CAB Maintenance Tips

Checking the Braze at the Furnace Exit
Part 1 of 5  - Color

Dark Brown:  This dark brown discoloration in localized areas is indicative of organic coloration.  Organic material is mainly found in oil or carbon chain based products.  The oil used in fin machines should be an evaporative oil such as Martol EV-15 or punch oil substitute.  This prevents discoloration because 95% of the oil  evaporates by the time the part reaches 150°C (300°F). Be careful when using a wet flux application because the water-flux mixture will tend to run off oil contaminated areas.

Light Brown:  Light brown areas are a sign of oxygen in the braze zone.  This is not necessarily a problem.  You might be using enough flux that the parts are still brazing well.  It is important to monitor the instruments to make certain they are functioning correctly.If the instruments are indicating an excellent atmosphere, polish a small piece of copper tube and send it through the furnace.  If the part is still shiny with a blue tint, the atmosphere is good.If the copper tube turns black or has a black residue, there is a problem with the atmosphere, and probably loose airways. (Loose Airways will be covered in Part 2)  Check atmosphere curtains, nitrogen supply purity, holes in the muffle and wet parts entering the furnace.

Black:  Black usually indicates contamination.  Contaminants could be in the washer, fluxer, operator's hands or in some operation that might be carried through into the next stage.Check the pH of the washer.  This value should be around 8.  An overly caustic solution will etch the part and require a de-smut, or removal of the etching, not recommended.  Reduce concentration of the cleaning solution and try again. We suggest that you take default readings when all is running well.

For more information on CAB Brazing, check out http://www.secowarwick.com/aluminumbrazing.html

| Go to Part 2 Airways |

The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement.