Question: What is a good method to attach a large sheet of honeycomb material around the entire outside diameter (OD) of a large 304L stainless steel cylinder so that it can be effectively brazed in place around that OD?

Answer: We have successfully brazed honeycomb sheets onto the OD of large cylinders in the past, but to do so requires that a number of steps be carefully followed. Take a look at Figure 1, which shows a shop worker assembling a sheet of honeycomb around the outside of a large 304L stainless cylinder during a preliminary “sizing” check.

A typical setup and brazing procedure for the parts pictured in Fig. 1 can be as follows:

1. After determining the proper length of honeycomb to use, cut it to that length so that it properly fits around the OD of the stainless cylinder and the edges of the honeycomb can properly butt together with no overlap.
2. After this, a sheet of AMS 4777 (BNi-2) nickel-based brazing filler metal (BFM) foil should be cut to the same width and length as the honeycomb sheet. I recommend either 0.0015-0.002 inch (0.04-0.05 mm) brazing foil be used, depending on the thickness of the honeycomb material used. For thinner honeycomb, use thinner BFM foil.
3. Thoroughly degrease/clean all mating surfaces to remove oil, lubricants, fingerprints, etc.
4. While wearing clean gloves, place a single layer of thin brazing foil around the OD of the stainless cylinder, over which you should then wrap the layer of honeycomb that you want to braze to the stainless pipe (using the BFM foil already placed below the honeycomb). Small pieces of tape can be used to hold them in position (tape will be removed prior to brazing).

Check back next time for the rest of this discussion.

Fig. 1.  Shop worker sizing a honeycomb sheet so that it can be cut to a size that allows its edges to butt against each other around the periphery (OD) of a 304L stainless cylinder.