Water gas saturation as a lever for controlling the level of properties of frozen foundry molds

Abstract

The purpose of the work is to increase the survivability of sand-clay forms that freeze in equipment without the use of liquefied gases. Quartz sand 1K3O3016, bentonite clay BS2T2, kaolin clay KS2T2, tap water, carbonated water and degassed (boiled) water were used in the research. Flowability was determined according to GOST 23409.9, compressive strength — GOST 23409.7, gas permeability — GOST 29234.11. In order to achieve the specified level of the main parameters of sand-clay mixtures frozen at –15 °С with a simultaneous increase in the survivability of frozen casting molds and rods up to ~18 min, it is most appropriate to use a mixture of 5 % bentonite clay of the BS2T2 brand and 5 % of degassed (boiled) water with clay activation in such water as part of the mixture for 24 hours. At the same time, the use of KS2T2 kaolin clay as part of mixtures is impractical, since mixtures with such clay do not meet the requirements for molding and core mixtures. Molding mixtures consisting exclusively of sand and water are not suitable for the production of casting molds and rods due to high flowability. To increase the strength and reduce the flowability, it is necessary to use a mixture of sand, water and clay for the production of frozen molds and rods. Addition of bentonite (BS2T2) or kaolin (КS2Т2) clay to sand and water leads to a decrease in the flowability of frozen mixtures and an increase in their strength. Frozen at –15 °C mixtures with a kaolin clay content of up to 7 % (by mass) and 5 % (by mass) of tap water are characterized by increased flowability, which makes it impossible to use them as a molding or core mixture. When adding 5 % of bentonite clay BS2T2 swollen with degassed water to quartz sand, the flowability of the frozen mixture becomes less than 0.1 %, the gas permeability reaches 129 units, and the compressive strength exceeds 4.0 MPa, which meets the requirements for molding and rod mixtures. The gas saturation of water is a powerful lever in the system of controlling the level of properties of frozen casting molds, which include quartz sand and swollen bentonite clay.