56% silver brazing Steel to Steel wetting issues and low penetration problems
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    Default 56% silver brazing Steel to Steel wetting issues and low penetration problems

    Hi there everyone, Im just a backyard tinkerer looking to get away from messy stick welding so im moving to brazing 56% silver rods with propane or mapp.

    I have successfully brazed some pieces well ..around 12 pieces , and i was certain by this time i had this licked.

    However last night, i spend an hour over and over again trying to braze a simple steel nut to a washer...and i had issues that i never had before.

    first off after researching, i found the silver wasn't wetting properly when using my harris paste flux 1100-1700 working degree temperature.

    I would wait for the flux to glaze..then try to apply the rod, the rod does not melt upon touching the base material until the base material is glowing red, beyond dull red.

    my technique to compensate for this is to get the flux to glaze, and then head the rod until the tip of the rod melts and is nearly about to drip...THEN i apply the rod to the metal and put the torch flame ON the surface AND the rod all at once.

    In doing this i drastically reduce the work time available as the flux only has about 10 seconds before it turns black....
    I found last night..that this is not enough time to flow the rod.

    I will admit, that out of experimentation i have heated the part to bright RED to see if i can flow it further out....it doesn't work well and..i found that the silver seems to....how can I say this...."peel" off the steel when struck with a hammer....HARDLY mig weld strength (as it is supposed to be)

    The rod is fairly thick, its roughly 3/32, however...i had much success with this rod on previous attempts.

    I experiment with other techniques as i make jewlery on the side i cut small pieces of silver rod with the band saw and place them right next to the item to be brazed (right on top of the flux) then i just try my best to focus with the heat as the silver is in place. Sometimes this works, sometimes it does not.
    regardless, i cannot let the base metal melt the silver, i must use the torch heat directly on the rod AND the part...sometimes the flux turns black, and i must wire wheel it to clean it off, and then start again...each time losing more and more precious silver rod.

    I have spent much time on youtube vidoes but eventuall i knew that i woudl need to ask direct questions to professionals because i am out of idea.

    Im going to try to include a picture of last nights failure. I noticed the silver braze gets a lot of brownish, dare i say "rust" color on it?
    my other sucessful silver brazes look silver and clean, no pourocity either.

    Notice i was able to simply use a pair of plyers and RIP the bolt out of the silver..it peeled off like tin foil.
    Each time i grinded to new steel, and re-fluxed and tried again...the same result.

    possibly the flame out of my torch is defective? go out and buy new flame? ha ha.

    any help or advice you could give me woudl be appreciated
    Attached Thumbnails Attached Thumbnails dscn3029.jpg  

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    An Oxy-Acetylene torch would be better, and frankly for brazing flush surfaces like this I'd much rather use bronze/brass braze and not silver. Silver does not take up space very well, and requires surfaces to be very close or it will not bond well. I'm no expert, but I am riding my own silver-brazed lugged bicycle around town when the weather is nice


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    Have you seen this - click on the guide PDF Safety-Silv® 56 | The Harris Products Group

    FWIW it sounds as if you may have a higher melting point rod than you think (mislabeled or missold?) or a ''short life'' flux - see the guide.

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    I agree with Atomkinder, looks like you are way shy on heat. A propane or MAPP torch doesn't compare to the heat a O/A will put out.

    Stuart

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    Quote Originally Posted by Limy Sami View Post
    Have you seen this - click on the guide PDF Safety-Silv® 56 | The Harris Products Group

    FWIW it sounds as if you may have a higher melting point rod than you think (mislabeled or missold?) or a ''short life'' flux - see the guide.
    Well silver braze should melt at ~1200°F (also listed in your link) but I have to wonder... is it a rod or a coil? At 3/32" it should have come in a round plastic case as a coil.

    That said, if fillet brazing is what is required, and bronze braze isn't desired, switch to 50N. 56% silver is not a good fillet material.

    Quote Originally Posted by atomarc View Post
    I agree with Atomkinder, looks like you are way shy on heat. A propane or MAPP torch doesn't compare to the heat a O/A will put out.

    Stuart
    In addition to shy on heat, my guess is the outside of the bolt is heating enough to wet the flux, but the core is still relatively cold. Hearth brazing could help, pre-heating the bolt, and/or a rosebud torch, but I don't know how effective or available those are in MAPP or propane.

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    Oh, another technique is to create a small coil of the braze and wrap it around the area that needs brazing. Heat alternately from the top and bottom and when the flux starts to wet, around the braze coil, focus a bit more of the heat on the bottom area until the braze is drawn into the gap.

