Brazing

[garym]

I was asked if I could mend a break in a chrome plated steel walking frame and thought that this would be a good candidate for brazing.

I haven't done any brazing since my days as an apprentice about 35 years ago and then I had access to all the right gear (oxy/acetylene etc).

But I thought how hard can it be? looked up a few tutorials, thought I could use my Taymar blow torch and set off to bunnings to get some brazing rod and flux.

Ha! first Bunnings I went to didn't have ANY brazing rod or flux. The second Bunnings had some dusty old unmarked brazing rod but no flux.

Went to Mitre 10 and bought some Bernzomatic Nickel/silver flux coated brazing rod (blue). Got home and the blow torch just burnt off the flux and nothing else. Went back to Mitre 10 and bought a Yellow tip brazing rod. They didn't have any flux. Went to GasWeld - no brazing rod and no flux (I still can't believe that!), went to another Mitre 10 and bought a plastic jar of CigWeld "COMWELD Copper and brass flux". The directions say: "Specially developed for braze welding copper OR steel".

Got home and tested all on a couple of 2-1/2" nails. Did all the documented things, cleaned, cleaned, ground to shiny metal, cleaned again coated with flux, brought up to red heat (I think, I am red-green colour blind) added the rod which melted and just formed into round blobs and dripped of the nails (i.e. did not "wet" the steel at all). Tried again with 1/8" and 1/16" plate/sheet. Same result - no "wetting" of the target material.

I have tried the flux in powder form and in paste form (by adding a little water). I have tried cleaning with detergent, acetate, hydrochloric acid, and grinding. All to no avail.

Am I completely off the track here? Am I using the right brazing rod/flux? if not, what do I need? and where can I get it? (I am in Sydney and there does not seem to be a large range available to hobbyists here).

Whilst I can repair the frame some other way, brazing is something I would like to be able to do a little of as long as the cost is not prohibitive.

Any advice would be much appreciated.

[Fossil]

Hi garym

I have not brazed with anything but an oxy setup before.
Are you getting enough heat in to the work?

I have a big pack of CIG Pink rods in the shed, and haven't had any particular issues brazing steel.

If it were me, I would weld the break with oxy/acet and bit of tie wire. I have done heaps of repairs on bike frames using this method for some of the local kids, and the welds stand up the jumping abuse these bikes get.

[Ashore]

Proberly a heat problem, as an alternative you could get the closest fitting copper tube that will slide/fit over the chrome frame cut a 4-5 cm length slide it over the break and silver solder it:wink:


Rgds

[garym]

Thanks for the reply Fossil (doesn't feel right calling you that).


Hi garym

I have not brazed with anything but an oxy setup before.
Are you getting enough heat in to the work?

I have a big pack of CIG Pink rods in the shed, and haven't had any particular issues brazing steel.

If it were me, I would weld the break with oxy/acet and bit of tie wire. I have done heaps of repairs on bike frames using this method for some of the local kids, and the welds stand up the jumping abuse these bikes get.

I must admit that I don't think that I'm getting enough heat to bring the steel up to the correct temperature (although I am getting it to yellow heat in the case of the nail test).

I would love an oxy/acetylene set but it seems hard for hobbyists to obtain the gas bottles these days, and I am not sure if the small amount of brazing I am likely to do (granted that there are a lot of other uses) would justify the cost.

May I ask where you sourced your set from? and can you give me an indication of the cost?

When you say you would "weld the break with oxy/acet" are you referring to a fusion weld?

Thanks again.

[faex]

i used cig blue rods and mapp gas to weld 2mm steel tube to 1mm tube. i had to heat for ages until it was red over a large area. if you put the rods under direct flame when at steel brazing temperature they will just blob and wont melt to the parent metal. i had to scratch the rods over the red part until i could see it spreading to the parent metal in a thin way (like with silver solder at a lower temp) edit: this was while the flame was only indirectly heating the rod+area. after that the rods braze to the thin brass layer easily.

[garym]

Proberly a heat problem, as an alternative you could get the closest fitting copper tube that will slide/fit over the chrome frame cut a 4-5 cm length slide it over the break and silver solder it:wink:


Rgds

Ahh! but what exactly do you mean by "silver solder"? In effect I thought that "silver soldering" was more-or-less what I was trying to do (the brazing rod is yellow tip which I think means it contains 2% silver). The difference between "silver soldering" and brazing is not clear to me unless you are referring to a much higher content of silver (and therefore lower melting temp)? I haven't been able to source any higher silver content rod. The idea of the tube was one I was going to fall back on if the braze wasn't strong enough, however if I can't get the braze/silver solder to wet the steel this method won't work either.

