Non-Arc Welding Processes Continued

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Non-Arc Welding Processes Continued
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Non-Arc Welding Processes (Cont.)

• Learning Activities
• Look up Keywords
• View Slides
• Read Notes,
• Listen to lecture
• Do on-line workbook
• Do homework

• Lesson Objectives
• When you finish this lesson you will understand
• High Energy Density Welding, Advantages and
  Disadvantages
• Soldering and Brazing Systems
• Plastics Bonding
• Adhesive Bonding

Keywords Laser Beam Welding (LBW), Electron Beam
Welding (EBW), Plasma Plume, YAG, Soldering,
Brazing, Flux, Wave Soldering, Hot Plate
Welding, Hot Gas Welding, Vibration Welding,
Ultrasonic Welding, Thermoplastic, Thermoset,
Adhesive Bonding, Curing
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Non-Arc Welding Processes
Introduction

• Resistive heating, chemical reactions, focused
  light and electrons, sound waves, and friction
  can also be used to join materials
• Resistance welding
• Oxy-Fuel Welding
• Friction welding (Solid State)
• Laser and electron beam welding
• Brazing and soldering
• Plastics joining
• Adhesive bonding

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High Energy Density Processes
High Energy Density Processes

• Focus energy onto a small area
• Laser
• CO2 gas fixed position
• Nd-YAG crystal fiber-optic delivery
• Electron Beam

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High Energy Density Processes

• These processes focus the energy onto a small
  area
• Laser - 0.0001-inch thick stainless steel sheet
• Electron Beam - 0.030-inch weld width on 0.5 inch
  thick steel plate

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Laser Beam Welding (LBW)
Laser
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Laser Beam Welding (LBW)
High Energy Density Processes

• Single pass weld penetration up to 3/4 in steel
• Materials need not be conductive
• No filler metal required
• Low heat input produces low distortion
• Does not require a vacuum

Plasma keyhole
Keyhole welding
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Focusing the Beam
High Energy Density Processes
Heat Surface Welding
Cutting treatment modification
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Advantages

• Single pass weld penetration up to 3/4 in steel
• High Travel speed
• Materials need not be conductive
• No filler metal required
• Low heat input produces low distortion
• Does not require a vacuum

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Limitations
High Energy Density Processes

• High initial start-up costs
• Part fit-up and joint tracking are critical
• Not portable
• Metals such as copper and aluminum have high
  reflectivity and are difficult to laser weld
• High cooling rates may lead to materials problems

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Electron Beam Welding (EBW)
EB Applications
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Electron Beam Welding (EBW)
High Energy Density Processes
Advantages

• Deepest single pass weld penetration of the
  fusion processes
• 14-inch-thick steel
• Fast travel speeds
• Low heat input welds produce low distortion

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Limitations
High Energy Density Processes

• High initial start-up cost
• Not portable
• Part size limited by size of vacuum chamber
• Produces x-rays
• Part fit-up is critical
• High cooling rates may lead to materials problems

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Questions?

• Turn to the person sitting next to you and
  discuss (1 min.)
• In laser welding, materials with high
  reflectivity reflect the beam right off the
  surface and no heat is absorbed and thus they are
  difficult to weld. What might we do to make
  these high reflectivity materials more weldable?

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Non-Arc Welding Processes
Introduction

• Resistive heating, chemical reactions, focused
  light and electrons, sound waves, and friction
  can also be used to join materials
• Resistance welding
• Oxy-Fuel Welding
• Friction welding (Solid State)
• Laser and electron beam welding
• Brazing and soldering
• Plastics joining
• Adhesive bonding

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Brazing (B) and Soldering (S)
Brazing and Soldering

• In these processes, the base metals are heated
  but do not melt only the filler metal melts
• Brazing filler metals having a melting point
  above 840 F (450C)
• Soldering filler metals have a melting point
  below 840F (450C)

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Brazing and Soldering
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Application of Low Thermal Expansion Alloys

• Thermal expansion mismatch in metal-ceramic
  joints can lead to cracks in the ceramic
• Thermal expansion coefficients at 25C (10-6 mm /
  mmC)
• Alumina, 8.8
• Nickel, 13.3
• Iron, 11.8
• Kovar, 5.0

Kovar lid
Silicon chip
Alumina substrate
Brazed joints
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Brazing Specifications
Brazing and Soldering

• AWS A5.8 Specification for Brazing Filler Metal
• 8 well-defined groups (B) plus a vacuum grade
  (BV)
• BAg-1 (44-46 Ag, 14-16 Cu, 14-18 Zn, 23-25 Cd)
• BAu-1 (37-38 Au, remainder Cu)
• BCuP-1 (4.8-5.2 P, remainder Cu)
• Standard forms strip, sheet, wire, rod, powder
• Joint design tolerances, generally 0.002 -
  0.006 inches
• Uses for each braze material
• AWS C3.3 Standard Method for Evaluating the
  Strength of Brazed Joints

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Balchin Castner, Health Safety, McGraw
Hill, 1993
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Advantages
Brazing and Soldering

• Joins unweldable materials
• Base metals dont melt
• Can be used on metals and ceramics
• Joined parts can be taken apart at a later time
• Batch furnace can easily process multiple parts
• Portable when joining small parts

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Limitations
Brazing and Soldering

• Joint tolerance is critical
• Lower strength than a welded joint
• Large parts require large furnaces
• Manual processes require skilled workers
• Flux

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Questions?

