3.5% Nickel steel

[mrithyun jay]

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.

[Rajagopal Kannan]

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

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[nitin patil]

your assumpyion is coorrect ,just reduce the pre heating time 

 

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Thanks And Regards,
Nitin R. Patil
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[pgoswami]

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,

pgos...@quickclic.net

 

 

 

 

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[mrithyun jay]

Hi Pradip / Rajagopal / Nitin,

Thanks for your prompt advise. You are correct I have used E8016-C2 / E8018-C2 with Ø3.2mm (1/8") electrodes. 

To share the additional information, the applied preheat was 160°C (continuously maintained by induction coils), max. IPT was 300°C and heat input ranging between 1.5 to 1.8kJ/mm. All mechanical tests / NDE comply with ASME VIII Div 1 with CVN values well above 110J. I have already checked the based material hardness which is below the specification limits < 197HBW. And the re-test of the cap HAZ revealed the nearly the same values ~ 270HV10.

Given the preheat, max. IPT, heat input and compliance of mechanical tests / NDE, I am wondering what could be the likely reason. Any more thoughts or do I need to carry on temper bead technique to get the hardness reduced OR a PWHT for 10.97mm wall thickness?

Thanks & Regards

Mrithyunjay

[arijoy roy]

Dear Mr. Mrithyun jay

I would suggest you study the micro structure of the HAZ. under SEM ( specially with EPMA facility ) an try to identify the precipitation of any carbides in the HAZ. If there are fine carbides then only hardness may be reduced by globular annealing If it is only some martensite then low temperature tempering will reduce the hardness. 

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From: mrithyun jay <mrith...@gmail.com>
To: material...@googlegroups.com
Sent: Friday, 30 September 2011 2:51 PM
Subject: Re: [MW:12584] 3.5% Nickel steel