    If the OP wants to try some 50N I have about 20g of Harris Safety-Silv 50N 1/16" that I will likely never use, and would be willing to ship it on for the cost of a small USPS flat rate box.

    50n.jpg

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    Heat the thicker piece,the bolt til it is orange,then the solder will flow. Also if the joint between the washer and bolt head has no clearance,then the solder will not hold the parts. About .0003/ .0005 clearance will do.
    I would punch 4 spots on the washer,this should raise the metal slightly,then flux and heat. I also would cut 2 or 3 pieces about 1/8" long and place them in the flux before heating. Heat slowly at first,I use a pointed rod to maneuver the pieces of solder. When the flux crusts over the solder will stay in place. Now increase the heat til the bolt and washer turn orange,not red.
    For something as small as a bolt and washer propane or mapp gas will do.

    mike

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    Looks to me like the bolt in the picture is coated. What coating? some melt way before silver solder and could give you a problem.

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    Quote Originally Posted by mike 44 View Post
    Heat the thicker piece,the bolt til it is orange,then the solder will flow. Also if the joint between the washer and bolt head has no clearance,then the solder will not hold the parts. About .0003/ .0005 clearance will do.
    I would punch 4 spots on the washer,this should raise the metal slightly,then flux and heat. I also would cut 2 or 3 pieces about 1/8" long and place them in the flux before heating. Heat slowly at first,I use a pointed rod to maneuver the pieces of solder. When the flux crusts over the solder will stay in place. Now increase the heat til the bolt and washer turn orange,not red.
    For something as small as a bolt and washer propane or mapp gas will do.

    mike
    Orange is over 1500°F, far too hot for silver brazing, and once the flux has crusted it's no longer cleaning the surface of the materials, and virtually useless as flux at that point.

    Juergenwt has another point regarding plating/coating too.

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    Silver brazing is sensitive to contamination. Any coating or plating has to be stripped to bare base metal if you wish the silver to wet the surface. Localized grinding will do but the ground surface has to be clean too. That is to say, don't use a sanding disk or belt previously used for paint, wood, etc because it will smear contaminants on the ground surface. Same with a worn disk where the backing glue is exposed,

    Do not solvent wash for the final cleaning (acetone etc). No solvent evaporates completely because, unless it's chemically pure, it carries dissolved contaminants of its own. Scrub the work with a powdered abrasive kitchen cleanser (Comet is my fav) immediately before brazing.

    I suspect you tried to silver braze passivated zinc plated (gold colored) bolts to that part.

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    If parts are plated dip your parts in muriatic acid (usually just one minute or less), then rinse in water, flux and sil-braze

    I routinely use the 56 silver for hyd tubing and fittings

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    I usually use oxyacet trying for a neutral flame. Depending on the part I heat with the inner cone or for smaller parts just the soft blue flame of the "jetwash".

    Cooking the flux black generally is not good. Perhaps change flux. I can't recall the brand but it came from McMaster Carr as white paste flux.

    I don't however put the silver anywhere near the heat until I think I have a dull orange heat in the joint area. I use the soft flame area trained on the joint area, touching the solder, to melt the solder at that point as the part also has plenty of heat into it.

    As mentioned above, parts need to be stainless wire brushed clean, filed to a bare surface, or belt-sanded, milled, whatever, but fresh metal no plating. Also not a bad idea to wire brush the solder with the ss bristle if there is any contamination or oxide visible.

    The 3/32 solder sounds pretty thick for your low heat, the 56% wire I'm using, is guessing .040 to .060.

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    I don't do much of the sort of work you are doing but I have silver brazed many thousands of silver contacts to copper bars and copper tabs on Nichrome ribbon for locomotive rectifier balancing resistors. First, you should try Eze Flow solder and get the right flux. We started out with Eze and switched to medium flow because it was running all over. We use it in leaf form and put a suitable piece under the part after wiping on a thin coating of flux. That way, as soon as it gets to melting temperature, the solder flows and everything is already in the joint. A little downward pressure finishes the job.. We used to get a flux from PRAXAIR that would make the solder flow out smoothly from the part, wetting Nichrome, which doesn't like to wet. They changed to a replacement that worked well enough but wasn't really the same. Unfortunately, I don't remember the name of the first flux, but a little searching should be able to find it now. That was before the internet.

    We started out with oxy-acetylene but went to natural gas and an oxygen generator, actually an extractor that takes it out of the air. The motive was economic and avoiding running out in the middle of a run. Propane with oxygen also works well. These gases with air are not so good because you are blowing 4 parts cold nitrogen on the part for every part of oxygen trying to heat it.

