Dental Soldering Flashcards
What is soldering?
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 degree Celsius.
What is brazing?
It is a procedure in which 2 metals are joined by the fusion of a filler metal between them at a temperature below the solidus temperature of metals being joined and above 450 degree Celsius.
What is liquidus temperature?
It is the temperature at which metals of an alloy begin to solidify on cooling or become totally liquid on heating.
What is solidus temperature?
It is the temperature at which metals of an alloy become completely solidified on cooling or start to melt on heating.
What is welding?
The joining of two or more metal parts by applying heat, pressure or both, with or without a filler metal, to produce localised union across the interface through fusion or diffusion.
Components of soldered joint?
- Parent metal
- Solder filler metal
- Flux
- Anti flux
- Heat source
Application of soldering?
- Inlays
- Crowns
- Fixed bridge work
- Removable partial denture
- Orthodontics appliances
What is parent metal?
The parent metal is the metal or alloy to be joined.
Parent metal is also know as….. and….
Base metal
Substrate metal
The composition of parent metal determines…..(4)
- melting range
- oxide that forms on the surface during heating
- Wettability of the substrate by the molten solder.
What kind of soldering is preferred for stainless steel wire?why?
A low temperature soldering is preferred to prevent carbide precipitation and to prevent an excessive softening of the wire. So silver solders are generally preferred.
What is solder metal?
Alloy of two or more metals used to joined other metal together.
Principle of attachment of solder metal to parent metal…
Capillary action.
Strength of solder joint depends on…
Filler metal used
Requirement of a good solder (7)
- Melting point should be below that of metals to be soldered.
- Strength and hardness should be as near as that of metal to be soldered.
- Melt and flow freely
- Ability to flow the substrate
- Resistance to tarnish & corrosion
- Acceptable colour
- Resistance to pitting during heating.
Classification of solders?
- BASED ON MELTING RANGE
A. Soft solders
B. Hard solders
C. Very hard solder/ brazing solders
- BASED ON TYPES OF METALS
A. Precious metal solders
B. Non precious metal solders
Melting temperature of soft solders?
- Very low-below 260 degree Celsius
What king of alloy used in soft solder and in what proportion?
Lead tin alloy in 40:60 ratio
Heat source of soft solders
Electric gun/ iron
Advantage of soft solder?
Good strength
Disadvantage of soft solder?
Poor corrosion resistance.
Is soft solder used in dentistry?
No
Advantages of hard solder(3)
- High hardness and strength
2. Good corrosion resistance
Melting point of hard solder?
High
Hard solder is used in?
Joins broken gold alloys
Disadvantage of hard solder? (2)
- High cost
2. High softening temperature
Example of hard solder?
- Gold & silver solder
Composition of gold solder?
Gold :45-81%
Silver : 8-30%
Copper : 7-20%
Sn, zn, p : trace
Composition of silver solders?
Silver : 40-65 % Copper : 15-30% Zinc : 15-20 % Cadmium :17-24 % Tin : 1-3 %
What is flux?
It is a reducing agent applied to metal surfaces to be joined to prevent formation of oxides which may reduced the strength of soldered area.
How amount of flux is important?
Little- burn off
Excess- remain trapped in filler metal alloy which makes weak weak joint.
What is the function of flux?
- Eliminates impurities like dirt,oxides at the joint which reduce strength of soldered part.
- acts as reducing agent by preventing reoxidation
- act as wetting. Agent and reduce surface tension
Classification of flux 4
- Based on their main purpose
- surface protection : prevents access to oxygen so that no oxides can form
- reducing agent : reduce oxide presents and exposes clean metal
- solvent : dissolves oxides - Based on their pH
- acidic flux : silicone dioxide
- basic flux : calcium oxide, calcium carbonate
- neutral flux : borax, fluorspar - Based on their sources
- organic : Rosin fluxes( used in soft soldering procedure that require low temperature)
- inorganic flux : halogenides acid fluxes( used in brazing procedure that require high temperature ) - Based on their composition
- borax flux
- fluoride flux
Example of acid flux
Silicone dioxide
Example of basic flux
Calcium oxide
Calcium carbonate
Example of neutral flux
Borax
Fluorspar
Rosin flux used in?
Soft soldering procedurethat require low temperature
Halogenides acid flux used in?
Brazing procedure that require high temperature
Borax flux characteristics 3?
- noble metal alloy
- based on boric or borate compound
- act as protective and reducing fluxes
Characteristics of fluoride flux?
- used for base metal alloy
- more stable
Requirement for a flux
- flow easily
- it should melt easily
- it should be able to wet the metal and the solder surface to form an intimate contact between the two.
- It should not have effervescent or bubble
- it should be able to remove the undesirable oxides and impurities presents on the surface
What is antiflux?
The material used to restrict the flow of melted solder into unwanted areas.
How to apply anti flux
-applied before applying flux/ solder
Example of anti flux
- lead oxide for soft solder
- paste of iron oxide or calcium carbonate in alcohol for hard solder
Heat sources
- Flame from gas torch
- High frequency of AC current
- Laser
- Infrared sources
5 hydrogen and oxygen combustion.
Types of flame from gas torch 4
- H2+O2 mixture : has low heat content
- Natural gas : gives more heat than above but not sufficient
- Acetylene : highest flame temperature but chemical unstable. It can deposits on Ni-Pd alloys
- Propane : good flame temperature ; burns clean ; easily available ; best choices
High frequency AC Current characters 2
- Electrosoldering method done using spot welder
2. Current is passed through electrode and temperature is generated at the carbon tip of the electrode.
What is the wavelength used in laser to melt and joined metals?
800-900 nm
What are the infrared sources?
Infrared sources are LED through fibresand focused into a single spot which has to be soldered.
Characteristics of hydrogen and oxygen combustion. 4
- Hydroflame soldering unit
- uses electrolytic process to make hydrogen and oxygen from distilled water.
- has flame temperature of 2000 degree Celsius , no separate fuel requirement
- expensive method-not used commonly
Methods of soldering
- Free hand soldering (jig soldering)
- Investment soldering - investing or assembling the parts on a cast. Plane gas can be used for soldering provided it can be made into a fine jet. Air jet can be added.
- Infrared soldering
- Soldering can also be done by carbon electrode by using ordinary welder.
What is the best method and easiest method of soldering?
Flame
Uses of investment soldering?
For precise arrangements of parts for bridge work of partial denture.
Steps of investment soldering?
- Soldering parts are assembles with sticky wax.
- It is then kept in investment mix
- Sticky wax flushed by boiling water.
- Then flux is applied.
- Solder is applied and melted with a flame.
- Quenched in water
Methods of free hand soldering?
Here parts to be assembled are held either by soldering jig or by hand . Then same procedure
Uses of free hand soldering
Generally used in orthodontics
Steps in soldering ?
- Cleaning and assembling the surface to be. Joined.
- Maintenance of proper gap between the surfaces to be soldered.
- Applying suitable flux and Solder to be joined.
- Applying heat to part that has to be joined.- gas torch can be used
- Temperature of heat source must be Controlled
- Controll of time during heating is important
- Cleaning and polishing of the joint.
What happen if too high temperature?
Carbide ppt
What happens in too low temp?
Filler material will not flow.
