallographic samples were prepared to reveal the microstructure of the coatings. Thickness measurements of the obtained coatings were carried out, and graphs of the approximate crystallization kinetics of the zinc coating were prepared. High-temperature galvanization carried out on the treated surface led to the release of graphite beads from the metal matrix and their diffusion into the coating. This phenomenon can have an adverse effect on the continuity of the coating and its adhesion to the substrate. Crystallization of the d phase was observed in the coating, and at longer immersion times - a mixture of two-phase d1 and - phases. With increasing Ti content in the bath, a deterioration in the casting properties of the bath was observed. [ABSTRACT FROM AUTHOR]

In this paper, a novel method for the double heat treatment of ductile iron was applied. Ten sets of specimens (three specimens in each set) of ductile cast iron (DCI) containing 0.51% wt. Cu were prepared and converted to austenitic ductile iron. All specimens were austenitized at 850 °C for 60 min and annealed at 420 °C, 331 °C and 250 °C for 120, 68 and 30 min, respectively. Five sets of samples were then annealed at 500 °C for 60 min, creating a novel double heat treatment process for annealing. Finally, all specimens were slowly cooled in air at ambient temperature. Tensile strength, hardness and elongation were measured in all specimens to compare the specimens with and without subsequent tempering. A microstructural analysis was also performed, which showed that the microstructure changed for the specimens that were subsequently tempered with. The results show that specimens with subsequent tempering have slightly higher hardness, a small decrease in tensile strength and significantly higher elongation. In addition, specimens with subsequent tempering exhibit more uniform mechanical properties compared to specimens without subsequent tempering. The use of neutron beam techniques was proposed to further characterize the newly formed microstructure after subsequent tempering. [ABSTRACT FROM AUTHOR]

The paper presents the results of laboratory tests to determine the effect of an internal polyurethane coating in ductile iron pipes on the quality of disinfected and non-disinfected drinking water. A decrease in the pH of water in contact with the polyurethane coating was found, which was slightly higher in the non-disinfected water than in the disinfected water. The coefficient of variation (CV) of the pH values for the chlorinated water samples was 5.02% and for the non-chlorinated water was 7.15%. The experiments also showed a rather large effect of polyurethane liner on the increase of TOC concentration in water. The presence of disinfectant further slightly increased the amount of organic compounds released. The CV values normalized to one day for TOC were as high as 193.32% and even 199.39% for disinfected water. A significant effect of polyurethane coating was observed on the color change and odor of water. On the other hand, there was no effect of polyurethane coating on alkalinity and chlorine consumption in water. The CV values normalized to one day in both cases were very small at 0.97% and 0.53%, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the wear rate of ferritic and pearlitic ductile iron, as well as three types of austempered ductile iron (ADI materials), austempered at 300, 350 and 400 °C is investigated. Two wear parameters were varied, wear load (0.5, 1.3, 2 kg) and grit paper abrasive grain size (P240, P500, P800). The hardness of ductile iron and stress-assisted phase transformation of retained austenite into martensite (SATRAM) phenomenon in ADI materials were found to play major roles in wear behaviour. The pronounced SATRAM phenomenon was detected for the most severe wear parameters. Another important factor in the occurrence of SATRAM phenomenon is the presence of metastable, low carbon-enriched retained austenite. As a consequence, the wear rate of ADI austempered at 400 °C is nearly equivalent to ADI austempered at 300 °C at medium and high loading with the coarsest abrasive paper grit tested (P240). [ABSTRACT FROM PUBLISHER]

Repairing the worn surfaces of wear-resistant workpieces, such as rollers, is one of the main application fields of surface treatment, but the repairing time is often not considered. In fact, the repairing time is very important, since it affects the repair quality and service life of wear-resistant workpieces. In this paper, a remelted gradient coating was prepared on a ductile iron plate by plasma transferred arc to simulate the repair treatment of wear-resistant workpieces. First, two positions in the remelted gradient coating were defined, i.e., the top of the gradient remelted layer was defined as M1, and the position where the hardness was two-thirds of the top of the remelting layer was defined as M2. Next, the time taken to repair the workpiece when the working surface reached M2 was proposed. Finally this method was verified by a comparative study on the microhardness and wear resistance of the M1 and M2. In this paper, the M2 was located at a ~0.5 mm from the top of the remelted gradient layer. The results show that the microhardness of the position of the M1 was higher than that of the position of the M2. However, the wear resistance of the M1 was worse, as confirmed by the wear rates. At the same time, cracks and fragments were observed on the worn surface of the M1 and M2 positions. Furthermore, the coefficient of friction (COF) of the position of M1 was noted to be first higher and subsequently lower than that of the position of M2, owing to the grinding ball entering the substrate. The abrasion mechanisms of both regions were observed to be complex, including oxidative wear, adhesive wear, delamination wear, and/or fretting wear. The experimental data indicate that it is feasible to determine the repair time according to the microhardness of workpieces. [ABSTRACT FROM AUTHOR]

