Re: [MW:27770] AWS D 1.1 interpretation on Increase in Preheat / Interpass temperature

Hello, 

Increase and decrease of Charpy value is linked with Interpass temperature. Grain size is also linked the time maximum temperature is sustained....

Yes, The cooling rate is slightely reduced as compared with 30°c under discussion. Since PQR is qualified with Interpass temperature of 173°c, Metallurgically this does not give much sense...

It will be good if it is clarified that what is the MAX. PREHEAT in this case ??

On Wed 2 May, 2018, 8:46 PM 'james gerald' via Materials & Welding, <materials-welding@googlegroups.com> wrote:

I agree with Pandithan Sir.

Please find below the snap shot of AWS D1.1 as it indicates maximum Preheat or Interpass temperature.

Please understand the Metallurgy behind the same.

Increase in Preheat temperature reduces the Cooling Rate and hence increases the Grain size thus reducing the Charpy values.

ASME Sec.IX covers all Materials both Ferrous & Non-Ferrous and includes only ASME coded materials.

AWS D1.1 is different in terms of Materials & Temperature covered.

Thanks & Regards

J.Gerald Jayakumar

0091-9344954677

On Wednesday, May 2, 2018, 5:29:33 PM GMT+4, 'wilfred kojo' via Materials & Welding <materials-welding@googlegroups.com> wrote:

Kannayeram,

If you claim that the client comment is ok, please what is the negative consequence of increasing the preheat temperature on the mechanical properties of the weldment.

On ‎Wednesday‎, ‎2‎ ‎May‎ ‎2018‎ ‎11‎:‎43‎:‎53‎ ‎WAT, 'wilfred kojo' via Materials & Welding <materials-welding@googlegroups.com> wrote:

Increase in preheat temperature is not essential variable; decrease in preheat temperature is essential variable. 

Increase in inter-pass temperature is supplementary essential variable (applicable only when notch toughness is required).  

Any client who claims increase preheat temperature is essential variable does not understand the code requirement.

On ‎Wednesday‎, ‎2‎ ‎May‎ ‎2018‎ ‎04‎:‎58‎:‎49‎ ‎WAT, N VENKATESWARA PRASAD <weldengr.velosi@gmail.com> wrote:

Dear Experts,

We have received a comment on Increase in Preheat temperature greater than 56°C is essential variable as per AWS D.1 from our client.

My interpretation is the increase in 56°C is applicable only for inter pass temperature.  The details are as given below. 

 

PQR   Test coupon thickness        :  30 mm

PQR   Preheat temperature          :  30°C

PQR Inter pass temperature        :  173°C

 

Job Thickness                                  : > 38 mm  to 65 mm  ( As per Table 3.3)

Preheat temperature                    :  110°C

Inter pass temperature                 :  220°C

MDMT                                               :  -40 °C

 

As per AWS D 1.1  Table 4.6  Point no. 7   an increase more than 56°C in max preheat or interpass temperature is essential variable  for CVN testing applications.

 

Based on the above clause, the client is insisting that the Qualified Range for  thickness in WPS shall be restricted to 38 mm as the preheat is increased from 30°C to 110°C which is not acceptable .

 

Please provide me if you any interpretation on it from AWS.

Regards

Prasad

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