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The Effect of Chemical Composition and Cast Iron Structure on the Frictional and Abrasive Properties of the Brake Disc

Salavaty, Abdollah | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52046 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Varahram, Naser; tavakoli, Rohollah
  7. Abstract:
  8. One of the most important factors affecting the performance of the vehicle's brake disc is its stiffening coefficient. To improve this feature, many researches have been carried out by leading automotive companies, whose scientific aspects have not yet been widely disseminated. Brake discs are often made of cast iron and are more likely to produce gray iron with type A graphite. However, according to available resources, factors such as graphite morphology, their length-to-thickness ratios, cast iron and heat treatment on the piece affect this important feature. One of the most important factors that make changes in the above mentioned cases is the chemical composition and freezing rate. In this study, the effect of the above factors on the frictional properties of castings with different graphite morphologies, such as compact, gray and spheroid graphed, was investigated. Another important factor is the increase of abrasion resistance to increase longevity, this goal is often contrasted with increasing friction coefficient. Therefore, in this research, we tried to reach the optimal balance point between these two important properties. After that, gray cast iron was used to obtain the type A graphite from furosilcium. The use of magnesium was used to cast the ductile iron. The use of magnesium in the molding was used for unbreakable cast casting. In order to obtain pig iron with compressed graphite, in addition to reducing the magnesium content, titanium was used to obtain compressed graphite. Due to the limited frequency of melting and science, the positive effect of phosphorus on the abrasive properties was achieved using a percentage of phosphorus. Therefore, in order to see the results, we first performed a quantummetery and metallurgical identification of cast iron, and then the friction coefficient and abrasion rate were determined by the test of wear on the disk pin. In addition to the above tests, the hardness test was also performed and then the sum of these results and properties were discussed. The results showed that the ratio of length to width of graphites had a significant effect on the wear rate and friction coefficient of castings. In fact, by increasing the surface ratio of the graphite, the coefficient of friction increases and the abrasion resistance decreases. The hardness of the samples is also reduced. It should be noted that the field of all cast alloys was perlite. Phosphorus also increases the wear resistance by forming a rich phosphorus compound, which in turn is a hard phase. At the end, as a result of the project results, cast iron with a compact graphite and a high percentage of phosphorus has a good balance between the wear rate and the coefficient of friction in comparison to the ductile iron and gray iron. In fact, gray cast iron has a high friction coefficient and abrasion resistance. Ductile iron has less coefficient of friction and also has a high abrasion resistance; however, high-phosphorus high density graphite has an optimum point for these properties. It is therefore suitable for the production of brake discs for passenger cars
  9. Keywords:
  10. Gray Cast Iron ; Cast Iron with Phosphor Compression Graphite ; Morphology ; Friction Coefficient ; Adhesive Wear

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