Sand Cores Research Articles

Prediction of intrusive gas pores caused by resin burning in sand core for iron castings

Prediction of intrusive gas pores caused by resin burning in sand core for iron castings

Investigations of the Cold Box Core Curing Stage Using an Augmented Simulation Approach

AbstractFoundry sand cores are used to produce complex metal castings. They are manufactured on universal coremaking machines in two distinct stages, shooting and curing. Various simulation tools exist to optimize the coremaking process. Numerical modeling of the two distinct process stages is challenging as it involves different tooling, raw materials, and process parameters. Additionally, each stage requires appropriate mathematical modeling of the fluid flow since the relevant physical phenomena are different. The state-of-the-art combined simulation approach (CA) can simulate these two stages in sequence using a Core shooting & curing module. The gassing system (GS) is also important to consider when calculating the complete physical mass flow during the curing stage in CA. An augmented simulation approach (AA) is proposed, which can include GS in the coremaking simulations. This approach enables the execution of two-stage combined simulations (CA) using Magma C + M software (SW1) and incorporates GS data using FLOW-3D CAST software (SW2). In order to analyze the influence of including selected factors such as the hopper during the shooting stage and GS during the curing stage, the simulation approaches CA and AA were compared. The simulation results were correlated with experiment results (EX) to analyze sand density distribution and different curing times, focusing on the final core quality. Quantity analysis has been done among EX samples to observe the cured core trend. The results obtained from AA exhibit a significantly better correlation with EX than with CA. The proposed augmented approach offers significant potential for the improved analysis, optimization, and accurate prediction of complex coremaking processes within polyurethane (PU) Cold Box Systems.

Enhancing the performance of paraffin's phase change material through a hybrid scheme utilizing sand core matrix

Smart waste management and valorisation is presented in the current investigation. Iron is collected from mining wastewater stream and augmented with sand as a supporting material to produce sand core. The sand core pellets encapsulated in paraffin’s to enhance its feasibility as phase change material (PCM). Sand core was characterized using X-ray diffraction and Scanning Electron Microscope (SEM) augmented with energy dispersive X-ray spectrum analysis. Experimental test is achieved by mixing sand core/iron and paraffin that is signified as an encapsulated phase change material. The encapsulated sand core-PCM is embedded in varies mass weights of percentages of 0.5, 1.0, 1.5 and 2.0% and labeled as 0.5%-sand core-PCM, 1.0%-sand core-PCM, 1.5%-sand core-PCM and 2.0%-sand core-PCM. The encapsulated sand core-PCM is embedded into a heat exchanger of the vertical type model that is connected with a flat plate solar collector. Such collector is heating the heat transfer carrier, which is exposed to the heat exchanger for melting the PCM. The experimental work is conducted across the solar noon where the solar intensity in the region is reached to 1162 W/m2 at the time of conducting experiments. Water is applied and supposed as the working heat transfer fluid transporter and pumped into the system at the rate of 0.0014 kg per second. The experimental result revealed that the heat gained recorded an enhancement from 7 to 48 kJ/min when the 1.5%-sand core-PCM system is applied. Thus, the results showed the system is a good candidate by increasing the system efficiency with 92% as a potential solution of solar energy storage at the off-time periods.

Characterisation of the Decoring Behaviour for Furan Resin Bonded Sands Using DEM Simulation

Sand cores and moulds form the inner and outer structures of casting parts with tolerances of up to a few tenths of a millimetre. These must fulfil two complementary characteristics. During casting, they must withstand the high thermal and mechanical loads and subsequently disintegrate without leaving any residue. The production of these mostly organically bonded cores and moulds is done with conventional manufacturing processes, such as core shooting, or what is becoming increasingly more important for foundries, using 3D printing. In order to better understand this complex disintegration behaviour of these different core types and thus minimise the enormous energy input for their removal, a suitable simulation model based on discrete element methods (DEM) is considered as a tool to describe and further analyse the prevailing complex interactions in more detail. This contribution discusses the characterisation of furan resin bonded sand cores/parts, presenting various test apparatuses designed for this purpose, and outlines the foundational setup and definition of bonded-particle models (BPM) to be used as breakable structures in respective DEM simulations.

