Strength Of Mold Research Articles

Numerical simulation study on the mold strength of magnetic mold casting based on a coupled electromagnetic-structural method

Numerical simulation study on the mold strength of magnetic mold casting based on a coupled electromagnetic-structural method

Effect of Additives on Heat Hardened Inorganic Solid Foundry Binder

AbstractRenewed interest in inorganic binders for sand molding has also intensified research on different forms of it. In this study, solid inorganic sodium silicate binder was tested with different additives to see how these affected the silica mold quality. The five additives used were: glucose, sucrose, boric acid, aluminum oxide and iron(III)oxide powders. The mold quality was assessed through tests like bending strength, tensile strength, hot distortion, wear resistance, gas evolution and collapsibility tests. In addition, SEM imaging was done on some select mold fracture samples. In the end, a casting trial was carried out followed by a surface roughness and defects analysis. A reduction in mold strength was noticed with glucose and boric acid, while collapsibility was improved by glucose, sucrose and boric acid additives. Casting trials have shown the best surface finish to be obtained with sucrose additive. All the casts in general showed some penetration; however, repeat casts have proven that altering some casting parameters could result in casts with excellent surface finish using solid silicates.

Certain investigation on feasibility of developing riser less ductile iron castings

The solidification mechanism of ductile iron is a bit complex due to the precipitation of graphite and silicon. These elements change the solidification pattern of cast iron. Density of these elements is less than iron leads to occupying more volume consequently increase the overall metal volume. There are two aspects on this increase in metal volume. One is, reducing this volume increase to reduce the creation of porosities at the earlier stage of solidification and second is, using this volume increase to remove porosity at the later stage of solidification. Proper understanding of this graphite expansion in cast iron solidification will bring insights on reducing or removing of the risers. The current study focus on correlating the net contraction and austenitic liquidus point with shrinkage. The average contraction found through this study is 1.36 % which is more than the net expansion of 0.25 % (without riser) reported in literature. The study found that properly balancing graphite precipitation, pouring temperature and mold strength can enable riserless casting of ductile iron by compensating for liquid contraction through graphite expansion.

Proposition of new yield criterion for green sand mold and its experimental validation by FEM stress analysis of triaxial compression test

Prediction of the deformation during shape casting by FEM (finite element method) thermal stress analysis has been desired. For such prediction, validated constitutive models are essential for both the casting alloy and the mold. In this paper, two fatal defects in the modified Cam-Clay (MCC) model, which has conventionally been employed for a green sand mold, are clarified. The aim of this paper is to concurrently resolve these defects by a new yield criterion. The defects were those that cause an unreal distinct yielding and dilatancy peak on the stress-strain curve, which was clarified by comparing the true stress-strain curves obtained in the experiment and the FEM stress analysis of a triaxial compression test. A device capable of measuring the true stress during vertical compression was newly developed for the triaxial experiment. These defects inevitably led the MCC model to overestimate the mold strength by approximately 200% of the experimental value. This paper provides a new yield criterion, which employs an additional yield surface with the Drucker-Prager inherent surface, to rectify these defects of the MCC model. As a result of the stress analysis of the triaxial test with the new criterion, the smooth stress-strain curve with neither a peak nor a distinct yielding was reproduced. The calculated compressive stress traced the experimental value with less than a 15% error. Therefore, the new criterion should remarkably improve the accuracy of calculating the mold strength in the FEM thermal stress analyses during casting when compared to the MCC model.

Porous Diatomaceous Earth/Nano-Zinc Oxide Composites: Preparation and Antimicrobial Applications

This paper presents the preparation and characterization of a porous and antimicrobial composite material consisting of diatomaceous earth, an inorganic pore-forming agent, and nano-zinc oxide (ZnO). A modified direct precipitation device produced high-surface area ZnO powder. The effect of reaction temperature, volume flow rate, and titration rate on ZnO particle size was studied. Using sodium chloride, potassium nitrate, and sodium percarbonate as porosity to create porous structures through dissolution was also investigated. This study found that adding cement sand to diatomaceous earth improved mold strength while lowering the volume flow rate, and increasing the reaction temperature increased the specific surface area of ZnO. At 60 °C, the crystalline structure changed from an irregular spherical form to a regular nanorod structure. The specific surface area of the prepared ZnO nanorods reached over 15 m2/g, which is about five times higher. In an antibacterial experiment, adding 5% ZnO nanorods of 50 nm diameter to the porous diatomaceous earth composite material resulted in a nearly 100% antibacterial rate against E. coli in an aqueous environment. The results suggest that the porous diatomaceous earth/nano-ZnO composite has potential applications as an antimicrobial material, and the modified direct precipitation method could have broader implications in materials science.

