strength of brazed joints

anyone know, ballpark or otherwise, what the relative strength of a braze is, per square inch?
numbers for solder, silver, etc..
and, out of curiousity, how do you decide between welding or brazing? i've seen great jobs done on brazed gocart frames, for example, where i would have probably just have mig'd it.
thanks, -tony
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Regular brazing is pretty strong being around 40,000 psi. At this level it matches grey cast iron. A perfect silver solder joint professionally done can reach over 100,000 psi. I know it just doesn't sound possible but it is really amazing when done properly. Ever looked closely at the jaws of your Vise Grips??? I don't think you will ever see a pair of Grips that separated at the jaws and stamped metal frame. If you have a torch outfit and have to join thin tubing brazing is a good choice. You use less heat than welding and require less skill. Brazing is often a good choice for cast iron repairs or joining tool steels to other assemblies. Silver soldering by the way is actually silver brazing using a silver alloy. Randy

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I dissagree with the "use less heat" part. It is true that the joint doesn't reach the same temperature as during welding, but with brazing you need to spread the heat over a larger area than with welding and you also have to heat the area at a slower rate than when welding. This is in order to avoid overheating the joint and rendering the flux useless. Because of that I expect to see more heat distortion when brazing something than when welding it, particularly when MIG welding it.
As for when to use brazing over welding, the obvious answer is when joining dissimilar metals. A less obvious answer is when the parts being joined are so small or thin that welding would likely melt holes in the parts or would even melt the whole parts away.
Brazing strenght depends to a large degree on the gap at the joint. If the gap is too narrow or too wide you can't reach the 100 ksi mentioned earlier. Controlling the gap is a challenge because we are talking about a few thousands of an inch in the optimal case and the parts can expand by much more than that as you heat them to brazing temperature.
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