Oxyacetylene Welding By Matt Scott 4/15/2017

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. 4/15/2017

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. 4/15/2017

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!!!!!!!!! 4/15/2017

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 4/15/2017

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 4/15/2017

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 4/15/2017

Step 6 – Get Comfortable Steady yourself when welding 4/15/2017

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 4/15/2017

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 4/15/2017

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 4/15/2017

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. 4/15/2017

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If the buildup on both welds is removed, weld (B) would be stronger 4/15/2017

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 4/15/2017

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 4/15/2017

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 4/15/2017

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. 4/15/2017

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 4/15/2017

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 4/15/2017

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 4/15/2017

Where to Get More Information Owners Manual Welding Principles and Applications by Larry Jeffus PCC Welding 4/15/2017