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Heat input, impact and hardness requirements, EN 15614-1

Heat input, impact and hardness requirements, EN 15614-1

Postby hanyu » Mon Oct 28, 2013 7:51 pm

Dear forum members,
In section 8.4.8 of EN 15614-1 is stated that:
"when impact requirements apply, the upper limit of heat input qualified is 25% greater than that used in welding the test piece"
and
"when hardness requirements apply, the lower limit of heat input qualified is 25% lower than that used in welding the test piece".
Could you please let me know why have such limits been established and how does the heat input affect both impact and hardness requirements?
Thanks
hanyu
 
Posts: 18
Joined: Fri Aug 30, 2013 10:09 am

Re: Heat input, impact and hardness requirements, EN 15614-1

Postby mohd » Wed Oct 30, 2013 6:31 pm

dear,
Increased heat input proportionally decrease the impact value, the question is why?
Increase heat input produce/transfer more heat into weld metal that decrease cooling rate and thus widen the dangerous HAZ (heat affected zone) area. The HAZ has more course grain structure than the base metal (the course grain structure results in lower toughness). So, the more the heat input is the lower the resulting toughness.

Decreased heat input proportionally increase the hardness, the question is why?
Lower heat input means less heat transfer into weld. Less heat means faster cooling. Faster cooling lead to form the dangerous martensite (quenching) since there is less time for grain structuring. Martensite has increased hardness and thus the lower the heat input is the higher the resulting hardness.

Regarding EN 15614-1, the plus/minus 25% values have been set by the EN 15614-1 committee's investigation.

regards,
mohd.
mohd
 
Posts: 74
Joined: Mon Jul 08, 2013 2:17 pm

Re: Heat input, impact and hardness requirements, EN 15614-1

Postby hanyu » Thu Oct 31, 2013 12:20 pm

Mohd,
Thank you very much for your valuable reply
hanyu
 
Posts: 18
Joined: Fri Aug 30, 2013 10:09 am

Re: Heat input, impact and hardness requirements, EN 15614-1

Postby Logosweld » Mon May 19, 2014 3:11 pm

this kind of knowledge should be mainly for welders and its mandatory because according to me these are the preconditions that should be known to every welders because it represent the well qualified welders
Logosweld
 
Posts: 82
Joined: Thu Mar 13, 2014 10:27 am
Location: India


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