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Method and apparatus for controlling dispersion of molten metal in a mold cavity

a technology of dispersion and mold cavity, which is applied in the direction of metal-working equipment, foundry patterns, mold molding apparatus, etc., can solve the problems of limited casting rate or rate at which molten metal enters the mold cavity, other areas to back-fill, and parts configuration which do not lend themselves to castingability, so as to minimize backfill and other casting defects, the effect of optimizing the material properties of the resulting casting

Inactive Publication Date: 2006-10-12
GM GLOBAL TECH OPERATIONS LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for controlling dispersion of molten metal in a mold cavity for a lost foam casting process. This invention maximizes the filling of regions of the mold cavity that do not lend themselves to castability, minimizes backfill and other casting defects, and optimizes the flow pattern of molten metal and material properties of the resulting casting. The apparatus includes a pattern die with a cylinder and a pattern forming cavity, a squeeze pin slidably disposed in the cylinder, and means for applying a force on the squeeze pin to cause it to move in the cylinder towards the pattern forming cavity, resulting in a localized densification of the pattern. The method involves providing a pattern with at least one locally densified portion, embedding the pattern in sand to form a mold cavity, and introducing molten metal into the mold cavity. The densified portion facilitates a diversion of the molten metal throughout the mold cavity upstream of the densified portion to promote a complete filling of the mold cavity.

Problems solved by technology

The casting rate or rate at which the molten metal enters the mold cavity is limited by the rate the advancing molten metal front can displace the pattern from the cavity.
Casting engineers are often challenged with a part configuration which does not lend itself to castability.
Features such as long straight rails cause metal to flow through a mold quickly while causing other areas to back-fill.
The back-fill areas can be subject to defects such as folds.

Method used

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  • Method and apparatus for controlling dispersion of molten metal in a mold cavity
  • Method and apparatus for controlling dispersion of molten metal in a mold cavity
  • Method and apparatus for controlling dispersion of molten metal in a mold cavity

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Embodiment Construction

[0021] The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the process disclosed and the flow diagrams illustrated, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical.

[0022]FIG. 1 depicts a lost foam pattern die 10 according to an embodiment of the invention. The die 10 includes a pattern forming cavity 12 formed therein. The cavity 12 has a shape substantially the same as a desired cast part (not shown). A cylinder 14 is formed in the die 10 and is in communication with the cavity 12. Cylinder as used herein is meant to mean a through-hole, cavity or other chamber adapted to have a sliding member disposed therein.

[0023] A squeeze pin 16 is slidably disposed in the cyl...

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Abstract

A method and apparatus for controlling the dispersion of molten metal in a mold cavity is disclosed, the control facilitated by a localized densification of foam in a lost foam casting operation for producing metal castings, wherein the filling of regions of the mold cavity which do not lend themselves to castability is maximized, an amount of backfill and casting defects are minimized, and a flow pattern of molten metal and material properties of the resulting casting are optimized.

Description

CROSS REFERENCE OF RELATED APPLICATION [0001] This is a Divisional of U.S. Ser. No. 11 / 100,049 filed Apr. 6, 2005.FIELD OF THE INVENTION [0002] The invention relates to lost foam casting and more particularly to a method and apparatus for controlling dispersion of molten metal in a mold cavity in a lost foam casting process for producing metal castings, wherein the control is facilitated by a localized densification of the foam. BACKGROUND OF THE INVENTION [0003] A so-called “lost-foam” casting process is a well-known technique for producing metal castings. A fugitive, pyrolizable, polymeric, foam pattern (including casting, gating, runners, and sprue) is covered with a thin (typically in the range of 0.25-0.5 mm), gas-permeable refractory coating / skin such as mica, silica, alumina, or alumina-silicate, for example. The pattern is embedded in compacted, unbonded sand to form a mold cavity within the sand. Molten metal is then introduced into the mold cavity to melt, pyrolyze, and di...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B22C7/02B22C9/04
CPCB22C7/023
Inventor WARD, GARY C.PRIEM, BARRY L.
Owner GM GLOBAL TECH OPERATIONS LLC
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