Patent Application
20180111187
The present disclosure is related to methods and systems for casting metal, and more particularly to methods and systems for casting metal using metal shot casting molds.
Foundries produce metal castings using a casting process. The casting process is characterized by using mold material. A frame or mold box known as a flask contains the molding material. A foundryman creates mold cavities by compacting molding material around mold patterns within the flask. The metal casting is formed by filling the mold cavities with molten metal. The molten metal cools to form a solid metal casting. The composition of the molding material may affect the cooling rate of the metal.
The teachings of the present disclosure relate to a system and a method for casting metal. In accordance with one embodiment, a metal casting system includes a cope mold portion and a drag mold portion that form mold cavity. The cope mold portion comprises internal cope mold walls. The drag mold portion comprises internal drag mold walls. The cope mold portion and the drag mold portion comprise a molding material comprising a plurality of metal particles. The mold cavity is representative of a mold pattern. The internal cope mold walls and the internal drag mold walls define, at least in part, the perimeter of the mold cavity.
According to another embodiment, a metal casting method includes positioning a cope mold portion of a molding flask and a drag mold portion of a molding flask to create a passageway between a cavity representative of a mold pattern and an external portion of the molding flask. The cope mold portion and the drag mold portion comprise a molding material comprising a plurality of metal particles. The method further includes filling the cavity, at least partially, with a molten alloy to create a metal casting, the metal casting created by the solidification of the molten alloy. The method further includes removing the cope mold portion and the drag mold portion from the metal casting.
In yet another embodiment, a metal casting method includes receiving a first casting mold comprising a molding material comprising metal particles and one or more other media, the molding material used to create a cavity in the first casting mold. The method further includes extracting the molding material from the first casting mold. The method further includes separating the metal particles in the molding material from the one or more other media. The method further includes combining at least a portion of the separated metal particles and at least a portion of the one or more other media to create a reclaimed material. The method further includes forming a second casting mold using the reclaimed material. The method further includes creating a metal casting using the second casting mold.
Certain embodiments may provide one or more technical advantages. In some embodiments, a metal casting system comprising a molding material comprised of metal particles may allow molten alloy to solidify relatively quickly in the casting process. Generally, the mechanical properties of the solidified metal are higher when the molten alloy cools more quickly. As another example, the outer perimeter of a metal casting is generally relatively well defined compared to traditional metal castings due to increased integrity of the casting mold. These embodiments reduce or eliminate the need to machine the metal casting, thus reducing labor costs. In yet another embodiment, the molding material comprised of metal particles result in a casting mold does not require machining after each casting, thus reducing labor costs. As yet another advantage, using a molding material comprised of metal materials may reduce the cost of casting metal, as this contemplated molding material may be created and maintained at a reduced cost relative to other available molding materials.
Other technical advantages will be readily apparent to one of ordinary skill in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.
A more complete understanding of particular embodiments will be apparent from the detailed description taken in conjunction with the accompanying drawings in which:
Foundries produce metal castings using a casting process. The casting process is characterized by using mold material. A frame or mold box known as a flask contains the molding material. A foundryman creates mold cavities by compacting molding material around mold patterns within the flask. The metal casting is formed by filling the mold cavities with molten metal. The molten metal cools to form a solid metal casting. The composition of the molding material may affect the cooling rate of the metal. Generally, molding material that allows the molten metal to cool faster produces metal castings with higher mechanical properties.
Conventional methods of casting metal have included sand molds and graphite molds into which a molten alloy is poured. Sand resin molds may have a relatively low thermal transfer property. Thus, molten alloy poured into a sand mold may cool relatively slowly, causing the solidified alloy to have low mechanical properties. In some embodiments, molten alloy that cools slowly causes the various alloying elements to segregate, thus creating non-uniform properties. In some embodiments, a steel casting may require high mechanical properties. For example, a steel casting may be used to create an armored plate. If the molten alloy used to create the armored plate cools too slowly in the casting process, the elements of the solidified alloy may segregate when hit with projectiles, thus making the metal casting unsuitable as an armored plate.
As another example, metal castings made with sand resin molds may not have a smooth surface, due, at least in part, to the low thermal transfer properties of the sand resin. Thus, casting molds made with sand resin may require machining, which may be a time and labor intensive process. In certain circumstances, metal castings may not be able to be machined. For example, when the metal casting is a railcar wheel, the outer perimeter—or tread—of the metal casting may not be able to be machined due to the required shape and structural integrity requirements of the tread. For example, machined metal castings for a railcar wheel creating using a sand resin mold may be unusable due to the inability of resin bonded sand molds to hold the tight concentricity, flatness, and roundness requirements of railcar wheels.
