Modern Trends in Foundry

1. Introduction and Scope

The production volume of metals and their alloys, taking into account the current demand for materials containing steel, cast iron, non-ferrous metals and their alloys, will continue to increase in the near future. Today, the requirements for the quality of metallic materials in order to achieve the maximum production efficiency are constantly increasing, and the expectations for low costs continue to be higher and higher. From the point of view of individual metallurgical technologies, foundries represent the fastest way to produce the required parts of components. More and more complex forms are cast that cannot be made with other technologies to obtain an economical and more advantageous solution.

The purpose of this Special Issue was to present the foundry branch in its whole range and variety, covering the trends in modern foundry technologies and focusing on various metallurgical aspects of the production process, refining and casting.

2. Contribution to the Special Issue

The papers presented in this Special Issues present trends in modern foundries, research results and their industrial verification and application supplemented with modern methods presenting simulations of metallurgical processes.

In paper [1], the authors compare the technological and material properties of CMnCr steels without bismuth with those with 0.08 wt. % Bi and 0.12 wt. % Bi. Experimental melts showed that the most advantageous fusion of Bi into the melt took place in the ladle, with an efficiency of about 20%. The optimal temperature range for steel forming was 1160–1050 °C. With the increase in the Bi content, the deformability of steel and plastic properties decreased, while the yield strength and tensile strength increased. The microstructure of all tested steels was ferritic-pearlitic with bainite islands. The machinability tests assessed with the degree of tool wear showed that the most advantageous steel was the CMnCr steel with the addition of 0.08 wt. % Bi.

Article [2] focuses on the search for new ecological inorganic binders for the production of cores for pre-forming the interior shapes of castings. The evaluation of the influence of technological parameters of core production with the use of new-generation inorganic binding systems on their durability is presented. Durability was defined as the change in mechanical strength and wear resistance as a function of exposure time in a given environment and was assessed in different climatic conditions. It was stated that due to the curing mechanism of the system with inorganic binders (a reversible process), the relative humidity of the environment turned out to be a key factor in maintaining optimal storage conditions for the cores. By adjusting the appropriate storage conditions, the durability of cores can be extended from 24 h to several dozen days, which in normal foundry practice corresponds to the durability of cores produced using polyurethane cold box (PUCB) technology.

Subjects related to core binders were also dealt with by the authors of article [3]. The aim of this work was to evaluate the parameters of core mixtures with various binder systems in terms of core collapse after casting and the obtained quality of castings reflecting surface requirements based on non-ferrous metal alloys. This article compares organic core mixtures based on phenol–formaldehyde resins for the production of shell casting cores used for the production of aluminum alloy castings at Brembo Czech s.r.o. and blends using innovative inorganic binder systems based on GEOPOL^® W geopolymers. According to the comparison of the measurement results of the transverse strength of the tested mixtures, the RCS (resin-coated sand) mixtures achieved over 30% lower cold and hot strengths. Thus, with the requirements for the same strength, it was possible to reduce the dose of the GEOPOL^® W20 binder, which should also have a positive effect on the collapse. Comparing the advantages and disadvantages of these binder systems to assess the potential of inorganically bonded mixes to replace organically bonded mixes allowed for a significant reduction in the environmental impact of the industrial production of castings.

Article [4] focuses on the numerical simulation of casting in new foundries. Numerical techniques used as tools for process design and improvement are constantly evolving to include the modeling of more dynamic systems for industrial applications. This article presents a fresh approach to the numerical simulation of dynamic processes using the evolving and dynamic mesh technique. The dynamic mesh technique (DMT) proposed by the authors of [4] for casting applications paves the way for the easier implementation of dynamic generative systems into mainstream software tools. The authors briefly outline some technical aspects of the new DMT approach and its dynamic mesh strategy and discuss the industrial application of the method to semi-continuous casting processes.

Article [5] focuses on metallic materials with micron, submicron or amorphous grains, and in particular fine-grained, quasiamorphic strips of Mg-based alloy, produced in the process of casting strips with twin rolls, using simulation and experimental methods, were investigated. Based on the results of the simulation, the authors conducted an experiment of casting twin roll strips on the Mg-rare-earth alloy. A novel, puddle-like microstructure (comprising a crystalline matrix composite containing quasiamorphous particles) of the cast alloy strip was obtained. According to the authors of [5], this type of Mg-based alloy structure has never been reported before. Tensile test results showed that the novel as-cast Mg–rare earth strip exhibited superior tensile properties to those of amorphous matrix composite sheets and conventional as-cast alloys.

Article [6] focuses on the subject related to the use of inorganic binders in the core production process. In this article, the strength, permeability and thermal stability of siliceous and non-silica sands with round and angular grains, as well as fine and coarse grains, were tested using an inorganic binder. The obtained results provide useful information on the possibilities of using and combining various types of molding sands, both silica and non-silica. The investigations show that the addition of a fine sand can lead to an improvement, but also to a decline in the physical properties of a base coarse sand, depending on the choice of the added fine sand. This information can help to avoid typical casting failures. By influencing selected properties of the sand core, they can help solve problems in the core production process, as well as in obtaining a high-quality final product—the casting.

In article [7], the authors characterized a composite with dispersion phases cast by mixing on an aluminum matrix. The mixture of aluminum with FexAly and SiC powders was obtained through the process of mechanical alloying and self-propelled high-temperature synthesis (ASHS). A cast silumin structure was obtained, in which the matrix contained micro-areas of ceramic phases and intermetallic phases, which are characteristic of hybrid reinforcement. Fragmentation of dendrites in the α solid solution was found along with the transition from the two-component eutectic composition of the plate α(Al) + β(Si) to the modified eutectic composition.

3. Conclusions

The Special Issue “Modern Trends in Foundry” and its scientific articles present interesting examples of the most important challenges facing modern foundries. We hope that these articles will inspire scientists, researchers and technologists in this field and that the presented articles will be helpful to them in new research, debates and discussions.