Need advice on brazing/soldering

In my work I occasionally have to repair the metal housings of old power steering pumps. They are made of a stamped sheet metal steel. They have a small steel tube mounted to it for fluid return from the system. Many of these canisters have the tube bent or weakened where they go together. In most cases these parts are very lightly soldered together, so much pressure or vibration on the tube can cause the joint to leak.

I have been using a regular hardware store solder to repair these joints. It easily melts and flows into the joint. I clean and flux the area and heat it with a propane torch. It is usually a secure job and always much stronger than the original joint, but because this area can cause problems, I would like to make a stronger repair. I have heard that “silver solder” makes a stronger joint, but that there is also different kinds and fluxes required. Also I have heard that silver solder doesn’t fill up gaps well, but I don’t know if that pertains to the small gaps I run across.

I know that brazing would be better, but I do not have the torch equipment to do brass. I am looking for a higher grade or type of solder that will produce a stronger joint than standard hardware-store solder, that can be applied with a propane torch.

What do you recommend?

Somebody with a lot more experience than me should provide information, but I have worked some with silver solder. I used the kind for plumbing, I don’t know if that’s the same as you’re talking about. It’s a bit harder to work with because it doesn’t flow as easily as lead solder. You can still use a propane torch unless the amount of metal you’re heating is very large. I got better results with propane than with MAPP gas. Perhaps because the lower temperature of the propane torch allowed the temperatures of the joint to be more even. I used the regular cleaners and flux and they worked fine. The copper.org website says silver plumbing solder is stronger than lead (Thank god there’s a website creating greater awareness of copper). I used silver because I didn’t want to add any more lead to the pipes in my house. It’s a lot more expensive than lead, though.

Brazz/bronze braizing requires a lot more heat. If you have any plating on that part it will damage it. It may not have decorative chrome but a anti-corrosion plate like Cadmium.

Silver soldering is a form of brazing. A torch is required because the brazing rods, i.e. the soldering material, has a high temperature melting point.

I have the feeling that the soft soldered joints will not stand up very well to continued vibration.

Just to keep the terminology straight, brazing is the process of joining metal parts by adding melted material to the joint between the parts. Soldering with tin-lead or other soft, low melting-point material and with harder, high melting point materials are both types of brazing.

Welding is the process of joining metal parts by heating them and fusing the parent materials together without the addition of any other material.

The latter term is often used in the case of electric-arc brazing and in another 50 years of so the distinction will be gone, if it isn’t already. In fact, electric-arc brazing is unheard of. It’s always electric-arc welding, and with some justice because in arc welding there is considerable melting and fusion of the parent material in addition to the addition of the welding rod material to the joint.

This is a really appropriate question for SD, as jewlers, welders, refrideration workers,
and plumbers all use “silver solder” in thier trades, and in general are
all talking about different processes, or at least different alloys.

The 2% silver bearing solder sold for plumbing use AKA Sta-brite, isn’t
much stronger than old 50-50 (Sn-Pb) solder. Not fatigue resistant
at all. it really needs a substantil lap joint, as provided by
copper sweat fittings. Collectivly, all this low temperature stuff is known
as “soft” solder…fairly discriptive, as most can be dented with your
thumbnail.

To distinguish from these, I’ll refer to silver brazing. I don’t consider “Silver solder” incorrect usage however, just likely to cause confusion now that silver bearing soft solder is widely available.

This uses filler with much higher melting poing. Though you can still sometimes use a air propane torch for small jobs, Mapp gas, and air-acetylene work really well. OXy-Acetylene requires some care to avoid overheating, but is certainly usable. It depends on the alloy, but you need to get the metal showing some color, and perhaps to a cherry red for some. Orange is definatly too hot.

Silver brazing is MUCH stronger than soft solder, though not quite as strong as bronze brazing. (which can be stronger than welding)

There are several different silver brazing alloys. You can find a discriptive table in the McMaster-Carr catalog. (available on-line) I’ve only used the two most common, which I discribe below. In my experience, the guys at the welding stores know squat about this part of thier product line. If you have the McM-C table, you are an expert. Unfortunatly the prices are quite high. Yes I know it has silver in it. Silver is not THAT expensive. Jewlers suppliers might be good source.

Most alloys will work well on a variety of metals, with higher melting points, including stainless steel, Except as noted below.

Flux will be required for use on steel. McMaster-Carr 7693A1 should work well for you.

One alloy typically used in refrigeration work is called “sil-phos” due to its phosphorous content. This is an exeption to the above. This makes it self fluxing when joining brass or copper. It also will fill gaps fairly well, and leaves a substantial fillet. It usually come in long sticks with a rectangular or square cross section. It is NOT recommended for ferrous (iron based, what you probably have) or nickle (stainless) steel.

Another type is 45% silver. One trade name is “EasyFlow-45”. This stuff does NOT fill gaps,
and it leaves almost no fillet. When it melts, it has a lower viscosity, than water, and the flux kills any hint of surface tension. Ideally, joints should have a consistant gap of .0005 to .002". It will flow by capillary attraction long distances through these joints…several inches at least. It work great on mild steel, tool steel, stailnless, copper, brass. Carefully done, it will even stand up as a butt joint on a bandsaw blade, provided you scarf the joint to increase area. This is usually supplied as a coiled wire. It will be almost as stiff as piano wire…NOT ductile like soft-solder.

