Q345B稀土铸钢在第三类脆性塑性谷底区组织变化规律的研究

Microstructure Change Law on Rare Earth Cast Steel Q345B in Third Class Brittle Plastic Bottom Area

以含稀土Ce的Q345B连铸钢坯为研究对象，采用Gleeble-1500D热模拟试验机模拟第三类脆性区，研究实验钢的最低塑形谷底。结果表明：含稀土Ce的Q345B钢，随拉伸温度的升高，抗拉强度降低。含0．0091％Ce的Q345B钢在第三类脆性温度区（600-900℃），在800℃出现塑形谷底。经金相显微组织分析，奥氏体晶界上薄膜状先共析铁素体不是造成热塑性较差的主要原因。

Q345B continuous casting billets containing rare earth Ce was used to research the lowest plastic bottom of experiment steels, and the third brittle zone was simulated by using Gleeble 1500-D thermal simulation machine. The results show that as the stretching temperature increasing, the high temperature mechanical properties of Q345B steel with rare earth Ce increase accordingly, the tensile strength of the sample decreases. When the temperature reaches the third class brittle plastic area （600℃-900℃）, especially at 800℃, Q345B steel with 0.0091% generates the plastic bottom. The analysis of the microstructure find that the film shape pro-eutectoid ferrite on the grain boundary of austenitic is not the main reason for poor thermoplasticity.