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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