According to the characteristics of grey cast iron brake discs produced by electric furnace, three kinds of HT200 molten iron with basically the same chemical composition and different w (TI) content (as shown in Table 1) are designed, and the brake discs of the same model are poured. C. S element is detected by leco-cs744 carbon sulfur analyzer, and other elements are detected by SPECTROMAXx spectrum analyzer. Test process: 6 tons of molten iron in the electric furnace are prepared according to the chemical composition of scheme a, and the first package is poured according to scheme a (the mass is 1 T); Then, FETI with 25% w (TI) is added into the furnace to increase the amount of W (TI) in the furnace to 0.03%; The second ladle molten iron pouring scheme B (mass: 1 T); Add FETI with 25% w (TI) into the electric furnace again, increase the amount of molten iron w (TI) in the furnace to 0.12%, and come up with the second ladle of molten iron pouring scheme C (mass is 1 T). Finally, the remaining molten iron in the electric furnace is evenly distributed to other furnaces and re charged for melting.
All test molten iron are poured into the same type of brake disc. The sampling and testing positions of Brinell hardness and tensile strength on the disc body are shown in Figure (a). The metallographic testing sample blocks cut on the brake disc are shown in Figure (b). Only three positions on the comparison sample blocks are numbered ①, ② and ③ respectively.
Take the final finished disc to detect the metallographic structure, use Zeiss metallographic microscope to detect the graphite morphology in the polished state, use 2% nitric acid alcohol solution to observe the matrix structure after corrosion, and prepare eutectic test samples according to gb/t7216-2009 metallographic examination of grey cast iron. All observation points are located in the middle of the sample section of the brake disc.
Observe the turning / grinding process, find and record the machining differences of different w (TI) quantity schemes.