brazing problems

[star882]

I'm having some problems brazing with a propane torch and Dynaflow. I was able to get it to work when the connection is about 6cm away from the compressor (used as a vacuum pump). However, when I tried to braze a connection 4cm away, I had to reheat it several times to get a leak-free connection and it ended up looking as ugly as Bill Gates.
Should I get a MAPP torch? Or is there something I'm overlooking?

[Marvin]

are you meaning the compressor fittings ?
propane torch may not have heat enough to braze others than copper to copper. maybe some flux could help you.
But for sure MAPP is a must.

[the_new_guy]

i would use higher silver content rod, 45%

heat the compressor side, slowly move to the other and start feeding the filler with the heat on the compressor side.

are you using propane on its own or with oxy? get oxy

[[XC] MarioMaster]

i could never braze anything with propane, spend $30 at home depot and get a mapp gas torch, works a lot better

[Xeon th MG Pony]

I second that I used to have tons of problems with cold joints and the like got a mapp tourch and after that first thing I did was b*tch slap my self for not doing it sooner!

it will make a huge differance. And don't forget the usual of cleaning the pipe ends with alcohol after sanding for a clean ruffed surface.

[sl4ck]

And don't forget the usual of cleaning the pipe ends with alcohol after sanding for a clean ruffed surface.

Doesn´t the flux does that job? I think so..

[Brettbeck]

Does anyone use Oxy-Propane for brazing? Is it as good as MAPP?
I read somewhere propane burns hotter than acetylene, so if it's mixed with oxygen, shouldn't the propane setup be hotter than oxy-acetylene?

[the_new_guy]

i use oxy lpg, lpg is a dummer version of propane, works great, no probs even while doing evaps.

[Holst]

Doesn´t the flux does that job? I think so..

I was always told to clean the joint to remove and bits with some alchohol as well.

The flux should do this, but it dosent hurt to give it a hand.

(this is when working in a garage where you might have grease on your shirt or nearby)

[Hugo van Dijk]

Does anyone use Oxy-Propane for brazing? Is it as good as MAPP?
I read somewhere propane burns hotter than acetylene, so if it's mixed with oxygen, shouldn't the propane setup be hotter than oxy-acetylene?

No oxygen - acetylene is around +3200c

While oxygen propane is around +2700c

And i believe propane uses about 2x times as much oxygen as with acetylene.

[Brettbeck]

i use oxy lpg, lpg is a dummer version of propane, works great, no probs even while doing evaps.

Cool, so you just use the torch to do evaps too? Or do you use another stove burner to keep more heat in the evap?


No oxygen - acetylene is around +3200c

While oxygen propane is around +2700c

And i believe propane uses about 2x times as much oxygen as with acetylene.

Ahh right. You can regulate the oxygen though can't you? So giving the flame more would increase the temperature?

What about the temperature of MAPP gas? Is that anywhere near as hot as those two options?

[aasmaukr]

I thought Propane used more like 4 times as much Oxy as Acetylene.. I'd get Acetylene if i was going to start brazing with Oxy.

I don't think MAPP is very much hotter than Propane, but maybe higher pressure so you get a bigger flame. But i don't really know.

[bazx]

Most all problems with brazing comes down to temps

I only use oxy-acetylene

It near impossible to get a good joint every time with out full control
Over the amount of heat you can apply to the job

Oxy-acetylene maybe difficult to get but imo you will always find brazing hard without it

[Brettbeck]

So oxy-propane isn't really a good idea? Either use MAPP or oxy-acetylene?

[[XC] MarioMaster]

that's the way i would go

[Hugo van Dijk]

So oxy-propane isn't really a good idea? Either use MAPP or oxy-acetylene?

There is nothing wrong with oxygen propane, but if you buy welding equipment it doesn,t really matter in price if you go for propane or acetylene. Startup costs with propane might be a little cheaper but its not much. and then again you need a special torch for using propane you can,t just but a acetylene torch and use it with propane without adapting the torch and nozzles.

Mapp is around 1300/1400c (without oxygen) if I,m correct.

I worked with a propane torch on school and I really can,t emagine that people can braze with that, if I point my oxygen - actylene torch on a piece of copper its almost instantly ready for brazing, and if you even hold it a little to close it just burns the copper away. I,ve also tried mapp although personaly i think its a pain in the ass it clocks up alot and bottles are empty in no time. But he mapp is a good cheap way if you only plan to make one or maybe a few units, if you really have plans to build alot of units i think a little investment in a oxygen-acetylene torch is needed.

[Xeon th MG Pony]

Doesn´t the flux does that job? I think so..

Yes but to not do it is just being lazy you get all the better joint by actualy taking the extra 3 seconds to clean the junction properly, or be lazy and take your chances! I personaly love perfect reliable joints but hey, that's just me.

[trance565]

my oxy map turns brass into dust if i hold it there long enuff, like ... it just dissapears, turns into nothingness.... kina sweet

[eshbach]

Mapp is around 1300/1400c (without oxygen) if I,m correct.


Mapp gas is C3H4, yes? If so, it should have a combustion temperature around 2900C.

[the_new_guy]

i was able to do evaps without a stove burner, but its quicker with the burner.

propane and acetylene have almost same startup cost but, where i live acetylene is almost 4 times the price of propane.

[johann]

Most all problems with brazing comes down to temps

I only use oxy-acetylene

It near impossible to get a good joint every time with out full control
Over the amount of heat you can apply to the job

Oxy-acetylene maybe difficult to get but imo you will always find brazing hard without it

Not 100% true Baz. Use of a good quality MAPP head is more than fine. I use a Rotherberger MAPP head and have never seen the need for an oxy/acetylene setup.

[Hugo van Dijk]

i was able to do evaps without a stove burner, but its quicker with the burner.

propane and acetylene have almost same startup cost but, where i live acetylene is almost 4 times the price of propane.

Same here Acetylene is around 40euro,s for 10liter bottle (and that,s even with the discount i get). but 10Liter bottles get filled by hand next year I,m going to get 35liters which get filled automaticly and so much cheaper. and at higher pressure (acetyleen 17, oxygen 300bars) the gas for these 35liters are the same price as the for the 10liters. only the bottle itself is more exspensive.

[RussC]

When brazing by the comprssor, I use two torches. The compressor will soak up alot of heat. I usally mount the propane torch in my bench on the fitting. Then start in with the oxy/mapp torch. That usually does the trick.

RussC

[johann]

I find no problem atall when brazing even compressor ports with my Rotherberger MAPP torch. I only use two torches when brazing of the heavier evaps.

[meggwell]

Does anyone use Oxy-Propane for brazing? Is it as good as MAPP?
I read somewhere propane burns hotter than acetylene, so if it's mixed with oxygen, shouldn't the propane setup be hotter than oxy-acetylene?

MAPP is just a little hotter and cleaner .. but propane is cheaper. with mapp there is no reason to have two cylinders to push around..

[DetroitAC]

Could you describe (or snap a picture of) the "ugly" joint Star882?

If you put the flame directly on the filler metal and overheat it, something glows and burns off (the phos maybe?) leaving a nice little pinhole. You'll end up with a cratered joint, pinholes everywhere.

If the base metal doesn't get hot enough, the filler will melt, but won't get to liquidus and "flow" into the joint. The joint will look globby, is that a word? it should be.

If you are brazing to a compressor tube that has lost it's copper coating, you need a flux and probably a different filler like safety silv 45.

The fix to your prob depends on what the prob is exactly.

[Brettbeck]

I use a large propane torch on a 19Kg tank - never had a problem.

When i brase evaps i use a cheapo MAPP torch in addition to the propane torch to give some extra heat, works well. I've brased 7(?) evaporators and never had a leak on an evap (yet :D)...

Tom

I practiced with a similar setup...

http://www.justmyluck.f9.co.uk/Brett/Phase_Change/First_SS/2006-04-21_Resized%201024x768/19Kg-Propane+Torch.JPG

...but I wasn't really able to get the brazing rods to flow that well.
However I had the pipes in a vice, so could that have been taking all the heat from the pipe and stopping it from getting hot enough?

[wdrzal]

I copy this from a previouse explanation of liquidus and solidus,its also in the data base. You have have to have to proper heat and if there is a problem you have to know why.
the original question was something like "can you un-braze a joint." it will also help you understand how to make a proper joint, I wrote many explanation if you search the data base.

the correct answer is "it depends" unfortunatly the worse brazer you are the more likely you will not be able to remelt the joint.here is why: first you need to know that brazing rods have two melting temperatures,solidus and liquidus . the solidus is when a brazing rod just begins to melt and is thick and goo-ee,this contains solid and liquid metal. liquidus is when it is fully melted and flowing freely. when heating a joint and brazing it some of the base metal,copper in this case, is dissolved into the filler metal,and filler is asorbed by the copper .This diffusion process changes the chemical make up of the filler.it acts more like the copper tube. While this process is relativly slow, the longer the joint is at brazing temperature the more copper is transfered to the filler. This raises the filler melting point above its original one. So the longer it take you to braze a joint, the hotter temp you need to re-melt the filler. so you guys that hover over a joint for 5 or 10 minuites probable ain't geting it apart. I just did 2 tests for a comparason, one useing a acetylene/oxygen torch with a 0 tip very small and a acetylene /air torch ,b tank w/#3 tip medium, both joined 3/8 copper tube using swage (lap) joint. I chose phos-copper rods,no silver , highest melting point rod I have. the soldius temp is 1310f and the liquidus temp is 1471f. as you can see there is a 161 degree differance between were they begin to melt and flow. I think this is why most guys have trouble. any how ,the act/oxy torch took between 8 to 10 seconds to braze the listed joint. my act/air torch took 20 to 25 seconds for the same joint. one note,I did these tests without flowing nitrogen thru joint, it may have a slight cooling effect making time slightly longer.I have a propane /air torch that I will test over weekend and post results here.If brazing to the compressor or a brass fitting or any thing that "sucks up heat" brazing times will be longer. There is no question that a acetylene/oxygen torch is the best by far for this type of work. But no matter what torch you use,the trick is to be sure the copper tube is hotter than the liquidus temperature of your rod before touching the rod to it.This way the rod flows around in 1 or 2 seconds then your done. If the tube is in a horizontal position ,Once the tube is hot I touch it at the 10 o'clock position sweeping the rod over the top to the 2 o'clock position.do this quickly,1 second. this is so braze flows down both sides, you can just touch it at the top also but I found my method makes sure the filler flows completly around the joint. "work safe" walt

[Marvin]

nice, i was watching this video, but i dont know what kind o mix this man prepared, but resulted in white flux :
http://www.youtube.com/watch?v=62t61RZ37Bo

[Brettbeck]

nice, i was watching this video, but i dont know what kind o mix this man prepared, but resulted in white flux :
http://www.youtube.com/watch?v=62t61RZ37Bo

IMO that video seemed a little strange... the way he brazed that joint. WAY too much flux imo and you shouldn't even need flux for copper to aluminium.

[LittleDevil]

Are those normal silver rods? Is it possible to braze ALU to Copper with 45% silver brazing rods with flux?

regards

[Brettbeck]

Are those normal silver rods? Is it possible to braze ALU to Copper with 45% silver brazing rods with flux?

regards

I don't know which rods the guy is using in that video on youtube, I don't think it says either.

I would say it is possible to braze alu to copper with 45% rods with flux, as long as you have enough heat.

[Barnsley-Bill]

the trick with brazing and welding with gas is to make sure the parts your going to weld or braze are hot enough like its bean said imo once you get it right you know when to touch the rod so it runs stright away .
Brettbeck id use a mat if i were you if i weld small stuff i use a damp sand bag with a heat mat and lean the part to be welded on it allso brazing outside when its cold takes away a load of heat .

[Gray Mole]

Silver, even high grade, generally won't melt until your ALU is dust.

In fact, even the pure ALU rods I used tend to be hard to work with, as most ALU pipes have so much other stuff in them that they disintegrate before you're at brazing temp.

So I just tend to use 'Heat Stick' on ALU that's repairable. Pinholes, small cracks, it works real well. Melts around 200-250c and holds up to about 40 bar. Nice stuff to have around, works on pretty much any metal if you clean it really well.

I had a huge oxy/acetyl kit, but got rid of it. At home it just took up too much space and I've never found anything that it was 'critical' for.

I have 3 Mapp torches, and one oxy/mapp kit as well.

I tend to use 2 mapp torches for evaps, one on the base to heat it up, and then I adjust it down to maintain temps, and the other for specific brazing.

