9Ni钢T&T焊接工艺低温韧性

Low-temperature fracture toughness of welded joints for TOP-TIG welding on 9Ni steel

关键词:  钨极保护焊  低温储罐钢  低温韧性

Key words:  tungsten inert gas welding  liquefied nature gas  low temperature toughness

摘要:

依据AWS D1.1M-2010,ISO 15653:2010对液化天然气(LNG)低温储罐钢9Ni钢TOP-TIG(T&T)焊接接头进行了夏比冲击韧性试验和断裂韧性(CTOD)试验. 另外对接头进行组织、XRD及断口分析，研究了9Ni钢T&T焊接接头低温韧性性能. 结果表明，T&T焊接接头冲击吸收功远高于标准要求，冲击韧性很好；热影响区组织主要为板条马氏体，位错密度高，断口韧窝浅而小，呈准解理断裂，焊缝区CTOD值较高，组织主要为奥氏体树枝状结构和等轴晶，断口含有大量韧窝，断裂韧性好. 9Ni钢T&T焊接接头-196 ℃低温韧性好，可以满足相关工程标准的要求.

Abstract:

According to AWS D1.1M-2010 and ISO 15653:2010, the crack tip opening displacement (CTOD) test and the Charpy impact test of TOP-TIG welded joints made by 9Ni steel using in liquefied nature gas (LNG) had been conducted. The microstructure, X-ray diffractometry and fracture surface were performed to study the low-temperature toughness of welded joints for TOP-TIP welding on 9Ni steel. The results revealed that the impact toughness of the welded joints was very good and much higher than the standard requirements; The CTOD characteristic values were higher. The microstructure of HAZ was mainly consisted of lath martensite with more dislocation. The fracture surface of HAZ showed quasi-cleavage fracture with shallow and small dimple. The microstructure of the welded seam comprised of austenite dendritic structure and other equiaxed crystal had excellent fracture toughness which with a significant number of dimple fracture surface. The low temperature toughness of welded joints for TOP-TIG welding on 9 Ni steel was good enough to reach the engineering requirements.