Basic Principles of SSW. - PowerPoint PPT Presentation

1 / 40
About This Presentation
Title:

Basic Principles of SSW.

Description:

ATOMIC BONDING FREE ENERGY Definition of Solid State Welding A group of welding processes that produces coalescence at temperatures essentially below the melting ... – PowerPoint PPT presentation

Number of Views:20
Avg rating:3.0/5.0
Slides: 41
Provided by: Industria
Category:

less

Transcript and Presenter's Notes

Title: Basic Principles of SSW.


1
INTRODUCTION ATOMIC BONDING FREE ENERGY
2
Introduction to Atomic Bonding and Free Energy
  • Lesson Objectives
  • When you finish this lesson you will understand
  • History, Background and Uses of Solid State
    Bonding
  • Atomic and Molecular Bonding Principles
  • Primary Secondary Bonds
  • Free Energy Considerations and Adhesion
  • Learning Activities
  • View Slides
  • Read Notes,
  • Listen to lecture
  • Examine Web Page
  • Do on-line workbook
  • View Demo
  • Do Homework

Keywords Solid State Bonding, Atomic Bonding,
Primary Bonds, Secondary Bonds, Ionic Bonding,
Covalent Bonding, Metallic Bonding, Free Energy
3
Definition of Solid State Welding
Definition
  • A group of welding processes that produces
    coalescence at temperatures essentially below the
    melting point of the base metal. Pressure may or
    may not be used.

4
Linnert, Welding Metallurgy, AWS, 1994
5
(No Transcript)
6
Examine the Web Page
7
Homework
  • Submit Your Bio-sketch
  • Do the Pre-Course Survey
  • Email to get your student code

Dickinson.1_at_osu.edu
8
These PowerPoint Slides have Supplemental
Information
Click on Edit Slides Notes Page View to see
Slide Notes Or Click on Icons When They Appear on
Page
Examine Key Topic From Welding Encyclopedia
Look It Up
Dig Deeper About This
See Demo
Hear Explanation
Industrial Applications
9
Introduction to Solid State Welding
  • History of solid state welding dates back to very
    ancient time.
  • Gold was hammered together by the ancients
    earlier than 1000 B.C.
  • The iron framework of the Colossus of Rhodes was
    forge welded in 280 B.C.
  • Versatility of fusion welding eclipsed solid
    state welding in the first half of the 20th
    century.
  • Solid state welding experienced a rebirth in the
    60s and 70s, especially in the field of
    micro-electronics.

10
Advantages of Solid State Welding
Broad View for Motivation
  • Eliminates liquid phases.
  • Makes the joining of many dissimilar metal
    combinations possible.
  • Can be applied at different temperatures and
    under different stresses
  • At high temperature, where the atomic interaction
    range is relatively large and solubility of
    contaminants is high, parts can be joined
    together with less deformation.
  • At low temperature, where the atomic interaction
    range is relatively small and solubility of
    contaminants is low, more stress is needed to
    join two parts together and thus more deformation
    is expected.

11
Disadvantages of Solid State Welding
  • Surface preparation can be necessary.
  • Joint design is limited.
  • Elaborate and expensive equipment may be
    required.
  • Non-destructive inspection is very limited.

12
Solid State Welding Materials
Materials
  • Both similar and dissimilar metals can be welded.
  • Similar metal welds include
  • Titanium-to-titanium alloy (aircraft rivets) by
    friction welding.
  • Ultrasonic welding of fine aluminum wire to
    aluminum metallization in microelectronics.
  • Examples of dissimilar metal includes
  • Aluminum to steel, titanium to aluminum, and
    titanium to stainless steel (tubular transition
    joint) by explosion welding.

13
Solid State Welding Applications
Applications
  • Bonding of stainless steel liners in aluminum fry
    pans.
  • Aluminum cladding bonded to uranium fuel rods.
  • Ultrasonic and thermo-compression bonding in the
    microelectronics industry.
  • Friction welding in aero-space and automotive
    applications.
  • Drill pipe.
  • Intake / exhaust automatic valves.
  • Bi-metallic pipe.

