1. SOLDERING
&
WELDING
Presentation By:
Garima singh
MDS 1st yr
1

2. CONTENT
•
Definitions
•
Soldering
•
Parent metal
•
Flux
 Classification of flux
 Ideal properties of flux
•
Anti-flux
•
Solder
 Flow temperature
 Classification of solder
•
2
Heat source

3. •
General principles for soldering
•
Methods of soldering
 Investment soldering
 Free-hand soldering
•
Technique consideration for soldering
•
Soldering defects
•
Welding
•
Types of welding
 Spot welding
 Pressure welding
 Laser welding
 Plasma welding
3
•
References

4. DEFINITIONS
• 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 joining of metals by the fusion
of filler metal between them, at a temperature below
the solidus temperature of metals being joined and
above 450° C.
4
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33 Gold Alloy
Solders, Soldering Procedure, Page 563,564

5. • WELDING Process of fusing of two or more metal
parts through the application of heat, pressure, or
both, without a filler metal, to produce a localized
union across an interface between the parts.
5
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33, Dental casting and
soldering alloy, Page 563,564.

6. SOLDERING
• Soldering is often used in construction of dental
appliances .
• Components of solder joint:
1. Parent metal
2. Flux
3. Solder/filler metal
6
William J. O’Brien(2002). Dental materials and their selection, ed 3, chapter 18, soldering, welding and
electroplating. Page 249

7. 1.PARENT 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 substrate metal.
The composition of parent metal determines:
• melting range
• oxide that forms on the surface during heating
• wettability of the substrate by the molten solder.
7

8. 2.FLUX
• FLUX In Latin flux means “to flow” .
• Purpose of flux is to remove any oxide coating on the
substrate metal surface when the filler metal is fluid and
ready to flow into place.
• They protect the alloy surface from oxidation during
soldering and dissolve metallic oxides as they are
formed. The resulting solution of oxides or other
extraneous matter in flux constitutes “slag”.
8
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33 Gold Alloy
Solders, Soldering Procedure, Page 609

9. CLASSIFICATION OF FLUX
1. According to their primary purpose / activity
a. Surface protection type
b. Reducing agent type
c. Solvent type
9
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33 Gold Alloy Solders,
Soldering Procedure, Page 609

10. 2. According to the pH of the flux:
a.
Acidic fluxes – SiO2
b.
Basic fluxes – CaO, lime CaCO3 LIMESTONE
c.
Neutral – Fluorspar (Ca.F2),Borax (Na2B4O2)
3. Based on boric or borate compound:
a.
TYPE I – protective fluxes by forming a lowtemperature glass
b. TYPE II – reducing fluxes for low stability oxides such
as copper oxides
c. TYPE III – fluoride flux
10

11. BORAX FLUXES
• They are based on boric or borate compounds such
as boric acid/boric anhydrate and borax. It is usually a
white powder consisting of soft colourless crystals that
dissolve easily in water.
• They act as protective fluxes and reducing fluxes for
low stability oxides such as copper oxide and are used
for noble metal alloys.
11

12. • They are available in
a. Liquid form : Solution of borax/boric acid in water.
Indicated for soldering of orthodontic appliances and
bridges in which minimum amount of flux is required.
b. Paste form : Formed by mixing borax with petroleum jelly.
Required when fluxes are needed in large quantity.
c. Powder form : Contains a mixture of borax, basic
acid, silica and finely divided charcoal. Charcoal is
reducing agent and silica holds molten flux in surface of
hot metal. This is usually used for casting operation.
12

13. FLUORIDE FLUXES
•
Composition:- Potassium fluoride – 50-60%
Boric acid – 25-35%
Borax glass - 6-8%
Potassium carbonate – 8-10%
• The fluoride flux is used with alloys containing base metals
even if a gold/silver solder is used. Some fluoride containing
fluxes involve toxic fluorides when heated, so inhalation of
fumes should be avoided.
13

14. SUPER FLUX
• A combination of high melting salts is used as fluxes to
combine the good characteristics of each ingredient and
create superior flux.
•
A formula for efficient flux is
Borax glass – 55 parts
Boric acid – 35 parts
Silica - 10 parts
• The ingredients may be fused together and then
crushed to fine powder.
14

15. 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 metal.
• It should be easily removable after soldering.
15
SH Sorature (2002). Essentials of dental materials, ed 1, chapter 25, Soldering and welding, page 315

16. APPLICATION OF FLUX
1. Painted on the substrate metal at the junction of pieces
to be joined.
2. It may be Fused onto the surface of the parent metal
strip.
16
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33 Gold Alloy
Solders, Soldering Procedure, Page 609

17. ANTI-FLUX
• ANTI FLUX Materials used to restrict flow of solder are
known as anti flux.
• It is applied on the surface of specific area where the
solder should 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.
17
SH Sorature (2002). Essentials of dental materials, ed 1, chapter 25, Soldering and welding, page 315

18. 3.SOLDER/ FILLER METAL
Desirable properties of dental solders:
 The fusion temperature must be at least 50-100°C 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. Fluidity and 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.
18
E.C. Combe (1992). Notes on dental materials, ed 6, chapter 46, soldering and welding, page 204

