Today, we take a brief look at the use of carbon-fiber reinforced carbon (C/C) for fixtures, and in coming weeks we'll look at other available fixturing materials that can replace some of today's commonly used metallic materials.
One of the large-cost items in any furnace-brazing run is the cost of heating all the fixturing inside the furnace chamber. The more fixture material that is present and the heavier and more massive the fixturing materials used, the higher the operating costs associated with heating and then cooling that mass of fixturing up to, and down from, brazing temperature. In some brazing furnace loads, the cost of heating/cooling the fixtures represented the bulk of the cost of that brazing cycle.
Remember, there is no "free ride" in furnace brazing. Every pound or kilogram of fixturing you put inside that furnace absorbs heat energy (BTUs/calories) and must be paid for. The more weight you put into the furnace load, the more expensive that load since every BTU/calorie absorbed by the fixturing and by the actual parts being brazed costs you money. You can make a lot more money by cutting way back on the weight/mass of the fixturing used so that more and more of the costs of each cycle relate only to the actual parts being brazed.
Do a review of the fixtures you are now using for your furnace brazing, and make a commitment to do the following: (1) eliminate as much excess fixturing as possible (it is not hard to find fixtures that really aren't necessary, such as overweight baskets, heavy added grates, dead-weights, etc.) and then (2) try to reduce the actual weight of the needed fixturing that remains.
One way to achieve this weight reduction is to look at the use of C/C fixtures. C/C is growing in popularity because of its excellent high-temperature stability and very light weight. Although it may be more expensive than some of the more commonly used fixture metals, C/C's low mass, low weight, long-term high-temperature stability and lack of distortion should make it fairly easy to recover those additional costs in a very reasonable period of time.
NOTE: Industrial Heating (IH) contains a lot of information in each monthly issue about fixture materials for furnaces, and a lot of that information centers on C/C. It is worth exploring the pages of IH each month to find many of the good sources for these newer C/C fixtures.
A number of brazing shops have been able to eliminate 90% or more of the weight of their fixtures by switching from steel to C/C. As an example, a steel furnace grate weighing almost 70 pounds (30 kg) was successfully replaced by a C/C fixture for the same purpose, but the C/C fixture weighed only about 5 pounds (2 kg). With far less thermal mass to heat/cool during that furnace cycle, operating costs were significantly reduced.
An additional benefit of the C/C fixture material is its long life (with proper care) due to thermal stability, lack of thermal distortion, strength retention at brazing temperature and exceptional creep resistance. Their lack of distortion results in elimination of a lot of the repair costs normally associated with metal fixtures over time.
Brazing shops are in business to create profits for their people. An excellent way to do this is by lowering the costs for each furnace brazing cycle by cutting down on electrical power consumption. Furnace cycle time can be reduced dramatically by eliminating a lot of the weight processed through each furnace cycle. One way to do this is by evaluating the use of C/C fixtures in your furnaces to replace the much heavier metal fixtures you're currently using.
C/C technology has advanced to the point that many brazing houses need to take a closer look at this technology to help them significantly reduce operating costs and improve productivity.