Tack welding of Low alloy steels.

[P.Rao]

Dear All,

We Know Low Alloy steels materials like P4, P5.....requires

Preheat before welding as well as postheating after welding.

As per my client specifications, i need to needs to do 150 deg.C

preheat & 200deg.C postheating for 2hrs.

Query:1. I needs to follow the same thing for tacking?.

2. If GT AW process i use ( No flux/coating involved, No question of diffussible hydrogen level to be dried off after welding)

for tacking, can i eliminate postheating?

3. Is there any other mothods of simplifying/avoiding postheating.

P.Rao

[Karthik]

Hi, Please find suggestions as below.

Query:1. I needs to follow the same thing for tacking?.

Yes.If you are going to use this Tack weld incorporate with final weld.If u plan to grindout the tack weld..then no need.

2. If GT AW process i use ( No flux/coating involved, No question of diffussible hydrogen level to be dried off after welding) for tacking, can i eliminate postheating?

Actually,Post heating is required by some customer to avoid cold crack if the PWHT is not followed immedietly after the weld.In your case,if you are use this tack weld as a permanent final weld and after tack weld if the final weld done after a long time,then you have to do post heat as per your customer spec.

3. Is there any other mothods of simplifying/avoiding postheating.

As the post heat required by your customer,yo have to follow..There is only option is you have to do PWHT immedietly after the weld finish Thanks & Regards,   (Karthik) Karthikeyan.S QA/QC Manager Getabec Energy Co.,Ltd. 379,Moo6,Soi8,Nikhomphatana, Rayong-21180, Thailand. Phone: 0066 38 897035-8 (Off) Fax: 0066 38 897034 Hand Phone: 0066 892512282 --- On Tue, 10/5/10, P.Rao <vasanth...@rediffmail.com> wrote:

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[César Alexis Viteri Pérez]

Dear Mr. Kartik,
 
PWHT has to be done inmediatelly after welding?... Is it suitable to do it after 48 hours or not?
 
Thanks and regards
Alexis
 

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Date: Mon, 4 Oct 2010 20:50:45 -0700
From: karth...@yahoo.com
Subject: Re: [MW:7367] Tack welding of Low alloy steels.

[Karthik]

Hi, Normally it can be done after 48 hours.But as per your customer spec.you need to do post heat immedietely after welding and PWHT(if applicable to your job) can be done later.But as you required to avoid post heat,PWHT(if applicable to your job) shall be done immedietely after welding. Still you have an option to avoid post heat that you can request your customer that,you will do PWHT(if applicable to your job) after 48 hours after welding finished to waive the post heating. If they accept,then no need to do post heat and you can do PWHT(if applicable to your job) after 48 hours. If PWHT is not applicable to your job,then you have to do postheat as per your customer reqirements.

Thanks & Regards,   (Karthik) Karthikeyan.S QA/QC Manager Getabec Energy Co.,Ltd. 379,Moo6,Soi8,Nikhomphatana, Rayong-21180, Thailand. Phone: 0066 38 897035-8 (Off) Fax: 0066 38 897034 Hand Phone: 0066 892512282

--- On Tue, 10/5/10, César Alexis Viteri Pérez <alexis...@hotmail.com> wrote: