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Up Topic Welding Industry / Technical Discussions / Silicon deposition in weld bead
- - By Bhargav Date 05-12-2019 16:21
I am working in a welding line. We are using ER70S6 electrode. We are having high silica deposition in the weld bead. We are currently using a brush to remove the silica.

Is there anyway to reduce the silica deposition. We have already tried optimizing the silicon and manganese content in the electrode. Any other ways to reduce silica deposition??
Parent - - By 803056 (*****) Date 05-12-2019 19:39
If you are seeing silicon oxides on the surface of the weld, it would be the result of the silicon deoxidizer reacting with oxygen to mitigate porosity in the weld. Reduce the oxygen and you'll reduce the silicon oxide.

Parent - By Bhargav Date 05-14-2019 17:13
We are using Argon C02 mixture as shielding gas. There is very little oxygen
Parent - - By jwright650 (*****) Date 05-13-2019 14:14
May try using ER70S-3, it has less deoxidizers but it won't tolerate mill scale and contamination as well as the ER70S-6.
Parent - - By Lawrence (*****) Date 05-14-2019 21:27
I think Al has given you the true nature of the ER70S-6 and what it's doing.

But why it's doing what it's doing can be driven by many factors, or a combination of factors.

Many questions must go before quick advice...  And buying electrode wire is probably not going to solve the issue..  It's not the cause.

The deoxidizers are just doing their job...   What is brining them out to do it is the question you must answer.

A one control at a time root cause analysis will get to the bottom of your issue, but it may take some time and patience.

How many welding machines are showing this problem?

Some of them?   All of them?   Are there differences between one unit and another unit?

Are all the welding machines supplied by the same gas manifold system?

Are the machines supplied by bottles?

Semi automatic hand welding or Robotic?

The silica (glass) on the surface of your weld can come from many sources...
Oxygen from a cracked O-ring in your mig gun
Oxygen from too low shield gas flow
Oxygen from too high shield gas flow
Oxygen being sucked into delivery line via leak from main supply
Oxygen being sucked into delivery line via intermediate fitting
Oxygen from excessive gun angle (vortices)
Oxygen from excessive travel speed
Oxygen from shop air flow disturbances
Oxygen from excessive mill scale
Oxygen from rust
Spatter in Nozzle disturbing shield gas flow

There are a lot of ways to isolate your system and begin to test your equipment one thing at a time...  The key is to inspect and change just one thing.   

Has the work always had silica deposits or is this something new?

If it was my circus and those were my monkeys I would probably do the following.

Get clean base metal and make welds with correct gun angles and travel speed....  Glass yes or no?

Check O-rings and do soap check on all visible connections on gas system..  Shut down shop and listen for leaks... Make welds. Glass yes or no?

Once the simple things like gun angles and obvious leaks are eliminated...  If you still see glass you need to get a bottle of gas separate from your regular supply and connect directly to the machine...    Glass yes or no?

I'm willing to bet you have a gas issue one way or the other....  Having lived through several similar problems in the past.

A little island or two every once in a while is reasonable... When it is found in the toes of the weld and when it is impacting paint quality you have a gas problem... 

If everything is good and clean the ER70S-6 will not have silica islands on top of the welds...  The stuff only comes up when it is attacking the oxygen as Al mentioned.
Parent - - By 803056 (*****) Date 05-14-2019 22:13
Thanks for confirming my suspicions Lawrence.

Parent - - By Lawrence (*****) Date 05-15-2019 00:28
Hi Al !

I’ve been wanting to respond to this question for a couple days but just didn’t have time to explain what I was thinking about root causes.

It’s certainly something I have to deal with from time to time with a couple hundred GMAW units on my watch.

The glass/silica is usually accompanied by that lovely red-brown smoke at the toes... Oxygen contamination in MiG gas almost always has the smoke!  

Like this :)
Parent - - By 803056 (*****) Date 05-15-2019 14:25
If you have the silicon oxide on the weld surface, the silicon has performed its task, i.e., deoxidized the weld to mitigate porosity. Eliminate the source of oxygen and you eliminate the silicon oxide.

Looks to me like the mixed gas would fill the roll of providing oxygen to the weld pool. There are other sources as mentioned by my friend Lawrence.

Parent - - By Lawrence (*****) Date 05-15-2019 18:47
We may be going down the rabbit hole here on this Al... 

But just for the sake of conversation...

Our Euro friends across the pond absolutely love 80/20 Argon/Co2 shield gas for GMAW and GMAWP

This gas is just barely enough to produce spray transfer with .035 but it will with regular S6 or S3 solid wire.   The welds produced on clean to moderate mill scale are absolutely pristine … No silica islands.

One might think that with the higher Co2 percentage that there would be a greater oxidation potential.. and there is.. But not so much as to bring the glass to the top of a properly shielded GMAW deposit.

Also consider plain old short circuiting transfer with 75/25 or even 100% Co2..  With proper gas shielding and technique you can make lovely welds with no glass/silica in both short circuiting transfer or globular transfer modes.

The islands typically appear when an excessively high voltage is used in spray transfer..  A hiss is heard instead of the consistent crackle....  or gun angles are off. or one of the other above mentioned problems occur.

The only time I've seen a problematic amount of silica islands under excellent conditions is with GMAW on moderate mill scale and 95/5 Argon/Oxygen weld gas...   I hate that mix but some folks still use it.
Parent - - By 803056 (*****) Date 05-15-2019 20:40
I'm trying to remember a GMAW weld that didn't have some islands of "glass" or glass along the weld toes.

Parent - - By jwright650 (*****) Date 05-16-2019 11:29
Me too....always see at least little islands in the middle of the cap about the size of of the diameter  of wire being used.
Parent - - By Lawrence (*****) Date 05-16-2019 14:55
Ok... yeah

A little

Maybe a little hyperbole on my oart
Parent - By jwright650 (*****) Date 05-16-2019 17:09
Up Topic Welding Industry / Technical Discussions / Silicon deposition in weld bead

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