AMERICAN UNIVERSITY OF SCIENCE AND TECHNOLOGY
FACULTY OF ENGINEERING
DEPARTMENT OF COMPUTER AND COMMUNICATIONS ENGINEERING
DEPARTMENT OF MECHATRONICS ENGINEERING
GAS WELDING
Engineering Workshop
CCE/MTE 203
AUST – 2021
Gaby Abou Haidar, Ph.D.
GABY ABOU HAIDAR, PH.D.
Oxy-Fuel Welding
GABY ABOU HAIDAR, PH.D.
Introduction
 Welding is
a fabrication or sculptural process that joins
materials, usually metals or thermoplastics,
by using high heat to melt the parts together
and allowing them to cool causing fusion.
 Welding is distinct from lower temperature
metal-joining techniques such
as brazing and soldering, which do
not melt the base metal.
GABY ABOU HAIDAR, PH.D.
Oxy-Fuel-Gas Welding
1. Oxy-fuel-gas welding (OFW) is a general term used to describe any welding process that uses a fuel gas
combined with oxygen to produce a flame. This flame is the source of the heat that is used to melt the metals
at the joint.
2. Fuel gas used in welding can be acetylene, propane, hydrogen, butane and natural gas. Of these, acetylene is
by far the most widely used because the temperatures obtained by combustion of acetylene are much higher
than those obtained by combustion of other gases.
3. Oxy-acetylene flame temperature, for example, is of the order of 3500°C compared to 3000°C for oxyhydrogen or epoxy butane flame and 2800°C for natural gas flame. The medium of combustion of fuel gases is
generally oxygen though sometimes compressed air is also used. Use of air, leads to reduced thermal
efficiency, lower welding speed and poorer quality of the welds. The choice of gases for gas welding is thus
restricted to choice of correct fuel gas for the desired welding speed and quality of weld.
4. Oxy-acetylene gas welding process is widely used commercially for welding of ferrous and non-ferrous metals
particularly for thin sections up to 6 mm thick. The process is also useful for a large amount of repair work.
Typical applications of the process include fabrication of ventilation and air-conditioning ducts and repair of
vehicles. The process is also indispensable in early stages of the installation of a new plant. Oxy-hydrogen gas
welding is used for welding thin sheets of steel and low melting temperature materials.
GABY ABOU HAIDAR, PH.D.
Oxy-Acetylene Welding Equipment
GABY ABOU HAIDAR, PH.D.
Oxy-Acetylene Welding Equipment
GABY ABOU HAIDAR, PH.D.
Gas Welding Flow Gauge Settings
GABY ABOU HAIDAR, PH.D.
Gas Welding Flow Gauge Settings
GABY ABOU HAIDAR, PH.D.
Gas Welding Flow Gauge Settings
GABY ABOU HAIDAR, PH.D.
Gas Welding Flow Gauge Settings
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Gas Welding Pressure Gauge Settings
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Welding Torch
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Welding Torch
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Torch Tips
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Types of Flames
 Neutral flame
 Oxidizing flame
 Carburizing or reducing flame
GABY ABOU HAIDAR, PH.D.
 The proportion of acetylene and oxygen in the gas mixture is an important
factor in oxy-fuel-gas welding.
 At ratio 1:1 (no excess of oxygen) the flame is considered to be neutral.
 With a greater oxygen supply, the flame can be harmful, because it oxidizes the
metal.
 For this reason a flame with excess oxygen is known as an oxidizing flame.
 If the oxygen is insufficient for full combustion, the flame is known as a reducing
or carburizing flame (excess of acetylene).
GABY ABOU HAIDAR, PH.D.
Flame Temperature
 The flame temperature depends on the oxygen to acetylene ratio and increases with
increase in this ratio up to a certain point.
 The limiting values are 1.2 to 1.9 with corresponding temperatures of 3300 to
3500°C.
 The maximum temperature obtained in a reducing flame is about 2900°C, that in a
neutral flame about 3250°C and for an oxidizing flame about 3500°C.
GABY ABOU HAIDAR, PH.D.
Flame Temperature
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Flame Temperature
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Flame Temperature
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Flame Temperature
GABY ABOU HAIDAR, PH.D.
Fillers
 Filler metals are used to supply additional metal to the weld zone during welding.
 They are available as filler rods or wire and may be bare or coated with flux.
 The purpose of the flux is to retard oxidation of the surfaces of the parts being welded by
generating a gaseous shield around the weld zone.
 The flux also helps to dissolve and
remove oxides and other substances
from the weld zone, thus contributing to
the formation of a stronger joint.
 The slag developed protects the molten
puddle of metal against oxidation as it
cools.
GABY ABOU HAIDAR, PH.D.
Welding Practice
Qxy-fuel-gas welding can be used with most ferrous and nonferrous metals for almost any work piece
thickness, but the relatively low heat input limits the process to thicknesses of less than 6 mm. The
basic steps can be summarized as follows:
1. Prepare the edges to be joined and establish and maintain their proper position by busing clamps
and fixtures.
2. Open the acetylene valve and ignite the gas at the tip of the torch.
3. Open the oxygen valve and adjust the flame for that particular operation.
4. Hold the torch at about 45o from the plane of the work piece with the inner flame near the work
piece and the filler rod at about to 30 0 to 40 0.
5. Touch the filler rod to the joint and control its movement along the joint length by observing the
rate of melting and filling the joint.
GABY ABOU HAIDAR, PH.D.
Welding Practice
 Small joints made by this process may consist of a single weld bead.
 Deep V-groove joints are made in multiple passes.
 Cleaning the surface of each weld bead prior to depositing a second layer is important
to joint strength and to avoid defects.
 The use of safety equipment (such as goggles with shaded lenses, face shields, gloves,
and protective clothing) is essential.
 Oxygen and acetylene cylinders have different threads, so the hoses cannot be
connected to the wrong cylinders.
GABY ABOU HAIDAR, PH.D.
Welding Practice
GABY ABOU HAIDAR, PH.D.
Oxy Fuel Cutting Practice
Oxyacetylene welding/cutting is not difficult, but there are a good number of subtle
safety points that should be learned such as:
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More than 1/7 the capacity of the cylinder should not be used per hour.
This causes the acetone inside the acetylene cylinder to come out of the cylinder and
contaminate the hose and possibly the torch.
Acetylene is dangerous above 1 atm (15 psi) pressure. It is unstable and explosively
decomposes.
Proper ventilation when welding will help to avoid large chemical exposure.
GABY ABOU HAIDAR, PH.D.
Oxy Fuel Cutting Practice
GABY ABOU HAIDAR, PH.D.
Oxy Fuel Cutting Practice
GABY ABOU HAIDAR, PH.D.
Oxy Fuel Cutting Practice
GABY ABOU HAIDAR, PH.D.
Oxy Fuel Cutting Practice
GABY ABOU HAIDAR, PH.D.
Oxy Fuel Gas Types and Characteristics
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The Importance of Eye Protection
 Proper protection such as welding goggles should be worn at all times, including to protect the eyes against glare
and flying sparks.
 Special safety eyewear must be used—both to protect the welder and to provide a clear view through the yelloworange flare given off by the incandescing flux.
 Didymium eyewear, developed for glassblowers in the 1960s, was also borrowed—until many complained of eye
problems from excessive infrared, blue light, and insufficient shading.
 Today very good eye protection can be found designed especially for gas-welding aluminum that cuts the sodium
orange flare completely and provides the necessary protection from ultraviolet, infrared, blue light and impact,
according to ANSI Z87-1989 safety standards for a Special Purpose Lens
GABY ABOU HAIDAR, PH.D.
Watch the gas welding video