Thermal Properties of 3D-Printed Molds for Light Metal Casting

AbstractBinder Jetting technology is well established for the production of sand molds and cores for foundry use, owing to its flexibility and expansive design capabilities. A wide array of sand, aggregate, and binder combinations is commercially available. Utilizing these types of refractory materials in the casting process presents both technical and economic benefits and drawbacks. For intricate cast components, foundry technologists must assess the thermophysical properties of the mold material systems. With this knowledge, specialized high-performance material combinations may be employed in specific areas of the mold, while more economically viable systems are used for shaping the external mold support. This study primarily focuses on determining the heat capacity and thermal diffusivity and consequently the thermal conductivity using a specially developed analytical method. It investigates three different fundamental aggregates: silica, cerabeads®, and chromite. The result’s range provides an overview of relevant characteristics for the selected material systems. Given that the properties of sand affect heat flow during casting and solidification, these newly determined values can be utilized in future simulations. Consequently, these findings aid in maintaining and enhancing the quality of critically stressed cast parts.

The Technique of Inorganic Core Sand Shooting with Reduced Pressure in Venting System

The publication presents a new shooting technique with reduced pressure in venting system for manufacturing foundry cores using inorganic sand mixture with Cordis binder. Traditional technologies for producing casting cores using blowing methods, despite their undeniable advantages, including the ability to produce cores in series, also come with some disadvantages. The primary drawbacks of the process involve uneven compaction structure of the cores, with denser areas primarily located under the blow holes, and under-shooting defects, which often occur in regions away from the blow hole or in increased core cross-sectional areas. In an effort to improve core quality, a concept was developed that involves incorporating a reduced pressure in the core box venting system to support the basic overpressure process. The solutions proposed in the publication with a vacuum method of filling the cavities of multi-chamber core boxes solve a number of technical problems occurring in conventional blowing technologies. It eliminates difficulties associated with evacuating the sand from the chamber to the shooting head and into technological cavity and increases the uniform distribution and initial degree of compacting of grains in the cavity. The additive role of this “underpressure” support is to enhance corebox venting by eliminating 'air cushions' in crevices and structural elements that obstruct the flow of evacuated air. The publication presents the results of studies on core manufacturing using blowing methods conducted in three variants: classic overpressure, utilizing the core box filling phenomenon by reducing pressure, and an integrated approach combining both these methods.

Three-Dimensional Discrete Element Analysis of Bearing Characteristics of Concrete–Cored Sand–Gravel Pile Composite Foundation under Cyclic Dynamic Load

Concrete-cored sand–gravel piles are a kind of composite pile formed by wrapping a concrete-cored pile with a sand–gravel shell, which has the advantages of both a rigid pile and bulk-material pile. The bearing characteristics of the concrete-cored sand–gravel pile composite foundation were investigated by establishing a three-dimensional discrete element numerical model for a cyclic dynamic loading test. The results show that the vertical stress of the core pile body fluctuates greatly at the beginning of loading, and the fluctuation amplitude decreases with the depth, and gradually tends to be stable in the middle and late stages, and the vertical-stress distribution is relatively uniform. The radial stress in the upper part of the core pile body fluctuates greatly, the fluctuation in the lower part is small, and the radial stress in each part of the core pile body gradually tends to be stable in the late-loading period. The radial stress factor of the core pile body reaches the stable speed with the foundation depth decreasing; the fluctuation amplitude of the pile-soil stress ratio decreases with the foundation depth and gradually tends to be stable with the increase in loading. The results of this study can provide a reference for the design and construction of a core sand pile composite foundation.

