超大型ZG10MnNiCu 钢铸件显微组织与低温冲击性能的关系

Microstructural characteristics of heat-treated test blocks from the thick-walled sections of ten-ton ultra-large ZG10MnNiCu castings were investigated via Charpy impact test,metallographic microscopy and scanning electron microscopy (SEM)to solve the problem of unstable impact property of the large ZG10MnNiCu steel casting for marine applications. The low-temperature impact property of the test blocks was characterized,and the microstructural features and fracture morphologies of the specimens with different impact absorbed energy were systematically analyzed,thereby revealing the correlation between the microstructure and impact property of the ZG10MnNiCu steel. The results indicate that the microstructure of the ZG10MnNiCu steel after pre-treatment,normalizing and tempering is a mixture of ferrite and a small amount of pearlite,but the microstructure is uneven,which leads to a significant dispersion of low-temperature impact absorbed energy,indicating that the low-temperature impact property of the ultra-large ZG10MnNiCu steel casting is more sensitive to microstructure. Correlation analysis of the microstructure and property shows that the grain size,pearlite morphology and lamellar cementite parameters jointly determine the low-temperature impact property. Finer grain size,lower pearlite content,smaller pearlite lamellar spacing,more uniform structure distribution within the pearlite colony,and smaller thickness and spacing of lamellar cementite lead to higher impact absorbed energy and better impact toughness of the ZG10MnNiCu steel. As a result,its impact fracture shows ductile characteristics. Conversely,the fracture exhibits brittle features.