Three-Dimensional-Printed Molds from Water-Soluble Sulfate Ceramics for Biocomposite Formation through Low-Pressure Injection Molding.

Powder mixtures of MgSO4 with 5-20 mol.% Na2SO4 or K2SO4 were used as precursors for making water-soluble ceramic molds to create thermoplastic polymer/calcium phosphate composites by low pressure injection molding. To increase the strength of the ceramic molds, 5 wt.% of tetragonal ZrO2 (Y2O3-stabilized) was added to the precursor powders. A uniform distribution of ZrO2 particles was obtained. The average grain size for Na-containing ceramics ranged from 3.5 ± 0.8 µm for MgSO4/Na2SO4 = 91/9% to 4.8 ± 1.1 µm for MgSO4/Na2SO4 = 83/17%. For K-containing ceramics, the values were 3.5 ± 0.8 µm for all of the samples. The addition of ZrO2 made a significant contribution to the strength of ceramics: for the MgSO4/Na2SO4 = 83/17% sample, the compressive strength increased by 49% (up to 6.7 ± 1.3 MPa), and for the stronger MgSO4/K2SO4 = 83/17% by 39% (up to 8.4 ± 0.6 MPa). The average dissolution time of the ceramic molds in water did not exceed 25 min.

Precise Shrink Fitting Design of the High Strength Gear Mold for the Precision Forging of Noncircular Spur Bevel Gears

Shrink fitting of forging mold (SFFM) is an effective method for improving mold strength, extending the mold's service life and reducing the manufacturing cost of forging mold. However, due to the asymmetric geometry and complex stress distribution, the precise design of SFFM for the precision forging of noncircular bevel gears is very difficult. In this paper, a new precise design method of SFFM for the precision forging of noncircular bevel gears is proposed, which mainly includes the following five parts. First, a new design method for the mold parting surface-the curved surface parting method-is proposed to design the forging mold of noncircular spur bevel gears. Then, new dimension design methods for the gear mold and shrink rings based on the uniform shrinkage force are proposed. Third, a new design method for the inhomogeneous interference value between shrink rings and the gear mold is developed to provide a precise, uniform shrinkage force. After that, a strength correction method for the shrink-fitted gear mold is proposed to ensure the gear mold and shrink rings have sufficient strength both in the assembly process of the shrink-fitted gear mold and precision in the forging process of noncircular spur bevel gears. Ultimately, finite element simulations and verification experiments are performed to verify the proposed precise design method of SFFM for the precision forging of noncircular bevel gears. The precise design method of SFFM proposed in this paper is not only applicable to the precise design of the high-strength gear mold for noncircular bevel gears, but can also provide a valid reference for the precise design of the high-strength mold for other complicated asymmetric parts.

The Hollow Die Design of Suspension Protective Type

Because semi-hollow aluminum profiles are quite common in practice and have a large market demand, these profiles are characterized by a long cantilever, large tongue ratio, high complexity of mold design, and mold problems that have been bothering enterprises. These profiles are characterized by the long cantilever, large tongue ratio, high complexity of mold design, and mold problems that always have troubled enterprises. In order to solve this kind of mold strength problem, the engineering and technical personnel at home and abroad have carried out extensive research and have also obtained some successful experience. For example, mature die structures include split extrusion die and inlaid extrusion die, but these structures have certain applicable objects and conditions in practical application and have certain limitations in structure. Therefore, it is necessary to propose new and effective high-strength dies. A new type of die was present. The new die structure was named covering and protection die. With a actual product, the determination of structure parameters that it included the arrangement of portholes and the structure design of the chamber and the selection of bearings were introduced in detail. The features of the new structure were simple and easy to be processed. The practice shows that the new die can extended the life, increase of efficiency and reduce cost. The high precision dimensions and good surface quality were obtained. The new die is worth promoting. The purpose is to provide reliable data and reference for further research and development of the structure of semi hollow aluminum profiles.