Graphite molds may be cost prohibitive. For example, graphite molds may be expensive to produce. As another example, graphite molds generally have a relatively short life expectancy. Graphite molds may require a relatively high amount of maintenance due to their susceptibility to oxidize in the presence of air. For example, graphite molds may require a prohibitive amount of machining, thus increasing labor costs.
This disclosure contemplates a molding material made of metal particles, such as steel shot and/or iron shot. A molding material made of metal particles may alloy molten alloy to cool relatively quickly. The contemplated molding material may reduce the cost of metal casting systems.
As illustrated, metal casting system 100 also includes a sprue 120 and riser sleeve 122. Sprue 120 is a passageway through which a foundryman introduces molten alloy into mold cavity 116. One end of sprue 120 forms an opening in an external wall of flask 110, and another end connects to mold cavity 116. The cope and drag mold portions support sprue 120. Riser sleeve 122 receives molten alloy after it flows through sprue 120 and mold cavity 116. As another example, molten alloy may be poured directly into riser sleeve 122. A top end of riser sleeve 122 forms an opening in an external wall of flask 110. A bottom end of riser sleeve 122 connects to mold cavity 116.
Molding material 118 may comprise metal particles. Metal particle may allow molten alloy to cool quicker than a molding material made of, for example, sand. For example, molding material 118 may comprise steel particles such as steel shot and/or steel grit. As another example, molding material 118 may comprise iron particles such as iron shot and/or iron grit. In some embodiments iron particles are used when creating a metal casting of bronze, brass, copper, and/or aluminum alloys. Molding material 118 may comprise any suitable type of metal. Molding material 118 may comprise any suitable size of metal particles. In an embodiment, molding material 118 may comprise S-330 steel shot grade. Molding material 118 may comprise any suitable grade of steel shot. In some embodiments, molding material 118 may comprise standard metal shot. For example, molding material 118 comprises standard steel shot typically used in shot blasting machines. The embodiments may reduce or eliminate the need to “condition” the metal particles (e.g., impacting the metal particles to create irregularities at the surface).
In some embodiments, molding material 118 may comprise chromite. For example, molding material 118 may comprise chromite sand. When molten alloy is poured and contacts molding material 118 made of metal particles, the metal particles may melt. The melted metal particles may fuse to the casting or create voids at the surface of the metal casting, creating an irregular shaped metal casting. Introducing chromite to molding material 118 may reduce or eliminate these disadvantages. In some embodiments, molding material 118 comprises at most 85% metal particles. In some embodiments, molding material 118 comprises 70% by weight of metal particles. In some embodiments, molding material 118 may comprise at least 25% by weight of sand material. For example, molding material 118 may comprise 85% by weight of steel shot and 15% by weight of sand material. As another example, molding material 118 may comprise 70% by weight of metal particles and 30% by weight of sand material. As yet another example, molding material 118 may comprise 60% by weight of metal particles and 40% by weight of sand material. Molding material 118 may comprise any suitable type of sand material, such as chromite sand, zircon sand, synthetic sand, and/or ceramic sand.
Molding material 118 may comprise binding material. Binding material is used to bind the metal particles and/or chromite. In some embodiments, individual steel particles and/or chromite particles may not, alone, bind together. A binding material may be introduced to bind the particles to, for example, create the mold elements of metal casting system 100. Binding material may be a standard foundry binder. For example, binding material may be a no-bake type binder such as a two-part binder system or a three-part binder system that sets as a result of a chemical reaction. As another example, binding material may comprise a cold box-type binder that is cured using a gas. This disclosure contemplates any suitable type of binding material. That is, binding material may be any type of binding material that is presently known or developed in the future.
As discussed, molding material 118 comprising metal particles allows molten alloy to cool relatively quickly. As another advantage molding material 118 may reduce the cost of creating casting with system 100. The molding material 118 contemplated in this disclosure, unlike certain traditional graphite molds, may be more cost efficient in some embodiments. After a casting is created, the metal particles in molding material 118 may be reclaimed. For example, the metal particles may be extracted from molding material 118. In some embodiments, the chromite may be extracted from molding material 118. For example, the metal particles and chromite may be magnetically separated from molding material 118. These materials may be remixed to create new molding material 118 used in a new metal casting system 100. In an embodiment, the metal particles and chromite sand may be reused indefinitely, resulting in a more cost efficient way to create metal casting system 100.
