Thanks for the calculation. I’m curious though, the cooling rate calculation that I typically use are the ones derived by CF Adams which are based on Rosenthal’s work. There are two equations, 2D and 3D heat flow.
Could you tell me where the calculation you use is derived from? Also, is the Martensite Transition Temperature the Martensite start temperature or is it the nose of the TTT diagram? When I run the calculation based on Adams for the same heat input you used I get a different answer (very different).
The reason I ask is that I am putting together an electronic handbook in MathCAD called “The Welding Engineers Tool Box” In that book I have a section on cooling rates in which I use the Adams calculations. However, yours seems simpler and I am thinking of incorporating it into the book in addition to the Adams calculation.
Back in the office I have the Adams paper from the AWS magazine. In it is a chart for the transition from 2D to 3D that shows a start at about .5" and fully 3D at about 1". I can get you the reference next week if you like.
EWI has a for sale program that is supposed to be more accurate than either Adams or Yurioka, used for hot tap calculations of T8/5 and hardness.
MURZ,
("Also, is the Martensite Transition Temperature the Martensite start temperature or is it the nose of the TTT diagram? When I run the calculation based on Adams for the same heat input you used I get a different answer (very different)."
The Ms temp. is not the "nose" of a TTT curve. The nose tells you the time required to form pearlite from austenite. Only when you cool fast enough to retain some austenite below the nose is it possible to form something else-like Martensite or one of the Bainites. Don't take offense, but this is really about as basic as steel metallurgy as one can get. (no pun intended<g>)
Metalguy,
No offense taken. However, I believe you read my question wrong. I was asking if the Martensite Transition Temperature you use in your sheet was the martensite start temperature or the nose of the TTT diagram. I realize that the Ms is not the nose of the TTT diagram. Can I assume the Martensite Transition Temperature of 1105 K (831.85 C) is the Ms temperature. Is this true? It just seemed high for an Ms Temp.
I am reviewing some TTT diagrams now where the Ms temperature is about 780 K (C=.12, Mn = .43, Si = .12) and a 2.25 Cr 1 Mo where the Ms is about 790 K (C=.12, Si=.26, Mn=.48, Ni=.08, Cr=2.0, V=0.08)
Can I assume the Martensite Transition Temperature of 1105 K (831.85 C) is the Ms temperature. Is this true? It just seemed high for an Ms Temp. Yes, this was a value that I pulled out of my head to test the routine.
A good estimate (Stuhlmann) of Ms for low alloy steel
Ms = 561 - 474*C - 33*Mn - 17*Ni - 17*Cr - 21*Mo
where C, Mn, Ni, Cr, Mo are percentage concentartions of each alloying elements.
The 1105 K temperature is too high for the Ms Temp. This is no doubt the Upper Critical Temp. above which transformation to 100% Austenite occurs. Of course this temp. varies with Carbon content and Manganese content.