Development of Ternary Inorganic Binder System for Manufacturing High-Functional Ceramic Molds and Core

In existing ceramic mold manufacturing processes, inorganic binder systems (Si-Na, two-component system) are applied to ensure the effective firing strength of the ceramic mold and core. These inorganic binder systems makes it possible to manufacture a ceramic mold and core with high dimensional stability and effective strength. However, as in general sand casting processes, when molten metal is injected at room temperature, there is a limit to the production of thin or complex castings due to reduced fluidity caused by the rapid cooling of the molten metal. In addition, because sodium silicate generated through the vitrification reaction of the inorganic binder is converted into a liquid phase at a temperature of 1,000 °C. or higher, it is somewhat difficult to manufacture parts through high-temperature casting. Therefore, in this study, a high-strength ceramic mold and core test piece with effective strength at high temperature was produced by applying a Si-Na-Ti three-component inorganic binder. The starting particles were coated with binary and ternary inorganic binders and mixed with an organic binder to prepare a molded body, and then heat-treated at 1,000/1,350/1,500 °C to prepare a fired body. In the sample where the two-component inorganic binder was applied, the glass was liquefied at a temperature of 1,000 °C or higher, and the strength decreased. However, the firing strength of the ceramic mold sample containing the three-component inorganic binder was improved, and it was confirmed that it was possible to manufacture a ceramic mold and core via high temperature casting.

Experimental Study of Inorganic Foundry Sand Binders for Mold and Cast Quality

The interest in inorganic foundry binders has been rising steadily in recent times due to their favorable environmental characteristics. This paper compares the mold quality and cast quality attained with different inorganic binders. Three different types of sand and five different inorganic binders were used for the mold quality study. Of the inorganic binders, there was liquid sodium silicate used in different hardening methods, a geopolymer binder, and also solid sodium silicate. The mold quality was assessed through bending strength, residual bending strength, tensile strength, and loss on ignition measurement. A total of 12 castings were made using molds of different binders and sand materials. The cast quality was then assessed by tracking changes in dimension and the surface quality of final castings. Inorganic binders performed well in terms of mold strength and very well in terms of loss on ignition but there is room for improvement in the surface quality of the castings attained.

A sustainable formwork system based on ice pattern and sand mould for fabricating customised concrete components

PurposeOptimised concrete components are often of complex geometries, which are difficult and costly to cast using traditional formworks. This paper aims to propose an innovative formwork system for optimised concrete casting, which is eco-friendly, recyclable and economical.Design/methodology/approachIn the proposed formwork system, ice is used as mould pattern to create desired geometry for concrete member, then sand mould is fabricated based on the ice pattern. A mix design and a mixing procedure for the proposed sand mould are developed, and compression tests are also performed to ensure sufficient strength of the sand mould. Furthermore, surface preparation of the sand mould is investigated for easy demoulding and for achieving good concrete surface quality. Additionally, recyclability of the proposed sand mould is tested.FindingsThe proposed mix design and mixing procedure can provide sufficient strength for sand mould in concrete casting. The finished components exhibit smooth surfaces and match designed geometries, and the proposed sand mould can be fully recycled with satisfactory strength.Originality/valueTo the best of the authors’ knowledge, this is the first study that combines ice pattern and sand mould to create recyclable formwork system for concrete casting. The new techniques developed in this research has great potential to be applied in the fabrication of large-scale concrete structures with complex geometries.

Effect of Silica Nanoparticle Dispersion on Flexural Strength of Sand Mold with Sodium Silicate Binder

Sodium silicate solutions are used as an eco-friendly binder in the casting process. However, the strength of sand molds using the sodium silicate solutions is reduced because of their low humidity resistance. In this study, silica nanoparticles were added to a sodium silicate solution with a constant SiO2/Na2O ratio to improve the humidity resistance of the inorganic binder. The effects of the dissolution times and particle size of the silica on the flexural strength of the molds was also investigated. The physiochemical properties of the inorganic binders were characterized by viscometer, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Sand molds for the flexural strength test were prepared by mixing artificial sand and inorganic binders. The addition of silica nanoparticles reduced the viscosity and water evaporation rate of the inorganic binders and improved the humidity resistance of the molds due to an increase in the SiO2/Na2O ratio. The flexural strength of the molds increased as the size of the silica nanoparticles increased, due to formation of discrete silica aggregates with high surface area. However, as the dissolution times of the silica nanoparticles increased, the strength of the molds decreased due to an enhanced Q2/Q3 ratio. Therefore, we suggest that the addition of silica nanoparticles will improve the humidity resistance of molds, and that varying the particle size and dissolution time of the silica nanoparticles affects the strength of the molds.

