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随着现代生产技术的发展,各种新型机械产品以及高强度和超高强度的金属材料不断涌现。但在传统的强度、塑性等指标符合设计要求的情况下,仍然多次发生突然的脆性断裂,有时还造成灾难性事故。根据实践的需要,人们引进断裂韧性这个新的机械性能指标,用以衡量材料抵抗脆断的能力。十几年来,国内外都对此开展了大量工作。我室对某些钢种断裂韧性从宏观现象到微观机理进行了研究,并对断裂韧性与强度之间的辩证关系作了初步探讨。过去有些人从某些钢种的强度提高时,断裂韧性就相应降低的现象出发,认为断裂韧性与强度二者似乎必然是此消彼长、互相排斥的。实验事实说明这种看法是片面的。断裂韧性与材料的化学成分、金相组织等都有关系。在某些条件下,如对许多中碳合金结构钢,断裂韧性与强度主要表现为互相排斥,二者有相反的变化趋向;但它们之间的关系呈现出一定的阶段性,不能简单化地对待。在另一些条件下,如对我国创制的硅锰系列低碳马氏体类钢种,在一定回火温度范围内,断裂韧性与强度则表现为相互依赖,二者有相同的变化趋向,当强度提高时,断裂韧性也随着提高。可见断裂韧性与强度的关系在一定条件下可以发生转化,它们既是对立的,又是同一的。我们必须在马克思主义哲学指导下,全面认识事物的客观规律,才能根据机械零件的实际需要,充分发挥金属材料的强度潜力,达到最佳的综合机械性能。试验还表明,具有板条状组织的硅——锰系列低碳马氏体类钢种具有高强度和大韧性相结合的优点。这类钢的推广应用,将对减轻机械产品重量,同时又保证安全运行发挥积极作用。
With the development of modern production technology, a variety of new mechanical products and high strength and ultra-high strength metal materials continue to emerge. However, under the condition that the traditional indicators such as strength and ductility meet the design requirements, sudden brittle fracture is still occurred many times and catastrophic accidents are sometimes caused. According to practical needs, people introduced the new mechanical properties of fracture toughness, to measure the ability of the material to resist brittle fracture. For more than a decade, a great deal of work has been done both at home and abroad. Our laboratory has studied the fracture toughness of some steels from the macroscopic phenomenon to the microscopic mechanism, and made a preliminary discussion on the dialectical relationship between fracture toughness and strength. In the past, some people started from the phenomenon that the fracture toughness was correspondingly reduced when the strength of some kinds of steel increased, and it was considered that both the fracture toughness and the strength seemed inevitably to be counterbalanced and mutually exclusive. Experimental facts show that this view is one-sided. Fracture toughness and the chemical composition of the material, microstructure and so on. Under some conditions, such as for many medium carbon alloy structural steels, the fracture toughness and strength are mainly mutually exclusive, and both have the opposite trend. However, the relationship between them shows a certain stage and can not be simplified treat. Under other conditions, such as China’s low-carbon martensite series of silicon-manganese series of steel, in a certain tempering temperature range, the fracture toughness and strength are shown as interdependence, the two have the same trend of change, when As the strength increases, fracture toughness increases. Visible fracture toughness and strength of the relationship between the transformation under certain conditions, they are both opposites, but also the same. Under the guidance of Marxist philosophy, we must fully understand the objective laws of things so that we can give full play to the strength potential of metal materials and achieve the best comprehensive mechanical performance according to the actual needs of mechanical parts. The tests also showed that the silicon-manganese series low-carbon martensitic steel with lath-like structure has the advantage of combining high strength and toughness. The promotion and application of such steel will play an active role in reducing the weight of mechanical products while ensuring safe operation.