For your work, I would NOT use the 45% alloy, unless you can get the parts to fit really close. (maybe by expanding the tube some?). The 35% Ag alloy is said to fill gaps better, and that should give you some fillet. I would cautiously recommend this, and only hesitate because I have no first hand experience with that alloy.

You need to get the parts really clean…and that is a problem for you as they have soft solder on them. Abrasive (but not sand, leaves dirt embedded) basting or emory paper and lots of elbow grease will fix that. After you have the soft-solder off, use a CLEAN rag or Q-tip and either acetone or MEK to make sure there is no PS fluid near the joint. and don’t touch the area of the joint after that.

It will be very helpful if you can make the parts “self jigging”. Work the parts until they have a faily close fit. Then take an automatic center-punch, and prick the tube three places. Done correctly, this will raise three craters that will hold the part in position while you braze it. Three bumps are to hold the tube centered…ideally you’ll have an equal gap all the way around,

If the flux is a powder, of very thick, thin some flux using distilled water to the consistancy of very runny yogurt. Use an artist’s paintbrush, or a Q-tip, and apply flux to BOTH parts, every-where you want the filler to flow to. Try to be neat, because the filler WILL go there if there is flux and heat.

Since I haven’t used the 35% Ag filler, I’m not sure which technique below will work best.

SilPhos brazing is done like bronze brazing, or like a plumber does soft soldering: Heat the joint, then feed in some filler. Use the work, not the flame, to melt the filler. Move the flame around, and the filler will follow the heat. It may help to dip the rod in flux.

45%Ag brazing calls for a different techique. Very little filler is needed. One or more small pieces of solder (perhaps 3/8" long maximum) are placed on the joint prior to heating. The joint MUST either be self jigging, or a jig will be required to keep the parts in position. Use small enough pieces that the flux will hold them in place. The joint is heated, but try NOT to melt the filler with the flame. Heat the parts, and let the hot part melt the filler. It is best if you can apply heat from the opposite side of th joint from where the solder was placed. Once the filler melts, it may form drops that sit on the surface. If you poke or scratch at these drops with a sharpened wire dipped in flux, the flux will disrupt the surface tension and allow the filler to flow into the joint.

“Silver soft Solder” is a silver bearing tin alloy specifically designed for resulting in a bright joint. Melts in the 460 deg vicinity.
Regular brazing rod is a brass like alloy, requiring flux, and melts somewhere about 1200 deg.
“Silver/Hard/Jeweler’s Solder” melts at various temperatures. The hi temp type is used first on a complicated assembly, then as assembly progresses, lower and lower temperature types are used and themperature carefully controlled to result in the final product.
The manufacturer used a soft solder and there should be no need to change.
Clean all surfaces to be soldered with abrasive paper/cloth, wipe with clean cloth, flux with flux for the solder used. Use a good heavy duty soldering iron/gun, Heat the joint and apply the solder to flow and form a fillet around joint.

“In fact, electric-arc brazing is unheard of. It’s always electric-arc welding”

True brazing can be done using a carbon arc torch. I did it occasionally before I was set up with O-A.

This site has a lot of information about various solders. You may want to get a sample of this stuff, it might serve your needs very well. Low heat requirments, high tensile strength.

Your ‘regular hardware store’ solder could be anything – there isn’t a ‘regular’ product anymore. Solder has become very specific to the task. Plumbing solder is now all lead-free. Some electronic solder is also lead-free. The ideal solder is ‘eutectic’, which means it goes from a liquid to a solid without a ‘plastic’ state. Eutectic solder is desirable to eliminate the risk of deformation and other defects being introduced during the plastic state. For lead/tin solder, this means a 63/37 alloy.

I would have though that impossible. How do you manage to do that without the arc puddling the base metal?

The workpiece isn’t part of the circuit of a carbon arc torch, you could heat ceramic with it even.

The arc is between the tips two carbon electrodes, which are held about 90 degrees to each other. This arc looks, and is used similarly to a gas torch flame. It is hotter than, but womewhat inferior to an O-A flame:

-It is less focused
-There is nearly atmospheric levels of O2 in the flame, so scaling is worse.
-There is a lot of soot.

One is shown at the bottom of this PDF:
http://www.techair.com/acrobat%20files/Lincoln%20Electric/K1170.pdf

Isit possible to solder aluminum?I’ve heard that there are alloys that will wet aluminum, but it still must be difficult. What do you use as a flux?

I’ve bought some Al welding and brazing stuff from this site:

http://www.tinmantech.com/index.html

" real" aluminum brazing alloy, along with required flux. I have some, but the only thing I tried to use it on (a large intercooler) I got skeered (of causing other brazed joints to fail) before I got it hot enough, and ended up using JB-Weld instead (which has held up well in this application)

There are some zinc based (“3 in one”) rods around that will fuse aluminum…into a seriously weakened failure waiting to happen. Any time I am at any sort of exposition, etc. there is a booth hawking them. That is not what site above is selling.

And your right, when brazing or O-A welding aluminum, flux is one of the keys…having the right lens to veiw the process is another.