• Turn to the person sitting next to you and
  discuss (1 min.)
• Why is joint tolerance so critical?
• What happens if the joint space is too large?
• What happens if the joint space is too small?

• Turn to the person sitting next to you and
  discuss (1 min.)
• What happens if we do not have sufficient flux?

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Non-Arc Welding Processes
Introduction

• Resistive heating, chemical reactions, focused
  light and electrons, sound waves, and friction
  can also be used to join materials
• Resistance welding
• Oxy-Fuel Welding
• Friction welding (Solid State)
• Laser and electron beam welding
• Brazing and soldering
• Plastics joining
• Adhesive bonding

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Joining Plastics
Welding of Plastics
(Poly)ethylene

• Polymer - a single building block (mer) is
  repeated to form a long chain molecule
• Thermoplastic polymers soften when heated, harden
  when cooled
• 2-liter bottles
• Thermosetting polymers dont soften when heated
• Car tires, caulking compound

add H2O2
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Joining of Plastics

• Plastic (polymer) is a material in which single
  building blocks (mers) join to form a long chain
  or network molecule
• Thermoplastic polymers soften when heated and
  harden when cooled
• Foam cups (polystyrene), 2-liter bottles
  (polyethylene), Leisure suits (polyester)
• Thermosetting polymers become permanently hard
  when heat is applied and do not soften upon
  subsequent heating
• Car tires (isoprene, isobutene), Epoxy, Caulks
  (silicones)

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Hot Plate, Hot Gas, Infrared

• Advantages
• Provide strong joints
• Reliable
• Used on difficult to join plastics
• Limitations
• Slow
• Limited temperature range

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Hot Plate, Infrared Welding
Welding of Plastics
Hot plate welding
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Hot Gas Welding
Welding of Plastics

• Thermoplastics (hotmelts)
• Adhesive is heated until it softens, then hardens
  on cooling
• Hot gas softens filler and base material
• Filler is pulled or fed into the joint

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Vibration

• Advantages
• Speed
• Used on many materials
• Limitations
• Size
• Requires fixturing
• Equipment costly

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Ultrasonic

• Advantages
• Fast
• Can spot or seam weld
• Limitations
• Equipment complex, many variables
• Only use on small parts
• Cannot weld all plastics

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Questions?

• Turn to the person sitting next to you and
  discuss (1 min.)
• Make a list of some thermoplastic items you have
  recently seen that have been wlded.

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Non-Arc Welding Processes
Introduction

• Resistive heating, chemical reactions, focused
  light and electrons, sound waves, and friction
  can also be used to join materials
• Resistance welding
• Oxy-Fuel Welding
• Friction welding (Solid State)
• Laser and electron beam welding
• Brazing and soldering
• Plastics joining
• Adhesive bonding

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Adhesives

• Thermosets form long polymer chains by chemical
  reaction (curing)
• Heat is the most common means of curing
• Ultraviolet light, oxygen - acrylics
• Moisture - cyanoacrylates
• Thermoplastics (hotmelts)
• Adhesive is heated until it softens, then hardens
  on cooling -Polyethylene, PVC

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Curing of Adhesives
Adhesive Bonding

• Thermosets form long polymer chains by chemical
  reaction (curing)
• Heat (epoxy)
• Ultraviolet light, oxygen (acrylics)
• Moisture (superglue)

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Stress Modes - Best to Worst
2. Shear
1. Compression
3. Tension
5. Cleavage
4. Peel
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Why Adhesive Bonding?
Adhesive Bonding

• Dissimilar materials
• Plastic to metal
• Materials that can be damaged by mechanical
  attachments
• Shock absorption or mechanical dampening
• Laminate structures
• Skin to honeycomb structure

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Adhesive Selection
Adhesive Bonding

• Adhesive selection is based primarily on
• Type of substrate
• Strength requirements, type of loading, impact
  requirements
• Temperature resistance, if required
• Epoxy
• Cyanoacrylates
• Anaerobics - metals
• Urethanes
• Silicones
• Pressure sensitive adhesives (PSAs)

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Factors that Influence Process Selection
Process Selection

• Material joining needs
• Capabilities of available processes
• Cost
• Environment
• Required welding speed
• Skill level
• Part Fit-up

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Advantages

• Joining dissimilar materials - plastic to metal
• Materials that can be damaged by mechanical
  attachments
• Blind joints
• Shock absorption or mechanical dampening
• Temporary alignment
• Laminated structures
• Thin substrates - skin-to-honeycomb construction
• Stress distribution

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Limitations
Adhesive Bonding

• Adhesives dont do work, they distribute work
  they are not structural materials
• Environmental degradation
• Temperature
• Oxidation
• Difficult to repair
• Curing or setting time
• Surface preparation

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Homework
Do Homework Assignment 3 on More Welding
Processes and Turn in by next class period.