Evaluation of aluminum die casting defects causing casting rejection during machining
Abstract (Summary)The die casting process is an effective near net shape manufacturing process for producing geometrically complex components which require a high production rate and an excellent surface finish. However, one problem area has been indicated that die castings are often rejected by die casters as a result of being machined, and the defects for causing the rejections are frequently not clearly defined. The main objectives of this research project were: (1) to collect defective castings which were rejected as a result of being machined, (2) to collect and summarize scrap percentage data associated with these machining related rejects, and (3) to perform metallurgical analyses to determine the exact nature of the defects causing those rejections. Twenty four subject castings and the corresponding scrap percentages were collected from sixteen die casting companies in the North American die casting industry. Four reasons for rejection were classified; visual imperfection on machined surface, casting failed pressurized leak test, casting breakage during machining, and low tool life with excessive surface roughness. Also, the common defects found in these defective castings were categorized as follows: (1) porosity, (2) cold laps, (3) flow lines, (4) aluminum oxide inclusions, (5) lubricant or mold coating inclusions, and (6) mechanical cracks. This thesis summarizes what has been written about casting defects in the literature, and reports scrap records supplied by the contemporary die casting industry (1996) related to machining related defects. Also, the results of metallurgical evaluations of the defects found in twenty four defective die castings are reported. Photomicrographs showing examples of these defects are also included in this thesis.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/1997