Increasing the Quality of Manufacturing Sand Cores at the Casting and Mechanical Plant

Increasing the Quality of Manufacturing Sand Cores at the Casting and Mechanical Plant

Production, characterization, and application of Pseudoxanthomonas taiwanensis biosurfactant: a green chemical for microbial enhanced oil recovery (MEOR)

Biosurfactants, as microbial bioproducts, have significant potential in the field of microbial enhanced oil recovery (MEOR). Biosurfactants are microbial bioproducts with the potential to reduce the interfacial tension (IFT) between crude oil and water, thus enhancing oil recovery. This study aims to investigate the production and characterization of biosurfactants and evaluate their effectiveness in increasing oil recovery. Pseudoxanthomonas taiwanensis was cultured on SMSS medium to produce biosurfactants. Crude oil was found to be the most effective carbon source for biosurfactant production. The biosurfactants exhibited comparable activity to sodium dodecyl sulfate (SDS) at a concentration of 400 ppm in reducing IFT. It was characterized as glycolipids, showing stability in emulsions at high temperatures (up to 120 °C), pH levels ranging from 3 to 9, and NaCl concentrations up to 10% (w/v). Response surface methodology revealed the optimized conditions for the most stable biosurfactants (pH 7, temperature of 40 °C, and salinity of 2%), resulting in an EI24 value of 64.45%. Experimental evaluations included sand pack column and core flooding studies, which demonstrated additional oil recovery of 36.04% and 12.92%, respectively. These results indicate the potential application of P. taiwanensis biosurfactants as sustainable and environmentally friendly approaches to enhance oil recovery in MEOR processes.

Effects of surfactants on the physical properties of silicate binders and the mechanical properties of silicate-bonded foundry sand cores

In the foundry industry, casting sand cores require high and low peak and residual strengths, respectively, to achieve comprehensive optimal mechanical performance. The peak and residual strengths of sand cores are positively related, highlighting the criticality of balancing them. Thus, an innovative approach comprising the incorporation of anionic surfactants into the silicate binder was introduced to balance both factors. Additionally, the investigation of the effects of the anionic surfactants on the physical properties of the silicate binder, including its colloidal stability, surface tension and adhesion, revealed that four different anionic surfactants reduced the surface tension and adhesion of the silicate binders and reduced the residual strength of the silicate-bonded sand cores. Among them, 0.10 wt% lauryl ether phosphate reduced the surface tension and adhesion of the adhesive by 49.64 and 112 mN/m, respectively, and reduced the residual strength of the sand core by 0.035 MPa. However, increasing the dosage did not further reduce the residual strength of the sand core, although it continued to reduce its peak strength. Therefore, during silicate binder modification with anionic surfactants, the dosage of the anionic surfactant must be kept at ≤0.10 wt%, as this dosage exerted the most comprehensive optimal modification effect, which was attributable to the adsorption of anionic polymers onto the surface of the silicate aggregates. This adsorption weakened the network structure of the silicate aggregates and imparted the sand cores with appropriate mechanical properties during casting.

Linear contraction of sand casting Mg–9Gd–3Y–0.5Zr alloy

The effect of geometric characteristics of castings on the linear contraction of sand casting Mg–9Gd–3Y– 0.5Zr alloy (VW93) was studied. The dimensions of free and restrained structure castings were precisely extracted by a 3D scanner and then used for the calculation of the contraction coefficient. The ratio of sand core volume to enveloping volume of casting (γ), was introduced to quantify the degree of constraint caused by sand cores. According to the statistical distribution of free contraction coefficients and the evolution of restrained contraction coefficients against γ, it is indicated that the free contraction coefficient of VW93 alloy equals 1.96%, and the restrained contraction coefficient declines linearly with the increasing γ, which supplies support on predicting the contraction of VW93 alloy through the geometric characteristic of castings.

The Influence of the Matrix Grain Size and Mineral Addition on Improving the Knock-Out Properties of Molding Sands with an Inorganic Binder

This article presents the results of tests of molding and core sands with inorganic binders incorporating a mineral in the form of raw perlite ore. This material serves to reduce the final strength, thereby improving the knock-out properties. The assumption was made that the selection of the optimal fraction of the loosening additive, tailored to the grain size of the matrix of the molding sand used in foundries, could significantly affect its mechanical and technological parameters. The tests were conducted on molding sands prepared using three quartz sands with the addition of perlite ore of different grain sizes. In addition to determining the final tensile strength, the permeability and grindability of the molding sands were assessed. The results indicated that the raw perlite ore significantly reduced the final strength of the molding sands in each considered system, with the best efficiency achieved when using finer fractions. Moreover, the mineral’s addition had a minor impact on the technological properties of the molding sands, such as permeability and grindability.

