How to weld copper pipe to the elbow?

A metal like copper could be attached using several processes. For instance, soldering, brazing, and welding are key joining processes. Choosing the method of connection depends on the type of alloy used, the strength requirements, as well as the application.

Pure copper is pliable and forming components from this metal is effortless. In comparison to other alloys (including Cu alloys), the pure metal is not hardenable like regular steel-grades because there is no change in their phase. The application of heat melts or softens this metal. As a result, unalloyed Cu components lose their strength, especially in HAZ or heat affected zones. It has a high rate of thermal conductivity. Therefore, forging any joint requires a pre-heat treatment, even if the thickness is moderate at best. Furthermore, the distortion of the component could be a problem due to a higher coefficient of thermal expansion. The issue occurs expressly on the closure of gaps during welding.

Welding work

Welding - This process is apt for systems that have a thicker wall thickness, and when the material to be attached is the same. The temperature for this process is the highest amongst all the three techniques. Typically methods such as gas tungsten arc, Electric resistance, Oxy-fuel, submerged arc, or shielded metal arc aid to weld this metal.

Brazing - Similar to soldering, the difference in this mechanical process is the temperature of the melted filler metal, for this operation is higher than a solder. Though HVAC systems require a secure connection, it is ok to either braze or solder the tube.

In instances where fittings, like the elbow, are of another alloy or metal grade, a solder performs the task adequately. An elbow is a variety of fitting that influences change in the direction of flow. Commonly elbows influence the directional flow at angles of 22.5, 45, and 90 degrees. Generally, fittings like the elbow are a part of a piping system via internal threads, as both the tube and fitting are products that have internal threads. However, unlike other materials, a pipe in a copper-based HVAC system tends to be soft and weak to form a threaded connection. Hence, the elbows are attached to an arrangement by exercising a sweat connection. In such an organization, the elbow fitting has a bore constructed a little larger than the tube. A slight enlargement of the fitting makes it easier to slip on to the pipe. Once the elbow fitting slips over it, the nexus is soldered.

Soldering - The term sweat connection obtains its name from the process it undergoes. The attachment of the fitting or the elbow is by the heat received when exposed to a propane torch. The heat treatment causes the metals to melt and fuse. Therefore a leak-free and tightly integrated joint is obtained. Using this method is an efficient way to join thinner cross-sections even if both the fitting and pipe vary.

Following a strict method ensures good quality welds between the fitting and the pipe. First, the welder needs to polish and smoothen the tube with the use of an emery cloth or a woven abrasive pad. Any synthetic material abrasive woven pad can clean copper. Once the surface is free from blemishes, using a flux brush, the application of a layer of flux is the next step. After the removal of excess flux, the torch flame directly heats the fitting. The flux in the fitting acts as a guide by bubbling, which in turn causes steam. Once the solder on the pipe melts, it is adequately hot. Different areas of the fitting joints could make an efficient soldered connection. Once the joint is sufficiently cold, the piping system can undergo a test. A leak in the system would require reheating up to the point when the solder melts and joint disassembly. Following the joint disassembly, the welder will have to clean, flux, heat as well as solder them again.