Cheers.

[faex]

Ahh! but what exactly do you mean by "silver solder"? .

"Hard soldering" or "silver soldering" (performed with high-temperature solder containing up to 40% silver) is also often a form of brazing, since it involves filler materials with melting points in the vicinity of, or in excess of, 450 °C.

http://en.wikipedia.org/wiki/Soldering

[garym]

i used cig blue rods and mapp gas to weld 2mm steel tube to 1mm tube. i had to heat for ages until it was red over a large area. if you put the rods under direct flame when at steel brazing temperature they will just blob and wont melt to the parent metal. i had to scratch the rods over the red part until i could see it spreading to the parent metal in a thin way (like with silver solder at a lower temp) edit: this was while the flame was only indirectly heating the rod+area. after that the rods braze to the thin brass layer easily.

Thanks faex. That is just what is happening (the blobbing). I haven't been able to get the metal hot enough to melt the rod without direct flame so that's probably my problem, MAPP would be much hotter than what I am getting from my Taymar. What you describe seems a lot like 'tinning' when soft soldering - it makes sense. I did try a form of this by filing the rod and mixing the file shavings with flux and then trying to get the mix to 'melt' by indirect heat, but I couldn't get it hot enough I don't think.

I assume the CIG blue rods would be the same as the Bernzomatic blue rod I tried first? i.e. Nickel Silver - self fluxing?

Anyway it looks like I will have to go MAPP or oxy/acet.

Cheers

[Barry Hicks]

G'day Garym,
In my experience (limited) you are wasting your time trying to braze with propane etc alone.
I have been using SBA (silver brazing alloy) 245 with great success on small jobs over the years on straight propane. I believe SBA 245 is commonly called silver solder and has a relatively low melting point.

Barry Hicks

[garym]

G'day Garym,
In my experience (limited) you are wasting your time trying to braze with propane etc alone.
I have been using SBA (silver brazing alloy) 245 with great success on small jobs over the years on straight propane. I believe SBA 245 is commonly called silver solder and has a relatively low melting point.

Barry Hicks

Thanks Barry - I suspect you're right.

Where did you get the SBA 245 from?

Cheers.

[Grahame Collins]

I added the rod which melted and just formed into round blobs and dripped of the nails (i.e. did not "wet" the steel at all).

Brazing and Silver brazing are almost the same technique. The difference being in the temperature at which the filler bonds with the parent metal.
The critical element in both applications is that the parent metal temperature is hot enough to melt the filler material. The heat source, heats the parent metal not the filler material.
The question is ,are you brazing with a bronze based filler material or are you silver brazing. Bronze based wire is a gold colour when polished clean and silver based is a platinum colour.

I strongly suspect you don't have the technique correct.

Grahame

[garym]

Brazing and Silver brazing are almost the same technique. The difference being in the temperature at which the filler bonds with the parent metal.
The critical element in both applications is that the parent metal temperature is hot enough to melt the filler material. The heat source, heats the parent metal not the filler material.
The question is ,are you brazing with a bronze based filler material or are you silver brazing. Bronze based wire is a gold colour when polished clean and silver based is a platinum colour.
Grahame


Thanks Grahame, that's pretty much how I understood it, however, can you clarify a couple of things for me? Is the colour of the "silver braze" due to the higher silver content (the gold coloured rod I am using does contain 2% silver) or is it a completely different thing? Does the platinum coloured rod have a tip colour?



I strongly suspect you don't have the technique correct.
Grahame

I'm damn sure of it! :((

Cheers.

[Grahame Collins]

The silver content would have a bearing on the colour.

There is a blue tip coded silver solder Comweld SBA 245.From my memory it runs 40-50% silver content.

2% silver content does not not sound right at all

Putting the flame on the filler will cause it to go molten before the parent metal is hot enough to bond with it.

Fluxing is with brazing (bronze) is by warming the metal first,then throw a pinch of powdered flux on the hot metal which then sticks to it. Doing it the other way- putting flux on cold metal, then heating, lets most of the flux get blown away by the flame. The filler is wiped onto the metal and is melted by it, only if the metal is hot enough.