Experimental impact study of ultra‑fine metal powders on technical characteristics and physical properties of foundry sodium silicate sand cores

Experimental impact study of ultra‑fine metal powders on technical characteristics and physical properties of foundry sodium silicate sand cores

A Sustainable Solution with Improved Chemical Resilience Using Repurposed Glass Fibers for Sewage Rehabilitation Pipes

This paper introduces a sustainable sewage rehabilitation solution, utilizing repurposed glass fibers for enhanced chemical resilience and environmental conservation. The approach involves dividing a unitary pipe into segments, assembled during commissioning, aiming to reduce installation and transportation costs, particularly in less accessible areas. Each pipe segment comprises a multi-layered glass fiber composite sandwich, joined by an adhesive reinforced with recycled glass fibers. The glass fiber-reinforced plastic (GFRP) pipe features a core of blended sand impregnated with resin, an outer layer for impact resistance, and an inner layer to prevent corrosion. Chemical resilience is assessed through a 10,000 h strain corrosion study exposing both unitary and two-piece circular GFRP pipes to sulfuric acid in a deflected condition. An apparent hoop tensile test evaluates mechanical integrity before and after exposure. The experimental results reveal that the two-piece pipe with a tongue and groove joint (TGJ) with recycled glass fiber adhesive exhibits superior long-term bending stress and failure strain % compared to unitary pipes. This enhancement is attributed to the TGJ’s improved load-bearing capability and chemical resistance. The failure strain % of the two-piece pipe (1.697%) is higher compared to the unitary pipe (1.2613%). The long-term bending stress of the two-piece pipe obtained is 119.94 MPa whereas the unitary pipe reaches 93.48 MPa at the 50-year mark. The cost analysis supports the adoption of the two-piece pipe over unitary pipes due to a 40% reduction in carbon emissions and transportation cost. The novelty lies in the utilization of multi-piece pipes with enhanced chemical resilience, achieved through the incorporation of milled fiberglass reinforcements in the TGJ. Strain corrosion tests take a long time to perform; hence, an accelerated test is needed to improve the current recommended testing standard.

The Use of 3D Printed Sand Molds and Cores in the Castings Production

As a part of this work, an analysis of the current state of knowledge regarding the use of additive technology - binder jetting in the production of castings was made. The binder jetting (so-called 3D printing) has become the leading method of sand mold and core production. Within this paper types of molding and core sands with organic and inorganic binders that are and can be used in technology were analyzed. The need to carry out works aimed at developing pro-ecological molding / core sands with inorganic binders and organic binders with reduced harmfulness to the environment dedicated to binder jetting technology was noticed. The influence of technology parameters on the properties of molding / core sands and the properties of cast components was analyzed. It was shown that thanks to the unlimited shapes of the systems obtained with the use of additive technologies, it is possible to influence the rate of heat dissipation through the mold, which positively effects the process of solidification and crystallization of the castings.

On the mechanism of binder migration in furan binder jetting of sand molds and cores

