solderingwelding-171217173136-converted.pptx

 Definitions
 Ideal requirements of dental solder
 Soldering
1. Parent metal
2. Flux
A) Classification of flux
B) Ideal properties of flux
C) Application of flux
3. Anti-flux
4. Solder
A) Classification of solder
 Heat source
Contents:

 General principles for soldering
 Methods of soldering
1. Investment soldering
2. Free-hand soldering
 Technique consideration for soldering
 Soldering defects
 Welding
 Types of welding
1. Spot welding
2. Pressure welding
3. Laser welding
4. Laser micro welding
 References

Introduction
There are three categories of metal-joining operations: soldering,
brazing and welding
The common characteristic of these operations is the
achievement of bonding between the workpieces and/or the
filler metals by a controlled heating procedure.

SOLDERING: Is defined as the joining of metals by the fusion of
filler metal between them, at a temperature below the solidus
temperature of the metals being joined and below 450°C.
BRAZING: Is defined as the joining of metals by the fusion of filler
metal between them, at a temperature below the solidus
temperature of the metals being joined and above 450°C.
.

WELDING:Two pieces of similar metal are joined together without the
addition of another metal; that is, the metal pieces are heated to high
enough temperature so they join together by melting and flowing

Soldering is often used in construction of dental appliances.
Components of solder joint:
1. Parent metal
2. Flux
3. Anti-flux
4. Solder/filler metal

 The parent metal is the metal or alloy to be joined.
 It is also known as substrate metal or base metal.
 Soldering operation is the same for any

 The composition of parent metal determines:
1. Melting range
2. Oxide that forms on the surface during heating
3. Wettability of the substrate by the molten
solder.

 In Latin flux means “to flow”
 Purpose of flux is to remove any oxide coating
on the metal surfaces.
 They protect the alloy surface from oxidation
during soldering and dissolve metallic oxides as
they are formed.

A) CLASSIFICATION OF FLUX:
There are three types of fluxes according to their primary
purpose:
Type I. Surface protection—covers the metal surface and
prevents access to oxygen so that no oxides can form.
Type II. Reducing agent—reduces any oxides present and
exposes clean metal.
Type III. Solvent—dissolves any oxides present and
carries them away.

2. According to the pH of the flux:
a. Acidic fluxes – SiO2
b. Basic fluxes – CaO, lime CaCO3 LIMESTONE
c. Neutral – Fluoride flux
(Ca.F2),Borax (Na2B4O2)

3. Based on boric or borate compound:
a.TYPE I – protective fluxes by forming a low
temperature glass
b.TYPE II – reducing fluxes for low stability
oxides such as copper oxides
c. TYPE III – fluoride flux

B) Ideal Properties of Flux
 Its melting point must be lower than that of solder.
 It should lie quietly on the work while being fused and should not
increase in volume.
 After fusing, it should spread evenly and remain on the parent metal
without volatization.
 It must dissolve metallic oxides or other surface impurities likely
to occur on the surface a metal.
 It should be easily removable after soldering.

C) APPLICATION OF FLUX
 Painted on the substrate metal at the junction of
pieces to be joined.
 It may be Fused onto the surface of the parent
metal strip.

 Anti-Flux Materials used to restrict the flow of
solder are known as anti flux.
 It is applied on the surface of specific area
where the solder should not flow. It is
applied before applying flux or solder.
 E.g.: Graphite in the form of lead pencil.

 Disadvantage of graphite is that it can burn off
on prolonged heating at high temperature. In
such cases whiting (CaCO3 in Alcohol and
water suspension) is used.

 Desirable properties of dental solders:
 The fusion temperature must be at least 50-
100°C i.e. lower than the melting temperature of
the alloys to be joined.
 It must have good affinity for the metals upon
which it is used.

 It must flow freely, quickly and smoothly over
the surfaces of the parts to be joined. Adhesion
of the solder to the metal is essential.
 Its strength and hardness should be
comparable with that of parent metal.
 It should not cause pitting of
soldered joint.
 It must be resistant to tarnish and
corrosion.

