Hobbies And Interests
Brazing
Brazing is a process used for many types of metals in heavy industry. Its purpose is to fuse two metals together. The fusing metal -- also known as "filler" -- has a higher melting point than the material being fused. Manufacturers generally use gas, such as oxygen propane or oxygen MAPP, to in torches to heat the filler, apply it to the metal and fuse two pieces together.
Brazing Stainless Steel
When brazing stainless steel, the filler of choice is silver mixed with copper and tin, since these metals have a higher melting point than stainless steel. However, this is not to be confused with silver soldering, which is a different process. First, manufacturers apply a chemical mixture called flux to the stainless steel. Flux helps transfer heat and prevent oxidation. In the case of stainless steel, the flux must not contain cadmium. Next, you heat the stainless steel and filler. Once the steel and filler reach their melting point, they flow together in liquid form to fuse the stainless steel pieces together.
Silver Soldering
Silver is the base metal used in silver soldering, with copper, tin and zinc mixed in. The only real difference between brazing and silver soldering is the melting point of the filler metal. With brazing, the filler is heated above 840 degrees, whereas soldering heats the silver filler to about 430 degrees.
Preferred Method
Although brazing and silver soldering are effective methods to fuse stainless steel together, brazing is preferable. In some cases, such as construction, steel needs to support a great deal of weight or be outside, exposed to the elements. According to L.D. Connell of Johnson Matthey Metals, brazing creates a low "bond strength." This means that silver soldering does not fuse stainless steel together strongly. Brazing, on the other hand, creates a stronger fusion to handle the physical demands expected of stainless steel.