Grey Iron Castings

About Grey Iron Castings and Grey Castings, Including: Ductile Iron Casting, Gray Iron, Gray Iron Castings, Grey Iron & Iron Castings.

Grey iron is arguably the oldest and most versatile of all metals that are cast by foundries to date. It is also among the most abundant and cheapest of all metal materials. Grey iron castings are a product created from melted grey iron molecules that are poured into a mold, and once cooled, extracted. The properties of a casting depend greatly on foundry practice along with the rate of cooling. Large concentrations of carbon are present in grey irons. This high content allows for ease of casting, melting, and machining. Designs for grey iron castings vary greatly due to its near absence of shrinkage while cooling. The cast product itself is renowned for its durability and strength. Tensile strength for grey iron castings range from nearly 20,000 psi to more than 60,000 psi. Without any heat treatment, hardness values for grey iron products differ from 100 to 300 BHN.

There are a number of things that someone looking to purchase grey castings should consider. First and foremost is foundry quality in procedures and resulting products. Since characteristics of grey iron castings rely greatly on foundry practices, finding the appropriate one will result in a consumer's needs being met or surpassed. Carbon concentration in the casting itself is another important consideration. Common percentages for carbon amounts range from 2.5 to four percent. A carbon addition of about .1 percent in grey castings will result in a tensile strength decrease of around 2700 psi. Different foundries utilize varying casting procedures.

Green sand molding is the most common production type for castings. It is generally used to produce small or medium sized cast products, but can produce castings up to 1000 pounds. The process of shell molding is used for larger applications. With shell molding, it is possible to cool the mold that contains the heated metal. This process allows for a cleaner final product than any other means of production. Centrifugal casting is the third and final type of procedure. It's typically used for pipe and large cylinder production and consists of water-cooled molds. Choosing a reputable foundry, that utilizes the correct process for a casting, will lead to both consumer and producer satisfaction.

Many shops not only are capable of grey iron castings, but specialize in a wide range of non-ferrous metal die-casting. Grey castings are used extensively in the automotive, appliance, agricultural and machinery industries. Examples of parts created using grey iron are pump and turbine housings as well as bases for dynamometers and compressors. Most manufacturers are capable of both low and high production outputs as well as short order runs. Prototypes are standard to ensure accuracy and customer satisfaction. Finishing services such as machining, painting and galvanizing are provided as well by many of the manufacturers of grey iron castings.

Types of Grey Iron Castings

• Alloy castings are a cast product that is composed of multiple metals. Almost all castings are alloys because it is difficult to mold a solitary metallic element.
  
• Ductile iron castings are very thin molded products cast out of iron or an iron alloy. A ductile casting has the ability to be stretched, hammered or drawn without breaking.
  
• Gray iron, or cast iron, is an inexpensive and commonly used metal material.
  
• Gray iron castings are created by molding molten gray iron materials.
  
• Grey iron casting services are performed by foundries. They normally consist of one or more metals going through liquefaction, then pouring the molten material into a mold. After proper cooling, the mold is re-opened, and the casting is ejected.
  
• Iron castings are any of variously designed products that are comprised of primarily iron. Iron is a very strong and plentiful material, making it a prime candidate for casting foundries.
  
• Malleable iron castings are cast products that consist of mostly iron. Unlike a normal iron casting, one that is malleable has the ability to be shaped and bent without fracture.

Grey Iron Castings Terms

As-Cast Condition - Casting without later heat treatment.

Brinell Hardness Number (BHN) - A value given to a grey iron casting after undergoing a Brinell hardness test. Higher numbers indicate a harder material.

Brinell Hardness Test - A method used to measure how hard a material is. Typically for grey iron castings, a 3000kg metal ball is impressed on the surface of a flat grey iron piece; after removing the ball, the indentation in the metal is recorded and measured, determining a hardness value.

Chaplet - A small metal insert or spacer used in the molding process used to give support to the core.

Cope - The top half of a piece which has been forged or caste horizontally.

Deflection - The amount of bending or deformation that an iron casting endures due to an external load. Deflection is an important consideration for companies that plan on supporting a load with a grey iron casting.

Drag - The bottom half of a mold created horizontally.

Ductility - The ability of a grey iron casting to deform without being fractured. Iron castings have a considerable amount of ductility.

Ferrous - Any material that is made of or contains iron.

Foundry - A place where molten metal is poured into a mold, creating a metal casting.

Galling - A condition that results from excessive friction between metal surfaces. It creates surface deformation(s) and can result in temporary adhesion. Grey iron is renowned for its resistance to galling.

Hypereutectic Iron - Refers to an iron metal that is composed of more than 4.3 percent carbon.

Hypoeutectic Iron - Any iron alloy that is made up of 4.3 percent carbon or less.

Malleable - A property describing metals that can be pressed, hammered, formed, rolled, bent, etc.

Modulus of Elasticity - Measures the ration of stress to strain for an elastic material. Modulus of elasticity also describes stiffness of a material.

Permeability - The mold-metal property which allows passage of mold/core gasses during the pouring of molten metal.

Pilot Casting - Also known a sample casting in which a pattern produced by a production die is used to check the accuracy of the quality and dimensions of a potential order run casting.

Porosity - Holes formed in casting due to trapped gasses or chemical reactions between the molten metal and internal substances or objects such as chaplets.

Pounds per Square Inch (PSI) - The pressure a material applies on the walls of a closed enclosure. Atmospheric pressure at sea level is 14.7 psi.

Shrinkage - The decrease in the size of a material. Grey iron goes through little if any shrinkage when going through solidification.

Tensile Strength - The amount of stretching and bending that a material can undergo before breaking or tearing. The tensile strength for grey iron castings range from about 20,000 psi to 60,000 psi.