Introduction to Oxyfuel Welding 273

acetone

A flammable liquid used to clean contaminants from surfaces or help store other chemicals. Acetone is used in acetylene cylinders to dissolve and safely store acetylene.

acetylene

A colorless, flammable gas that consists of carbon and hydrogen. Acetylene is the most common fuel gas used in oxyfuel welding.

alloys

A substance consisting of a mix of two or more elements, one of which must be a metal. Steel is an alloy of carbon and iron.

aluminum

A nonferrous, silvery-white metal that is soft and light. Aluminum is one of the most difficult metals to weld.

arc welding

A group of welding processes that use electricity to generate the heat needed to melt the base metals. Arc welding is the most common form of welding.

base metals

Metal that is welded together to form a joint. The base metal and its properties influence the type of welding and filler rod that should be used.

brass

An alloy of copper and zinc. Brass has high tensile strength and corrosion resistance.

braze welding

A welding process that deposits a filler metal with a melting point above 840°F (449°C) but below the melting point of the base metals. Braze welding is similar to brazing but uses welding joint designs and does not use capillary action.

brazing

A joining process that uses capillary action to draw in a filler metal with a melting point above 840°F (449°C) but below the melting point of the base metals. Brazing is similar to braze welding but uses different joint designs.

brittleness

A material's unwillingness to be drawn, stretched, or formed. Brittleness tends to cause materials to fracture when subjected to these forces.

capillary action

The process of a liquid being drawn into a space between objects. Capillary action occurs in soldering and brazing when metal is drawn between the metals being joined.

carbon

A common nonmetallic element found in gas form in the air and released as gas from burning various fuels. Carbon and hydrogen make up acetylene.

carbon steels

An alloy of iron and carbon that contains less than 3% other alloying elements. The amount of carbon in a carbon steel affects its strength, ductility, and malleability.

carburizing flame

An oxyfuel flame that contains more acetylene than oxygen. Carburizing flames burn at lower temperatures than neutral and oxidizing flames.

check valves

A one-way valve that prevents gas from flowing backwards from a welding torch into hoses and cylinders. Check valves are located at the bottom of the torch near the hose connectors.

coalescence

A feature of joints made by melting the base metals. Coalescence occurs during oxyfuel welding, but braze welding, brazing, and soldering do not produce coalescence.

combustible

A material that can quickly catch fire if it comes in contact with sparks or fire. Combustible materials catch fire at higher temperatures than flammable materials.

copper

A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper is often used to coat filler metal rods.

cutting

The act of separating a workpiece into two or more pieces. Cutting can be done with traditional methods, such as milling or sawing, or more advanced methods, such as oxyfuel and plasma cutting.

cylinders

An airtight metal container designed to hold gases at high pressures. Cylinders are specially designed and manufactured to hold specific gases.

defects

An irregularity in the specified and expected composition of a weld that exceeds the part design's tolerances. A defect is an unacceptable discontinuity.

distortion

The non-uniform expansion of weld metal during the heating and cooling process of welding. Distortion can be reduced by using oxyfuel welding, which has a lower heat input.

ductwork

A system constructed of thin sheets of metal that is designed to transport air. Ductwork is used extensively in the heating, ventilation, and air conditioning (HVAC) industry.

electric arc

The area in which electricity jumps from an electrode to a workpiece. Electric arcs produce extreme heat and light.

equal pressure

An oxyfuel torch that requires equal pressures of oxygen and fuel gas to ensure the gases reach the mixing chamber simultaneously and mix properly. Equal pressure torches are also called positive-pressure or medium-pressure torches.

ferrous

Containing iron. Ferrous metals are the most common type of welded materials.

filler metal

Metal added to a weld that often adds strength and mass to the welded joint. Filler metal generally has properties similar to those of the base metals.

filler rods

A unit of filler metal that is manually added to the weld pool by the welder. Filler rods usually match the composition of the base metal and can add beneficial mechanical properties to the finished weld.

fittings

A component that connects, redirects, extends, or terminates the run of a fluid conductor. A fitting contains the fluid by providing a seal.

