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Oxyfuel Fusion Welding

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Presentation on theme: "Oxyfuel Fusion Welding"— Presentation transcript:

1 Oxyfuel Fusion Welding

2 Definition Oxyfuel fusion welding:
A welding process that uses an oxyfuel flame to melt the steel piece(s) forming a pool (puddle) that when cooled, solidifies to form the joint. How popular is the process today? Limited applications today. Usually limited to thin metal Electric arc welders have replaced oxyfuel for thicker metal. MIG welders have almost replace oxyfuel welding for thin metal.

3 Preparing To Weld What safety preparations should be completed before attempting an oxyacetylene steel fusion weld? How does oxyfuel welding meet the three requirements of fusion welding Heat Shielding Filler material Concrete or masonry floor Work area free of combustible material Clean gloves and clothing Appropriate fire extinguisher available Appropriate shaded face shield or goggles Pliers for handling hot metal Use equal working pressures _______ Flame Manual rod

4 Five (5) Factors Which Control The Quality of Oxyfuel Fusion Welds.
1. Heat 2. Filler rod 3. Torch position 4. Travel Speed 5. Manipulation

5 1. Heat Heat is provided by a flame utilizing oxygen and acetylene gas. Based on the laws of physics, what two methods can be used to control the flow of a gas? List the eight (8) ways that are used when oxyfuel fusion welding to control the heat of the weld. Change the pressure Change the orifice/pipe size When oxyfuel welding the amount of heat can be manipulated 8 (eight) ways. Size of tip Fuel gas working pressure Torch settings Torch angle Speed of travel Welding rod manipulation Size of welding rod Distance from the torch to the metal

6 Heat #1.1 - Tip Size What determines the best tip size to use?
Notice from the chart that tip sizes are not standardized. The tip size is determined by the thickness of the metal. Tip sizes are not standardized.

7 Heat #1.2 - Fuel gas working pressure
What determine the ideal working pressures? What is a possible problem with excessive working pressure? What is a possible problem with insufficient working pressure? Recommended fuel gas working pressure is based on metal thickness. Higher fuel gas working pressure will result in higher gas flow for the same torch setting. High fuel gas working pressure will contribute to a harsher flame which will make it more difficult to weld with small tips. Cold flame, reduced penetration

8 Heat #1.3 - Torch settings Torch setting refers to the position of the oxygen and acetylene torch valves. Which one of the torch valves controls the amount of heat? Which one of the torch valves controls the type of flame? Acetylene Oxygen Settings must be appropriate for the size of tip. A small tip set with excessive flow rate will produce a harsh flame. A large tip set too low will overheat.

9 Oxyfuel Welding Tips On the system that we use what is normally called a welding tip is actually a welding tip and a mixing chamber. The welding tip can be purchased separately—reduces cost.

10 Using Tip Cleaner Start with the smallest size that will enter the orifice without excessive force and work up to orifice size. Be careful, a broken tip cleaner usually means a destroyed tip. Clean the face of the tip with the included file.

11 Heat #1.4 - Torch Angles Two welding angles are important in OxyFuel welding. Work Travel Will increasing the travel angle change the heat at the weld? Explain! Yes. The closer the torch is to perpendicular the greater the heat at the weld—less is reflected away.

12 Heat # Travel Speed Why does changing the speed of travel change the temperature of the weld? The torch produces heat at a constant rate. Increasing the speed spreads the heat over a larger area = lower temperature

13 Heat #1.6 - Welding Rod Manipulation
Manipulating the torch produces a wider bead. The heat of the flame is applied to a larger area--lower weld temperature.

14 Heat #1.7 - Size of welding rod
Standard rods are 36 inches long and are available in a range of sizes from 1/16 to 1/4 inch diameter. A slightly larger or smaller rod than what is recommended can be used to manipulate the heat of the weld. Explain! The rod size can be used to manipulate the welding heat. Increasing the size of the rod will reduce the weld pool heat.

15 Heat #1.8 - Distance from the torch to the metal
The distance between the torch and the metal influences the temperature of the weld in two ways. As the distance is increased the heat is spread over a wider area. This reduces the temperature of the weld. 2. The temperature of the flame is not uniform.

16 Heat #1.8 - cont. What is the critical distance when oxyfuel fusion welding called? What is the distance? Torch Height 1/8 to ¼ inch

17 2. Filler Rod What are the desirable characteristics of the filler rod? How will use a rod larger or smaller than recommended affect the welding process? Compatible metal composition with the base metal Correct diameter = thickness of metal. _____ A larger rod will absorb more of the torch heat and reduce the heat at the weld. A smaller rod will absorb less heat.