19. Flow Temperature
• Temperature at which filler metal wets and flow on
substrate and produce a bond .It is usually higher
than its liquidus temperature.
• Flow temperature of filler metal should be lower
than solidus temperature of metal being joined.
• A rule of thumb is that flow temperature of the filler
metal should be 56°C (100°F) lower than the
solidus temperature of the substrate metal.
19
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33, Dental casting and
soldering alloy, Page 610

20. CLASSIFICATION OF SOLDERS
a. Soft solders & Hard solders
• SOFT SOLDERS They are lead- tin eutectic alloy with a
low melting point. Sometimes called as plumbers solder.
They have low fusion range of about 260°C or less. Soft
solders lack corrosion resistance, so they are impractical
for dental use.
• HARD SOLDERS Hard solders have higher meting
temperature & possess greater hardness and strength.
Heating is done with gas torch or special devices. Two
types of hard solders are used in dentistry: gold solder &
silver solder.
b. Precious metal solders & Non precious metal solders
20

21. 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 %
with small amounts of Tin, Zinc and Phosphorus to
modify fusion temperature and flow qualities. They are
high fusing with a fusion temperature range of 750- 900° C
21

22. 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%
with small amounts of cadmium, tin and phosphorus.
22

23. HEAT SOURCE
• HEAT SOURCE The most common instrument used as
heat source is gas- air or gas- oxygen torch.
• The type of torch depends on the type of fuel. The fuels
used are : Hydrogen -low heat content, so heating is slow.
 Natural gas - heat content is four times that of
hydrogen
 Acetylene
 propane.
23
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33, Dental casting and
soldering alloy, Page 612

24. General Principles Of Soldering
Procedure
• 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.
24
SH Sorature (2002). Essentials of dental materials, ed 1, chapter 25, Soldering and welding, page 316

25. • 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.
25

26. Methods Of Soldering
I.
Investment soldering
II. Free hand soldering
III. Jig soldering
26

27. INVESTMENT SOLDERING
• INVESTMENT SOLDERING Used when very
accurate alignment of parts to be joined is
needed.
27
SH Sorature (2002). Essentials of dental materials, ed 1, chapter 25, Soldering and welding, page 317

28. FREE-HAND SOLDERING
• Free hand soldering is used for soldering
orthodontic appliances. Orthodontic torches can
be placed on a bench so that both hands can be
used to hold the parts in position.
SOLDERING BY USING
SOLDERING JIG
28
SH Sorature (2002). Essentials of dental materials, ed 1, chapter 25, Soldering and welding, page 316

29. Technique Consideration For Soldering
• Flame
• Gap
• Temperature
• Time
29
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33, Dental casting and
soldering alloy, Page 614

30. FLAME
The flame can be divided in to four zones
•
•
Partial combustion zone (oxidizing)
•
Reducing zone
•
30
Cold mixing zone (unburned gas)
Oxidizing zone (burned gas).
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental Materials, ed 11, Chapter 33, Dental casting and
soldering alloy, Page 615

31. HYDROSOLDER
• This machine converts Water
into oxy-hydrogen fuel for an
extremely hot and precise
reducing flame operating at
4850*F.
• This machine is perfect for
soldering and brazing in the
orthodontic laboratory
environment.
31

32. SOLDERING DEFECTS
1. Those affecting the structure of joint itself.
a. Porosity or pitting
causes incorrect fluxing
 Incorrect flaming
 Incorrect cleaning
 Incorrect spacing of parts
b.
c.
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Fracture of the joint- due to overheating
Actual solution of parts- due to overheating

33. 2. Distortion of parts being soldered.
causes Overheating
 Thermal expansion of the metal parts
33

34. Soldering Applications In Pedodontics
• 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.
34

35. WELDING
• WELDING is the process by which the surfaces of
metals are joined by mixing, with or without the use of
heat.
1.
2.
35
Cold welding is done by hammering or pressure.
An example of cold welding is the gold foil filling.
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.

36. Methods of welding
• Basically two methods are followed:
1. Fusion welding: where the parts are melted and
joined, but pressure is not applied.
Eg: Gas welding, Laser welding
2. Pressure welding: where parts are heated and
pressed , but not melted.
Eg: Spot welding
36

37. TYPES OF WELDING
• SPOT WELDING
• PRESSURE WELDING
• LASER WELDING
• PLASMA WELDING
37

38. • Spot welding: The two clean metal surfaces to be
welded are placed together under pressure.
• Pressure welding: If two metal parts are placed
together and a sufficiently large force is applied
perpendicular to surface , pressure welding occurs.
• Laser welding: Laser generates a coherent, highintensity pulse of light that can be focused.
38

39. Application of Spot welding
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.
•
39
It is used more in the construction of fixed
appliances than removable appliances.

40. CONCLUSION
•
•
Both soldering and welding can cause a
deterioration in properties if the wire is overheated
or under heated.
•
40
The choice of soldering materials has extreme
importance in determining the properties of the
soldered joints.
In the final analysis, however the combination of
techniques which offer optimum mechanical,
physical and chemical properties or offer desired
properties which are most favourable must be
selected.

41. References
•
•
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.
•
41
Kenneth J. Anusavice(2004). PHILLIP’S Science Of Dental
Materials, ed 11, Chapter 33 Gold Alloy Solders, Soldering
Procedure, Page 563,564.
B.W.DARVELL (2001). Materials Science For
Dentistry, Chapter 22 soldering and welding, 9th edition, page
486.

42. Thank you