Non-mechanical joints 2 - bryan garcia godinez

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Non-mechanical joints 2
Bryan Eduardo García Godínez 14310119 
Specialized welding techniques
Resistance welding involves passing an electric current through metal components that are touching. This heats the metal and welds it. The technique can be used for spot welding - welding a number of small points between the surfaces of the components. It can also be used for seam welding, to make long, narrow welds. Ultrasonic welding uses high-frequency acoustic vibrations (sound vibrations) to make the touching surfaces of two components vibrate. This generates friction, heating them and fusing them. The technique is often used to weld plastics
Brazing and soldering
In brazing, brass- an alloy of copper (Cu) and zinc (Zn)- is melted using an oxyfuel torch, and added as filler to form the joint. Unlike welding, the base metal of the components is not melted, so the components are not fused. Brazed joints are therefore not as strong as welded joints. 
For some pipe joints and for electrical connections, soldering is often used. Solder is a metal filler which melts at quite a low temperature. Like brazing, soldering forms joints without melting the base metal. Soldered joints are therefore weaker than welds, and also generally weaker than brazed joints. In soft soldering, an alloy- of tin (Sn) and lead (Ph), or of tin and copper- is melted using an electrically heated rod called a soldering iron. In hard soldering, a solder containing copper and silver (Ag) produces slightly stronger joints.
Adhesives
Adhesive - called glue in everyday language -can be used to bond (permanently join) components together. Its purpose is to adhere to the surfaces being joined, to create a bond between them. Most adhesives are liquids, which can be applied to (put on) the surfaces that need to be glued together. Adhesives can create adhesion between surfaces in two main ways. One is by allowing wet adhesive to be absorbed by the components. After drying and hardening, this forms a mechanical bond, as adhesive is anchored into each component's substrate (the material below the surface). Adhesion may also be created by a chemical bond, from a chemical reaction between the adhesive and the materials.
Contact adhesives must be applied to both components, then left to dry for a time before the surfaces are brought together. A bond then occurs when the surfaces touch.