� Gas Brazing Technique

Welcome to Weld.com.

last time we did some brazing, never.

Let's do some brazing today.

You wanna?

I've got a product over here,
it's by a local company, local vendor.

It's called, LF BFC and it is a low
fuming bronze type application here.

It's got the flux on the outside.

I like using this stuff for
general repair, but

I wanna demonstrate just some technique.

When I tack these up I wanna
use quite a bit of gap.

And the reason I wanna do that is because
I wanna show you some heat sensitive.

If I just poured the heat in here and
stuck this rod,

then I expect this to just fall through
the backside, we don't wanna do that.

So I wanna do this exercise of
actually controlling our heat.

I do want the penetration,
I want this to show on the backside and

I also wanna fill this on the front.

It's an outside corner joint but
it's gonna have gap in it, so

I wanna fill this up enough that
it's nice and round up on top or

at least fused along the edges here.

So let me get some gear on and
we'll, we'll put some space in this.

When I tack these, I'll probably light the
torch and put a big old dot out here and

bring it out a little bit and
then I'll get a magnet, and

I'll have this held up here
where it's got some gaps.

I'll fuse these parts together, but

I do wanna show probably about
an eighth of an inch of gap.

I know that sounds big for 316 plate but

again I'm trying to show a couple
of exercises here of control, and

how this stuff flows and everything,
and how to manipulate the torch.

So old school stuff.

I like doing brazen.

I do a lot of repairs on
various equipment and

one of the first things
that I consider is brazing.

I always do for some reason probably
because I just like it so much.

So, let me get my stuff on,
I'll be right back.

Welcome back.

I have these tacked,
I have 316 plate and I went ahead and

put 332 gap, maybe a little open there.

I don't think that's an eighth of an inch,
I'm gonna call that 332 and

it's pretty good size gap if
you can see that on camera.

So the attempt here is,
I've already have some glass showing here,

and this glass is an end
product of the flux.

Could we use a bare wire and powder flux?

Sure.

Maybe we can demonstrate
that in another video.

This one, I wanna use this product here,
which is the low fuming bronze product,

has the flux already on the wire,
it's just real convenient.

So I'm gonna start out and
I'm gonna start heating this up.

So what's the, there's brazing and
there's welding.

So what's going on here?

How do we make a bond with brazing?

Brazing is generally 840 degrees and

above but
not melting the parent metal, Okay?

So the filler wire is gonna
melt at around 840 and

it's gonna bond by what we
call a capillary action.

I have cleaned these plates,
they're rusty down here, but

they're clean down to pure white metal.

The flux will pre-clean the surface and

by this capillary action it will
make a bond into the parent metal.

It wets into the parent metal and
it sticks and bonds to it.

Soldering is 840 degrees and below, so

we start talking about these
concepts of brazing and soldering.

What can you do with them and the alloys?

It gets kind of interesting when you
actually look, see what's in them and

how they melt, and how they bond, and
what you can actually do with them.

And then again how strong they are.

That's what's amazing to me is how
strong this stuff actually is.

So let me light a torch here and
I'll be right back.

I may put my dark shield on because some
of you ding me pretty hard on not wearing

a dark shield.

When I did the brass tree showing
how to manipulate this stuff, so

I may wear my dark shield here.

Be right back.

I'm using an OTT tip, and

my oxygen pressure is set about 4 pounds,

my acetylene pressure is
set about 3 pounds 3 PSI.

My torch angle is about
2030 degrees point or

20 degrees pointed forward.

And you'll notice that I'm
taking it out of the pool here.

This is liquid solid.

So and the reason I'm doing
that is because again,

as I said when we did the intro,
if I just left this in there,

it would probably fall through to
the backside and kinda make a mess.

It'd be too much on the backside,

I'm trying to get this to

round, up slightly.

So I wanna fill it in, but
I don't want it to drip through.

I want it to show

on the back side

just like amperage

and voltage.

When you're wire feed welding,
you can turn things up.

How about stick welding?

Could I use a bigger size wire?

And a bigger tip and more pressure?

Sure.

I would probably do these manipulations

a little quicker, and
this is a little slow.

But again,
I'm trying to show this technique.

I remember when I first started welding,

very first thing we did
was oxy acetylene welding.

Learn how to manipulate the pool and
the filler wire.

I have laid the filler

wire a little lower.

