Yes, pieces of coat hanger wire can be soldered together. Coat hanger wire is typically made of steel, which is a ferrous metal. Ferrous metals are metals that contain iron, and they are generally considered to be solderable. However, there are a few things to keep in mind when soldering coat hanger wire.

First, the surface of the wire must be clean and free of any dirt, oil, or grease. This can be done by wiping the wire with a solvent such as isopropyl alcohol.

Second, the wire must be heated to a high enough temperature for the solder to melt and flow. This can be done using a soldering iron or a butane torch.

Third, the solder must be applied to the wire in a way that allows it to flow evenly and smoothly. This can be done by using a flux to help the solder spread, and by applying the solder to the wire in a continuous motion.

Once the solder has cooled and solidified, the pieces of coat hanger wire will be permanently joined together.