Welding of F91 material

[mmm]

Seal weld joint between bonnet and body
1)Weld deposit thickness is 8mm.
2)design code- API-602
3)Electrode - E9015-B91
4)base material for bonnet and valve
body- SA 182 Gr F91
5)hardness of the weld joint is 300 BHN.

Dear experts
a)Please let me know what are method to reduce the Hardness of the weld joint?
b) is this electrode is correct or not please specify if its wrong

Thank you.
MNK

[Prakash Hegde]

MNK

Presume the weld is  F91 to it self ( P= 15E  to P15E) where you require to follow certain welding discipline

i.e. Preheat -> Welding continuously  not below preheat temp->Post heat at about 300-320C (If asked by client spec)-> cool below 100C to convert to martensetic sructure -> later PWHT as per Code say 730-760C  Then only you will get hardness between 190-260BHN which is generaly acceptable limit

(If SMAW E9015 B9 is used with lower H control)

Regards

Hegde P.b.

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[Thompson, Dennis]

Hi MNK,

What were the temperature/time parameters of the :

1. Weld preheat heat treatment (PHT) and interpass?
2. The post weld dehydrogenation heat treatment (DHT)?
3. The post DHT cooling?
4. The post weld heat treatment (PWHT)?

Regards,
DT

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[mmm]

Hegde

Thanks for your reply

till now we have not carried out PWHT, please correct me if i am wrong,

a) as per B16.34 for PWHT we have to follow ASME section viii Div-1,

b) as per section viii for P# 15E ( table UCS-56) please correct me if following the info is wrong

               TEMP RANGE -730  TO 800 Degree Celcius

                SOAKING TEMP  - 800 Degree Celcius (Ni-Mn is less than 1 %)

                HEATING RATE - NOT MORE THAN 222 c

                COOLING RATE - NOT MORE THAN 280 c

                 SOAKING PERIOD - 1 Hr / inch ( our job is 15 mm thick fillet weld)

                   temperature variation during soaking is max 83 c

                    

c) what is the temperature variation max permitted during heating and cooling rate?

regards

MNK

[Rajesh S.Mhaske,Engineer Welding,CSWIP,ASNT,Pune,]

Dear MNK

  Please  refer  following  details  for  Gr91 TO  Gr 91 

       Preheating  : 200 deg  c 

       Interpass temp :300 deg  C

       Post heating  :  350 deg  c  for 4 hrs 

       Weld  metal  cool  to  100 deg  c soaking  period  1hrs for  formation of martensitic structure  

       after  this  start the  PWHT @ 760 /120 min minimum  

       cooling  and  heating  rate  :  80 deg c / hr 

       unloading  at  : RT 

      Hardness  test  -  Acceptable limit  245 to 260 

[George Dilintas]

Normally all P91 welds must be pwhted whatever the thickness might be

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