Silicon Bronze MIG brazing

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PostPosted: Sat Dec 22, 2018 9:02 am
I picked up a reel of Silicon Bronze MIG wire the other day and have been playing around with it, my Miller machine is set to their recommendation 4-40 for 20ga using pure Argon. The problem I am having is on butt welds, I keep blowing holes, even if I go down to 3.5-35 or 3-30. Filling those holes with Si/Br results in either bigger holes or a stacked up bead. Lap welds are easy and predictable and in all cases the weld is much stronger than the metal itself. All metal has been cleaned before hand, any tips would be appreciated.
Thanks
IMG_1351 (1024x768).jpg

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PostPosted: Sat Dec 22, 2018 1:30 pm
https://www.bing.com/videos/search?q=Si ... &FORM=VIRE

https://www.bing.com/videos/search?q=Si ... &FORM=VIRE

https://www.mig-welding.co.uk/brazing.htm

I've included a few links that might be of help and interest? While you might think a picture of the offending weld is worth a 1000 words, in this instance, a picture of the end of the nozzle, wire diameter, length of wire sticking out and the end of the wire after completing the weld would be of greater benefit. Also a conformation of polarity being used.

To the benefit of the reader, and hopefully in assistance, the size of your power source, the size of wire, and if possible, on a scale of 1 to 10, 10 being the highest, your honest understanding of the process.
I will offer up some sage advice. It's about the droplet. How it forms and transfers. It's not ment to short. It's a globular transfer.
That's why you'll notice in the video links WFS as a variable worth noting.

I'm going to step away with another bit of advice. When you set the machine, run a few beads. While you do, pay attention to the Stick out of wire and it's length.
Vary it.
Same settings, but run a bead with it longer. The gun further away.
Run a bead with it shorter. Gun held closer.
Watch the wire end as it melts. See the effect it has on the droplet. Your looking for a soft splat not a hard split.

Now..think about the effects to that bead by increasing or decreasing a voltage setting, WFS, the droplet formation and transfer, as well how Argon as a shielding gas transfers heat in the arc plasma as magnetic fields play at pinching and squeezing droplets.

One more thing. That one to ten thing. The ten guy also looks at a number of other factors. One is joint design. I'm not saying you can't or shouldn't. I would say a butt joint for a silicon braze joint isn't the best choice when ground surfaces leave little bond strength remaining. Metallurgically speaking, think how strong are two peices of plywood glued at the edges?
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Now...I said that and I'll also say, if the edges are chamfered, beveled back increasing surface area, things improve for the butt joint and strength in such an application.

I see potential, and I hope you see is what I see. In the first video, the gun angle is laid to low. In the second video, I like how buddy gets his arm up, the gun vertical. :goodjob:



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PostPosted: Sat Dec 22, 2018 3:27 pm
Noelc,
Polarity is DCEP electrode +, work clamp -
Power source is 230v, the machine a Millermatic 211, .8 mm Si/Br wire, Argon at 12 CFH
Stick out about 1/2" On a scale of 1-10, a solid 4 and creeping up.
I think I see what you are talking about concerning the distance, I was holding the tip way too close, getting better results now and a softer splat by pulling the nozzle back to .75-1" away from the surface. Now I can see the droplet being deposited. A lot of the repairs I doing at the moment are rust in the middle of a panel so strength isn't so important and I'm trying not to warp the panel with too much heat which is why I thought I would try my hand at Mig brazing.
Thanks for the advice, the pics are after 2 different welding runs.
IMG_1368 (1024x768).jpg
IMG_1365 (1024x768).jpg

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PostPosted: Sat Dec 22, 2018 5:41 pm
"The flow of electrons is termed electron current. Electrons flow from the negative terminal to the positive. Conventional current or simply current, behaves as if positive charge carriers cause current flow. Conventional current flows from the positive terminal to the negative."

This was the last comment I copied in a lengthy reply which caused me to drop a mouse from the arm of my chair and lose the page and my response.

I've run out of time however to repeat it. I'll try and reply again later this evening, in the mean while, drop the voltage and repeat. Then drop it again and repeat. No wiggle, wobble or weave. Straight line start to finish go.

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PostPosted: Sun Dec 23, 2018 12:01 am
noelc wrote:"The flow of electrons is termed electron current. Electrons flow from the negative terminal to the positive. Conventional current or simply current, behaves as if positive charge carriers cause current flow. Conventional current flows from the positive terminal to the negative."

This was the last comment I copied in a lengthy reply which caused me to drop a mouse from the arm of my chair and lose the page and my response.

I've run out of time however to repeat it. I'll try and reply again later this evening, in the mean while, drop the voltage and repeat. Then drop it again and repeat. No wiggle, wobble or weave. Straight line start to finish go.


I mentioned this electron travel thing. Forces of 70 against 30, or 30 against 70? Now, we don't have to get complicated. But if we look at the big ball on the end of your wire and try to explain it away...it's gets complicated.

In my previous post I said turn the voltage down and repeat. The reason why was to hear back what you discovered in doing so.
Over simplifying things... I tend to use what I think is relatable content, not always does it answer a question, some time it's to get the reader to see the topic differently. I ask forgiveness if this is misconstrued as dumbing it down. It's not.

4 is a good number. My buddy Brian swore by it. Anyways...with what you noticed already in this short time, you'll soon be a 6 or 7.

So some of the magic bullet moments.

That big old ball, how did it get there? Time could have been one factor. Electromotive force another.
"a difference in potential that tends to give rise to an electric current." thanks google.

So...depending on your electron theory, me keeping it simple, lets agree that turning up the WFS does nothing more then add more wire.
Can we do that? Or am I going to have to prove you wrong because you heard amperage and think like other processes it turns up heat? If you think more or less that would be great for both of us.

Voltage. The means of force that moves the electrons. I could poke you in the stomach, or I COULD POKE YOU in the stomach. The light bulb is BRIGHTER or dimmer? Is it a LARGE pot of boiling water, or a small pot of boiling water. If I said you had to walk the plank, would the width of the plank make it easier or harder to walk the plank?

https://forum.millerwelds.com/forum/wel ... ials/page3

That's a pretty small wire. Let me know if any of this is making sense, helping or hindering the cause? But again simply stated, you control the size of the droplet, the force it's propelled, with where and when the droplet departs, thru setting to the power source, as well the extension of wire stick out length as you discovered. The resistance. Rebel forces fighting against the Dark side.
Tweak things you must, learn you will. :rotfl:
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PostPosted: Sun Dec 23, 2018 7:59 am
That is certainly a different way of thinking about it than what I'm use to, I can see that I will have to do a lot more playing around with different variables, amperage, speed and height.

[quote=
Over simplifying things... I tend to use what I think is relatable content, not always does it answer a question, some time it's to get the reader to see the topic differently. I ask forgiveness if this is misconstrued as dumbing it down. It's not.


Not at all, linear thought is great but non-linear can help you see a larger picture, I'm good with that and really appreciate you taking your time to help.
So if I'm understanding what you are saying that a higher amperage isn't blowing holes in the work piece then it must be my speed or lack of that is my problem?

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PostPosted: Sun Dec 23, 2018 11:57 am
"So if I'm understanding what you are saying that a higher amperage isn't blowing holes in the work piece then it must be my speed or lack of that is my problem?"

In the drawing I've attached you'll see variables. Your quote mentions two of them. WFS (Amperage) And travel speed.

If I had a foot long sub (roll of wire) and was going to feed it to you (metal plate) how much or little is WFS.
If I feed it slow, you take small bites, easily chew and swallow. If I feed it faster big chunks in a bite, less chew before swallowing. Eventually leading to chocking on the chunks. More or less.

Now, if I had a bunch of you each taking a bite, lined up in a row, how much time I allow for each of you to take a bite, allowing for a lessor or larger bite to be taken, that's travel speed.