RESEARCH OF THE UNIFORMITY OF THE COMPOSITION OF A CERAMIC PRODUCT DURING IMPREGNATION WITH A BINDER

In the production of aircraft parts by precision casting in ceramic molds, the key parameters are the uniformity of the composition and strength of ceramic molds associated with the technology of their manufacture. The technologically optimal strength of ceramics can be achieved using the technology of re-impregnation of a ceramic product with a binder, but in this case problems arise with the isotropy of the mechanical properties of the products. The paper presents the results of research and development of methods for regulating the uniformity of impregnation of ceramic samples with a secondary binder.

A Novel Approach to Quantifying the Effect of the Density of Sand Cores on Their Gas Permeability

The density of moulding mixtures used in the foundry industry plays a significant role since it influences the strength, porosity, and permeability of moulds and cores. The latter is routinely tested in foundries using different solutions to control the properties of the moulding materials that are used to make moulds and cores. In this paper, the gas permeability of sand samples was measured using a custom-made setup to obtain the gas permeability in standard units instead of the usual permeability numbers (PN) with calibrated units. The aim of the work was to explore the effect of density variations in moulding materials on their gas permeabilities. Permeability in this work is quantified in SI units, square metres [m2]. The setup works based on Darcy’s law and the numbers obtained from the measurements can be used to deduce the gas permeability, k, of a sample. Two furan resin bonded mixtures with the same grain size distribution were hand-rammed with varying compaction forces to obtain a variation in density. Cylindrical samples (50 × 50 mm) were prepared using a silica sand aggregate sourced from a Swedish lake. The results of the measurement provided the difference in gas permeability between the samples that have varying densities. The results of permeability were then extrapolated by modifying the viscosity value of the air passed through the sample. In order to find the effect of apparent density variation on the pore characteristics of the samples, mercury intrusion porosimetry (MIP) was also performed. The results were in line with the gas permeability measurements.

Understanding the mechanics of complex topology of the 3D printed Anthill architecture

Abstract The present work aimed to investigate the deformation behavior of complex ant mound architectures under compression. We have used the cement casting method to extract four different ant nest morphologies. These casted cement structures were digitalized using a 3D micro-computer tomography scan. The digitized structures were simulated under different loading conditions using finite-element methods (FEMs). In order to supplement the numerical understanding, the digital architectures were 3D printed and experimentally tested under uniaxial loading conditions. Ants produce a variety of complex architectures for adapting to the surrounding environment and ants’ needs. Ant mound consists of at least one pillar with a broad base tapered toward its tip. Anthill architectures have unique topological features. Mechanical strength of ant mould can be 600 times enhanced by tuning topology. Thickness and angle of pillars have huge effect on load-bearing property. The branched structures can endure larger stress and deform in the process under a volumetric pressure application, making them sacrificial units for extreme disasters like floods and earthquakes. The 3D printing experiments and FEMs simulations are needed to tackle the complex ant mound architectures and appear in good agreement, suggesting a robust design and thus the possibility of constructing anthill-inspired civil buildings with a tree-trunk-like geometry.

ENVIRONMENTALLY FRIENDLY MATERIALS AND TECHNOLOGIES FOR THE PRODUCTION OF CASTINGS FROM ALUMINUM ALLOYS

The article is devoted to the topical problem of development and creation of environmentally friendly materials and technologies for foundry production. In recent years, priorities have changed in the development of materials and technological processes towards their compatibility with the environment. The environmental aspects of production come to the fore, which are determined by harmful emissions into the atmosphere, which is strictly regulated by the Kyoto Protocol. In the foundry industry to obtain castings in disposable forms, various technologies have been developed and used, which can be separated based on the type of mold used and the method of its manufacture. The main content of the study is the analysis of traditional foundry technologies and the most promising technology of casting in low-temperature forms (NTF). The peculiarity of casting in NTF is a significant increase in the strength of molds, compared with casting in sand-clay molds, as well as the possibility of using water as the main binder. This method of mold making improves the structure, increases the accuracy and geometry of castings, saves molding materials, and, most importantly, improves the environment by eliminating harmful emissions into the atmosphere of foundries. However, the method of casting in NTF has a number of disadvantages associated with the formation on the surface of castings of shells, pores, as well as increased burns. To eliminate these shortcomings, it is proposed to apply non-stick coatings on the surface of NTF and rods. Considerable attention is paid to the development and research of non-stick coatings, which allow the use of environmentally friendly casting technology in NTF for the production of castings from various alloys of high quality. Coating compositions and methods for determining the optimal composition of non-stick coating, which could be recommended for the production of aluminum castings in low-temperature molds, are identified and described. The obtained results indicate a high potential for the use of this technology as a means of improving the environmental safety of foundry production.