18 3. Torch Position Critical torch positions are angle and height.
Explain the effect of having incorrect angle and/or height.

19 4. Welding Speed Travel speed should be adjusted so that as the edges of the puddle melt they form a collapsed key hole at the front edge of the puddle each time the rod is dipped into the weld puddle. What factors determine the ideal speed of travel? The ideal speed is determined by: The thickness of the base metal, Tip size Torch settings Torch motion.

20 5. Manipulation Three common manipulation patterns:
Circular/spiral C or crescent Dipping Torch manipulation is necessary When using all three types of torch manipulations, the torch should advance about 1/8 inch each time the torch passes the center of the weld. To travel at a faster welding speed, the torch manipulation rate must increase.

21 Oxyfuel Welding Process

22 Seven (7) steps to Oxyfuel Welding
Prepare metal Attach the correct welding tip Turn on system Set regulators to correct working pressure Light the torch and adjust the flame Form a puddle Manipulate torch and filler rod (if used) to complete the weld

23 1 - Prepare Metal You need to complete an oxyacetylene fusion weld on this piece of sheet metal. Should anything be done to the metal before you start? If so what? Any rust, scale, etc. on the surface of the metal will flow into the molten puddle and be oxidized by the flame. This can cause contamination that will prevent the molten steel from flowing. Cleaning should be by wire brush or grinder. A beveled edge may be required for some joints when welding thicker metal.

24 2 – Attach the correct tip
What determines the correct tip? How should it be attached? Thickness of metal Joint welding position snug by hand

25 3 - Turn On System What are the step for preparing an oxyacetylene system for use? Check regulator screw Inspect hoses and torch turn on cylinders (oxyall the way, acet ½-3/4 turn)

26 4 – Set Regulators How do you set the regulators to the correct working pressure? What do you do if you set the pressure to high? Turn in the adjusting screw until the desired pressure is set on the gauge. _____ Back out the regulator screw and open the torch valve to drain the pressure.

27 5 - Lighting Torch & Adjusting Flame
Should the acetylene or the oxygen torch valve be opened first? How far should you open the torch valve when starting the torch? Why? Acetylene---It determines the size of the flame Turn on fuel 1/8 turn or less Light the torch using a striker. Open the oxygen valve until the desired type of flame is set. Readjust the acetylene and oxygen until the desired flame is set Three parts to a flame Three types of flames

28 5 – Lighting Torch and Adjusting Flame – cont.
Fusion welding requires a neutral flame. Describe a neutral flame.

29 6 – Form Puddle Hold torch stationary, or 1/8 circle, at the beginning of the weld until the molten puddle is formed. Note: The puddle should form in 3 to 4 seconds.

30 7 – Manipulate Torch and Rod
Requirements; The torch must be moved to the back of the puddle before the rod is dipped in. The rod must be dipped into the molten puddle and withdrawn when the desired amount is melted off. The rod must stay within the outer flame. The rod a torch advance 1/8 – 3/16 inch each time the rod is withdrawn. A dipping motion is used with the rod for all three torch manipulations. The rod should be removed slightly from the puddle when the torch is the closest to the puddle. When dipped into the weld the rod must contact the center of the molten puddle. The filler rod should melt from heat of base metal, not from the direct heat of the torch. If the filler rod contacts the metal outside the puddle, it will stick to the metal. If the rod is melted in the air and forced to drip into the puddle, penetration will be reduced and the weld will be more irregular. Note: To produce a good weld the welder must practice until they can maintain a constant rhythm.

31 Joints & Spacing Use the correct joint preparation.
Square butt, no gap Square butt, gapped 1/16 to 3/32 Square butt, 60 deg bevel 1/16 to 1/8 root face, 1/16 to 3/32 gap Describe each one of these joints.

32 Acceptable Welds An acceptable weld has the designed strength and meets appearance standards. Strength Bending Tensile Appearance evaluation Uniformity Appropriate weld size Penetration Reinforcement Undercutting Starved joint

33 Unacceptable Welds Five unacceptable fusion weld conditions:
The weld doesn’t completely fill the joint. Surface reinforcement is greater than 1/8 inch. Undercutting is greater than 1/32 inch. The weld breaks during a bend test. The weld metal was not fused to the base metal.

34 Questions?

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