Transcript 8_OxyfuelWelding

Oxyfuel Fusion Welding
Definition
Oxyfuel fusion welding:
A welding process that uses an oxyfuel
flame to melt the steel piece(s) forming a
pool (puddle) that when cooled, solidifies
to form the joint.
How popular is the process today?
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Preparing To Weld
What safety preparations should be completed before attempting
an oxyacetylene steel fusion weld?
How does oxyfuel welding meet the three requirements of
fusion welding
1. Heat
2. Shielding
3. Filler material
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Five (5) Factors Which Control The Quality of
Oxyfuel Fusion Welds.
1. Heat
2. Filler rod
3. Torch position
4. Travel Speed
5. Manipulation
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1. Heat
Heat is provided by a flame utilizing oxygen and acetylene gas.
Based on the laws of physics, what two methods can be used to
control the flow of a gas?
List the eight (8) ways that are used when oxyfuel fusion welding to
control the heat of the weld.
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Welding Tip Size Conversion Chart
Heat #1.1 - Tip Size
(Mark @Bik esmithDes ign.c om)
Wire
Drill
Decimal
Inc h
97
85
80
76
75
74
71
70
69
67
65
63
60
58
57
56
55
54
53
52
51
49
48
45
44
43
40
36
35
0.0059
0.0110
0.0135
0.0200
0.0220
0.0225
0.0260
0.0280
0.0292
0.0320
0.0350
0.0370
0.0400
0.0420
0.0430
0.0465
0.0520
0.0550
0.0595
0.0635
0.0670
0.0730
0.0760
0.0820
0.0860
0.0890
0.0980
0.1060
0.1100
Smit hs
AW1A
Litt le
Torch
Harris
Vic tor
Meco
Midget
#2
#3
AW200
#00
0
#4
0
AW20
AW201
AW202
AW203
1
#00
1
0
2
#5
2
AW204
#000
What determines the
best tip size to use?
#6
1
3
AW205
AW206
#7
3
2
4
4
AW207
5
3
AW208
Notice from the chart
that tip sizes are not
standardized.
5
6
AW209
4
7
8
AW210
9
10
5
6
6
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Heat #1.2 - Fuel gas working pressure
What determine the ideal working pressures?
What is a possible problem with excessive
working pressure?
What is a possible problem with insufficient
working pressure?
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Heat #1.3 - Torch settings
Torch setting refers to the position of the oxygen and acetylene
torch valves.
Which one of the torch valves controls the amount of heat?
Which one of the torch valves controls the type of flame?
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Oxyfuel Welding Tips
On the system that we use what is normally called a welding tip is
actually a welding tip and a mixing chamber.
The welding tip can be purchased separately—reduces cost.
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Using Tip Cleaner
•Start with the smallest size that will
enter the orifice without excessive
force and work up to orifice size.
•Be careful, a broken tip cleaner
usually means a destroyed tip.
•Clean the face of the tip with the
included file.
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Heat #1.4 - Torch Angles
Two welding angles are important in
OxyFuel welding.
– Work
– Travel
Will increasing the travel angle change
the heat at the weld? Explain!
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Heat # 1.5 - Travel Speed
Why does changing the speed of travel change the temperature of
the weld?
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Heat #1.6 - Welding Rod Manipulation
• Manipulating the torch produces a wider bead.
• The heat of the flame is applied to a larger area--lower weld
temperature.
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Heat #1.7 - Size of welding rod
• Standard rods are 36 inches long and are available in a range of
sizes from 1/16 to 1/4 inch diameter.
• A slightly larger or smaller rod than what is recommended can
be used to manipulate the heat of the weld.
– Explain!
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Heat #1.8 - Distance from the torch to the metal
The distance between the torch and the metal
influences the temperature of the weld in two ways.
1. As the distance is increased the heat is spread over
a wider area. This reduces the temperature of the
weld.
2.
The temperature of the
flame is not uniform.
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Heat #1.8 - cont.
What is the critical distance when oxyfuel fusion welding called?
What is the distance?
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2. Filler Rod
What are the desirable characteristics of the filler rod?
How will use a rod larger or smaller than
recommended affect the welding process?
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3. Torch Position
Critical torch positions are angle and height.
Explain the effect of having incorrect angle and/or height.
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4. Welding Speed
Travel speed should be adjusted
so that as the edges of the
puddle melt they form a
collapsed key hole at the front
edge of the puddle each time the
rod is dipped into the weld
puddle.
What factors determine the ideal
speed of travel?
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5. Manipulation
Three common manipulation patterns:
1
2
3
Circular/spiral
C or crescent
Dipping
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Oxyfuel Welding Process
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Seven (7) steps to Oxyfuel Welding
1. Prepare metal
2. Attach the correct welding tip
3. Turn on system
4. Set regulators to correct working pressure
5. Light the torch and adjust the flame
6. Form a puddle
7. Manipulate torch and filler rod (if used) to
complete the weld
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1 - Prepare Metal
You need to complete an
oxyacetylene fusion weld
on this piece of sheet
metal.
Should anything be done to
the metal before you start?
If so what?
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2 – Attach the correct tip
What determines the correct tip?
How should it be attached?
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3 - Turn On System
What are the step for preparing an oxyacetylene system for use?
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4 – Set Regulators
How do you set the regulators to the correct working pressure?
What do you do if you set the pressure to high?
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5 - Lighting Torch & Adjusting Flame
Should the acetylene or the oxygen torch valve be opened
first? Why?
How far should you open the torch valve when starting the
torch?
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5 – Lighting Torch and Adjusting Flame – cont.
Fusion welding requires a neutral
flame.
Describe a neutral flame.
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6 – Form Puddle
Hold torch stationary, or 1/8 circle, at the beginning
of the weld until the molten puddle is formed.
Note: The puddle should form in 3 to 4 seconds.
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7 – Manipulate Torch and Rod
Requirements;
1 The torch must be moved to the
back of the puddle before the rod
is dipped in.
2 The rod must be dipped into the
molten puddle and withdrawn
when the desired amount is
melted off.
3 The rod must stay within the outer
flame.
4 The rod a torch advance 1/8 –
3/16 inch each time the rod is
withdrawn.
Note: To produce a good weld the welder must
practice until they can maintain a constant rhythm.
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Joints & Spacing
Use the correct joint preparation.
Describe each one of
these joints.
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Acceptable Welds
• An acceptable weld has the
designed strength and meets
appearance standards.
• Strength
– Bending
– Tensile
• Appearance evaluation
1. Uniformity
2. Appropriate weld size
3. Penetration
4. Reinforcement
5. Undercutting
6. Starved joint
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Unacceptable Welds
Five unacceptable fusion weld conditions:
1. The weld doesn’t
completely fill the joint.
2. Surface reinforcement
is greater than 1/8
inch.
3. Undercutting is greater
than 1/32 inch.
4. The weld breaks
during a bend test.
5. The weld metal was
not fused to the base
metal.
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Questions?