the question of lincoln L56 wire

Date 02-13-2014 17:23

Silicon is utilized as a deoxidizer. When the silicon reacts with oxygen in the liquid weld pool silicon oxides and silicates are formed. Being of lighter density, they tend to float on the surface of the weld pool and solidifies as "glass" on the surface of the solidified weld bead.

By Lawrence (*****)

Date 02-13-2014 18:45

Silicon Islands are what I think you are seeing.

Your L56 is an ER70S-6 which uses the silicon as a deoxidizer/scavenger and is particularly effective if there are small amounts of mill scale or very light rust.

Lincoln also makes an ER70S-3 of excellent quality that has a slightly lower content that might suit you. Less fluidity of the puddle is also a characteristic of S-3 fillers when compared to S-6... This may or may not be a benefit to your application.

This is a sales pitch for metal core, but talks about it.
http://weldingdesign.com/mag/wdf_77878

By Smooth Operator (***)

Date 02-14-2014 02:23

Was getting this type of problem when using 75/25.........changed to 85/15 and it disappeared........

By jherrera (*)

Date 02-14-2014 01:49

Hi, i work with lincoln electric in Argentina. The silicate is common to many 70s-6 wires, not only for Lincoln wire. I suggest you to change your gas mixture. Choose one with less CO2, the first problem is the oxygen, less oxygen - less silicate beads... And the second and most important, use L56 suggested procedure (wire feed speed, volts, stick out, and travel speed).

Look for procedures here:
http://www.lincolnelectric.com/en-us/Consumables/Pages/product.aspx?product=Products_Consumable_MIGGMAWWires-SuperArc-SuperArcL-56(LincolnElectric)

Good luck!

By edisonwang (*)

Date 02-14-2014 13:34

my company is always using NR305、outshield 70\ L56 \71M\E7018\E8018\L50\LA100, it have been 20 years old .because my company is a joint ventures .these wires provide from USA factory . but we dont test basic property of these wires .can u provide some property result to me ,for example actual yield strength \tensile strength \elongation\impact

By Tyrone

Date 02-14-2014 12:08

A needle peener will quickly remove the silicon oxide on the surface of the weld without scarring the weld appearance (compared to a grinder).

On a side note....
My colleague experimented on the effect welding over the silicon on multipass welds. No effect on bend tests.

Tyrone

By jwright650 (*****)

Date 02-15-2014 13:57

A small company that I had helped with Welder Quals were having trouble with bend testing because they said that solid wire didn't have a slag system so they could run pass after pass without chipping. I agreed with them to an extent, but they failed more bend tests than you could shake a stick at. The silicon islands would float to the top for a few passes and then get trapped between passes after a while causing the bend tests to fail. They started using a needle scaler/peener between passes and achieved a 100% passing rate from then on.

By js55

Date 02-14-2014 12:54

Not sure how silicon deposits are rejectable through UT. Given we have some excellent NDE guys in here I'd like to hear their input.

By edisonwang (*)

Date 02-14-2014 13:39

i forgot to tell you the shiled gas in using L56,it is 90%Ar/8%co2/2%O2

By cddolan74 (**)

Date 02-14-2014 16:27

i dont see a need for that mix. cut the O2. with your silicon content you should be able to get nice wetting.

By jherrera (*)

Date 02-21-2014 00:58

The problem is the o2 in the gas. Use 75 ar / 25 CO2.

By jwright650 (*****)

Date 02-15-2014 14:01

Jeff,
Any material inside the joint that has an accoustic mis-match from the base material (sound velocity) has the potential to display a reflection on the UT screen.

By js55

Date 02-17-2014 13:02

John,
Not sure what 'inside the joint' means.
If the silicon deposits are not rejectable per VT (and to my knowledge there is no code criteria other than obscuring an RT) why would they be rejectable for UT?
If they are rejectable per VT it would only be per a customer specification not a code requirement, of which, to my knowledge, sil deposits are not even mentioned.
And even if there were a reflector would not the NDT be able to interpret the deposits as the source of the reflector?

By Lawrence (*****)

Date 02-17-2014 13:41

Not sure about UT,

But I've seen silicon islands that are not removed between multi-passes cause failures in destructive testing. Especially with short circuiting GMAW.

They don't "always" burn off as the next layer of weld is applied. And when they don't burn off, fusion is compromized which is readily seen by the type of fractures that occur during guided bends.

If I had the equipment it would have been interesting to do UT on the samples before they were destroyed, to see if the UT caught the defects within the weld (inside the joint) and then verified by destructive testing...

After a few thousand bend tests failing, you start to think about why they fail, how they fail, and what operators tend to do to cause those defects.....

I've seen silicon get pretty thick.

.

By js55

Date 02-17-2014 13:55

Lawrence,
UT for internal volumetric indications as such seems to me ligit. It would essentially be either a slag or a fusion call I would suppose. The confusion I am having is with what I was assuming are surface indications.