Now every time I introduce the torch,

it may look like I'm melting the wire
with the flame, and I'm not.

I'm creating a weld pool first.

I'm leaving it right on the leading edge.

I teach this class in my program.

I teach oxyacetylene welding,
brazing silver soldering.

Right alongside the introduction
to tig welding.

If you think about it,
it's the exact same hand

eye coordination,
filler wire, heat source.

I think I wanna leave

this open at the end

just to show you what

the original gap was.

I'm gonna do a little remelt here.

Saw a couple of bug holes right on
the surface that I didn't like,

so I went ahead and
just remelted them slightly.

Could I remelt this whole thing and
reshape it?

Sure, but then I take a chance of
all of it dripping through again.

I'm gonna go quench this off and
I'll probably leave it before I buff

it off with the wire wheel or
whatever we do to clean it up.

So let me go quench this off
because it's saturated with heat.

Be right back.

Welcome back.

I finished this part.

I went over and quenched it and I very
lightly touched it with a wire wheel

just to get this excess of flux and
glass off, and I did the same on the back.

We could have gone a little bit hotter.

We're showing that we melted
some on the backside.

We didn't get through as much as I
would have liked for a demonstration,

but I'm pretty sure you can see this.

We've gone just a little bit more in heat
and let it fall through a little bit,

it would have bonded on the backside.

What came through on the back was
it really looks like a glass.

And so, I mean, when it solidifies,
you can knock it off,

you can chip it off,
I hit it with a wire wheel.

Again, we could have gone a little hotter,
maybe a little more aggressive.

I just wanted to show this
technique of filling this thing up.

You can see some dark
discoloration spots in here.

I didn't hit this with the wire wheel
because this is soft enough that it will

re-arrange the patterns in here.

I've left these ripple patterns down
here at the bottom of this part.

I went ahead and hit it with
a flapper wheel with a 40 grit.

I believe it was just to blend this and
sand this over.

I mean, this thing looks pretty nice,
very slight bug holes in it,

which is kind of normal.

You can go back and melt those out.

You could sand this and polish this off,
and it just look, it looks like gold,

It's cool.

So we've done some projects where
we're putting some stuff together and

we get that color differential.

You can play around with this and
weld some,

some other types of material
other than carbon steel.

I have my students
memorize chemical symbols,

all kinds of other technical data.

They think they come in here and they just
get to strike an ARC, and that's not.

So we need to know some things,
and we need to know about

35 elements of the periodic table for
chemical symbols.

And right here they are technical data.

We've got a melt point of about
1620 Fahrenheit, 882 Celsius.

Again, I said brazing is 840 and
above, but

not to the melting point of carbon
steel that we were welding on.

So this says that the nominal,
let me back up.

It says to pre-clean the joint,
bevel heavy sections, preheat broadly,

then concentrate oxy fuel neutral
flame into the joint area,

melt some flux off the end of the rod so
it'll be activated and

it gets down in around the parent metal.

And then you can start
dipping the alloy and

melting the alloy like
we demonstrated here.

The technical data.

The nominal analysis says Cu 58%.

So what's Cu?

It's a chemical symbol for copper.

And Sn is 10.1%.

Mn is manganese, 0.040%.

Fe is ferrous iron, 0.75%.

Si is silicone, 0.1% with a Zn balance.

Zn is zinc.

So now you know what chemically
you're working with here, and

that is typical of all filler metals.

I don't care if you're looking
up a stainless electrode,

you're gonna be given the chrome,
the moly the nickel, the carbon content,

anything, it's all gonna come to you
in chemical symbols I have not read.

I can't remember looking up a technical
spec of something that hasn't,

whether it's a base metal or
a filler wire.

I can't remember looking it up,
having it spell out chromium,

or carbon, or nickel, or
molybdenum, or whatever.

Every one that I've ever read has been
given to me in a chemical symbol fashion.

So anyway, I hope this was fun.

We'll do some more brazing
demonstrations and we might do.

Hopefully, we can dream up a project
where we can braise it together.

I know in the past that we did
a brass tree and it was an exercise of

manipulating this wire, and
building this tree, and starting out and

going all over the place,
which is a really good exercise for

learning how to manipulate the torch and
the heat.

So I hope this helps.

Thanks for watching our videos.

Bob Moffett with Weld.com,
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New videos come out every Monday.

Thank you.