Ch 9 Joining of Metals [Read-Only] - kau 9 Joining of... · 2015-05-11 · Advantages and...
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Transcript of Ch 9 Joining of Metals [Read-Only] - kau 9 Joining of... · 2015-05-11 · Advantages and...
5/11/2015
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Basic WorkshopBasic Workshop
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Joining of Metals
Welding
RivetingClamping
Adhesive Bonding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Welding Process
Welding is the process of joining together two pieces of metals through
heat alone (fusion welding) with/without filler material or through heat
and pressure (Forging) without filler material.
Welding
Pressure Welding
Friction Welding
Resistance Welding
Forge Welding
Fusion Welding
Thermit Welding
Arc Welding
Gas Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Five basic types of weld joint designs
Types of Joints and Welding Positions
Welding Process
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Four Welding Positions
Welding Process
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Fusion Welding
Fusion welding is a process in which metals are welded together by brining
them to the molten state at the surface to be joined with or without the
addition of filler metal without pressure.
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
1. Gas welding:Oxyacetylene welding (OAW)
2. Arc welding:Shielded metal arc welding (SMAW)
Gas–tungsten arc welding (GTAW)
Plasma arc welding (PAW)
Gas–metal arc welding (GMAW)
Flux-cored arc welding (FCAW)
Submerged arc welding (SAW)
Electroslag welding (ESW)
3. High-energy beam welding:
Electron beam welding (EBW)
Laser beam welding (LBW)
Three major types of fusion welding are as follows:
Fusion Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Variation of heat input to the workpiece with power density of the heat source
Fusion Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Gas WeldingOxy – Acetylene Welding
Gas welding is a process that melts and
joins metals by heating them with a flame
caused by the reaction between a fuel gas
and oxygen
Fusion Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Temperature distribution in a neutral
oxyacetylene flame
Gas WeldingOxy – Acetylene Welding
Fusion Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Three Types of Flames
Neutral Flame: This refers to case where oxygen and acetylene
are mixed in equal amounts and burned at the tip of the torch
Reducing Flame: When excess acetylene is used, the resulting
flame is called a reducing flame. The combustion of acetylene is
incomplete
Oxidizing Flame When excess oxygen is used, flame becomes
oxidizing because of the presence of unconsumed oxygen
Gas WeldingOxy – Acetylene Welding
Fusion Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Welding Movements
Forward weldingBackward welding
Gas WeldingOxy – Acetylene Welding
Fusion Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Advantages and Disadvantages
The main advantage of the oxyacetylene welding process is that
• The equipment is simple,
• Portable, and
• Inexpensive.
It is convenient for maintenance and repair applications.
However, due to its limited power density,
• The welding speed is very low, and
• The total heat input per unit length of the weld is rather high,
resulting in large heat-affected zones and severe distortion.
The oxyacetylene welding is not recommended for welding reactive metals such
as titanium and zirconium because of its limited protection power
Gas WeldingOxy – Acetylene Welding
Fusion Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Flame cutting of a steel plate with an oxyacetylene
torch, and a cross section of the torch nozzle.
Cross section of a flame-cut
plate, showing drag lines
Gas WeldingOxy – Acetylene Welding
Fusion Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
� Thermit material is a mixture of Al and processed iron oxide.
� A wax pattern is then made around the joint .
� A mold made of refractory sand is built around the wax pattern and
joint to hold the molten metal after it is poured.
� The sand mold is then heated to melt out the wax and dry the mold.
� The mold should be properly vented to permit the escape of gases
and to allow the proper distribution of the metal at the joint.
Thermit Welding
Fusion Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Thermit Welding
Fusion Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Electric arc welding is a fusion welding where high temperature is obtained from
the electrical energy, filler material is needed, which is molten to the gab between
the two parts to be joined.
The electric are circuit consists of:� The power supply,
� An electrode cable,
� A ground cable,
� An electrode holder, and
� The electrode rod.
Electrod
e
Electrode
holder
Base Metal
Power
supply
Filler
materialGround
Power supply
Fusion Welding
Electric Arc Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Shielded arc welding is a process that
melts and joins metals by heating
them with an arc established between
a covered electrode and the metals
Fusion Welding
Electric Arc Welding
Shielded Metal Arc Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Functions of Electrode CoveringCovering of the electrode contains various chemicals and metal powder in order
to perform one or more of the functions:
1. Protection2. Deoxidation3. Arc stabilization4. Metal Addition
Advantages and DisadvantagesThe welding equipment is:
• Relatively simple, and
• Inexpensive as compared to other arc welding processes.
Gas shield is not clean enough for reactive metals such as Al and Ti.
The limited length of the electrode (about 35cm) requires electrode changing,
and this further reduces the overall production rate
Fusion Welding
Electric Arc Welding
Shielded Metal Arc Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Gas–tungsten welding is a process that melts and
joins metals by heating them with an arc between
a nonconsumable tungsten electrode and metals
The gas goes through the torch body and is directed
by a nozzle toward weld pool to protect it from air.
