A Guide to Closed Die Forging

Closed die forging, also known as impression die forging, uses two or more dies that contain a precut
profile of the desired product. Heated metal, such as steel, bronze, titanium, or aluminum, is poured
into the bottom die. As the dies come together, pressure and impact forces form the metal to fit the
shape.

Capabilities of Closed Die Forging

A major advantage of closed die forging is its preciseness. Parts weighing anywhere from several
ounces to 60,000 pounds can be produced in a virtually limitless variety of 3-D shapes. Closed die
forging is equally effective for simple spheres and blocks, for extremely intricate components with high
vertical projections and thin webs, and for parts that include detailed design elements such as bent or
curved flanges and protrusions.

Metals and Alloys

Virtually all metals and alloys that are used in engineering can be used in closed die forging. Some
materials that are particularly sensitive to temperature or strain rate, such as refractory alloys and
nickel-based super-alloys, may require special equipment for closed die forging.

Closed Die Forging Process Operations

The simplest version of closed die forging brings two dies together to cause plastic deformation in the
heated metal until its sides touch the side walls of the dies. A small amount of the metal then starts to
flow outside the die, forming flash. The rapidly cooling flash adds deformation resistance, building up
pressure inside the dies to boost material flow into all areas of the dies.

Closed Die Upsetting

Closed die forging can be performed on horizontal forging machines known as upsetters. In this case,
“grip dies” consist of one stationary die and one moving die that contain the desired impression and
can be closed to hold the material in position for forging. A ram-operated “heading tool” acts as a
hammer or press, forcing metal into all sections of the grip dies.

Closed die forging can produce products with tighter tolerances and higher precision than other
methods such as open die forging. The finished products also have better strength and tightness, as
well as an improved surface finish. Like anything else, though, closed die forging is not always the
right choice. It can be expensive for small runs due to the need to create customized profiles for each
piece. In addition, fatigue resistance is not as high for closed die forged items as for open die forged
items.

At Atlas Bronze, we carefully select the forging or casting process that is right for each item. Using the
best process lets us ultimately produce the best results.

Ready to Start?

Atlas Bronze is a leading U.S. distributor of bronze, copper, brass, iron, and more. Contact us today at
1-800-478-0887 to place an order or learn about our custom products.

Understanding Hot Extrusion

Extrusion creates objects by pushing raw materials through a die to create complex cross-sections in
finished products, such as bars, tubes, or strips, and to improve the strength of metal construction or
manufacturing materials. The finished materials could be hollow or solid. It is one of the most common
methods of metal processing, though it can also be used with other types of raw materials.

How Hot Extrusion Works

Hot extrusion happens when the process takes place at a higher temperature than the metal or alloy’s
recrystallization temperature. This makes the process of pushing the material through a die easier.
How hot the metals must be depends on the specific metal. However, temperatures typically range
from 650°F for magnesium to 2,400°F for some types of steel. The exact temperature varies based on
many factors, including the final application.

Benefits of Hot Extrusion

Hot extrusion creates products with homogeneous properties that are of very high quality. This improves
the appearance and functionality of the finished product, as well as increasing the strength of the metals
(in most cases). The process of hot extrusion can save energy compared to cold extrusion processes,
where more force must be exerted onto the materials. It can also reduce material waste, which can
mean material savings, especially from large projects.

While hot extrusion may not be economically advantageous for small or very large batches, it might be
the most cost-effective option for medium to large volume projects. However, this largely depends on the
materials being rolled. Some types of steel produced in quantities over 50,000 pounds are more cost
effective using a hot extrusion process.

Disadvantages of Hot Extrusion

Hot extrusion is a more expensive process than other methods because of the upfront cost of the
required machinery as well as the cost of maintaining it. Some manufacturers may not offer hot extrusion
as a result. You may be required to pay more for parts created using hot extrusion rather than other
processes.

