Mig brazing!!!!!!!!!

[onthames]

I picked up a Kempii minarcmig evo 200 today for a good price and found out it has a mig brazing mode.... So I did a bit of research. Turns out modern cars are joined together with mig brazing as the high boron steel loses its strength from the heat of normal welding... The wire is expensive, and you have to use pure argon, but I'm going to give it a go and report back. The results look fantastic and for non structural areas seems IDEAL.

[steve_k]

its something i'm keen to learn but the costs put me off a tad.

post up any results you have for us to have a nosey at.

[martauto]

I picked up a Kempii minarcmig evo 200 today for a good price and found out it has a mig brazing mode.... So I did a bit of research. Turns out modern cars are joined together with mig brazing as the high boron steel loses its strength from the heat of normal welding... The wire is expensive, and you have to use pure argon, but I'm going to give it a go and report back. The results look fantastic and for non structural areas seems IDEAL.

Go for it mate and we really DO need a lot of pics for this new adventure

Mart.

[onthames]

its something i'm keen to learn but the costs put me off a tad.

post up any results you have for us to have a nosey at.

The wire is very expensive but in terms of gas I'm using argoshield light which is 95% argon and may be ok for mig brazing as well - will give it a go before I go with some 100% argon.

Welding thin bodywork material uses very little wire anyway so although it is more expensive it's not like I'll be going through a reel of it a week. I think the cost may be outweighed by the fact it saves time as it's much faster (as it's colder so you don't have to keep waiting/cooling) and much easier to grind so there should be significant time savings

Will post some results!

[flybynite]

Quite a few bits of the E30 are brazed from the factory, roof skin corner joins and around the boot. Brazing is not as strong as weld gives a bit more flexibility so is used in the places that flex. TIG uses different rods to Oxy but gives pretty much the same effect.

Not a replacement for weld but can be really useful for joining difficult metals together although these days I use epoxy which was not as common when I learned to braze. Braze looks better than epoxy if done well though.

[onthames]

Quite a few bits of the E30 are brazed from the factory, roof skin corner joins and around the boot. Brazing is not as strong as weld gives a bit more flexibility so is used in the places that flex. TIG uses different rods to Oxy but gives pretty much the same effect.

Not a replacement for weld but can be really useful for joining difficult metals together although these days I use epoxy which was not as common when I learned to braze. Braze looks better than epoxy if done well though.

Have spoken to a few and seems that mig brazing can be a replacement for welding in non structural areas. Say a patch in a floor pan for instance. It can be mig brazed in no problems at all apparently. Basically anywhere thats thin sheet (non structural) can be mig brazed.
https://www.millerwelds.com/resources/a ... ing-basics
https://www.repairerdrivennews.com/2016 ... onze-wire/

[flybynite]

Have spoken to a few and seems that mig brazing can be a replacement for welding in non structural areas. Say a patch in a floor pan for instance. It can be mig brazed in no problems at all apparently. Basically anywhere thats thin sheet (non structural) can be mig brazed.

Those links are mainly on about modern cars where brazing is used to join the various different boron steels they have in the panels of a modern bodyshell. Structural elements can be brazed if designed that way, like the E30 roof.

Anything non-structural can be repaired however you like, lots of people would say that fibreglass and filler would be no problem if done properly but it is not how I would do it. Floorpan is structural in a monocoque like the E30, personally I would weld it.

Having a differing metal in a panel can induce its own distortion due to different rates of expansion and it will cause problems if you need to planish the panel after. You also get problems if you need to do a weld repair over a panel that has been brazed because all the braze needs to be completely cleaned off to weld.

You may end up needing a spool gun because some brazing wire can be too soft, like aluminium wire, and snags in the feed rollers. Helps to keep the torch lead as straight as you can. Personally, if I can't use Oxy I prefer TIG brazing as it is more controllable.

Useful thing to have though but as I said above not really a replacement for a good weld.

[onthames]

Have spoken to a few and seems that mig brazing can be a replacement for welding in non structural areas. Say a patch in a floor pan for instance. It can be mig brazed in no problems at all apparently. Basically anywhere thats thin sheet (non structural) can be mig brazed.

Those links are mainly on about modern cars where brazing is used to join the various different boron steels they have in the panels of a modern bodyshell. Structural elements can be brazed if designed that way, like the E30 roof.