This paper summarizes the investigation of the conversion of an 11-piece steel fabrication to an austempered ductile iron (ADI) casting. It was a collaborative effort involving the component manufacturer, foundry, machinist, local university, and an ADI heat treater. A number of design concepts were developed, with the final, significantly stronger, ADI design being compared to the fabrication using FEA analysis. The resulting conversion, at similar weight and cost, eliminated the failures that were experienced in the fabricated components in addition to reducing the production lead-time. [ABSTRACT FROM AUTHOR]

The selection of MgFeSi alloy and inoculants used for ductile iron treatment has confounded members of the foundry industry for many years. Frequently foundries have used certain types of alloys "because they have always done it that way" or "because someone else was doing it." The current study involves ductile iron produced with three grades of MgFeSi with varying levels and types of rare earths along with four different inoculants. The iron was cast into test samples of various thickness from 2×2×8 inches to 10×10×8 inches. Mechanical properties and microstructures were evaluated at multiple locations in each of the 36 samples for a total of 156 points of data. In this paper, we will summarize the findings for differing section sizes. [ABSTRACT FROM AUTHOR]

The paper deals in depth with characterizing bead-on-plate welds on EN-GJS-500-14 base metal, utilizing two filler metals: a pure Ni wire and a NiFe wire containing 45 wt pct Ni. The welds were conducted using the same heat input to ensure comparability in microstructure analysis. The microstructural observations were carried out using optical and scanning electron microscopies, X-ray tomography, X-ray diffraction analysis, and microhardness testing. Thermodynamic simulations using the non-equilibrium Scheil solidification model provide insights into the solidification process and the underlying metallurgical factors associated with the observed microstructural evolution. The observations revealed that the pure Ni wire deposited a softer fusion zone with graphite precipitation, while cementite precipitated in the fusion zone of NiFe alloy. The formation of martensite structures with different morphologies was the predominant microstructural evolution in the heat-affected zone of both welds. The partially melted zone of the pure Ni weld is narrower than the NiFe weld because more diffusion of Ni avoids widening the brittle structures in the partially melted zone. An unmixed zone in the form of a peninsula was exclusively observed in the fusion zone of the NiFe weld because of inadequate diffusion of Ni into the liquified materials along the fusion boundary. [ABSTRACT FROM AUTHOR]

In this paper, the pre-oxidation products, surface silicon content, hot-dip galvanized layer structure and corrosion resistance of nodular cast iron pre-oxidized by sodium bicarbonate were studied by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction. When the pre-oxidation temperature is 100 °C, the pre-oxidation product is primarily Fe2O3. The oxidation products are Fe2O3 and SiO2 at 200 °C and that is mainly SiO2 at 300 °C. The surface silicon content of the pre-oxidized samples decreases first and then increases with increasing pre-oxidation temperature. The silicon content of samples after alkali and acid washing decreases with increasing pre-oxidation temperature. With the increase in pre-oxidation temperature, the thickness of the alloy layer in the zinc coating of nodular cast iron continuously decreases. The thickness of the alloy layer in the zinc coating of nodular cast iron pre-oxidized at 300 °C is only 37.3 μm, which is 43.9% lower than that of nodular cast iron without pre-oxidation. [ABSTRACT FROM AUTHOR]

The purpose of this study was to experimentally determine the abrasion wear properties of ausferritic ductile iron austempered at 250 °C in order to obtain cast iron of class EN-GJS-1400-1. It has been found that such a cast iron grade makes it possible to create structures for material conveyors used for short-distance transport purposes, required to perform in terms of abrasion resistance under extreme conditions. The wear tests addressed in the paper were conducted at a ring-on-ring type of test rig. The test samples were examined under the conditions of slide mating, where the main destructive process was surface microcutting via loose corundum grains. The mass loss of the examined samples was measured as a parameter characteristic of the wear. The volume loss values thus obtained were plotted as a function of initial hardness. Based on these results, it has been found that prolonged heat treatment (of more than 6 h) causes only an insignificant increase in the resistance to abrasive wear. [ABSTRACT FROM AUTHOR]

