Anyone here experienced in silver soldering?

[country gent]

Did you try cleaning the solder pull a length thru a clean scratch pad a few times.

[Hannibal]

Again, what silver solder are you using and what's your heat source? If it's an oxy acetylene flame you want neutral or slightly carburizing. An oxidizing flame will prevent proper wicking.

Look at post #14. I answered your questions.

[Hannibal]

Did you try cleaning the solder pull a length thru a clean scratch pad a few times.

No, I did not try that. I did cut about 2" off the end before I started.

[country gent]

any oxidation in the process is dooming. it over time the solder may have oxidized it should be bright and shiny not a dull grey. All materials needs to be clean.Best is new solder flux and fresh cut materials sanding or grinding is next then come wire brushes.
When I have to solder copper tubing its 60 grit emery to clean not the wire brushes. brighten the end and inside flux heat and apply solder its a quick zip as the solder flows and fills.

Another is you have to have "room" in the joint for the solder. like glue you can have to tight of a joint for it

[Hannibal]

any oxidation in the process is dooming. it over time the solder may have oxidized it should be bright and shiny not a dull grey. All materials needs to be clean.Best is new solder flux and fresh cut materials sanding or grinding is next then come wire brushes.
When I have to solder copper tubing its 60 grit emery to clean not the wire brushes. brighten the end and inside flux heat and apply solder its a quick zip as the solder flows and fills.

Another is you have to have "room" in the joint for the solder. like glue you can have to tight of a joint for it

I appreciate your advice. I'm a bit aggravated right now so I'll think about it and try again tomorrow. So far as appearance the solder looks very clean, not gray. Usually I have no trouble at all so I'm considering causes that I normally wouldn't. Perhaps the flux and the solder aren't compatible? IDK.

[Martin Luber]

Same problems here. The original flux dried up to a hard crust. I cant redisolve it with anything

What should I use for flux…even tried boraxo soap

[Hannibal]

Same problems here. The original flux dried up to a hard crust. I cant redisolve it with anything

What should I use for flux…even tried boraxo soap

Hopefully someone has a good suggestion. Right now I've no good ideas. Appears we are in the same boat.

[Hossfly]

I use the white flux in plastic bottle and reconstitute it with water. Think it’s called sta silv.

[Hannibal]

I use the white flux in plastic bottle and reconstitute it with water. Think it’s called sta silv.

Found that on line. Any particular solder you like? I think for starters I'm just going to try a new combination and avoid acid core this time. I presume things like acid core solder have a shelf life but right now that's just a guess.

[Winger Ed.]

I've had good luck with the American made Sil-Fos brand.
The sticks imported from China always gave me fits.

They make it in different amounts of Silver content.
The more Silver content, the easier it is to work with..... and a little more expensive.
I think it was either 15 or 20 that I used in years past.

It comes in a stick that looks like a coat hanger wire hammered out flat and about 18 inches or so long.
A good hardware store should have it on the shelf.

[DougGuy]

I silver solder torch heads on tubes, stainless tubes and stainless torch head. Metal is very clean, sanded shiny, I am using either Harris stay silv or Sua white flux No.1

Solder is 56% silver, it has a high melting point which makes it perfect for soldering cutting torch heads on tubes. Brush the flux in the holes and on the tubes then stick the parts together, clamp them for no movement this is critical. I get the metal a good cherry red/orange pull the flame off and stick the solder on where I want the solder to flow, give it a few seconds for the solder to heat up and if it doesn't break and wet the joint, pull it off and heat some more, when it's hot enough it will melt and flow like butter. It is a silvery bronze color on the spool and finishes really pretty like gold.

I use a No. 3 tip oxy/acetylene. Sounds like you don't have enough heat or enough in the right place and I have never used that solder, I have used 15% soldering copper nickel, 45% is a good strong solder and it's easy to work with, use oxy/acetylene it puts intense heat in small places near the weld, lesser torches have to heat too much of the surrounding area.

[M-Tecs]

The Harris Stay-Silv White Paste Brazing Flux doesn't go bad but it does need water to reconstitute if it dries out. I've silver solder hundreds possibly thousands of parts with silver solder. That has always been done with oxy/acetylene torch or a heat treat oven.

Never used an air/acetylene torch or acid core silver solder so I have no firsthand experience with most of what you are using.

[Hannibal]

I silver solder torch heads on tubes, stainless tubes and stainless torch head. Metal is very clean, sanded shiny, I am using either Harris stay silv or Sua white flux No.1

Solder is 56% silver, it has a high melting point which makes it perfect for soldering cutting torch heads on tubes. Brush the flux in the holes and on the tubes then stick the parts together, clamp them for no movement this is critical. I get the metal a good cherry red/orange pull the flame off and stick the solder on where I want the solder to flow, give it a few seconds for the solder to heat up and if it doesn't break and wet the joint, pull it off and heat some more, when it's hot enough it will melt and flow like butter. It is a silvery bronze color on the spool and finishes really pretty like gold.