Additionally, the pressure range required for the process requires the use of lubrication. The heating
process could weaken the materials. Cold extrusion, as opposed to hot extrusion, may provide a better
surface finish. Under high heat, some metals can become oxidized, which could change the appearance
of the metal and increase friction, again requiring the use of lubrication. Which process is best will
depend on the raw materials and the final intended use of the products.

Ready to Get Started?

Atlas Bronze sells a range of engineered products for every industry, including made to order plates,
castings, and forgings. Check out our online store at www.atlasbronze.com to see what existing
products we sell or contact us for a quote on your custom project. Our expertise and experience can
help to ensure that you have access to the highest quality metal products for your project.

A Guide to Centrifugal Casting

Centrifugal casting, also known as rotocasting, is a casting process that can create thin-walled cylinders
of metal that are of high quality. It is often used to make stock materials in applications where the
standardization and quality are important. Here are some things to know about centrifugal casting.

What is Centrifugal Casting?

Centrifugal casting is the process of casting metals such as iron, steel, and aluminum alloys into a
rotating mold. In the normal casting process, these metals are poured into a mold that forms them into a
precise shape as they cool. This works well for most applications where the finished product has a solid
metal core. Centrifugal casting works in the opposite way, creating shapes that are hollow inside. This is
done by pouring liquid metal into a mold that is rotating at a high speed. Instead of filling the center of
the mold, the metal moves to the outer walls.

Types of Centrifugal Casting

There are three basic types of centrifugal casting: horizontal, vertical, and vacuum. Horizontal centrifugal
castings rotate on a horizontal axis to create long cylindrical parts using fast speeds. Vertical centrifugal
casting uses dies that rotates on a vertical axis and may use sand or ceramic molds to achieve outer
diameter shaping. In the vacuum centrifugal casting process, the process takes place in a vacuum to
limit the metal’s exposure to oxygen, which could react with some metals.

How Does Centrifugal Casting Work?

The process starts when a molten metal is poured into a mold as it spins around. The centrifugal force
distributes the metal at an intense pressure greater than that of gravity. As the die fills with the molten
metal, the densest metal is forced to the wall of the die while lighter metals stay closer to the core. The
result is a formed metal object that is hollow and generally has a rounded outer shape.

Benefits of Centrifugal Casting

Centrifugal casting creates a high-quality finished product that is known for its controlled metallurgy and
crystal structure. The process can create castings that have rotational symmetry. In traditional casting
applications, it is difficult to create thin-walled cylinders.

Applications for Centrifugal Casting

Due to the high material soundness that results from centrifugal casting, it is an excellent choice for
creating materials that need a consistent and reliable level of quality. Many components used in
manufacturing, industrial, military, and aeronautics applications benefit from centrifugal casting. It can
also be used to make items that will be placed under high pressure such as underground pipes, tubes,
and cylindrical objects with highly dense outer shells.

Atlas Bronze is a leading distributor of bronze, copper, brass, iron, and sintered products in the U.S. If you’re in the market for metal engineered products, including high quality centrifugal castings, contact Atlas Bronze by contacting us or shopping in our online store. We’re happy to answer any questions you may have about our castings and the various applications in which they can be used.

A Guide to Continuous Casting

Also known as strand casting, continuous casting is the process of solidifying molten metal into a
semi-finished billet or slab for rolling in a finishing mill. Before the 1950s, casting required the liquid
metal to be poured into individual molds to create ingots. Continuous casting speeds up and smooths
out the process, reducing the cost of cast metal while raising its quality and standardizing its
production.

Advantages of Continuous Casting

No single casting method is the right choice for all applications. Still, for many applications, continuous
casting has a number of advantages over other casting methods.

Continuous Casting vs Ingot Casting: Ingot casting loses approximately 5 percent of all blocks to
waste due to cracks and deformations that arise during the casting process. Continuous casting
creates solid, uncracked bars and slabs every time.

Continuous Casting vs. Sand Casting: Most metal castings are created through sand casting, and
it remains an excellent option for many projects. However, sand casting carries several risks that are
virtually eliminated by continuous casting, such as shifting molds, non-uniform cooling, and the
possibility of cracks in the mold.

