摘要
采用金相显微镜和扫描电子显微镜对厚规格X80管线钢微观组织和-25℃落锤撕裂试验断口形貌进行观察,研究了X80管线钢的断裂行为与组织之间的关系。研究发现,钢板从表面到厚度中心,针状铁素体体积分数逐渐降低,并出现较多的粒状贝氏体、多边形和准多边形铁素体。具有较高针状铁素体体积分数的钢板,其落锤撕裂剪切面积也越高,多边形和准多边形铁素体以及大尺寸MA岛的存在能够导致解理断裂的产生,不利于钢板的低温断裂韧性。在裂纹扩展的过程中,主裂纹附近组织出现变形,导致脆硬性的MA岛周围出现微孔,微孔与微孔之间随着组织变形相互连接而形成微裂纹。二次裂纹通常在针状铁素体周围出现转折或停滞,说明针状铁素体有利于阻碍裂纹的扩展,提高钢板的断裂韧性。
The effect of microstructure on tearing fracture behavior for thick plates of X80 pipeline steel was assessed at -25 oC by means of drop-weight tear tester（DWTT）,as well as optical microscopy and scan electron microscopy（SEM）. The result shows that the volume fraction of acicular ferrite reduced gradually in the thickness direction and reached a minimum level at the center of the plate, whilst more volume fraction of granular bainite（GB）, polygonal-like ferrite（PF） and quasi-polygonal-like ferrite（QF） appeared. The higher volume fraction of acicular ferrite of the plate is, the larger tearing share area will be. In addition, the existence of PF and QF, and large size martensite-austenite（MA） could lead to the initiation of cleavage crack, and reduce the fracture toughness of the plate. During the crack propagation process, microstructures near the main crack deformed and elongated seriously, but the hard and brittle MA can hardly deform, resulting in the growth of voids and formation of micro cracks. The secondary crack is always reflected by or arrested on acicular ferrite boundaries, which demonstrates that the acicular ferrite has good toughness, and thereby retards the crack propagation effectively.
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2018年第1期33-41,共9页
Chinese Journal of Materials Research
关键词
金属材料
管线钢
X80
落锤撕裂试验
断裂行为
组织
metallic materials, pipeline steel, X80, drop-weight tear test, fracture behavior, micro-structure
