冷却工艺对超低碳贝氏体钢组织和性能的影响

Effect of cooling process on microstructure and properties of untra-low-carbon bainitic steel

采用热模拟试验和实验室轧钢试验,研究了超低碳贝氏体钢在冷却过程中冷却速率和终冷温度对微观组织和力学性能的影响。结果表明,在相同的冷却速率条件下,随着终冷温度的降低,试验钢的微观组织中板条贝氏体数量逐渐增加,但马奥岛体积分数减少,并且形状由长条状全部转变为球状。相同的终冷温度条件下,试验钢微观组织随着冷却速率的增加,粒状贝氏体组织略为变细,马奥岛尺寸减小、数量减少。轧钢试验中,随着冷却速率的提高和终冷温度的降低,试验钢的屈服强度、抗拉强度和屈强比都增加,但冲击韧性随着冷速的增加而明显改善,400～500℃范围内终冷对韧性影响不明显。

Effect of cooling rate and final cooling temperature on microstrueture and mechanical property in an untra-low-carbon bainitie steel was studied by using hot simulator and laboratory mill test. It is shown that with final cooling temperature reducing at the same cooling rate, the lathy bainite of the steel increases, the volume fraetion of M/A phase reduces and the shape changes from strip into spheroid. But in the same final cooling temperature, granular bainite became slightly finer, the dimension of M/A phase is diminished and the number is decreased with increasing cooling rate. In the steel rolling test, the higher the cooling rate and the lower the final cooling temperature, the higher the yield strength,the tensile strength, and the yielding-to-tensile ratio. The impact toughness of the steel obviously improves with cooling rate increasing,but it is uneonspicuous when the final cooling temperature is in 400 - 500 ℃.