They also are a cost-effective material with good machinability, corrosion resistance, and vibration damping properties, as well as relatively high wear resistance, thanks to graphite's self-effect. Cast irons are widely used in industry due to their excellent castability, allowing for the production of near-net shape components with complex geometries without the need for additional forging or machining processes. The review suggests research directions to expand the application of HCCI and research directions and contents to enhance the corrosion wear resistance of these materials by modification, alloying and heat treatment methods. [Extracted from the article]

Nowadays, the best castings' manufacturers have to meet very demanding requirements and specifications applicable to mechanical properties and other characteristics. To fulfill those requirements, more and more sophisticated methods are being used to analyze the internal quality of castings. In many cases, the commonly used Non-Destructive Methods, like X-ray or ultrasonic testing, are not enough to ensure precise and unequivocal evaluation. Especially, when the properties of the casting only slightly fail the specification and the reasons for such failures are very subtle, thus difficult to find without the modern techniques. The paper presents some aspects of such an approach with the use of Scanning Electron Microscopy (SEM) to analyze internal defects that can critically decrease the performance of castings. The paper presents the so-called bifilm defects in ductile and chromium cast iron, near-surface corrosion caused by sulfur, micro-shrinkage located under the risers, lustrous carbon precipitates, and other microstructure features. The method used to find them, the results of their analysis, and the possible causes of the defects are presented. The conclusions prove the SEM is now a powerful tool not only for scientists but it is more and more often present in the R&D departments of the foundries. [ABSTRACT FROM AUTHOR]

Sewer pipeline failures pose significant threats to the environment and public health. To tackle these repercussions, many deterioration models have been developed to predict the conditions of sewer pipes, most of which are based on CCTV inspection reports. However, these reports are prone to errors due to their subjective nature and human involvement. More importantly, there are insufficient data to develop prudent deterioration models. To address these shortcomings, this paper aims to develop a CCTV-based deterioration model for sewer pipes using Artificial Intelligence (AI). The AI-based model relies on the integration of an unsupervised, multilinear regression technique and Weibull analysis. Findings derived from the Weibull deterioration curve indicate that the useful service life for concrete and vitrified clay pipes are 79 years and 48 years, respectively. The regression models show that the R2 value for vitrified clay sewer pipes, concrete sewer pipes, and ductile iron sewer pipes are 71.18%, 71.47%, and 81.51%, respectively, and 73.69% for concrete stormwater pipes. To illustrate the impact of various factors on sewer pipes, sensitivity analyses under different scenarios are conducted. These analyses indicate that pipe diameter has a significant influence on sewer pipe deterioration, with little impact on stormwater pipes. These findings would guide decision makers in identifying critical pipes and taking necessary precautionary measures. Further, this provides a sound basis for prioritizing maintenance actions, which would pave the way for designing sustainable urban drainage systems for cities. [ABSTRACT FROM AUTHOR]

The aim of this paper is to evaluate the fatigue resistance of austenitic nodular cast iron and to compare it with other types of nodular cast irons. The austenitic nodular cast iron, used for the experiments, was alloyed by 13% nickel and 7% manganese (EN-GJSA-XNiMn13-7) to obtain an austenitic matrix. The microstructure was studied using light metallographic microscopy. Mechanical properties were investigated by tensile test, impact bending test and Brinell hardness test. Fatigue tests were carried out at sinusoidal cyclic push-pull loading at ambient temperature. The results of fatigue tests were compared with the fatigue properties of ferrite-pearlitic nodular cast iron and pearlite-ferritic nodular cast iron. Experimental results show that NiMn-type of austenitic nodular cast iron has lower tensile strength and hardness, but higher elongation and absorbed energy than the compared types of nodular cast iron. However, austenitic nodular cast iron has lower fatigue limit. [ABSTRACT FROM AUTHOR]

