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RE: [MW:13732] RE: 13484] Pre-heating for cutting

By Materials & Welding
Dear Gerald
Yes, it is often recommended as good workmanship practices but is there anyware in Codes required as mandatory requirement?
Thanks
Ganesan
 
Date: Wed, 18 Jan 2012 04:18:53 -0800
From: gerry_tup@yahoo.com
Subject: Re: [MW:13501] RE: 13484] Pre-heating for cutting
To: materials-welding@googlegroups.com

For carbon steels upto certain thickness it is not required.

Only when the thickness is very high and for Chrome-moly steels it is recommended to preheat the base material before cutting to avoid formation of undesirable phases which leads to cracking. Preheating before cutting will result in grain coarsening and impair the Impact properties.

Moreover it is always recommended to grind the HAZ of the Gas cut surfaces.
 
Thanks & Regards

J.Gerald Jayakumar
0091-9344954677
From: DEBASISH <debasish.uae@gmail.com>
To: materials-welding@googlegroups.com
Sent: Wednesday, January 18, 2012 1:08 PM
Subject: Re: [MW:13500] RE: 13484] Pre-heating for cutting

Perfect. To add more on this:
Basically this becomes more and more stringent, in case of low temp. steels, wherein the grain coarsening is detrimental to it's Impact ( Toughness ) properties. Also, Preheating before flame cutting is required to decrease the thermal gradient which eventually decreases the chances of grain coarsening & also reduces thermal shock or any initiation of micro fissuries leading to cracks latter. Workshop remedy is: we ask to remove the HAZ formed by flame cutting,  by grinding the skin of the flame cut edge preparation.  Offcourse, This stringent practice is generally not required for general Mild steels grades of steel.
regars,
DEBASISH
Dubai
+971504349936.
 
 
 
 
 
On Tue, Jan 17, 2012 at 2:35 PM, sandeep monody <smv.monody@gmail.com> wrote:
Dear all,
 
 
The purposes of preheat are to avoid crack due to sudden heating and for wide heat affected zone,so in my openion preheating is required for both cutting and welding.
 
Regards,
 
Sandeep.M.V
 


 
On Tue, Jan 17, 2012 at 10:31 AM, Lakshman Kumar.B <lakshmankumar4@gmail.com> wrote:
Dear All,
 Beyond all the technical aspects, small logic for this situation….
This is only my view…
 
After cutting the edges are again welding to some part / connection(say pipe, fitting, flange, etc or leaving like that) in all the cases if welding is going to do it will be again preheat and PWHT after welding so any thermal shocks will be relived during PH, PWHT,
 
So I think no need of pre heating.
 
Thanks and Regards................?
 
Lakshman Kumar.B|Manager |Lanco Infratech Limited
Plot No 1255 | Sanjeevani chowk | Mahanadi vihar | Cuttack 753004
Phone : + 91 671 2445033 | Mobile : +91 9937286851 |www.lancogroup.com
Go Green|The future will thank you
 
 
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of jesti fer
Sent: Monday, January 16, 2012 3:22 PM

To: materials-welding@googlegroups.com
Subject: [MW:13484] Pre-heating for cutting
 
Dear Experts,
 
I need your help for this subject, We are fabricating some piping as per B31.3, the material ASTM A106 Gr.B, 8"Sch-XXS and 160 and we are doing preheat and PWHT for welding, but my enquiry pre heat is required for cutting also? It is mentioned in any code or any other were? Please help me
 
Jesti
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