High Heat Input reduces the Cooling rate as the Peak temperatures experienced from the weld zone is wider, moreover thermal conductivity remains same and it varies based on critical thicknesss as it changes from 2 Dimensional flow to 3 Dimensional flow as thickness is increased. That is the reason why Preheating is done for thicker steels to reduce the cooling rate.
Cooling Rate Formula for 3D Flow.
You will also note from the above Formula That Cooling Rate R is inversely proportional to Heat Input Hnet.
Please also find below the Cooling Rate formula for 2 Dimensional Flow.
Above formulas from AWS Handbook.
Thanks & Regards
J.Gerald Jayakumar
On Sunday, April 19, 2020, 12:00:54 PM GMT+7, Student <nabeel233@gmail.com> wrote:
Dear all
I am confused about the following statement. Can anyone tell me the reason.
High heat input causes slow cooling and low heat input causes fast cooling.
I understand that cooling is a function of temperature differences between the metal and ambulance system. If high heat input causes high temperature then temperature differential should be higher than low heat input.
Can any one tell me the reason.
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