Heat Input in a WELD

Many Welding Engineers fail to correctly tell what is the heat input in weld ?

Surprised – do not get surprised but go on telling them the following: 

Heat input = (A x V x 60) /S

Where A = welding current Amps

             V = Arc voltage in Volts

             S = Travel speed mm/min or cm/min

Heat input will be Joule/mm or Joule/cm. 

General value of heat input may range between  1 to 2 KJ/mm – convinced ? If not what is the value you are getting in your welding process compare – think !! 

When heat input knowledge is important and MUST in Carbon Steel welding ??

To answer this question we should appreciate higher the heat input higher the cooling rate and higher cooling rate may mean possible change in microstructure which can have change in mechanical properties of weld or may be a possibility of embrittled HAZ which can be detrimental if you are trying to avoid hydrogen induced cracking !!