中厚板探伤不合原因分析

利用扫描电镜、能谱仪以及金相显微镜对探伤不合钢板的拉伸断口形貌、夹杂物和显微组织进行观察和分析,研究钢板探伤不合格的原因。结果表明:钢板中心存在氧化物、钙铝酸盐、保护渣、硫化物夹杂,C、Mn偏析严重,且有贝氏体带状组织,在热应力和组织应力的联合作用下引起内部裂纹,导致钢板探伤不合格。为此,提出了加强保护浇注、优化结晶器流场和二冷段弱冷等工艺措施,提高了探伤合格率。

Investigation on the Causes of Non-Conformity in Ultrasonic Flaw Detection of Heavy Steel Plate

The tensile fracture morphology,inclusions and microstructure of the nonconforming steel plate in ultrasonic flaw detection are observed and analyzed by means of SEM,EDS and metallographic microscopes to study causes of the nonconforming steel plate in ultrasonic flaw detection.The results show that the nonconformity of steel plate in ultrasonic flaw detection is caused by the internal cracking due to the oxides,calcium-aluminates,synthetic slag,sulphide inclusion,C and Mn segregation and banded bainite in the center of steel plate under the joint actions of thermal stress and structural stress.Thus many technological measures of enhancing shielded pouring,optimizing mould flow field and soft cooling at secondary cooling zones are raised and the conformity rate of ultrasonic detection is improved.