 It should melt at low temperature
 When melted, it should wet and flow freely over
the parent metal
 Its colour should match that of metal being
joined
 It should be resistance to tarnish and
corrosion
 It should be resistance to pitting during heating
and application

A) CLASSIFICATION OF SOLDERS
1. Soft solders & Hard solders
• SOFT SOLDERS:
 They have low melting range of about 260°C
 Soft solders lack corrosion resistance, so
they are not suitable for dental use.
 Eg. lead- tin eutectic alloy (plumbers solder).

• HARD SOLDERS
 Hard solders have higher meting temperature &
have greater strength and hardness.
 They are melted with gas blow torch or with
electric furnace.
Two types of hard solders are used in dentistry:
gold solder & silver solder.

Gold Solder:
 Gold solders Has good
tarnish and corrosion
resistance
 Extensively used for crown
and bridge applications.
 Composition:
Gold – 45-81 wt %
Silver - 8-30 wt %
Copper -7-20 wt
% Tin –2–4 wt %
Zinc –2–4 wt %
They are high fusing with a fusion temperature range
of 750- 900° C

Silver Solder

Silver solders Used in
orthodontic appliances
They have low fusion
temp-600-750°C Used
with stainless steel or
other base metal alloys.
 Resistance to tarnish and corrosion is not as good
as gold solders But have strength comparable to
gold solders.
 • Composition:
Silver -10-80 %
Copper -15-30%
Zinc -4-35%

 It is most important part of brazing and soldering.
 The most commonly used heat source is gas-air or gas-oxygen
torch. And other is electric furnace.
 various gases used are…
1) Hydrogen: lowest heat content(1000*C)
slow heating
So not indicated for soldering of large bridges

2) Natural gas: Temperature of 2680*C
4 times that of hydrogen
Available in non uniform in composition

3) Acetylene: Highest flame temperature
(3140*C)
Higher heat content than hydrogen and natural
gas
Chemically unstable and decomposes readily into
carbon and hydrogen.

4) Propane: Highest heat content (2385*C)
Having good flame temperature (2850*C)
Best choice

• Thoroughly clean the parts to be joined by
immersing in dilute hydrochloric acid and then
polish with pumice.
• The parts to be joined must be placed in closest
possible contact with each other.
• Excessive amount of solder must not be used.
The strength of the soldered joint is greatest
when the minimum of solder is used.

• The temperature of flame must be carefully
controlled and flame held at proper distance.
Over heating must be avoided.
• Solder must be heated to its melting point as
quickly as possible, when the solder has melted
and filled the space between parts, remove the
flame and work is quenched in water.
• Oxidation must be avoided by using suitable
reducing flux and reducing zone of torch flame.

1) FREE-HAND SOLDERING
 Free hand soldering is used for soldering
orthodontic appliances.
 In this technique the parts to be soldered are
held in proper position by maintenance of gap
between parts manually.

Principle of free hand soldering:
 The parts to be soldered are cleaned and polished
 Parts should be in close approximation
 The liquid solder flows into the joint due to
capillary action.
 So optimum gap should be in 0.13 to 0.3 mm
range for proper flow and strength of joint
 Parts should be stable during application of heat

 Flux is applied to the joint area to allow a free
flow of solder and to prevent oxidation.
 The bridge assembly is preheated by the
application of reducing zone of flame.
 Oxidation of filler and parent material may
occur if proper zone of flame is not used.

 Flame provides protection from oxidation
especially at brazing temp.
 The solder is placed on the joint parts so
solder melts and flow into the gap
 As soon as soldering is completed, the
assembly is quenched in water.

