View A Video on Grey Iron Castings - A Quick Introduction
Grey iron castings are alloyed iron components manufactured by melting
and molding molten metal at specific rates and temperatures so as to
create parts and components of variable grades and qualities as needed
for industrial applications. Also spelled gray iron, these castings have
been used throughout history due to the abundance and low cost of iron.
A type of cast iron, the name of grey iron is derived not only from the basic elemental composition of the material, but also from the coloring of fractured surfaces of the metal. This method is commonly used to distinguish between iron alloys though the molecular structure is also very different. Even within the category of grey casting there are several different types, such as ductile castings and spheroidal graphite cast iron, based on molecular composition and internal structure. Even minor differences lead to considerable variation of the many desirable features of grey iron such as low melting point, resistance to deformation and wear, energy dissipation and thermal conductivity. As casting and machining can also alter these qualities, specific iron castings must be carefully compared to their intended use to ensure structural competence. Because so many variations exist, iron foundries often offer several different metallurgical and core processes to produce plain gray iron castings as well as ductile iron castings. One of the most popular operations is green sand casting, though die casting is also extremely popular within the industry. The selected casting method depends largely upon the desired size and characteristics needed for the finished part. Foundry professionals may provide additional insight into the most appropriate use of grey iron castings.
Making up 5% of the Earth's crust and 35% of its total mass, iron is the most copious element on the planet. Rarely found in pure form, however, iron oxides or iron ores must be mined and processed to produce grey iron. Metalworkers achieve this through the use of a special type of blast furnace known as a cupola or an electric induction furnace. Though several standardized grading systems are available, the general composition of grey cast iron is 95% iron by weight with an additional 2.1 to 4% being carbon and 1 to 3% silicon. Manganese and other impurities are also commonly found in or added to molten iron as needed for the diminishing or enhancement of specific properties. Sulfur, for example, is commonly introduced to the molten metal in order to increase hardness which is otherwise low in most cast iron components. Specific to grey cast iron is a high amount of silicone which is responsible for the production of graphite when the alloyed materials are heated. The deflection of this graphitic microstructure is what gives the metal its grey appearance. Though most often in flake form, ductile cast iron production slows down the growth of graphite and allows the carbon to separate as spheroidal graphite particles instead. Both the timing and temperature play important roles in the structural disposition of grey iron castings.
With desirable stock material readied, iron foundries use several different processes to produce grey iron castings. Virtually every technique requires the liquification of the grey iron which is then poured into a mold and cooled at precise rates before the completed part is ejected. Die casting employs reusable dies which contain an impression of the finished product. This method is popular when continuous cycle or fast production is needed. Centrifugal casting is used for cylindrical parts and components and works by rotating the mold at high speeds as the molten metal is introduced. This creates a fine grained outer surface with even dispersion. Sand molding is another commonly used process as it is low cost and easily accomplished. A two part mold cavity is formed using a sandy mixture, the composition of which can be any of four choices which include green sand, skin-dried, dry sand and no bake. The material chosen depends largely upon the accuracy needed and the desired surface finish which is often rough and may require finishing operations. As most mold and casting techniques leave the possibility for burrs and other undesirable artifacts, iron foundries often provide a number of secondary operations in order to provide more finished products. Additionally, processes such as annealing, machining, painting and galvanizing among others may also be had at several metallurgical work shops.
Though often confused with forges, only foundries provide the closed mold operations needed to produce quality grey iron castings for the many industries that employ them. Automotive, agricultural, machinery building, electronics, irrigation, ventilation, architecture, construction and transportation industries all utilize these molded parts in daily operations as they provide both strength and durability. As a building and construction component, grey iron castings provide protection against fires as they are non-flammable and thus preferred over wooden support structures. The graphite content of the parts also provides reliable and efficient energy dissipation making the parts suitable for applications in which the dampening of mechanical vibrations is required or desired such as crankshafts and engine blocks. Additional cast grey iron components commonly used include pipes, cases, dies and even decorative embellishments as the material is easily machined with accuracy and precision.
Grey Iron Casting - Fairfield Castings, LLC
Grey Iron Casting - Fairfield Castings, LLC
Grey Iron Casting - Calmego
Types of Grey Iron 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.
- Cast iron encompasses a large group of ferrous alloys containing between 1 and 3 % silicone and 2 to 4% carbon with a core of about 95% iron by weight. There are two predominant types of cast iron, those being grey iron and white iron.
- Core processes involve the implementation of a block or barrier around which castings are made. The use of a core in this manner allows for the creation of internal cavities and reentrant angles in solid iron castings.
- Ductile castings are molded iron components made with a particular group of cast iron alloys that are designed for improved flexibility as compared to traditional grey iron castings which tend to be brittle.
- 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
- Gray iron castings are created by molding molten gray iron
- Gray iron, or cast iron, is an inexpensive and commonly used metal material.
- Green sand casting uses disposable molds made of special sand based slurries to produce cast iron parts and components for a number of industrial uses. While some variations may actually appear green in color, the term is actually derived from wood working and references the wet state of the slurry during mold making.
- Grey casting is the production of molded products made of any of a particular group of iron alloys with notably high carbon and silicon content.
- Grey iron is a type of metal often used in castings. In the past, grey iron was known as cast iron; however, cast iron is now made out of iron-carbon alloys that have a higher level of ductility.
- 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.
- Iron foundries are facilities which provide all of the services necessary to produce iron castings of various sizes and shapes.
- 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
- Spheroidal graphite cast iron is a group of iron alloys specially formulated to create molded products with heightened elasticity, tensile strength and durability.
Grey Iron Castings Terms
- Casting without later heat treatment.
- A value given to a
grey iron casting
after undergoing a Brinell hardness test. Higher numbers indicate a harder
- 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.
- A small metal insert or spacer used in the molding process
used to give support to the core.
- The top half of a piece which has been forged or caste horizontally.
- 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.
- The bottom half of a mold created horizontally.
- The ability of a grey iron casting to deform without being
fractured. Iron castings have a considerable amount of ductility.
- Any material that is made of or contains iron.
- A place where molten metal is poured into a mold, creating
a metal casting.
- 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.
- Refers to an iron metal that is composed of more
than 4.3 percent carbon.
- Any iron alloy that is made up of 4.3 percent carbon
- A property describing metals that can be pressed, hammered,
formed, rolled, bent, etc.
- Measures the ration of stress to strain for an
elastic material. Modulus of elasticity also describes stiffness of a
- The mold-metal property which allows passage of mold/core
gasses during the pouring of molten metal.
- 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.
- Holes formed in casting
due to trapped gasses or chemical reactions between the molten metal
and internal substances or objects such as chaplets.
pressure a material applies on the walls of a closed
enclosure. Atmospheric pressure at sea level is 14.7 psi.
- The decrease in the size of a material.
Grey iron goes through
little if any shrinkage when going through solidification.
- 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.