When implementing particular embodiments of metal casting system 100, a foundryman packs molding material 118 around various patterns to form mold cavity 116 and sprue 120. The foundryman may insert one or more riser sleeves 122 between mold cavity 116 and an external wall of flask 110. One of skill in the art would recognize that both the positioning and the number of passageways, such as sprues 120 and riser sleeves 122, may vary depending on various factors such as the mold pattern and the metal alloy used in a particular metal casting. The foundryman assembles flask 110 by coupling drag mold portion 114 to cope mold portion 116. The foundryman pours molten alloy into sprue 120 and/or riser sleeve 122. The molten alloy flows through sprue 120 where it fills mold cavity 116 and riser sleeve 122. In some embodiments, the foundryman may pour molten alloy directly into riser sleeve 122. As the molten alloy solidifies and shrinks in mold cavity 116, molten alloy flows from riser sleeve 122 back into mold cavity 116 to compensate for the shrinkage. The molten alloy solidifies to from a metal casting. In some embodiments, the metal casting is all, or a portion of, a railcar wheel. In some embodiments, the metal casting is all, or a portion of, an armored plate. The metal casting may be used for any suitable purpose.
Particular embodiments of metal casting system 100 may provide for more efficient solutions. For example, a metal casting system comprising a molding material comprised of metal particles may allow molten alloy to solidify relatively quickly in the casting process. Generally, the mechanical properties of the solidified metal are higher when the molten alloy cools more quickly. In yet another embodiment, the molding material comprised of metal particles result in a casting mold does not require machining after each casting, thus reducing labor costs. For example, creating a metal casting may alter a casting mold's shape. In a traditional graphite casting mold, the graphite may be machined to attempt to bring the casting mold's shaped to the original shape. The casting mold contemplated in this disclosure, however, does not require machining because molding material 118 may be used to easily and efficiently create a new casting mold. As yet another advantage, using a molding material comprised of metal materials may reduce the cost of casting metal, as this contemplated molding material may be created and maintained at a reduced cost relative to other available molding materials. As yet another advantage, molding material 118 may facilitate a structurally sound casting mold with high mold hardness. This high mold hardness facilitates more accurately defining the final shape of a metal casting. This facilitates creating a more accurate metal casting that may be used without machining.
At step 510, the foundryman pours molten alloy into sprue 120. The molten alloy flows through sprue 120 where it fills mold cavity 116. The molten allow may also fill all or a portion of one or more riser sleeves 122. In some embodiments, the foundryman may pour molten alloy directly into one or more riser sleeves 122. After the molten alloy solidifies, the cope mold 114 and drag mold 112 separated to remove the metal casting at step 515.
Modifications, additions, or omissions may be made to the method described herein without departing from the scope of the present disclosure. For example, the steps may be combined, modified, or deleted where appropriate, and additional steps may be added. Additionally, the steps may be performed in any suitable order.
The molding material elements may be combined to create molding material 118 at step 620. In an embodiment, molding material elements (e.g., metal particles and chromite sand) are mixed to create molding material 118. For example, the molding material elements may be mixed using a foundry mixer. In an embodiment, a binding material may be used to combine the molding material elements. The combined molding elements may be used to create a casting mold 100 at step 625. As discussed, molding material 118 may be used in conjunction with a mold pattern to create molding system 100. The casting mold created at step 625 may be used to create a metal casting, as discussed, at step 627.
The method then proceeds to step 630 where a foundryman, or any other suitable person or machine, determines whether to create a new metal casting system 100. For example, the metal casting system 100 created in step 625 may be used to make a new metal casting, such as a railcar wheel casting. If it is determined to create a new metal casting system 100, the metal casting system 100 created in step 625 (or any other metal casting system 100) may be broken down to create the new metal casting system 100 beginning at step 605. If it is determined that a new metal casting system 100 does not need to be created, the method ends.
Modifications, additions, or omissions may be made to the method described herein without departing from the scope of the present disclosure. For example, the steps may be combined, modified, or deleted where appropriate, and additional steps may be added. Additionally, the steps may be performed in any suitable order. As another example, method 600 may begin at step 610. In this embodiment, molding material 118 is received outside of a metal casting system 100.
Particular embodiments of method 600 may provide for more efficient solutions. Method 600 may allow for the efficient reuse of molding material 118. In some embodiments, the media in molding material 118 may be used indefinitely. In some embodiments, the media in molding material 118 may be easily separated, for example, by using magnetization. The media in sand resin molds may be difficult or impossible to separate. Additionally, a foundryman does not need to melt the metal particles in molding material 118 to reuse the molding material 118. For example, it is impractical or impossible to create a new casting mold made of graphite molding material. It may be impractical or impossible to re-melt graphite molding material. As discussed, a graphite mold may require machining between uses. Generally, after the graphite mold is machined a several times, the mold becomes unusable. Thus, the graphite molds may be discarded after a relatively small number of uses.
Although embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various other changes, substitutions, and alterations may be made hereto without departing from the spirit and scope of the invention as defined by the claims below. For example, although this disclosure generally refers to a metal casting as a railcar wheel and an armored plate, a metal casting created using this systems and methods described herein may refer to any suitable type of metal casting. As another example, although particular steps have been described as being performed by a foundryman (e.g., pouring molten alloy, extending riser sleeves, etc.) many of those steps may also be machine automated.