Buried pipes comprise a significant portion of assets of a water utility. With time, these pipes inevitably fail. Failure prediction enables infrastructure managers to estimate long-term failure trends for budgetary planning purposes and identify critical pipes for preventive intervention planning. For short-term prioritization, machine learning based algorithms appear to have superior predictive performance compared to traditional survival analysis based models. These models are typically stratified by material resulting in the exclusion of newer pipe materials such as polyethylene and corrosion-protected ductile iron, despite their prevalence in modern networks. In this paper, an application of an existing methodology is presented to estimate time to next failure using artificial neural networks (ANNs). The novelties of the approach are 1) including material as an input parameter instead of training several material-specialized models and, 2) addressing right-censored data by combining soft and hard deterioration data. The model is intended for use in short-term prioritization. [ABSTRACT FROM AUTHOR]

This article is a tribute to Richard (Rick) Gundlach, a highly accomplished metallurgical engineer who made significant contributions to the metalcasting industry. Rick received numerous awards and honors for his work, including the Joseph S. Seaman Gold Medal and the AFS Award of Scientific Merit. He was also a Fellow of the American Society of Materials. Throughout his career, Rick published over 70 technical papers and held two U.S. patents. His passion for metallurgy, metalcasting, and educating others was evident in his work and will continue to inspire the industry. The article also includes Rick's two final papers, which were submitted on his behalf by his colleague, Dr. John Tartaglia. The papers focus on the effects of silicon in high-Cr white cast irons and achieving higher strength and ductility in heavy-section ductile iron castings. Rick's contributions to the industry will be greatly missed. [Extracted from the article]

Microstructural characteristics and mechanical properties of the ductile iron in three heat treatment processes (normalizing, quenching + high‐temperature tempering and isothermal quenching) were investigated in this paper. The pearlite and ferrite with large‐sized spherical graphites can be obtained in the normalized sample, and the spherical graphites with relatively large size can still be observed in the mechanical mixture of tempered martensite and acicular ferrite for the quenched‐tempered sample. Meanwhile, the lower bainite accompanied with the relatively fine spherical graphites are existed in the isothermal‐quenched sample. The difference of tensile strength is mainly caused by the phase composition, distribution and size of the spherical graphites and the effect of the solid solution strengthening. The weaker degree of the debonding damage, higher proportion of high‐angle grain boundaries will improve the impact toughness of the ductile iron. In a word, the optimum combination of strength and toughness is acquired by using isothermal quenching, and the tensile strength and impact toughness are ~1350 MPa and ~10.62 J, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the ferrite grain size was controlled by two annealing methods, which can affect the low-temperature toughness of ferrite nodular cast iron. The annealing temperature ranged from 720 to 750 °C, and one annealing method consisted of constant temperature heating with temperature controlled to ± 1 °C. The other method employed cyclic heating, with a temperature change of 19 (+ 14, − 5) °C and a period of 450 s. The change law of ferrite grain size under low temperature annealing and the effect of ferrite grain size on low-temperature impact toughness were studied. The conditions under which the superheated ferrite does not transform into austenite were determined. The mechanism by which coarse ferrite favors high toughness in nodular cast iron at low temperatures was discussed. Nodular cast iron with tensile strength of 392 MPa, yield strength of 206 MPa, elongation of 26% and impact energy of 13.5 J at − 70 °C was obtained. [ABSTRACT FROM AUTHOR]

This paper will present results of a thorough evaluation of the effects of (1) 'plain' thermal analysis (TA) cup (aka 'eutectometer' cup, as coined by Heine in AFS Trans 78:187–193, 1970; AFS Cast Metals Res J 7:49–54, 1971; AFS Trans 80:462–470, 1973) design/geometry (square vs. round), (2) 'before' and 'after' paper cup inoculation of plain TA cup, (3) inoculant type, and (4) inoculant dosage on the resultant TA metrics and microstructure characteristics as quantified by image analysis metallography of treated and inoculated ductile iron. Since production castings have near-infinite shapes and sizes, there is often a large variation in the types and dosages of inoculants employed by ductile iron casting producers. Thus, the evaluations of this paper are important in quantifying the proportions of gage variation (discriminating capability) for all independent and interactive combinations of the foregoing four predictor variables. That is, the gauge variation for any combination of predictor variables must be sufficiently low to make any valid assessment(s) of them having significant effects on the responses of TA metrics and microstructure characteristics. Further analysis was done in probing for any significant correlations between TA metrics and the ultrasonic velocities and quantified microstructure characteristics of both mold-cooled and water-quenched coupons after casting, with presentation of results for the significant correlations. When GR&R variation for the effects of any combination of all the TA predictor variables is sufficiently low, we can then make valid assessment(s) of their effects on and correlations to ultrasonic velocity and digital metallographic image analysis metrics of test coupons that were cast simultaneously with TA cups in multiple sets cast from a single sample spoon. [ABSTRACT FROM AUTHOR]

