Performance of digital patternless freeze-casting sand mould

Digital patternless freeze-casting technology is a new approach for obtaining frozen sand moulds using digital milling technology. The change law of tensile strength and air permeability of frozen sand moulds (100-mesh and 200-mesh silica sand, and zircon sand moulds) under different freezing temperatures and water contents was studied. Results show that with the decrease of freezing temperature and the increase of water contents, the tensile strength and air permeability of the sand moulds are gradually improved. Meanwhile, computed tomography technology was used to characterize the shape and size of the water film between the sand particles mixed with 4wt.% water. The results show that in silica sand moulds, the form of water film is lumpy, and 200-mesh silica sand moulds have more water films and higher proportion of small-sized water films than 100-mesh silica sand moulds, while in zircon sand moulds, the form of water film is membranous. At the same freezing temperature and water content, the tensile strength of zircon sand mould is the highest, and 100-mesh silica sand mould is the lowest. A comparative solidification experiment of A356 aluminum alloy was carried out in frozen sand mould and resin sand mould. The results show that the primary α-Al phase appears in the form of equiaxed and eutectic silicon phase is needle-like in freezing sand mould casting, but the primary α-Al phase grows in the form of dendrites, and the eutectic silicon phase is coarse needle-like in the resin sand mould casting. The difference of microstructure is caused by the different cooling rate. The cooling rate of A356 aluminum alloy in frozen sand mould is higher than that in resin sand mould.

A Model for Predicting Dynamic Cutting Forces in Sand Mould Milling with Orthogonal Cutting

Cutting force is one of the research hotspots in direct sand mould milling because the cutting force directly a ects the machining quality and tool wear. Unlike metals, sand mould is a heterogeneous discrete deposition material. There is still a lack of theoretical research on the cutting force. In order to realize the prediction and control of the cut?ting force in the sand mould milling process, an analytical model of cutting force is proposed based on the unequal division shear zone model of orthogonal cutting. The deformation velocity relations of the chip within the orthogonal cutting shear zone are analyzed first. According to the flow behavior of granular, the unequal division shear zone model of sand mould is presented, in which the governing equations of shear strain rate, strain and velocity are estab?lished. The constitutive relationship of quasi?solid–liquid transition is introduced to build the 2D constitutive equation and deduce the cutting stress in the mould shear zone. According to the cutting geometric relations of up milling with straight cutting edge and the transformation relationship between cutting stress and cutting force, the dynamic cutting forces are predicted for di erent milling conditions. Compared with the experimental results, the predicted results show good agreement, indicating that the predictive model of cutting force in milling sand mould is validated. Therefore, the proposed model can provide the theoretical guidance for cutting force control in high e ciency mill?ing sand mould.

The Study of Green Compression Strength of a Green Sand Mould Using Statistical Approach

The study of green compression strength of a green sand mould using statistical approach has been undertaken. Empirically generated data in National Metallurgical Development Centre, Jos Sand Testing Laboratory were used for the study. Coefficient of correlation, coefficients of determination and coefficient of multiple determinations were used to explain the relationship existing between the two independent variables of clay and moisture content and green compression strength, the dependent variable. The study showed that the coefficient of determination for Ys: X1 was 0.88 while the coefficient of correlation was 0.94, coefficient of determination for Ys: X2 was 0.90 while the coefficient of correlation was 0.95 and the coefficient of multiple determination was 0.72;these coefficients assisted tremendously in the study of green compression strength. A mathematical model was developed for the prediction of green compression strength;it was tested and proved to be a good estimation tool for estimating green compression strength values on the foundry shop floor. The study has clearly shown that statistical approach is a good tool for studying green compression strength of green sand moulds.

Development tendencies of moulding and core sands

Further development of the technology for making moulding and core sands will be strictly limited by tough requirements due to protection of the natural environment. These tendencies are becoming more and more tense, so that we will reach a point when even processes, that from technological point of view fulfill high requirements of the foundry industry, must be replaced by more ecologically-friendly solutions. Hence, technologies using synthetic resins as binding materials will be limited. This paper presents some predictable development tendencies of moulding and core sands. The increasing role of inorganic substances will be noticed, including silicate binders with significantly improved properties, such as improved knock-out property or higher reclamation strength. Other interesting solutions might also be moulding sands bonded by geo-polymers and phosphate binders or salts and also binders based on degradable biopolymers. These tendencies and the usefulness of these binders are put forward in this paper.