How big the mouth is opened is voltage.

On the tech side, you have slope. Squeezing the trigger the wire comes out and arcs the plate, current surges to a peak value in relation to available voltage. Then you have inductance, the time it takes to rise. While these are typically tied to short circuit transfer, as you leave that transfer to a globular transfer voltage range, also attributed in appearance by a lack of WFS, you manipulate thru stick out (resistance) and the effect of the droplet and where it breaks off. In the surface, at the surface, above the surface.

If you thought of that wire like a caulking gun, squeeze and out comes a product, then a consistent squeeze force and steady travel should lay a nice bead wouldn't you think? Why doesn't it? Because other variables are at play.

IMG_6565.JPG


The more you know, the more you understand and the easier it gets. In simple terms again, that wire is a solid that's taken to a temperature of transition to become molten. Like a soft ice cream, how molten does it become is what you control.
Practice, play, experiment. Post the results.
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PostPosted: Sun Dec 23, 2018 6:30 pm
grannyknot wrote:Noelc,
Polarity is DCEP electrode +, work clamp -
Power source is 230v, the machine a Millermatic 211, .8 mm Si/Br wire, Argon at 12 CFH
Stick out about 1/2" On a scale of 1-10, a solid 4 and creeping up.
I think I see what you are talking about concerning the distance, I was holding the tip way too close, getting better results now and a softer splat by pulling the nozzle back to .75-1" away from the surface. Now I can see the droplet being deposited. A lot of the repairs I doing at the moment are rust in the middle of a panel so strength isn't so important and I'm trying not to warp the panel with too much heat which is why I thought I would try my hand at Mig brazing.
Thanks for the advice, the pics are after 2 different welding runs.
IMG_1368 (1024x768).jpg
IMG_1365 (1024x768).jpg



I would shorten the Cup make it even with the Tip where the wire comes out, Also INCREASE your Argon flow from 12 cfh to 30 too 35 CFH!!!!!!
Pics of your welding shows signs of contamination/Lack of Argon Shield.
Your Auto set should be OFF! and USE Manual mode.

Look at this page For tips from Miller for Welding Silicon Bronze
Find your Machine in the Charts "Miller 211" follow its suggestions for Basic set up for BUTT Joint,T joint or LAP Joint settings like
Argon Flow, Voltage, and Wire speed settings for Wire diameter being used.

https://www.millerwelds.com/resources/a ... ing-basics

Your welding Technique should be the same as used for regular steel welding.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Wed Dec 26, 2018 5:39 pm
So not great but much better than before, Doright, thanks, bumping up the gas pressure made a big difference. Far right are skip welds joined together, middle was two separate welds and the far left was an attempt to do the entire bead without lifting and without blowing, so I ended up going too fast. There is good penetration to the other side on all of them. 16ga, 3 voltage, 40 wfs, 30 cfh. Now I need lots of practice.
IMG_1376 (1024x768).jpg



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PostPosted: Wed Dec 26, 2018 9:19 pm
At least the bead looks nice and Golden now, Look at that chart 16 gauge should be welded at 4 volts too 4.5 volts depending on wire diameter .030 or .035 ? that kinda explains the Proud bead but I would guess its a combo of Traveling to slow as well as too cold. Try increasing your voltage and picking up your travel speed, Also LOOSE the GAP between your pieces Your pieces should BUTT Together Tightly! with NO GAP!

Also Your "AUTO SET" is turned off and machine is in Manual correct?

Make up a couple more 16 gauge pieces but them up tight try welding with a 3/8" too 1/2" stick out get in there close and run a good 2-3 inch Bead with the metal butted up tight.
Practice and please post pics when done.

One more thing are you PUSHING or PULLING your Bead? if your Pulling or dragging the bead try Pushing you can do either one really But stick with one or the other when learning.

Pushing will make you a better welder with more consistent welds with time and practice.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.
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