Influence of Heat Treatment Process on the Structures and Properties of Grate Bars Used in Sintering Trolley
The as-cast structure of grate bar used in sintering trolley is primarily comprised of austenite and eutectic (eutectic austenite and eutectic carbide). The austenite is dendrite, while the carbide is reticular and chrysanthemum-like. The grate bars were quenched and tempered under various temperature (one set of samples: quenching (975~1050°C); the other: quenching (1000°C) + tempering (240~600°C)). With rise in quenching temperature, the content of martensite increases and gradually stabilizes, and the hardness increases and then decreases (the maximum is 61.5HRC). For the tempered simple, the strip-like carbides gradually become smaller, shorter and homogenized; the resistance to temper softening is high and the maximum hardness is 58HRC; the wear resistance gradually decreases and is lower than that of as-cast one when the temperature is higher than 480°C. The heat treatment process to improve the service properties of grate bars is: quenching (1000°C, 2.5h, and air-cooling) + tempering (300~420°C, 2.5h, and air-cooling).