V型缺口加工方法对材料冷脆转变曲线的影响

本文分析了各国关于V型缺口冲击试样的缺口加工方法及表面粗糙度的不同要求；选择了现行加工V型缺口较普遍的四种方法：磨、铣、拉和电火花切割；分别测试了各组试样从室温到低温下的冲击功、侧向膨胀值、纤维断口百分率；绘出了两种材料（16Mn和3.5Ni）在四种加工方法下的冷脆转变曲线。本文提出，在冷脆转变曲线的上半部分，各种加工方法之间及其本身对材料的冲击韧性影响不大（＜10％），随着温度的降低，加工方法和表面粗糙对材料的冲击韧性影响增大。

WORKING METHODS OF CHARPY V-NOTCH ON THE EFFECT OF CURVE OF THE DUCTILE-BRITTLE TRANSITION

This paper analysies the difference of standards and specifications in the world on the working methods of V-notch and surface roughness of the Charpy V-notch impact specimens, elects convention four working methods of V-notch: grinding, milling, broaching, electrospark process, measures separately the impact energy, lateral expansion, and the percentage of shear fracture at variant temperature of testing on the four groups impact specimens, draws the ductile-brittle transition' curves of two metallic materials (16Mn, 3.5Ni) on the four working methods of V-notch. This paper indicates: in the upper section of the curve of ductile-brittle transition, the effect of the working methods on impact toughness is small (<100%): with decrease of temperature, the effect of working methods (surface roughness) on impact toughness increase, in order for the impact test to conform to the requirements of standards and specifications, specially, for the impact test at low temperature, the surface roughness (Ra) or the working methods of V-notch should specify specially (RaC1.6pm).