厚大断面球墨铸铁低温冲击性能研究

摘要

研究了厚大断面球墨铸铁从室温到-50℃的冲击断裂韧性,分析了冲击温度对断裂的影响机制.结果表明:试样石墨平均尺寸为34.6 μm,石墨形状因子平均为0.77;V口冲击试样的韧-脆转变温度在-30℃左右,-40 ℃为零塑性转变温度.冲击韧度值随着温度的降低而成下降的趋势,冲击韧度在-25～-35℃的温度区间内出现一个平台,保持在7 J/cm2 左右,随着温度进一步降低,冲击韧度值显著下降,在最低温度(-50℃)时的冲击韧度值不足室温时候的三分之一;冲击断口从常温到低温断裂机理经历由韧性断裂到韧性+解理断裂,到最后完全解理断裂的过程.%The imapct toughnesses of the heavy-section nodular iron under room temperature to-50 ℃ was investigated,and the mechanism of the impact temperature influencing on the fracture was analyzed.The results showed:when the average graphite dimension being of 34.6 μm,the average graphite shape factor was of 0.44,the tough-brittle transition temperature was of about-30 ℃ of the V-notched specimens,and-40 ℃ was their zero toughness transition temrature.The impact toughness value showed decreasing tendency with temperature decreasing,impact toughness exhibited a fiat table in the temperature range of-25～-35 ℃ and maintaining at 7 J/cm2.When the temperature decreasing further,the toughness obviously decreased,and the value at the lowest temperature of-50 ℃ was less than 1/3 of that at the room temperature,the impact fracture mechanism change from room temperature to low temperature went through a process from tough rupture to rough + cleavage fracture and finally complete cleavage fracture.