The article discusses issues related to the melting of grey and ductile cast iron in terms of metallurgical quality. The derivative and thermal analysis (DTA) was used to assess this quality. The article presents the results of research carried out in industrial conditions and analysed by the Itaca system. In the paper, the effect of the furnace type, the charge materials and the inoculation process on the parameters characterising the cast iron being melted was analysed. The most important of these are the minimum eutectic temperature (Temin), the liquidus temperature (Tliquidus) and the nucleation rate. The results of the research and calculations are shown in graphs and as dependencies. Some of DTA results were compared to the microstructure analysis results. The article shows that the derivative and thermal analysis is a very effective tool in the assessment of the metallurgical quality of cast iron. It is a very good addition to chemical analysis. Based on the results of the research, it was concluded that a very high correlation exists between the rate of nucleation (DTA) and the number of graphite nuclei (microstructure analysis). Furthermore, it was also found that an improvement in nucleation could be achieved by ensuring a high value of carbon equivalent (CE) and, above all, by conducting the primary and secondary inoculation processes, respectively. [ABSTRACT FROM AUTHOR]

The goal of the present paper is to discuss the accuracy and reliability of a procedure for the fatigue strength estimation of defective metals by considering some experimental data available in the literature. In particular, the fatigue behaviour of three ductile cast irons (DCIs) containing solidification defects (i.e., micro-shrinkage porosity) is simulated through the above a procedure, based on the joined application of the a r e a -parameter model and the Carpinteri et al. multiaxial fatigue criterion. The fatigue strength of such DCIs subjected to both uniaxial (rotating bending or torsion) and biaxial (combined tension and torsion) cyclic loading is evaluated and compared with the experimental results. [ABSTRACT FROM AUTHOR]

Ductile cast iron is also called spheroidal graphite cast iron or nodular cast iron. It contains graphite in the semblance of nodules. Automobile scrap (i.e., the engine block) made from gray cast iron was used in this study. In this paper, the recycling of gray cast iron to ductile iron, and its influence on the microstructure and mechanical characteristics be studied. Four kilograms of scrap were put in a crucible and then heated up to 1400°C in an oil-fired crucible furnace. For desulfurization, 4% burnt lime with 0.5% fluorspar was direct tapped into the melt at 1400°C. Then, the additions were 3.5% nickel, 0.75% ferro molybdenum, and 0.5% ferro manganese of the scrap weighing. Also, 3.75% nodularizing alloy and 1% inoculating alloy of scrap weight were to treat the molten at 1450°C. Samples analyses have been achieved to determine their composition, tensile strength, impact strength, Brinell hardness, and microstructural. The microstructures revealed that the scrap sample possesses flake graphite, and the produced sample includes nodule graphite. It is observed that the ultimate tensile stress, elongation and hardness of the scrap sample, which are 247.75 MPa, 6% and 400.3 HB, respectively, increased in the product sample to 416.23 MPa, 8% and 451 HB, respectively. [ABSTRACT FROM AUTHOR]

Ductile iron is a high-strength cast iron material. The spherical graphite obtained by inoculation treatment effectively improves the mechanical properties of cast iron, resulting in higher strength than carbon steel. However, severe corrosion may occur under specific circumstances, especially in thermal water pipelines. In this paper, the corrosion mechanisms at the main defective points of ductile iron were investigated using microscopic morphological characterization after accelerated tests combined with numerical simulations. The influence law of each environmental factor on the corrosion kinetics of ductile iron in a complex water quality environment was studied using dynamic potential polarization tests. The results showed that the main causative factors leading to the increased corrosion of ductile iron were the presence of tail-like gaps on its surface, and the crescent-shaped shrinkage and loosening organization around the graphite spheres. After mechanical treatment was applied to eliminate the obvious defects, the number of corrosion pits was reduced by 41.6%, and the depth of the pits was slowed down by 40% after five days. By comparison, after ten days, the number of pits was reduced by 51%, and the depth of the pits was slowed down by 50%. The dynamic potential polarization test results show that the dissolved oxygen concentration has the greatest influence on the corrosion of ductile iron in the simulated water environment; meanwhile, the water hardness can slow down the corrosion of ductile iron. The relative influence of each environmental factor is as follows: dissolved oxygen concentration > temperature > immersion time > water hardness > pH > Cl−. [ABSTRACT FROM AUTHOR]

