Hi Mrithyunjay,
If sour service requirements i.e MR-0103, is applicable then the maximum allowable hardness is 22HRC (237HBW or 248HV 10)
Several grades of 3.5% Nickel steel is accepted in ASME Code. If you look carefully in Sec-II ,Pt-A, Grade D has maximum "C" restriction of 0.17%, while for grade E & F this limit is 0.20%. The compositional limits for all other alloying elements are identical for all 3.5% Ni grades.
The default SMAW welding electrode (assuming this was the weld process used) for this grade of 3.5% Nickel steel is E-8016/8018-C2 (Max C -0.12%).When hardness restriction is imposed then welding electrodes could be classified as E-7016/7018-C2L (max C-0.05%).
SFA 5.5 ,Annex-A elaborates the philosophy. If the scenario is such that:-
- PWHT is not required as per design code or project specifications
- low temperature notch toughness is to be met
- hardness requirement is imposed
then low carbon grade E-7016/7018-C2L would be advisable to use in addition to the usual cautions on heat input.
Here the issue of higher hardness is on the HAZ of the capping pass.Essentially if this scatter is isolated, re-evaluate the reading. Otherwise use a lower diameter electrode, typically 1/8" for the final pass and increase the number of runs.This would effectively do better tempering of the capping weld and adjacent HAZ and would help to control the hardness.
While welding 3.5% Nickel steel do not try to exceed the preheat and interpass temperature.Since both the factors tends to reduce the acicularity of 3.5% Nickel weld and HAZ , it could have negative impact on notch toughness values.
Thanks.
.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist & Consultant
Ontario,Canada.
Email-pgoswami@sympatico.ca,
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Rajagopal Kannan
Sent: Thursday, September 29, 2011 1:24 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:12578] 3.5% Nickel steel
Sent: Thursday, September 29, 2011 1:24 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:12578] 3.5% Nickel steel
Dear Mrithyunjay,
For the 3.5% Nickel steel, it is client to say what hardness they want.
Nace requirement is 248 HV10.
The post heating of 350 Deg.C does not seem to have much impact on HIC testing.
Thanks and Best regards,
K.Rajagopal
On Thu, Sep 29, 2011 at 9:09 AM, mrithyun jay <mrithyun.j@gmail.com> wrote:
Hello Everyone,
Currently I am qualifying a welding procedure for a pressure equipment which involves 3.5% Nickel steel. The design code is ASME VIII Div 1,
the query is what is max. permitted HAZ hardness for this material. I have got two indentations 278 and 280 vickers 10kg in cap HAZ, whilst
the others are well below 250HV10.
WT of the coupon was 10.97mm and I have done a post heating at 350°C for 2 hours (assuming it would be beneficial to address HIC). I haven't done any PWHT.
NB: Client is not sure of the permitted max. hardness, from memory - being a ferritic steel, I would assume max. permitted is 250 for NACE
applications.
I would like a confirmation from the group members, whether my assumption is correct?
Thanks everyone
Mrithyunjay.
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