Patent Application
20180029113
The present disclosure relates to casting. More specifically, the present disclosure relates to direct squeeze casting.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Current manufacturing processes for producing engine components of a motor vehicle, for example, cylinder blocks include high pressure die cast (HPDC) processes. Typically, as molten metal is directed to a mold, HPDC high velocity fill processes entrain air, generate oxides and have difficulty addressing metal shrinkage from certain regions within the mold. Other processes include precision sand casting which employs a bonded sand core pack mold with a large thermal bulk head chill and head deck risers to achieve desired material properties. Precision sand casting, however, is a costly process reserved for components requiring high integrity and enhanced material properties.
Accordingly, there is a need in the art for a cost efficient casting process for producing high quality and performance cast components.
The present invention provides a system to cast structural components. Accordingly, in one aspect of the present invention, a casting system includes a pour cup, a plurality of runners that receive molten metal from the pouring cup, a top mold and a bottom mold that receive the molten metal from the plurality of runners, and a plurality of slides positioned within the top mold and the bottom mold. The positioning of the plurality of slides applies direct pressure on the molten metal in the top mold and the bottom mold to form a high integrity casting component.
The foregoing aspect can be further characterized by one or any combination of the features described herein, such as: the pour cup is a gravity pour cup; the pour cup is a tilt pour cup; electromagnetic pump; low pressure dosing fill system; interior surfaces of the top mold and the bottom mold have a pressure sensitive coating; the pour cup introduces the molten metal to the plurality of runners with a pour velocity of less than 100 cm/sec, preferably less than 50 cm/s; the plurality of slides is four slides; each slide is an insert that reciprocates along a respective channel; the pour cup introduces molten metal to the runners so that the molten metal flows into the mold quiescently without turbulence; and the applied pressure is between about 60 psi and about 3000 psi.
Accordingly, pursuant to another aspect of the present invention, an apparatus to form a metal structural component includes a first mold, a second mold, the first mold and the second mold being configured to receive molten metal, and a plurality of slides positioned within the top mold and the bottom mold. Positioning of the plurality of slides applies direct pressure on the molten metal in the top mold and the bottom mold to form a high quality metal cast component.
The foregoing aspect can be further characterized by one or any combination of the features described herein, such as: interior surfaces of the first mold and the second mold have a pressure sensitive coating; the plurality of slides is four slides; each slide is an insert that reciprocates along a respective channel; and the applied pressure is between about 60 psi and about 3000 psi.
Accordingly, pursuant to yet another aspect of the present invention, a method of casting a quality metal component includes one or more of the following steps: pouring molten metal into an interior cavity defined by a first mold and a second mold, and exerting pressure on the molten metal to form a quality metal component.
The method of casting a structural component may be further characterized by one or any combination of the following features: interior surfaces of the first mold and the second mold have a pressure sensitive coating; the molten metal pours into the interior cavity with a velocity of less than 100 cm/sec, preferably less than 50 cm/s; exerting pressure is produced by a plurality of slides positioned in the first mold and the second mold; the molten metal flows into the interior cavity quiescently without turbulence assisting in pushing existing air from mold cavity; the applied pressure is between about 60 psi and about 3000 psi; the slides move outwards along respective channels to accommodate an overfill volume, and the slides move inward to compensate for metal shrinkage as the molten metal transitions to a solid, while the positioning of the slides maintain the desired pressure on the solidifying casting; and the slides are configured to move to apply direct pressure to the molten metal as it solidifies, and pressure is applied and controlled with use of one or more pressure punches applied to regions of interest of the solidifying casting, the slides and the one or more pressure punches operating simultaneously or independently of each other.
Further features, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring now to the drawings, a direct squeeze system to cast structural components embodying the principles of the present invention is illustrated therein and designated at 10. Turning in particular to
Referring to
Turning to
In either system 10 or 100, the molten metal is poured into the respective system with a slow pour velocity. For example, in some arrangements, the pour velocity through the ingates 22 is less than 100 cm/sec, preferably less than 50 cm/s. In contrast, in high pressure die cast (HPDC) systems, the pour velocity exceeds 2000 cm/sec, and, in some arrangements, approaches 3800 cm/sec. A particular benefit of the low speed pour velocity for the systems 10 or 100 is the quiescent flow of the molten metal as it flows into the molds 16 and 18, which thereby reduces or eliminates turbulence in the flowing molten metal. In comparison to HPDC systems, the non-turbulent flow of the molten metal reduces the entrainment of air in the molten metal, which reduces the creation of structural voids in the structural component 30. In some arrangements, the surface of the interior cavity 28 is coated with a pressure sensitive coating, which enhances heat transfer and directional solidification, since the coating has a high thermal resistance with no pressure and low or no thermal resistance with high pressure. An example of such a coating is Trabo™ available from REL, Inc.
Generally, molten metal shrinks as it cools. For example, aluminum shrinks about 6% as it solidifies. Another feature of the systems 10 and 100, is the ability to compensate for the shrinkage of the molten metal as it cools and solidifies. Specifically, as shown in
Note also, that the positioning of the top mold 16 and the bottom mold 18 exerts or applies controlled direct pressure on the cooling molten metal as well. For example,
In sum, the mold cavity or interior region 28 is coated with a high thermal resistant-pressure activated coating. The molds 16 and 18 are closed and mechanically locked except for a direct pressure punch detail. Molten metal, such as, aluminum alloy quietly fills the mold cavity with approximately 10% overfill. The mold cavity is vented around the pressure punch or other locations. The direct pressure punch sequences shutting off the flow of molten metal through the downgate 14 and the ingates 22. The desired pressure is set and held until the cast component 30 solidifies. The molds 16 and 18 are opened and the mechanical component is removed.
In various arrangements, the direct squeeze pressure applied to the metal by the system 10 or 100 as it forms the component 30 can vary between about 60 psi to 3000 psi. It should be understood, that the inserts 32, 34, 36 and 38 arrangement can be modified for creating different component geometries. The pressure can be applied directly to a strategic region of the mechanical component 30, for example, the bulk head region of an engine block. As such, high integrity cylinder block castings can be heat treated to optimum tensile and fatigue strengths. Tensile and fatigue strengths of components produced with the system 10 or 100 can be at least double as compared to components produced with HPDC systems. Quiescent mold fill combined with low to medium squeeze pressure allows for the use of strong sand cores for internal passages and closed deck designs. Low to medium squeeze pressures can be used to drive molten metal infiltration of ceramic or metal reinforcement of local high stress regions of the component. Significantly lower casting pressures reduce tooling and press ruggedness requirements, which enables the use of simpler castings machines, hydraulic systems and controls compared to HPDC machinery. As such, simpler casting machines, hydraulics and controls and improved tool life lowers the cost per component compared to components made with HPDC systems.
The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