Fluxing with Silver Brazing is by a borax based liquid which goes on the cold metal. When the metal heats up under flame and turns the liquid to a dried toothpaste look. Further heating will eventually turn the flux clear like water.thats the time you wipe the SBA on the hot metal and it will run immediately.

That help ?
Grahame

[Barry Hicks]

G'day again Garym
Graheme C obviously knows what he is talking about!
SBA 245 seems to be widely available in places that sell welding type gear. I bought my last lot in a little place in Atherton in FNQ and I have bought it at a CIG outlet in Townsville.

Barry Hicks

[garym]

The silver content would have a bearing on the colour.

There is a blue tip coded silver solder Comweld SBA 245.From my memory it runs 40-50% silver content.

2% silver content does not not sound right at all

Putting the flame on the filler will cause it to go molten before the parent metal is hot enough to bond with it.

Fluxing is with brazing (bronze) is by warming th metal first,then throw a pinch of powdered flux on the hot meta which then sticks to it.Doing it the other way- puting flux on cold metal ,then heating,lets most of the flux get blown away by the flame. The fillier is wiped onto the metal and is melted by it only if the metal is hot enough.

Fluxing with Silver Brazing is by a borax based liquid which goes on the cold metal. When the metal heats up under flame and turns the liquid to a dried toothpaste look. Further heating will eventually turn the flux clear like water.thats the time you wipe the SBA on the hot metal and it will run immediately.

That help
Grahame

Thanks for the clarification Grahame.

I get the 2% from a statement I found on the web:
"Silver solder has a % of silver. Yellow tip 2%, Brown 15% and Blue 45%"

However, this is anecdotal and I have been unable to verify it from a reliable source.

So, it looks like I am using a high melting temp version of silver solder, with flux meant for brazing (i.e. Boric Acid + Sodium Metaborate) as it is definitely a powder (I have tried making it into a paste by adding water).

I nearly bought the silver solder flux but it was a third the quantity of the brazing flux and a third more expensive (penny pinching costs me again, doh!).

Can you suggest a source for Comweld SBA 245?

Thanks very much for your assistance, lot's of good tips there.

Cheers.

Gary

[Grahame Collins]

Can you suggest a source for Comweld SBA 245?



One of the welding supply shops will have it.

Or try and an enginnerring shop,they may sell you 1 stick
Grahame

[Master Splinter]

If you picked up a yellow tip brazing rod from Bunnies, I'll bet it was in the plumbing section.

That'll make it a phos copper rod that is designed for the fluxless brazing of copper pipe. They'll work on brass with flux, but I've never heard of them used on steel.

[garym]

If you picked up a yellow tip brazing rod from Bunnies, I'll bet it was in the plumbing section.



That'll make it a phos copper rod that is designed for the fluxless brazing of copper pipe. They'll work on brass with flux, but I've never heard of them used on steel.


No, I didn't get it from Bunnings, although when I enquired about brazing rods I was sent to the plumbing section and there I was pointed to a few dusty old rods that were obviously very old stock, not labelled, not priced, and didn't have any corresponding flux. Needless to say I didn't buy anything there. It wasn't much better at Mitre 10 but I did get the yellow tip there, it wasn't in the plumbing section but I would bet quids you are spot on, it's just that info from various web sites indicate that it should work with steel, unless, of course, there is a yellow tip code for other types of rod, *nowhere* I have been to has any information about the composition of the rods at all, and the staff never know, but the main use of these rods would definitely be for plumbing so I think you are right.

I suppose I was being optimistic about getting the correct rods from a hardware store. I thought GasWeld (given the name) would be sure to have a good range but no, nothing at all. the trouble is that when I look under yellow pages for welding supplies is it's all wholesale and don't sell to the public. It's strange but living in the inner part of Sydney seems to be a real disadvantage in sourcing engineering supplies (for the individual).

I think I'll have to buy it online (if I can).

Thanks to everyone for your advice.

[pipeclay]

try reece plumbing supplies

[garym]

try reece plumbing supplies

Thanks pipeclay - will do. There is one quite close so fingers crossed.

[garym]

Just as a summary to this thread:

After two days of research,

Nearly all of the easily available (i.e from hardware stores) brazing rod contains phosphorus which makes it unsuitable for brazing steel (although it should still wet it, I believe I am using the wrong flux or have too low a heat), and what doesn't requires very high heat (= oxy/acetylene).

