The effect of different binder levels on the heat absorption capacity of moulding mixtures made by the phenolic urethane cold-box process

Abstract

The phenolic urethane cold-box (PUCB) process was first introduced to the foundry industry in the late 1960s. Since then, it has become one of the most popular methods to make foundry purpose sand moulds and cores, utilized in the manufacturing of aluminium and cast iron cast components. The factors to be considered, affecting the general performance of a PUCB moulding mixture, are the temperature of sand, the moisture content, the mixing conditions, etc. Moreover, there are variable production parameters such as binder level, to improve certain properties of the mould and/or the core based on their specific area of application. These are mainly mechanical properties such as tensile or splitting strength. They have significant influences on the behaviour of the moulding material and are usually tested at room temperature. Although the production phases of the PUCB system are refined to a high extent today, the effect of binder content on the quality of the mould/core and the final casting should be supported by new approaches also in thermal sciences, interpreted in high-temperature environment. In this work, different PUCB mixtures were produced to evaluate the effect of various binder levels on the thermophysical properties of sand cores. Thermogravimetry, differential thermal analysis and a novel application of Fourier thermal analysis were used to study the decomposition processes of the PUCB mixture and to reveal the impact of binder level on the heat absorption (cooling) capacity of sand cores at temperatures relevant in the manufacturing of cast iron parts (1300 ± 10°C).

Novel Measurement Method to Study Thermal Aspects of Molding Mixture Decomposition

“…[8][9][10] https://journals.agh.edu.pl/jcme Protective pipes of quartz glass with a wall thickness of 1 mm (t1 and t2 in Figure 1) were used to protect the thermocouples as the specimens are immersed into liquid metal during the measurement. The diameters of the protective pipes (øp1 and øp2 in Figure 1) were chosen according to previous works [8][9][10]. The size variations of the specimens and their direct contact with the liquid metal (as a heat source) during the tests ensured real foundry conditions.…”

Thermoanalytical tests (TG–DTG–DSC, Py-GC/MS) of foundry binders on the example of polymer composition of poly(acrylic acid)–sodium carboxymethylcellulose

“…The activities are carried out to create new binders that are environmentally friendly in their original form and do not generate harmful substances in the technological process. It is important to minimize the emission of gaseous products of thermal decomposition during the pouring process of liquid metal [14][15][16][17][18].…”

Thermoanalytical studies (TG–DTG–DSC, Py–GC/MS) of sodium carboxymethyl starch with different degrees of substitution

“…From the point of view of pouring a liquid alloy casting into foundry sand molds, important issue is it is to determine the thermal stability of a binder during process. Namely, course of thermal decomposition of the organic binder in molding sand determines the result in the formation of significant casting defects, knock-out properties or adversely affect the efficiency of thermal reclamation methods of used molding sands [21][22][23][24][25]. In terms of environmental protection and the assessment of the binder's harmfulness, it is also important to determine the quality (composition) of the decomposition products of the binding material released during rapid heating.…”