1. Regarding Thickness, there are many factors which decide the PWHT Thickness
a. Material and the Hardenability criteria
b. Restraint provided by increasing the Thickness for expansion and contraction and the resultant Residual Stresses
c. Increase in the Cooling Rate as the Heat flow changes from 2 Dimensional to 3 Dimensional beyond a critical thickness
d. Other factors
2. Electroslag welds requiring Grain refinement.
Normally in electroslag welds the Grain size is bigger, and as governed by Hall Petch equation Grain size is related to Strength and Impact properties. Finer the grain size and higher the Charpy Impact values.
Thanks & Regards
J.Gerald Jayakumar
0091-9344954677
On Tuesday, November 21, 2017, 6:01:42 AM GMT+4, new welding man <tony.navarez51@gmail.com> wrote:
Section VIII div.1 and div.2, B31.1, B31.3, etc all have a minimum thickness range(s) for PWHT. In particular for carbon steel.
The question I had was, what is the theory behind the chosen thickness? Same being for non-mandatory PWHT rules like "groove welds not over 1/2", etc
Where do these thickness originate?
Another question, why do the electroslag welds in ferritic materials in materials over 1 1/2" have to be "grain refined by heat treatment"? besides preservation of the material and things like that.
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