通过SEM和示波冲击试验研究了特厚压力容器用钢板的0、-20、-40℃的冲击韧性及显微组织。结果表明：降低试验温度，t/4和t/2处的E1变化不大，Pm、E2、E3+E4和（Pm-Pf）值减小，脆性断裂趋势增大，脆性断裂止裂变差；t/4处抑制裂纹形成和阻止脆性断裂的能力优于t/2处。t/4处的-20℃冲击断口纤维区由细小韧窝组成，t/2处呈现为准解理断裂形貌。t/2处放射区中河流花样和撕裂棱数量较t/4处增多。同一个珠光体团内部呈现出LP和DP两种形态。t/2处LP片层间距较t/4处增大，DP有所增加。%The impact toughness at 0 ℃,-20 ℃ and-40 ℃ and the microstructure of ultra heavy plate for pressure vessel were investigated by means of SEM and instrumented impact test. Experimental results showed that the test temperature have a great influence on impact toughness of the t/4 and t/2. The maximum impact load (Pm), ductility fracture propagating energy (E2), brittle fracture propagating energy (E3)+brittle crack arrest energy (E4) and (Pm-Pf) were decreased with the decreasing of test temperature, brittle fracture tendency increases gradually, brittle fracture arrest properties become worse, while E1 changes little. The brittle fracture tendency in t/4 and brittle fracture arrest properties are better than that of t/2. In t/4, the fibre region of impact fracture at-20℃is made up of tiny dimples, while the fibre region in t/2 exhibits quasi-cleavage. The number of river pattern and tearing ridge in t/2 is more than that of in t/4 in radial region. The pearlite colony is a mixture of lamellar pearlite (LP) and degenerated pearlite (DP). The DP content in t/2 is increased, the LP’s lamellar pearlite interlamellar spacing is larger than that in t/4.
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