Soldering And Welding
- Soldering: Soldering is a process in which two or more metals are joined together by melting and flowing a filler metal (solder) into the joint.
- Welding: Welding is the process by which two pieces of similar metals are joined together without the addition of another metal.
Laser welding
- Laser welding is a recent advancement in the welding procedures.
- In laser welding, the laser used is a pulsed neodymium laser with a very high power density.
- The laser unit consists of a small box that contains the laser tip, an argon gas source, and a stereo microscope with lens crosshairs for the correct alignment of the laser beam with the components.
- The maximum depth the laser can penetrate is 2.5 mm.
- The heat generated is small, so the parts can be hand-held during welding and it can be done close to the ceramic or even resin facings without damaging it.
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Indications Of Laser Welding
- Laser welding is used mainly to join titanium components.
- This is because the commercially pure titanium (cpi) used in dentistry for fixed and removable partial denture frameworks is highly reactive in the air.
- Ordinary soldering procedures result in a weak joint because of the formation of a thick layer of titanium oxide (especially when heated above 850°C).
- Laser welding or plasma welding can be done at lower temperatures.
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Mechanism Of Laser Welding
- When the light beam reaches the surface of the metal, the metal absorbs its energy, converting it into heat that penetrates into the interior of the metal by conduction.
- Owing to a high concentration of heat, the metal is taken to its melting point, and a series of events culminates in the formation of a keyhole or spots that will be filled with the melted metal.
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Advantages Of Laser Welding
- Lower heat generation.
- Laser welding can be executed directly in the working model.
- Allows welding in regions near the resins and porcelain portions without fear of damage to these materials.
- No oxide formation because of the inert argon atmosphere.
- Joints made of the same pure titanium as the components, thus reducing the risk of galvanic corrosion.
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- 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 compared to conventional welding methods.
- Less time expended.
- Allows welding with the structures in close contact or with minimal space for bragging using filer metal
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Disadvantages Of Laser welding
- Residual stress introduced into welding joints is a consequence of the heating and cooling cycles of the welding process. This affects the mechanical behavior of laser—welded structures.
- Argon gas can cause porosities which can lead to the failure of welded structures.
- Insufficient penetration of the laser beam can cause a big defect or internal failure if the equipment is not adjusted properly.
- High cost of the equipment.
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