Is 316L compatible with ER320 ?

Date 07-06-2007 03:01 Edited 07-06-2007 03:05

I have never had any first hand experience with ER320 electrodes, But what comes to my mind is solidification cracking. Stainless requires a certain level of ferrite when cooling, too much or too little can cause cracking during solidification. One way to check ferrite content is to use a Severn gage or electronic ferrite meter with a WRC diagram. What I don't understand is why they don't specify a 316L or 316LSi. There are guys with more experience on stainless that use this forum, I would be curious to hear what they say.

By chuck meadows (***)

Date 07-09-2007 15:34

Tracy,
You can give me a call if you like, but I think the problems lies within one or both of two things.
ER320 is a non-ferritic material, and can be subjected to solidification cracking if not careful. ER316L generally has enough ferrite to prevent centerline cracking unless the parts are of difference thicknesses and the cooling rate is sufficient to affect the cooling of both parts.
Another thing, and this doesn't happen very often, is that improper grinding techniques can cause tensile stresses that can propogate into centerline cracking.
Again, if you call we can discuss exactly what you're doing and probably come up with a reasonable explanation as to the cracking issue.

Chuck

By prasad

Date 07-09-2007 16:57

Besides the above this may help ( Quoted from ISSF Belgium )

Austenitic steels do suffer from hot shortness i.e a tendency to crack at high temperatures . This is attributed to a number of causes both during and after solidification . Of these probably the most important is the sequence of events during solidification. Sulphur has low solubility in austenite so that if austenite is the first metal to solidify sulphide inclusions will seperate out and be pushed ahead of the advancing crystal to form a line of weakness when two crystal faces intersect.
If on the other hand ferrite is the first phase to crystallise out the sulphur remains in solution and there is no line of sulphide inclusions.
summary of three supporting charecteristics that will promote cracking
Austenite - austenite boundaries are more easily wetted by liquid impurities than austenite / ferrite boundaries and will therefore be weaker during contraction.
Large grain size
Cracks can easily pass through the single phase structure.
In addition to these points bead contour and weld constrain must also be regarded as contributing factors although overall weld constraint should not markedly affect hot tearing.
To overcome cracking of this type the ideal is to control chemical composition so that solidification occurs through the ferrite zone as well as bead shape.
If the composition of the weld is chosen to give a completely ferritic structure it is found that there is excess ferrite in the final weld so a compromise must reached. The most appropriate composition to provide least cracking results in around 4 - 12 % ferrite in the weld deposit , more usually at the 4- 6 % at room temperature.

Tracy there is a lot more but I am not very fond of typing . In case you are interested I will email you the pdf document.

By alumtig (**)

Date 07-19-2007 13:08

I would very much be interested in reading the pdf. if you would be so kind as to forward it to me. I am constantly faced with stainless welding issues of all sorts. Thats why I'm so grateful for Chuck and all his input, and guidance in this area. I appreciate all the responses that I've recieved.

Tracy

By alumtig (**)

Date 07-19-2007 13:05

Hi Chuck,

Thanks for the reply. Sorry to take so long to get back with you but I got jerked out of the shop and have been traveling around the state for the last 2 weeks. I'm still working on the tank though and have now started subarc welding the outside, Wd ended up welding the inside with ER320 electrodes as the GMAW was a nightmare. We backgouged the outside by grinding and then rooted the outside with 316L flux core. Thats when the cracking started. I was out of the shop most of the time, and the guys just dept plugging along I had them switch to a larger diameter wire and adjust thier settings. At some point things apparently turned around because by the time I returned the root passes were completed. My biggest fear is that we still have to do spot RT and my fingers are crossed on that one. This vessel is called a prenuetralizer and my assumption is that it will contain sulfer, however I'm not sure. We get stuck with a lot of this overalloying thing from the chemical plants that we do work for. I'm still playing catch up from being out of the shop and have a lot of issues to address before I'll have time to sit down and give you a call but I will. Thanks again.

Tracy

By MBSims

Date 07-09-2007 22:05 Edited 07-09-2007 22:26

I have welded with ER320 and learned the hard way that it will crack like glass if the heat input is too high. It is not like the typical 300 series weld fillers. Forget the austenite-ferrite arguments. Composition is nominally:

Cr - 20%
Cu - 3.5%
Fe - 36.5%
Mo - 2.5%
Nb - 3.5%
Ni - 34%

The 300 series stainlesses are typically 18Cr-8Ni with Mo, Ti or Cb additions. ER320 is used for welding Alloy 20 (Carpenter 20). We use it in sulphuric acid piping for water treatment plants. I don't see what your customer is gaining by using it for 316L base metal (other than higher cost and pain in the rear to weld). You will have to limit heat input to 35,000 joules maximum to keep it from cracking and no preheat should be used. Remember, heat input (in joules) = (volts x amps x 60) divided by travel speed (in inches per minute).

Here's a link for welding technique for Alloy 20 that should help:

http://www.alleghenyludlum.com/ludlum/Documents/al20%20(053106).pdf

By js55

Date 07-11-2007 19:04

I'm a little perplexed as to the choice of 320 as well. I suppose if 316 is good 320 is better. Its a bigger number. 321 and 347 are even better, and Alloy 59 or 122 wouldn't do well at all. OK, enough of the sarcasm.
320 was indeed originally designed for sulphuric acid service (its the Cu). It is generally considered a super austenitic. The base metal it is generally applied to is actually found in non ferrous specifications (ASME IIB for example). I've never figured this one out, though its chemistry is a bit of a fence sitter. And a clue might be that its chemistry is quite close to Alloy 800, more than twice as good. OK I'll stop.
It will crack as Marty made quite clear (mostly due to the Nb-same as Alloy 625 or 347 SS), so heat input control is critical. But the funny thing is, even at low heat regimes microfissures are still present, yet there is no history of failures due to these microcracks (not those on a scale Marty is talking about however). The LR version has greatly improved the crack tendency.
But in the end, I can think of no reason off hand that it won't weld well to 300 series SS's with the proper precautions. If I were you I'd take chuck's advice and send him an email

By MBSims

Date 07-12-2007 03:11

Yes - what he said.

