Search Results

You are looking at 1 - 5 of 5 items for

  • Author: N. Kaźnica x
Clear All Modify Search
Open access

N. Kaźnica and J. Zych

Abstract

The results of researches of sorption processes of surface layers of components of sand moulds covered by protective coatings are presented in the hereby paper. Investigations comprised various types of sand grains of moulding sands with furan resin: silica sand, reclaimed sand and calcined in temperature of 700°C silica sand. Two kinds of alcoholic protective coatings were used - zirconium and zirconium - graphite. Tests were performed under condition of a constant temperature within the range 30 - 35°C and high relative air humidity 75 - 80%. To analyze the role of sand grains in sorption processes quantitavie moisture sorption with use of gravimetric method and ultrasonic method were used in measurements. The tendency to moisture sorption of surface layers of sand moulds according to the different kinds of sand grains was specified. The effectiveness of protective action of coatings from moisture sorption was analyzed as well.

Knowledge of the role of sand grains from the viewpoint of capacity for moisture sorption is important due to the surface casting defects occurrence. In particular, that are defects of a gaseous origin caused by too high moisture content of moulds, especially in surface layers.

Open access

N. Kaźnica and J. Zych

Abstract

The results of investigations of the sorption process of surface layers of sand moulds covered by zirconium and zirconium - graphite alcohol coatings are presented in the paper. Investigations comprised two kinds of sand grains (silica sand and reclaimed sand) of moulding sand with furan resin. Tests were performed under conditions of a high relative air humidity 75 - 85% and a constant temperature within the range 28 – 33°C. To evaluate the effectiveness of coatings protective action from moisture penetration into surface layers of sand moulds gravimetric method of quantitavie moisture sorption and ultrasonic method were applied in measurements.

The optimal number and kind of coatings from the viewpoint of protection from moisture sorption were specified for furan moulding sands with quartz sand and reclaimed sand as well.

Knowledge of proper coatings selection is important due to protection from high air humidity and its adverse effects. What is more, it can allow to select the proper storage conditions of casting moulds waiting for being poured with liquid metals. This can limit the occurrence of surface defects which are caused by too high humidity of casting moulds, especially in surface layer.

Open access

N. Kaźnica, J. Zych and J. Mocek

Abstract

A large number of defects of castings made in sand moulds is caused by gases. There are several sources of gases: gases emitted from moulds, cores or protective coatings during pouring and casting solidification; water in moulding sands; moisture adsorbed from surroundings due to atmospheric conditions changes. In investigations of gas volumetric emissions of moulding sands amounts of gases emitted from moulding sand were determined - up to now - in dependence of the applied binders, sand grains, protective coatings or alloys used for moulds pouring. The results of investigating gas volumetric emissions of thin-walled sand cores poured with liquid metal are presented in the hereby paper. They correspond to the surface layer in the mould work part, which is decisive for the surface quality of the obtained castings. In addition, cores were stored under conditions of a high air humidity, where due to large differences in humidity, the moisture - from surroundings - was adsorbed into the surface layer of the sand mould. Due to that, it was possible to asses the influence of the adsorbed moisture on the gas volumetric emission from moulds and cores surface layers by means of the new method of investigating the gas emission kinetics from thin moulding sand layers heated by liquid metal. The results of investigations of kinetics of the gas emission from moulding sands with furan and alkyd resins as well as with hydrated sodium silicate (water glass) are presented. Kinetics of gases emissions from these kinds of moulding sands poured with Al-Si alloy were compared.

Open access

J. Kolczyk, Ł. Jamrozowicz and N. Kaźnica

Abstract

The results of investigations of the rheological properties of typical ceramic slurries used in the investment casting technology - the lost wax technology are presented in the paper. Flow curves in the wide range of shear velocity were made. Moreover, viscosity of ceramic slurries depending on shearing stresses was specified. Tests were performed under conditions of three different temperatures 25, 30 and 35°C, which are typical and important in the viewpoint of making ceramic slurries in the investment casting technology.

In the light of the performed investigations can be said that the belonging in group of Newtonian or Non - Newtonian fluid is dependent on content of solid phase (addition of aluminum oxide) in the whole composition of liquid ceramic slurries.

Open access

Ł. Jamrozowicz, J. Kolczyk, N. Kaźnica and Z. Pyziak

Abstract

Measurements of the hardening process of the selected self-setting sands are presented in the hereby paper. Moulding sands were prepared on the matrix of „Szczakowa” sand of the Sibelco Company. Two resins: phenol-formaldehyde-furfuryl (FF/AF) and urea-formaldehydefurfuryl (MF/AF) were used for making moulding sands. - Methylbenzene-sulphonic acid was applied as a hardener for the moulding sand on FF/AF resin, while paratoluene-sulphonic acid for the moulding sand on MF/AF resin. Both hardeners were used in two concentrations: low - the so-called ‘slow’ hardener and high - ‘fast’ hardener. During investigations, the courses of the hardening process were determined, more accurately changes of the velocity of the ultrasound wave passage through the moulding sand cL = f(t) and changes of the moulding sand hardening degree versus time, Sx = f(t). In addition, the kinetics of the hardening process was determined. Measurements were performed on the research stand for ultrasound investigations.