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通过对含磷量大于0．1%的高磷球铁机械性能和断裂力学性能试验,研究考察了含磷量对球铁的强度、断裂韧性和疲劳断裂特性的影响。试验表明:随着含磷量的增加,断裂韧性K_IC值下降,而对裂纹扩展的界限应力强度因子K_th值影响甚微,一般都高于结构钢的K_th值。金属型复砂铸造工艺能改善高磷球铁的铸造性能和断裂韧性,表面氮化工艺则在一定幅度内提高高磷球铁的K_th值。采用金属型复砂工艺铸造的铸态高磷球铁在强度和断裂韧性诸方面均达到了砂型铸造的经正火处理的低磷球铁水平。本文认为:磷分高于0．1%的球铁可以作为承受疲劳载荷的重要构件(如曲轴)材料。
The mechanical properties and fracture mechanics properties of high phosphorus ductile iron containing more than 0.1% phosphorus have been investigated. The effects of phosphorus content on the strength, fracture toughness and fatigue fracture properties of ductile iron have been investigated. The results show that with the increase of phosphorus content, the K_IC value of fracture toughness decreases, while the K_th value of the crack growth stress has little effect, which is generally higher than that of the structural steel. Metal-type sand casting process can improve the casting performance and fracture toughness of high-phosphorus ductile iron. The surface nitriding process increases the K_th value of high-iron ductile iron within a certain range. The as-cast high-phosphorus ductile iron, which is cast by the metal-type compound sand process, achieves the normalized low-iron ductile iron content of the sand-type foundry in terms of strength and fracture toughness. This paper argues that ductile iron with a phosphorus content higher than 0.1% can be used as an important component (such as crankshaft) for fatigue loading.