1. Oxyacetylene Welding
By Matt Scott
4/15/2017

2. Introduction
OAW is a welding process that heats the base metal with a controlled mixture of acetylene and oxygen gas. The heat from the torch allows for the melting and mixing of the base metal and filler metal to form a solid weld.
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3. 8 Steps to Making a Quality Weld
Safety Check
Select a tip based on metal thickness
Adjust gas pressures
Ensure the tip is clean
Set torch to neutral flame
Get Comfortable
Maintain a consistent Coupling Distance
Oscillate torch to ensure fusion.
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4. Step 1 – Safety At a Glance SAFETY FIRST!!!!!!!!!
Stop – smell, look and listen before using!
Did you ensure the cylinders where chained up and hoses where in good shape?
Did you scan the whole system to see if there was anything odd?
SAFETY FIRST!!!!!!!!!
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5. Step 2 and 3 – TIP Selection & Setting the Gas Pressure
Metal Thickness
Tip Size
Drill Size
Oxygen Pressure (PSIG)
Acetylene Pressure (PSIG)
Acetylene Consumption (SCFH)
Min.
Max.
Up to 1/32”
000
75 (.022) 3 5 1 2
1/16”-3/64” 00
70 (.022)
1 ½
1/32”-5/64”
65 (.035) 4
3/64”-3/32”
60 (.040) 6
1/16”-1/8”
56 (.046) 10
1/8”-3/16”
53 (.060) 7 8 18
3/16”-1/4”
49 (.073) 25
¼”-1/2”
43 (.089) 12 15 35
½”-3/4”
36 (.106) 14 9 45
¾”-1 ¼”
30 (.128) 16 30 60
1 ¼”-2”
29 (.136) 19 75
2 ½”-3”
27 (.144) 24 50
100
3 ½”-4”
25 (.149) 28 80
160
Victor Cutting Equipment
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6. Step 4 – Ensure the Tip is Clean
Indicators of a clean tip are:
Preheat flame is sharp and ¼” in length.
Secondary flame does not splinter
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7. Step 5 - Set torch to Neutral Flame
A neutral flame is when you have the same ratio of acetylene and oxygen burning
Most efficient welding flame setting
Flame temperature is 5800 Fahrenheit
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8. Step 6 – Get Comfortable
Steady yourself when welding
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9. Mild Steel Welds
Oxyacetylene welding is limited to thin metal sections or when portability is important
Today almost exclusively used on thin metal
An electric arc welding processes is usually used for welding thicker metal
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10. Mild Steel Welds Easiest metal to gas weld
Welds with 100% integrity possible
Secondary flame shields the molten weld pool from the air
Atmospheric oxygen combines with carbon monoxide to produce carbon dioxide
Carbon dioxide forces surrounding atmosphere away from the weld
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11. Factors Affecting the Weld
The torch tip size controls the weld bead width, penetration, and speed
Torch angle and the angle between the inner cone and the metal effect:
Speed of melting
Size of the molten weld pool
Welding rod size and torch manipulation control the weld bead characteristics
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12. Step 7&8 Coupling Distance and Torch Manipulation
“Flashing” the flame off the metal will allow the molten weld pool to cool and reduce in size.
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16. If the buildup on both welds is removed, weld (B) would be stronger
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17. Characteristics of the Weld
Molten weld pool must be protected by the secondary flame
Weld crater susceptible to cracking
Number of sparks in the air increases just before a burn through
Burnout does not happen to molten metal until it reaches the kindling temperature
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18. Outside Corner Joint
Flat outside corner joint made with or without filler metal
One of the easiest welded joints to make
Filler metal not needed if sheets are tacked properly
Filler metal is added uniformly
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19. Lap Joint Flat lap joint easily welded with basic manipulations
Use caution when heating the two sheets
Both sheets start melting at the same time
Direct the flame on the bottom sheet away from top sheet
Filler rod added to the top sheet
Gravity pulls the molten weld pool down
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20. Tee Joint Flat tee joint is difficult because the Uneven heating
Large percentage of welding heat is reflected back on the torch
Angle the torch in the direction of weld travel (push technique)
Adjust the flame to be somewhat oxidizing
Keep a tight coupling distance to focus heat at the root.
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21. Out-of-position Welding
Welds performed in position other than flat
The following welds are out of position:
Vertical
Horizontal
Overhead
Somewhat more difficult than flat welds
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22. Common OAW Vocabulary Base Metal Weld Metal Filler Metal
Toe and Crater of weld
Delivery Pressure vs. Working Pressure
Flashback vs. Backfire
Oxygen vs. Air
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23. Summary
Learning to control the heat input to the weld by changing the torch angle, height, or travel speed is important
Oxyacetylene welding is the process of preference for thin materials
The most common problem with OFW welding is heat and weld distortion
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24. Where to Get More Information
Owners Manual
Welding Principles and Applications by Larry Jeffus
PCC Welding
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