Anything non-structural can be repaired however you like, lots of people would say that fibreglass and filler would be no problem if done properly but it is not how I would do it. Floorpan is structural in a monocoque like the E30, personally I would weld it.

Having a differing metal in a panel can induce its own distortion due to different rates of expansion and it will cause problems if you need to planish the panel after. You also get problems if you need to do a weld repair over a panel that has been brazed because all the braze needs to be completely cleaned off to weld.

You may end up needing a spool gun because some brazing wire can be too soft, like aluminium wire, and snags in the feed rollers. Helps to keep the torch lead as straight as you can. Personally, if I can't use Oxy I prefer TIG brazing as it is more controllable.

Useful thing to have though but as I said above not really a replacement for a good weld.

Apparently a mig braze done correctly will offer around 70% the tensile strength of a traditional mig weld. I've been speaking to someone who uses brazing wire in this exact same machine no issues so hopefully don't need special rollers/spool gun.
I agree with you about needing to weld in future though, that is a potential issue with brazing.
Personally from the tests I've seen and talking to various people I wouldn't have any worries using it in the floor pan. Miller states that a mig braze on thin sheet will be stronger than a mig weld. I'm not sure how they've come to that conclusion but Miller are quite well known so it would be odd for them to say something completely wrong.

What I don't understand though is if it can be used structurally for high boron steel why can't it be used structurally on normal steel? Surely if the braze is the weakest point in both applications, it should be applicable to both? Personally I'm excited about mig brazing for repairing rust with patches. It grinds fast, joins the panel faster, no chance of blowing through and apparently less distortion. I will report back how much of this is true though!

[flybynite]

What I don't understand though is if it can be used structurally for high boron steel why can't it be used structurally on normal steel? Surely if the braze is the weakest point in both applications, it should be applicable to both

That will be because it has been designed to have that method of joining with the correct overlap, length of weld and point of failure taken into account. It is not specifically boron steel that causes the problem, it is the fact that they use so many different steels in one body shell and joining dissimilar metals is what brazing is good at doing.

Big difference in what exactly you are using to braze. Nickel/brass has different uses to silver/brass and variations between.

We will have to agree to disagree on the floorpan, brazing those areas is not something I would do personally but in reality, small patches are not probably going to cause an issue no matter how they are fixed.

[DanThe]

Miller states that a mig braze on thin sheet will be stronger than a mig weld. I'm not sure how they've come to that conclusion but Miller are quite well known so it would be odd for them to say something completely wrong.

I expect there are a few reasons, thin sheet gets burned very easily when welding so the thickness next to the weld can easily be reduced, you often see this on less than perfect tig welds where it burns into the material. There is also the hardening effects of the welding heat which increases brittleness. Exact same reasons why most of a body shell is spot welded together

The mig braze puts less heat into the surrounding material which is why its a lot more suitable for a body shell than TIG or gas welding in my opinion

[Tzantushka]

The mig braze puts less heat into the surrounding material which is why its a lot more suitable for a body shell than TIG or gas welding in my opinion

Correctamundo.
Lower heat, smaller Heat Affected Zone.
Important for thin gauge sheet.
And especially important for high strength steels that are susceptible to embrittlement with no post weld heat treatment.
But having said that a good MIG/TIG weld with the right settings can be better than a shoddy MIG braze.

More importantly we need pics!

[onthames]

The mig braze puts less heat into the surrounding material which is why its a lot more suitable for a body shell than TIG or gas welding in my opinion

Correctamundo.
Lower heat, smaller Heat Affected Zone.
Important for thin gauge sheet.
And especially important for high strength steels that are susceptible to embrittlement with no post weld heat treatment.
But having said that a good MIG/TIG weld with the right settings can be better than a shoddy MIG braze.

More importantly we need pics!

couldn't find any wire for it locally so had to order in, should be here in a few days. I'm very excited to try it out. I have some 0.8mm sheet to try it coming aswell

[onthames]

Wire arrived and a video will be coming soon

[martauto]

Wire arrived and a video will be coming soon

This will be very interesting to see , is it restricted to just steel ??

Mart.

[onthames]

Wire arrived and a video will be coming soon

This will be very interesting to see , is it restricted to just steel ??

Mart.

Nope, you can braze any metal pretty much

Here's the video: