Cannot braze copper or too hard to do, any tips?

[meke]

Hi,
after using some technician support, I decide to do my own work to finish my single stage.

He was using the electric soldering kit and really too easy to have leaks, I almost lost 2 weeks for this s**t.

Anyway, I decide to buy an oxi/lpg kit for brazing, but too expensive for a basic startup, I bought a basic starter kit for around 50$.

It's a ROTHENBERGER kit called Turbostar 2100,
contains LPG and working conditions are;

Flame temperature 2100 °C
Working Temperature 850 °C

http://www.nexmart.de/intershoproot/eCS/nexMart/en_DE/sellerdata/spezial_09/catalog/media/04-0035630-11301.jpg



But I cannot make the rods melt around the copper.
I already read the tips about the brazing, also Hatemi uses a similar stuff and he confirms that this kit is enough for brazing.

I first open the valve and use the ligther to fire it.
then give some gas to get the copper in red.

I push the rod into the red & hot copper but it doesn't melt.

I checked the rods and they melt @ 710 °C

When I success to melt it, it brazes the copper tubes like 0,5 cm thick and nearly 5 cm of rod has gone.

Also the copper parts are nearly black because I keep the torch around 5 minutes over them to get the rod melt over it. I don't care the finish but the inner parts are also black needs a lot cleanup. :slapass:

Do I need some oxigen support to melt better or am I just in the first day of the begining class for welding world? :confused:

[wdrzal]

what type rod are you using? most people that have problems are using the wrong ones.not all rods will flow on copper. when a joint is properly heated the braze will flow around and into the overlap(swage). flowing nitrogen thru the tube while brazing is the accepted method for keeping the inside of a tube from oxidizing. work safe walt

The type of tip you use also makes a big difference.one that concentes the flame is much better than a general heating tip.

[meke]

My rods are again ROTHENBERGER Rolot 607, seems suitable for this temps, and it says
"for copper-copper, do not need flux" over the package.

Should I use some silver added rods? or add some flux or paste?

I know how it fills the gap when the temp and parts are correct, but couldnot mak it run like that :mad:

[wdrzal]

while I don't know what rolot 607 is. they are probable are phosphores rods. the lpg/air torch is at the low end of the heat requirement for brazing. so you must have the proper tip on your torch. I never used the style of torch you have so I don't know its abilities. Rods with silver in them have a lower melting point, this is what you may need.they melt a couple hundred degrees cooler than phorphores ones. ask hatemi what tip he has and what rods he uses with his torch.

as to the flux ,you don't need it with those rods when brazing copper to copper.

[meke]

I also have silver added rods, but not tried yet.

I will try tonight, also with the second end in the picture (the yellow one)

edit: btw, thank you for your support :)

[meke]

I solve it.

it was not the rod nor the torch, even not the temp.

The wrong choice was the clamp that I was using for holding the copper parts. :D

It was sucking all the heat to itself of course, I use an old copper wire to keep the parts away from the clamp,

let the parts get red and then just touch with the rod, bingo :banana:

I want to share the evolution of my brazing experience with you,
#1 is the first try with copper rod (yesterday)
#2 is the first try with %40 silver rod
#3 is the second try with %40 silver rod, but decide not to use it
#4 is the finished braze with copper rod. (I will keep the %40 silver rod for steel to copper brazings)

I'm still looking for a solution for clean inside.( do not offer me using nitrogen or co2, because these like small parts will have some mounting problems for these gases, right?)

[Stewie007]

Mounting problems for these gases?

I don't know that I follow. I just got a Nitro Cylinder, a regulator with a quarter inch union, and connected a small flared tube to both the system and the cylinder and turned it on. Unless I don't follow you right...

And you are most correct in avoiding the 40% silver for copper. You better make sure you have some Black Flux though (Stay Silv for example) for high temp brazing of Copper to STeel or Brass. Phos copper is the best to use with copper, it creates the strongest bond. :)

[andL64]

well, i am also now in this business and i ve got the same problem i ll try ur advices and i also use something what could suck heat..... !

seEn

[Stewie007]

I use steel vices at work all the time, you just gotta be patient and apply more heat. It'll glow, you just have to give it more time when you've basically got a heatsink attached. It'll take longer, but still it works.

[Jimi...]

Can't you just use solder for joining copper pipe to copper pipe?

[wdrzal]

I going to try to answer a few questions here,first when building a system you usually assemble the whole system with the exception of items that must be pre-brazed then do your brazing with nitrogen flowing thru the line. the inside of a refrigeration system must be clean,thats clean room clean, or you will have problems later.those black specs will clog your filter and cap tube. since its allmost imposible to completly clean inside a tube, the only method is to prevent them from forming in the first place.

jimi if you mean soft solder like 50/50 mor 60 /40 no you can't it reacts with refrigerants and the tensil strenght is too low for the application.

[Lando95]

Can't you just use solder for joining copper pipe to copper pipe?

No, it is not strong enough to hold the joints together.

[Coyote]

whats the composition of LPG?? is it better than MAPP?

[wdrzal]

Lpg is the abbreveation for propane(liquified propane gas) , mapp is lpg + actylene. mapp is hotter

[meke]

LPG is something %70 butan, %30 propane.

My ROTHENBERGER gas called "GAS300" contains %65 butan and %35 propane, similar to lpg.

Mapp is different, "GAS400" called @ ROTHENBERGER, and it is butan, propane and actylene.

They prepare a super burner kit called "oxi", use mapp + oxi and give
Flame temperature 3100 °C
Working Temperature 1250 °C

I think the lpg is the key here because it also add some soot (blacken) over and in the copper tubes. I remember than lpg also add some soot over the soucepot in my kitchen :(

anyway, @ wdrzal , you advice to fix the assembly without braze and let nitro gas in, but what about the brazing rule? you have to keep the parts vertical position and it's not possible to braze in any condition, the rod or the torch may not have a possible direction or heat may damage some part in the assembly. :confused:

[wdrzal]

propane is marketed as LPG and butane is also LPG as are a mix of the 2 ,I made a mistake lpg is" liquified petroleum gas", I am used to propane because around here that what it is.not butane.

[wdrzal]

You can braze a connection in any position,the filler will flow towards the heat.

[meke]

I made a mistake lpg is" liquified petroleum gas"

no, you don't.

LPG stands for Liquified Petroleum Gas, but doesn't write a rule for the mixture of the petroleum gases :toast:

[meke]

well, i am also now in this business and i ve got the same problem i ll try ur advices and i also use something what could suck heat..... !

seEn

If you are not kidding, you are wrong. :p:

I advice you fix some wires by clamp, then use that wires to hold the copper parts away from the clamp.

[Jimi...]

Are you able to heat up old brazed joints and take them apart like you can do with soldered joints?

[expansionvalve]

I will have to disagree to some degree about soft solder not being useable on a system, although I would not use the stuff from a plumbing shop, I have used and do use a refrigeration spec soft solder, copper to copper only, for suction,liquid and discharge lines in the trade and with one transport manufacturer this grade of solder is all they use on their 134a and 404a systems. It's pretty good stuff and I have never had a discharge line blow the solder even with head pressure sitting at 300psi. One thing I must mention though is that it's probably not the easiest solder to use, the joints have to be very very clean, it needs tinning before hand and the heat from the torch needs to be spot on, tell a lie, the only time I have see soft solder blow is when the hp switch has died and there has been a problem with the condenser fans the head pressure reached around 400psi when the discharge line blew. Another line of thinking, you know you see some receiver tanks with a fusible plug? guess what that solder is, soft.

I would give you some specs on the solder if the 5 year old roll still had the label on it.
I will even put my money where my mouth is and solder my new rig with the stuff.

I like soft solder as you do not get the oxidisation but like silver because of the strength.

[wdrzal]

there's no silver, its lead and tin,unless you have a roll of high silver silver solder

[expansionvalve]

Not sure on it's exact make up, all I do is ask the parts guy for soft refrig solder and I get a roll. I will have a gander tomorrow and see what I can find out about it, pretty good whatever it is :D

[wdrzal]

about what does it cost, in dollars if you know.

[Russell_hq]

You get soft solder that is lead free and is marketed as "Silver bearing lead free solder". I used it on a couple of my capillary joints, as these are strong joints because of the small gap between the 2 pipes. Though I would recommend using silver brazing rods as soft solder aint as strong as others.

[wdrzal]

I bet your right russel, we use that all the time for water pipes,in fact its the law here, you can no longer use 50/50 solder like we used too.never even crossed my mind.the silver content is really low

[Stewie007]

Copper to Copper - Phos Copper

Brass/Steel to Copper - 40T Silver Rod


Those are the only two rods I use when brazing. :) I wouldn't dare use a low temp solder to join my copper together. It'll vibrate and crack very quickly. Its simply not worth the trouble. Phos copper will create the strongest bond, and you can successfully braze using MAPP Gas with it. Black flux will make the job easier even on copper to copper. You can use low % silver like 15% Rods, they're fine.

For either you really don't need flux, but it works alot better when you use it. :) You'll garuntee yourself, assuming that you heated the connection properly, that you have complete joint penetration and a sturdy joint.

[Jimi...]

Is it possible to heat up a brazed joint and take it apart?

[meke]

Is it possible to heat up a brazed joint and take it apart?

depending on my 2 weeks welding and brazing experience, you cannot :p:

[cold_ice]

Is it possible to heat up a brazed joint and take it apart?
You can

[wdrzal]

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

[Stewie007]

You make it sound so complicated, yet it is not. :p

Try not over explaining it, they'll better understand then.

[wdrzal]

You make it sound so complicated, yet it is not. :p

Try not over explaining it, they'll better understand then.


everyone is aware you can teach a monkey to braze,"Heat tube ,apply rod!!! "I wrote that for those who are intersted in the specifics.

[gclg2000]

You make it sound so complicated, yet it is not. :p

Try not over explaining it, they'll better understand then.

Well it has been a while....

[Stewie007]

I gather Walt, but next time arrange it better... It gave me a headache straining to read it without the computer screen mixing it around all funny like it does when you stare at it long enough...

One big paragraph..... yeesh.. most people don't even read them.

[gclg2000]

I read through it.

Good post walt.