Influence of wet activation of used inorganic binder on cyclically refreshed water glass moulding sands hardened by microwaves

The paper presents the research results of using an innovative method to reclaim the waste moulding sands containing water glass. Two of the examined processes are connected with "dry" or "wet" activation of inorganic binder in waste moulding sand mixtures physically hardened by microwave radiation. The sand mixtures consisting of high-silica sand and water-glass with average molar module 2.5, were subjected to the following cyclical process: mixing the components, compacting, microwave heating, cooling-down, thermally loading the mould to 800 °C, cooling-down to ambient temperature, and knocking-out. After being knocked-out, the waste moulding sands were subjected to either dry or wet activation of the binder. To activate thermally treated inorganic binder, each of the examined processes employed the surface phenomenon usually associated to mechanical reclamation. The study also covered possible use of some elements of wet reclamation to rehydrate waste binder. To evaluate the effectiveness of the two proposed methods of waste binder activation, selected strength and technological parameters were measured. After each subsequent processing cycle, the permeability, tensile strength and bending strength were determined. In addition, the surface of activated sand grains was examined with a scanning electron microscope. Analysis of the results indicates that it is possible to re-activate the used binder such as sodium silicate, and to stabilize the strength parameters in both activation processes. Permeability of the refreshed moulding sands strongly depends on the surface condition of high-silica grains. The wet activation process by wetting and buffering knocked-out moulding sands in closed humid environment makes it possible to reduce the content of refreshing additive in water-glass. The moulding sands cyclically prepared in both processes do not require the addition of fresh high-silica sand. The relatively high quality achieved in the refreshed moulding sands allows them to be reused for manufacture of next moulds. Thus, the two proposed methods for cyclically processing used moulding sands containing sodium silicate, subject to microwave hardening, are suitable for economic and ecological circulation moulding mixtures.

Criteria for an advanced assessment of quality of moulding sands with organic binders and reclamation process products

Reclamation of used moulding and core sands has been defined as a treatment of waste moulding refractory materials, enabling a recovery of at least one of the components having properties similar to those of the fresh component, and reuse for production of casting moulds and cores. However, at present, there is a lack of a reclaimed material assessment index, which could be applied to each type of moulding sand and reclaim. Modern investigation methods and equipment for the estimation of the quality of the moulding sands matrices with organic binders, in their circulation process, are presented in this paper. These methods, utilizing the special equipment combined with the author's investigation methods developed in the Faculty of Foundry Engineering, AGH - University of Science and Technology, allow the better estimation of the matrix quality both in an aspect of its application as a fresh sand substitute in the preparation of moulding sands, and also with regard to the environmental protection. The most important criteria for the technological assessment of the reclaimed materials and the quality of sands with organic binders are presented in this paper.

Investigations of physicochemical properties of dusts generated in mechanical reclamation process of spent moulding sands with alkaline resins

Mechanical reclamation processes of spent moulding sands generate large amounts of postreclamation dusts mainly containing rubbed spent binding agents and quartz dusts. The amount of postreclamation dusts, depending in the reclamation system effi ciency and the reclaim dedusting system, can reach 5%-10% in relation to the total reclaimed spent moulding sand. The proper utilization of such material is a big problem facing foundries these days. This study presents the results of investigations of physicochemical properties of post- reclamation dusts. All tested dusts originated from various Polish cast steel plants applying the mechanical reclamation process of moulding sands with alkaline resins, obtained from different producers. Different dusts, delivered from foundries, were tested to determine their chemical composition, granular characterization, physicochemical and energetic properties. Presented results confi rmed assumptions that it is possible to utilize dusts generated during mechanical reclamation of used sands with organic resins as a source of energy.

