How to Silver Solder Steel to Copper

Copper and steel are frequently used together in fabricated parts, tubing, mechanical equipment, and repair applications, but joining these dissimilar metals requires an alloy that will bond to both surfaces.

Steel is primarily an alloy of iron and carbon, with other elements such as silicon, boron, manganese, chromium, molybdenum, nickel, and vanadium, added in different combinations to produce specific properties.  The composition and intended use help distinguish the many types of steel, including spring steel, low alloy steel, high alloy steel, carbide steel, stainless steel, tool steel, mild steel, carbon steel, and manganese steel, to name a few.

SSQ-6 combines silver solder and flux in a syringe, allowing the material to be placed directly where the copper and steel meet before either metal is heated.

In this video, Mike silver solders a 1/8-inch steel plate to a copper end cap using SSQ-6 silver solder paste and a propane torch.

It is the paste version of Muggy Weld SSF-6 Silver Solder Rod, and can be used to join steel to copper as well as other compatible dissimilar metal combinations.

Why Silver Solder Steel to Copper?

Steel is found throughout automotive, construction, mechanical equipment, shipbuilding, railroad, aircraft, mining, energy, appliance, surgical, and farm equipment applications.  Copper is also common in tubing and other systems, so repairs and fabrication work often create situations where the two metals need to become part of the same assembly.  Silver solder provides a practical way to create a metallurgic bond between the two without having to melt either parent metal.

For another application using the same paste, see silver soldering copper with SSQ-6.

Clean Both Metals Before Applying SSQ-6

Clean the steel plate and the copper end cap thoroughly before brazing.  The surfaces that form the joint need to be free of contamination so the silver solder can bond to the parent metals.

Pay particular attention to the edges of the metal to be joined.  Once the two pieces are clean, position them correctly before applying the paste.

Good preparation matters even more with a dissimilar-metal joint, because the filler needs to wet two different parent metals at the same connection.

Apply the Silver Solder Paste While the Parts Are Cold

SSQ-6 comes in a syringe, allowing the paste to be placed directly at the joint.  Apply it to the cold steel and copper before using the torch.

The syringe format gives you control over how much filler is used and where it is positioned.  This is useful around an end cap, where the silver solder needs to follow the shape of the connection rather than cover a large surface.

Once the paste is in place, begin heating the parent metals.

Heat the Steel and Copper Together

Torch technique matters when two different metals are being joined, because copper and steel do not respond to heat exactly the same way.  Instead of pointing the flame directly at the SSQ-6 paste, broadly heat the parent metals and gradually bring the joint to working temperature.

Balance the Heat Between Copper and Steel

Copper conducts heat quickly, so the two sides of the joint may not warm at the same rate. Keep the propane torch broadly moving across the work area while heating the 1/8-inch steel plate and copper end cap.

As the metals reach the proper temperature, the SSQ-6 melts and flows into the joint, bonding the steel directly to the copper.

Let the Joint Pull in the Silver Solder

The filler should flow through the heated connection rather than remain as a mound of paste on the outside.  Keep the torch moving around the joint as the SSQ-6 melts and wets the parent metals.

The paste was applied before heating, making the syringe format particularly convenient for fittings, end caps, and other areas where precision application is required.

For a different dissimilar-metal application, see how SSF-6 joins steel to brass in an RC plane project.

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Updated 9/23/26

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