|dc.description.abstract||In this study, we focus on the influence of three pouring temperature(1423°C、1398°C and 1368°C) and two casting projects. First, we have the measurement of natural frequency on the brake disc. Second, we have the suitable samples be polished and pictured by the optical microscopes. After that, let samples have friction and wear test on a Ball-on-disc test machine. At the last, we have to observe the different wear surface of different casting samples.
From the test of natural frequency and picture of microstructure, we get the relation between them. When the content of Type C graphite increase in the matrix of gray iron, the value of natural frequency will decrease. The higher the pouring temperature and the closer to the in-gate of the molten iron, having the slower solidification rate and will form larger flake graphite or lump graphite. Besides, because of the lower solidification, matrix of gray iron tends to form ferrite and coarse pearlite near the larger or lump graphite.
At the beginning of friction, graphite will be smeared onto the wear surface and form graphite layer protect surface form directly friction and serve as lubrication. Unfortunately, with the leave of graphite or soften matrix near graphite, such as ferrite and coarse pearlite, ease to transform or peel off and cause cavities on the wear surface. Meanwhile, the fragment will have abrasive wear on the surface. With the constant friction, the surface of brake disc will form bigger cavities and crack. For the performance、vibration and noise of brake system, it will cause harmful influence.||en_US|