To remain competitive in this growing field of the manufacturing industry, there is a need to reduce the lead times in the development of a component. The virtual simulation environment tool can be utilised for minimising production time as well as assure defect-free casting. This technique is based on heat transfer and volumetric calculations for prediction of possible defects. In this paper, analysis of automobile impeller casting is explored. The modelling of the casting and feeding system is done using the CATIA software. The CAD model of the impeller is imported into the simulation environment for solidification simulation. The simulation is performed using SolidCAST software which is based on the Finite Difference Method. The simulations are performed to ensure proper feeding for achieving sound casting. The melting trials are performed in jobbing foundry. The hardness and microstructure analysis of simulated and experimental casting is performed so as to correlate. The section thickness and cooling rates in casting were analysed and used for formulating hardness and microstructure in the experimental castings. The statistical predictions based on simulated and experimental results are presented for formulating Brinell hardness and amount of pearlite phase in particular section of shell moulded ductile iron casting. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents an assessment of the possibility of using digital image classifiers for tomographic images concerning ductile iron castings. The results of this work can help the development of an efficient system suggestion allowing for decision making regarding the qualitative assessment of the casting process parameters. Special attention should be focused on the fact that automatic classification in the case of ductile iron castings is difficult to perform. The biggest problem in this aspect is the high similarity of the void image, which may be a sign of a defect, and the nodular graphite image. Depending on the parameters, the tests on different photos may look similar. Presented in this article are test scenarios of the module analyzing two-dimensional tomographic images focused on the comprehensive assessment by convolutional neural network models, which are designed to classify the provided image. For the purposes of the tests, three such models were created, different from each other in terms of architecture and the number of hyperparameters and trainable parameters. The described study is a part of the decision-making system, supporting the process of qualitative analysis of the obtained cast iron castings. [ABSTRACT FROM AUTHOR]

Ferritic high-Si ductile cast irons replace an unstable mixed ferrite-pearlite matrix with a unique combination of high elongation, strength and hardness (ideal for automotive drive train components) and resistance to oxidation and corrosion at high temperatures (automotive exhaust and turbocharger systems). The present paper analyses the graphite parameters of 4.5%Si, un-inoculated ductile cast iron (4.7%CE, 0.035%Mgres) as an effect of the casting section size. The structure is characterized by 10.5–11.2% graphite and 464–975 nodules/mm2, at more than 70% ferrite and no carbides, including at 3 mm wall thickness. The lower the wall thickness is, the higher the nodule count is and, consequently, the higher the ferrite amount is. The Roundness Graphite Shape Factor (RSF = 0.65–0.68) illustrates the presence of Slightly Irregular Spheroidal Graphite (Form V ISO 945). There is a big difference between the graphite nodularity evaluated according to ISO 16112:2017 [CGI] (NG1 = 79–86%) and according to ISO 945-4-2019 (DI) (NG2 = 65.2–74.6%), both of them based on RSF. Graphite Nodularity (NG3), calculated with the ISO 945-4-2019 [DI] formula, but replacing RSF with SSF, Sphericity Graphite Shape Factor, has an intermediary position. The higher the imposed minimum RSF or SSF is, the lower the Graphite Nodularity (NG4, NG5): 80–90% for min. 0.50 (minimum Form IV or Intermediate Graphite), 60–80% for min. 0.60–0.65 (minimum Form V graphite) and 35–70% for min. 0.80 (minimum Form VI graphite). The SSF is more representative than the RSF for Si-alloyed ductile cast iron, so it is recommended to use a graphite nodularity calculus considering SSF instead of the RSF formula (stipulated by ISO 945-4-2019), with SSF replacing RSF. [ABSTRACT FROM AUTHOR]

Throughout many parts of the world, cast iron pipe has been and continues to be used for utility piping (water and sewage) and gaseous media piping. Gray cast iron is known to have a limited life in service but is often left in place beyond its reasonable service life. Therefore, end of life is then left to be defined as a rupture or a crack and a subsequent leak, often at an unpleasant time with unpleasant results. The controlling mechanism involved is time dependent and known as graphitic corrosion. This paper provides a review of the phenomenon of graphitic corrosion in the form of key characteristics. Several references are cited that further explore the mechanism involved and corrosion prevention/mitigation. Two case studies are presented that explore graphitic corrosion in gray cast iron pipe from a failure analysis point-of-view. Both case studies feature conditions that further aid in the interpretation of graphitic corrosion and an appreciation for when and how this phenomenon occurs. [ABSTRACT FROM AUTHOR]

