Effect of Sand Wetting on Physically Hardened Moulding Sands Containing a Selected Inorganic Binder. Part 1

Abstract

In the paper, an attempt was made to evaluate the effect of preliminary wetting of high-silica base during preparation of moulding sands containing a selected grade of sodium water-glass, designed for hardening by traditional drying or by electromagnetic microwaves at 2.45 GHz. In the research, some water was dosed during stirring the sandmix before adding 1.5 wt% of the binder that was unmodified sodium water-glass grade 137, characterised by high molar module within 3.2 to 3.4. Scope of the examinations included determining the effect of wetting the base on mechanical parameters like compression, bending and tensile strength, as well as on technological parameters like permeability, abrasion resistance and apparent density. The research revealed a significant positive effect of adding water to wet surfaces of high-silica base grains on mechanical properties and quality of moulding sands hardened by physical methods, in particular by microwave heating.

Effect of Sand Wetting on Physically Hardened Moulding Sands Containing a Selected Inorganic Binder. Part 2

“…In a ribbon laboratory mixer, 6 kg of moulding sand was prepared according to [8], as follows: − variant 0%: 1.5 wt% of binder was dosed to the sand base after starting the mixer and stirred for 4 minutes; − variant 0.5%: 0.5 wt% of water was dosed to the sand base after starting the mixer, then, after stirring for 60 s, 1.5 wt% of binder was dosed and stirring was continued for 4 min; − variant 1%: 1 wt% of water was dosed to the sand base after starting the mixer, then, after stirring for 60 s, 1.5 wt% of binder was dosed and stirring was continued for 4 min. Next, longitudinal and octal specimens, formed by vibration compacting on a LUZ-2e stand, were hardened:…”

“…Good wettability of sand base and low viscosity of binder increase probability of creating non-enveloped links [11] between the sand base and the bonding material, which give the sandmix higher strength in comparison to those containing enveloped links. In the paper [8] described is the effect of introducing additional water to the sandbinder system subject to physical hardening (slow traditional drying and much faster microwave heating). The expected result of wetting the sand base with an additional amount of water before adding the binder was improvement of mechanical parameters of the sandmix.…”

“…1.5 wt%, causes problems with maintaining high and fully repeatable quality parameters of casting moulds and cores. In order to stabilise these parameters, an addition of water wetting the sand base was introduced during preparation of the sandmix [8]. It was observed in the paper [8] that quality of linking bridges can be affected by various content of water wetting the high-silica base.…”

“…In order to stabilise these parameters, an addition of water wetting the sand base was introduced during preparation of the sandmix [8]. It was observed in the paper [8] that quality of linking bridges can be affected by various content of water wetting the high-silica base. Analysis of the examination results showed that, in the case of the sandmixes containing 1.5 wt% of water-glass grade 137, introducing small addition of water during stirring before adding the binder resulted in improved quality of the links between sand base grains, created during hardening with physical methods.…”

Effect of Sand Base Grade and Density of Moulding Sands with Sodium Silicate on Effectiveness of Absorbing Microwaves

“…Measurements of iron content, carried-out with an EDS analyser, clearly indicate that the sands originate from the same deposit. Selected inorganic binder (Table 1) thanks to physical methods of hardening can be classified to the highest 1st quality class binders [10,11], determined by bending R g U and tensile R m U strength calculated per 1 wt% of the binder. 6-kg portions of moulding sands for the examinations were prepared in a laboratory ribbon mixer in the following proportions (by mass, per 100 parts of moulding sand): 0.5 part of water were dosed to the base [10,11], then 1.5 parts of binder 137 were dosed in 60 s after starting the mixer and stirring was continued for 4 min.…”