Casting cores produced in additive manufacturing are more often used in industrial practice, in particular in the case of the production of unit castings and castings with very complex geometry. The growing interest in the technology of 3D printing of cores and molds also brings emerging doubts related to their mechanical and technological properties. This article presents a comparison of the properties of cores made of sand with acid-curing furfuryl resin, made with 3D printing technology; the cores were prepared in a conventional way (mixing and compaction). The main purpose of this research was to determine the possibility of using shell cores as a substitute for solid cores, aimed at reducing the amount of binder in the core. The influence of the type of the binder and the size of the grain matrix fraction on the obtained mechanical and technological properties of the cores, with particular emphasis on abrasion and thermal deformation, as well as on the kinetics of their hardening, was demonstrated.

This article presents the findings of a study focusing on the gas generation of 3D-printed cores fabricated using binder-jetting technology with furfuryl resin. The research aimed to compare gas emission levels, where the volume generated during the thermal degradation of the binder significantly impacts the propensity for gaseous defects in foundries. The study also investigated the influence of the binder type (conventional vs. 3D-printed dedicated binder) and core construction (shell core) on the quantity of gaseous products from the BTEX group formed during the pouring of liquid foundry metal into the cores. The results revealed that the emitted gas volume during the thermal decomposition of the organic binder depended on the core sand components and binder type. Cores produced using conventional methods emitted the least gases due to lower binder content. Increasing Kaltharz U404 resin to 1.5 parts by weight resulted in a 37% rise in gas volume and 27% higher benzene emission. Adopting shell cores reduced gas volume by over 20% (retaining sand with hardener) and 30% (removing sand with hardener), presenting an eco-friendly solution with reduced benzene emissions and core production costs. Shell cores facilitated the quicker removal of gaseous binder decomposition products, reducing the likelihood of casting defects. The disparity in benzene emissions between 3D-printed and vibratory-mixed solid cores is attributed to the sample preparation process, wherein 3D printing ensured greater uniformity.

The article presents the results of a study aimed at determining the impact of storage conditions on the gas-forming tendency of standard samples (cores) made from moulding sand using a two-component binder based on resole-type phenolic resin, cured with a dedicated ester mixture. The objective of the research was to determine the total volume of gases released as a result of contact between the cores or moulds and the high temperature of molten casting alloys, as well as the rate of gas release, which can influence the tendency for gas-related casting defects. Additionally, the influence of storage conditions on the gas-forming tendency of the samples was evaluated in terms of their environmental and occupational health impact, based on the emission of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), which serve as key indicators of the harmfulness of moulding and core sands to the surrounding environment.

This study investigates the influence of binder reactivity and storage conditions on the mechanical and technological properties of foundry cores made with two phenol–formaldehyde resole resins differing in reactivity. Cylindrical specimens were produced using the Alpha-Set process and tested for tensile and splitting strength, gas permeability, abrasion resistance, and thermal deformation after 1 h of curing and 24 h of storage under three climatic conditions (temperature (°C) and relative humidity (RH) are given using standard notation): A (25 °C, 90% RH), B (0 °C, 10% RH), and C (15 °C, 50% RH). The bench life of the mixtures ranged from 6.5 min for the high-reactivity resin to 8.0 min for the low-reactivity resin, indicating that higher reactivity shortens the technological window but enables faster strength development. After 48 h of curing under moderate conditions (C), cores made with the high-reactivity resin achieved a tensile strength of 0.51 MPa, compared with 0.35 MPa for the low-reactivity binder. Under high humidity (A), this trend reversed—the less reactive resin reached a higher splitting strength (4.27 MPa vs. 2.95 MPa) and exhibited lower friability (0.9% vs. 3.0%), confirming greater resistance to moisture-induced plasticization. The high-reactivity resin, however, showed smaller maximum thermal deformation (≈−2 mm vs. ≈−5.5 mm), although the onset of instability occurred earlier during heating. In cold and dry conditions (B), the low-reactivity resin provided higher tensile strength (0.23 MPa vs. 0.12 MPa) and lower friability, whereas the high-reactivity resin exhibited lower thermal distortion. Binder selection should therefore reflect the prioritized property—dimensional stability or mechanical strength and abrasion resistance. A comparative evaluation of all measured parameters indicated that the most balanced performance was obtained under moderate storage conditions (15 °C, 50% RH), representing the optimal processing route for phenolic resin-bonded cores.

The properties of chemically bonded core sands strongly depend on the reactivity of phenol-formaldehyde resole binders and on the granulometry of the sand matrix. This study presents an evaluation of the mechanical, technological, thermomechanical, and thermophysical properties of core sands prepared using two resole binders with different reactivity levels (Resin 1—lower reactivity; Resin 2—higher reactivity) and two fractions of quartz sand (BK 40 and BK 45). The investigations included the kinetics of strength development (1–48 h), friability, permeability, thermal deformation (DMA), and the determination of thermophysical coefficients (λ₂, a₂, b₂) based on temperature field registration during the solidification of a copper plate. The results indicate that sands containing the higher-reactivity binder exhibit a faster early strength increase (≈0.42–0.45 MPa after 1–3 h), whereas sands bonded with the lower-reactivity resin reach higher tensile strength after 24–48 h (≈0.58–0.62 MPa). Specimens based on BK 45 quartz sand achieved higher tensile strength; however, the finer grain fraction resulted in increased friability (up to ≈3.97%) and a reduction in permeability by 30–40%. DMA analysis confirmed that sands based on BK 40 exhibit delayed and more stable thermal deformation. Thermophysical parameters revealed that BK 45 provides significantly higher thermal insulation, extending the solidification time of the Cu plate from 71–73 s to 89–92 s compared with BK 40. Overall, the results indicate that the combination of BK 40 quartz sand and a lower-reactivity resin offers an optimal balance between thermal conductivity and thermal stability, promoting improved technological performance in casting processes. The determined thermophysical coefficients can be directly applied as input data for foundry process simulations.

This study presents a comprehensive analysis of the thermophysical properties of a casting mould based on BK 50 quartz sand and a resol-type phenol-formaldehyde resin. The investigation combines classical laboratory measurements using Differential Scanning Calorimetry (DSC) with in-situ temperature field recording inside a foundry mold during the solidification of a copper plate casting. Based on specific heat capacity data and readings from seven thermocouples, temperature-dependent values of thermal diffusivity (a), heat capacity (b), and thermal conductivity (λ) were determined. The results indicate a low thermal conductivity of the tested material and a strong temperature dependence of its thermophysical properties. A significant influence of residual moisture was observed during the initial heat exchange phase, manifesting as disturbances in the heating curves around 100 °C. The adopted methodology enabled a realistic mapping of thermal conditions during solidification and confirmed the stable course of the process. The identified thermophysical coefficients characterize the material and are crucial for providing accurate input parameters in numerical simulations of casting processes. Furthermore, they support the informed selection of molding materials in industrial applications, contributing to more reliable simulation outcomes and improved process design, material selection, and final casting quality. The findings validate the integration of laboratory measurements with in-situ analysis and point to the necessity of further research involving various binders, sand grain size distributions, and elevated pouring temperatures.