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Abstract: Effect of tempering temperature on the combination of
strength and toughness of air cooled carbide free bainite-martensite (CFB/M)
microstructure and water quenched martensite (M) microstructure for a
low carbon Mn-Si-Cr steel is experimentally investigated. The results
show that CFB/M microstructure compared with M microstructure has a
better combination of strength and toughness after intermediate
temperature tempering. The fracture toughness of the steel with CFB/M
microstructure should be characterized by JIC while that of the steel
with M could be characterized by KIC after tempering. After tempering at
360 ℃,the combination of strength and toughness of the steel with CFB/M
microstructure is s 0.2＝1355 MPa, sb＝1600 MPa, δ5＝13.5 %, j＝56.2 %, AK＝81 J,
while that of the same steel with M microstructure is s0.2＝1 350 MPa, sb＝1 617
MPa, d 5＝14.1%, j＝59.5, AK＝67.5 J. The cause might be that CFB has a
higher temper resistance than M. And carbon enriched retained austenite
film in CFB with a good thermal stability might improve the toughness of
the steel after tempering at intermediate temperature.
Key words: Carbide free bainite-martensite steel Strength and
toughness Fracture toughness
CLC No: TG142.1
国家重点基础研究发展规划基金资助项目(G1998061513). Received 20011010, received in revised
form 20020612
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