In order to observe the different position of lower bainite, martensite nucleation and formation characteristics of residual time and position of the bright region, the following experiment do Shenzhen sushi heat treatment at 860 ℃, selection of austenitic 1h after oil quenching of 5-6s, the oil temperature is 300-400 ℃, can be seen around the undercooled austenite, graphite first of all, the inference should be lower bainite. And along the direction of flake graphite tip distance of supercooled austenite transformation is preferred. In addition, stable white area is also formed at this time, lower bainite ring body of certain thickness is formed around the.
Experiments show that, the martensite / bainite duplex microstructure of grey cast iron is characterized by lower bainite ferrite in near graphite nucleation and growth. From the analysis of the transformation kinetics, the uneven distribution of elements in the gray cast iron, graphite around the carbon depleted silicon rich, Si can reduce the gamma region and accelerate the decomposition of austenite in the cold, for bainite nucleation.
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