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Join Date: Jul 2014
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Hardness-Difference Between Weld & HAZ for P91 Weldments?

11/10/2017 5:31 AM

Dear Sirs,

I wish to know, what should be the maximum difference in hardness between the weld & the HAZ in case of SA 335 P91 pipes welds after PWHT.

Thanks & regards,

D.D.N. VERMA

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#1

Re: Hardness-difference between Weld & HAZ for P91 Weldments ?

11/10/2017 9:13 AM

The expected hardness range is 200-275 BHN. Keep in mind that hardness testing is only a sorting method and does not provide the total heat treatment condition of the P91 weld and base metal heat affected zone (HAZ). If necessary, surface replication should be used to evaluate the microstructure of the weld and HAZ to corroborate hardness test results. .

After PWHT, P91 is significantly more ductile. Its Rockwell C hardness drops to the low 20s and its Charpy V-notch toughness can increase to 40 to 70 foot-pounds, depending on the welding process.

So, this is the reason for not having to specify an acceptable hardness range in the

material specification. (i.e. ASME B31.3)

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#2

Re: Hardness-difference between Weld & HAZ for P91 Weldments ?

11/10/2017 9:14 AM

Why would you ask, unless someone has asked you?

Have you looked at AWS/ASTM/industry specifications?

ASTM A335/ASME SA335 P91 High Pressure Steel Pipe - Piyush Steel

Have you asked your pipe supplier?

Have you asked your welding supplier?

You could always weld up some samples and test them.

Or, if it's really important, have them tested by a certified test facility and get official results, not a guess.

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#3

Re: Hardness-Difference Between Weld & HAZ for P91 Weldments?

11/10/2017 1:17 PM

Whatever Whitephone lays out for you is gospel. Lyn is no newbie to these queries, either.

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Join Date: Jan 2010
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#4
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Re: Hardness-Difference Between Weld & HAZ for P91 Weldments?

11/10/2017 3:28 PM

you can believe it. Amen

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