Oxyacetylene Welding By Matt Scott 1 392021 Introduction
Oxyacetylene Welding By Matt Scott 1 3/9/2021
Introduction l 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. 2 3/9/2021
8 Steps to Making a Quality Weld 1. 2. 3. 4. 5. 6. 7. 8. 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. 3 3/9/2021
Step 1 – Safety l 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? l SAFETY FIRST!!!!! 4 3/9/2021
Step 2 and 3 – TIP Selection & Setting the Gas Pressure Metal Thickness Tip Size Drill Size Up to 1/32” 1/16”-3/64” 1/32”-5/64” 3/64”-3/32” 1/16”-1/8”-3/16”-1/4” ¼”-1/2” ½”-3/4” ¾”-1 ¼”-2” 2 ½”-3” 3 ½”-4” 000 00 0 1 2 3 4 5 6 7 8 10 12 75 (. 022) 70 (. 022) 65 (. 035) 60 (. 040) 56 (. 046) 53 (. 060) 49 (. 073) 43 (. 089) 36 (. 106) 30 (. 128) 29 (. 136) 27 (. 144) 25 (. 149) Oxygen Pressure (PSIG) Min. Max. 3 5 3 5 3 5 4 7 5 10 6 12 7 14 8 16 10 19 12 24 18 28 Acetylene Pressure (PSIG) Min. Max. 3 5 3 5 3 5 3 6 4 7 5 8 6 9 8 10 9 12 12 15 Acetylene Consumption (SCFH) Min. Max. 1 2 1½ 3 2 4 3 6 5 10 8 18 10 25 15 35 25 45 30 60 35 75 50 100 80 160 Victor Cutting Equipment 5 3/9/2021
Step 4 – Ensure the Tip is Clean l Indicators of a clean tip are: – Preheat flame is sharp and ¼” in length. – Secondary flame does not splinter 6 3/9/2021
Step 5 - Set torch to Neutral Flame l l l 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 7 3/9/2021
Step 6 – Get Comfortable l Steady yourself when welding 8 3/9/2021
Mild Steel Welds Oxyacetylene welding is limited to thin metal sections or when portability is important l Today almost exclusively used on thin metal l An electric arc welding processes is usually used for welding thicker metal l 9 3/9/2021
Mild Steel Welds Easiest metal to gas weld l Welds with 100% integrity possible l Secondary flame shields the molten weld pool from the air l Atmospheric oxygen combines with carbon monoxide to produce carbon dioxide l Carbon dioxide forces surrounding atmosphere away from the weld l 10 3/9/2021
Factors Affecting the Weld The torch tip size controls the weld bead width, penetration, and speed l Torch angle and the angle between the inner cone and the metal effect: l – Speed of melting – Size of the molten weld pool l Welding rod size and torch manipulation control the weld bead characteristics 11 3/9/2021
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. 12 3/9/2021
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If the buildup on both welds is removed, weld (B) would be stronger 16 3/9/2021
Characteristics of the Weld Molten weld pool must be protected by the secondary flame l Weld crater susceptible to cracking l Number of sparks in the air increases just before a burn through l Burnout does not happen to molten metal until it reaches the kindling temperature l 17 3/9/2021
Outside Corner Joint Flat outside corner joint made with or without filler metal l One of the easiest welded joints to make l Filler metal not needed if sheets are tacked properly l Filler metal is added uniformly l 18 3/9/2021
Lap Joint Flat lap joint easily welded with basic manipulations l Use caution when heating the two sheets l – Both sheets start melting at the same time Direct the flame on the bottom sheet away from top sheet l Filler rod added to the top sheet l Gravity pulls the molten weld pool down l 19 3/9/2021
Tee Joint Flat tee joint is difficult because the Uneven heating l Large percentage of welding heat is reflected back on the torch l Angle the torch in the direction of weld travel (push technique) l Adjust the flame to be somewhat oxidizing l Keep a tight coupling distance to focus heat at the root. l 20 3/9/2021
Out-of-position Welding Welds performed in position other than flat l The following welds are out of position: l – Vertical – Horizontal – Overhead l Somewhat more difficult than flat welds 21 3/9/2021
Common OAW Vocabulary Base Metal l Weld Metal l Filler Metal l Toe and Crater of weld l Delivery Pressure vs. Working Pressure l Flashback vs. Backfire l Oxygen vs. Air l 22 3/9/2021
Summary Learning to control the heat input to the weld by changing the torch angle, height, or travel speed is important l Oxyacetylene welding is the process of preference for thin materials l The most common problem with OFW welding is heat and weld distortion l 23 3/9/2021
Where to Get More Information l l l Owners Manual Welding Principles and Applications by Larry Jeffus PCC Welding 24 3/9/2021
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