2) INVESTMENT SOLDERING
 Parts to be joined are mounted on a soldering type
of investment and are held in position by the
hardened investment during application of heat
and solder
 Parts to be soldered are assembled on a cast and
the parts are joined by sticky wax with the
investment
 And wax is eliminated with the help of boiling
water
 Suitable solder is placed in the gap and subjected
to flame until completion of soldering

• Flame
• Gap
• Temperature
• Time

FLAME
The flame can be divided in to four zones

2) Gap:
 The liquid solder is draw into the joint through
capillary action.
 Thus optimum gap should be there for proper
flow and strength of joint
 Gap width should be ranging from 0.13 to
0.3mm

 What happens if gap is too narrow?
 Low strength
 Porosity caused due to incomplete flow
 What happens if gap is to great?
 The joint strength will be the strength of solder

Temperature:
 Should be minimum required to
complete the brazing
operation
 Prior to the placement of the solder,
parent metal is heated till it is hot
enough to melt the filler metal as soon as it
touches.
 A low temp will not allow the filler to wet the
parent metal

Time:
 The flame should be kept in place until the filler
metal has flowed completely into the connection
 Shorter time increases chances of incomplete
filling of joint
 Longer time increases possibility of diffusion
 Both conditions results in weaker joint

HYDROSOLDER
• This machine converts Water into oxy-hydrogen
fuel for an extremely hot and precise reducing
flame operating at 4850F.
• This machine is perfect for soldering and
brazing in the orthodontic laboratory
environment.

1) Porosity or pitting:
 It may occur during finishing and
polishing due to volatilization of lower
melting components as s result of higher
temp. and longer time
causes-
 Incorrect fluxing
 Incorrect flaming
 Incorrect cleaning
 Incorrect spacing of parts

2. Distortion of parts being soldered.
causes-
 Overheating
 Thermal expansion of the metal parts

 Wire to wire.

Tube can be soldered to the bridge of
the Adam’s clasp.
 Attachment of springs to arch wire,
 Soldering lingual arch or palatal arch.
 Soldering of various type of space management
appliances.
Application

 Two pieces of similar metal are joined together
without the addition of another metal.
 The metal pieces are heated to high enough
temperature so that they join together by
melting and flowing.

1.Cold welding is done by hammering or
pressure. An example of cold welding is the
gold foil filling.
2.Hot welding uses heat of sufficient intensity to
melt the metals being joined.
The heat source is usually an oxyacetylene
flame or high amperage electricity.

• Basically two methods are followed:
1) Fusion welding: where the parts are melted
and joined, but pressure is not applied.
E.g: Gas welding, Laser welding
2)Pressure welding: where parts are heated and
pressed , but not melted.
E.g.: Spot welding

• SPOT WELDING
• PRESSURE WELDING
• LASER WELDING
• LASER micro WELDING

1) Spot welding:
 The two clean metal surfaces to be welded are
placed together under pressure.
 Two ends of wire or band to be welded are
placed between two copper electrodes of
welder and pressed together
 When switch is pressed large current passes
through the wires or band on the copper
electrode.
 Combined heat and pressure fuses the metal
pieces at that point.

2) Pressure welding:
 This is also called cold welding and does not
require heat application
 Gold foil is welded by pressure or cold
welding
 Two layers of gold foil are joined by application
of pressure at room temperature.

3) LASER welding:
 LASER (‘Light Application by
Simulated Emission of Radiation’)
 It is clearly documented that laser welding
is stronger than solder joints of comparable
size.

LASER micro welding:
 The laser micro welder is high power industrial
laser capable of delivering 20J/pulse for
maximum of 6 mili seconds at a wire length of
1.06 microns.
 Micro welding can be done in intra-oral
orthodontic appliances such as normal arch
wire, ortho-surgical splint simulation, space
maintainers, retention devices etc

Spot welding may be used as method of fusing
• Stainless steel strip for making bands.
• Securing attachments to the bands
• Attaching springs to a rigid bow wire, or to
bands.
• It is used more in the construction of fixed
appliances

References
• Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental
Materials, ed 11, Chapter 33 Gold Alloy Solders, Soldering
Procedure, Page 563,564.
• William J. O’Brien(2002). Dental materials and their selection, ed
3, chapter 18, soldering, welding and electroplating. Page 249.
• SH Sorature (2002). Essentials of dental materials, ed 1, chapter
25, Soldering and welding, page 315.
• B.W.DARVELL (2001). Materials Science For Dentistry, Chapter
22 soldering and welding, 9th edition, page 486.

solderingwelding-171217173136-converted.pptx

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