Hollow sand casting

Hollow sand casting is a relatively simple process for making cast metal objects that for thousands of years was the most widely used of all casting methods. For the most basic castings, the molds are made from ordinary silica sand mixed with water so as to keep the sand particles compacted together to maintain the required hollow-shaped form. The hot, fluid... 

The mass flow of emissions from full mould and hollow mould casting processes are to be considered as similar. This can be seen from Figure 3.5 which shows the mass flow of organic carbon as a function of time upon pouring. Time 0 00 corresponds to the starting of the pouring. The data were collected using furan-bonded sands, both for full and hollow mould... 

In open-mold casting, the shape of the desired object is carved as a "negative" depression or hollow into a suitable bulk of material that withstands the temperature required for the process wood is often used for cold casting molds stone, sand, and dry mud, for hot casting. The fluid casting material is then poured into the carved depression, where it is left to set and from which, when solid, it is finally removed. 

A unique and considerably more elaborate multiaxial test employs a thick-walled hollow sphere test specimen which may be pressurized internally or externally with a nearly incompressible liquid. Figure 20 illustrates the essential features of the test device as described by Bennet and Anderson (5). The specimen is prepared by casting propellant in a mold fitted with a sand-poly (vinyl alcohol) mandrel inside the sphere which may be removed easily after curing. A constant displacement rate instrument drives the piston to pressurize the chamber and apply large deformations. The piston s total displacement volume is transferred to... 

A piece er must next be prepared with the plan outline of the pattern on the joint face cut out. This is ])laced so as to cover the whole of the sand and the top box placed in position, and this in turn rammed up level and carefully removed, of course, bringing with it the upraised sand coincidii with the hollow portion of the ultimate casting. The tissue pajwr is then removed and the pattern withdrawn from the bottom box. Pourer and risers (eight in number) are drilled as before and smoothed off, the top box replaced, thus finishing the mould. 

The viscosity of caramel allows its employment as an adhesive and binder for instant sand-molds and foundry core for producing difiicultly accessible, hollow cavities in castings. Caramel binds together a sodium chloride, quartz, or metal-powder matrix to a mass that binds to aluminum or aluminum-alloy castings. On casting, such a binder produces only a small volume of combustion gases. The cores are readily removed, either mechanically or by dissolution. ... 

The waste wax or cire -perdue method of making hollow castings is believed to have originated in Egypt about this timef. A nucleus of suitable material such as sand or clay was prepared and coated with wax. The wax envelope was suitably shaped and the whole covered with a layer of fine clay and then with loam. The wax was now melted and allowed to flow away whilst molten metal was poured into the hollow mould thus produced. 

When a casting is to have a hollow section, a core must be incorporated into the mould. Cores can be made from metal or more commonly from sand, made separately in a core box, and inserted into the mould after the pattern is removed and before the mould is closed. They are located and supported in the mould in a seating formed by the core prints on the pattern. The core must be strong enough to support itself and withstand the flow of molten metal, and in some cases it may be necessary to reinforce it with wires to give added strength. The more complex cores are produced from CO sand. 

Urea-formaldehyde resin is also commonly used to bind the sand together to make the cores that are placed in molds for casting hollow metal shapes. The amino resin is mixed with the moist sand and formed into the desired shape. After drying and curing, the core is assembled into the mold. The sand core is stable enough to hold the molten metal to the desired shape until the metal solidifies. The continued heating of the sand core breaks down the resin so that the loose sand may be poured out by the time that the molding has cooled down and solidified to the desired shape. 

For casting metals, molds are used. There are permanent molds (metal, graphite and ceramic) or sand molds. Sand cores for hollow castings are used for both mold types. Sand molds and cores need core-binders. Usually, 1-2 parts are added to 100 parts of sand. There is a large variety of inorganic and organic binders. Some foundry resins are based on RR ... 

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