氧化铝分解槽焊缝应力-碱脆开裂行为研究

拜耳法生产氧化铝分解槽焊缝及附近出现大批次开裂，利用扫描电子显微镜SEM、光学显微镜OM等手段分析裂纹形貌和金相组织，利用有限元等方法分析分解槽罐体受力情况，最后综合分析开裂失效行为机理。结果表明：厚壁焊缝自身产生纵向、横向和厚度方向三种残余应力，与罐体内部液体自重产生的应力叠加形成碱脆的多重应力环境。另外，潮湿的焊条在焊接时水蒸气在高温下产生气泡，气泡造成应力集中，作为裂纹源在碱应力促进下沿晶界和珠光体区域扩展（IGPSCC）形成最终裂纹，造成泄露。建立了多应力碱性环境下含气孔的厚壁容器焊缝应变诱发-阳极溶解导致IGPSCC模型，为研究长期运行后的拜耳法氧化铝分解槽焊缝应力-碱脆开裂行为提供借鉴。

Study on stress alkali embrittlement cracking behavior of welds in alumina decomposition tank

Cracks appear in and around a large batch of welds of alumina decomposition tank produced in production of alumina by Bayer process. The crack morphology and metallographic structure are analyzed by means of SEM and optical microscope, the stress of decomposition tank body is analyzed by means of finite element, and finally the failure mechanism is comprehensively analyzed. The results show that there are three residual stresses in the longitudinal, transverse and thickness directions of the thick wall weld, which are superimposed with the stresses generated by the liquid self weight in the tank to form an alkali brittle multiple stress environment. In addition, when wet electrodes are welded, water vapor produces bubbles at high temperature. As a crack source, bubbles expand along grain boundaries (IGPSCC) under the promotion of alkali stress to form final cracks, resulting in leakage. The IGPSCC model of multi stress thick wall weld with pores under strain anodic dissolution is established, which provides a reference for studying the stress alkali embrittlement cracking behavior of Bayer alumina decomposition tank after long-term operation.