flammable

A material that can quickly catch fire if it comes in contact with sparks or fire. Flammable materials catch fire at lower temperatures than combustible materials.

flashback

A torch malfunction that occurs when the flame moves past the torch and into the gas hoses or gas cylinders. Flashback can cause explosions if not prevented or controlled.

flashback arrestors

A device that prevents flames from reaching into the gas hoses or cylinders when flashback occurs. Flashback arrestors are typically installed between the gas hoses and the torch and/or between the gas hoses and cylinders, but they may also be integrated into torches.

flat

A welding position used to weld from the upper side of a joint. In the flat position, the face of the weld is horizontal.

flux

A nonmetallic material that is intended to clean and protect the weld pool and solid metal from contamination. Flux is often a part of an electrode or filler rod.

fuel gas

A gas that can store potential energy and release it as thermal energy or that can be used to perform work. Fuel gases are mixed with oxygen to perform oxyfuel processes such as welding and cutting.

fusible plugs

A safety device included in acetylene gas cylinders that is designed to melt if the cylinder is exposed to excessive heat. Fusible plugs help prevent acetylene cylinders from exploding.

gas hoses

A flexible tube, often made of synthetic rubber, used to transport gas. Gas hoses connect gas cylinders to the torch in oxyfuel welding.

gas welding

A welding process that uses a flame produced by a mixture of oxygen and fuel gas to fuse metals. Gas welding may or may not use filler metal and is often referred to by the standard term oxyfuel welding.

Grade R

A type of gas hose designed for use with oxygen and acetylene. Grade R hoses are not recommended for other fuel gases.

Grade T

A type of gas hose that is primarily used for alternative fuels, such as propane and natural gas, but can also be used for acetylene. Grade T hoses are designed to resist the oils in many alternative fuels.

hardness

A material's ability to resist penetration, indentation, or scratching. Hardness in a metal may change due to the heat generated during welding.

heat input

The amount of thermal energy transferred to the workpiece during welding. Heat input is measured in kilojoules per inch (kJ/in.) or kilojoules per millimeter (kJ/mm).

high-carbon steel

A plain carbon steel that contains more than 0.50% carbon. High-carbon steels are extremely strong and hard, and they always require heat treatment for effective welding.

high-strength steel

A steel alloy that offers high yield and tensile strength. High-strength steel filler rods are often used to improve the strength of a weld.

horizontal

A welding position used to weld from the upper side of a horizontal surface and against a vertical surface. The horizontal position is often used for fillet and groove welds.

hose connectors

A fitting on an oxyfuel torch used to attach gas hoses to the torch. Hose connectors are made of brass to ensure safety and durability.

hydrogen

A colorless, odorless active gas that is the most abundant element on the planet. Hydrogen and carbon make up acetylene.

infrared radiation

The energy emitted by light sources with wavelengths just longer than red light. Infrared radiation, which cannot be seen with the human eye, can cause eye and skin irritation.

injector

The component in an injector torch that draws a fuel gas into the oxygen stream. The injector helps use fuel gases efficiently at lower pressures and helps mix the gases before they reach the torch.

injector torch

An oxyfuel torch with an internal injector nozzle that uses a stream of oxygen to pull fuel gas into the mixing chamber. Injector torches are also called low-pressure torches.

in-tip mixers

A mixing chamber that is located within the welding tip of a torch. In-tip mixers help with proper gas mixing and can help produce more stable flames.

joint

The meeting point of two materials that are fused together. Welding creates a permanent joint.

left-hand threads

A type of thread that fastens components when it is rotated counterclockwise. Left-hand threads are used on the fittings that connect oxyfuel components, such as gas hoses to torches.

low-alloy steel

A steel that contains small amounts of intentionally added materials that change the properties of the metal. Low-alloy steels commonly contain manganese, molybdenum, and nickel.

low-carbon steel

A carbon steel that contains 0.05-0.15% carbon. Low-carbon steels are generally tough, ductile, and easy to weld.

low-pressure

An oxyfuel torch with an internal injector nozzle that uses a stream of oxygen to pull fuel gas into the mixing chamber. Low-pressure torches are also called Injector torches.

