My fellow scientists
I am looking for a reliable model to calculate bainite start temperature of microalloyed steel for a computer program I am working on. So far I have found two that do not agree very much:
what are your thoughts?
Thanks in advance
do you know this not so old paper?
http://www.sciencedirect.com/science/article/pii/S1005030214000425
http://ac.els-cdn.com/S1005030214000425/1-s2.0-S1005030214000425-main.pdf?_tid=b7375364-b379-11e4-96a5-00000aacb35d&acdnat=1423829787_91b0efa3b02661c932eeb99e42fce640
On Bhadeshia site you can access materials algorithm project (MAP) and find MUCG83 (http://www.msm.cam.ac.uk/map/steel/programs/mucg83.html) which uses his theory to get Ms, Bs and other important phase transformation temperatures. For some preliminary results this is usually adequate. Since list of used elements in MUCG83 does not contain Nb, you will need to add that into program.
In our project, the Bs and Ms temperatures of micro-alloyed austenite with or without deformation were recorded by a Gleeble dilatometer and a linear regression equations for the dependence on alloying and dependence on the cooling rate were determined. I attach two tables showing the values of the coefficients to predict these temperatures. A reasonable fit.
Thank you Volker for the paper. That paper is one of the good ones I have read in the field.
Thank you David Bombac. I have tried that program. When you use the same principles (Tzero and Tzeroprime) with a more comprehensive CALPHAD database like thermocalc you end up getting results that are VERY different with MUCG83. Especially when you calculate Tzero line for instance. That program is great but needs to be updated with current data.
Thank you L.P. Karjalainen that is a great source of information. I have a little problem tho when calculating C coefficient. I end up geting positive numbers above the cooling rate of 20 C/s. Am I doing something wrong.
Unfortunately I have not done the work by myself so I cannot say anything from my experience. The report also includes tables showing the values of the coefficients for the cooling rates used in tests, and according to them, the C coefficients is always negative increasing with the increasing cooling rate, max 48 °C/s (attached file). Hence, there should be no such a problem, but I cannot guarantee that there are no printing mistakes in the equations in the report. In that case, I can ask Dr Mahesh Somani, who has done the work to check the equation(s) for errors (typos).
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