Search Results (137)

Additive manufacturing (AM) has brought significant breakthroughs to the construction sector, such as the ability to fabricate complex geometries, enhance efficiency, and reduce both material usage and construction waste. However, several challenges must still be addressed to fully transition from conventional construction practices to innovative and sustainable green alternatives. This study investigates the use of non-cementitious traditional mixtures for green construction applications through 3D printing using Liquid Deposition Modeling (LDM) technology. To explore the development of mixtures with enhanced physical and mechanical properties, natural pine and cypress wood shavings were added in varying proportions (1%, 3%, and 5%) as sustainable additives. The aim of this study is twofold: first, to demonstrate the printability of these eco-friendly mortars that can be used for conservation purposes and overcome the challenges of incorporating bio-products in 3D printing; and second, to develop sustainable composites that align with the objectives of the European Green Deal, offering low-emission construction solutions. The proposed mortars use hydrated lime and natural pozzolan as binders, river sand as an aggregate, and a polycarboxylate superplasticizer. While most studies with bio-products focus on traditional methods, this research provides proof of concept for their use in 3D printing. The study results indicate that, at low percentages, both additives had minimal effect on the physical and mechanical properties of the tested mortars, whereas higher percentages led to progressively more significant deterioration. Additionally, compared to molded specimens, the 3D-printed mortars exhibited slightly reduced mechanical strength and increased porosity, attributable to insufficient compaction during the printing process. Full article

This study investigates hazardous emissions from foundry binder systems, comparing organic resins (phenolic urethane, furan, and alkaline-phenolic) and clay-bonded green sand with inorganic alternatives (sodium silicate and geopolymer). The research was conducted at the Fundaciόn Azterlan pilot plant (Spain), involving controlled chamber tests for the production of 60 kg iron alloy castings in 110 kg sand molds. The molds were evaluated under two configurations: homogeneous systems, where both mold and cores were manufactured using the same binder (five trials), and heterogeneous systems, where different binders were used for mold and cores (four trials). Each mold was placed in a metallic box fitted with a lid and an integrated gas extraction duct. The lid remained open during pouring and was closed immediately afterward to enable efficient evacuation of casting gases through the extraction system. Although the box was not completely airtight, it was designed to direct most exhaust gases through the duct. Along the extraction system line, different sampling instruments were strategically located for the precise measurement of contaminants: volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), phenol, multiple forms of particulate matter (including crystalline silica content), and gases produced during pyrolysis. Across the nine trials, inorganic binders demonstrated significant reductions in gas emissions and priority pollutants, achieving decreases of over 90% in BTEX compounds (benzene, toluene, ethylbenzene, and xylene) and over 94% in PAHs compared to organic systems. Gas emissions were also substantially reduced, with CO emissions lowered by over 30%, NO_x by more than 98%, and SO₂ by over 75%. Conducted under the Greencasting LIFE project (LIFE 21 ENV/FI/101074439), this work provides empirical evidence supporting sodium silicate and geopolymer binders as viable, sustainable solutions for minimizing occupational and ecological risks in metal casting processes. Full article

This study presents a simulation modeling of the gravity filling of a sand casting mold with gray cast iron EN-GJL-250. An analysis of the fluid flow, the nature of the filling of the casting mold, and the possibility of forming defects, such as voids and porosity due to metal shrinkage during the crystallization process, was performed. The simulation was performed using specialized software for simulating metal casting processes. The software allows the modeling of fluid dynamics and thermal conditions during the filling of the casting mold. The results obtained show the influence of the design of the sprue system, pouring temperature, and casting geometry on the movement of the fluid flow and the crystallization of the metal. The simulation also allows the visualization of turbulence and temperature gradients, helping to localize areas prone to defects. The results of this study could improve the quality of the specific casting and aid in selecting appropriate technology for the casting of a small series of high-quality castings. Full article

Traditional sand casting is limited by mold fabrication, cost control, and data collection, which restrict its further advancement. However, 3D sand printing technology represents a sophisticated rapid prototyping approach that directly utilizes three-dimensional models to fabricate complex sand molds and cores, thereby bypassing the traditional mold-making steps. This technology significantly enhances production efficiency and design flexibility, thereby advancing the modernization of casting processes. In the context of wind tunnel testing, the application of 3D-printed sand shell additive manufacturing has successfully produced sand molds and cores for the non-axisymmetric intake duct structures. This demonstrates the feasibility of this technology for complex casting applications and its capability to meet experimental requirements. Full article

