Understanding the Hot Rolling Process

In metalworking, rolling is a fabrication process that consists of passing the metal through a pair of
rollers. Flat rolling creates a sheet, while profile rolling creates a bar or a rod. In addition, rolling
processes are temperature-dependent. Hot rolling is performed when the material is above its
recrystallization temperature, while cold rolling is performed below the recrystallization temperature.

Advantages of Hot Rolling

As you might suspect, hot rolling and cold rolling create products with very different characteristics,
meaning that each process has its place. Hot rolling requires less processing than cold rolling,
meaning that hot rolled products are significantly less expensive. In addition, hot rolled metals cool at
room temperature, avoiding the internal stresses of quenching or work-hardening. Hot rolling allows
metals to be easily manipulated into a variety of shapes, and it creates a denser finished product.

It is important to note that dimensional tolerances are not as precise with hot rolling as with cold rolling,
but the material strength is higher. Therefore, it is best suited to applications in which strength matters
more than minute distortions, such as construction projects and railroad tracks.

Hot rolled metals do not have the same smooth surface as cold rolled metals, as scaling is a byproduct
of the cooling process. However, this scaling can be removed through acid-bath pickling, sandblasting,
or grinding, and a new finish can be applied. In addition, descaled steel provides an optimal surface for
coatings such as paint.

How Is Hot Rolling Done?

The first step is to heat a large, rectangular billet of metal to an extremely high temperature based on
the temperature at which the molten metal recrystallizes (for example, more than 1700 degrees F for
steel), and then pre-process it by flattening it into a single large roll. While maintaining the temperature,
the metal is then pushed through a series of rollers at high speeds to create its finished shape and size.
To create sheet metal, the rolled metal is spun into coils before cooling. For bars, plates, or other
profiles, the material is sectioned, cooled, and then packaged. Note that hot rolled metal is allowed to
cool naturally, which will result in a bit of shrinkage and perhaps minute warping.

Each metal and each fabrication process has its own unique pros and cons, and each is best for
specific applications. Because there is no one size fits all solution, it is vital to work with an expert to
ensure that you choose just the right metal and fabrication process for your specific project.

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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 Sintering Process

Powder metallurgy is the process of creating metal objects from metal powder rather than formed billets.
It is highly useful for smaller items in which casting or forging would create a great deal of loss, for
metals such as tungsten with extremely high melting points, and for creating alloys of mutually insoluble
metals. It is also used when a highly porous item is desired.

Sintering is the process of heating and compacting the metal powder to create the desired object. It is
done at temperatures higher than room temperature but lower than the melting point of the metal.

Solid State Sintering

If solid state sintering is desired, two things must happen after the powder is heated and compacted.
First, the pressing lubricant must be removed through evaporation and vapor burning. Then, the surface
oxides of the powder particles must be removed. At this point, the contact points of the object will grow
“sintering necks” that join them together, which can later be cold welded for strength. Most commonly,
the entire process occurs in a single, continuous furnace kept at an appropriate temperature.

Sinter Hardening

To enhance the strength imparted by sintering, it is possible to accelerate the cooling rate of the
sintering furnace. Special material grades are available that create tougher microstructures at specific
cooling rates.

Liquid Phase Sintering

There are two types of liquid phase sintering: transient and permanent.

Transient liquid phase sintering: When working solely with iron powder, solid state sintering would
lead to shrinkage as the sintering necks develop. Adding fine copper powder, though, guards against
shrinkage and adds extra strength to the finished product. In transient liquid phase sintering, the copper
melts at sintering temperature, diffusing throughout the iron powder.

Permanent liquid phase sintering: In some cases, such as cemented carbides, a permanent liquid
phase is desired throughout the sintering process. This involves adding a melting binder to the
powdered metal. There are three distinct stages to this process:

Rearrangement: During melting, the liquid will be pulled into pores and the grains will rearrange
through capillary action.
Solution-precipitation: Where capillary action is high, atoms will move into solution and then precipitate into areas of lower chemical potential. The result is grain boundary diffusion and
densification.
Final densification: At this point, grains are efficiently packed, allowing liquid to easily flow into pores, gradually densifying the full solid skeletal network.

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 Open Die Forging

Also known as smith forging, open die forging takes its name from the fact that the dies—the surfaces
that make contact with the metal being forged—do not enclose the piece. Instead, the metal flows
freely except in the limited areas where the dies are placed. Open die forging is an important technique
for many manufacturing applications. Here is what you should know.

