38CrA钢的T-ln((?)_0/(?))-D^(-(1/2))冷脆断裂控制图和机制图的研究

THE RESEARCH OF T-ln(ε_0 / ε)-D^(-1/2) COLD BRITTILE FRACTURE CONTROLLING DIAGRAM AND MECHANISM'S DIAGRAM FOR 38CrA STEEL

从理论和实验上研究了38CrA钢光滑拉伸试样的韧脆转移温度T_(NDT)、A(A=ln(?)和D^(?)之间的关系。得到其屈服应力σ_(YS)与A之间具有指数关系,其T_(DNT)与D^(?)之间具有线性关系,并且得到T_(DNT)与ln(?)乘积为一材料常数等关系。建立了三维冷脆断裂控制图和机制图,它们不仅可以用于冷脆断裂的分析、诊断、预测、控制和预防,而且可以用于低温构件的设计、选材和安全评估。

In this paper , the comprehensive relationship among TNDT, A (A =ln(ε0 /ε) and D -1/2 are researched in theory and experiment in smooth tensile specimen of 38CrA steel. The following relations are obtained : the relation between the yield stress σYS and A is an exponential one, the relation between ductile brittle transtition temperature TNDT and grain size D-1/2 is linear, and the multiplier of TNDT and In(ε0 /ε) - D-1/2 is a constant of material. According to the formulae mentioned above, three dimension T-ln(ε0 / ε) - D-1/2 cold brittle fracture controlling diagram and fracture mechanism's diagram are established. They can be used not only in analysis, diagnosis, prediction , controls and prevention of cold brittle fracture , but also in design, choice of materials and safe evaluation of structural parts in low temperature.