학술논문
水冷壁管环焊缝开裂原因分析 / Cracking analysis of circumferential weld for water wall pipe
Document Type
Academic Journal
Author
Source
焊接 / Welding & Joining. (1):60-80
Subject
Language
Chinese
ISSN
1001-1382
Abstract
文中利用宏观形貌及金相组织观察、化学成分检测、硬度测试等方法对水冷壁管开裂原因及机理进行了研究分析.结果表明,水冷壁管启裂于对接环焊缝与鳍片纵焊缝交叉处,该部位焊接残余应力及弯曲约束力程度较高且基体为不完全相变组织的;加之,环焊缝的基体组织中还存在因焊接工艺不合格或操作不当产生的夹渣和气孔等焊接缺陷.在机组启停或热负荷变化较大时产生的交变应力、焊接残余应力及弯曲约束力的共同作用下,裂纹逐渐于水冷壁管对接环焊缝与鳍片纵焊缝交叉处萌生并不断向内壁延伸,而焊接缺陷的存在又进一步加速了裂纹的扩展,最终导致水冷壁管发生开裂泄漏.
In this paper,cracking cause and mechanism of the water wall tube were investigated and analyzed by means of macroscopic morphology and metallographic observations,chemical composition detection and hardness testing.The results reveal that the cracking of the water wall tube is initiated from the intersection of the butt circumferential and fin longitudinal welds with high welding residual and bending restraint stresses composed of incomplete phase transformation structures.In addition,welding defects such as slag inclusions and pores in the matrix structure of circumferential weld due to unqualified process or improper operation are also found.Under the joint actions of alternating stress formed when the unit is started,stopped or heat load changed,welding residual stress and bending restraint force,crack is gradually formed and extended at the intersection of the butt circumferential weld of the water wall pipe and the longitudinal weld of fin.And finally,the cracking of the water wall pipe is caused with the accelerating expansion of the preexisting welding defects.
In this paper,cracking cause and mechanism of the water wall tube were investigated and analyzed by means of macroscopic morphology and metallographic observations,chemical composition detection and hardness testing.The results reveal that the cracking of the water wall tube is initiated from the intersection of the butt circumferential and fin longitudinal welds with high welding residual and bending restraint stresses composed of incomplete phase transformation structures.In addition,welding defects such as slag inclusions and pores in the matrix structure of circumferential weld due to unqualified process or improper operation are also found.Under the joint actions of alternating stress formed when the unit is started,stopped or heat load changed,welding residual stress and bending restraint force,crack is gradually formed and extended at the intersection of the butt circumferential weld of the water wall pipe and the longitudinal weld of fin.And finally,the cracking of the water wall pipe is caused with the accelerating expansion of the preexisting welding defects.