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针对低合金中厚板超声波探伤合格率低的问题,采用低倍、金相、扫描电镜检验和断口形貌分析对探伤不合格的中厚板进行研究,得出结论:引起超声波探伤不合格的主要原因是钢中的氢含量偏高和板坯中心偏析严重,条状MnS夹杂物集聚氢导致氢致裂纹,板材中心部位因偏析产生的少量马氏体、贝氏体组织导致轧后应力集中,在冷却速度较快的条件下产生微裂纹,最终造成探伤缺陷。通过计算得知MnS夹杂物前端的氢陷阱中氢的浓度远高于陷阱中氢的最大饱和浓度,过剩的氢造成裂纹。采用铸坯及板材轧后缓冷等措施,使板材探伤合格率大幅度提高。
Aiming at the problem of low pass rate of low-alloy plate in ultrasonic testing, using low magnification, metallographic examination, scanning electron microscopy and fracture surface morphology analysis on the unqualified medium and heavy plate, concluded that ultrasonic flaw detection failed The main reason is that the hydrogen content in steel is high and segregation of slab center is serious. The accumulation of hydrogen in strip-shaped MnS inclusions leads to hydrogen-induced cracking, a small amount of martensite due to segregation in the central part of the slab and the stress concentration in bainite after rolling , Resulting in microcracks under faster cooling conditions, resulting in flaw detection. It is calculated that the concentration of hydrogen in the hydrogen traps at the front end of the MnS inclusions is much higher than the maximum saturation concentration of hydrogen in the trap and the excess hydrogen causes cracks. Adopting measures such as slab and slab slow rolling, so that the passing rate of plate testing greatly improves.