HT250灰铸铁干熄炉风帽断裂原因分析

Cause analysis on fracture of gray cast iron HT250 vent-cap of CDQ unit

为了考察HT250灰铸铁干熄炉风帽在使用过程中发生断裂的原因,分别利用化学分析法、光学显微镜和布氏硬度计,对断裂后风帽材料的化学成分、微观组织和布氏硬度(HBW)进行了分析、观察和测定,并根据布氏硬度值计算材料的抗拉强度。结果表明,风帽材料中的铁素体含量高于HT250灰铸铁件的要求上限,在风帽非工作面附近的基体组织中,铁素体含量达50%以上;铁素体含量过高导致HT250灰铸铁风帽材料的抗拉强度低于正常,是造成风帽断裂的主要原因。

In order to investigate the reason for the fracture of gray cast iron HT250 vent-cap of CDQ （Coke Dry Quenching） unit in service, the chemical composition, microstructure and Brinell hardness （HBW） of vent-cap material after fracture were analyzed by chemical analysis, optical microscope and Brinell hardness tester. And then the tensile strength of vent-cap material was calculated by Brinell hardness. The results indicate that the ferrite amount in vent-cap material is higher than the upper limit requirement of HT250 castings, which even reach over 50% in the matrix microstructure near the non-working surface of vent-cap. It is the main reason for the fracture of vent-cap that excessive ferrite amount leads to tensile strength of HT250 vent-cap material lower than the normal range.