    Another method that works well is furnace brazing. I had to braze a bunch of brackets that wound up on U-505 in the Chicago Museum of Science and Industry. I set them up in a stainless steel pan in a pottery kiln with a copper tube through a hole in the top and connected to the argon from my TIG welder. Maintaining a low argon flow through it during the heat cycle produced perfectly clean parts. They did require a tiny amount of flux, even in the inert atmosphere, but not much.

    If you want, I will send you some medium leaf to try. Respond with your address to [email protected],com. My PM box is always full.

    Bill

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    Much good advice has already been given. Since silver soldering is new territory, I would suggest starting out with easy small parts until you find consistent success. You can solder clean steel if you can bring it up to a UNIFORM dull red heat. This is especially critical if attaching a small easily heated part to a more massive part. You have to start heating the massive part first until it is close to temp and then bring up the small part so they both are dull red and the solder wets both parts. I have used O/A for larger parts or oven soldered very large parts. But I also have used MAPP gas for plenty of small parts sometimes by making a small heating "hearth" by surrounding the part on 3 sides with fireplace brick to contain the heat better. Don't start heating at the joint though. Heat around the joint until the metal near the joint glows and then bring the heat to the joint and apply the silver. When it is done correctly the silver will flow into this joint quickly and thoroughly. And the silver will look very shiny. You will see that it wet out the joint well and will start to seep up the edges of the joint.

    pictured is a simple demo using a couple o duplex spikes. It is hard to photograph "shiny" but take my word for it the joint is shiny and you can see the silver started to creep up the steel all around. Once the joint cooled, I used vice grips to test the joint and the spikes bent, but the joint held. I have done this demo many time for shop visitors who tell me silver solder is unreliable or weak.

    Almost any silver solder flux will work if you don't burn the joint by heating it too much and too directly. Play with it a bit on simple stuff. Won't be long and you get a feeling for it. Silver solder is a great tool to get familiar with. And it really is easy once you get an idea of how to heat the joint.
    Attached Thumbnails Attached Thumbnails image.jpg   image.jpg   image.jpg  
    Last edited by dgfoster; 04-13-2015 at 08:56 AM.

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    I love that bike, hard tails the only way i go!

    and thanks

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    Quote Originally Posted by Limy Sami View Post
    Have you seen this - click on the guide PDF Safety-Silv® 56 | The Harris Products Group

    FWIW it sounds as if you may have a higher melting point rod than you think (mislabeled or missold?) or a ''short life'' flux - see the guide.

    funny i tried the harris today and had the same issue. The rods i have are unknown...=(
    same result as the known name brand i have so im hoping its me and not scammed solder lol

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    Quote Originally Posted by Atomkinder View Post
    Oh, another technique is to create a small coil of the braze and wrap it around the area that needs brazing. Heat alternately from the top and bottom and when the flux starts to wet, around the braze coil, focus a bit more of the heat on the bottom area until the braze is drawn into the gap.

    If the OP wants to try some 50N I have about 20g of Harris Safety-Silv 50N 1/16" that I will likely never use, and would be willing to ship it on for the cost of a small USPS flat rate box.

    50n.jpg
    i would love to try it thank you. I don't know what this 50n is but if you think its superior to what i have i would love to give it a shot,
    my goals is to get away form my 70amp stick welder, its too messy and ugly.

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    Quote Originally Posted by juergenwt View Post
    Looks to me like the bolt in the picture is coated. What coating? some melt way before silver solder and could give you a problem.
    Hi there, yes its a zinc coated, i was afraid the zinc would mess up the bond and simply peel off (kinda like what happened) so i always GRIND on a stone wheel and then wire wheel until i am very certain the zinc is gone and pure steel is what remains.

    i never considered there could be traces of zinc in my material....

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    Quote Originally Posted by mike 44 View Post
    Heat the thicker piece,the bolt til it is orange,then the solder will flow. Also if the joint between the washer and bolt head has no clearance,then the solder will not hold the parts. About .0003/ .0005 clearance will do.
    I would punch 4 spots on the washer,this should raise the metal slightly,then flux and heat. I also would cut 2 or 3 pieces about 1/8" long and place them in the flux before heating. Heat slowly at first,I use a pointed rod to maneuver the pieces of solder. When the flux crusts over the solder will stay in place. Now increase the heat til the bolt and washer turn orange,not red.
    For something as small as a bolt and washer propane or mapp gas will do.

    mike
    will try this tonight! =) thanks for the tip!


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