What You Need to Know About Brazing Steel to Copper

Brazing steel to copper is a process in which steel and copper are joined together using a filler metal that has a lower melting temperature than steel and copper. Once the filler metal has melted, it fills in the gaps between the two metals through capillary action. The filler metal is then cooled to join copper and steel together. This is a well-known technique in the metal joining industry that is frequently used to create high strength joints, valves, and parts for assembly. Although this is a process that is very commonly performed and well-documented, certain conditions need to be met, and hazards need to be accounted for in order to avoid injury and a poor brazing of the metals.

What Conditions Need To Be Met?

Capillary action only works when the space between the copper and steel parts being joined is extremely small, such that surface tension between the melted filler metal and the joining metals can act to lift the metal through the entire space. Thus, the clearance should stay strictly between 0.001 to 0.005 inches. The next step to account for in brazing steel to copper is to ensure that the filler metals and are properly cleaned. Any contamination will result in an incomplete joining of copper and steel, resulting in a joint that cannot be used. Once all the metals are cleaned, the chemical compound flux must be applied to the joining metals to prevent corrosive oxides from being formed during the heating process. In the case of brazing steel to copper, phosphorus-free filler metals must be used to avoid joint failure due to the formation of phosphides that weaken the joint’s strength. Finally, ensure that heat is applied equally and evenly amongst the steel and copper pieces so that the filler metal melts evenly and completely fills the clearance between the two metals.

What Could Go Wrong?  

As high temperatures are used to melt metals, extreme caution and safety must be taken to avoid injuring yourself and others around you. Any materials with the slightest degree of flammability must be removed from the vicinity, and the appropriate safety equipment must be worn until all materials have cooled to room temperature. It may be to your advantage to have another worker present to guide you through the process and ensure that all safety protocols are being followed. Finally, ensure that you are familiar with the safety profile of the filler metal that is being used. These should come with a comprehensive safety profile that advises workers on how to properly handle them and the potential dangers that could arise from their misuse. Overheating some filler metals could result in the release of toxic materials in the atmosphere that might be accidentally inhaled.


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