Physical and chemical properties of aluminum.
Aluminum is one of the most interesting chemical elements since it has been introduced unexpectedly and quickly into our lives, through the automotive, electrical, construction, Automotive Die and aeronautical industries, in many cases replacing iron and steel.
It is the most abundant metallic element in the earth’s crust. It is ductile and malleable, it is a light metal, less heavy than iron.
Aluminum is used in a wide variety of products, including cans, foil, cookware, window frames, beer kegs, and aircraft parts. This is due to its particular properties. Al aluminum has low density, is non-toxic, has high thermal conductivity, and has excellent corrosion resistance. It is non-magnetic and does not produce sparks. It is the second most malleable metal and the sixth most ductile.
It is often used in alloys because aluminum itself is not particularly strong. Alloys with copper, manganese, magnesium, and silicon are light in weight but relatively strong. These alloys are common in the construction of aircraft and other means of transportation.
Pure aluminum is highly reactive in the presence of oxygen. When it oxidizes, aluminum oxide is produced, and it is deposited on the entire outside of the metal, this is a microscopic layer that is resistant to corrosive action. Aluminum oxide is transparent, unlike iron oxide, which is reddish or brown, so it seems that aluminum never rusts, although in reality it can be said that aluminum is always rusty.
This microscopic layer of aluminum oxide is highly resistant to corrosion.
This makes the aluminum under the clear oxide layer less affected by the elements in the environment.
Unlike iron, in which oxidation is slow and takes years or decades, the oxidation process in aluminum is very fast, and occurs when aluminum comes into contact with oxygen in the air, completing the layer of transparent rust in a very short time.
Sand Casting VS Die Casting
The process of producing useful parts or objects with molten metal is known as the casting process.
In Sand Mold Casting , patterns are used to create the molds, Automotive Die the preparation and bonding of these sand molds is a very important step.
Two main methods are used for the bonding of sand molds:
• “Green sand” consists of mixtures of sand and clay.
• “Dry sand” is made up of thermally or chemically cured sand and synthetic binders.
Sand mold casting consists of pouring molten metal into the mold in the shape of the part or object to be manufactured and waiting for it to harden as it cools. Among the most common foundry metals are cast iron, steel, aluminum alloys and brass.
Sand mold casting is based on the principle of gravity, that is, the only source of energy that forces the metal to fill the mold cavity is the force of gravity.Automotive Die This type of casting is used for pieces in which the quality of finish and dimensional is not decisive.
Disadvantages are poor dimensional accuracy, poor surface finish, and low strength as a result of slow cooling.
Gravity cast parts will not have as high a dimensional accuracy as die cast.
In Die Casting, the liquid metal is forced into the cavity between the dies by injecting it at high pressure into a die by a special die-casting machine, with a clamping force of 300 tons.
The acting pressure is maintained until the metal has completely solidified.
The pieces obtained with this procedure are of high quality in terms of their finish, their dimensions and have great precision.
This procedure is one of the most used for the production of large quantities of castings.
The mold called matrix, is the most delicate element of pressure casting, it must be made of steel with great accuracy and cleanliness, for which precision tools and machines must be used.
Once the matrix is finished, it is subjected to a heat treatment, which increases its hardness and resistance to attack by liquid metal.
In die casting, the physical conditions in the solidification of the metal can be controlled. While the solidification of the metal in a sand mold is carried out under the action of its own weight, leaving pores.
CHARACTERISTICS OF THE PRESSURE CASTING (DIE CASTING)
- – GREAT ACCURACY OF MEASUREMENTS.
- – CLEAN AND SMOOTH SURFACES.
- – CASTING OF PARTS WITH HOLES WITH HIGH PRECISION.
- – SPEED OF PRODUCTION.
The pieces cast by the pressure injection method are characterized by their cleanliness, measurement accuracy, dimensional stability, good resistance properties, and have better mechanical properties than those cast in sand molds.