It is also interesting that the Alloy 20 base metal is a P-No. 45, nickel base alloy, but the ER320 classification is in AWS A5.9 with the other "Bare Stainless Steel Electrodes and Rods" and is a F-No. 6. It would seem better to move it to AWS A5.14 and classify it as F-No. 45.

By js55

Date 07-12-2007 13:27

Marty,
Yeah, this is proof that even though the A5 guys and the Section II materials sub group guys may be having coffee at the same cafe's this subject seldom comes up. Or, I'm not sure that they can really make up their minds where it belongs. Understandable. The fact that there is now a 324 (Alloy 24) and a 326 (Alloy 26) based upon the 320 chemistry might tend to drift it towards exactly what you have recommended.
How important is it? Probably not very, if you deal with this stuff regularly. But it does catch people by surprise.

By cryogenicshaun (**)

Date 03-27-2008 13:44

What about using ER320 SAW for overlay? I submitted an overlay procedure for this Clad vessel, Backing is SA516-70, cladded with Alloy 20. I assumed I could get away with 316L wire, but that got shut down, do you recommend ER320LR for this. I looked on the ESAB website, they got tig/mig, i need sub-arc, to cover a lot of ground faster, that i did not come across. Can you help?

By js55

Date 03-27-2008 14:02

Offhand I see no reason why 320 could not be used for overlay but you need to be cognizant of your dilution and final chemistries and whether or not it will hold up under service intended. In other words its not so much a welding isssue as an engineering issue.
The possibility exists that you may have to two pass it to get the right final chemistry in which case you may be better off with a nickal alloy and the ability to one pass. Being able to one pass while maintaining final chemistry mins and good fusion are the most important things with overlays. Sometimes its better to pay more for the filler alloy and be able to one pass.

By cryogenicshaun (**)

Date 03-27-2008 14:54

What do you mean by getting the right final chemistry? Do you mean 320 has a different chemical comp. than alloy 20?

By js55

Date 03-27-2008 15:30

When you do overlays you will get dilution from the substrate. This dilution will reduce the chemical composition of the alloyed filler so that the chemsitry of the filler when it starts will not be the chemistry of the final weld layer at completion. The final chemistry is what will be exposed tothe corrosive medium and is whatneeds tobe ocnsidered.
For example: if you have 20% nickel and you weld on carbon steel with 50% dilution you will end up with 10% nickel, since half the weld deposit will come from the substrate and half will come from the filler.
This is why its critical to minimize dilution as much as possible. The problem is making sure you maintain good fusion as well. This is the trick of overlays.

By cryogenicshaun (**)

Date 03-27-2008 16:39

Makes sense, when you break it down like that, i appreciate the advise! I do have one more thing, should you layer, bottom being 316L and top layer being 320? or only use 320 all the way through?

By js55

Date 03-27-2008 17:13

It really depends. Start with the chemistry you need to end up with. Consider what process you are going to use. Again. Its dilution. Do some rough dilution calcs to give you some idea of where you might end up. To do overlays efficiently you can't escape engineering.
SAW will hit about 50% generally though you can control it lower with practice.
SMAW will be generlaly 35 to 50. Pulse GMAW can get as low as 15%. Trying to get much lower than that with fusion processes risks lack of fusion.
Often you can go with cheaper alloys as the first pass. Similar to what you're asking. 309 is popular. One pass may be even cheaper n the long run. If you're running two passes then you have calculate two regimes of dilution. But keep in mind also to add a little complication when you run beads side by side you will actually get partial substrate partial prior beads to calc as dilution.
The best way to do it is run an actual test and then PMI. That way you don't have to mess with calcs and trying to estimate dilution from bead cross sections. Limit your parameters to limit your dilution.

By cryogenicshaun (**)

Date 03-27-2008 17:48

Does 130-140 amps, 28-30 volts, 11-15 ipm sound low enough for GMAW?
What about SAW? Sorry for all the questions, this Alloy 20 is whooping my * * *

By js55

Date 03-27-2008 18:47

Sounds low and fast enough. Voltage is a bit high. But if the arc is stable it can work for you. The higher the voltage the less penetration generally. The less penetration the less dilution.
Alloy 20 can be run at about the same parameters as the 300 series SS's on the low side. So if you have procedures for 308/309/316 take a look at those. Or better, nickel alloys.
Run a test. Look at your filler cert (needs to be actual) then PMI the deposit. Compare the two and you will know your dilution.
SAW is the same concept.

By cryogenicshaun (**)

Date 03-27-2008 18:58

Thanks a million, this is the second pinch you got me out of, i will drop my volts to 15-25, i figure i will be golden then!

By js55

Date 03-27-2008 19:54

Make sure you distinguish as to whether or not you wanna run in spray or short circuit. Short circuit will give you less pentration and less dilution but a lot of customers are not too fond of that transfer mode. And if you test it and your dilution is good you can think about kickin it up a bit for production and fusion sake.