Welding Workshop Part 2-Workshop Practice-Lecture Slides, Slides of Mechanical Engineering

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Furnace brazing

• Furnace brazing is a semi-automatic

process used widely in industrial brazingoperations due to its adaptability to massproduction and use of unskilled labor.

Furnace Brazing

Braze welding

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In another similar usage,

brazing

is the use of a

bronze or brass filler rod coated with fluxtogether with an oxyacetylene torch to joinpieces of steel.

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Braze welding takes place at the meltingtemperature of the filler (e.g., 870 °C to 980 °Cor 1600 °F to 1800 °F for bronze alloys) which isoften considerably lower than the melting pointof the base material (e.g., 1600 °C (2900 °F) formild steel).

Cast iron "welding"

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The "welding" of cast iron is usually a brazingoperation, with a filler rod made chiefly of nickelbeing used although true welding with cast ironrods is also available. Ductile cast iron pipe maybe also "cadwelded," a process which connectsjoints by means of a small copper wire fused intothe iron when previously ground down to thebare metal. The purpose behind this operation isto use electricity for keeping underground pipeswarm in cold climates.

Dip brazing

• Dip brazing is especially suited for brazing

aluminum because air is excluded, thuspreventing the formation of oxides. Theparts to be joined are fixtured and thebrazing compound applied to the matingsurfaces, typically in slurry form. Then theassemblies are dipped into a bath ofmolten salt (typically NaCl, KCl and othercompounds) which functions both as heattransfer medium and flux.

Advantages of Brazing

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Brazing has many advantages over other metal-joiningtechniques, such as welding. Since brazing does notmelt the base metal of the joint, it allows much tightercontrol over tolerances and produces a clean join withoutthe need for secondary finishing. Additionally, dissimilarmetals and non-metals (i.e. metalized ceramics) can bebrazed. In general, brazing also produces less thermaldistortion than welding due to the uniform heating of abrazed piece. Complex and multi-part assemblies can bebrazed cost-effectively. Another advantage is that thebrazing can be coated or clad for protective purposes.Finally, brazing is easily adapted to mass production andit is easy to automate because the individual processparameters are less sensitive to variation.

AWS & CWI

• AWS: American Welding Society• CWI: Certified Welding Inspector

Welding

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Welding

is a fabrication process that joins

materials, usually metals orthermoplastics, by causing coalescence.This is often done by melting theworkpieces and adding a filler material toform a pool of molten material (the

weld

pool

) that cools to become a strong joint,

with pressure sometimes used inconjunction with heat, or by itself, toproduce the weld.

Weld Bead

Weld Bead

Weld

• A fusion weld is a casting surrounding by a

heat treatment.

• A localized coalescence of metals and

non-metals by heating the materials tosuitable temperatures, with or without theapplication of pressure, or by theapplication of pressure alone and with orwithout the use of filler material.

Butt welds

• Butt welds are welds where two pieces of

metal are joined at surfaces that are at 90degree angles to the surface of at leastone of the other pieces.

Butt Joints

Bevel Butt Joints

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Single-bevel butt welds

are welds where one

piece in the joint is beveled and the othersurface is perpendicular to the plane of thesurface. These types of joints are used whereadequate penetration cannot be achieved with asquare-groove and the metals are to be weldedin the horizontal position (HBW).

Double-bevel

butt welds

are common in arc and gas welding

processes. In this type both sides of one of theedges in the joint are beveled.