尿素合成塔外层板裂纹成因分析

Cause Analysis of Cracks on Outer Laminates of Urea Reactor

通过对尿素合成塔外壁带有裂纹的层板试样进行宏观检查、金相组织分析、断口扫描电镜分析、化学成分分析、力学性能测试、硬度及厚度的测定,并结合外层板材料分析、层板间的应力分析以及尿塔工作介质的分析,最终可得出:外层板出现多处裂纹是由于有较大拉伸应力的低合金钢外层板在空气与雨水中的氨、保温层中的Na+、K+、S2-以及漏入检漏蒸汽中的Na+、K+等腐蚀性物质共同作用下发生应力腐蚀造成的。

The macroscopic inspection,metallurgical structure,SEM observation on fracture surface,chemical composition,mechanical properties,hardness and thickness of laminate with cracks on the outerwall of urea reactor were measured.Combining with the analysis of outerwall material,stress among laminates,working medium of urea reactor,such many cracks on outer laminate of urea reactor were due to the stress corrosion of lean alloy steel outer laminate with larger tensile stress under the ammonia in the air and rain,Na ＋,K＋ and S2-in the insulating layer,Na＋,K＋ and other corrosive substances leakage into the leak detection steam.