Continuous Casting vs. Extrusion Molding: Extrusion molding is an inexpensive way to churn out
simple parts. However, it uses force to ram one metal into another, and as such, it cannot be used to
create complex shapes. In addition, extrusion raises the risk of cracking in the finished product.

Steps to Continuous Casting

Molten metal is ladled into a casting machine where it is molded, cooled, and stretched into the desired
shape and size. Different machines have their own pros and cons, but the basic steps remain the
same:

1. Tundish: Liquid alloy is ladled into the tundish, which serves as a reservoir and directs the flow of
the metal into the mold.

2. Mold: The tundish directs the liquid alloy into a water-cooled mold, where it partially solidifies and
receives its basic shape. The semi-cooled metal is known as a grid.

3. Strand Guide: When the grid is semi-solid, it is sent through the strand guide, which stretches the
metal to its proper thickness while continuing to cool it.

4. Straightener: When the grid is fully hardened, it is sent through a straightener to receive its final
dimensions.

5. Rolling: The finished material is wound into a roll and stored.

Bending and Straightening Considerations

Throughout the casting process, the metal is bent and straightened over and over again to achieve a
precise shape and size. However, this can cause excess strain that weakens the finished metal.
Therefore, it is critical to find just the right arc to bend the grids depending on the mechanical properties
of the specific metal that is selected. It is also important to choose a multi-point straightening process
that can minimize the effects of the strains caused by bending.

Ready to Start?

Atlas Bronze is a leading U.S. distributor of bronze, copper, brass, iron, and more. Contact us today at 1-800-478-0887 to place an order or learn about our custom products.

Understanding The Difference Between Cast Metal and Wrought Metal

Many people use the terms “cast metal” and “wrought metal” interchangeably, but the two actually
refer to very different processes. Cast metal has been melted, molded, and cooled. Wrought metal has
been heated and then worked with tools. Here is what you should know.

Cast Metal

Any metal that can be wrought can also be cast. However, both cast metal and wrought metal are
generally alloys rather than pure metals, and their compositions are different. This means that when
compared to wrought metal, cast metal is harder, more brittle, and less malleable.

Cast metal has a relatively low tensile strength, which means that it is likely to break rather than bend,
but it has a high compression strength, making it useful for constructions and other applications where
it needs to hold significant weight. Cast iron, for example, was a common building material from the
18th century until it was replaced by steel in the early 20th century.

Wrought Metal

Wrought metal is heated and then worked with a hammer and other tools while hot before being
cooled. It is softer and more ductile than cast metal. Since it is extremely malleable, wrought metal
can be reheated and reworked over and over again. This reworking actually strengthens wrought metal
rather than damaging it.

Wrought metal has a very high tensile strength, making it ideal for applications such as horizontal
construction beams that must deform and reform regularly. It is extremely resistant to fatigue, and it is
unlikely to break unless it is distorted from intense heat such as a fire or is severely overloaded.
Today, wrought metal is mostly used as a decorative material.

Corrosion

Some metals form a protective oxidative coating over time, while others are susceptible to corrosion.
Both cast iron and wrought iron are particularly at risk for corrosion, especially in areas of high
humidity and frequent precipitation. Consequently, both need to be protected in some way. Paint and
powder coatings are two of the most common ways to protect bare metal.

A powder coating consists of a polymer resin mixed with a variety of additives such as leveling agents,
curatives, flow modifiers, and perhaps pigments. The ingredients are melted, mixed, cooled, and
ground into a power that resembles baking flour. The powder is then loaded into a special electrostatic
spray gun that gives it a negative charge and applies it evenly to the metal item. The metal then enters
a curing oven where it is baked to create a chemical reaction that ensures even, long-term adhesion.
Powder coatings are highly durable and are not prone to flaking, fading, cracking, or chipping.

Both cast metal and wrought metal can be highly decorative as well as extremely functional. Yet the
two are not interchangeable. It is important to understand the differences in order to purchase the
product that best meets your needs and desires.

Ready to Start?

