UNIT: Oxy-Acetylene; Welding, Brazing, Cutting and Heating - PowerPoint PPT Presentation

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UNIT: Oxy-Acetylene; Welding, Brazing, Cutting and Heating

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Brazing Sheet Metal Select the proper welding nozzle, brass rod size and flux. Follow safety and operating procedures for setting up cylinders and regulators. – PowerPoint PPT presentation

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Title: UNIT: Oxy-Acetylene; Welding, Brazing, Cutting and Heating


1
UNIT Oxy-Acetylene Welding, Brazing, Cutting
and Heating
  • Lesson Oxy-Acetylene Brazing
  • Standard B7.5 - Know basic repair skills using a
    variety of techniques, such as brazing or hard
    surfacing

2
Brazing
  • Is classified by the American Welding Society
    (AWS) as a liquid solid phase bonding process.
  • Liquid- Filler metal is melted (Brass Rod).
  • Solid- Base metals are not melted (heated only).
  • Phase- The temperature at which bonding takes
    place between the solid base metal and liquid
    filler metal
  • Bonding- To secure or hold together.

3
Brazing
  • A form of welding characterized by the use of
    base metal temperatures above 700 degrees but
    below the melting point of the base metal.
  • Brazing Temperature- Occurs around 840 degrees
  • Most metals can be joined by brazing but the
    proper filler rod and flux must be used.
  • Flux is required to prepare the metals for
    joining and the filler rod bonds the base metals
    together.
  • CAUTION All brazing processes should be
    preformed in a well-ventilated area. Toxic fumes
    may be generated by the brazing process.

4
Advantages of Brazing
  1. Low Temperature- since the base metal does not
    have to melt, a low temperature heat source can
    be used.
  2. May be permanently or temporarily joined- since
    the base metal is not damaged, parts may be
    disassembled at a later time by simply reapplying
    heat.

5
Advantages of Brazing Cont.
  1. Dissimilar metals can be joined- brazing can join
    dissimilar metals, such as copper to steel,
    aluminum to brass, and cast iron to stainless
    steel.
  2. Metals of various thickness can be joined- very
    thin metal can be joined to thick metal without
    burning, warping, and overheating them.

6
Advantages of Brazing Cont.
  • 5. Easy realignment- parts can easily be
    realigned, through reheating the joint and
    repositioning the part.

7
FLUXES INVOLVED IN BRAZING Three major functions
  • To remove any oxides that form as a result of
    heating the metal.
  • To promote wetting.
  • Aid in capillary action.
  • Wetting is the phenomenon whereby a liquid filler
    metal or flux spreads and adheres in a thin,
    continuous layer on a solid base metal.
  • Capillary action is the force that pulls filler
    metal (brass) through the joint.

8
Preparing the Metals to be Brazed
  • All paint, rust, grease, dirt must be removed
    from the surface area prior to beginning to
    braze.
  • The successful brazing operation depends on close
    joint tolerances, meaning no major gaps.

9
Brazing Sheet Metal
  • The following brazing techniques can be utilized
    in all brazing applications. This example uses
    strips of 14 gauge sheet steel in the Flat T
    position.

10
Brazing Sheet Metal
  • Select the proper welding nozzle, brass rod size
    and flux.
  • Follow safety and operating procedures for
    setting up cylinders and regulators.
  • Acetylene 5 psi
  • Oxygen 5 8 psi.

11
Brazing Sheet Metal Cont.
  • 3. Obtain a neutral to slightly oxidizing flame
    on torch.
  • 4. Preheat metal only to a dull red color. If
    the base metal is heated to a higher temperature
    a porous deposit will result.

12
Brazing Sheet Metal Cont.
  • Touch fluxed rod to heated portion and allow some
    flux to melt and react with the base metal.
  • The melted flux reacts to chemically clean the
    base metal.

13
Brazing Sheet Metal Cont.
  • 6. Melt off small amounts of fluxed rod and if it
    flows freely and tins (adheres to the heated
    base metal), the correct temperature has been
    reached. Maintain this temperature by continually
    moving the flame over the metal.

14
Brazing Sheet Metal Cont.
  • 7. Continue to dip rod into the molten puddle and
    add sufficient amount of brass to the base metal
    to build up the bead.

15
Brazing Sheet Metal Cont.
  1. Continue to tin and build a bead until the
    desired section has been covered.
  2. With a chipping hammer, remove the flux covering
    (slag) on the bead.

16
Brazing Sheet Metal
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