Brazing brass to steel

Can I have some advice on brazing brass to steel? What type of rod and which flux should I use and any tip on technique?

Norm can you confirm if you actually mean the high temperature brazing which usually requires oxy-acetylene or do you want to silver solder, which is sometimes known as silver brazing.

J

Brazing is joining by melting a brass filler rod into the joint. If you attempt to braze brass, you may melt the parent job. You can sliver solder at a lower temperature which will be just as strong, only dearer. Silver solder is currently about £2.50 for 100mm. Unless you can obtain some flux, it is also pricey. Remember - cleanliness of the surfaces is all important. The present low MP. silver solder from say Johnson Matthey is called Silver Flo. Ensure the parts are wired together or clamped as any movement during the procedure will cause problems. Also consider using Loctite of a suitable grade. On my Loctite leaflet, they claim it to actually be stronger than brazing, if done correctly. For fitting a rod into a hole it must not be a force fit but with minimal clearance.

Hi Norm

Go on ebay search brazing rods they are flux coated and quite cheep compared to silver rods. you can use no rods but use silver solder flux and melt the brass to make the joint, if you need a fillet then you must use a rod.

Regards

Stan

hi norm,

i disagree with stan (who's post didnt make sense 'melt the brass' etc).

'brazing' brass you need to silver solder and the lowest melting point stuff these days (unless someone will give you some precious easyflo or easyflo 2) is silverflo 55 or the cupalloys equivalent (630 degrees celcius). for silver soldering with steel you need quite an active flux - easyflo flux isnt active enough. use tenacity 4a or thessco F flux.

heat up quickly away from the brass onto the steel instead. (whack the heat up!) plenty of flux to a stiff creamy paste for use with steel.

i make lots of steel fabrications for my miniature locos silver soldered up.

cheers,

julian

Thank you all for your comments. I am trying to replicate a part I am replacing in the door lock of a 1935 car. The square holed brass bush is brass brazed into a steel lever. The joint on the other side has quite a large fillet to give it some strength, I wasn't sure that silver solder would give fillet or strength. Is there a low temperature brass coloured braising rod, maybe copper based and which flux would be suitable?

hi norm,

no, not without melting the brass you are aiming to add as part of the repair! silver solder (silverflo 55 or easyflo is you can get some). its as strong as the parent metal so strength not an issue. if you want to send me the bits i'll silver solder it for you if it's something yopu dont want to buy the stuff for or think you might lack the necessary experience etc (though its not that difficult really).

cheers,

julian

Hi Norm

Use 55% silver low temp silver solder eg 455 and longer life flux eg HT5. You will readily get this small component to temperature using a propane torch. Sit it on a lightweight firebrick. Dependent on your future needs you will get by with a 50gm pack of flux and a metre of wire 0.7mm dia.

For more info re technique go to http://www.cupalloys.co.uk/best_practice/

regards

keith

Edited By CuP Alloys 1 on 16/02/2014 07:58:34

Edited By CuP Alloys 1 on 16/02/2014 07:59:57

Edited By CuP Alloys 1 on 16/02/2014 08:00:30

A tip given to me many years ago, is when silver soldering steel mix the flux with methelayted spirit, this will help prevent the steel oxidising as it is heated. A word of caution though, if you do, do your silver soldering outside bearing in mind what you have mixed the flux with.

Hi Norm

Helpful comments all round, professional advice from Keith and a very generous offer from Julian - what more can you wish for!

Useful forum this eh?

( another) Norman

Confused now! If I use an oxy-acetylene torch can I braze brass to steel using brazing rod because I have a very good control of the heat, but if I only have a propane torch, I need to use silver rod so I can work at a lower temperature and have less chance of melting the brass component? (ie Oxy-Acetylene is precise application of heat, whereas propane is flooding the parts with heat more akin to soldering so less control)

Just wondering how this was done in 1935 when Norm's car was built.

Steve

Steve

They would have fitted a new one.

Simples

Mike

Just a thought - could the brass bush originally have been cast in place in a die rather than being a separate part brazed in?

Keith

Without knowing the contact area that is available for the silver solder it is almost impossible top say if a fillet will have an effect or not. Brazing is often used for joining tubes such as suspension components, cycle frames and the like where the area of the tube is very low so a fillet of braze adds considerably to the joints strength.

In the right hands brass to steel is not a problem but it takes skill not to melt teh brass part particularly if its a lot smaller than the steel part, in effect you are welding teh brass and brazing teh steel

J

Hi Norm, Don't know where you are , but IF your anywhere near Hunstanton, Norfolk, I can do it for you while you wait. I'll introduce you to the Wash Monster as well, if you wish. Noel.

Hi Julian

Brazing brass to steel without a filler rod was comon when i served my time in the 1950 it was even done by blacksmiths in the forge its the same principal as gas welding by melting the two pieces of steel to form the joint also comon practice.

Regards

Stan

Hi All

Success!

Have used Silverflo 55 with Easyflow Flux. It has produced a fine filleted joint very much more professional looking than the original.

Thank you all for your help and suggestions. What did we do before the internet? I suppose that is why the pace of change was that much slower.

Many thanks again

Norm

Hi Jason, a good way to explane the process. Technically, welding is fusion of the filler wire to the parant metal, therefore brass welding can only be done on brass and yes it is possible. In brazing there is no fusion with the parant metal, just a bonding, a bit like none solvent glues.

Braze welding is similar to brazing but uses a higher temperature and the technique is the same as welding two pieces of steel together but no fusion takes place on at least one of the components, however the joints can be practically as strong as fusion welded joints depending on joint design. Braze welding of broken cast iron manifolds is a typical application, as you would prep the joint as if you were going to weld it with a cast iron filler rod, and you would have a bead of brass in the joint, rather than the capilary action of brazing.

With the right skill braze welding of brass to steel can be done. I have done it several times, but not for vey many years now.

Regards Nick.

Hello gents

I am attempting to join a short length of silver steel (5/16th diameter) to a small piece of brass (1/8th) thick. I'm using silver solder, something called 'auflux' as the flux and am heating it all with a propane torch. My big problem is that I struggle to get the solder to run, and when it does it adheres only to the brass, not the steel.

Any ideas where I'm going wrong? All suggestions much appreciated

Thanks ......

Brian

Hi Brian.

See my response Feb 16th 2014. You have a flux problem.

Flux is exhausted or the steel is not at temperature,

Or the flux is not compatible with the melting range of the silver solder or the parent materials.

Nothing has changed! go to http//www,cupalloys.co.uk/best_practice/

Keith