Soldering and welding are processes to join metal components. Soldering involves melting a filler metal below the melting points of the components being joined. Welding directly melts the components together without a filler. Common types of soldering include soft, hard, and brazing based on the filler metal temperature. Welding techniques include spot welding, laser welding, and tungsten inert gas welding. Key factors for a strong joint include clean surfaces, proper temperature, timing, and gap width between components. Defects like porosity or distortion can weaken the joint if processes are not followed correctly.

1. WED
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Good morning

2. SOLDERING AND
WELDING
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3. • Common roles in the society?
• What u perceive with these words soldering &
welding?
• Any examples to it?
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4. CONTENTS
• DEFINITIONS
• IDEAL REQUIREMENTS OF A DENTAL SOLDER
• TYPES OF SOLDERING
• COMPONENTS OF SOLDERED JOINTS
• TECHNIQUE OF SOLDERING
• STEPS OF SOLDERING
• USES OF SOLDERING
• SOLDERING DEFECTS
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5. • WELDING
• TYPES OF WELDING
1. SPOT WELDING
2. PRESSURE WELDING
3. LASER WELDING
4. PLASMA ARC AND TUNGSTEN INERT
GAS WELDING
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6. • SOLDERING: 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.
• WELDING: Two pieces of similar metal are joined
together without the addition of another metal;
i.e., the metal pieces are heated to high enough
temperature so they join together by melting
and flowing.
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7. IDEAL REQUIREMENTS OF A DENTAL
SOLDER
• 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
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8. TYPES OF SOLDERING
1. Soft soldering- joining of two metals by a filler metal
having a very low melting temperature, usually
below 3500C. E.g.-lead-tin alloy as a filler; in
electronic industry
2. Hard soldering- joining of two metals by a filler metal
having a very low melting temperature, usually below
4500C; in dentistry
3. Brazing- joining of two metals by a filler metal having
a very low melting temperature, usually more than
4500C; in automobile indusry
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9. COMPONENTS OF SOLDERED JOINTS
Parent metal
Fluxes and anti- fluxes
Solder or filler metal
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10. PARENT METAL
• The parent metal is the metal or alloy to be joined.
• It is also known as substrate metal or base metal.
• Gold based, silver based, palladium based, nickel
based, cobalt based, pure titanium.- can be used as
parent metal.
• The composition of parent metal determines:
o melting range.
o oxide that forms on the surface during heating.
o wettability of the substrate by the molten solder.
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11. FLUX
• 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.
• Increases wettability and flow
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12. 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.
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SURFACE PROTECTION
TYPE
REDUCING AGENT TYPE
SOLVENT TYPE
TYPES OF FLUX
Covers the metal surface and prevents
access to oxygen so that oxides can
form
Reduces any oxides present and expose
clean metal
Dissolve any oxides present and carries
them away
1. ACCORDING TO THEIR PRIMARY PURPOSE / ACTIVITY

14. • TYPE I – protective fluxes by forming a low
temperature glass
• TYPE II – reducing fluxes for low stability
oxides such as copper oxides
• TYPE III – fluoride flux, usually contain
borates as glass formers
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2. ACCORDING TO THE BORIC OR BORATE COMPOUND:

15. 3. ACCORDING TO THE PH OF THE FLUX:
• Acidic fluxes – SiO2
• Basic fluxes – CaO, lime CaCO3 LIMESTONE
• Neutral – Fluoride flux (Ca.F2),Borax
• (Na2B4O2)
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16. The Flux may be used by:
• Painting it on surface of the substrate metal at
the junction of the pieces to be joined,
• Fusing onto the surface of the filler metal strip,
• Filler metal being in a tubular form and flux
inside the tube- prefluxed sloder
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17. 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 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.
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18. SOLDER OR FILLER METAL
• Sufficiently low flow temperature(i.e. lower
than the solidus temperature of the metal to be
joined- 55.60C)
• Ability to wet he substrate metal
• Sufficient fluidity at the flow temperature
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19. Soft Solders-
• They have low melting range about 260°c. they can be
applied by simple means like hot soldering.
• Less corrosion resistant.
• E.g.- lead-tin alloys.
Hard Solders-
• They have a high melting range. (>260°).
• They are melted with gas blow torches, electric furnaces.
• Used in dentistry.
• E.g. - gold solder, silver solder, pre and post ceramic
solder.
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TYPES OF SOLDER

