Fracture resistance of low- and medium-carbon steels depending on type of microstructure (ferritepearlite, bainite, and martensite) and its volume fraction is studied. On the basis of studying the temperature dependence for impact strength of V-notched samples and pre-cracked specimens the contribution of work for crack initiation and propagation to the general specific impact energy of steels with a different structural type is revealed. It is shown, that the main part of failure energy in low-carbon steels with ferrite-pearlite structure is work for crack initiation. For low-carbon martensite steels the work for crack initiation and propagation is comparable. Failure resistance of tempered low- and medium-carbon steels depending on the quantitative relationship of martensite, bainite and ferrite structures is described. Characteristic structural features of lower and upper bainite influencing fracture resistance are detailed. It is shown that failure resistance of such complex structures is governed by properties of the components, and also their amount and location. Polygonal ferrite, whose separation occurs mainly at the boundaries of previous austenite grains, has a particularly unfavorable effect on ductility properties and cold resistance.

研究了取决于显微组织类型（铁素体珠光体、贝氏体和马氏体）及其体积分数的低碳和中碳钢的抗断裂性。在研究 V 型缺口试样和预裂纹试样冲击强度的温度依赖性的基础上，揭示了裂纹萌生和扩展功对具有不同结构类型的钢的一般比冲击能的贡献。结果表明，具有铁素体-珠光体结构的低碳钢破坏能的主要部分是裂纹萌生功。对于低碳马氏体钢，裂纹萌生和扩展的功是可比的。描述了取决于马氏体、贝氏体和铁素体组织的数量关系的回火低碳和中碳钢的抗破坏性。详细介绍了影响抗断裂性的下贝氏体和上贝氏体的特征结构特征。结果表明，这种复杂结构的抗破坏性受部件的特性以及它们的数量和位置的控制。多边形铁素体的分离主要发生在先前奥氏体晶粒的边界处，对延展性和耐寒性具有特别不利的影响。