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Soldering & welding

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Soldering and welding .... this topic include what exactly is soldering and welding and its application in routine dental practice....

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Presented by, Dr Sumit Rajewar BDS, MDS (Pedodontics And Preventive Dentistry)
CONTENT: 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
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
Soldering & welding
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属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属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 & welding
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
Soldering & welding
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: 1. According to their primary purpose / activity a. Surface protection type b. Reducing agent type c. Solvent type
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
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
They are available in 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. Paste form: Formed by mixing borax with petroleum jelly. Required when fluxes are needed in large quantity. 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.
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.
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 super flux is Borax glass 55 parts Boric acid 35 parts Silica - 10 parts
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 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 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属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.
A) CLASSIFICATION OF SOLDERS 1. Soft solders & Hard solders SOFT SOLDERS: They have low melting range of about 260属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 24 wt % Zinc 24 wt % They are high fusing with a fusion temperature range of 750- 900属 C
Silver Solder Silver solders Used in orthodontic appliances They have low fusion temp-600-750属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%
Soldering & welding
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
Soldering & welding
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.
Soldering & welding
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
Soldering & welding
Flame Gap Temperature Time
FLAME The flame can be divided in to four zones Cold mixing zone (unburned gas) Partial combustion zone (oxidizing) Reducing zone
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.
Soldering & welding
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
Soldering & welding
Wire to wire. Tube can be soldered to the bridge of the Adams clasp. Attachment of springs to arch wire, Soldering lingual arch or palatal arch. Soldering of various type of space management appliances.
Soldering & 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.
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
References Kenneth J. Anusavice(2004). PHILLIPS Science Of Dental Materials, ed 11, Chapter 33 Gold Alloy Solders, Soldering Procedure, Page 563,564. William J. OBrien(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.
Soldering & welding

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Soldering & welding

  • 1. Presented by, Dr Sumit Rajewar BDS, MDS (Pedodontics And Preventive Dentistry)
  • 2. CONTENT: 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
  • 3. 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
  • 5. 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属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属C. .
  • 6. 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
  • 8. 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
  • 10. 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
  • 11. 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
  • 12. 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.
  • 13. 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.
  • 14. A) CLASSIFICATION OF FLUX: 1. According to their primary purpose / activity a. Surface protection type b. Reducing agent type c. Solvent type
  • 15. 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)
  • 16. 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
  • 17. 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
  • 18. They are available in 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. Paste form: Formed by mixing borax with petroleum jelly. Required when fluxes are needed in large quantity. 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.
  • 19. FLUORIDE FLUXES Composition:- Potassium fluoride 50-60% Boric acid 25-35% Borax glass - 6-8% Potassium carbonate 8-10%
  • 20. 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.
  • 21. 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 super flux is Borax glass 55 parts Boric acid 35 parts Silica - 10 parts
  • 22. 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 metal. It should be easily removable after soldering.
  • 23. 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.
  • 24. 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.
  • 25. 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.
  • 26. Desirable properties of dental solders: The fusion temperature must be at least 50- 100属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.
  • 27. 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.
  • 28. A) CLASSIFICATION OF SOLDERS 1. Soft solders & Hard solders SOFT SOLDERS: They have low melting range of about 260属C Soft solders lack corrosion resistance, so they are not suitable for dental use. Eg. lead- tin eutectic alloy (plumbers solder).
  • 29. 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.
  • 30. 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 24 wt % Zinc 24 wt % They are high fusing with a fusion temperature range of 750- 900属 C
  • 31. Silver Solder Silver solders Used in orthodontic appliances They have low fusion temp-600-750属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%
  • 33. 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
  • 34. 2) Natural gas: Temperature of 2680*C 4 times that of hydrogen Available in non uniform in composition
  • 35. 3) Acetylene: Highest flame temperature (3140*C) Higher heat content than hydrogen and natural gas Chemically unstable and decomposes readily into carbon and hydrogen.
  • 36. 4) Propane: Highest heat content (2385*C) Having good flame temperature (2850*C) Best choice
  • 38. 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.
  • 39. 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.
  • 41. 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.
  • 42. 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
  • 43. 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.
  • 44. 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.
  • 45. 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
  • 47. Flame Gap Temperature Time
  • 48. FLAME The flame can be divided in to four zones Cold mixing zone (unburned gas) Partial combustion zone (oxidizing) Reducing zone
  • 49. 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
  • 50. 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
  • 51. 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
  • 52. 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
  • 53. 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.
  • 55. 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
  • 56. 2. Distortion of parts being soldered. causes- Overheating Thermal expansion of the metal parts
  • 58. Wire to wire. Tube can be soldered to the bridge of the Adams clasp. Attachment of springs to arch wire, Soldering lingual arch or palatal arch. Soldering of various type of space management appliances.
  • 60. 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.
  • 61. 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.
  • 62. 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
  • 63. SPOT WELDING PRESSURE WELDING LASER WELDING LASER micro WELDING
  • 64. 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.
  • 65. 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.
  • 66. 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.
  • 67. 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
  • 68. 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
  • 69. References Kenneth J. Anusavice(2004). PHILLIPS Science Of Dental Materials, ed 11, Chapter 33 Gold Alloy Solders, Soldering Procedure, Page 563,564. William J. OBrien(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.