Frequently Asked Questions
Brazing
Question: What are the key factors to achieve good results in brazing?
Answer: The important factors are: 1) Use clean parts
2) Apply correct amount of filler metal
3) Do not overheat paste during drying
4) Use suitable fixturing during brazing
5) Check that the oxygen content in the furnace is less than 20 ppm
6) Apply correct brazing temperature on the parts.
More detailed explanations can be found in the Handbook.
Question: Do I have to clean the parts before assembling and brazing the core?
Answer:
In normal cases not. The fins are clean enough after forming and the tubes are clean enough for coating after welding. Normally the headers, tanks and side supports are clean enough, too. Sometimes, if the stamping oil or emulsion is dirty and causes staining on the parts, they have to be cleaned.
Compatibility
Question: Can I use CuproBraze materials for soft soldered heat exchangers?
Answer: You can use the tube brass and header brass but not the fin copper. The fin copper requires treatment at the brazing temperature to reach the required thermal conductivity level.
Question: Can I braze CuproBraze and aluminium products in the same furnace?
Answer: From brazing point of view it is usually possible as the protective atmosphere is the same and the brazing temperatures are close to each other. However, it is recommended that a furnace is dedicated to only one of the metals, because copper deposits on aluminium surfaces can cause pitting corrosion on aluminium. Therefore, switching between the materials is not recommended, unless the furnace is carefully cleaned between the runs.
Corrosion resistance
Question: How is the corrosion resistance of CuproBraze heat exchanger compared to soft soldered one?
Answer: It is generally better. On CuproBraze heat exchangers the materials are of equal nobility, so galvanic differences are practically eliminated. On soft soldered heat exchanger the solder is less noble than fin and tube materials and can suffer from galvanic attack in a corrosive environment. CuproBraze tube alloy contains 85% copper which gives high resistance against dezincification and stress corrosion cracking.
Environmental
Question: Is CuproBraze a leadfree process?
Answer: Yes, the brazing alloy contains copper, nickel, tin and phosphorus.
Repairability
Question: Can CuproBraze heat exchanger be repaired in the field?
Answer: Yes, repairability is one of the big advantages, especially in remote areas, where availability of spare parts is limited. You can repair it with leadfree soft solder (for example 97% tin, 3% copper) or with common silver containing brazing alloys.
More to come soon .....