ABOUT
DURALOY > Manufacturing Processes
Duraloy utilizes two casting processes in our Scottdale, Pennsylvania foundry - static casting and centrifugal casting. Both processes require a high level of process control to produce high quality parts. In addition to casting, Duraloy offers complete welding and fabrication services, utilizing automatic and stick TIG and MIG processes.
 Centrifugal Casting
Centrifugal casting or "spincasting" was developed in France in the 1800's as a means to efficiently cast iron sewer pipe. Even today, much of the water and sewer pipe produced in the world is manufactured using the centrifugal casting process. In the early 1900's, companies started to experiment with casting other alloys using this process. In the 1940's, Thomas Heyward, founder of Duraloy, experimented with centrifugal casting of heat resistant alloys to produce long tubes in heat resistant materials.
Basically, making a centrifugal casting involves preparing a mold by securing "end caps" to both ends of the mold. The mold itself is a forged steel tube that has been machined on the inside to a specific diameter required to match the O.D. of the tube to be cast. After the end caps are secured, the inside of the mold is coated with a ceramic coating to keep the metal being poured from attaching to the mold. The mold is then heated and placed on a centrifugal "spinner". The mold is then rotated, or "spun" at a very high speed. Hot metal is poured into the rotating mold from one end. The centrifugal force, created by the rapidly spinning mold, forces the liquid metal against the inside of the mold. The mold continues to spin until the hot metal has solidified. The mold is then stopped, the end caps removed, and the cast tube is pulled out of the mold.
As a result of the high g-force applied to the metal by the spinning mold, the slag and impurities are displaced to the center of the casting where they are easily removed by machining. The result is a tube with a homogenous, very densely packed grain structure, ready for use or incorporation into an assembly.
Static Casting
 Static casting is one of the oldest methods of casting metal. Basically, static casting involves the pouring of hot metal into a shaped mold. The term "static" comes from the fact that the mold is "static", or not in motion and that there are no external forces, other than gravity, that are applied to the metal as it fills the mold. This "static" mold differentiates the process from other dynamic processes, like injection casting and centrifugal casting.
Generally, the differences in static processes comes from the materials that are used to make the shaped mold. Many different molding media are used, with the most common being sand and ceramic. Duraloy utilizes a "No Bake" or "Air Set" sand molding process. This means that the sand that is used to form the mold is mixed with a binder (a glue-like material that holds the sand together) and the binder cures or hardens in air, without having to be heated in a curing oven (hence the term "No Bake").
Making a static casting starts with a pattern, usually made of wood or plastic. The pattern material has been formed to copy the shape of the outside dimensions of the part to be produced. In more complex molds, a "core" can also be placed in the mold to copy the shape of the inside of the part to be cast. This would allow the production of small tubes, elbows, return bends and other parts that have both inside and outside shaping. The pattern is then mounted on a board and "gated". Gating involves designing how the casting should be filled metal and installing wooden molds to create pathways in the sand mold for hot metal to fill the cavity and allow gases to escape.
After the pattern is produced, it is placed into the bottom of a box. The box is then filled with the resin-sand, packing the sand around the part to insure that there are no air pockets or voids in the sand. The filled box is allowed to sit in for a few minutes to allow the air-set resin to harden. The box and pattern are removed and what is left is a "negative" image of the desired part molded into sand.
From there, the sand mold is filled with hot metal and allowed to cool. When hot metal is introduced, through the gates, the cavity containing the shape of the desired part is filled with the hot metal, with unwanted gases being allowed to escape out of the top of the mold. The entire mold is allowed to cool to room temperature (about 1 day). After cooling the sand is broken away from the raw casting. The casting is then sent through final processing where it is cleaned, trimmed, ground and tested, prior to shipment.
 Welding and
Fabrication
Duraloy offers complete fabrication services for petrochemical tubes and assemblies, furnace and CAL/CGL roll fabrication and radiant tube assemblies. Most of the fabrication that Duraloy performs is done by welding, however, we can also bolt assemblies together as well as "shrink fit and pin" assemblies.
Each assembly is custom manufactured to the customer's specifications and drawings. Duraloy utilizes MIG, automatic and manual TIG process and all welding procedures are qualified to ASME Section IX specifications. Backed up with complete radiographic, hydro and other non-destructive testing operations, Duraloy is able to offer components that are ready for installation upon delivery.
Other Processes
 In addition to the above manufacturing processes, Duraloy also offers machining, radiography and a metallurgical characterization and testing lab, complete with room temperature and high temperature tensile testing, high temperature creep-to-rupture testing, chemical analysis, and microstructure evaluation and quantification.
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