Oxyacetylene Welding
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Transcript of Oxyacetylene Welding
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Oxyacetylene Welding Oxyacetylene Welding
By Matt Scott
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Introduction 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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8 Steps to Making a Quality Weld 8 Steps to Making a Quality Weld
1. Safety Check2. Select a tip based on metal thickness3. Adjust gas pressures4. Ensure the tip is clean5. Set torch to neutral flame6. Get Comfortable7. Maintain a consistent Coupling Distance8. Oscillate torch to ensure fusion.
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Step 1 – SafetyStep 1 – Safety
At a Glance – 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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Step 2 and 3 – TIP Selection & Step 2 and 3 – TIP Selection & Setting the Gas PressureSetting the Gas Pressure
Victor Cutting Equipment
MetalThickness
TipSize
DrillSize
OxygenPressure(PSIG)
AcetylenePressure(PSIG)
AcetyleneConsumption
(SCFH)Min. Max. Min. Max. Min. Max.
Up to 1/32” 000 75 (.022) 3 5 3 5 1 21/16”-3/64” 00 70 (.022) 3 5 3 5 1 ½ 31/32”-5/64” 0 65 (.035) 3 5 3 5 2 43/64”-3/32” 1 60 (.040) 3 5 3 5 3 61/16”-1/8” 2 56 (.046) 3 5 3 5 5 101/8”-3/16” 3 53 (.060) 4 7 3 6 8 183/16”-1/4” 4 49 (.073) 5 10 4 7 10 25
¼”-1/2” 5 43 (.089) 6 12 5 8 15 35½”-3/4” 6 36 (.106) 7 14 6 9 25 45¾”-1 ¼” 7 30 (.128) 8 16 8 10 30 601 ¼”-2” 8 29 (.136) 10 19 9 12 35 752 ½”-3” 10 27 (.144) 12 24 12 15 50 1003 ½”-4” 12 25 (.149) 18 28 12 15 80 160
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Step 4 – Ensure the Tip is CleanStep 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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Step 5 - Set torch to NeutralStep 5 - Set torch to Neutral Flame 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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Step 6 – Get ComfortableStep 6 – Get Comfortable
Steady yourself when welding
Mild Steel Welds 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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Mild Steel WeldsMild Steel Welds
Easiest metal to gas weldWelds with 100% integrity possibleSecondary flame shields the molten weld
pool from the airAtmospheric oxygen combines with carbon
monoxide to produce carbon dioxideCarbon dioxide forces surrounding
atmosphere away from the weld
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Factors Affecting the WeldFactors 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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Step 7&8 Coupling Distance Step 7&8 Coupling Distance and Torch Manipulation 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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If the buildup on both welds is removed, weld (B) would be strongerIf the buildup on both welds is removed, weld (B) would be stronger
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Characteristics of the WeldCharacteristics of the Weld
Molten weld pool must be protected by the secondary flame
Weld crater susceptible to crackingNumber of sparks in the air increases just
before a burn throughBurnout does not happen to molten metal
until it reaches the kindling temperature
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Outside Corner JointOutside Corner Joint
Flat outside corner joint made with or without filler metal
One of the easiest welded joints to makeFiller metal not needed if sheets are tacked
properlyFiller metal is added uniformly
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Lap JointLap 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 sheetGravity pulls the molten weld pool down
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Tee JointTee JointFlat tee joint is difficult because the
Uneven heatingLarge percentage of welding heat is
reflected back on the torchAngle the torch in the direction of weld
travel (push technique)Adjust the flame to be somewhat oxidizingKeep a tight coupling distance to focus
heat at the root.
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Out-of-position WeldingOut-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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Common OAW VocabularyCommon OAW Vocabulary
Base Metal Weld MetalFiller Metal Toe and Crater of weldDelivery Pressure vs. Working PressureFlashback vs. BackfireOxygen vs. Air
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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SummarySummary
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Where to Get More InformationWhere to Get More Information
Owners Manual Welding Principles
and Applications by Larry Jeffus
PCC Welding