Biodegradable materials as binders for IVth generation moulding sands

This paper focuses on the possibility of using the biodegradable materials as binders(or parts of binders' compositions) for foundry moulding and core sands. Results showed that there is a great possibility of using available biodegradable materials as foundry moulding sand binders. Using biodegradable materials as partial content of new binders, or additives to moulding sands may not only decrease the toxicity and increase reclamation ability of tested moulding sands, but also accelerate the biodegradation rate of used binders, and the new biodegradable additive(PCL) did not decrease the strength and thermal properties. In addition, using polycaprolactone(PCL) as a biodegradable material may improve the flexibility of moulding sands with polymeric binder and reduce toxicity.

Effect of Varying Corn Cob and Rice Husk Ashes on Properties of Moulding Sand

The use of rice husk and corn cob ashes as aggregates for foundry moulding sand has been studied. 5-12.5 weight percent of rice husk and corn cob ashes were added to the sand mixture and the sand properties determined. A mixture of equal proportion of rice husk and corn cob ashes was also used. In each case, four weight percent water and clay were added to the sand mixture. Some of the properties of the sand tested are: permeability, green compression strength, dry compression strength, green shear strength, dry shear strength, moisture content and permeability. The results showed that the green compression strength, green shear strength, moisture content and permeability decrease with increase in the additives (rice husk ash, corn cob ash, and (50% rice husk and 50% corn cob ashes). While dry compression strength and dry shear strength increase with increase in weight percent of the additives.

A new numerical simulation model for high pressure squeezing moulding

High pressure squeeze is the most popular moulding process applied in modern moulding machines.Because of the unique characters of moulding sand and nonlinearity of squeezing process,the mechanical model is of key importance for computer simulation.Drucker-Prager/Cap is a typical soil mechanical theory model and it was used to simulate the squeezing process in this study,while ABAQUS software is used to simulate dynamic stress/strain evolution during the process.The simulation agrees well with the experimental results.We conclude that Drucker-Prager/Cap is an appropriate model for the squeezing compaction of moulding sand,and that the associated nonlinearity can be solved well with ABAQUS software.

Iron casting skin management in no-bake mould – Effects of magnesium residual level and mould coating

The relative performance of coatings for furan resin sand moulds [P-toluol sulphonic acid(PTSA) as hardener] [FRS-PTSA moulds], was compared by analyzing the surface layer for degenerated graphite in Mg treated iron with 0.020 wt.% to 0.054 wt.% Mgres. It was found that the iron nodularising potential(Mg, Ce, La content) and whether the mould coatings contained S, or were capable of desulphurizing were important factors. These moulds have S in the PTSA binder, which aggravates graphite degeneration in the surface layer, depending strongly on the Mgres with lower Mgres increasing the layer thickness. The application of a mould coating strongly influenced graphite deterioration in the surface layer of castings. It either promoted graphite degeneration to less compact morphologies when using S-bearing coatings, or conversely, limited the surface layer thickness using desulphurization type coatings. Independently of the S-source at the metal – mould interface, the presence of sulphur had an adverse effect on graphite quality at the surface of Mg-treated irons, but its negative effect could also reach the graphite phase within the casting section. If the coatings employed desulphurization materials, such as Mg O, or a mixture(Ca O + Mg O + Talc) or Mgbearing Fe Si, they protected the graphite shape, improving graphite nodularity, at the metal – mould interface, and so decreased the average layer thickness in FRS-PTSA moulds. Fe Si Mg was highly efficient in minimizing the casting skin by improving graphite nodularity. It is presumed that the Mg O or(Mg O + Ca O + Talc) based coatings acted to remove any S released by the mould media. The Mg-Fe Si coatings also reacted with S from the mould but additionally supplemented the Mg nodularising potential prior to solidification. This dual activity is achievable with coatings containing active magnesium derived from fine Mg-Fe Si materials.

