This is a question that arises once in a while, and needs to be taken seriously. Fortunately, for most of us, problems with Certificates of Conformance (or Certificate of Compliance) are very rare. Most manufacturers of brazing filler metals (BFMs) are reputable companies who pride themselves in being able to produce high-quality BFMs in such a way that the BFM product is homogeneous, and its chemistry is carefully controlled in a manner that can guarantee that it fully meets the requirements of the specification(s) to which it is being produced.
The Certificate of Conformance will show the BFM specification(s) to which it conforms, and the customer to whom the “cert” was sent should be able to fully rely on the accuracy and truthfulness of that document.
Every once in a while, a customer, using a BFM product (paste, wire, preform, etc.) which they have purchased from their supplier, discovers that the BFM product does not perform the way it is supposed to, and many questions begin to surface about that product they have received:
- Is the product actually that which is reported on the Cert?
- Is the product faulty?
- Am I doing something wrong?
- Has my brazing furnace changed and no longer working properly?
- Has someone in my brazing shop accidently grabbed the wrong product from the shelf?
These, and other questions, can begin to arise, and must each be evaluated in order to determine the answer to the question: “Why isn’t this BFM working for me?” First things first. The first thing that I suggest you do if you receive a BFM that appears to be questionable is to test it in your furnace along with a sample of the same BFM from another lot that you know is okay. This is very important.
Recommendation: Place a sample of the new BFM onto a base-metal sheet coupon (this coupon might be a small, flat plate of stainless, or from sheet, or from a different base-metal that is compatible with the BFM in question). The size of the test-coupon does not need to be large, but should be large enough to allow you to melt two different samples of BFM on it. Place a sample of a known good BFM from a different heat/lot of the same alloy next to the questionable BFM on the same flat coupon. Allow enough distance between the two samples so that they can melt separately and not blend together when melted.
Run the coupon in your brazing furnace at a temp of 100°F (50°C) above the published liquidus temperature for that particular BFM, with NO hold at that brazing temperature. As soon as the coupon reaches that brazing temp, allow it to immediately start to cool. Obviously, if the new BFM does not melt correctly and the known good BFM sample melts and flows nicely, then you know that the problem is not with your furnace or procedures, but is a problem with the new batch of BFM you received.
Note: That is why I always suggest you do a quick “coupon test”, as described above, before you start doing a lot of checking with your supplier or doing a lot of questioning about your in-house shop procedures. Run the coupon FIRST! The answers you receive from that coupon-test will quickly enable you to move in the right direction with your search for answers.
BFM Chemistry-Tolerances vs. Brazing Temperature Used
Please always remember that each constituent in the BFM chemistry has a tolerance allowance. Thus, the exact, precise amount of each element in that BFM will vary slightly from batch to batch, and this can affect its melting characteristics slightly. Thus, it must always be understood that there is a tolerance-spread, too, for the melting temperatures of each BFM.
Example: I remember a person telling me a number of years ago that he wanted to return some BFM that we had supplied to him, because when he had set his brazing furnace right at the liquidus temp for that BFM he was using, the BFM didn’t flow correctly, and he wanted us to take it back.
Because of the tolerance-spread in the chemistries mentioned earlier, it is ALWAYS a good practice to braze at a temperature well above the published liquidus temperature for that particular BFM. I recommend that brazing be done at 100F/50C above the published liquidus of the BFM, unless you have specific experience or knowledge that you can braze at a different temp for a particular BFM.
Is a Certificate of Conformance Worthless If the BFM Doesn’t Work?
Assuming that you have run the coupon-test with two different heats/lots of the BFM in question (as I recommended earlier in this article), and assuming that the results show you that there is a problem with the new batch of BFM you received, and thus there is not a problem with your furnace equipment or procedures, should you then just assume that the Certificate of Conformance (C of C) you received is totally worthless?
NO — that C of C is a legal document, and now it takes on REAL value! You can now take that C of C and work with your supplier, saying (for example): “Here is the C of C you sent to me with the material, and this is the material you sent to me. The material you sent doesn’t work, but your cert promises that it will. Therefore, based on that promise (the C of C), please replace this material with a correct and properly-working batch of the BFM in question.”
Conclusion: Fortunately, non-conformance to Certificates of Conformance (or Certificates of Compliance) is rare among the current suppliers of BFM to the brazing community. But always remember two things: (1) always test the alleged non-conforming material via a test-braze on a coupon on which you’ve also included some known, good BFM; and (2) IF the newly received BFM does indeed have a problem, remember that the C of C that came with it is a legal document that suddenly takes on real value for you, allowing you to get restitution (replacement of the incorrect BFM) from your supplier.
Important Question: Do you always insist on getting certificates of conformance/compliance for each batch of BFM you receive from your supplier?
Remember: A certification of compliance (or certificate of conformance) merely indicates that the supplier is telling you that they certify that the BFM meets a certain industry spec for chemistry, but it doesn’t actually give you the exact chemistry for that particular lot/heat of BFM that they have sent to you.
For an exact chemistry you would have to request a Certificate of Actual Chemistry (different suppliers may use different names for such a document), which can be more time-consuming to produce, and for which you may be charged a fee. You should not be charged any fee for receiving a certificate of conformance (or compliance)..