Patent Application
20170087627
This application claims priority to International Application No. PCT/US2014/014,900, filed Feb. 5, 2014, which claims priority to U.S. Provisional Application No. 61/766,334, filed on Feb. 19, 2013.
This disclosure relates to a die casting die and system used in high temperature die casting.
Generally, die casting is a process that includes forcibly moving molten metal into a die cavity to form a desired shape. More particularly, the process includes the steps of forcing molten metal into the die, retaining the metal in the die until it solidifies, and removing the solidified part from the die.
One of the largest challenges in die casting is developing die materials and a die configuration in order to maximize die life while minimizing die cost. Because die casting is performed at high temperatures, thermal mechanical fatigue can occur in the dies.
In one exemplary embodiment, a die casting die includes a shoe comprised of a first material and includes a pocket. An insert is arranged in the pocket. The insert is comprised of a second material that is different from the first material and the insert provides a contoured surface. A coating is on the contoured surface. The coating provides a cast part contour.
In a further embodiment of any of the above, the first material has a thermal conductivity between 12 W·m−1K−1 and 62 W·m−1K−1.
In a further embodiment of any of the above, the first material comprises steel.
In a further embodiment of any of the above, the second material has a thermal conductivity above 350 W·m−1K−1.
In a further embodiment of any of the above, the second material comprises copper.
In a further embodiment of any of the above, the coating has a hardness between 36 HRC and 62 HRC.
In a further embodiment of any of the above, the coating includes at least one of a cobalt chromium alloy, a cobalt alloy, and ceramic.
In a further embodiment of any of the above, the shoe includes at least one passage for circulation of fluid.
In another exemplary embodiment, a die casting system includes a first die including a first shoe comprised of a first material. The first shoe includes a first pocket. A first insert is arranged in the first pocket. The first insert is comprised of a second material that is different from the first material. The first insert provides a first contoured surface, and a first coating on the first contoured surface. The first coating provides a first cast part contour. A second die includes a second shoe comprised of the first material. The shoe includes a second pocket. A second insert is arranged in the second pocket. The second insert is comprised of the second material. The second insert provides a second contoured surface and a second coating on the second contoured surface. The second coating provides a second cast part contour. The first die and the second die are arranged to form a die cavity. A chamber is in fluid communication with the die cavity, and a plunger for injecting a molten metal through the chamber into the die cavity.
In a further embodiment of any of the above, the first material has a thermal conductivity between 12 W·m−1K−1 and 62 W·m−1K−1.
In a further embodiment of any of the above, the first material comprises steel.
In a further embodiment of any of the above, the second material has a thermal conductivity above 350 W·m−1K−1.
In a further embodiment of any of the above, the second material comprises copper.
In a further embodiment of any of the above, the first and second coatings have a hardness between 36 HRC and 62 HRC.
In a further embodiment of any of the above, the first and second coatings comprise at least one of a cobalt chromium alloy, a cobalt alloy, and ceramic.
In a further embodiment of any of the above, at least one shoe contains at least one passage for the circulation of fluid.
In a further embodiment of any of the above, the die casting system includes a multiple of fluid lines attachable to the at least one fluid passage. The multiple of fluid lines are connectable to a cooling fluid source for fluid communication between the at least one shoe and the cooling fluid source.
In another exemplary embodiment, a method for die casting includes arranging a first die and a second die to form a cavity. The first die includes a first shoe comprised of a first material. The first shoe includes a first pocket. A first insert is arranged in the first pocket. The first insert is comprised of a second material that is different from the first material. The first insert provides a first contoured surface and a first coating on the first contoured surface. The first coating provides a first cast part contour. The second die includes a second shoe comprised of the first material. The shoe includes a second pocket. A second insert is arranged in the second pocket. The second insert is comprised of the second material. The second insert provides a second contoured surface and a second coating on the second contoured surface. The second coating provides a second cast part contour. The method includes forcing molten metal into the cavity. The method includes retaining the molten metal in the cavity until the molten metal becomes a solidified metal, and removing the solidified metal from the cavity.
In a further embodiment of any of the above, at least one shoe includes passages for circulation of fluid during the retaining step.
In a further embodiment of any of the above, the second material comprises copper.
The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
The first die 12 includes a first shoe 22 having a first pocket 24. A first insert 26 arranged in the first pocket 24. In the example, the first insert 26 is a separate structure from, but removably affixed to the first shoe 22. The first insert 26 provides a contoured surface 28. The contoured surface 28 is coated with a coating 30, which provides a contour of the part to be cast.
One of ordinary skill in the art would recognize that the system disclosed is not limited to having two dies with one insert in each die. For example, more than two dies could be implemented, as could more than one insert in each die.
In an example embodiment, the first shoe 22 and the second shoe 32 are comprised of a material having a thermal conductivity between 12 W·m−1K−1 and 62 W·m−1K−1. Example materials in this range that could be used for the shoes 22, 32 include, but are not limited to, steel and steel alloys. A steel or steel alloy die shoe will provide high strength to the die while also acting as a heat sink.
The first insert 26 and the second insert 36 are comprised of a highly thermal conductive substrate having a thermal conductivity above 350 W·m−1K−1. Example materials in this range that could be used for the inserts 26, 36 include, but are not limited to, copper and copper alloys.
The insert coatings 30, 40 are approximately 0.1 inches (2.54 mm) thick and are provided by a material having a hardness between 36 HRC and 62 HRC. Materials in this range that could be used as the coatings 30, 40 may be at least one of a cobalt chromium alloy, a cobalt alloy, and ceramic. Coating the insert will provide a deposited hard faced layer that will resist the thermal shock on the insert during injection. The disclosed configuration will transfer heat extremely quickly to the die shoe, reducing the amount of stress on the inserts.
In the example, at least one of the shoes 22, 32 may include at least one passage 42 for the circulation of fluid to regulate the temperature of the die casting system. As illustrated in
By staggering the thermal conductivity of the die casting system as done in the example embodiment, the heat from the molten metal injected into the die cavity 16 will be quickly transferred to the shoe 22, 32 and removed by the hot oil, which will increase the life of the die insert 26, 36. Furthermore, the preferred embodiment is constructed from relatively inexpensive materials. The wear surface of the die assembly is a deposit coating 30, 40 that can be easily refurbished as necessary.
The system may be used in hot chamber and cold chamber die casting. Generally, the die casting process involves forcing molten metal into the cavity 16 formed by dies 12, 14, retaining the metal until the molten metal solidifies into the desired cast part, and then ejecting the solidified metal cast part from the die cavity 16. In the preferred embodiment, this process will include the circulation of fluid through at least one passage 42 in at least one of the shoes 22, 32 in order to regulate the temperature of the die system. This circulation of fluid will occur during the molten metal retention process, and may be implemented during other steps as well.
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
