고로슬러지 還元分鐵을 이용한 自動車 브레이크 摩擦材 開發

Abstract

Friction material is a very important element of disk brakes, because it is directly related to brake performance in such areas as effectiveness, friction stability with various brake conditions, pad life and different kinds of noise and vibration. Although friction material manufactures have worked to develop many different friction materials, very few studies have been published about the development of friction materials. Therefore knowledge of friction material development is not widespread. This paper covers the basic considerations, studies and experiments which focus on brake pad development using reduced iron of blast furnace sludge. Automotive brake materials must provide high and stable friction, low noise and vibration, and high wear resistance, under various braking conditions such as temperature, vehicle speed and braking pressure. To satisfy the above requirements, several different material ingredients are usually combined to form complex friction materials. When a friction material pad slides against gray cast iron rotor, the rotor and pad friction surfaces undergo physicochemical changes, and the so called transfer film is formed in the interface. In an attempt to examine the applicability of blast furnace dust to the friction materials, the dust itself(G1) or its reduced form of dust(G3) is partially substituted to the BaSO₄ used as a filler material. The BaSO₄ content of specimens G1 and G3 contents are varied as 10%, 20% and 30%, respectively, and using the brake dynamometer the manufactured pads are tested to assess the friction characteristics such as friction coefficient, noise, rotor compatibility, and wear resistance. After a fade test which is one of the severest friction tests, tested rotors are cut and polished to observe transfer film formation on the rotor surface by SEM(scanning Electronic Microscope), and the EDX(Energy Differential X-ray) analysis is followed to study the component variation through the film thickness. The results show that the friction coefficients of friction materials containing G1 or G3 decrease with the increase of G1 or G3 content, the tendency of which becomes more apparent as the vehicle speed and deceleration rates increase. The fade tests, for the specimens containing 30% of BaSO₄, G1, G3 respectively, show that the friction coefficients surprisingly increase after 5 cycles of the test, which is termed 'anti-fade phenomenon' in this study. In the friction materials containing BaSO₄ as a filler material, the transfer film is found to be well developed, while in those which contain G1 the transfer film is very poorly developed. The thickness of the transfer film decreases with increase of deceleration rates, which implies the thicker film thickness, the higher friction coefficients. The components of the transfer film are similar to those of the respective filler materials, and the Fe content in the film for G1 and G3 materials is higher than the conventional friction materials containing BaSO₄. Compared to the conventional friction materials, the wear resistance, rotor compatibility, and noise characteristics have greatly improved with the use of G1 or G3 as a filler material.