To address the challenge of imprecise micro-droplet formation control in piezoelectric jetting devices used in sand mold 3D printing and apply on-demand inkjet printing technology to sand mold manufacturing, this study first explains the working principle of a piezoelectric shear-mode printhead. A mathematical model of the droplet ejection process is then established based on Computational Fluid Dynamics (CFD). Building upon this model, numerical simulations of droplet generation, breakup, and flight are conducted by using the Volume of Fluid (VOF) model within the Fluent module of the Workbench 2020 R2 platform. Finally, under consistent driving conditions, the effects of key parameters—viscosity, surface tension, and inlet velocity—on the ejection process are investigated through simulation. Based on the results, appropriate ranges and recommended values for ink properties are determined. This study provides significant engineering value for improving the stability and precision of droplet formation in industrial sand mold 3D printing. Full article

Sand mold milling plays a critical role in digital mold-free casting, but it is prone to damage such as corner collapse, collapse, and cracks during the machining process. To address this issue, ultrasonic vibration was used for sand mold milling in this study. By incorporating the solid–liquid transition model for sand mold cutting and considering the deformation characteristics of the shear zone, a prediction model for ultrasonic milling forces in sand mold was developed and experimentally validated. The results demonstrate that increasing the spindle speed and decreasing the feed rate lead to a decrease in cutting force. At high speeds, there is a 15% error between the dynamic milling force model and experimental values. Compared with conventional processing methods, ultrasonic processing reduces cutting force by 19.5% at a frequency of 25.8 kHz and amplitude of 2.97 μm, minimizes defects like sand particle detachment pits on the surface of sand mold, significantly improves surface quality, and enables precise, stable, high-precision, and efficient sand mold processing. Full article

This study developed a high-performance composite mortar with a low water-to-binder (W/B) ratio to improve the mechanical strength and volumetric stability of preplaced aggregate concrete-filled steel tubes (PACFST). Silica fume was incorporated to optimize the interfacial transition zone (ITZ) between the matrix and coarse aggregates. The effects of the sand-to-binder (S/B) ratio, water-to-binder (W/B) ratio, and expansive agent content on the flowability, compressive strength, and volume stability of the composite mortar were systematically analyzed. Experimental tests were conducted using vibration-free molded specimens, and the influence of different S/B ratios (0.8–1.4), W/B ratios (0.26–0.32), and expansive agent dosages (0–8%) on mortar properties was evaluated. The results indicate that an optimal S/B ratio of 1.2 significantly enhances flowability and strength, whereas further increases offer limited improvement. Reducing the W/B ratio enhances strength, with a decrease from 0.32 to 0.28 leading to a 23.4% increase in 28-day compressive strength. Additionally, a 6% expansive agent dosage reduces 90-day shrinkage by 13.1% while maintaining high compressive strength. The optimized PAC achieved a 28-day compressive strength of 115.9 MPa, with an 11.6% increase in 7-day strength and a 51.2% reduction in 90-day shrinkage compared to conventional C100 concrete. These findings provide theoretical guidance for designing high-strength, low-shrinkage PAC, offering insights for bridge, tunnel, and high-rise building applications. Full article

Binder jetting is the most widely implemented additive technology for the fabrication of sand molds. However, the use of furan binder-jetting technology in the production of molds for vacuum casting is hindered by the thermal destruction of the furan binder accompanied by violent gas emission that occurs during the mold heating process. This investigation explores the potential of using the molds obtained via furan binder jetting 3D printing and further impregnation in colloidal silica binder and sintering. Two distinct sands, proppant and cenosphere, were utilized in the fabrication of the mold components exhibiting different thermal properties. An examination of the structure of the initial sands and samples produced via different impregnation and sintering regimes was conducted via scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffractometry, thermogravimetric analysis, and micro computed tomography. Furthermore, the bending mechanical properties and linear shrinkage of the samples were determined. The experimental findings demonstrated that the specific impregnation and sintering regimes examined in this study yielded sufficient mechanical properties for the casting molds and the structure with cristobalite bridges. The mold assembly, composed of proppant and cenosphere sands-based parts, was produced, and impeller nickel-based superalloy castings were fabricated. The findings of this study demonstrate that the utilization of a furan binder-jetting technique, in conjunction with impregnation in colloidal silica binder, is a promising technology for the manufacture of high-melting-temperature alloy casting. Full article

