Core mixture preparation plays a crucial role in the manufacturing process for achieving acceptable products that meet the required quality standards. The use of pure quartz sand consistently results in surface defects on castings. Therefore, ongoing efforts are made to identify new methods to prevent these defects. One such approach involves the addition of non-quartz sands to the core mixtures. This article presents the results of testing the physico-chemical properties of quartz and non-quartz sands, as well as their mixtures in various ratios, on the surface quality of cast iron castings. The tests were conducted on five types of foundry sands and twelve core mixtures, with 90%, 60%, and 30% quartz sand content. In addition to determining the chemical composition of the sands using AAS elemental analysis, other parameters such as loss on ignition, bulk density, porosity, thermal dilatation, sieve analysis, bending strength, and the surface quality of 24 castings were examined. The results indicate that the presence of acidic SiO2 oxides in the sands, lower bulk density and porosity, irregular thermal expansion of sands, higher mean grain size (d50), lower grain size regularity, and lower bending strength increase the risk of veinings. Properties such as loss on ignition, sand porosity, AFS value, content of particles below 0.09 mm, log w, Sth, MKcalc, nth, Sw, Kh, and the proportion of coarse, medium, fine, and very fine particles were found to have no significant impact on the veining elimination.

This study investigates and compared various properties of high-quality foundry sands on the surface quality of castings, whose cores are produced using the col-box method. Methods such as the measurement of flushable fraction, sieve analysis, electron and optical microscopy, pH and electrical conductivity measurements were used to monitor the physico-chemical properties of silica and non-silica sands. 5 core mixtures were prepared from individual sands by adding 1.6 % of organic binder based on phenol-formaldehyde formed from resin and hardener using an MR100 mixer. The produced cores were placed in moulds made of a uniform bentonite mixture and cast (15 test castings). In all the tested sand samples, the dust content was visible at a 300x magnification, but the share of flushable content is not exceeded 3 %, which is one of the fundamental conditions for moulding. All the tested sands are heat resistant at 1600 °C and had a low flushable fraction in the range 0.05-0.3 %. The results indicate that the occurrence of surface defects in high-quality foundry sands is not related to the flushable fraction content, to the average grain size value d₅₀, to the electrical conductivity, to the shape of the sand grains and to the flexural strength. The surface roughness is related to the average grain size, to the grain shape and to the flexural strength.

The main problem in the cores production by cold-box method is the occurence of surface defects due to the tension generated by thermal expansion of the silica sand. One of the possibilities of eliminination is exchange of silica sand from another location. Another interesting factor is the type of used binder and its amount. However, even these measures donʹt guarantee sufficient quality. Foundries most often solve this problem by adding expensive additives to the core mixture. Foundries may have a dilemma in choosing the right additive. The aim of this paper was to investigate the effect of silica sand from two different locations, the effect of dosing the amount of binder and the addition of several types of commonly available additives on the quality of casting cavities. For this purpose, a total of 11 differently composed core sand mixtures were prepared, but only one of these mixtures was successful.

This article presents a analysis of the impact of varying amounts of a specific additive in the core mixture and adjustments in shooting pressure on the elimination of surface defects in castings, particularly veinings. These defects, often located in inaccessible areas of the casting, cannot be effectively removed through conventional methods like punching, making the optimization of the core mixture composition crucial. Additives are frequently incorporated into the core mixture, as they have become an essential component in its production. For the core mixture to be effective, it is not only essential to identify the appropriate type of additive but also to precisely determine the optimal quantity of the additive and accurately set other critical production parameters, such as shooting pressure.This study investigates the influence of additive concentration and shooting pressure on the surface quality of cast iron castings, employing the cold box method for core production. The findings reveal that higher shooting pressure contributes positively to the reduction of veining defects. However, an increased additive content in the core mixture does not necessarily ensure vein-free castings. The additive also plays a role in reducing the gas content within the core, and increased core hardness is associated with a decrease in the occurrence of veining defects. The casting with the highest surface quality and the fewest veinings was produced using cores made from a mixture with 1% additive content, subjected to a shooting pressure of 4 bars.

Present hectic times do not allow the foundrymen to test various modifications of gating system in real production due to lack of time and efficiency of production phase. When testing of tens or hundreds of modifications is needed, simulation software MAGMA5 and its optimization procedure comes into place. This article deals with choosing the best design of gating system which will ensure the filling of the sprue as soon as possible together with possible shortening of pouring time on Disamatic line. Soonest filling of the sprue will ensure that no air is entraped in the molten metal which is entering the cavity of the mold and no air bubbles would occur in the final casting after pouring. With this goal achieved, foundry can secure the production of castings. There is a big chance chance to decrease the pouring time of the mold, which will make the production more effective.

Modern foundries are being challenged by current trends such as lightweight construction, advanced core and casting design with controlled material properties, and high precision requirements. Core production plays a critical role in casting, as the cores have a significant impact on the final quality. One key factor is the choice of materials for molds and cores, with silica sand being the most commonly used. However, even the highest-quality silica sand cannot always prevent defects in the final casting. A possible solution to reduce such defects is the addition of additives to the mold and core mixtures. This paper explores the effects of commonly available additives on the surface quality of test castings. In the study, five additives were tested, including energy ash, and 14 test castings were evaluated using visual comparators to assess surface quality.