A lot of focus is (quite rightly) given to ensuring the selection of the appropriate braze filler metal, however the quality and appropriateness of stop-off materials in modern vacuum furnace brazing is often overlooked.
We all know the purpose of a stop-off and the effectiveness of them, but it is precisely because they can be so effective that in some braze environments the need to control the usage of these materials is discounted. It is not uncommon for the braze joint to be overfilled with alloy material and then compensated by overuse of stop-off material. This will not only potentially cause an untidy join but is also an unnecessary cost and waste of materials.
Likewise, you’ve possibly witnessed people trying to correct their stop-off “slips” by trying to clean off stop-off with an acetone or alcohol solution. This is unlikely to be an effective solution, remains of the stop-off will remain in the crevices and gaps which often leads to difficulties with the braze and prevents the filler metal from properly flowing.
It’s important therefore to ensure you are not only using a high-quality product but also your application is controlled and accurate, which is why Vitta produces it’s two highest quality stop-offs in multiple formats for the most effective application.
Vitta 1AL Braz-Stop is for use on most base metals without reactive elements and for general purpose brazing. It was originally developed for nickel brazing but has also been used for some copper and silver brazing systems. Specially processed and highly pure it is both chemically and thermally inert.
Vitta 1YT Braz-Stop is [PP1] designed for use with base metals containing reactive elements such as titanium, aluminium, zirconium and other reactive elements.
Both are available as:
- Paint – With no objectionable odour, no requirement to remix for at least 12 hours, easily thinned, a working temperature of over 1600C and easy clean-up this provides a good all-purpose solution.
- Paste – compounded specialised organic binders produce a very stable paste that is dry to the touch after as little as 20 minutes. No separation occurs so no remixing is required. The binders will decompose well below the working temperature so there will be no binder[PP2] residue in the Braz-Stop materials.
- Tapes – Vitta has been pioneering tapes for over 50 years. The self-adhesive tape provides an easy way to deliver uniformity with no waste and no mess. All the binders and adhesives will decompose well below working temperatures. Tapes can be made to bespoke sizing and start at just 0.005” thick and 0.250” wide.
- Preforms – Bespoke thickness and design – protect holes from filling with molten material by using self-adhesive washers.[PP3]
Vitta has been at the forefront of braze alloy technology for over 50 years. Discover for yourself why more furnace operators are turning to Vitta for their brazing requirements.