Dilatometric studies of plaster sandmix in raw and heat treated state

• Autorzy: Pawlak M. , Niedźwiedzki Z.
• Języki publikacji: EN

Abstrakty

EN

Results of dilatometric studies of bounded plaster sandmix applied in precision pressure below atmospheric casting, are presented in this paper. Sandmix composed of half-hydrate alpha-CaSO4ź2H2O with different parts of silica SiO2 was a subject of investigations. Silica is a factor weakening the influence of phase transformations on total distortion of the mould during heating and thus influences the accuracy of prepared cast. Experimental moulders of dimensions 735 made of plaster sandmix with silica fraction equal 30; 40; 50; 60 and 70% were used during studies. Sandmix was tested in raw state and after heat treatment changing the alpha-half hydrate into anhydrite II (CaSO4). It was demonstrated that addition of the silica at level about 50% influences most advantageously on dimension changes of heated sandmix by lowering dilatations 3 times in comparison with sandmix composed of pure alpha-half hydrate. The transformation of plaster structure into anhydrite II is also important - the shrinkability phase disappears and expansion similar to linear-like appears. It was determined that it is possible to obtain sandmix of small, stabile distortion on the way of appropriate selection of components and heat treatment parameters what improves dimensional and shape accuracy limits of the cast and significantly limits internal stresses in the mould eliminating risk of its cracking.

Słowa kluczowe

EN

foundry technologies; foundry materials; precision casting; plaster mould; dilatation

PL

technologie odlewnicze; materiały odlewnicze; odlewy precyzyjne; forma odlewnicza

• Wydawca: Komisja Odlewnictwa Polskiej Akademii Nauk Oddział w Katowicach
• Czasopismo: Archives of Foundry Engineering
• Rocznik: 2008
• Tom: Vol. 8, iss. 3
• Strony: 145--148
• Opis fizyczny: Bibliogr. 6 poz., rys.,

Twórcy

autor

Pawlak M.

autor

Niedźwiedzki Z.

• Department of Materials Engineering and Production Systems, Technical University of Łódź, Stefanowskiego 1/15 Str., 90-924 Łódź,

Bibliografia

• [1] K. Akerman: Gips i anhydryt (Gypsum and anhydrite), PWN, Warszawa 1964.
• [2] L. Lewandowski: Moulding materials) Akapit, Warszawa 1997 (in Polish).
• [3] M. Wiktorski, M. Pawlak, Z. Niedźwiedzki: Effect of plaster moulds compositions on thermal dilatation plaster moulds used in precision casting, Archives of Foundry, 2005, Vol. 5, Nº 17, 232-240, (in Polish).
• [4] F. Nadachowski: (utline of engineering of refraktory materials) Wyd. Śląsk, Katowice, 1998 (in Polish).
• [5] M. Pawlak: Influence of temperature and time of fi ring on the properties of gypsum. Resarch in Polish Metallurgy AT the Beginning of XXI Century. Committe of Metallurgy of the Polish Academy of Science, AKAPIT, Cracow, 287-293 (in Polish).
• [6] M. Wiktorski, M. Pawlak, Z. Niedźwiedzki: Derivatograph investigation of plaster moulds composition for plaster moulds used in precision casting Archives of Foundry, Polish Academy of Science, 2004, Vol. 4, Nº 13, 225-232, (in Polish).