Re: [MW:24501] QW406.1&3 Preheating temperature

Hi,

In addition to Lalu's comments,  preheat reduce weld cooling rate with those benefits as stated Lalu. Notwithstanding excessively slow cooling rate leads to grain growth which adversely affect the toughness the weld, hence the upper limit (supplementary essential variable). 55ºC decrease or increase is the window within which the properties of weld can be guaranteed without much change. 

Regards, 

Wilfred Kojo ( AWS CWEng )

Sent from Yahoo Mail on Android

On Thu, 10 Mar, 2016 at 11:53 am, Lalu Rajendran

<lalucpt@gmail.com> wrote:

Hi,

As per Sec IX, 55ºC (100ºF) increase(IP) is a supplementary essential variable and decrease in preheat in the same proportion is an essential variable.

There are four primary reasons to utilize preheat: 

(1) It lowers the cooling rate in the weld metal and base metal, producing a more ductile metallurgical structure with greater resistant to cracking 

(2) the slower cooling rate provides an opportunity for any hydrogen that may be present to diffuse out harmlessly without causing cracking 

(3) It reduces the shrinkage stresses in the weld and adjacent base metal, which is especially important in highly restrained joints 

(4) It raises some steels above the temperature at which brittle fracture would occur in fabrication. Additionally, preheat can be used to help ensure specific mechanical properties, such as notch toughness.

regards,

LALU

On Wed, Mar 2, 2016 at 11:01 AM, Mohd Siraj <mohd52100@gmail.com> wrote:

Dear all,

Why ASME-IX is mentioned exact 55ºC increase(IP) or decrease preheating is essential variable?

Is there any specific reason?

reagards,

--
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-welding+unsubscribe@googlegroups.com.
To post to this group, send email to materials-welding@googlegroups.com.
Visit this group at https://groups.google.com/group/materials-welding.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/dcfa92c9-337c-434c-9ff1-c42cc8868283%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

--
http://www.linkedin.com/groups/MaterialsWelding-122787?home=&gid=122787&trk=anet_ug_hm
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.
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-welding+unsubscribe@googlegroups.com.
To post to this group, send email to materials-welding@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CAOwU13suFr3y82AnQjTseBPiHD2f35sWmA-tvNY-FaVa6Rn8Fg%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.

--
http://www.linkedin.com/groups/MaterialsWelding-122787?home=&gid=122787&trk=anet_ug_hm
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.
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-welding+unsubscribe@googlegroups.com.
To post to this group, send email to materials-welding@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/207638426.89785.1457761476669.JavaMail.yahoo%40mail.yahoo.com.
For more options, visit https://groups.google.com/d/optout.