ASSESSMENT OF THE PROPERTIES OF CERAMIC COATINGS USED FOR FOAMED POLYSTYRENE PATTERNS IN THE FULL MOULD TECHNOLOGY

摘要

In the full mould technology covering a foamed polystyrenepat-tern with a ceramic refractory coating plays an important part anddecides on the quality of the produced castings. From one hand the coatingrequires appropriate strength, and from the other one good permeability ofgaseous products which are formed as a result of thermal destruction of apattern. In the article an attempt has been undertaken to determine theassessment criteria of usefulness of these coatings. A device, which makesthe co-operation with the apparatus for determination of moulding sandspermeability possible, has been designed and made. The suitable indiciesW_R and W_(Rl) have been elaborated to make the comparison of thestrength of various tested coatings possible. Several kinds of ceramiccoatings have been used m testing.The carried out tests have indicated the fill usefulness of themethod and apparatus for testing both the strength andpermeability of the layers of ceramic refractory coatings usedfor foamed polystyrene patterns in the full mould technology.