热轧中厚板探伤合格率低的成因研究

Research on Causes of Low Disqualification of Hot-rolled Q235B Heavy and Medium Plate by Ultrasonic Detection

针对某钢厂生产的Q235B热轧中厚板探伤合格率低的问题,采用光学显微镜和扫描电镜对钢板探伤不合格部位进行了观察与分析。结果表明,导致探伤不合格的主要原因是组织中存在以点状密集形和长条状为主的MnS、Al2O3或氧化物和硅酸盐夹杂,尤其是钢板组织中存在大量长度达300μm的狭长条带状MnS夹杂物,条带区域与基体结合疏松,有大量显微空隙与显微裂纹。

Aiming at the low disqualification problem of the hot-rolled Q235B heavy and medium plate by ultrasonic detection,the microstructure and the inclusions of the detection unqualified positions in the hot-rolled Q235B plate were investigated and analyzed by optical microscopy and scanning electron microscope.The results show that the main reason is that there exist the pointlike intensive and the long-stripe-like inclusions,such as MnS,Al2O3 or oxide and silicate.Especially a large number of the elongated band MnS exist in the microstructure of the steel plate whose size reaches 300 μm.The combination between the strip area and the base is loose with a great quantity of the microscopic gaps and microscopic cracks.