Casting of aluminum in sand molds most commonly used in the manufacture of metal castings. This technology uses disposable sand molds for casting of complex parts from virtually any metal alloys, including, casting aluminum alloys. Because the, to remove the finished casting, sand mold has to destroy, the sand casting usually has low productivity.
aluminum casting process in sand molds
The technology of aluminum sand casting includes the use of:
- melting (holding) furnace,
- foundry models and
- sand mold.
A casting aluminum alloy, first melted in an oven and then through the ladle, often, manual, is poured into the cavity of the sand mold. This cavity in a mold formed using the mold casting model, often, wood. Sand mold after complete solidification of the metal separated along a parting plane and extracting the solidified casting. Below these technological stages of casting in sand molds, including, aluminum casting, discussed in more detail.
Sand casting is used for producing various metal components with complex geometries. These casting can vary considerably in size and weight - from hundreds grams to several tons. It is sand casting that produces many aluminum cast parts and components for cars: blocks and cylinder heads, gearbox, housing units chassis and much more.
The technological process of casting aluminum sand casting consists of six basic steps.
Production of casting sand mold
The first step in the casting process in sand casting is to create a mold for casting. Sand molds are single - disposable, so they made anew for each casting. Sand mold formed by compacting the sand in each of the two mold halves. Sand stuffed around the model, which is the imprint of the outer shape of the casting. When the model is withdrawn, It is in the form of a cavity, and which will form the casting.
To generate any internal cavities of the casting, which can not be generated model, individual components used form, so called, rods. These rods are also made of sand before the molding mold.
The sand casting mold manufacturing process includes:
- installation of the model;
- compaction of sand;
- model removal.
The duration of making a sand mold depends on:
- the size of the cast part;
- number of rods;
- type sand mold.
If the type of the sand mold requires heating or baking, the duration of its production is greatly increased. Moreover, on the surface of the mold lubricant is often applied in order, to make it easier to remove the finished casting. Application of lubrication also facilitates the flow of metal, and increases the quality of the casting surface. Lubricant is selected according to the type of sand used, and the melt temperature.
Build sand mold
When the casting mold is made, it is prepared for pouring the molten metal. The surface of the mold is first smeared, to ensure free removal of the casting. Then set the cores, an upper mold mounted on the lower and securely connect them with each other. It is very important, so that the two halves of the mold remain securely closed, to prevent any flow of metal.
Fill the mold
the molten metal, for example, casting the molten aluminum alloy, is brought in the melting (holding) furnace to the specified pouring temperature. After that, as the mold is closed, the molten metal can be fed into the ladle and poured into the mold. This filling can be made, manually, or by mechanisms and automation.
The amount of metal in the ladle should be sufficient to completely fill all cavities and channels of the mold.
Cooling the mold
Molten aluminum begins to solidify, as soon as it enters the mold. When all of the mold cavity and the molten aluminum is filled completely solidifies, forming a predetermined shape casting. Mold does not open, until the set time has elapsed it cool. Necessary cooling duration is evaluated by the casting wall thickness and the pouring temperature of the metal.
Most of the possible defects, which can be in aluminum casting, result from solidification process. If molten aluminum is cooled too quickly, on the casting may occur shrinkage, a crack or portions, insufficiently filled with metal.
Knockout of the casting mold
After that, as a predetermined duration has elapsed solidification, sand mold just destroy and remove them from casting. This stage is called a knockout, because it is usually made on special vibration or inertial knock-out machines, which shake the sand and casting out of the flask. Typically fresh castings are adhered on the surface of the sand or oxides, therefore, they are often subjected to shot peening, to remove any leftover sand, particularly the inner surfaces, and reduce the surface roughness.
When the metal is cooled in the mold material of the secondary passages gating system together with the solidified casting. This excess material is removed from the casting by hand using various cutting tools, for example, teeth, as well as the use of special machines obrubochnyh. The complexity of this operation depends on the size and complexity of the casting. metal waste, which are formed by chipping operation, sent to the smelter following parties castings.
A source: custompartnet.com