Which solders are most commonly used for making solder joints on copper tube?

The choice of solder for joining copper tubes significantly impacts the strength and integrity of the connection. The most commonly used solder joints for copper tubes are based on the lead-tin alloy, specifically the 60/40 lead-tin solder. This specific ratio offers a good balance of melting point, flow characteristics, and strength, making it ideal for plumbing and other piping applications.

This alloy has a melting point that is low enough to facilitate easy workability while still providing a strong bond when cooled. Additionally, the composition allows for effective wetting of the copper surfaces, which is essential in soldering processes to ensure that the solder adheres properly and ensures a leak-proof joint. In contrast, other options contain higher percentages of tin or different alloying elements that may not be as commonly used for general soldering on copper tubes.

For instance, while some of the other choices include components like tin-antimony or tin-silver, these are less prevalent in typical plumbing applications due to their higher costs and specific applications in more specialized environments. Therefore, the choice that highlights the widely recognized ratio of lead-tin for general soldering purposes is the correct one.