Porosity Effect Analysis on The Dimension of Cast Pinion Gear, Drive Disc and Head Stock Components of Manganese Steel
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Date
2016-07
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Addis Ababa University
Abstract
Production of parts by casting operation involves various processes which include pattern making, mold preparation, core making, melting and pouring, removal of the cast from the mold, cleaning, finishing and inspection. Defects in castings may occur during these processes due to some reasons. This study has been carried out mainly on porosity defects of manganese steel castings.
Porosity is one of the main challenges in steel castings at Akaki Basic Metals Industry. The problem occurs on the 4784kg of pinion gear, 900kg of drive disc and 4538 kg of headstock components of manganese steel castings. For the purpose of avoiding pores and cavities, large amount of material is removed from the surface of the steel castings by machining and grinding operations. This leads to rejection of the products due to unsatisfactory design requirements, or assembling defective components shortens the service life of the product for its intended purpose. The method used in the study includes physical observations, photographic analysis and experimental analysis by taking measurement of depth of pores and cavities. Data was gathered from both primary and secondary sources. The result of the experiment was analyzed using control charts and Ishikawa (cause and effect) diagram. Depending on the analysis results, interpretation was made and the root causes of porosity were identified and remedial actions required to improve the quality of steel castings with regard to the selected defective components are presented. Mold preparation problems, molding material property, pouring temperature and time, poor gating system design, inappropriate material composition and improper utilization of reclaimed sand are the main causes for porosity.
Experimental analysis implies that the maximum pore depths on the drive disc, pinion gear and headstock components are found as 24mm, 23mm and 24mm respectively. Removing these amounts of material from the finished surfaces highly reduces the desired dimensions of the parts. So the quality level of the components is taken as a reject due to unsatisfactory design requirements and the rework cost is high; 25,821.50 USD. Better combination of the process parameters like sand binder ratio, grain fineness number, mold permeability, proper gating system design, pouring temperature and time are the leading parameters to reduce the casting defects.
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Keywords
Cast Pinion Gear, Manganese Steel, Porosity Effect Analysis