Influencing of foundry bentonite mixtures by binder activation

Although new moulding processes for manufacture of high quality castings have been developed and introduced into foundry practice in recent years, the green-sand moulding in bentonite mixture still remains the most widely used technology. Higher utility properties of bentonite binders are achieved through their activation. This contribution is aimed at finding a suitable activating agent. A number of sodium salts and MgO based agents has been chosen. In the framework of the experiment the swelling volume of chosen agents was tested and technological parameters of a bentonite mixture with a binder activated with the studied agents were determined.Web of Science55110

Effect of cast steel production metallurgy on the emergence of casting defects

The paper documents metallurgical possibilities of high alloy cast steel production in open induction medium frequency furnaces and an electric arc furnace in a gravity die casting foundry. The observation was focused on the emergence of gas defects in steel castings. The content of gases achieved during the metallurgical processes was evaluated for every unit of the production equipment and the casting ladle before casting into disposable sand moulds. The sand mould area was considered to be constant. The aim was to evaluate the current metallurgical possibilities of affecting the content of gases in high alloy cast steel in the current technical conditions of the foundry.Web of Science55470470

Evaluation of additive manufacturing of sand cores in terms of the resulting surface roughness

Obtaining a good surface finish on casting is challenging and depends on the dimension of the sand particles and the processing method of the mold. Evolving modern trends in mould and core production as a binder jetting technology is an option and it is more than desirable to evaluate and remove any possible negative effects. The aim of this study is to compare the influence of furan no-bake technology and 3D printing method on the surface quality of cores and cavities formed in aluminium alloy castings. In addition to the sieve analysis and mechanical properties of the moulding mixtures, the roughness (Ra, Rz) of the cores and resulting casting surfaces of indi-vidual samples were compared in this study.Web of Science810art. no. e1075

Innovative inorganic binder systems for the production of cores for non-ferrous metal alloys reflecting the product quality requirements

The aim of this study is the evaluation of the parameters of core mixtures using different binder systems with regard to the collapsibility of cores after casting and the resulting product quality of castings reflecting surface requirements based on non-ferrous alloys. The research compares organically bonded core mixtures based on phenol-formaldehyde resins for the production of cores with the shell molding (resin coated sand), currently used in the production of aluminum alloy castings in the Brembo Czech s.r.o., and mixtures using innovative inorganic binder systems based on geopolymers; GEOPOL(R) W. The aim of the research is to compare the advantages and disadvantages of these binder systems in order to evaluate the potential of inorganically bonded mixtures to replace organically bonded mixtures, which would lead to a significant reduction in the environmental impacts of industrial production of castings.Web of Science115art. no. 73

Technological and quality aspects of the use of innovative inorganic binders in the production of castings

The production of cores for the pre-casting of holes in castings places high demands on the quality of the molding mixtures used. For this reason, organic binders are still used to a large extent, which, although they meet the technological requirements, are a source of pollutant emissions during the production of castings. The current trend towards greening production is therefore looking for a suitable alternative in 'green' inorganic binders. Although for many decades standard inorganic binders could not be compared with organic resins in terms of technological properties, new inorganic binder systems are currently being developed that can largely eliminate these disadvantages, which include, in particular, significantly lower collapsibility and reclaimability, and lower mechanical strength values. Last but not least, the use of these binder systems may be limited by the technological parameter of shelf-life, which is the main focus of this study. The aim of this paper is to evaluate the influence of technological parameters of core production using a new generation of inorganic binder systems on their shelf-life. Shelf-life, defined as the change in mechanical strength and wear resistance as a function of exposure time in a given environment, is evaluated under different climatic conditions.Web of Science1111art. no. 177

Water activity of Czech dry-cured meat products: Influence of sampling point and sample preparation method

Water activity (aw) is a key factor influencing dry-cured meat products' safety. However, the standards for determining aw do not specify how the laboratory sample for self-analysis should be prepared and adjusted for determination in this type of food. This work aimed to verify whether the place of sampling and method of sample preparation of dry-cured meat products can influence the measured value of aw. For this purpose, samples of dry-cured heat-treated and fermented meat products were purchased from the local market. Samples before analysis were taken from the edges and centre of the meat products, and preparation consisted of: i) homogenisation; ii) dicing (4 × 4 × 4 mm); iii) slicing. The results of this work indicate that aw is significantly affected by both the part of the product from which the sample is taken and the method of preparation of the sample itself (P < 0.05). The highest measured values of aw were determined in samples prepared by slicing, and the lowest values were determined in homogenised samples. The place of sampling significantly affects the aw, especially for dry-cured heat-treated products

