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Title: Predicting Pattern Tooling and Casting Dimensions for Investment Casting, Phase II

The investment casting process allows the production of complex-shape parts and close dimensional tolerances. One of the most important phases in the investment casting process is the design of the pattern die. Pattern dies are used to create wax patterns by injecting wax into dies. The first part of the project involved preparation of reports on the state of the art at that time for all the areas under consideration (die-wax, wax-shell, and shell-alloy). The primary R&D focus during Phase I was on the wax material since the least was known about it. The main R&D accomplishments during this phase were determination of procedures for obtaining the thermal conductivity and viscoelastic properties of an unfilled wax and validating those procedures. Phase II focused on die-wax and shell-alloy systems. A wax material model was developed based on results obtained during the previous R&D phase, and a die-wax model was successfully incorporated into and used in commercial computer programs. Current computer simulation programs have complementary features. A viscoelastic module was available in ABAQUS but unavailable in ProCAST, while the mold-filling module was available in ProCAST but unavailable in ABAQUS. Thus, the numerical simulation results were only in good qualitative agreement with experimentalmore » results, the predicted shrinkage factors being approximately 2.5 times larger than those measured. Significant progress was made, and results showed that the testing and modeling of wax material had great potential for industrial applications. Additional R&D focus was placed on one shell-alloy system. The fused-silica shell mold and A356 aluminum alloy were considered. The experimental part of the program was conducted at ORNL and commercial foundries, where wax patterns were injected, molds were invested, and alloys were poured. It was very important to obtain accurate temperature data from actual castings, and significant effort was made to obtain temperature profiles in the shell mold. A model for thermal radiation within the shell mold was developed, and the thermal model was successfully validated using ProCAST. Since the fused silica shells had the lowest thermal expansion properties in the industry, the dewaxing phase, including the coupling between wax-shell systems, was neglected. The prefiring of the empty shell mold was considered in the model, and the shell mold was limited to a pure elastic material. The alloy dimensions were obtained from numerical simulations only with coupled shell-alloy systems. The alloy dimensions were in excellent quantitative agreement with experimental data, validating the deformation module. For actual parts, however, the creep properties of the shell molds must also be obtained, modeled, and validated.« less
 [1] ;  [2]
  1. (EMTEC)
  2. (ORNL)
Publication Date:
OSTI Identifier:
Report Number(s):
DE-FC36-01ID14033; TRN: US200707%%251
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
Edison Materials Technology Center (EMTEC)
Sponsoring Org:
USDOE - Energy Information Administration (EI); USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
36 MATERIALS SCIENCE; 42 ENGINEERING; ALLOYS; ALUMINIUM; CASTING; COMPUTER CODES; COMPUTERIZED SIMULATION; CREEP; DEFORMATION; DEWAXING; DIMENSIONS; FOUNDRIES; SHRINKAGE; SILICA; TESTING; THERMAL CONDUCTIVITY; THERMAL EXPANSION; THERMAL RADIATION; dimensions, investment casting processes, computer simulations, wax, viscoelastic, thermal rediation, thrmophysical properties, stress during solidification.