Analysis Of Sand Casting Defects On The Basis Of Moulding Sand Properties

Abstract

In this research casting defects were studies by changing the green sand properties like permeability, grain size or structure, moisture content and pouring temperature molten metal. Pure Aluminium metal has taken to study defects like porosity, shrinkage, and blow holes. In order to minimize and reduce these casting defects, various process parameters were studied like Grain Fineness Number of sand, permeability of green sand mixture, Power driven Sieve shaker, Permeability meter, Muller machine, were used to study the surface defects on the cast. These ingredients are properly prepared by using a sand mixing machine or by hand in a foundry shop. The manual hand test is carried out to check the hardness of the green sand mixture so that it can resist metlstatic pressure of a molten metal which is three times more than the hydro static pressure. Pattern is placed in the drag part of the flask and a thin film of chalk dust or powder is sprinkled over the pattern. Then green sand mixture is packed into the molding flasks and gentle ramming is done by hand rammer. Two halves of the pattern are assembled by dowel pins and cope and drag parts are placed on one another. Flask latches helps in aligning the two halves.Permeability of sand is function of the degree of ramming, therefore specimen were prepared according to standard conditions. A laboratory sand rammer was used along with a split specimen tube to get standard ramming conditions and standard sized specimens. For this purpose three samples of Aluminum product were casted from sand of different grain size and structure. It has seen that casting defects like Blow holes was more when Grain Fineness Number (GFN) was high &Permeability Number was low. If pouring temperature remains more than melting temperature of Aluminum it creates more porosity in the end product but if pouring temperature is too near to melting temperature then another defect like cold shut occurs. Permeability of molding sand depends on number of factors like shape & size of sand grains or granules, ramming of sand moisture content, and amount of binder particles.