SA-106-B Normalized 3

[chaulklate]

Sorry to anyone who read this already, I also posted in the Vessel forum.

Is there any merit in normalizing SA-106-B?

I'm on a job now where the request is as per above for use on vessels subject to sulfide stress cracking. I've heard people say that SA-106-B has no merit to normalizing as it will not move it from curve B material to curve C material as per UCS-56, as UCS-56 indicates not only a normalizing requirement but also a 'fine grain practice' requirement. ASME defines 'fine grain practice' as it applies to SA-20 as per interpretation VIII-1-92-100, SA-20 is a plate spec and would therefore not apply to SA-106-B. We could probably all agree that you could normalize it, normalizing is really a heat treatment and anything (within reason) can be heat treated.

So, if someone requests SA-106-B normalized, does this request have any value?

 

[metengr]

chaulklate;
Normalizing as a separate heat treatment step for this plate will result in a more uniform grain size and slightly better ambient temperature strength. Note that I stated ambient temperature service, not elevated temperature service. That is it - I see no reason to specify normalizing for SA 106 material, considering this material by specification is for elevated temperature service.

 

[DrJim]

What will normalizing SA-106-B do to impact values at zero degrees F?

 

[metengr]

Normalizing will slightly increase the strength of the SA 106 material, but I would expect no real benefit in notch toughness because it is the fine grain practice and/or alloying that promotes notch toughness.

 

[vesselfab]

we see this "request" for normalized a-106-b all the time.

we refuse to go to the hassle of normalizing small pieces of pipe and running new physical tests for something that adds no value because someone asks for it.

it is normally because some "expert" thinks that if the plate is normalized, that everything that touches that plate, internal or external, pressure or non-pressure, should be normalized.

if they insist, we offer a-333 pipe
if they don't want that,or some other normalized pipe.. sorry.

 

[SJones]

Is it a 'request' or is it specified. One reason to specify normalising for A106 is to prevent a suspect hot finishing process and maximise lot uniformity. A333 is a better standard because it specifies the hot finishing (normalising forming) temperature requirements whereas A106 does not.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[DrJim]

Steve,
It is being considered to get acceptable charpy values (17/12 ft-lbs @ 0 deg F) from A106-B. Other material options are not available in sizes needed.

It appears the critical variable to get acceptable charpy values from A106-B is the Mn level. The higher the Mn the higher the charpy.

Has anyone verified or disproved this statement?

Would NQT or QT yield better charpy values than normalizing?

 

[vesselfab]

CHARPY'S at 0*f

is this pipe over 1" thick?

 

[stanweld]

DrJim,
What are the current absobed energy values? It is quite possible that normalizing will prove effective. Appropriate normalizing will refine the current grain structure. I have often seen a 20 F delta due to normalizing in both A-106 and A-105 - even greater through double normalizing.

 

[metengr]

DrJim;
SA-106 Grade B pipe material is permitted for use down to -20 deg F by ASME B&PV Code without having to conduct impact tests for material thickness 3/8" or less. This means that for lower temperature service conditions, SA 106 Grade B that is 3/8" or less posses adequate notch toughness to satisfy 15 ft-lbs at -20 deg F (using Curve B as shown in Figure UCS-66). You can normalize until the cows come home and you will not gain relief from the impact exemption curve because you need both a fine grain practice AND N&T or N heat treatment.

 

[DrJim]

Thanks for all the feedback. The A-106 is 16" OD x 11" ID (2.50" thk) - ID finishes at 12". I do not know current values. The vessel vendor found a heat of A-106-B with .71 Mn. I sense something magic about >.70 Mn. He will cut off 6", normalize it, and run impact and tensile tests on it to see if we have a winner. If close, you talked me into a double normalize, or would QT after N be better than a second normalize? Again, thanks.

 

[metengr]

Q&T is not the same as N&T. Quenching in this sense is only used by agreement between the purchaser and vendor and typically is used for heavy wall sections to enhance a rapid cool rate for normalizing. At 2.5" thick, you probably would need enhanced cooling (liquid spray) for a true normalizing heat treatment. I would not double normalize for this plate thickness.

Keep in mind that Grade B has by specification 0.30% C max, and this will be your limiting factor for notch toughness at lower temperatures for material that is not fine grain.

 

[stanweld]

DrJim,
I have seen absobed energy values of 17/12 at 0 F in the hot formed condition of A-106 B. I have also seen the same values between 32 F an 40 F. I recommend that you determine what the absorbed energy values are in the pipe now at at 0 F before normalizing or define the transition temperature of the material, unless you do not have adequate material for conducting the tests.

If insufficient material exists, I recommend that you double normalize, test and hope for the best.

 

[DrJim]

Thanks Stanweld,
My supplier has contacted the mill and found that impact values in excess of our needs are obtain consistently when the available material is normalized, quenched and tempered. That procedure is currently being tested on a 6" sample of the 2-1/2" wall thickness A106-B tubing.