硅砂、陶粒砂和宝珠砂铸造工艺性能研究

研究了鄂尔多斯硅砂、通辽硅砂、海南海砂、陶粒砂和宝珠砂的形貌,用其做原砂的碱酚醛树脂砂的抗拉强度,原砂抗机械破碎和粉化能力等。结果表明:鄂尔多斯硅砂形貌最差,呈尖角、片状;通辽砂、海砂较好,呈圆形、多角形;陶粒砂和宝珠砂最好,呈圆形。型砂24 h时抗拉强度,鄂尔多斯硅砂最低,只有0.277 MPa;通辽硅砂和海砂较高,接近0.6 MPa;宝珠砂最高,接近0.9 MPa;陶粒砂为0.667 MPa,高于硅砂,低于宝珠砂。经机械搅拌破碎试验得出:鄂尔多斯硅砂强度较低,抗破碎能力最差,易破碎粉化,粉尘含量由0.03%提高到0.812%;通辽硅砂和海砂强度都较好,粉化较轻,粉尘含量由0.016%提高到0.32%;陶粒砂强度也较好,粉化较少,粉尘含量由0提高到0.195%;宝珠砂破碎和粉化率极低,粉尘含量基本无变化。

压下制动盘的国产化试制

分析制动盘的结构特点,采用铁模覆砂铸造工艺,通过原料成分控制,炉前工艺控制,铁型砂箱改进等措施,均衡整个圆盘温度场分布,消除缩孔等缺陷,实现铸件内部组织致密,确保制动器试制成功。

Performance analysis of cow dung as an eco-friendly additive material for sustainable moulding and casting

In the present work,an attempt is made to partially replace high cost silica sand with sustainable eco-friendly cow-dung.The practical utility of cow dung as an additive material that facilitates binding in sand moulds has been tested.The Taguchi method is used to plan and conduct nine experiments with three replicates each.Pareto analysis of variance study is performed to understand the practical significance of moulding sand variables,that is,percentage of cow dung,clay,water,and degree of ramming on sand mould properties.The conflicting multiple objective functions(maximize mould hardness,and minimize collapsibility and gas evolution)are optimized by utilizing the Data Envelopment Analysis Ranking(DEAR)method.The optimal parameters i.e.6%of clay,4%of water,5%of cow-dung and 4 numbers of ramming strokes are obtained by applying a hybrid Taguchi-DEAR method.These parameters show the best moulding properties are:mould hardness 55,gas evolution 5.9 ml·g-1,and collapsibility 470 g·cm-2.Thereafter,a Lovejoy coupling made of aluminium is cast in the sand mould prepared with cow dung and without cow dung,with the optimum set of parameters.The mechanical properties,surface finish,and microstructure of the casting cast with cow-dung are better than that without cowdung.

Impact of Moisture Variation on Some Foundry Properties of Fori Silica Sand

Moulding Sand for metal casting is usually sourced from either natural deposit or synthetic mix of refractory sand grain binder and moisture. Each of the mix constituent is important in determining the characteristics of sand. The binding agent is responsible for bendability thereby determining the size of voids within the sand grain, while moisture level determines the plasticity of the foundry sand. Tests using American Foundry Society (AFS) Standard were followed in carrying out the experiment on Fori sand deposit to determine its suitability for foundry use. The sand was collected from the river bank of Fori, in Fori Community, Maiduguri, Borno State. The experimental test equipment includes: laboratory sand mixer, sand rammer, universal strength testing machine, permeability-meter, oven, mouldability machine, and as well as quick moisture teller. The chemical composition of the materials was carried out using atomic absorption spectrophotometer (AAS) model PG990AFG. The silica content in the material sample is about 78.65%, and with the traces of other elements, such as CaO (1.07%), Fe2O3 (0.76%), Al2O3 (15.81%), MgO (1.01%), TiO2 (2.21%), K2O (3.87%), and Na2O (1.16%), respectively. These percentages are within acceptable limits. The results of the physical properties revealed that the sand sample has clay content of 15.32% which is above the standard range of 10% - 12% recommended for natural moulding sands required for producing good quality castings. Other foundry properties of Forinatural moulding sand conducted include “moisture content” in the following ranges of percentages, 7.6%, 6.5%, 5.8%, 4.2% and 2.9% with the corresponding value of green compressive strength of (43.95, 53.47, 69.56, 68.21 and 61.16 KN/m2), dry compressive strength (93.50, 96.52, 105.50, 146.50 and 152.49 KN/m2), and permeability No. of 340, 390, 410, 430 and 440 respectively. It is clear from the test that, the lower the moisture content, the higher the dry compressive strength of the materials. The refractoriness value of the materials is 1400 ℃. The results of the physical and other foundry properties carried out show that Forisilica sand is suitable for casting non-ferrous alloys like bronze, brass and aluminium, and cast iron.