Optimiranje postopka žarjenja mavčnih form za izdelavo kovinskih pen z nepravilno strukturo celic

Metallic foams are the materials, the research of which is still ongoing, with a broad applicability in many different areas (e.g., automotive industry, building industry, medicine, etc.). These materials have interesting potentials due to a combination of properties, which are, on the one hand, related to their metallic character and, on the other hand, to the porous structure. Since the discovery of porous metallic materials numerous methods of production have been developed. This work deals with the optimization of the foundry method for the manufacture of metallic foams using the evaporable polymeric pattern. This technology was used for the manufacture of metallic foams with an irregular cell structure and with fully open pores. Attention, in the experimental part, is devoted particularly to the chosen moulding material – plaster. We checked the suitably of the proposed procedure of manufacturing a plaster mould, the drying process and the subsequent annealing that significantly influence the final properties of the mould and, therefore, the quality of the resulting casting of the metallic foam.Kovinske pene so materiali, ki se še preiskujejo in imajo široko podro~je uporabnosti na razli~nih podro~jih (npr. avtomobilska industrija, gradbena industrija, medicina in podobno). Ti materiali so perspektivni zaradi kombinacije lastnosti, ki imajo po eni strani kovinske lastnosti, po drugi pa porozno strukturo. Od odkritja poroznih kovinskih materialov so se razvile {tevilne metode njihove izdelave. Delo obravnava optimizacijo livarske metode izdelave kovinske pene z uporabo izparljivega polimernega modela. Ta tehnologija je bila uporabljena za izdelavo kovinske pene z nepravilno celi~no strukturo in popolnoma odprtimi porami. V eksperimentalnem delu je pozornost usmerjena v izbiro mavca kot materiala za model. Preverjen je bil predlagani postopek izdelave mavčnega modela, postopka sušenja in žarjenja, ki imajo največji vpliv na končne lastnosti modela in na kvaliteto ulivanja kovinske pene.Web of Science49453052

Bacteriophages as a Strategy to Protect Potato Tubers against <i>Dickeya dianthicola</i> and <i>Pectobacterium carotovorum</i> Soft Rot

The protective effect of bacteriophage suspensions (Ds3CZ + Ds20CZ and PcCB7V + PcCB251) on phytopathogenic bacteria causing soft rot of potato tubers, namely Dickeya dianthicola (D50, D200) and Pectobacterium carotovorum (P87, P224), was observed in ex vivo and in vitro experiments. Ex vivo tests were performed (with air access) on potato slices, on cylindrical cuts from the center of the tubers, and directly in whole potato tubers. In vitro experiments were carried out in a liquid medium using RTS-8 bioreactors, where bacterial growth was monitored as optical density. In particular, the inhibitory effects of phages were confirmed in experiments on potato slices, where suppression of rot development was evident at first glance. Phage treatment against selected bacteria positively affected potato hardness. Hardness of samples treated with bacteria only was statistically significantly reduced (p p < 0.001 for D200 and P87). Ex vivo experiments confirmed significant inhibition of P87 symptom development, partial inhibition of D200 and D50 in phage-treated tubers, and no effect was observed for P224. The inhibitory effect of phages against bacteria was not observed in the in vitro experiment

Preparation of cast metallic foams with irregular and regular inner structure

The aim of this paper is to summarize the possibilities of foundry methods for the production of metallic foams. At present, there are a number of production technologies for this interesting material, to which increasing attention has been paid in recent years. What is unique about metallic foams is the combination of their physical and mechanical properties. As part of our research, we designed and verified four main methods of metallic foam production by the foundry technology, whose products are metallic foam castings with regular and irregular arrangements of internal cavities. All these methods use materials and processes commonly used in conventional foundry technologies. The main idea of the research is to highlight such technologies for the production of metallic foams that could be provided by manufacturing companies without the need to introduce changes in production. Moreover, foundry methods for the production of metallic foams have the unique advantage of being able to produce even complex shaped parts and can thus be competitive compared to today's established technologies, the output of which is usually only a semi-finished product for further processing. This fact was the main motivation for the research.Web of Science1422art. no. 698