By 46.00

Date 02-17-2014 19:31

I'm sure we have had this conversation or a similar one before on the forum. Given that we are working to AWS-
A3.0 gives us this definition:

slag.A nonmetallic product resulting from the mutual
dissolution of flux and nonmetallic impurities in some
welding and brazing processes.

slag inclusion.A discontinuity consisting of slag
entrapped in weld metal or at the weld interface.

Notice it states 'nonmetallic'. Silicon is nonmetallic. Therefore, if a completed weld was offered to me for visual inspection with large amounts of silicon present, I would reject it on the basis that it was a residue from the welding therefore a slag

AWS D1.1 states:

5.30.2 Cleaning of Completed Welds.
Slag shall be removed from all completed welds, and the weld and adjacent base metal shall be cleaned by brushing or other
suitable means.

ASME B31.3 has a zero tolerance for what it calls 'exposed slag inclusions' in welds greater than 5mm 'T'.

By js55

Date 02-17-2014 21:00

Except that a silicon deposit (visually referenced) is not trapped in the weld or at a weld interface. Its on the surface. If its subsurface and detected by UT you would not know that its silicon.
I'm not trying to be difficult, just precise. And trying to understand what basis UT has for determining surface phenomena.
One other point, silicon deposits do not result from the dissolution of flux and nonmetallic impurities. It is a deoxidizer. It results from the chemical bonding of silicon with oxygen. There is no 'fluxing' per se with GTAW or GMAW. And whereas silicon might be argued as being some kind of fluxing agent, it cannot logically be the fluxing agent AND the non metallic impurity. Or it would be fluxing itself. And oxygen might be considered a non metallic impurity but that's a stretch. And if the oxygen is the non metallic impurity what is the silicon?

By 46.00

Date 02-17-2014 22:58

js55,

You have not read my post correctly, silicon on the surface of a weld in any significant amount would be classed as slag. Slag is a no no both by AWS and ASME in the most part.

Check the AWS A3.0 definition of Flux:

'flux. A material used to hinder or prevent the formation
of oxides and other undesirable substances in molten
metal and on solid metal surfaces, and to dissolve or
otherwise facilitate the removal of such substances.
See also active flux, neutral flux, and slag.'

Now check ESAB's description of it's Spoolarc 29S welding wire, this consumable was just picked out of numerous descriptions of GMAW wire, any make or brand have the same propaganda:

http://esabna.com/us/en/products_catalog.cfm?Product_ID=67

"As part of the Elite series, Spoolarc 29S is a general purpose copper-coated solid wire suitable for many carbon steel welding applications using either the MIG/Gas Metal Arc Welding (GMAW) or the Submerged Arc Welding (SAW) processes. Spoolarc 29S contains moderate amounts of manganese and 'silicon to provide sufficient deoxidation 'over light mill scale. Shielding gas choices for Spoolarc 29S in the GMAW mode are 100% carbon dioxide, argon/carbon dioxide mixtures, argon/oxygen mixtures, and other argon based mixed gas blends. In the SAW mode, Spoolarc 29S can be combined with a variety of active and neutral bonded fluxes to achieve better welding performance over Spoolarc 81 wire. Spoolarc 29S is used in a wide variety of applications including heavy equipment, automotive parts, railcars, agricultural equipment, and sheet metal welding."

Flux is a material added to a welding consumable to do something, in this case de-oxidate, the resultant left over is a slag......slag in this case being the undesirable stuff that was removed from the weld i.e oxidants ........Slag left on the surface of a weld is unacceptable, (it prevents complete visual inspection of the weld for a start). Unacceptable levels of slag left inside a weld are unacceptable, the amount which is subject to what standard is being used).

I think you have gotten confused with the part about using UT for determining surface phenomena? I don't think this is viable? I am no UT person so am unsure about this.

By js55

Date 02-18-2014 13:11

46,
Silicon as a deoxidizer is NOT a flux. No more than manganese, titanium, zirconium, or aluminum which is also used for deoxidation (as in 70S-2). Its a deoxidizing element.
It is also NOT a material. You are reading into the definition.
Your reading into the definition to suit your argument also denies and obscures the very obvious terminology used for fluxes such as in SAW and FCAW. There is a reason that FCAW has the F and not GMAW.
Utilizing your argument any GTAW or GMAW wire with any type of element that bonds chemically with oxygen would be considered a flux. This would only serve to cause confusion.

By cddolan74 (**)

Date 02-18-2014 19:16

I know we did this before.
But js55, i dont think you are reading 46 definitions carefully enough. silicon is a deoxidizer and many other things thats benificial to the welding process. I think defining the Oxide, which we know to be a SiO in this discussion can be entrapeed in the weld and be a inclusion and should be removed is a "slag entrapment". there are alloys with lower Si content for this reason as not to add a second operation to the production process. I beleive in a previous thread this was exhausted and what I came out with it is its hard to classify and define everything. In the end, is it undersirable for the Slag or Oxide to remain on the surface of the weld where it can be entrapped on the following pass??

