Aluminum Sand Casting or Sand Casting Aluminum

Aluminum sand casting is the process of forming aluminum into a mold pattern formed in sand. Almost 60 percent of all metals are produced using the sand casting process. Most aluminum castings are usually made in sand molds.

You only need two things to create an aluminum sand casting. One is, the sand has a cavity shaped in the object you want to replicate. The second is, there should be an opening for melted aluminum to go through the cavity.

History of Aluminum Sand Casting

Aluminum Sand casting is one of the oldest casting processes way back 2000 years ago. It was first recorded in 1540 by Vannoccio Biringuccio. Sand casting aluminum goes back to when aluminum was discovered. Wagner Ware is a cast-iron cookware manufacturer. They converted several of their sand-cast abilities to aluminum starting in 1894.

Four main components for making a sand casting aluminum mold

Base sand

Base sand is the type used to make the mold or core without any binder.

Types of base sands

  • Silica sand – It is found on a beach and is also the most widely used sand in casting aluminum. It is created by crushing sandstone or taken from naturally occurring environments like beaches or river beds. The melting point of pure silica is 3,200 degrees Fahrenheit or 1,760 degrees Celsius. Impurities make the sand in aluminum sand casting have a lower melting point.
  • Olivine Sand. This sand is a mixture of magnesium and iron orthosilicates.  It is a mineral called “dunite.” It is free from silica and can use with other basic metals, such as manganese steel. It has high thermal conductivity and fusion point but has a low thermal expansion rate. It is popular in Europe because it is safer than using silica.
  • Chromite sand. It is a solid mixture solution of magnesium and aluminium called spinels. It has a high fusion point of about 3,360 degrees Fahrenheit or 1,850 degrees Celsius. It has an astounding thermal conductivity but it is very costly.
  • Zircon sand – It is a compound mixture of zirconium oxide and silica. It has the highest fusion point for all base sands with 4,710 degrees Fahrenheit or 2,600 degrees Celsius. Zircon sand has a low thermal expansion rate. But high thermal conductivity making it efficient for casing allow. This is expensive and not always available.
  • Chamotte sand – It’s created by heating fire clay to high temperatures in the absence of oxygen. It is very coarse and gives a very poor finish.

Binder

Binders are additives that help in holding together the sand particles. It is like glue for the mold.

Types of Binders

  • Clay and water – There are two types of clay used. They are bentonite and kaolinite.
  • Oil – Linseed oil and vegetable oils are used before. They are now discontinued due to expensiveness.
  • Resin –  They could be synthetic or natural gums found on trees or plants. Urea-formaldehyde and phenol formaldehyde are typical resins used in sand casting aluminum.
  • Sodium silicate – It is a sturdy binder partnered with silica molding sand. It can be used at room temperature and can dry fast.

Additives

These are chemicals added to the molding ingredients. It enhances the parts’ aesthetic finish, structural strength, refractoriness, and energy absorption properties. The coal powder and fuel oil added to the molding material prevent liquid metal from adhering to sand particles.

Parting compound

It is a mixture of powders like talc, dry silica or graphite, and mineral oil and water-based silicon solution. It helps in getting the replicated parts out of the mold pattern.

Types of Aluminum Sand Casting Processes

Green Sand

This method is made from wet sands that contain water and an organic bonding compound or clay. It is called green not because it is colored “green” but as a term saying that the mold is not yet “set.”

It is a mixture of the following:

  • Silica sand
  • Clay
  • Water
  • Inert sludge
  • Hard coal or sea coal

The use of sand has a lot to do with the temperature at which it is pour. When pouring molten copper or iron, the clay is usually inactivated by heat. Montmorillonite is then converted to illite. Illite is a non-expanding clay. There are many ways for proportioning the clay used with other materials. They all depend on the right balance of aesthetic finish, moldability, and aluminum’s ability to degas. For it to achieve the replicated parts. Greensand for aluminum sand casting uses olivine sand. It is a mixture of the minerals found by crushing dunite rock. Forming forsterite and fayalite. Sea coal is always present in all sand casting processes.  This is due to its partial combustion property when combined with molten metal.  

The least desirable of the sands used is silica. Metamorphic grains of silica sand has a tendency to explode. Forming sub-micron-sized particles that enter foundries work areas. It can lead to pulmonary fibrosis in workers. Foundries exert a lot of effort on eliminating these silica particles. They currently use sophisticated respiratory-protective equipment.

Air-set method

Air-set method is a process that uses dry sand bonded with clay and other materials using a fast curing adhesive. There are two types of molding sand used, bank sand and synthetic. Synthetic is preferred because of its consistent composition.

With this method, the sand mixture is stuff around a pattern forming a mold cavity. A temporary plug is also formed within that cavity for it to have a channel for the liquefied metal to be pour. Air-set molds are forged with the help of a casting flask with a top and bottom part. The sand mixture is press down as it is added into the pattern. It is then shaken and patted to make the sand compact and fill any void within the mold.

The plug is removed to let the liquefied metal pour into the mold cavity. The casting is removed from the sand mold once it is cool. Typically the mold is destroyed in the removal process.

Why JC Casting is the right choice for your Aluminum Sand Castings needs

JC Casting implements a very thorough and strict quality inspection process. We are ISO 9001:2008 certified and have the experience of helping you with all your casting needs. JC Casting has various alloy materials you may need. From titanium, steel, alloy, iron, as well as aluminum casting. Our goal is 100% on-time delivery. We guarantee that all services purchased are of high-quality materials. But at an affordable price.

The information given here will give you a better understanding of sand casting aluminum. To know more about aluminum sand casting here at JC Casting. Please visit our website at https://www.investmentcastingpci.com. Send us an email at [email protected]

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