INTRODUCTION TO OXYACETYLENE WELDING

LEARNING GOALS

• We will distinguish between various low-temperature welding processes.

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• We will define oxyfuel welding.

PROCESS TERMINOLOGY

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• Fusion Welding-any processes that joins metals by heating them together to their melting point

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• Oxyfuel Gas Welding-uses oxygen and fuel gases to fuse work pieces by heating them. Can be used with or without filler metal.

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• Oxyacetylene Welding-type of fusion welding; heats base metal until they become liquid and flow together and solidify

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PROCESS TERMINOLOGY

• Flame Cutting-uses high temperature oxidation (combines metal and oxygen) to cut metal

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• Brazing-metal pieces are heated above 840*F but below their melting points; uses a filler metal

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• Braze Welding-similar to brazing but the filler metal does not fill the joint using capillary action

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• Soldering-metal pieces are heated below 840*F and below the melting point of the base metal; uses solder to fill the small spaces with capillary action

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OTHER DEFINITIONS

• Molten: Liquid metal

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• Fusing: Heating two or more metals until they become liquid and allowing them to flow together and solidify

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• Capillary action: Occurs when a liquid is drawn into a small gap between mating parts

OFW OVERVIEW

OFW = Oxygen Fuel Gas Welding

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Requires fuel gas & oxygen

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FUEL GAS OPTIONS

Acetylene

• Produces the hottest flame

Methylacetylene-propadiene

• MAPP

Propylene

Propane

Natural Gas

• Methane

FUEL GAS CHARACTERISTICS

FUEL GAS CHARACTERISTICS - CONTINUED

FUEL GAS CHARACTERISTICS - CONTINUED

OXYACETYLENE

• Flame temperature=5,589*F

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• With this you can:
• Weld steel
• Cut steel
• Braze
• Solder
• Heat treat

Bead without Filler Metal

Bead with Filler Metal

OA WELDING

OA WELDING

ADVANTAGES OF OFW

Variety of Thickness

No Slag

No Spatter

High Quality Welds

Low Cost Equipment

No Electricity Required

All Position Welding

Extremely Portable

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LIMITATIONS OF OFW

Primarily Ferrous Materials

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Must Operate under “Hot Zone” Concept

• (Fire Hazard)

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Various Hazards Associated with Fuel Gases, Oxygen and High Pressure Gases

Flashbacks & Backfires

Often Slow

Cannot Weld with All Fuel Gases

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BRAZING

BRAZING OVERVIEW

Brazing: Bonding of metals and alloys that melt at temperatures above 840 F when capillary action occurs

• The temperature of properly prepared metal must first be raised to the melting point of the brazing alloy to be used.
• The brazing alloy is then added by means of a long, thin rod called a filler rod. Copper-zinc alloys are the most popular filler rods for brazing. The alloy is drawn between parts and spreads throughout the spaces.

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Braze Welding: bonding with alloys that melt at or above 840 F, when capillary action does not occur

• Metal is bonded to each part, and the void between or around the part is filled with the metal alloy.

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COMPARISON OF �BRAZING AND BRAZE WELDING

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Brazing�

Uses capillary action and a thin layer of braze metal to join two pieces of base metal

Braze Welding

�The alloy bonds to each part without capillary action

ADVANTAGES TO BRAZE WELDING

The process allows:

• The use of low temperatures
• Disassembly of the parts
• Different metals can be joined
• Working at high speeds
• Little damage to parts
• Easy realignment of parts
• Parts with various thicknesses to be joined

BRAZING A LAP JOINT

BRAZING A LAP JOINT

BRAZING A LAP JOINT

SOLDERING

SOLDERING PROCESSES

Mini OA torch set

Butane gas soldering gun

SOLDERING OVERVIEW

Soldering: the bonding occurs with metal alloys that melt at temperatures below 840 F

• Some common uses of soldering are to join electrical wires, join copper gutters and spouts, sweat copper pipes, and fasten tin-plated steel.

ADVANTAGES TO SOLDERING

• Soldered joints have excellent heat and electrical conductivity
• Widely used in the electronics industry
• Can be used to create joints that are leak-proof, neat, and have low electrical resistance
• Preferred method for joining many types of materials, such as soft copper

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