Production Technology(IND 006)

Preparatory Year,

Faculty of Engineering,

Fayoum University

Dr. Ahmed Salah Abou Taleb

Lecturer, Industrial Engineering Dept.,

Faculty of Engineering, Fayoum University

Lecture No. 6

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Joining and Fastening Processes

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Introduction

Why using joining and fastening processes?

1- Products are impossible to be manufactured as a single piece due to size or transport constraints.

2- Repair of products during their service life.

3- Products made of different materials.

Joining and Fastening Processes

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Joining and Fastening Processes

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1- Mechanical Fasteners:

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Fastening Processes

Permanent Non-permanent

riveting, press or shrink fitting

assembly with threaded fasteners

2- Adhesive Bonding (gluing or glue bonding):

Natural Inorganic Synthetic

These are made from natural ingredients.e.g.: Starch, dextrin, soya flour, animal

products

There are made from inorganic

chemical materials

e.g.: sodium silicate,

magnesium oxychloride

Are based on natural and synthetic rubbers.

They set by solvent evaporation or heat

curing. e.g.: thermoplastic and

thermosetting plastic

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Adhesive Bonding

– Welding is a materials joining process which produces coalescence of materials by heating them to suitable temperatures with or without the application of pressure, and with or without the use of filler material.

– Welding is used for making permanent joints.

– Applications: ships, pressure vessels, automobile bodies, off-shore platform, welded pipes, sealing of nuclear fuel, explosive, aircraft frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, and general repair work.

3- Welding Process:

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Joining Processes

welding processes could be classified according to the type of energy used in performing the process.

3- Welding Process:

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Joining Processes

Welding Process

Heat Energy

Mechanical Energy

Both Energy

Fusion Welding

Friction Welding

Resistance Welding

3-1- Arc Welding (Fusion Welding):

• The heat is obtained from electrical energy.

• The arc is produced between tip of electrode & workpiece.

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Joining Processes

Joining Processes

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3-1- Arc Welding (Fusion Welding):

The basic elements involved in arc welding process:

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Joining Processes

3-1- Arc Welding (Fusion Welding):

The heat generated in arc melts a portion of the tip of electrode, its coating and base metal.

Function of electrode coating:

1- Stabilize the arc.2- Generate gases to act as a shield against

atmosphere.3- Control the rate which the electrode melts.4- Produce slag which protects the molten weld pool.5- Add alloying elements to the weld zone to enhance

the properties.

Joining Processes

Advantages Most efficient way to join

metals.

Most simple method.

Lowest-cost joining method

Portable equipment useful in remote area

Affords lighter weight through better utilization of materials

Joins all commercial metals

Provides design flexibility

Workpiece thickness range from 3 to 20 mm

Limitations• Manually applied, therefore

high labor cost.

• Need high energy causing danger

• Not convenient for disassembly.

• Defects are hard to detect at joints.

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3-1- Arc Welding (Fusion Welding):

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Joining Processes

3-1- Arc Welding (Fusion Welding):

Applications:General constructions, ship building, pipelines, and maintenance work.

Other arc welding processes1- Submerged arc welding: The weld arc is shielded by

granular flux.2- Gas metal arc welding: The weld area is shielded by

inert gas.3- Flux-cored arc welding: Tubular electrode filled with

flux.4- Gas tungsten arc welding: Non-consumable electrode

plus filler wire plus inert gas.

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Joining Processes

3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

A fusion welding process which joins metals, using the heat of combustion of an oxygen and fuel gas (i.e. acetylene, hydrogen propane or butane).The intense heat (flame) thus produced melts and fusestogether the edges of the parts to be welded, with the addition of a filler metal.

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Joining Processes

3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

Joining Processes

• Maximum temperature reached at tip of inner cone, while outer envelope spreads out and shields work surface from atmosphere.

• Oxyacetylene can also be used for cutting metals

• Shown below is neutral flame of oxyacetylene torch indicating temperatures achieved

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3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

1- Oxygen is turned on, flame immediately changes into a long white inner area (Feather) surrounded by a transparent blue envelope is called Carburizing flame (30000c)

• Used for welding: high carbon steel.

Joining Processes

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3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

2- Addition of little more oxygen give a bright whitish cone surrounded by the transparent blue envelope is called Neutral flame (It has a balance of fuel gas and oxygen) (3200 0C)

• Used for welding: mild steel, stainless steel, cast iron, copper, and aluminum.

Joining Processes

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3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

3- If more oxygen is added, the cone becomes darker and more pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame

• Has the highest temperature about 34000c

• Used for welding: copper base and zinc base metals.

Joining Processes

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3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

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Advantages

Portable.

Low cost equipment.

Suitable for all welding positions.

Can be used in cutting and preheating.

Flux:

used to remove the oxide film and to maintain a clean surface.

Joining Processes

Limitations

Together, acetylene and oxygen are highly flammable.

C2H2 is colorless and odorless.

3-2- Gas ”Oxy Fuel” Welding (Fusion Welding):

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Terminological elements of welding process used with common welding joints

Joining Processes

3-3- Weld Joint (Fusion Welding):

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For welding the edges of joining surface of metals are prepared first.

Joining Processes

3-3- Weld Joint (Fusion Welding):

Joining processes

4- Brazing & Soldering:

• Filler metal distributed by capillary action

• Only filler metal is melted, not base metal

• Strength of joint typically

– Can join dissimilar metals

– Less heat - can join thinner sections (relative to welding)

– stronger than filler metal itself

– weaker than base metal

– Excessive heat during service can weaken joint

• Pros & Cons

• Lower temperatures in all welding processes.

• Metallurgical bond formed between filler & base metals

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Joining processes

4-1 Soldering:Solder = Filler metal

Applications:

• Printed Circuit Board (PCB) manufacture

• Pipe joining (copper pipe)

• Jewelry manufacture

Easy to solder: copper, silver, gold

Difficult to solder: aluminum, stainless steels

• Alloys of Tin (silver, bismuth, lead)

• Melt point typically below 300 0C.

Flux used to clean joint & prevent oxidation

• Typically non-load bearing

Tinning = pre-coating with thin layer of solder

• separate or in core of wire (rosin-core)

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Joining processes

4-2 Brazing:

Applications:

• Pipe/Tubing joining (HVAC)

• Filler metals Cu alloys (silver, zinc & phosphorus)

• Melt point typically above 300 0C)

• Automotive - joining tubes

• Electrical equipment - joining wires

• Jewelry Making

• Flux also used

• Types of brazing classified by heating method:

– Torch, Furnace, Resistance

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Workshop This Week (4-7/4/2015)

Day Time Slot 3 Time Slot 4

Saturday Workshop 5 Workshop 5

Sunday Reparation

Monday Reparation Workshop 5

Tuesday Workshop 5 Workshop 5

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Lecture Power Point, Assignments, & Grades

www.fayoum.edu.eg/ahmedsalah