MAPP gas

Methylacetylene-propadiene propane gas. A colorless, flammable gas mixture made by combining methylacetylene, propadiene, and propane gases. MAPP gas can be used as a fuel gas for oxyfuel processes.

methylacetylene-propadiene propane gas

MAPP gas. A colorless, flammable gas mixture made by combining methylacetylene, propadiene, and propane gases. Methylacetylene-propadiene propane gas can be used as a fuel gas for oxyfuel processes.

mild steel

A carbon steel that contains 0.15-0.30% carbon. Mild steels are generally tough, ductile, and easy to weld, but they have slightly lower weldability than low-carbon steels.

mixing chamber

The component of an oxyfuel torch where the oxygen and fuel gas combine prior to existing the torch. The mixing chamber may be located in either the torch tip or the torch body.

natural gas

A flammable gas that occurs underground. Natural gas can be used as a fuel gas for oxyfuel welding, brazing, and soldering.

neutral flame

An oxyfuel flame that contains equal amounts of oxygen and acetylene. A neutral flame is preferable for oxyfuel welding.

nonferrous

Not containing iron. Common nonferrous metals include aluminum and copper.

nuts

A fastener with a hole and internal threads that mates with a bolt or screw. Nuts are used to secure gas hoses in welding systems.

OAW

Oxyacetylene welding. An oxyfuel welding process that uses a flame produced by a mixture of oxygen and acetylene fuel gas. OAW is the most common type of oxyfuel welding since acetylene provides the most ideal flame and heat input for welding.

OFW

Oxyfuel welding. A welding process that uses a flame produced by a mixture of oxygen and fuel gas to fuse metals. OFW may or may not use filler metal and is sometimes referred to by the non-standard term gas welding.

orifice

A hole at the end of a torch tip through which gases escape. Orifice shape and size determines the applications for specific tips.

overhead

A welding position used to weld from the underside of a joint. The overhead position requires extra safety precautions.

oxidation

A metal's chemical reaction with oxygen. Oxidation can weaken a metal's surface.

oxides

A chemical compound containing oxygen and one other element. Oxides can cause weld defects if they are not removed.

oxidizing flame

An oxyfuel flame that contains more oxygen than acetylene. Oxidizing flames burn at higher temperatures than neutral and carburizing flames and should be avoided.

oxyacetylene

A mix of oxygen and acetylene gas that is used to fuel a flame for welding. Oxyacetylene produces a hotter flame than other gas mixtures used for oxyfuel welding.

oxyacetylene welding

OAW. An oxyfuel welding process that uses a flame produced by a mixture of oxygen and acetylene fuel gas. Oxyacetylene welding is the most common type of oxyfuel welding since acetylene provides the most ideal flame and heat input for welding.

oxyfuel cutting

OFC. A thermal cutting process that uses a flame produced by a mixture of oxygen and fuel gas along with a high-pressure stream of oxygen that reacts with and severs metal. Oxyfuel cutting is sometimes called by the non-standard terms flame cutting or gas cutting.

oxyfuel welding

OFW. A welding process that uses a flame produced by a mixture of oxygen and fuel gas to fuse metals. Oxyfuel welding may or may not use filler metal and is sometimes referred to by the non-standard term gas welding.

oxygen

A colorless, odorless, tasteless, active gas that naturally exists in the atmosphere. Oxygen is mixed with fuel gas to produce a flame in oxyfuel welding processes.

penetration

The depth to which welding heat melts the joint below the surface of the base metals. Penetration is directly affected by various factors, such as fuel gas, welding process, and heat input.

personal protective equipment

PPE. Any clothing or device worn or used to minimize exposure to hazards and prevent injury. Personal protective equipment for welding usually includes a welding helmet, jacket, safety glasses, and gloves.

porosity

A discontinuity characterized by the appearance of tiny voids in a weld bead, which occurs when gas is trapped in the weld metal. Excessive porosity can weaken a weld.