This study investigates the influence of casting thickness on the cooling rate of gray cast iron using metal molds and compares it to the cooling rate achieved with traditional sand molds. Sand molds represent the oldest and most widely used method in metal casting, while metal molds are a relatively newer application for gray cast iron. The cooling rates during solidification were monitored using thermocouples connected to a data logger. The smelting of gray cast iron was performed in an induction furnace, with some samples inoculated using FeSi and FeMn additions, while others were cast without inoculation. This study analyzed the chemical composition, microstructure, hardness, and surface morphology of gray cast iron through SEM-EDS for both inoculated and non-inoculated samples. The results indicate that FeSi and FeMn inoculation enhanced the carbon content of the cast iron. Additionally, while the differences in cooling rate due to the casting thickness in permanent metal molds were not substantial, a distinct pattern emerged. The mid-thickness regions exhibited the highest cooling rates, which influenced the hardness distribution across the castings. This research highlights the nuanced effect of the mold type and casting thickness on the cooling dynamics and mechanical properties of gray cast iron. Full article

This study investigates the development and application of climate friendly processes in the foundry industry, particularly with regard to the use of inorganic binders to reduce emissions and pollution. An inorganic binder system based on water glass, which is used in 3D printing technology for the production of sand molds and core, is being tested and the possibility of determining a kinetic model for the curing kinetics of sodium silicate as an inorganic binder is investigated. The aim is to use a kinetic model to better describe the microwave process currently required in binder jetting for drying the binder and catalyzing the chemical reaction of the binder during curing. For sodium silicate in particular, there is still no scientific knowledge available in this respect, which is why basic investigations based on thermogravimetry or heat flow difference calorimetry must first be carried out. In this way, it should be possible to simulate the drying process in the microwave, which has so far been based on empirical values, in order to maximize the efficiency of this process and also the quality of the components. The results indicate that the weight loss and weight changes depend on the heating rates and that a heating rate of 30 K/min is not sufficient to fully cure the sample at 500 °C. The thermogravimetric analysis (TGA) shows that the fastest weight loss occurs at the beginning of the measurement, indicating a partial pre-curing of the sample before the measurement. From the measurements, an average activation energy of 144.18 kJ/mol could be determined using the Friedman method and 123.36 kJ/mol and 123.31 kJ/mol using the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods, respectively. Measurements of the heat flow at a heating rate of 30 K/min indicate partially exothermic reactions during the curing process. Full article

A large-sized backward-curved fan with high shape difficulty was designed, and fan performance was roughly predicted from computational fluid dynamics. Three gating systems of aluminum sand casting were designed to fabricate the fan. The flow pattern and solidification process of molten metal were analyzed by casting simulation. Three types were applied: bottom-up with four gates, bottom-up with ten gates, and top-down with a feeder. The simulation results of the bottom-up with four gates show that a large temperature loss occurs while molten metal flows into thin blades, and there is a temperature range below the liquidus temperature. Due to nonuniform temperature distribution, the solidification pattern is also not uniform. The bottom-up with ten gates shows almost similar flow and solidification patterns but has the effect of slightly reducing the temperature loss of molten metal. The top-down type has a much smaller temperature loss, while molten metal flows into the mold cavity compared to the bottom-up type and has a directional solidification pattern. As the feeder also acts as a riser to compensate for the shrinkage of the thick part, the simulation results regarding porosities are also significantly reduced. The fan cast as a top-down type has soundness without any unfilled parts. Full article

Foundries generate millions of tons of waste annually, posing a challenge to companies that generate it and to the environment due to landfill disposal. Meanwhile, the construction sector contributes heavily to global resource consumption. Adopting a circular economy approach by integrating foundry wastes into construction materials offers two main benefits: reducing landfill accumulation and preserving natural reserves of raw materials while also supporting the UN’s Sustainable Development Goals. This paper presents a review of recent studies on the use of foundry wastes in construction materials and provides an overview of the foundry industry, including its background, waste management, and statistics. Furthermore, a bibliometric analysis highlights the evolution of research in this area, showing a 182% increase in publications over the last 10 years. Key findings include that waste foundry sand is the most widely utilized foundry waste in construction materials, while ceramic mold shells and paraffin waxes remain underexplored. Concrete is the primary material incorporating foundry waste. The incorporation of foundry waste into construction materials improves durability and mechanical strength when used in appropriate proportions. The replacement content can reach up to 100%. These results underscore the feasibility of foundry waste as a sustainable alternative in construction, building circularity, and reducing environmental impact. Full article