I have located two companies in Sydney that sell the SBA 245 (and similar). Unfortunately they only sell it in quantities that make it cost prohibitive (250 grams = $600), at least for my application.

I have sent an email off to www.mcmaster.com (http://www.mcmaster.com) asking about freight costs to Sydney but I fear that the freight cost will make it too expensive.

At this point I think that I must conclude that brazing is not an option due to the cost and difficulty in obtaining supplies.

Thanks again to everyone that provided info.

Cheers

[durwood]

Seeing that you are doing a favour for a friend and only need a small amount of material to fix the walking frame why don't you look up a TAFE college. Most have welding and some have panel beating sections which would have the materials and the knowhow to do your little job. In Sydnely you shouldn't be too far from one.

I'm sure if you went to one a teacher would be more than happy to help you out either by giving you a bit of rod and flux and some guidance or by actually getting a student to do it or doing it themselves.

I wouldn't ring I would just front up,( they get crank calls from all soprts of people) maybe call to find out if they have classes at night ( most do) and wander down sometime when you can.

[Grahame Collins]

I'm sure if you went to one a teacher would be more than happy to help you out either by giving you a bit of rod and flux and some guidance or by actually getting a student to do it or doing it themselves.

I wouldn't ring I would just front up,( they get crank calls from all soprts of people) maybe call to find out if they have classes at night ( most do) and wander down sometime when you can.

Durwood ,
PLEASE ACCEPT THESE COMMENTS IN THE VEIN THEY ARE INTENDED.
Sadly, you are out of touch with the workings of most Tafes. I am from the NT and Queensland Tafe systems and am reasonably sure the others are pretty similiar.

Tafe teachers are not in a position to just help out anyone that wanders in unannounced with a foreign order.You have not considered all the bureaucratic bull fecal matter Tafe staff have to deal with. Just the risk and legal factors say no,no, no! Teachers are employees like anybody else and are not permitted to make that decision.

Forget good deeds and public service and being all warm and fuzzy. Thanks, but they already have more than enough to do in chasing up fee for service work ( with industry) just to generate income to keep UNDERFUNDED Tafes going. Its about funding more than anything.

Security is another thing.We live in a time of all type of threats to our security and Tafe colleges are no different Rock up to a class at night time and you are not registered as a student ,you may well be shown the door by security.

If you want Tafe to do anything at all for you, going through through official channels is the only way to go.

Consider how you would feel if someone arrives at your workplace and wants a foreigner done for them. It only takes something to go awry and who is in the shyte?

Cheers
Grahame

[durwood]

I have worked in TAFE NSW for over 33 years.

Its always the teachers call, they may or may not want to offer anyone any help but I have never refused to help any one if it was a reasonable request for help.

In NSW the TAFE is there to serve the community, sure there are legal factors but giving someone a piece of brazing rod and a teaspoon of flux is no big deal.

I understand where you are coming from but having known the Queensland TAFE system it doesn't surprise me that you would take the view you have.

If I ever took any notice of the bureaucratic line nothing would ever get done. In NSW service fees do exist but again most courses don't have them and even if they did it still wouldn't prevent me or my collegues from offering assistance to anyone.

[Metal Head]

I have worked in TAFE NSW for over 33 years.

Its always the teachers call, they may or may not want to offer anyone any help but I have never refused to help any one if it was a reasonable request for help.

In NSW the TAFE is there to serve the community, sure there are legal factors but giving someone a piece of brazing rod and a teaspoon of flux is no big deal.

Personally I wouldn't do that Durwood as I would leave myself open to fellow colleagues accusing me of giving items (tax payers) away. Next thing you could have Today Tonight calling in to say you had given the terrorist some of the items to make a bomb that is to be used to blow a building up at your TAFE:wink: :D. But seriously speaking having worked in Uni workshops in the past and been faced with the same dilemma I wouldn't do it. We once had a guy walk in off the street wanting a tank (air) just patched up:rolleyes:. I explained to him the legal issues with doing it then kicked him out when he thought I was being unreasonable. We also had another guy (unknown) come in who wanted just a small piece of ally which my boss gave him. Then the next day he came in for some S.S. but told him we weren't a charity shop , needless to say we didn't see him again. Being the way I have been bought up I will always try helping someone out but one has to be careful these days and not just legally wise. Would you pull over on a quiet lane in the countryside to help someone who had appeared to have brokendown?. I would have but not now. Now having learnt that a former next door neighbour had been bashed (lost teeth and nearly his eyesight) to a thug - trying to do the right thing nearly cost him his life:((.

