将加氢反应器中的3Cr1MoV钢试块加工成直线型U型和V型缺口试样，并在-196~25℃进行小冲杆试验，对比研究了2种缺口形式试样的载荷-位移曲线、断口形貌以及E_sp/F_m（E_sp为断裂能，F_m为最大载荷）-温度曲线。结果表明：V型缺口试样的载荷-位移曲线在温度低于-140℃下存在pop-in现象；U型缺口试样的载荷-位移曲线光滑，随着温度的降低，其最大载荷先增后降，最大位移减小；在相同试验温度下，2种缺口形式试样的断口形貌差异不大；U型缺口试样的E_sp/F_m-温度曲线具有明显的上下平台，其拟合相关系数高于V型缺口试样的，因此U型缺口试样比V型缺口试样更适用于小冲杆试验评估韧脆转变温度。

Small punch tests at -196-25℃ were carried out on linear-type U-notched and V-notched specimens, which were machined from 3Cr1MoV steel test blocks in a hydrogenation reactor. The load-displacement curves, fracture morphology and E_sp/F_m (E_sp is fracture energy, F_m is maximum load) vs temperature curves of two notched specimens were compared. The results show that the load-displacement curves of V-notched specimens indicated a pop-in phenomenon below -140℃ while those of U-notched specimens were smooth. With the decrease of temperature, the maximum load of U-notched specimen increased and then decreased, and the maximum displacement decreased. The fracture morphology of two notched specimens had small difference at the same test temperatures. The E_sp/F_m vs temperature curve of U-notched specimen had obvious up and down platforms, and the correlation coefficient was higher than that of V-notched specimen, therefore the U-notched specimen is more suitable to evaluate the ductile-brittle transition temperature by small punch test than the V-notched specimen.