By js55

Date 02-18-2014 19:57

cd,
I would agree that it is undesirable. That wasn't the point.
And based upon the OP we are not talking about an internal entrapment either. Of which the cause would be indeterminative after the fact. Unless during the repair you found unmelted flux or silicon.
We are talking about surface deposits.
My primary argument is that there is a gap in terminology and that we use terms for convenience because we have no others. But that doesn't mean we should not be aware we are using them for convenience. Though my first point was how you could justify rejecting per UT. Which has yet to be answered by the way.

By ssbn727 (*****)

Date 02-19-2014 01:37

I'll sum it up by pointing out the obvious differences between the nomenclature used in Europe as opposed to what is standard terminology here in the USA.
Btw, If you re-read the OP again you will notice that the OP did not mention which code or standard is being used regarding this query so, to assume that we're exclusively referring to or working to AWS standards is not relevant in this particular query... Which is why I propose that we stop focusing on the nuances of nomenclature, and instead focus on answering the OP's query. I mean isn't that a more productive and friendlier way to approach this? :smile:

I'm just saying that life is too short to argue over this - CAPECHE?

Respectfully,
Henry

By js55

Date 02-19-2014 13:53

Henry,
I see it a little different. Personally I think the simplified question and answer paradigm is boring. I enjoy the debates that deal with nuance and detail. And I always learn from them. And it in no way, though it may appear so sometimes, implies from my standpoint any lack of respect for those I am debating with. In fact, I would point out that by the very act of debating with someone I am demonstrating the utmost in respect. I am being challenged and having to work to respond. What more acknowledgement of respect could there be?

By 46.00

Date 02-21-2014 23:44

Henry, I am quoting from AWS A3.0 and AWS D1.1. I have also included ref to ASME were I saw fit. I doubt the OP is referring to EN standards. The easy answer is to remove the deposits before inspection or depositing weld on top of these 'silicon islands'. The 'nuances of nomenclature' are what causes 99% of problems in the engineering field.

http://www.youtube.com/watch?v=zZ3fjQa5Hls

By ssbn727 (*****)

Date 02-23-2014 05:28

Weemarkabull!!! :smile:

By Lawrence (*****)

Date 02-24-2014 13:49

I think I agree with ya 46 for the most part.

The bottom line is that these "silicon islands" appear !

When they appear and are not removed a number of negative things may occur. Paint, fusion, corrosion, inspection etc.

Solid wire GMAW produces more tons of weld metal than all other processes combined.... Yet this phenomina (silicon islands) have not been given a proper attention...

It's one of those "elephant in the room" things.... It's a substantial issue, but the industry driven code bodies would prefer to ignore it, because taking action would be expensive. (mandated code to be obeyed)

So we are left to apply slang terms or try to deal with it within the framework of a lexicon that is intentionally constructed by the code bodies to be unclear on this specific phenomina.

****Edit:
Another welding conspiracy!

.

By 46.00

Date 02-21-2014 23:37

As regards your first point - I'm no UT expert but I would imagine a "Silicon" inclusion would show the same as a slag inclusion or at least as a lack of fusion? I don't see how you would tell the difference between them unless their acoustic properties are very different, I don't know.

I think weld surface deposits of silicon are rejectable as I would class them as slag.

By jwright650 (*****)

Date 02-20-2014 01:22 Edited 02-20-2014 01:32

Jeff,

Read back through my reply...it is more of an explanation that you may be able to detect the silicon islands trapped between the passes in welded joint given that the material velocity will mostlikely be a mis-match for mild steel/silicon.
Now...The acceptability or rejectability of the UT scan would be dependant on where it falls in the Table(6.2-statically loaded or 6.3-cyclically loaded) in D1.1...not sure about other codes in regards to UT. It does not spell out what materials are allowed to be trapped inside the joint...only gives dB ratings/size/length/location acceptale/rejectable criteria.
As for telling what the reflector is inside without actually seeing it...I doubt that I could, maybe other UT fellas could, but I would have someone gouging into a weld if it failed due to silicon trapped inbetween passes.

EDIT

>Its on the surface. If its subsurface and detected by UT you would not know that its silicon.

I read that the OP was having problems passing the UT, that tells me it is not only on the surface, but possibly trapped inside somewhere. The transducer is a wedge(70* mostlikely) and it would be scanned from over on the base material(no silicon islands there), and not directly on top of the joint unless it is a very thin joint.

By js55

Date 02-20-2014 13:21

John,
If it is internal I understand UT has a roll. It is the surface phenomena of which my gross ignorance of UT makes me ask.

By fschweighardt (***)

Date 02-24-2014 15:38

you might get a surface wave to give a return on a silicon island, but I bet it would be virtually impossible to see the indication on the scope, much less interpret it.

By js55

Date 02-24-2014 16:59

Hey Fred,
That's what I would have thought but I don't really know.