Positive-pressure torch

An oxyfuel torch that requires equal pressures of oxygen and fuel gas to ensure the gases reach the mixing chamber simultaneously and mix properly. Positive-pressure torches are also called equal-pressure or medium-pressure torches.

post-processing

A procedure used to clean, improve, or otherwise finish a part after it is fabricated. Post-processing procedures include abrasive finishing, heat treating, and painting.

pounds per square inch

psi. A measurement of the amount of load pressure that is applied over an area of one square inch. Pounds per square inch is used in the English system.

power plants

A facility that uses combustion or another force to generate electricity. Power plants have demanding requirements because they must operate continually at high temperatures while achieving high efficiency.

power source

The device that provides the electricity needed to power a circuit. Power sources are required to perform arc welding.

propane

A colorless, flammable gas created during petroleum refinement processes that outputs lower heat as it burns. Propane is the second-most common fuel gas for oxyfuel welding.

propylene

A colorless, flammable gas created during petroleum refinement processes that outputs higher heat as it burns. Propylene can be used as a fuel gas for oxyfuel processes.

psi

Pounds per square inch. A measurement of the amount of load pressure that is applied over an area of one square inch. The psi unit is used in the English system.

regulator

A device used to reduce the pressure of gas from cylinders to a useable working pressure for welding and cutting. Regulators consist of a control valve and a flowmeter or gauge that indicates the pressure and flow rate of gas.

right-hand threads

A type of thread that fastens components when it is rotated clockwise. Right-hand threads are used on the fittings that connect oxyfuel components, such as gas hoses to torches.

sheet metal

A flat metal stock that is no greater than 0.25 inches (0.64 centimeters) thick. Sheet metal is often made into ductwork using oxyfuel processes.

shielded

A weld pool being protected from environmental contaminants during the welding process. Shielded weld pools are commonly protected by flux, shielding gas, or a combination of both.

single fuel torches

An oxyfuel torch that has a dedicated fuel gas supply but no direct source of oxygen. Single fuel torches draw in atmospheric oxygen through openings and are mostly used for soldering and brazing because they produce less heat.

soldering

A joining process that uses a filler metal with a melting point below 840°F (449°C). Soldering is often used for delicate projects such as jewelry and electronics.

stainless steel

A type of steel that contains 11-30% chromium and exhibits excellent hardness and corrosion resistance. Stainless steel can be welded with many different welding processes.

striker

An inexpensive and easy-to-use device that uses friction to safely ignite the fuel gas flowing from an oxyfuel torch. Strikers are also called spark lighters.

thermal cutting

A cutting process that uses heat to remove metal from a workpiece. Thermal cutting processes include oxyfuel, air carbon arc, plasma arc, and laser beam cutting.

torch handle

The main part of an oxyfuel torch that connects the torch tip to the rest of the torch and connecting components. The torch handle contains internal hoses that direct the flow of gases to the mixing chamber.

twin-line hoses

A set of color-coded gas hoses that includes a green hose for oxygen and a red hose for acetylene and other fuel gases. Twin-line hoses are mounted together in a setup or molded together permanently.

two-piece tips

A welding tip that consists of an outer shell with an insert designed to improve the burning efficiency of alternative fuels. Two-piece tips replace preheating holes in other tips for slower-burning gases.

valve

A mechanical device that controls the flow of fluids such as liquid or gas. Valves contain movable parts that open, close, or obstruct one or more openings or passageways.

ventilation

A means of moving air to remove contaminants and provide clean air. Ventilation reduces the hazards posed by welding fumes and gases.

vertical

A welding position used to weld on a vertical surface, moving up or down. Welding in the vertical position is more difficult than flat- or horizontal-position welding.

weld pool

The small area of molten metal that forms during welding and that, when cooled, forms the permanent joint. Weld pools are sometimes called weld puddles.

welding

A joining process that permanently bonds two separate components together. Welding uses heat, pressure, friction, or a combination of methods to make a new part.

welding position

The position in which a welder performs a weld. Welding positions include the flat, horizontal, vertical, and overhead positions.

welding tip

The component of a torch that includes the orifice through which gases escape. The welding tip helps control and direct the flame.

welding torch

The instrument used to generate the arc or flame for welding. An oxyfuel welding torch uses the controlled combustion of gases to produce a flame.