Cooling Time Parameter and Hardenability Estimation of HAZ in Welding of Medium, High Carbon Machine Structural Steels : Toughness Improvement of the HAZ for Macine Structural Carbon and Low Alloy Steels (Report 3)(Mechanics, Strength & Structural Design)

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Hardenability is one of the important factors for estimating weldability of steels, therefore the cooling time parameter (Δt_<8/5>) was usually used for estimating the microstructure and hardenability of lower carbon steels. However it is not clear whether the parameter of Δt_<8/5> is suitable or not for higher carbon steels. Therefore this paper has been investigated the suitable cooling time for these steels using a Gleeble tester. Futhermore by use of new cooling parameter (Δt_<8/3>) and carbon equivalent estimation equation on hardenability has been obtained. Main conclusions obtained are as follows: (1) The cooling time parameter of Δt_<8/3> is better than that of Δt_<8/5> for estimating the hardenability on the HAZ of higher carbon steels, whose carbon content is more than 0.3%. (2) The hardness of the HAZ of medium and high carbon (C≧0.3%) machine structural steels could be predicted within 15% deviation by using the introduced equation in combination of Δt_<8/3> and carbon equivalent.
大阪大学の論文