Oxyfuel Fusion Welding

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Definition

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.

Oxyfuel fusion welding:

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. Heat2. Shielding3. 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

List the eight (8) ways that are used when oxyfuel fusion welding to control the heat of the weld.

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?

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Heat #1.1 - Tip Size

What determines the best tip size to use?

Welding Tip Size Conversion Chart (Mark@BikesmithDesign.com)

Wire Drill

Decimal Inch

Smiths AW1A

Little Torch Harris Victor

Meco Midget

97 0.0059 #2

85 0.0110 #3

80 0.0135 #00

76 0.0200 AW200 #4 0

75 0.0220 0 #000

74 0.0225 AW20

71 0.0260 AW201 1

70 0.0280 #00 1

69 0.0292 AW202 #5

67 0.0320 AW203

65 0.0350 2 0 2

63 0.0370 AW204 #6

60 0.0400 1

58 0.0420 3 3

57 0.0430 AW205

56 0.0465 AW206 #7 2 4

55 0.0520 4

54 0.0550 AW207

53 0.0595 5 3

52 0.0635 AW208 5

51 0.0670 6

49 0.0730 AW209 4

48 0.0760 7

45 0.0820 8

44 0.0860 AW210

43 0.0890 9 5

40 0.0980 10

36 0.1060 6

35 0.1100 13

Notice from the chart that tip sizes are not standardized.

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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 distance?

What is the critical distance when oxyfuel fusion welding called?

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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 Circular/spiral

2 C or crescent

3 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?

2 – Attach the correct tip

What determines the correct tip?

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How should it be attached?

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3 - Turn On System

What are the step for preparing an oxyacetylene system for use?

4 – Set Regulators

How do you set the regulators to the correct working pressure?

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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?

How far should you open the torch valve when starting the torch?

Why?

5 – Lighting Torch and Adjusting Flame – cont.

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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

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.

Five unacceptable fusion weld conditions:

Questions?