Binder Jetting is a layer-based additive manufacturing process in which a printhead deposits droplets onto a pre-prepared layer of particles. Upon droplet impact, the binder begins to migrate and infiltrate adjacent areas away from its originally intended location. The purpose of this study is to investigate the mechanism of furan binder migration. Observing in-situ binder spreading is challenging, especially for the furan binder used in this work. The strong discoloration of the surrounding sand makes it difficult to distinguish between the printed pattern and the surrounding loose sand. For this reason, a fluorescent dye is added to the binder. A wavelength-matched laser in the binder jetting machine provides the excitation energy, and in-situ observation of binder migration becomes feasible. The results show an unexpected behavior where the actual microscopic fluid redistribution of the binder does not match the observed macroscopic measurements of other reports. It becomes clear that the migration mechanism of furan binder in sand binder jetting is strongly influenced by gaseous mass transport. To support this theory, a phenomenon called boundary zone is studied by micrographic and computed tomographic analysis. This outer shell region surrounds samples with higher binder contents and extends over a thickness of approximately 400 µm. The binder content here is significantly higher than that of the core of the specimen and its target value, demonstrating that liquid concentration equalization is not feasible. A plausible explanation is evaporation and condensation of binder, resulting in localized binder accumulation in areas of high catalyst to binder ratios. Since binder evaporation is an overlooked issue in furan binder jetting, additional experiments are performed to demonstrate the extent of evaporation. For this, particle layers are deposited on a scale, the printhead deposits binder, and the resulting mass loss is recorded. With a better understanding of binder migration, new strategies can be developed to reduce geometric deviation, improve geometric precision, and possibly allow for higher layer thicknesses in furan sand binder jetting.

Research on Gas Pore Prediction Method Based on Sand Core Characteristic Time

Research on Gas Pore Prediction Method Based on Sand Core Characteristic Time

Analysis of Influence of Sand Matrix on Properties of Moulding Compounds Made with Furan Resin Intended for 3D Printing

Binder jetting (BJ) sand printing is a 3D printing process in which a sand mould or sand core is produced from an STL file. A single layer of a sand matrix consisting of one or more grains in height of sand is applied to a worktable, and then a liquid resin or binder is applied to bond the grains together. This process is repeated until the final result matches the CAD model. The sand matrix is the main component of ceramic cores and moulds. The present study aims to demonstrate the influence of the matrix used on the properties of the resulting moulding sand. Three types of sand matrices were selected for the study. The first was a quartz matrix for 3D printing with binder jetting; this is characterised by a sharp geometry that allows for proper layering during printing. Ordinary quartz sand was also used for the study; this type of sand is usually used for the production of sand cores in the hotbox process, among other things. The shape of this sand is irregular. The last matrix to be tested was Cerabeads sand; this was selected because its spherical geometry clearly distinguishes it from the other two matrices. The matrices were analysed for their grain sizes. Scanning electron microscope images were also taken to compare the geometries and chemical compositions of the respective matrices. In presented research utilises a sand matrix for the production of self-curing compounds with furan resin dedicated for binder jetting 3D printing. The moulding masses were produced in a laboratory circulation mixer. The laboratory moulds were produced with wooden core boxes and pre-compacted by vibration. The samples from the matrix for the 3D printing were produced using the binder jetting method. The samples were produced to determine the flexural strength, tensile strength, gas permeability, hot distortion, and apparent density. It was not possible to carry out tests for the Cerabeads sand, as the obtained moulds were too brittle to perform adequate tests. Tests with the other matrices have shown that the shape and size of the matrix affect the apparent density and gas permeability.

Modeling De-Coring Tools with Coupled Multibody Simulation and Finite Element Analysis

De-coring is an essential process in the casting process chain, determining the quality and cost of production. In this study, a coupled multibody system (MBS) and finite element modeling (FEM) technique is presented to study the mechanical loads during the de-coring process. The removal of cast-in sand cores from the inner regions of the cast part by de-coring or knocking out is a complex process with dynamic loads. Currently, the process relies upon empirical knowledge and tests. Inorganic sand cores pose additional challenges in the success of the de-coring process. Increasing complexity in geometry and stringent environmental regulations compel a predictive process in the earlier stages of design. Predicting the process’ success is challenged by the dynamic non-linearities of the system. The dynamic characteristics and the interaction between hammer and casting were studied here for the first time using an industrial-based test rig, and a novel modeling approach was formulated. The results of the developed model are in good compliance with the experiments. The methodology presented in this study can be used to include a varying number of hammers and loads. The proposed approach presents the possibility to discretize the process and qualitatively assess the process parameters for optimization.

Investigation of 3D Printing Sand Core Technology on the Mechanical Behaviors of Soft–Hard Interbedded Rock Masses

Investigation of 3D Printing Sand Core Technology on the Mechanical Behaviors of Soft–Hard Interbedded Rock Masses