Brazing

Brazing is a metal-joining process. Two or more metal items are joined together by melting and flowing a filler metal into the joint. The filler metal has a lower melting point than the adjoining metal.
Brazing differs from welding because it does not melt the work pieces. Brazing differs from soldering because it uses a higher temperature and more closely fitted parts than soldering. 
During the brazing process, the filler metal flows into the gap between close-fitting parts by capillary action. 
The filler metal is brought slightly above its melting temperature. while protected by a suitable atmosphere, usually a flux. It then flows over the base metal and joins the work pieces together. A big advantage of brazing is it can join the same or different metals with considerable strength.