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					       Manufacturing Processes Lab I
                MET 1321
              Stick Welding


Manufacturing Processes Lab 1 (MET 1321)
Prof S. Nasseri
                  Welding Processes
                                              1.   Shielded Metal Arc Welding (Stick welding)
                                              2.   Gas Metal Arc Welding (MIG)
 ARC Welding                                  3.   Gas Tungsten Arc Welding (TIG)
    (AW)                                      4.   Flux Cored Arc Welding
                                              5.   Submerged Arc Welding
                                              6.   Plasma Arc Welding



Oxyfuel Welding
                                              Oxyacetylene Welding (OAW)
     OFW

Resistance Welding
        RW


   Manufacturing Processes Lab 1 (MET 1321)
   Prof S. Nasseri
Shielded Metal Arc Welding (SMAW), or
  Manual Metal Arc (MMA) welding or
            Stick Welding
                                           Shielded metal arc welding is performed by
                                           striking an arc ( electronic current AC or DC)
                                           between a coated-metal electrode and the base
                                           metal.

                                           Once the arc has been established (the weld is
                                           laid), the molten metal from the tip of the
                                           electrode flows together with the molten metal
                                           from the edges of the base metal to form a
                                           sound joint. This process is known as fusion.

                                           The coating from the electrode forms a covering
                                           over the weld deposit, shielding it from
                                           contamination; therefore the process is called
                                           shielded metal arc welding.


Manufacturing Processes Lab 1 (MET 1321)
Prof S. Nasseri
    Shielded Metal Arc Welding (SMAW), or
      Manual Metal Arc (MMA) welding or
                Stick Welding

Fact 1: The world's most popular welding process,

Fact 2: The process is used primarily to weld iron and steels
(including stainless steel) but aluminum, nickel and copper alloys can
also be welded with this method.

Fact 3: The main advantages of shielded metal arc welding are
that high-quality welds are made rapidly at a low cost.




    Manufacturing Processes Lab 1 (MET 1321)
    Prof S. Nasseri
                SMAW system setup
Stick welding equipment typically consists of a constant current welding power
supply and an electrode, with an electrode holder, a work clamp, and welding
cables (also known as welding leads) connecting the two.




      Manufacturing Processes Lab 1 (MET 1321)
      Prof S. Nasseri
                          Welding current
When electrical current moves through a
  wire, heat is generated by the resistance
  of the wire to the flow of electricity. The
  greater the current flow, the greater the
  heat generated.

The heat generated during the SMAW
  process comes from an arc that develops
  when electricity jumps across an air/gas
  gap between the end of an electrode and
  the base metal.

 The air/gas gap produces a high resistance to the flow of current.
 This resistance generates intense heat (6000◦ F to 10000◦ F or
 3300◦ C to 5500◦ C).
      Manufacturing Processes Lab 1 (MET 1321)
      Prof S. Nasseri
                      Welding current
Welding current can be Direct Current (DC) or Alternating Current (AC).

Direct current or Dc is an electrical current that flows in one direction
   only. There is no change in the direction of the current.
                                                www.pbs.org




  Manufacturing Processes Lab 1 (MET 1321)
  Prof S. Nasseri
                         Welding current
Alternate current or AC is an electrical current that has alternating
   positive and negative values. In the first (positive) half-cycle, the
   current flows in one direction; the current then reverses and for
   the second (negative) half-cycle flows in the opposite direction.
                                                 www.pbs.org




         +
                               -




     Manufacturing Processes Lab 1 (MET 1321)
     Prof S. Nasseri
    Transformer, Rectifier and Inverters
A transformer is an electrical device that changes voltage from one
   level to another. It produces AC current.
                                            V1                           V2
                                                 AC                 AC
                                                      Transformer

A rectifier is an electrical device contained within a transformer
welding machine that changes AC current into DC current.
                                                 AC                 DC
                                                       Rectifier

An inventer is an electrical device that changes DC current into AC current.

                                                 DC                 AC
                                                       Inverter



     Manufacturing Processes Lab 1 (MET 1321)
     Prof S. Nasseri
                                 AC and DC
AC current:
Allows a welder to easily maintain an arc during welding. Some
   features of AC current include low operating and maintenance
   costs, high overall electrical efficiency.
AC welding machines typically operate on single-phase primary
   power.

DC Current:
DC output has usually polarity switches with both positive and
negative terminals.
DC current output for SMAW may use single-phase or 3-phase
primary electrical power.
The most stable DC welding is provided by welding machines that
provide 3-phase transformers and full-wave rectifiers.


  Manufacturing Processes Lab 1 (MET 1321)
  Prof S. Nasseri
                                             AC/DC
AC/DC welding machines are commonly used for SMAW.

