Microstructure and Mechanical Property of 1800MPa Grade Low Alloyed Ultra-High Strength Steel for Engineering Machinery
LIU Shuang1,2，TANG Guang-bo2，LI Ji-guang1，SUN Hao-yuan1,2，LI Bin1,2
1. School of Material and Metallurgy, University of Science and Technology Liaoning, Anshan 114000， Liaoning, China 2. Institute for Special Steels, Central Iron and Steel Research Institute, Beijing 100081, China
Abstract：A novel 1800MPa grade low alloyed ultra-high strength steel for engineering machinery was designed and its hot rolling was simulated on a pilot hot rolling mill. Effect of different processes, such as process 1 (deformation of 80% + direct-quenching + tempering at 250℃), process 2 (deformation of 90% + laminar cooling to 650℃/1 h + air-cooled + tempering at 250℃) and process 3 (deformation of 90% + air-cooled to 650℃/1 h + air-cooled + tempering at 250℃), on the microstructure and mechanical properties were investigated. The results indicate that the sample of process 1 has a maximum tensile strength of 1816MPa and yield strength of 1473MPa with elongation of 13 percent and reduction of area of 45 percent, the impact energy of room temperature and -40℃(KV2) is 28J and 21J respectively, and the hardness value is 50HRC. It might be from the comprehensive effect of strengthening mechanisms due to the lath martensite+retained austenite, composite micro-alloy carbide and ε-carbide precipitation. Multi-phase microstructure involving lath martensite+upper bainite+retained austenite, lath martensite+acicular ferrite+lamellar pearlite+retained austenite can be obtained by the processes 2 and 3 respectively, and the mechanical properties dramatic decline. The second phase precipitation composite particles are precipitated with Nb,V,Ti.
2014, Vol. 49 
