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采用淬火变形膨胀仪测量高铬铸铁在不同冷却速度下的膨胀曲线,研究了加热温度和冷却速度对高铬铸铁热处理冷却过程中其微观组织转变的影响规律。结果表明,在较低冷速下微观组织为典型的亚共晶白口铸铁组织形态,由初生奥氏体的低温转变组织和共晶体组成;在冷却速度为3℃/s时开始出现马氏体组织,并优先在共晶奥氏体区域大量形成;随着冷却速度的增加,马氏体量逐步增多,在10℃/s冷速下为连续的马氏体基体组织和共晶碳化物。二次碳化物在初生奥氏体区大量弥散析出,而在共晶奥氏体区近共晶碳化物周边位置没有二次碳化物生成,远离共晶碳化物的区域有少量二次碳化物的析出。随着加热温度的升高和冷却速度的增加,初生奥氏体和共晶奥氏体区的珠光体片层间距均逐渐减小。
The quenching deformation dilatometer was used to measure the expansion curve of high chromium cast iron at different cooling rates. The influence of heating temperature and cooling rate on the microstructure of high chromium cast iron during cooling was investigated. The results show that the microstructure is typical hypoeutectic white cast iron microstructure at low cooling rate, consisting of low temperature transformation microstructure and eutectic of austenite; when the cooling rate is 3 ℃ / s, And preferentially formed in the eutectic austenite region. With the increase of cooling rate, the amount of martensite gradually increased and the martensite matrix structure and eutectic carbide were continuous at the cooling rate of 10 ℃ / s . The secondary carbides are precipitated in a large amount in the primary austenite region, whereas there is no secondary carbides in the vicinity of the eutectic carbide in the eutectic austenite region. A small amount of secondary carbides in the region away from the eutectic carbides Precipitation. With the increase of heating temperature and the increase of cooling rate, the spacing of pearlite sheets in both primary austenite and eutectic austenite decreases gradually.