Molding sand mixtures in the foundry industry are typically composed of fresh and reclaimed sands, water, and additives such as bentonite. Optimizing the control of these mixtures and the recycling of used sand after casting requires an efficient in-line monitoring method, which is currently unavailable. This study explores the potential of an AI-enhanced electrical impedance spectroscopy (EIS) system as a solution. To establish a fundamental dataset, we characterized various sand mixtures containing quartz sand, bentonite, and deionized water using EIS in the frequency range from 20 Hz to 1 MHz under laboratory conditions and also measured the water content and density of samples. Principal component analysis was applied to the EIS data to extract relevant features as input data for machine learning models. These features, combined with water content and density, were used to train regression models based on fully connected neural networks to estimate the bentonite content in the mixtures. This led to a high prediction accuracy (R² = 0.94). These results demonstrate that AI-enhanced EIS has promising potential for the in-line monitoring of bulk material in the foundry industry, paving the way for optimized process control and efficient sand recycling. Full article

Spheroidal graphite cast iron, which is commonly used in a variety of applications, is subject to sliding wear and tear during operation. This damage can be prevented by increasing its strength value. In this study, 0%, 0.191%, and 0.304% niobium-reinforced spheroidal graphite cast irons were produced. Specimens for hardness, compression, and abrasion tests were produced in accordance with the standards for the tests of the sand mold cast specimens. In order to compare the results of the tests, test specimens reinforced with 0.191% and 0.304% niobium, as well as 0% (unreinforced), were also produced. The hardness and compression strength of the niobium-reinforced and unreinforced specimens were tested in accordance with the standards. In addition, wear tests were carried out at 5 N, 10 N, and 15 N loads for 0%, 0.191%, and 0.304% niobium reinforcements, respectively. In the hardness tests, the highest measured value was observed in the sample reinforced with 0.304% niobium, with an average of 272 HB. Since Nb is an element with high hardness, the hardness values of the samples increased with the increase in Nb reinforcement. With an average value of 1411 MPa, the niobium-reinforced sample with 0.191% niobium reinforcement exhibited the highest compression strength. When analyzing the results of the compression tests, an increasing trend was observed with increasing reinforcement ratio, as was the case with the results of the hardness tests. In the wear tests, the changes in wear volume, wear rate, and friction coefficients were examined at loads of 5 N, 10 N, and 15 N. When the test specimens with the same reinforcement ratio were examined, it was found that the wear volume loss values increased with the increase in load. As the wear resistance increases with increasing hardness value, it becomes more difficult to detach the particles from the wear surfaces. The wear volume of the samples, therefore, decreases as the hardness value increases. At the end of the experimental study, a microstructural analysis of the surfaces subjected to sliding wear was carried out. It was observed that wear marks and pits had formed on the surfaces subjected to sliding wear. Full article

In the case of desulfurization and spheroization of cast iron using the in-mold method, in which the treated cast iron is poured into the reaction chamber and placed in the casting mold, the mineral raw material of the mold should support these processes. Therefore, it is important to know the physicochemical properties of the materials selected for the production of casting molds and to learn about the phenomena occurring during their pouring. The research presented in this paper was carried out on quartz, magnesite, chromite, and olivine sands. The results not only provide a comprehensive understanding of these materials but also have significant implications for reactor housing casting. Two of the three tested quartz sands meet all the standards, allowing quartz raw materials to be foundry sands. Marked by the authors of this work, P11 sand, which is classified as 1K grade by the seller, does not meet the requirements of the Polish standard PN-85/H-11001 for this grade and should be classified as 2K grade. At the same time, attention was drawn to relatively considerable weight losses at 1350 °C for the tested quartz raw materials. More significant losses on ignition were found for magnesite sand than the value permitted by the Polish standard, which should be associated with the fact that derivatographic tests were carried out in an oxidizing atmosphere. In the analysis made for olivine sand, the obtained data indicated that the magnesium content is slightly below the requirements of the relevant standard; on the contrary, the iron content exceeds the standard requirements. Analytical data obtained for chromite sand indicated that it meets the PN-91/H-11007 standard regarding chemical composition, but X-ray diffraction tests showed that the tested sample is not chromite but magnesiochromite. The results of grain size distribution, chemical composition, X-ray diffraction, SEM/EDS, and TG/TG presented in this paper show that before starting the production of a specific molding mixture, each time most of the parameters characterizing sand used should be controlled because the properties may differ from the manufacturer’s declaration. Full article