consumables for low temperature ss vessel

Date 04-04-2007 15:13

No particular specification but its preferrabler to use basic type coatings for SMAW, basic fluxes for SAW, and no ferrite fillers for FCAW.
Chuck can help us out here even more. You will see some degredation in ease of welding with basics (they won't flow and wet as well), and you will need to control heat input a little better with your no ferrite FCAW's. But those temp regimes are not particularly challenging to SS with careful WPS's.
The Charpies should not prove problematic for you. There is no precipitous ductile to brittle transition with SS's (S curves) like there is with ferritics.

By chuck meadows (***)

Date 04-04-2007 22:41 Edited 04-04-2007 22:46

Jimmie,
For cryogenic applications you will be required, by Code, to do impact testing, as Jeff said. The 3 impacts opposite the notch will be required to meet the minimum of 15 mils later expansion. Also, as Jeff said, it is best to use a low ferrite, or no ferrite filler metal. Ferrite affects the ability to meet the later expansion requirements. You can use a low ferrite, below 5FN, to have a very reasonable assurance of passing, but a pure austenitic filler like a 310 will give better results. Virtually any welding process is applicable, but FCAW has shown to have a few problems when doing the impacts due to the oxidation in the flux, but that is seldom. The thing to remember is the lower the ferrite, the better. Send me your e-mail address and I will send you a paper about filler metals for cryogenic applications.

By CWI555

Date 04-05-2007 01:24

Chuck, I'd be interested in reading that paper as well if you feel like sending it my way?
Regards,
gerald

By chuck meadows (***)

Date 04-05-2007 01:44

Gerald, send me an e-mail at chuck.meadows@avestawelding.com and give me your e-mail address and it will be on its way..

By nosetackle (**)

Date 04-05-2007 07:31

in my previous project ,we have done similar job with ER308 and E308L-15. we had no problem. but the thickness was not more than 19mm
furthermore consumable which has 5FN or below, is very hard to find in market . the consumable companies can not guarantee this level.

Regards

By js55

Date 04-05-2007 14:25

nt,
Your expereience is similar to mine. <5FN stuff can be problematic in supply since everyone is concerned in going the other way for crack resistence puproses. You generally have to purchase SS fillers specifically designed for cryo applications or as Chuck said, go to a fully austenitic 310.
But this introduces and interesting thought. All this fretting over ferrite in SS welds, and yet tons of 310 is welded every day. Increasing amounts of non ferrite fillers are welded every day and in very critical applications of extreme low temp where one would expect microfissures to perhaps be most problematic. Perhaps all this concern for ferrite is a little, just a little, overblown.

By CWI555

Date 04-05-2007 02:06

Given the thickness, it sounds like a job for SAW. However, the proper combination of fluxes and wire for this will be inherently particular on heat input and weld joint geometry.
As far as the proper combination, I'll leave that answer up to Chuck. One other comment though, is this a low temperature application or a cryogenic application? given the impact requirement you have it sounds like cryogenic?

Regards,
Gerald

By jiweiming (**)

Date 04-05-2007 02:18

It requires to do impact test under -196 degree centigrade, impact value not less than 34J.

By CWI555

Date 04-05-2007 03:24

The boiling point for liquid nitrogen is -196C so it will do the trick for cool down. As Chuck and js55 has mentioned already, it can be done with proper consideration.

By js55

Date 04-05-2007 14:31

Here's another little fly in the ointment. By the time you get down to these cryo regimes for impact testing, in order to really verify that you have achieved the test temp you have to do one of two things. You have to either really overcompensate your chill temp (like actually go to -250 of something), or you have to impact test in a refrigerated chamber (and who has those). Even if you take the specimen right outa the refrigerator set it on the anvil and smack it immediately the temperature has increased a lot, even if you get it onthe anvil in just a few seconds. You don't really know where you are.
Just thought I'd toss that in for discussion sake.

By CWI555

Date 04-05-2007 17:14

Your right, and even though it's not techically correct, most outfits who do this type of testing typically have the bottle right next to the anvil and drop it within a matter of seconds and leave it at that. I've only seen it done to the letter twice, and both times were for space based applications from organizations with very deep pockets who can afford the refrigerated chambers and other apparatus. They went one further, the temperature was measured real time, so that they had the actual surface temperature at the moment of impact. 99 percent of us don't have these idealistic conditions to perform these test, and if a lab could be found to do it the cost would be through the roof. Overcompensation is as you say another option, however; for the same reasons you've stated already, it's not accurate in normally available commercial service.

food for thought

By js55

Date 04-05-2007 17:38

CWI555,
I'm not surprised that aerospace is the only place you have seen it. Those guys often go far beyond normal applications. I've never used chamber measures. Few even consider the difficulty. I've usually just advised those involved of the difficulty and that if they wished to be as close as practical to decrease the refrigeration temp.
Committees are beginning to hear greater rumblings of the -425 applications that pop up from time to time being totally irrelevent unless done in a chamber. You just can't get cold enough and place it fast enough to actually get a -425. And you still don't know where you're at.
I suppose an interim measure could be to thermocouple a comparably sized specimen and remove it and measure the temp increase at a given ambient. Of course you could thermocouple the piece you smack as well, maybe something along the lines of what you witnessed.

By billvanderhoof (****)

Date 04-07-2007 05:06

Suppose you found some material that would act as a wick in liquid nitrogen and wrapped the sample in it before immersing the sample. One could then assume that the sample's temperature would remain correct until much of the liquid absorbed in the wick boiled away. I assume that this may add problems in avoiding cushioning the blow being rendered but they are probably solvable. You could also spray liquid on the sample until just before the blow is struck.
Bill

By js55

Date 04-09-2007 13:20

Bill,
I think you have some interesting suggestions, which demonstrates that with some imagination some reasonable measures short of chambers can be utilized. Not sure how your measures would be implimented exactly, but the first step is to be aware of the problem.