I don't really like to use oxy/acetyl on most things unless it's a valve or something that you want to be in and out asap. I've not found anything that the oxy/mapp can't do that oxy/acetyl can, but it's a small kit and it kills the bottles of oxy fast, so I use it sparingly.

Brazing is pretty easy after a while, you get to know your material. For anything that's even remotely possible to have steel behind it (danfoss compressors) just use flux and silver.

One trick I like to use is to braze in flux and high content silver, then finish the braze with low silver content filler. I find that silver is pretty thin whatever the %, and the low content stuff works well on top of it to strengthen it up when you need it.

Cheers

Gray

[Marvin]

Thanks Gray, but i have a doubt. Does the MAPP torch has heat enough to use with silver rods ?
I just cant braze with 40%silver rods, just 15% phoscooper. the torch dont have heat to melt the silver.

[Exahertz]

so you can mix brazing rods?

[Ssilencer]

I'm now using silver and flux in any joint, it is best and harder joint, and if you build a unit not too often, the costs are more than ok.
For stainless steel to copper, I used highr silver content (45%) with flux.

BTW, I have an oxi propane torch and it is more than enough, I have to take care or I can make holes everywhere with it :D

[Gray Mole]

Strange Marvin, all of the high content silver rods I have are a lower melting point than lower content.

I've never had a problem with Mapp getting it hot enough, but getting both the copper and stainless hot enough and ensuring there's enough flux there to make the bond can be challenging. Takes some practice for sure.

Oxy/(insert your choice of gas here) tends to make that easier, as it gives you a pinpoint of heat where you need it, where Mapp with a 'turbo torch' is a larger flame point. It can be more difficult to be exact with it.

As far as mixing filler goes, I've never had a problem. That's all they're doing, really, is mixing different kinds of filler with cutting agents, so doing a little of that yourself is fine.

The main reason I do it at times is that while you get the best bond with Silver, sometimes you don't get the same level of 'fill'. I like to make the initial bond, especially with stainless to copper, with 55% silver. If the fill is too thin, I'll finish it up with some 5% silver rod. I find it's quite 'thick' and gives the joint more durability.

I've been welding with Mig and Gas for a number of years so I've got a good background in it. If you're just starting out there's a whole bunch of 'little things' you get to know, and it just takes practice to develop your technique.

brazing with flux is probably the most challenging, as you've got to balance the heat between metals, make sure you don't burn out your flux, and and also ensure you don't overheat the stainless and make it brittle, especially where the thin flex line is brazed.

The guide on brazing is a help I suppose, but really there's no substitute for practice.

Gray

[Marvin]

Thanks Gray, but for me brazing with 15% silver and MAPP torch much easier. The 40 % silver rod doesnt melt easy for me :

[Brettbeck]

Brettbeck id use a mat if i were you if i weld small stuff i use a damp sand bag with a heat mat and lean the part to be welded on it allso brazing outside when its cold takes away a load of heat .

Yeah I do use heatproof mats, although with the oxy-propane setup I now have they just aren't enough, they just melt :D.

I'm going to get about a dozen firebricks soon, and make a bed type heatproof surface with them. Should work perfect.

[Gray Mole]

That's a very nice braze Marvin :)

I think perhaps your 40% silver sticks are different somehow.

I've been using the same supplier for my rods for a while now, so I'm used to the characteristics of each one.

You CAN buy silver sticks with the same content, but with different components that dictate the flow rates and the melting temps. If you're finding it difficult to work with one type, I would approach the supplier for the exact details of the rods, melting point, flow characteristics, etc. They should have that info for you.

Looks like you're getting pretty good at brazing though, so I doubt it's your technique that's a problem. It's probably a type of rod that's meant for another application, or has a strangely high melting point for something else.

Cheers

Gray

[ak_47_boy]

I got a Victor TurboTorch total LP off ebay for $30. I got a mini bbq tank for it. I can heat up a 3/8" line to brazing temperature in approx. 5 seconds. It works very good, it is very cheap to run. I love it.

If i have a stubborn joint i heat the joint till the braze melts then drip a bit of flux on it with a screwdriver, all i know is this works for some reason.

edit: i did a cap in cap evap with ease.