I use a No. 3 tip oxy/acetylene. Sounds like you don't have enough heat or enough in the right place and I have never used that solder, I have used 15% soldering copper nickel, 45% is a good strong solder and it's easy to work with, use oxy/acetylene it puts intense heat in small places near the weld, lesser torches have to heat too much of the surrounding area.

Well I'm certain heat isn't the problem as it melts immediately when touched to the parts. I am trying to solder mild steels together and I'm not sure if I need a different alloy for that. Again, what confuses me is I've used this in the past and it worked great. So something has changed apparently but I've no idea what.

I'm in the process of trying to determine what alloy is the best fit for my use and what flux I need. I definitely want to avoid acid core going forward. May or may not be the problem, just trying to eliminate future problems.

Right now the solder I have is behaving as if the parts aren't clean or are oil contaminated. But I'm certain that isn't the case.

[country gent]

Both the sta silver white and the black can be reconstituted with water its a job takes awhile to soak in then break the chunks up and add water to a thick paste. I have ran a drill bit into the hardened mass to break it up then add the water.

Silver solder like braising rod has the flux in a dry coat on the out side. Flux core and acid rosin all denote a lead tin solder or low temp. On your roll of solder whats the designation? 30-70, 60-40, 45%, 55%. The last 45 silver solder I bought was almost $80.00 an ounce. Silver solder is almost like a spring wire very stiff. Lead tin is soft and easily bendable. Silver solder is a small dia 1/16" or so soft solder is a bigger dia. Silver solder also has a goldish tint.

[DougGuy]

Well I'm certain heat isn't the problem as it melts immediately when touched to the parts. I am trying to solder mild steels together and I'm not sure if I need a different alloy for that. Again, what confuses me is I've used this in the past and it worked great. So something has changed apparently but I've no idea what.

I'm in the process of trying to determine what alloy is the best fit for my use and what flux I need. I definitely want to avoid acid core going forward. May or may not be the problem, just trying to eliminate future problems.

Right now the solder I have is behaving as if the parts aren't clean or are oil contaminated. But I'm certain that isn't the case.

Get some stick solder no flux, use white flux in the jar. Alloy depends on how high a temp you want the steel to tolerate. Generally the lower the % of silver the lower the melting temp for the solder and the less strength it will have, but sounds like you have acid core soft solder which is ehh ho hum for what you are wanting to do with it. Not very strong up against hard solder.

[Hannibal]

Both the sta silver white and the black can be reconstituted with water its a job takes awhile to soak in then break the chunks up and add water to a thick paste. I have ran a drill bit into the hardened mass to break it up then add the water.

Silver solder like braising rod has the flux in a dry coat on the out side. Flux core and acid rosin all denote a lead tin solder or low temp. On your roll of solder whats the designation? 30-70, 60-40, 45%, 55%. The last 45 silver solder I bought was almost $80.00 an ounce. Silver solder is almost like a spring wire very stiff. Lead tin is soft and easily bendable. Silver solder is a small dia 1/16" or so soft solder is a bigger dia. Silver solder also has a goldish tint.

Well this stuff is on a small roll and unfortunately does not list the content on the label. It's pretty soft/malleable and is .062" in diameter. Bernzommatic SAC300. Checked online and can't find any information on content there, either. I think I'll just toss this and start over.

[Hannibal]

So. I'm unable to determine the content of the solder I have so I'm going to dispose of it and start over.

For those of you who understand silver soldering, what would you choose to solder 1/4" mild steel together? There are a pair of pins internal to aid locations and it's a tight joint. Also would appreciate a flux recommendation.

[farmbif]

if you wanting to join large pieces of steel why do you want to silver solder it? ive always believed that the 5 and 15 silver solder rods like are used in HVAC are for bronze, brass and copper joints or joining any of those materials together and when joining steel, like hydraulic joints or gun sights 45-55% silver solder is needed. the silver solder is very expensive. but I went to welding/metal fab school almost 50 years ago and maybe things have changed with new materials and such.
why not braze or weld the large pieces of steel together?

[Rockindaddy]

There is no such thing as acid core silver solder or silver braze. You must be using a lead/ tin base acid core solder that melts around 650* Silver braze requires an oxygen-acetylene torch and melts at 1500* The flux is white and looks like dry wall compound. Been silver brazing since I was a kid 60 years ago. Its easy! Silver braze solder wire is just shy of $95 per small roll. Only tiny parts can be silver brazed with a propane torch. Go see your local welding supply shop They will know what you are doing wrong.

[country gent]

what is the physical size of the joint length and width in inches