O-F Running a Bead

8/13/2019 O-F Running a Bead

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

LESSON: Oxy-Acetylene Welding (OAW)

RUNNING A BEAD WITH AND WITHOUT FILLER ROD

Standard B7.4

Know how to fusion-weld mild steel with and without filler rod by using the oxy-fuel system


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The Welding Flame

A chief advantage of theoxy-acetylene flame is itshigh operatingtemperatures.

This oxy-acetylene flamecan easily melt allcommon metals.

The proper mixture of

oxygen and acetyleneburns at 5,589 degreesFahrenheit, which makesit the hottest oxy-fuel gasflame.


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Types of Flames

Three types of flames can be

produced with the oxy-

acetylene torch: carburizing,

neutral, and oxidizing.

The operator must be able torecognize each type of flame

by its size, shape, and color.

The operator must also master

the adjustment of the oxygen

and acetylene hand valves on

the welding torch to produce

the desired flame.


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Carburizing Flame Flame contains more

acetylene than oxygen.

This flame is easy to recognizeby the outer flame, which has aslim bluish taper with anorange tip.

Inside this outer flame is ashorter, blue flame called theacetylene feather.

Flame has a lower temperature

than the neutral flame. Flames are sometimes used

for silver brazing, brazewelding, and soldering.
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Neutral Flame

The neutral flame is produced bya proper balance of oxygen and

acetylene.

It is approximately 5,589 degrees

Fahrenheit and is the most widely

used of the three types of flames.

As the flame is adjusted from a

carburizing flame to neutral flame

by adding more oxygen, the light

blue acetylene feather disappears.

At the same time, the brilliant

inner cone becomes slightly

shorter and more sharply defined.
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Neutral Flame - Cont.

When a neutral flame isdirected upon a steel surface,the metal melts slowly.

The molten metal does notboil and few sparks appear.

The neutral flame protectsthe molten steel fromoxidation, and the weld joint

is not burned.

Extremely strong welds areproduced from this flame.


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Oxidizing Flame

Flame contains moreoxygen than acetylene.

Is similar to the shape of the

neutral flame, however the

inner cone of the oxidizingflame is more pointed,

shorter, and purple.

The flame can also be

distinguished from theneutral flame by a loud

hissing sound caused by

the excess rush of oxygen.


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Oxidizing Flame Cont.

This flame has very littlepractical use in welding.

Its temperature may reach6,300 degrees Fahrenheit,but the oxides that form whenthe excess oxygen combineswith the molten metal causeproblems with the weld.

Such problems includebrittleness, weakness, andhardening around the weld.


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Characteristics of the

Three Welding Flames


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Holding the Torch

A torch may be held in either one of twoways, depending on which is the morecomfortable for you.

When welding light-gauge metal (under 14gauge), most operators prefer to grasp the

handle of the torch with the hose over theoutside of the wrist, in the same manner apencil ordinarily is held.

In the other grip, the torch is held like ahammer, with the fingers lightly curled

underneath.

In either case the torch should balanceeasily in the hand to avoid fatigue.

Pencil Grip Method

Hammer Grip Method


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Pushing a Puddle Hold the torch so the flame points in the

direction you are going to weld and at

an angle of about 45 degrees with thecompleted part of the weld.

If you are right handed, start the weld atthe right edge of the metal and bring theinner cone of the neutral flame to within

1/8 of the surface of the plate.

The left-handed person reverses thisdirection.

Hold the torch still until a pool of moltenmetal forms.

Then move (push) the puddle acrossthe plate.


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Pushing a Puddle Cont.

As the puddle travels forward, rotate

the torch to form a series ofoverlapping ovals or circles (forming a

bead)

Do not move the torch ahead of the

puddle, but slowly work forward, givingthe heat a chance to melt the metal.

If the flame is moved forward too

rapidly, the heat fails to penetrate far

enough and the metal does not melt

properly.

If the torch is kept in one spot too long,

the flame will burn a hole through the

metal.


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Laying a bead with filler rod

On some types of joints (outside cornerwelds) it is possible to weld the two piecesof metal without adding metal from a fillerrod.

The use of a filler rod requires coordinationof the two hands.

One hand must manipulate the torch to carrya puddle across the plate, while the otherhand must add the correct amount of fillerrod.

In most instances the use of a filler rod is

advisable because it builds up the weld,thereby adding strength to the joint.

The strength of a weld depends largely onthe skill with which the rod is blended, orinterfused, with the edges of the base metal.


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Selecting the filler rod

Filler rods come in a variety of sizesranging from 1/16 to 3/8 indiameter.

The size of rod to use will depend

largely upon the thickness of themetal being welded.

The general rule is to use a rod witha diameter equal to the thickness ofthe base metal.

In other words, if a 1/16 metal isbeing welded, a 1/16 diameter rodshould be used.


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Laying a bead with filler rod Cont.

The torch is held at an angle ofapproximately 45 degrees to the basemetal, hold the rod at approximately thesame angle as the torch but slant itaway from the torch.

Move the torch tip over the starting edgeand rotate the flame near the metal in acircular or semicircular motion until thebase metal melts into a small puddle.

Once a small pool of the base metal is

established, dip the tip of the rod in themolten pool.

ALWAYS DIP THE ROD IN THECENTER OF THE MOLTEN POOL.


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The molten puddle will melt the rodand add to the puddle, as the rodmelts in the pool, advance the torchforward.

Concentrate the flame on the base

metal and not on the rod.

Do not hold the rod above the pool. Ifyou do this the molten metal will fallthrough the air to the puddle.

When this happens it combines withthe oxygen in the air and part of itburns up, causing a weak, porousweld.


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Common Difficulties with Laying a

Bead with Filler Rod .

The beginner often experiences difficulty in

holding the welding rod steady which can

cause the rod to stick to the base metal

Instead of inserting the rod in the middle of

the puddle where the heat is sufficient tomelt it readily, a beginner generally inserts

the rod near the edge of the pool where the

temperature is lower. The heat at the edge is

not enough to melt the rod and the rod will

likely stick to the base metal.

If the rod sticks to the base metal, do not tryto jerk it loose.

Simply place the flame directly over the tip ofthe rod and the rod will be freedimmediately.


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The circular or semicircular

motion should be advanced

approximately 1/16 per

motion until the end of the

joint is reached.

Since the angle of the tip

flame is preheating the

metals ahead of the weld, the

last of weld is critical.

Slightly raise the welding tip

and increase the addition of

filler rod to insure a full

smooth weld.


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Bead with filler rod

Bead with Filler Rod

Push a Puddle (No filler rod)

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O-F Running a Bead