14
Solid State Welding
Applications
Explosion clad titanium steel tube sheet blanks
180 inch diameter dome of 3/16 inch type 410
stainless steel on 3 inch thick A387 steel formed
from explosion weld.
Courtesy AWS handbook
15
Types of Solid State Welds
We Will Look At Each
Linnert, Welding Metallurgy, AWS, 1994
16
Questions
17
Basic Principles
  • In solid state welding, joining of two surfaces
    takes place by atomic bonding between the atoms
    on the surfaces.

18
Atomic Bonds
  • There are two major types of atomic bonds
  • Primary bonds
  • Secondary bonds
  • Primary bonds are much stronger than secondary
    bonds.

19
Primary Bonding
  • Primary bonds include three types
  • Ionic bonds
  • Covalent bonds
  • Metallic bonds

20
Ionic Bonding
  • Bonding takes place between metallic and
    nonmetallic elements.
  • Metallic atoms give up valence electrons to
    nonmetallic atoms.
  • Examples NaCl, MgO, CaCl2.

Na
Cl
Na
Na
Cl
Cl
Cl
Na
Na
21
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
22
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
23
Covalent Bonding
  • Bonding between two atoms takes place by
    cooperative sharing of electrons.
  • Examples Gas - N2, O2, CH4.
  • Solid - carbon (diamond), silicon, germanium.

Methane (CH4)
24
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
25
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
26
Metallic Bonding
  • Valence electrons are not bound to any particular
    atom and are free to drift throughout the metal.
  • Remaining non-valence electrons and atomic nuclei
    form ion cores.
  • Free electrons act as a glue to hold the ion
    cores together.

27
Questions
28
Secondary Bonding
  • Van der Waals bonds ( Ar, Kr, Ne).
  • Polar molecule-induced dipole bonds (HCl, HF).
  • Hydrogen bonds ( H2O, NH3).
  • Bond energy only about 1/10 of primary bonds.
  • Can cause adhesion of contaminants to metal
    surfaces.

29
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
30
CoCl2 - 6 H2O
Ion - Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
31
Dipole - Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
32
Dipole - Induced Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
33
Induced Dipole - Induced Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
34
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
35
(No Transcript)
36
Questions
37
Adhesion of Perfect Metal Surfaces
10 A
  • Adhesion of metal surfaces occurs
    by inter-atomic forces.
  • For this to happen, the two mating surfaces
    must be brought together within a very close
    distance.
  • For most metals, this distance is within a range
    of approximately 10 angstroms (A).

From Materials Science and Engineering An
Introduction by W.D. Callister, John Wiley
Sons, 1985
38
Free energy formation of a weld
  • The potential energy of atoms at the free surface
    is higher than that of atoms within the bulk of
    the solid.
  • The energy per unit area possessed by atoms near
    the free surface constitutes the free surface
    energy.
  • The average surface atom has about half the
    bonding energy of an interior atom.

missing bond
A
B
Surface energy of A is greater than B
39
Free energy formation of a weld
  • The welding of metal A to metal B results in a
    decrease in free energy (DGweld).
  • This negative energy difference (DGweld) creates
    a driving force which actually promotes welding.

A
B
g0
g0
g0 and gAB are surface energies (surface
tension) of the free surfaces and grain
boundaries respectively.
40
Summary for Similar Metals
Free energy formation of a weld
A
B
g0
g0
gAB
41
Summary for Dissimilar Metals
Free energy formation of a weld
  • A similar relationship can be developed for
    dissimilar metal welding showing a large negative
    (-) DG for all dissimilar metal combinations.

42
Link to Bonding Demo
43
End of Atomic Bonding
44
Homework
Write a Comment
User Comments (0)
About PowerShow.com