Atlas Bronze is a leading U.S. distributor of bronze, copper, brass, iron, and more. Contact us today at 1-800-478-0887 to place an order or learn about our custom products.

A Guide to Sand Casting

Sand casting is the process of casting metal via non-reusable sand molds. It is commonly used for
metal components ranging in size from just a few ounces to many tons. Sand casting can create
tremendously detailed castings, and it works for virtually any metal alloy. In fact, it is one of the few
processes that can be used for metals with very high melting temperatures such as nickel, titanium,
and steel. It is also relatively low-cost. Here is what you should know.

Molding Sand

Molding sand is inexpensive and easy to recycle, and it can withstand extremely high heat. While pure
sand breaks apart easily, molding sand contains bonding materials that allow it to hold its shape until
the metal inside has cooled and hardened.

Traditional sand casting used green sand, a mixture of sand, bentonite clay, pulverized coal, and water.
Today, modern chemically bonded mixes are becoming more popular. The most commonly used type
of sand, however, is still silica (SiO2).

Whether green sand or a modern chemical blend is used, molding sand must have certain properties
to be used for sand casting. These include:

Strength: The mold must be able to hold its geometric shape under mechanical stress.

Permeability: The mold must allow gases and steam to escape during casting.

Moisture: Too little moisture can make the mold brittle, while too much moisture can trap steam
bubbles inside the casting.

Flowability: Detailed castings need sand with a high flowability, or the capacity to even fill small
spaces in the pattern.

Grain size: The optimal size of each individual sand grain will vary according to the casting.

Grain shape: Molding sand comes in three different shapes. Rounded grains have high flowability
and permeability but poor bonding strength. Angular grains have high bonding strength but poor
flowability and permeability. For most applications, middle of the road sub-angular grains are ideal.

Collapsibility: A high level of collapsibility allows the sand mold to collapse under force. This lets the
metal casting shrink freely during hardening, reducing the risk of tearing or cracking.

Refractory strength: This is the molding sand’s ability to withstand extremely high heat.

Reusability: This refers to the molding sand’s ability to be recycled for new sand castings.

Sand Casting Mold

Sand casting molds have numerous parts that work together to develop the finished casting:

Pattern: The pattern is a full sized model of the finished piece that is used to create an impression in
the mold.

Core: A core is a separate piece of sand inserted into the mold to shape the interior of the pieces,
including such pieces as holes or passages. A core print and small metal pieces known as chaplets
may be added to support one or more cores.

Riser: A riser is a void in the mold that holds excess metal. It prevents voids from forming in the
casting by feeding liquid metal to the mold cavity as the casting hardens and shrinks.

Flask: The flask is a box that contains the entire sand mold. It is typically in two parts, with the
upper half known as the cope and the lower half known as the drag. The parting line separates the
two halves.

How Sand Castings Are Made

There are four basic steps to sand casting:

Mold assembly: The drag is partially filled with sand, and the pattern, core print, and cores are
inserted near the parting line. Then the cope is attached, and additional sand is poured until all pieces
are covered. The sand is compacted, and excess sand is removed with a strike off bar. The cope is
then removed so that the pattern can be extracted.

Metal pouring: The mold is prepared, a complex process that involves lubrication, positioning of the
cores, clamping, and possibly other steps to ensure that the mold is secure. Molten metal is then
poured into the mold via a pouring cup and gating system.

Cooling: During the cooling process, built up gases and displaced air escape through a series of
vents. The metal casting naturally shrinks as it hardens.

Removal: When the casting is completely cool, the sand mold is broken for removal in a manual or
automated process known as shakeout. The sand is then conditioned and recycled into a new mold.

Naturally, there are numerous different sand casting methods. Each is ideally suited for specific metal
items. At Atlas Bronze, we can create custom castings using the methods that, in our professional
opinion, are the best for your particular needs.

Ready to Start?

Atlas Bronze is a leading U.S. distributor of bronze, copper, brass, iron, and more. Contact us today at 1-800-478-0887 to place an order or learn about our custom products.