of Casting, Manufacturing Process in Current Foundry
Mankind’s industrial rise would not have been possible without
the evolution of metal working. The earliest evidence of copper
working indicated our ability to manipulate metals into desired
shapes. As civilization grew in trade and expansion, tools and
techniques were required to form metal objects. Metalworkers
grew in skill and technique; mastering the production in
adornments, weaponry, artifacts, ships, and machinery. As
centuries passed, various techniques in metal working were
created to meet the demands of the industrial age. These
processes eventually came together under one roof.
One particular technique that has been used from ancient to
modern times is metal casting. Skilled metalworkers pour molten
metal into a mold. The inside of this mold or “cavity”, contains
the metal which will solidify upon cooling. To obtain the
desired shape of the casting, the inside of the mold contains a
“pattern”. As the metal cools, it solidifies into the shape of
the pattern. The casting is then ejected or broken from the
Over time, various combinations of metals were used to meet a
casting’s desired metallurgical characteristics. Alloys were
created by mixing various metal and non-metal content to enhance
strength, toughness, durability, and surface hardness. Today’s
industrial castings are typically iron castings or steel
castings with varying ratios of additional elements. With the
advent of carbon steel castings, alloys containing different
ratios of carbon are used to achieve specific properties. One
example of carbon steel universally used in casting is ASTM A27
In parallel to alloy discoveries, new processes emerged in
castings. Two classes of casting methods came to be: expendable
mold casting (non-reusable molds) and non-expendable mold
casting (reusable molds). Expendable mold casting includes sand
casting, plaster mold casting, shell molding, investment
casting, waste plaster casting, and evaporative-pattern casting.
Non-expendable mold casting employs methods such as permanent
mold casting, die casting, centrifugal casting, and continuous
casting. There are various advantages to each casting process
depending on the object’s dimensional requirements, production
repeatability, and physical properties.
A foundry is a factory that will house any combination of the
casting processes mentioned above. Since ancient history, groups
of metalworkers, metallurgists, engineers, artisans, and
laborers worked together in a location that could accommodate
their services. In 3000 BC the Mesopotamians discovered bronze
by adding a small amount of tin with copper during smelting. The
Egyptians of 1500 BC depicted tomb paintings with pictures of
smelting operations, blast air, and crucibles filled with molten
metal. In Ancient Greek artwork, craftsmen are seen working with
hot furnaces and casting pits. For the modern day foundry, the
same fundamental casting processes exist - but with advances in
technology and production.
What can be found in today’s foundry that creates castings?
Similar to a factory’s production line, the manufacturing chain
is composed of nine primary sections:
1. First, foundries melt metal to extremely hot temperatures.
This requires heating raw metal and/or alloying elements into
molten form so it can be poured into molds. In order to achieve
these temperatures, specialized furnaces are used. Foundries may
house different furnaces based on the type of material or
casting process involved.
2. Some metals discharge quantities of hydrogen during cooling.
Hydrogen bubbles escape to the top of the surface at the moment
of cooling and solidification. This will create porosity on the
object’s surface and lead to mechanical and chemical
deterioration of the object over time. To combat this, a foundry
will employ various types of "degassing" equipment to measure
and regulate the amount of hydrogen present in the object.
3. In order to create a casting from an original design,
foundries require mold and pattern making equipment. Depending
on the casting process involved, a foundry may offer several
types of mold making systems. For example, sand casting requires
specialized resin bonded sand molds. Investment casting requires
the creation of wax patterns and ceramic molds. Die casting
involves machining metals into molds using various alloys
containing zinc, copper, lead, pewter, and more.
4. In foundry operations molten metal is transported, contained,
or poured. Crucibles, robotic arms, and gravity induced pouring
machines are used to move molten metal from one location to
another. Metal workers will also pour molten metal by hand using
5. Once a mold solidifies, equipment is used to eject the final
object from the mold. This requires the use of specialized
cutting torches, saw blades, sledge hammers, or even knockout
machinery to eject the casting from the mold.
6. Foundries also employ equipment used to heat treat metals in
order to alter their physical properties. Using specific
techniques in heating and cooling, a metal’s properties are
manipulated through annealing, case hardening, tempering, and
7. Once the casting is ready, its surface properties still
require treatment. Excess mold media such as sand or metal
particulate need to be removed. In this case, various surface
treatments are used. This can include high powered compressed
air or surface blasting with beads, metals, or other media.
8. Now that the casting is clean, final finishing takes place.
The finishing process involves equipment for grinding, sanding,
machining, painting, and welding to achieve whatever is
requested by the customer.
Foundries are simply factories that provide steel casting
services. Castings are the end product created by foundries. The
tools, techniques, and processes used to make castings were
berthed under the roof of the foundry. To this day, the pillars
of our industry depend on foundries to create castings of all
sizes and for every sector of our society.
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