Microstructure and mechanical properties of austempered high silicon cast steel

The influence of austempering treatment on the microstructure and mechanica l properties of silicon alloyed cast steel has been studied. The experiment al results show that an ausferrite structure consisting of bainitic ferrite and retained austenite can be obtained by austempering the high silicon ca st steel in a large temperature range (240-400 degreesC). No carbide would precipitate in the structure. The experimental results also indicate that a full ausferrite structure could be obtained by austempering the steel with a silicon content around 2.64%. Lower silicon would result in the formatio n of martensite, and excessive silicon would cause proeutectoid ferrite in the structure. The full ausferrite structure has high strength, toughness a nd hardness. With the increasing of silicon content, the strength decreases , the hardness keeps unchanged and the toughness firstly increases to a max imum value and then decreases. The material has also excellent work hardeni ng ability. (C) 2001 Elsevier Science B.V. All rights reserved.