Re: [MW:11792] Impact value in HAZ

Dear All:

Smaller Diameter electrodes have a small HAZ with smaller grain size comparing to runss deposited by larger diameter electrodes. And they have a tempering effect on previous welds and their HAZ's that is a good thing and improves toughness.

The only issue with smaller electrodes is the high distortion comparing to weld deposited by larger electrodes.

This is a common mistake in welding that you consider the " total heat input" as a criteria for toughness.

Here is the reason:

Every run has a HAZ.
A portion of this HAZ that includes the base metal is our final HAZ.
Other portions include previously deposited weld metal that doesn't cause toughness problems, in fact their toughness will be improved by tempering effect.
The smaller is the electrode size, the smaller is its HAZ and its grain size.

So do not use larger sizes if you have HAZ toughness issues in your PQR.

Good Luck

Ramin  Kondori

   QC/Welding Engineer 

         IWE AT 0070

   

On Sun, Jul 17, 2011 at 8:15 AM, abin eldhose <eldhoseabin@yahoo.com> wrote:

Dear Sandeep, When you use smaller dia electrodes it will decrease heat input for sure. But the total heat input is what matters. If you use higher dia lesser number of pass is required. So we cannot confirm unless you tested with both big and small dia electrodes to verify toughness values. Thanks & Regards Abin Eldhose QC Inspector DAEWOO E&C RRE EPC-4 PROJECT TEAM Tel: +971-56-7103039 email: eldhoseabin@yahoo.com --- On Sat, 16/7/11, sudhakar kuppuswamy <mechsudhakar@gmail.com> wrote: From: sudhakar kuppuswamy <mechsudhakar@gmail.com> Subject: Re: [MW:11769] Impact value in HAZ To: materials-welding@googlegroups.com Date: Saturday, 16 July, 2011, 11:15 PM Dear sandeep,                       To achieve better HAZ impact property you can weld with temper bead technique, where the HAZ is subjected to less heating during welding when compared normal technique.                    Preheat  the base material to  about 100 C (if the carbon content is high go for higher degree of preheat), this will reduce the rate of cooling so you can avoid martensite formation (which is a hard structure) and end up with pearlite( fine grain structure, which has good impact property)                    If Ur welding thick sections, doing PWHT will helps to achieve good HAZ impact properties                   By using smaller dia filler wire you can use lesser current  which inturn reduce Heat input, (heat input is the function of current, voltage ,travel speed)   but the rate of cooling will be high  (high cooling rate is not advice able), this can be controlled by doing preheating.                     If you do post heating (immediately after welding) for few minutes (say 30 min) ,cooling rate will be very slow and you will get fine microstructure like pearlite or bainite  instead of martensite . On Sat, Jul 16, 2011 at 4:43 PM, yusufkhan pathan <yusufkhanp97@gmail.com> wrote: Dear sandeep,   However as mentioned by Dinesh, voltage, current & travel speed as the important factors afftecting the heat input. as per my past experience related to SMAW we used to control these factors by increasing the travel speed thereby resulting in good impact values. I am not sure about GMAW, whether this method can be applicable. Another factor which effects the energy value is the choice of consumables.   Regrads, Yusufkhan. M. Pathan Engineer-Quality Air Liquide Engg (IND) Pvt.Ltd. Email to : yusufkhan.pathan@airliquide.com Cell:(+91) 8008804165   On Wed, Jul 6, 2011 at 12:29 PM, sandy <sandeepdhiman63@gmail.com> wrote: Dear All How we can get better impact values in HAZ with GMAW process in non alloyed carbon steel? like with multi pass welding. Please provide your valuable ideas. Regards Sandeep Kumar -- To post to this group, send email to materials-welding@googlegroups.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. -- To post to this group, send email to materials-welding@googlegroups.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. -- With regards, Sudhakar.k -- To post to this group, send email to materials-welding@googlegroups.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

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To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.