摘要
采用OM、SEM、TEM、EBSD、拉伸和冲击等分析和检测技术,研究了工业生产的117 mm厚Ni-Cr-Mo-B超厚钢板在厚度方向上微观组织的变化及其对力学性能的影响。结果表明,从表层到芯部,超厚板的屈服强度逐渐降低,表层和芯部的屈服强度分别为798和718 MPa;延伸率变化不大,为20.0%~22.0%;然而超厚板的-60℃冲击功变化较大,其中表层、1/8T(T代表板厚)和芯部的冲击功分别为35、160和20 J,使得整个厚度方向上的冲击功变化曲线呈现"M"型。从表层到芯部,超厚板的板条宽度(198.7~500.6 nm)、界面碳化物尺寸(130.6~226.6 nm)和晶内碳化物尺寸(45.8~106.2 nm)均逐渐增加,芯部还存在一定的块状区,板条的细晶强化和碳化物的析出强化效果均减小,使得屈服强度从表层到芯部逐渐降低。从表层到芯部,有效晶粒尺寸先减小后增加,表层(2.2μm)和芯部(2.7μm)的有效晶粒尺寸较大,对解理裂纹扩展的阻碍作用较弱,使得表层和芯部的冲击功较低;而1/8T位置具有较小的有效晶粒尺寸(1.7μm),对解理裂纹的阻碍作用较强,从而获得较高的冲击功。
With the increasing demand and exploitation depth for offshore oil and gas, offshore platforms are becoming larger and the performance requirements and size for offshore platform of ultra-heavy plates are also increasing. Due to the large plate thickness and the limitation of manufacturing techniques, inhomogeneous microstructures and mechanical properties along thickness direction are great challenges for offshore platform of ultra-heavy plates. In this work, variation of microstructure and its effect on mechanical properties for the 117 mm-thick Ni-Cr-Mo-B industrial ultra-heavy plate were investigated by means of OM, SEM, TEM and EBSD observation, in combination with the tensile and impact toughness test. The results show that yield strength reduces gradually from the surface(798 MPa)to the center(718 MPa) and elongation almost keeps constant around 20.0%~22.0% for the 117 mm-thick plate. It is noted that impact energy at-60 ℃ increases first from 35 J at the surface and reaches its peak 160 J at the depth of 1/8 T(T—thickness of plate), and then drops to the minimum about 20 J at the center, which suggests that impact energy curve along the whole section varies sharply and exhibits like letter ’M’. Lath width, boundary carbide size and intragranular carbide size are all gradually increasing from the surface to the center, i. e., from 198.7 nm to 500.6 nm, 130.6 nm to 226.6 nm, 45.8 nm to 106.2 nm, respectively, and there are also some blocky areas at the center, all those indicate that refinement strengthening and precipitation strengthening would decrease, as well as the gradual decrease of yield strength. Also, from the surface to the center, effective grain size(EGS) decreases first and then increases. The surface and the center have larger EGS(2.2 μm and 2.7 μm, respectively), which indicates that they have weaker resistance to cleavage crack and exhibit lower impact energy. However, the 1/8 T position has smaller EGS(1.7 μm) while obtains higher impact energy.
作者
张守清
胡小锋
杜瑜宾
姜海昌
庞辉勇
戎利建
ZHANG Shouqing;HU Xiaofeng;DU Yubin;JIANG Haichang;PANG Huiyong;RONG Lijian(CASKey Laboratory of Nuclear Materials and Safety Assessment,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China;Wuyang Iron and Steel Co.Ltd.,Pingdingshan 462500,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第9期1227-1238,共12页
Acta Metallurgica Sinica
基金
国家重点研发计划项目No.2016YFB0300601
辽宁省"兴辽英才计划"项目No.XLYC1907143
兵团重大科技项目No.2017AA004-2。
