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WELDING (SOLID STATE WELDING (Coalescence of part surfaces achieved by…

- - - - Component to be joined are heated to hot working temperature range & forged together by hammering
    - - Apply high pressure between clean contacting surface
        at room temperature
      - Application
        
        Making electrical connections
    - - Pressure sufficient to cause coalescene applied by means of rolls either with or without external heat
      - Application
        
        Bimetallic strips for measuring temperature
        
        "Sandwich" coins for U.S mint
    - - Uses heat & pressure, in controlled temperature. with sufficient time for diffusion
      - Application
        
        Joining of high strength & refractory metals in aerospace & nuclear industries
        
        Can be used to join either similar or dissimilar metals
      - Limitation
        
        Time required for diffusion can range from seconds to hours
    - - Method
        
        Rotating part, no contact
        
        Parts brought into contact to generate friction heat
        
        Rotation stopped & axial pressure applied
        
        Weld created
      - Types
        
        Continuous-drive
        
        Inertia
      - Coalescence achieved by frictional heat combined with pressure
      - Limitation
        
        Flash must usually be removed
        
        At least one of part must be rotational
- - - - Coalescence of metal achieved by heat from electronic arc between electrode & work
    - - Use a combination of heat & pressure to accomplish coalescence
      - Advantage
        
        High production rates possible
        
        Good repeatability & reliability
        
        No filter metal required
      - Disadvantage
        
        High initial equipment cost
        
        Skilled operators are required
        
        Bigger job thickness cannot be welded
      - Application
        
        Making tubes & metal furniture
        
        Welding aircraft & automobile parts
    - - Uses rotating wheel electrodes to produce a series of overlapping spot welds along lap joint
      - Application
        
        Gasoline tank
        
        Automobile mufflers
    - - Alternative Fuel Gases
        
        Hydrogen
        
        Acetylene
        
        Gasoline
      - Welding operation that burn various fuels mixed with oxygen
    - - Method
        
        Crucible tapped, superheated metal flows into mold
        
        Metal solidifies to produce weld joint
        
        Thermal ignited
      - Application
        
        Joining of railroad rails
        
        Repair of cracks in large steel castings & forgings
      - Heat for coalescene produced by superheated molten metal from chemical reaction of thermite