Hello,
I need some advise in brazing this material. I'm new to the process so I may not have all of necessary info. I'm trying to fit a cast propeller blade with an oval foot into a machined hub with a slot to match the hub. One problem is that they are tack welding the blades in place...then when it goes into the furnace the blades have fallen out of place. I know that I can make a fixture to hold everything in place...but is there an easier simpler method. My other problem is that the fit of the cast prop. to hub has inconsistencies so it sometimes will leave a .025" gap in areas. Is there something in the brazing process that can fill these large gaps? I understand that the requirement is .001-.005" but that is just not going to happen with our cast props. Plus, they are getting really sloppy now and in trying to fill the gaps, they're putting an obscene amount of filler and it's just running all over the place.
The reason for me going to vacuum brazing is only because the machined hub needs to hold it's precise dimensions. I'm up for suggestions on different methods if there is no solution with vacuum brazing. This is costing me a great deal of $$$ having to get these put in the furnace over and over to fill up the gaps.
Thanks in advance for your input!!!
Brandon
Hello Brandon, I am not a brazing guru by any means, however you had mentioned some tolerancing regarding fit and I believe also some limitations to this tolerancing. My experiences with soldering and brazing in various instances leads me to believe that if you have excessive fit-up gaps you could have strength failures as well. From what I have been led to understand there are some real differences in the finished realized strength of brazed joints when they are of the correct thicknesses as opposed to having excessive thicknesses of fill between parts. I think that you have somewhat answered your own question by considering that you may have to make some changes in the way that the parts are machined or the way in which they are fixtured prior to being processed. Just a few thoughts to consider. Best regards, aevald
Aevald is right- if your joint clearances are not controlled better, there can be serious decreases in mechanical properties. This is especially true if you are brazing with a nickel-based filler metal. There are ways to fill large gaps, namely blending pure nickel powder with your filler metal and filling the gap, then applying undiluted filler metal over the top. I would not recommend doing this in a propeller application that is subject to fatigue and vibration. Feel free to contact me if you would like to discuss this application further- we routinely vacuum braze 17-4 and 15-5 with a variety of filler metals.
Justin Liguori
Scarrott Metallurgical
www.scarrott.com
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