铈对S32750超级双相不锈钢低温冲击性能的影响

通过夏比冲击和示波冲击方法分析了两种Ce含量S32750超级双相不锈钢在20~－100 ℃范围内的冲击吸收能量及能量构成差异,利用Aspex自动扫描电镜分析仪、SEM、EDS研究了Ce对钢中夹杂物的改性行为及冲击断裂行为的影响。结果表明:高Ce试验钢的抗低温冲击断裂性能明显优于低Ce试验钢,前者韧脆转变温度相较后者下降16 ℃;Ce的添加使得试验钢－80 ℃冲击吸收能量提高45 J,其主要源于裂纹扩展能W_p的提升(76%)。冲击断口形貌观察和夹杂物分析结果显示,低Ce试验钢在－80 ℃冲击断口表现为完全解理断裂;相较于低Ce试验钢,高Ce试验钢中Al₂O₃夹杂显著减少,多为改性后的铈铝氧复合夹杂;硬脆Al₂O₃夹杂数量的减少有效改善了钢的冲击性能。

Effect of cerium additive on low temperature impact properties of S32750 super duplex stainless steel

The differences of impact absorption energy and energy composition between the two super duplex stainless steels with different Ce additives in the range of 20 ℃ to -100 ℃ was analyzed by means of Charpy impact test and oscilloscope shock method. Effects of Ce additive on modification of inclusion and impact fracture behavior of the steel were studied by means of Aspex automatic scanning electron microscope, SEM and EDS. The results show that the low temperature impact fracture resistance of the high Ce tested steel is obviously better than that of the low Ce tested steel, and the ductile-brittle transition temperature of the former is 16 ℃ lower than that of the latter. The addition of cerium increases the impact absorbed energy at －80 ℃ by 45 J, which is mainly due to the increase of crack growth energy W_P (76%). The results of impact fracture morphology observation and inclusion analysis show that the impact fracture of low Ce tested steel at －80 ℃ shows complete cleavage fracture. Compared with the low Ce tested steel, the inclusion of Al₂O₃ in the high Ce tested steel is significantly reduced, and most of the inclusion becomes the modified composite Ce aluminum oxygen inclusion. The decrease of the content of hard and brittle Al₂O₃ inclusions effectively improves the impact properties of the tested steel.