Capabilities of Open Die Forging

Open die forging allows both rough and finishing shaping work to be done on metal of sizes ranging
from very small to incredibly large. In fact, some open die forges can handle pieces that are 80 feet
long and weigh a whopping 136 metric tons.

Open die forging is difficult, though not impossible, to use for pieces with a great deal of fine detail.
Therefore, except for art pieces and other specialty operations, open die forging is typically used to
create discs, blocks, hugs, shafts, cylinders, flats, plates, sleeves, and other relatively simple shapes.
It is often used to rough-shape ingots in preparation for further forging of a different type.

Common Metals

Steel and similar alloys are the most common metals used in open die forging. However, the process
also works well with a variety of other metals, including alloys of copper, nickel, and titanium.

Open Die Forging Process Operations

While closed die forging can be automated, open die forging is entirely under the control of the
metalworker. The forge operator must continuously orient and position the metal being worked as a
hammer strikes and deforms it to create the desired shape. The dies resemble tools rather than molds
and since the metal flows freely except where it is in contact with the dies, the metalworker must
carefully manage the forging process.

There are three common open die forging processes that are typically performed first, regardless of the
type of metal or what the finished product will be. Taken together, they prepare the metal for further
forging:

Cogging: Cogging is used to reduce a raw bar of metal to the desired thickness. It uses an open die
drop forge to successively deform the bar along its length.

Edging: Generally performed after cogging, edging uses a concave open die to form the metal into the
desired width.

Fullering: Fullering uses a convex open die to thin out sections of the metal as needed.

Benefits of Open Die Forging

Open die forging has a number of benefits over other types of forging. It refines the metal grain,
improving strength and reducing porosity. It improves wear resistance and fatigue resistance. The
improved microstructure reduces the chance of voids.

No single forging process is right for all applications. It is always important to speak with an expert who
can help you decide which process has the most benefits and the fewest drawbacks for your particular
project.

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.

The Differences Between Brass and Bronze

Brass and bronze are often marketed interchangeably, but they are far from the same material. Both
play a valuable role in modern manufacturing, but one is often more suitable for a particular application
than the other. To know which is best for your project, it is essential that you understand the differences
between the two. Here are the basic differences between brass and bronze.

History

Bronze is far older than brass, dating to the Sumerian people around 3500 BC. A far stronger and more
durable material than stone and copper, the discovery of bronze gave mankind the hallmarks of the
Bronze Age, including more detailed metal sculptures, new decorative tiles, and a wide range of new
tools, weapons, and armor.

Brass was discovered in approximately 500 BC. Its natural golden color and tarnish resistance made
brass useful for the production of coins and other items where a lustrous appearance was desired.
However, it was difficult in those days to create brass, so it was not until medieval times that brass
became a commonly used material for church monuments and wire. By the 17th century, brass was the
alloy of choice for instruments that required accuracy, such as clocks, navigational aids, and precision
scientific instruments.

Composition and Properties

Bronze is a metal alloy based on copper and tin. Other elements such as aluminum, silicon, phosphorus,
and manganese may also be added. It is brittle and hard, but resists corrosion and metal fatigue better
than steel. Bronze is a good conductor of both electricity and heat. Its color is reddish-brown.

Brass is a metal alloy based on copper and zinc. Iron, silicon, aluminum, and manganese may be added
to improve corrosion resistance. Brass is more malleable than either zinc or copper, and it has a relatively
low melting point of 900 C. Brass is not as hard as steel. It has the appearance of muted, dull gold.

Uses

Bronze is particularly useful in marine applications due to its corrosion resistance. It is frequently used
to create cast sculptures, and it is generally considered one of the best materials for creating bells and
cymbals. Industrial uses for bronze include bearings, springs, electrical connectors, and a variety of clips.

Brass is commonly used for decorative pieces, and it imparts excellent acoustic properties to a variety of
musical instruments. It is also common in applications that require low friction, such as valves, gears,
doorknobs, ammunition, and locks. It is not prone to sparking, so it is often used for zippers as well as
fittings and tools that will be used around explosive gases. Brass is also a popular choice for boat
hardware.

Both brass and bronze are in common use today. However, they are not the same material, and their
properties differ significantly. Make sure you choose the metal that is truly the best option for your project.

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 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.