Research on preparation technology of modified animal glue binder for casting

Animal glue is a water-soluble natural polymer binder, which is nontoxic and harmless. However, it is easy to gel at normal temperature and the strength of molding sand is poor. In order to solve this problem, it is necessary to modify it. In this paper, citric acid (CA) is used as hydrolysis agent; then the animal glue was modified with xylitol and acrylic acid. And it is hardened by blowing in CO2 gas. The modification mechanism was analyzed theoretically by FT IR. The results show that acrylic acid and xylitol can be grafted and esterified with animal glue respectively. Through orthogonal optimization, the optimum mass ratio of the modifier was obtained as follows: acrylic acid 10g, ammonium persulfate 7g, xylose 11g, the additional temperature of modifier is 85 °C, and that of reaction time is 90min. The initial compressive strength of molding sand is 0.51 MP·a, and the compressive strength after 24 h is 4.60 MPa. The viscosity of binder is more than 1100 mPa-s. The compound modification of acrylic acid and xylitol can reduce the viscosity of animal glue, improve its fluidity and enhance the strength of sand mold.

Effects of Strength Additives on the Properties of High Bulk Pulp Mold

The bulkier structure would be one of the most important properties of the pulp mold as promising packaging materials. The low-polar solvent mixing at the forming process of wet pulp mold manufacturing resulted in the bulkier pulp mold. But the strength properties of the pulp mold would decreased. In this study, the effects of various types of paper strength additives on the strength of the pulp mold were evaluated depending on the forming condition in order to improving the strength properties of the bulker pulp mold. The dry strength and the wet strength of pulp mold were increased by the addition of the strength additives, but the effects of the additives were relatively lower in case of the low-polar solvent mixing condition. The application of the strength additives resulted in the higher increase in the strength properties of the pulp mold made of ONP than those of the pulp mold made of unbeaten BKP. The dry elongation of the pulp mold made at the low-polar solvent mixing condition showed the higher value of the pulp mold made at the water 100% condition. Although the strength properties of the pulp mold made at the low-polar solvent mixing condition were decreased, the application of the strength additives on the pulp mold could compensate for the reduction in the strength properties of the bulkier pulp mold.

Research of The Influence Mechanism of Multi Gradient Printing on Sand Mold Performance

In this paper, multi gradient sand mold sample printing was carried out based on the gray printing technology of sand mold 3D printing, and the influence of gradient distribution of resin addition in sand mold on the property of sand mold was studied. The results showed that the increase of resin addition gradient in sand mold would result in the decrease of tensile strength of sand mold with the constant total resin addition. The bending strength and air permeability of sand mold were mainly affected by the surface resin addition and gradient distribution. With increase of surface resin addition, The bending strength of sand mold decreased, and of which the air permeability increased at the same time. And the increase of gradient spacing between adjacent resin addition gradients in sand mold would lead to the increase of sand mold air permeability and the decrease of tensile strength and bending strength. The result also showed that The surface hardness of the sand mold increased with the increase of the resin content of the surface layer, and had nothing to do with the gradient distribution of the resin content.

Influence of Mold Material on the Mold Stability for Foundry Use

In CO2 molding process, sodium silicate is used as a binder to form a chemical bond to have high strength, good dimensional accuracy, etc. as compared to green sand mold. The mold materials are for present investigation wis. silica sand (ss), red mud (rdm), blast furnace slag (bfs), ferrochrome slag (fcs) and olivine sand (olv). This paper investigates the mold properties such as shear strength, compressive strength, hardness, and permeability as per to the American Foundrymen Society (AFS) standard. The mold properties of these mold materials were investigated for the stability as a mold, as compared with silica sand mold for foundry use. And also investigated the effect of mold material on the morphology of phases of the microstructure of Al-Si alloy cast in a different mold. The result shows that the mold properties of blast furnace slag were better as compared to silica sand mold; the mold properties such as shear strength, compressive strength, hardness and permeability of blast furnace slag mold and silica sand mold are 7.2 psi, 17.5 psi, 88, 630; 6.9 psi, 15.4 psi, 92, 480 respectively. The A319 alloy cast in slag mold having less porosity, lower value of secondary dendritic arm spacing (SDAS), and high tensile strength as compared to silica sand mold.