Protection from air is much better than in Shielded
arc welding.
Fusion Welding
Electric Arc Welding
Gas Tungsten Arc Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Advantages of Gas-Tungsten Arc Welding
� Suitable for joining thin sections because of its limited heat inputs.
� It can be used to weld butt joints of thin sheets by fusion without the addition of
filler metals
� Gas–tungsten arc is a very clean process, it can be used to weld reactive metals,
such as Ti and zr, Al, and Mg.
Disadvantages of Gas-Tungsten Arc Welding
� The deposition rate is low.
� Excessive welding currents can cause melting of electrode and results in brittle
tungsten inclusions in the weld metal.
Fusion Welding
Electric Arc Welding
Gas Tungsten Arc Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Gas–metal arc is a process that melts and joins
by heating them with an arc established between
a continuously fed filler wire electrode and the
metals.
Shielding arc and the molten weld pool is often
obtained by using inert gases such as argon and
helium
Fusion Welding
Electric Arc Welding
Gas Metal Arc Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Advantages
� Gas–metal arc welding can be very clean when using an inert shielding gas.
� The main advantage of Gas–metal arc over Gas–tungsten arc is the much
higher deposition rate, which allows thicker workpiece to be welded at
higher welding speeds.
Disadvantages
� Gas–metal arc welding guns can be bulky and difficult to reach small areas
or corners.
Fusion Welding
Electric Arc Welding
Gas Metal Arc Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Pressure Welding
Pressure welding is a process in which metals are welded together by
bringing them to the plastic state (without melting) at the surfaces to
be joined while pressing them together.
Pressure Welding
Friction Welding
Resistance Welding
Forge Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Resistance Welding
� Resistance welding uses the electric current and mechanical pressure
to create a weld between two pieces of metal.
� Weld electrodes conduct the electric current to the two pieces of metal
as they are forged together
Resistance welding types:
• Resistance Spot Welding,
• Resistance Seam Welding,
• Projection Welding
Pressure Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Resistance Welding Benefits
• High speed welding
• Easily automated
• Suitable for high rate production
• Economical
Resistance Welding Limitations
• Initial equipment costs
• Lower tensile and fatigue strengths
• Lap joints add weight and material
Resistance Welding
Pressure Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Spot Welding
Seam Welding
Projection Welding
Resistance Welding
Pressure Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
� Friction Stir Welding is a solid state joining (the metal is not melted during
the process), in which a cylindrical shouldered tool (pin) is inserted into the
joint line between two work pieces.
� Frictional heat is created between the wear resistant pin and the two pieces,
which are butted together and clamped onto a backing bar
Friction Stir Welding
Pressure Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Friction Stir Welding
Pressure Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Friction Stir Welding
Pressure Welding
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
� Good mechanical properties in the as welded condition
� No consumables and no filler or gas shield is required.
� Easily automated on milling machines - lower set-up costs.
� Can operate in all positions (horizontal, vertical, ….etc).
� Generally good weld appearance and minimal thickness
� Low environmental impact.
� Exit hole left when tool is withdrawn.
� Large forces required with heavy clamping necessary.
� Less flexible than arc processes.
� Slower traverse rate.
Disadvantages of the process
Advantages of the process
Friction Stir Welding
Pressure Welding
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Clamping
Temporary ConnectionsThese clamps are used to position or hold
components temporarily for various tasks
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
A rivet is a permanent mechanical fastener. Before being installed a
rivet consists of a smooth cylindrical shaft with a head on one end.
The end opposite the head is called the buck-tail.
Riveting
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
� The rivet is placed in a punched or pre-drilled hole, and the tail is upset so that it
expands to about 1.5 times the original shaft diameter, holding the rivet in place.
� To distinguish between the two ends of the rivet, the original head is called the
factory head and the deformed end is called the shop head or buck-tail
Riveting
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Riveting
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
1
2
3 4
5
6
Riveting
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Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Adhesive bonding
• Adhesive bonding describes a wafer bonding technique with applying
an intermediate layer to connect substrates of different materials.
• These produced connections can be soluble or insoluble.
• The commercially available adhesive can be organic or inorganic and
is deposited on one or both substrate surfaces.
The most important process parameters for achieving a high bonding
strength are:
� adhesive material
� coating thickness
� bonding temperature
� processing time
� chamber pressure
Dr. Abdel-Wahab El-Morsy Faculty of Engineering - Rabigh
Materials that soften by heating and then cooling it becomes hardened again and
this material Polyamide, vinyl polymers and cellulose derivatives in addition to
natural materials (i.e. resins and waxes)
Thermo Plastic Adhesive
Thermo Setting Adhesive
A material that becomes hardened as a result of chemical reactions and can not
therefore be re-relaxation again by heating after hardened
Adhesive materials can be divided depending on the nature of the hardening of two types
Adhesive bonding