weld low temperature steel with none nikel SAW wire/flux

Date 03-29-2007 13:47

You might wish to post the chemistry of you're wire and wire flux deposit. And keep in mind that the removal of certain residuals will lower the DBTT (ductile to brittle transition temperature) and therefore CS's are achieving impacts much greater than 30 or 40 years ago, for example Grade 6 A-333 which has a minimum spec of 13 ft/lbs at. All this with no particular alloying, but with the addition of a fine grained practice. Perhaps your Kobe material is achieving something similar.
-50deg F, and routinely does much better.
Having said that you should also post what it is you mean by high toughness

By js55

Date 03-29-2007 18:01

That's -50deg F.

By CWI555

Date 03-29-2007 18:53

You may want to refere to section VIII Part ULT

By jiweiming (**)

Date 03-30-2007 01:26

Thanks.But what the difference between low temp and cryogenic is? Is the latter's temperaturte lower? If so, usually cryogen mean how low the temp is ?
"In regards to H2S environment, We would have to have the specific material. " What do you mean?

By CWI555

Date 03-29-2007 21:55

From the Kobe manual:
Classification: ASME / AWS A5.17 F7A8-EH14, F7P8-EH14
Features : &#56256;&#56722;Suitable for butt welding of structures for low temperature service
&#56256;&#56722;DC-EP current is only applicable
&#56256;&#56722;Excellent impact value at low temperatures down to -60&#56271;&#56772; and
CTOD at temperatures down to -20&#56271;&#56772;
Redrying conditions of flux: 200~300&#56271;&#56772;x1h

From what I see, any steel that this material covers will be low nickel if any. I think you may be thinking about the cryogenic grade materials such as A553 which is 9% nickel.
In regards to H2S environment, We would have to have the specific material. I don't think the temperatures in the ranges you've specified are going to matter, I think it's going to be more in line with the H2S resistance. If I am not mistaken, the temps your specifying are considered refrigerated/low temp. not cryogenic. I doubt you'll see the higher nickel values until your into cryogenic the crogenic service range. .

By jiweiming (**)

Date 03-30-2007 01:36

Thanks. Do you know if this KOBEL WELDING CONSUMABLES can be used in H2S stress corrosion service?

By CWI555

Date 03-30-2007 03:25

H2S (hydrogen sulfide). I don't think the supplier is as important as the wire chemistry properly matched with the base material for the surface intended. I don't know exactly what service, what code, or what base material you have, so thats about the best answer that can be given at this time.

By js55

Date 03-30-2007 14:18

As a partial answer to one of your questions, cryo is considered lower than low temp, terminologically speaking. Minnesota December ambient (or Michigan as I'm sure Jon can testify) can be considered low temp, but unless a new ice age has moved in, it wouldn't be considered cryo.
I'm sure there is probably a specific temp at which cryo is considered to be the regime, but I don't know it off hand. Maybe -150F.

By CWI555

Date 03-30-2007 16:34

Your correct, cryo is considered to be -150 and below.

By GRoberts (***)

Date 03-31-2007 07:14

The Kobe product may be similar to this Lincoln carbon steel flux/wire.

http://www.mylincolnelectric.com/LEExtranet/certs/pdf_lib/US58820_20050215.pdf

SAW fluxes/wires that are designed to get acicular ferrite with low impurity levels, such as P, S, O, N, and probably some other trade secrets thrown in can get that toughness without nickel additions. Lincon's flux was just develped though, so I'm not sure how recently these toughness levels withot Ni have been achievable.

As for the H2S service, you should review a document such as NACE MR0175/ISO 15156 for the oil production side, or they have another one for refineries, but I can't remember that document is right now. The general principal is- not more than 1% Ni in the weld deposit, plus qualificaiton of the WPS by hardness testing. Then NACE has it's own set of essential variables that affect hardness that apply to the hardness tested WPSs. Items such as carbon equivalent of the base metal, PWHT, heat input, etc.