This work is a continuation of the studies presented in a recent paper by the authors, where a methodology to obtain different nodule quality categories in spheroidal graphite cast iron, was proposed. In this study, an exhaustive analysis of the highest-quality graphite nodules was performed. The experimental methodology involves X-ray micro-computed tomography analysis and digital image post-processing of the high-quality graphite nodule population. Furthermore, different subpopulations were selected, following a nodular size criterion. The procedure involves the evaluation and comparison of the sphericity and compactness distributions and the distances between neighbouring nodules by using ad-hoc image processing software. The results reveal the complementary nature of the sphericity and compactness parameters, which allow classifying, with great accuracy, different nodular quality categories of spheroidal graphite cast iron. Additionally, new viewpoints about the nodular morphology study and the distribution of quality nodules in the metallic matrix were provided, which could be extended to other heterogeneous materials. [ABSTRACT FROM AUTHOR]

The rotors of submersible wastewater pumps, generally made of nodular graphite cast iron, are subjected to complex processes of corrosive erosion during operation. To improve the characteristics of erosion resistance by impact with solid particles in the corrosive environment of wastewater, cast iron was subjected to a chemical phosphating treatment. In the paper, the scratch test behaviour of nodular cast iron and phosphate nodular cast iron is analysed comparatively, studying the behaviour of the deposited layer and its adhesion to the substrate. The nanoindentation characteristics of nodular cast iron and phosphate nodular cast iron were also studied. It was observed that the deposited layer is not compact, but when pressed, it does not crack and does not detach from the substrate; it is impregnated in the substrate in the metal matrix, but not on the area with carbon nodules. The SEM micrographs show that the deposited phosphate layer is relatively porous and can change the behaviour of the liquid flow moving on the surface of the rotor due to its hydrophilic behaviour; this also allows the formation of a boundary layer that adheres to the surface of the rotor and protects it from the impacts of microparticles driven by the liquid stream. [ABSTRACT FROM AUTHOR]

In the present paper, a procedure for fatigue strength assessment of metals containing solidification defects is employed to analyze the fatigue behavior of a ductile cast iron (DCI) characterized by a relevant micro‐shrinkage porosity. The procedure implements (i) a statistical method deriving from extreme value theory, (ii) the area‐parameter model, and (iii) the multiaxial critical plane‐based criterion by Carpinteri et al. According to the above statistical method, both the distribution of defects and the return period are determined. More precisely, the return period is computed by also exploiting a relationship here proposed to optimize the accuracy of the procedure in terms of fatigue strength estimation. The great potential of the present procedure is that the defect content analysis (performed by means of a statistical method deriving from extreme value theory) can be easily performed using machine learning techniques. HIGHLIGHTS: A procedure for fatigue assessment of metals with solidification defects is employed.The fatigue behavior of a DCI with a relevant micro‐shrinkage porosity is analyzed.A defect content analysis is performed by means of a statistical method deriving from EVT.The return period is computed by a relationship that optimizes the procedure accuracy. [ABSTRACT FROM AUTHOR]

With a long history of more than 600 years of development, the Achang Tosa knives have always been handmade and made in strict accordance with tradition and absorbing the essence of foreign cultures. It is not only a tool or a gift, but also a "knife culture" and a local "folk culture" with local ethnic characteristics in Yunnan. In this paper, we begin our research on the Achang Tosa knives by compiling literature and conducting field research to investigate the "knife culture" jointly created by the Achang and neighboring ethnic groups by studying the forging process of the Achang Tosa knives. Three sets of specimens were prepared and the mechanical properties were determined by combining the existing isothermal quenched ductile iron (ADI) material production, and a high-speed cutting test was carried out with a CC650 ceramic tool to investigate the relationship between the machined material, tool material, and cutting dosage-surface roughness during high-speed cutting of ADI; based on the particle swarm algorithm, a theoretical model between surface roughness and cutting parameters was established to provide theoretical guidance for the optimal production process of ADI in high-speed cutting. It provides more valuable experience for the protection of intangible cultural heritage of ethnic minorities and also provides reference for the development and protection of unique crafts of other ethnic minorities. [ABSTRACT FROM AUTHOR]