Title: Basic Principles of SSW.
1INTRODUCTION ATOMIC BONDING FREE ENERGY
2Introduction 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
3Definition 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.
4Linnert, Welding Metallurgy, AWS, 1994
5(No Transcript)
6Examine the Web Page
7Homework
- Submit Your Bio-sketch
- Do the Pre-Course Survey
- Email to get your student code
Dickinson.1_at_osu.edu
8These 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
9Introduction 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.
10Advantages 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.
11Disadvantages 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.
12Solid 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.
13Solid 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.
14Solid 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
15Types of Solid State Welds
We Will Look At Each
Linnert, Welding Metallurgy, AWS, 1994
16Questions
17Basic Principles
- In solid state welding, joining of two surfaces
takes place by atomic bonding between the atoms
on the surfaces.
18Atomic Bonds
- There are two major types of atomic bonds
- Primary bonds
- Secondary bonds
- Primary bonds are much stronger than secondary
bonds.
19Primary Bonding
- Primary bonds include three types
- Ionic bonds
- Covalent bonds
- Metallic bonds
20Ionic 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
21Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
22Kotz, 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)
24Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
25Kotz, 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.
27Questions
28Secondary 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.
29Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
30CoCl2 - 6 H2O
Ion - Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
31Dipole - Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
32Dipole - Induced Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
33Induced Dipole - Induced Dipole Interaction
Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
34Kotz, Chemistry Chemical ReaCTIONS, Saunders
College Pub., 1999
35(No Transcript)
36Questions
37Adhesion 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
38Free 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
39Free 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.
40Summary for Similar Metals
Free energy formation of a weld
A
B
g0
g0
gAB
41Summary 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.
42Link to Bonding Demo
43End of Atomic Bonding
44Homework