20. Gold solder
• Use for joining wrought and cast gold alloys.
• They are more corrosion resistant.
• Au-45-81%, Ag8-30%,Cu-7-20%,Sn-2-4%,Zn- 2-
4%. Fusion temperature- 690-870ºc
• Zn and Sn lower the melting point. Au imparts
corrosion resistance.
• Gold solders have been classified by fineness or
karat. Fineness refers to parts per thousand of
Au in a solder.
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21. Silver solder
• Mainly use for soldering of base metal alloys.
• Fusion temperature-620-700°c
• Au-10-80%, Cu-15-50%,zn-4-35%,Ca/P-1%.
Pre and Post ceramic solders
• Pre ceramic solders are used before ceramic
application and post ceramic solders are used after
ceramic application.
• Pt,Pd metals and Au impart corrosion resistance.
• Trace elements must be incorporated for porcelain
bonding
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22. TECHNIQUES OF SOLDERING
1. Free hand soldering-
Parts are held manually while heat and solder are
applied.
2. Invest soldering-
In investment soldering the parts to be joined are
mounted in a soldering type of investment. The
hardened investment holds it in position while the
heat and solder is applied.
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23. STEPS OF SOLDERING
1. Cleaning and preparing the surface to be joined.
• Clean soldering contact surfaces are a basic requirement
for optimum wetting.
• The surfaces of the soldering contact areas have to be
prepared by grinding and/or sand blasting.
• Evenly roughen the soldering contact surfaces in the
direction of flow of the solder using a suitable (ceramic-
bonded) grinding instrument.
• The soldering contact surfaces may also be blasted with
50 micron Al2O3.
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24. 2. Assembling the parts to be joined.
3. Preparing and fluxing the gap surface
4. Maintaining proper position of the parts during
procedure
• Optimum gap should be maintained.
• Gap width ranging .13-.3 mm.
• Narrow gap may cause incomplete flow, flux inclusion, porosity.
• Too wide gap may cause reduction of joint strength, parts to
draw together as solder solidifies.
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25. 5. Controlling the proper temperature and proper source of heat
• Different heat source-
• Heat transmission occur through 3 methods :
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26. Propane-
• Best choice as fuel gas.
• Flame temperature is 2850°C and heat content is 21221
kcal/m³.
• Uniform burning, water vapor free.
Acetylene –
• It has got the highest flame temperature (3140°C).
• But heat content of flame is less 12884kcal/m³
• Very difficult to use proper zone of flame because of variation
in flame temperature. 26

27. Natural gas –
• Flame temperature is 2680°c but heat content is higher than hydrogen gas. i. e
8898 kcal/m³
• Flame is not vapor free and the temperature is not uniform.
Hydrogen-
• low flame temperature 2660° c. heat content is also very low.2362kcal/m³.
• Not used in the soldering process of large bridges.
Laser soldering-
• High power diode laser is used.
• Lower heat input ,Low part distortion
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28. Microwave heating-
• Most recent technology.
• Microwave energy is used as energy source and to melt the alloy.
• Less energy is needed.
• Infrared heating-
• Production of thermal energy using an optical system of infrared
light capable of generating a maximum temperature of 1350 °C
• Accurate focus of thermal energy up to 1 cm diameter.
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29. TECHNIQUE CONSIDERATIONS FOR SOLDERING
• Flame
• Gap
• Temperature
• Time
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30. FLAME-
Can be divided into four zone:
1. Cold mixing zone
2. Partial combustion zone
3. Reducing zone
4. Oxidizing zone
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31. 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
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32. TEMPERATURE
• 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
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33. 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
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34. USES OF SOLDERING
• For joining components of fixed partial
denture.
• To overcome distortion in multiunit cast fixed
prostheses.
• To overcome firing distortion in metal–
ceramic FPDs..
• To repair perforation in crowns.
• To develop contact points in crowns.
• To solder clasps in removable partial dentures.
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35. SOLDERING DEFECTS
Porosity or pitting:
• It may occur during finishing and polishing due
to volatilization of lower melting components
as s result of higher temperature and longer
time causes-
• Incorrect fluxing
• Incorrect flaming
• Incorrect cleaning
• Incorrect spacing of parts
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36. Distortion of parts being soldered.
• causes-
• Overheating
• Thermal expansion of the metal parts
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37. WELDING
• 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.
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38. TYPES OF WELDING
• Cold welding/Pressure welding is done by
hammering or Pressure. Two layers of gold foil
are joined by application of pressure at room
temperature. No heat is used.
• 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.
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39. • 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
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40. • Weld joints are not corrosion resistant
because of precipitation of carbide thus,
leading to loss of passivating layer
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41. STEPS OF SPOT WELDING
• Clean the parts
• Check that the surface of the electrodes are
smooth, flat and perpendicular, should be in
even contact with each other.
• Adjust welder settings as recommended by the
manufacturer.
• Select the proper electrode (low resistance,
broader electrode for thin metal and vice
versa).
• Switch on the current
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42. 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 than removable appliances.
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43. • Laser welding produces a keyhole that
concentrates the energy absorbed in a small
region, resulting in high penetration and
formation of a narrow heat affected zone
(HAZ) that results in less distortion. E.g.-
titanium alloy welding using Nd:YAG laser.
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44. Light beam reaches the metal surface
Metal absorbs energy
Convert it into heat the penetrates inside
Formation of heat spots in the form of key hole that
fills with metal
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Roberto von Krammer K.,Cirujano-Dentista;Artificial Occlusal Surfaces;JPD oct 1971

45. • Plasma Arc Welding
Plasma is ionized gas at very high temperatures. The
plasma is generated by sending a jet of gas through
an electric arc. Plasma welding is only done with
automatic machines.
• Tungsten Inert Gas Welding
The electrode and the area to be welded are
protected by using an inert gas, usually argon or a
mixture of inert gases (argon and helium).
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46. Generates a complex region of stresses and
deformations in the welded region.
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47. FAILURE IN WELDING
• If the weld mates are not clean, impurities such
as grease, saliva and cement can weaken the
joint.
• Improper selection of electrode
• If electrodes are not clean, joint can fail
• If electrodes do not touch each other evenly,
there can be sparking band localized over
welding. This can weaken the joint
• Pressure not appropriate
• If heat generation is not optimum.
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