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一、引言某铝厂采用贝尔法生产Al_2O_3,使用850m~2。外加热式蒸发器,该蒸发器用低碳钢制成,使用在浓度为13～30％NaGH溶液中,24小时连续作业。蒸发器使用后约半年出现明显的碱液渗漏,采用局部补补丁和在裂缝处开坡口重新焊补两种办法修复,经修补后一个月又出现渗漏,再修补渗漏的更快些。约一年蒸发器循环管就报废了,给生产造成很大损失,为此我们分析了断裂原因。二、实验及分析 1.取样从蒸发器裂纹处取四块典型裂纹试件作为粗型观察用。1号和2号试样用于显微镜观察。1号样取自贴补后的焊缝处(图1c),2号样取自蒸发器原始焊缝的裂纹处(图1a,b)。 2.试验 2.1粗型观察:四块典型裂纹试件都可看见大小不等的多个裂纹,而全部裂纹皆产
I. INTRODUCTION Aluminum plant produces Al_2O_3 by Bell method, and uses 850m ~ 2. External heating evaporator, the evaporator made of low carbon steel, used in the concentration of 13 ~ 30% NaGH solution, continuous operation 24 hours. About half a year after the use of the evaporator, significant leakage of caustic soda occurred. Local patches and repaired welds at the crevices of the crevices were used to repair the repairs. One month after the repairs, leakage occurred and the leakage was repaired more quickly some. About a year evaporator circulation tube scrapped, resulting in great loss of production, for which reason we analyzed the fracture. Second, the experiment and analysis 1. Sampling from the evaporator to take four pieces of typical crack specimens as crude observation. Samples No. 1 and No. 2 were used for microscopic observation. Sample No. 1 was taken from the welds (Figure 1c) after patchwork, Sample No. 2 was taken from the crack at the original weld of the evaporator (Figure 1a, b). 2. Test 2.1 rough observation: four typical crack specimens can see multiple cracks of varying sizes, and all cracks are produced