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.

World Cup 2018

History of the World Cup Trophy

It may not be made of Bronze, but is made out of a precious metal!

The FIFA World Cup Trophy has become the most sought after and recognized sporting prize in the world and holds a universal appeal that is unique to the sport of football.
However, the current trophy is actually the second generation of the coveted prize. The first trophy – named the Jules Rimet Cup in 1946 in honour of the founding father of the FIFA World Cup™ – was commissioned from French sculptor Abel Lafleur by FIFA. The trophy was a depiction of the goddess of victory holding an octagonal vessel above her head, produced in gold with a base of semi-precious stones.

The Jules Rimet Cup had an eventful history, beginning with a period spent hidden in a box under a bed during World War II. It was later stolen in 1966 while on display in England. With the help of a dog named Pickles, the famed English detectives of Scotland Yard were able to retrieve the Trophy, which was hidden in a suburban garden.

At that time, FIFA regulations stated that any nation winning the FIFA World Cup three times would become permanent owners of the Trophy. Brazil did just that, taking home the Trophy in 1970 only to have misfortune follow in 1983, when the Trophy was stolen in Rio de Janeiro, only this time it was never to be seen again. It is widely believed that it was melted down by thieves.

In the early 1970s, FIFA commissioned a new trophy for the tenth FIFA World Cup™, which was to take place in 1974. Fifty-three designs were submitted to FIFA by experts from seven countries, with Italian artist Silvio Gazzaniga’s work ultimately winning the vote.

Gazzaniga described his creation thus: ”The lines spring out from the base, rising in spirals, stretching out to receive the world. From the remarkable dynamic tensions of the compact body of the sculpture rise the figures of two athletes at the stirring moment of victory.”

The original FIFA World Cup Trophy cannot be won outright anymore, as the new regulations state that it shall remain in FIFA's possession. Instead, the FIFA World Cup™ winners are awarded a replica which they get to keep as a permanent reminder of their great triumph. The gold-plated replica is referred to as the FIFA World Cup Winners’ Trophy.

The authentic, one-of-a-kind FIFA World Cup Trophy is 36.8cm (14.5 inches) tall, weighs in at 6.142kg (13.54 pounds), and is made of 18-carat gold. The base contains two layers of semi-precious malachite while the underside of the trophy is engraved with the year and name of each FIFA World Cup™ winner since 1974. Following the 2014 FIFA World Cup™, the vertical alignment of the champions’ engraved names needed to be redesigned to fit future title holders. The list of world champions since 1974 was therefore rearranged into a spiral to accommodate the names of the winners of future editions of the tournament.

Information courtesy and copyrighted by FIFA.com

Oil & Grease Lubrication for Made to Order Bearings

Oil & Grease Lubrication for Made to Order Bearings

          The importance of an oil depends mainly on its film forming ability which depends further on its viscosity.

         An oil of lowest viscosity is generally more suitable for an application since a higher viscosity oil will waste power to overcome the internal friction of the oil itself

          There are many ways to supply a lubricant to a bearing.  We will explore the different options below.

    

Pressure lubrication is probably the most positive and efficient means to provide lubricant to a bearing.
In addition to offering a more copious supply of oil lubricant, up to an average pressure of 50 PSI, it coats the bearing, maintaining a more stable viscosity range and it assists in flushing out dirt and wear debris from the bearing surface.

        

Oil bath lubrication is where the bearing is submerged in oil which makes it the next reliable method to the pressure-fed oil. The shaft speed should not be so great as to cause excessive churning of the oil.

Splash-fed lubrication involves the oil being splattered onto the bearing surface by movement of other adjacent parts. The housing should be reasonably oil-tight to prevent excessive loss and leakage of the lubricant.

         

Oil ring lubrication involves a revolving or processing ring on a shaft in contact with the oil sump. When the shaft is at low speed, sufficient oil may not be brought to the bearing surface or if the shaft speed is too great, the oil will be centrifuged beyond where it is needed. It also may not keep pace with the oil required.

For best results, it has been proposed that the peripheral speed should be in the range of 200 to 2000 feet per minute. The safe load based on full hydrodynamic lubrication mode should be reduced by one half of pressure lubricated bearings.

Wick or waste-pack lubrication delivers oil to a bearing surface by capillary action of a wick or waste-pack as done in many old railroad axles using bobbitted bronze backed partial sleeve bearings. The safe load when compared with pressure-fed full hydrodynamic load should be reduced to 1/4 of the load.

Grease-packed bearings: Grease is generally packed to surround the bearing and although is substantially less effective than oil, it is much more permanent but the bearing will generally operate in boundary conditions.

  Lubricant Selection

           The selection of a lubricant is based on various factors such as the type of operation, whether full hydrodynamic, mixed film or boundary film conditions in addition to the surface speed and bearing load involved.
 

          Various lubricant articles suggest some recommended viscosities for specific services.
 

          As a rule of thumb, the following suggested viscosities should be considered on the basis of surface speed with a qualified load.

                                Speed(fpm)                 Viscosity(sus)                   SAE Oil
                                 30 or less                       1200-1800                           80
                                 70                                    800-1200                           70
                                 150                                  500-800                             60
                                 300                                  300-500                             50
                                 600                                  150-300                             40
                                 1200                                120-150                             30
                                 2400                                  90-120                             20
                                 5000                                  40-90                               10
                                 over 5000                            5-40                                 5

          As a general rule of thumb, heavier oils are recommended for high loads and lighter oils for high speeds.
 

