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.

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® 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.

Characterization of the Strength of a Natural Sand and Artificial Sand Core Manufactured with Inorganic Binder

Natural sand and organic binders are commonly used in casting processes, but these ingredients produce environmental problems with dust and harmful TVOC(Total Volatile Organic Carbon) gases. Research on the introduction of artificial sand and inorganic binders to solve these environmental problems is being actively conducted mainly in the casting industry. Artificial sand has superior durability and a spherical shape compared to natural sand, and above all, it does not generate dust. In addition, inorganic binders have the advantage that no harmful gas is generated during casting and the used sand can be recycled. This study confirmed whether inorganic binders can be applied when replacing natural sand with artificial sand. First, eco-friendly inorganic binders that do not produce harmful gas were synthesized. Then characteristic analyses were carried out with artificial sand and natural sand. Physical and chemical properties were compared using X-Ray Fluorescence (XRF), Powder Flow Test (PFT) and particle size distribution analyses. The general strength and absorption (absolute humidity 29.9 g/cm³) strength of the sample core was measured using each sand (artificial sand, natural sand) and inorganic binder. Also, X-ray Photoelectron Spectroscope (XPS) analysis confirmed the combination structure. As a result, it was confirmed that artificial sand exhibited mold characteristics with similar strength even with lower inorganic binder content than natural sand.

A new type of inorganic binder curing agent for soft soil

Aiming at the defects of traditional curing agent in strengthening soft clay, a new type of inorganic binder type soil curing agent has been developed. Compared with P.O 42.5 cement, the new soil stabilizer has smaller fineness and larger specific surface area. The strength of the soil solidified by the new curing agent is lower at the initial stage, but it increases rapidly after 24 hours. When the dosage is 10%, the 28-day strength of the soil solidified by the new curing agent is 2.1 times that of the soil solidified by cement. The soil solidified by the new curing agent can form more calcium hydroxide crystals and hydrated calcium silicate gel with more compact structure. After solidification, there are fewer fine particles in the soil.

Solar absorptive coating: a thermally stable spinel pigment based coating with inorganic binder for waterborne paint

Purpose The spectrally selective solar absorption paint is prepared from spinel-based mixed metal oxides with inorganic binder as a key component. Inorganic binder (furnace cement) is blended with mixed metal oxide pigment during synthesis. High temperature stability upto 1,100ºC is achieved by the use of this modified coating system. The purpose of this paper is to work on solar selective coating synthesis, and application of a coating as a water-borne paint is the additive key feature that helps in reduction of solvent use. Design/methodology/approach The paint was formulated using water-based system, and the main component of colorant was made by mixed metal oxide–based spinel pigment and highly temperature stable inorganic binder. Findings The paint formed shows excellent absorptive power with low emittance even at high temperature. Optical and thermal properties were determined along with adhesion, abrasion and other properties. The solar absorptance for these samples were as = 0.93–0.95 with corresponding thermal emittance of eT = 0.096 (at room temperature) and 0.2–0.22 (at elevated temperature 100°C). Originality/value The paint formed shows excellent absorptive power with low emittance even at high temperature. The paint can be applied in solar absorptive tower system. The obtained results indicated excellent thermal stability of prepared paint coatings. As inorganic binder was used, the paint has reduction in solvent use, and being water as a base, it is environment friendly, easy to apply and durable at high temperatures, as the binder itself is stable up to 1,500ºC.

Influence of Disc Temperature on Ultrafine, Fine, and Coarse Particle Emissions of Passenger Car Disc Brakes with Organic and Inorganic Pad Binder Materials

Passenger car disc brakes are a source of ultrafine, fine, and coarse particles. It is estimated that 21% of total traffic-related PM10 emissions in urban environments originate from airborne brake wear particles. Particle number emission factors are in the magnitude of 1010 km−1 wheel brake during real-world driving conditions. Due to the complexity of the tribological processes and the limited observability of the friction zone between brake disc and pad, the phenomena causing particle emission of disc brakes are only partially understood. To generate a basis for understanding the emission process and, based on this, to clarify which influencing variables have how much potential for reduction measures, one approach consists in the identification and quantification of influencing variables in the form of emission maps. The subject of this publication is the influence of disc brake temperature on ultrafine, fine, and coarse particle emissions, which was investigated with a systematic variation of temperature during single brake events on an enclosed brake dynamometer. The systematic variation of temperature was achieved by increasing or decreasing the disc temperature stepwise which leads to a triangular temperature variation. Two types of brake pads were used with the main distinction in its chemical composition being organic and inorganic binder materials. The critical disc brake temperature for the generation of ultrafine particles based on nucleation is at approximately 180 °C for pads with an organic binder and at approximately 240 °C for pads with inorganic binder materials. Number concentration during those nucleation events decreased for successive events, probably due to aging effects. PM10 emissions increased by factor 2 due to an increase in temperature from 80 °C to 160 °C. The influence of temperature could be only repeatable measured for disc brake temperatures below 180 °C. Above this temperature, the emission behavior was dependent on the temperature history, which indicates also a critical temperature for PM10 relevant emissions but not in an increasing rather than a decreasing manner.

The Effect of the Surface Energy of Water Glass on the Fluidity of Sand

In recent years, the metal casting industry has sought to meet ever more stringent environmental standards. Inorganic binders based on silicate chemistry have many advantages with respect to environmental issues, but often suffer from reduced strength, burn-on and poor water-resistance. In particular, when sand is mixed with a water glass based inorganic binder, it adversely affects fluidity. In this study, a Powder flow test (PFT) analysis was conducted to confirm the effect of the surface tension of water glass on mixed sand. Certain additives were selected as surfactants to lower the surface tension of the water glass. The characteristics of the samples were measured using the PFT. A correlation between the surface tension of the water glass and the fluidity of the mixed sand was established. We then evaluated the effect of the inorganic binder on core strength. Using the surfactants, the fluidity of the mixed sand increased by 66%. However, strength and water resistance were reduced by approximately 45%. As a result, it was found that when 1.5% of surfactant was added, the resulting fluidity and humidity strength characteristics produced a mixed sand with good properties. Water glass with improved fluidity can produce a high quality core and mold. Finally, we used a practical application prove that an inorganic binder can replace organic binders in foundry cores.