AC/DC current output is available on constant-current
  welding machines that operate using a single-phase or
  3-phase primary power source.
A welding machine in which a steady supply of current is produced over a wide range
                of welding voltages caused by changes in arc length.


AC/DC output contains a rectifier (not available in AC
  ones).

Rectified single-phase welding power is not as stable as
  rectified 3-phase DC welding power.

      Manufacturing Processes Lab 1 (MET 1321)
      Prof S. Nasseri
   Welding Machine Output




           AC                                      DC




                                           AC/DC

Manufacturing Processes Lab 1 (MET 1321)
Prof S. Nasseri
                                            Polarity
Polarity is the positive (+) or negative (-) state of an object.

Polarity determines the direction of current flow in a DC circuit.

Polarity is of no consequence in AC welding machines because current is
constantly changing directions.

   Direct Current Electrode Positive (DCEP)                        Cables should be switched
   Direct Current Electrode Negative (DCEN)




                                                                          - +
                                                                            + -



       Manufacturing Processes Lab 1 (MET 1321)
       Prof S. Nasseri
                                         Polarity
Polarity determines the location of heat concentration
  in a welding circuit.

With DCEN, more heat is located in the work piece.

With DCEP, more heat is directed to the electrode.

The type of welding to be performed and the electrode
  used determine the polarity. Electrodes are designed
  for use with a specific polarity.


    Manufacturing Processes Lab 1 (MET 1321)
    Prof S. Nasseri
                                          Voltage
Voltage: The force or pressure that causes current to
  flow in a circuit.
(In a water system, a pump provides the pressure to make the water flow,
   whereas in an electrical circuit a power supply produces the force or
   voltage that pushes the current through the wires).


Voltage is measured using a voltmeter.

Voltage has the most effect on the height and width of
  the weld deposit.




     Manufacturing Processes Lab 1 (MET 1321)
     Prof S. Nasseri
                                       Voltage
Voltage drop is the voltage decrease across a component due to
   resistance to the flow of current. When there is too great a
   drop, the welding machine cannot supply enough current for
   welding.


Open-circuit voltage is the voltage produced when the
machine is ON and no welding is being done (50 V to 100V).



 Arc Voltage (Working voltage) is the voltage present after an
 arc is struck and maintained (18V to 36 V).




  Manufacturing Processes Lab 1 (MET 1321)
  Prof S. Nasseri
           Avoid electrical shock!
Make certain that the electrode holder and all electrical connections
and cables are properly insulated.

Check to see that the welder is properly grounded.

Do not dip the electrode holder in water to cool it because this
practice may result in electrical shock.

Never weld in damp locations because of the shock hazard. Never
touch the electrical connection, bare wire, work, or a machine part
which may cause electrical shock.




    Manufacturing Processes Lab 1 (MET 1321)
    Prof S. Nasseri
             Safety Instructions
Protect welding cables. Keep the cables from coming
in contact with hot metal and sharp edges. When
welding, avoid wrapping electrode cables around
your body.

Handle hot metal with pliers or tongs. Submerge hot
metal completely in water to prevent steam burns.

Do not allow electrode to stick. If the electrode
sticks, cut off the switch, allow electrode to cool,
and then break it loose with your gloved hand.


 Manufacturing Processes Lab 1 (MET 1321)
 Prof S. Nasseri
            Safety Instructions




Manufacturing Processes Lab 1 (MET 1321)
Prof S. Nasseri
               Safety Instructions
Never look at a welding arc without
wearing a welding helmet.

Safety glasses should be worn
under face shields, hoods, and
helmets and at all times when
working in the shop.

Use both hands. To reduce fatigue,
use both hands for welding.


   Manufacturing Processes Lab 1 (MET 1321)
   Prof S. Nasseri
                            Test yourself!
Which one is Direct Current Electrode Positive (DCEP)?




                                                - +




                                                         This is DCEP,
                                                         Because the
                                               + -       electrode is
                                                         connected to the
                                                         positive terminal.


    Manufacturing Processes Lab 1 (MET 1321)
    Prof S. Nasseri
                             Test yourself!
Place the name of machines in the empty boxes. Choose from: Rectifier,
   Inverter, and Transformer.

                 V1
                                                  V2
                                   Transformer




                                      Rectifier




                                      Inverter



     Manufacturing Processes Lab 1 (MET 1321)
     Prof S. Nasseri
                             Test yourself!
     With DCEP, more heat is directed to the … .
     a) Electrode
     b) Work piece

      Is this sentence true or false:
      Handle hot metal with pliers or tongs. Submerge the
Hot
        electrode completely in water to prevent steam
metal   burns.

     True
     False

     Manufacturing Processes Lab 1 (MET 1321)
     Prof S. Nasseri

				
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