difference in their expansion rates. It also provides a cushion between the hard carbide tip and the hard steel, which softens impact and prevents tip loss and damage—much as a vehicle's suspension helps prevent damage to the tires and the vehicle. Finally, the braze alloy joins the other two materials to create a composite structure, much as layers of wood and glue create plywood. The standard for braze joint strength in many industries is a joint that is stronger than either base material, so that when under stress, one or other of the base materials fails before the joint. Silver brazing may cause defects in certain alloys, e.g. stress-induced inter-granular cracking in copper-nickel. One special silver brazing method is called or . It has been developed especially for connecting cables to railway track or for cathodic protection installations. The method uses a silver- and flux-containing brazing pin, which is melted in the eye of a cable lug. The equipment is normally powered from batteries. Braze welding Braze welding is the use of a bronze or brass filler rod coated with flux to join steel workpieces. The equipment needed for braze welding is basically identical to the equipment used in brazing. Since braze welding usually requires more heat than brazing, acetylene or methylacetylene-propadiene gas (MAPP gas) fuel is commonly used. The name comes from the fact that no capillary action is used. Braze welding has many advantages over fusion welding. It allows the joining of dissimilar metals, minimization of heat distortion, and can reduce the need for extensive pre-heating. Additionally, since the metals joined are not melted in the process, the components retain their original shape; edges and contours are not eroded or changed by the formation of a fillet. Another effect of braze welding is the elimination of stored-up stresses that are often present in fusion welding. This is extremely important in the repair of large castings. The disadvantages are the loss of strength when subjected to high temperatures and the inability to withstand high stresses. Carbide, cermet and ceramic tips are plated and then joined to steel to make tipped band saws. The plating acts as a braze alloy. Cast iron "welding" The "welding" of cast iron is usually a brazing operation, with a filler rod made chiefly of nickel being used although true welding with cast iron rods is also available. Ductile cast iron pipe may be also