I understand where you are coming from but having known the Queensland TAFE system it doesn't surprise me that you would take the view you have.

If I ever took any notice of the bureaucratic line nothing would ever get done. In NSW service fees do exist but again most courses don't have them and even if they did it still wouldn't prevent me or my collegues from offering assistance to anyone.

[garym]

Never mind, I don't think that I could have been that... wait for it...

BRAZEN!

...sorry...

:wink:


PS any other ideas anyone?

[Metal Head]

Durwood you didn't tell me the reason why I couldn't use your TIG welder the other day to weld my ally towbar but I just found out the reason why:wink:

http://cgi.ebay.com.au/TIG-WELDER_W0QQitemZ330153762274QQihZ014QQcategoryZ11774QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Didn't they give you a wage rise this year? :rolleyes: :D

Here in Victoria we sell a very similar welder but you don't need gas to arc weld with our's:2tsup:. Is that the same for you Graeme?

[Metal Head]

Never mind, I don't think that I could have been that... wait for it...

BRAZEN!

...sorry...

:wink:

PS any other ideas anyone?

Just pop into a couple of local welding shops and tell them a sob story and you will give them a 6 pack of beer for their troubles:wink:.

[garym]

The reply from McMaster:

Thank you for sending us this inquiry. Due to the ever-increasing complexity of U.S. Export regulations, McMaster-Carr has decided to only accept international orders from a few of our long-established customers, so we cannot assist with your inquiry or accept orders from you.

We sincerely regret any inconvenience this causes you.

Oh well, scratch another possibility...

[garym]

Well I've finally done it. It's cost me approximately the cost of two walking frames, but at least I've learnt something.

I bit the bullet and bought some 45% silver solder from BOC. I had to buy far more than I'm likely to ever need, but, at least now I know I can do it if the need arises.

In the end it was still a lot more difficult to do than I had hoped due to the fact that one side of the break has a lot of mass and the heat tended to run away from the joint, but time and lot's of flux seems to have done the trick.

Thanks to all that contributed information.

Cheers.

[faex]

its pretty impressive that you can manage to solder that stuff without mapp or hotter. that 40%+ silver stuff must be prettty handy.

[durwood]

Metal head
Thanks for finding the welder!

I have informed the welding department and they will bid on it tonight and hopefully get it back in the shop before a Current Affair finds out.

Grahame,
I know what you mean about someone coming in getting something done and then it goes wrong, the hairdressers are always having problems with people getting a free haircut and then complaining about the big chunks of hair missing when the students finish practicing on them.

[garym]

its pretty impressive that you can manage to solder that stuff without mapp or hotter. that 40%+ silver stuff must be prettty handy.

It's good stuff alright, I had some doubts about the strength of it but it seems very strong.

One thing though, I did a test on a bit of scrap using the new flux and the old 2% rod that we suspect contains phosporus and it worked just as well as the 45% stuff! Now of course the Phosphorus will react with the steel to reduce the strength of the join, but the question is, how long would this take? If it takes longer than the working life of the item then who cares? I wonder if there are any knowledgeable people out there that would care to comment?

[Master Splinter]

Working from memory - phosphorus settles on the grain boundaries in steel and promotes cracking.

But with something like mild steel...I think its more likely to rust out or fail due to poor brazing technique than fail due to phosphorus induced stress cracking.

If it was a high strength alloy steel in a highly stressed structure...I'd worry.

But in something made from an unknown grade of cheap steel (recycled Datsun 120Y's perhaps) that has already failed once...I don't think it is much of a concern.

[BobL]

Gary, no one has mentioned building up a "heat well" around the bits you wish to braze. This reduces the rate of heat loss as you move the torch around. My brazing technique was low-strength rubbish until I made a high temperature surround around the bits. I used some old fire bricks, two flat on the bottom and built up a wall of bricks around these.

The difference is very significant, now the bits get hotter quicker and stay much hotter for longer. Once the temp is right the brazing rod flows like water. While the final look is definitely not pro-like the joints are very strong. I used this method to braze the 25 x 1mm SHS Chainsaw mill frame and having the chainsaw mill vibrating around on if for a couple of hours would have to be a good test for it

BTW I'm using MAPP.