Braze Wetting Test
Braze Wetting Test
Before you can create a good braze joint, you have to have clean materials that wet well. In this case wetting means that the braze alloy flows over and sticks to the surface.
Over the decades we have solved a great number of brazing problems very simply.
What we do and what we recommend is that you quit trying to solve the braze problem by brazing complete assemblies. Instead you take the individual components, put a small amount of the flux and braze alloy you’re using in the middle of them and heat them up. If the material balls up in the middle then the surface is not wetting. If the material flows out into a nice flat puddle then the surfaces wetting very well.
Roughly, roughly a piece of 50% silver braze alloy that is 3/64” or .046 inch and .320 inches long should flow out to be about the size of a dime. This is a very good flow. You can get better flows. I once got braze alloy to flow over carbide in such a manner that the braze alloy was thin enough to see through. This was done in the lab and had a great deal of value in research but is not particularly relevant in production.
Please do not get hung up on exact measurements for any of this. The idea is to have very little braze alloy, maybe 10% of what you would use in production. You heat this up with flux or however you do it, just as you would in production. You see how well it flows.
In the best case the braze alloy will melt and flow out. There may be intermediate balling where the braze alloy draws upon itself into a ball or a sphere and then flows out. In this case the surface is not as good as if the braze alloy just flows out but it makes a perfectly satisfactory surface for bond strength and impact protection.
If the braze alloy forms a ball and will not flow out, if it forms a highly irregular shape or if the braze alloy all runs off one side and does not stick to the top then you have found at least part of your problem.
Tags: brazed tools
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