          In order to obtain a quick conversion of viscosity (sus) to centistokes (cSt), multiply the (cSt) value by 5. The multiple will be the approximate (sus) value.

         To obtain the (cSt) value, divide the (sus) value by 5.

         These results are reported to be accurate within 7% in the range of75 to 7000 (sus) and 15 to 1500 (cSt).

          But also be cautioned that this assumption should not be used below 75 (sus) or 15 (cSt).

          For more explicit lubrication data, we suggest you refer to the CBBI manual or to the Machine Design article of March 10, 1966.

I hope post wasn't too DRY for you and this helped you learn about lubricating methods with ease. 

Anyway, that's it for now.  Until next time my metal loving friends...

Bearing Design Guide: Chapter Sixteen: Effect of the Casting Method on Bronze Alloys

          The casting method should not be ignored but given consideration of the type of service the bronze alloy will be subjected to.

           In particular, the type of load - whether steady and continuous, intermittent or with shock impact or pounding loads - the surface speeds to be encountered and other important features required to be met.

          The casting method has a definite impact on the bronze alloy such as the resulting grain size, density, hardness, mechanical and physical properties, soundness and structure.

          In general, the slower chilled or cooled casting will give rise to coarser and larger grain size. These have a profound effect on the surface qualities, coefficient of friction, wear rate or wear resistance and loads.

          The faster cooled or chilled castings result in greater density, hardness, finer grain size, improved soundness and structure.

           Referring to the illustrations on the following page, please note the finer grain sizes developed by each method of casting.

          Sand Casting: Since molten bronze is poured into a sand mold, the sand or silica having thermal insulating characteristics, will cause slow cooling or chilling of the casting in air. This slow cooling permits the grain size to grow larger, the density, the soundness and structure to be less than by other casting methods.

          Permanent Molded or Chill Casting: The thermal insulating sand is replaced by nickel steel or cast-iron dies. The metal mold quickly chills the casting and this faster solidification results in finer grain size, no interconnected porosity, finer surface finish and improved physical and mechanical properties.

          Centrifugal Casting: Molten metal is poured into a rotating steel or cast-iron die. The centrifugal force impacts the molten metal against the inside of the die, eliminating any porosity. the rotating or spinning die is then sprayed with water coolant to obtain a faster chill than the first two methods discussed the finer grain size further improves the physical and mechanical properties still further.

         Continuous Casting: The molten metal flows by gravity through a graphite die which is chilled
immediately by the cooling jacket surrounding the die. This faster cooling further reduces the grain size and results in still higher physical and mechanical strength.

          The average increase progressively in the tensile and yield strengths is about 5000 to 10,000 PSI and hardness is increased by 10 to 20 points of Brinell hardness.

          Remarks: To further enhances the physical and mechanical properties of the bronzes, extrusion and forging operations can reduce the grain size additionally. These are special processes and the four methods of casting described earlier in this chapter cannot achieve comparable mechanical and physical strength.

Casting Effect On Grain Size and Density

          So...as you can see above, things may look the same on the outside, but they can be very different on the inside.  It is always important to really understand the final application your part will be used in so you know which casting method would be best for you.

          Well...that's it for today. I say goodbye for now. Until next time my metal loving friends...

How Atlas Bronze Could Help if Santa's Sleigh Broke Down on Christmas Eve

          Every Christmas Eve, countless children lie restlessly in bed, thinking about all the toys that they hope to find under the tree on Christmas morning. They’re barely able to contain themselves as they anxiously await Santa’s arrival, depending of course on how well-behaved they were the past year. 

          

          I love watching my kids look up into the dark, winter sky from their bedroom windows, waiting to catch a glimpse of Santa’s sleigh flying through the air. They point and jump up and down when they see Rudolph’s red nose, and I agreeably nod, even though I know it's simply a blinking airplane light. So few things are as boundless as a child’s imagination! 

          

          One day, a terrible thought crossed my mind. What if  this all really happened and Santa's sleigh did in fact breakdown right before the big day or how devastating would it be if his sleigh broke down during his annual expedition to deliver gifts to the girls and boys of the world? The kids would wake up and rush down the steps only to find the terrifying sight of a Christmas tree without of any gifts beneath it. 

          Well, if Santa’s sleigh did break down, I know just the people who could (probably) fix it. Atlas Bronze of course! 

          If Santa’s sleigh was a real vehicle making these millions of trips all around the world in one night, an obvious source of potential troubleshooting would be with the engine. First, Atlas Bronze would go straight to the source and inspect the engine’s valve seats, or the strength center part of the engine that prevents harmful gases from leaking into the manifold. Aluminum bronze is a key component of the valve seat and also helps prevent corrosion. With the addition of bronze parts for added strength, Santa’s sleigh would be dashing through the snow again in no time!

          Since Santa has been so busy making a list and checking it twice, we’re sure he hasn’t thought about the exterior of his sleigh and how it could endanger him on his merry travels. Before Saint Nick goes on his merry way, he would need to incorporate some architectural bronze into the exterior. Bronze is commonly used in the production of doors, making them nice and strong. As an added bonus, bronze will not generate sparks when struck against a hard surface. So, as Santa lands up on the housetop with a click, click, click, he can ensure that his trusty sleigh won’t slide off of the roof.

          Finally, you can’t forget about the bronze sleigh bells on the reindeer's harnesses. As Santa’s original bells may have rusted over many years, he might go to Atlas Bronze to get the materials he needs for a shiny new outfit for Rudolph.

So, whether its Santa's sleigh or a piece of your machinery we are just a phone call away to save the day!