Effects of Additives on Some Selected Properties of Base Sand

In this study, effects of sawdust, coal dust and iron filling additives at varied proportions on some selected properties of moulding sand were investigated. Consequently, cylindrical specimens with different percentages of additives were prepared based on standard procedures. The prepared specimens were subjected to basic moulding sand testing including moisture content, bulk density, porosity, permeability, green compression strength and green shear strength using standard methods and equipment. From the obtained test results, all the experimental additives were found to improve the selected moulding properties of the base (silica) sand. Moulding sand specimen with sawdust additive revealed a relatively better compaction as compared to moulding sand specimens with coal dust and iron filling additives respectively. The moisture absorbing strength of the moulds was also found to increase with increasing percentage of sawdust. Addition of coal dust to the moulding sand was found to improve sand porosity and permeability which results in less casting defects, and due to improved moisture absorbing strength of sawdust, moulding sand specimens that contained sawdust were equally found to exhibit good compaction with maximum green compressive strength of 108.99 kPa. Also, the combination of 25% sawdust, coal dust and iron filling in the moulding sand was found to produce mould with optimum green shear strength value of 54.49 kPa.

基于CAE的缸盖砂型铸造浇注温度和铸型温度对缩孔的影响研究

针对汽车发动机缸盖铸件在砂型铸造过程中存在的缩孔缺陷,利用CAE模拟软件研究关键工艺参数——浇注温度和铸型温度对缩孔缺陷的影响。缩孔缺陷主要出现在缸盖的厚壁处,在浇注温度为1370℃、铸型温度为20℃以及浇注温度为1360℃、铸型温度为30℃时,缩孔数量最少,为22个。通过相关性分析,发现相较于铸型温度,浇注温度对缩孔数量的影响更明显。

GB/T 42156-2023《铸造砂型3D打印设备通用技术规范》国家标准解读

国家标准《铸造砂型3D打印设备通用技术规范》为指导和规范铸造砂型3D打印设备的设计、制造和验收提供了依据,对规范市场竞争、引导市场良性发展起到积极的作用。通过标准的制定和实施,为铸造砂型3D打印设备及技术的推广应用提供了有力的技术支撑,为推进产业结构调整与优化升级创造条件,对加快我国铸造砂型3D打印技术快速发展具有积极的促进作用。本文介绍了该标准起草的主要过程,对标准中的主要内容和关键点进行了解读,帮助标准使用者正确理解和认识该国家标准,以便于该标准的推广应用。

机器人手臂铸件铁型覆砂铸造工艺生产实践

目前,工业机器人在各个领域应用广泛,对机器人手臂铸件的质量要求也随之提高。本文根据机器人手臂的结构特征及技术要求,结合铁型覆砂铸造工艺特点,设计了机器人手臂铸件的铁型覆砂铸造工艺方案,并通过凝固模拟软件对工艺方案进行了优化。结果表明,机器人手臂铸件的铁型覆砂铸造工艺优化方案可行,实现了铸件的稳定高效清洁生产,铸件产品质量稳定,合格率达95%以上,表面粗糙度Ra达到12.5~25.0μm、尺寸精度为CT7级,降低了生产成本,可推广应用。

重型商用车平衡轴支架拓扑优化设计与试制研究

平衡轴支架是重型商用车平衡悬架的关键零件,也是平衡悬架总成中质量占比最大的零件。针对某重型商用车现有的平衡轴支架产品质量大、制造工艺性差等问题,亟需开发出轻量化、制造工艺性良好的平衡轴支架产品。基于ANSYS Workbench平台建立该重型商用车平衡轴支架的有限元模型,对3种典型工况下的平衡轴支架进行强度分析,在此基础上采用基于变密度法的拓扑优化技术对平衡轴支架进行轻量化设计。根据结构拓扑优化结果,对平衡轴支架进行模型重构,并对优化后的结构进行强度校核。结果表明,结构优化后的平衡轴支架与优化前相比质量减轻46.5%,强度满足使用要求。最后采用铁型覆砂铸造工艺对优化后的平衡轴支架进行样件试制,制造工艺性良好,铸件质量满足要求。