Soldering

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  • In pedodontics soldering is used for joining wires, bands springs etc. All are equally important and the role of each must be taken in to consideration to solder metal components successful.
  • Whatever is the technique used the most important thing to be considered is the amount of flux to be used.Too little of flux burns off and tends to be ineffective.Excess flux remains trapped in the filler metal and weakens the joint.Flux combined with metal oxide forms glass that is difficult to remove complete
  • Pitting/porosity
  • Fusion temp.
  • The formation of silver-copper eutectic is responsible for the low melting range of silver solder
  • The parts are placed on the master cast with a gap of at least 1mm. The parts are fastened with sticky wax before placing soldering investment. Anti flux is applied to confine the flow of solder. The investment is preheated to eliminate moisture. Flux can be applied before or after heat treatment. Soldering is carried out with reducing flame at 750- 870°C. The investment is cooled 5 min before quenching. Flux will cool to a glass which is removed by pickling
  • Steps- The wires to be joined are thoroughly cleaned and polished.Apply fluxSmall amount of solder placed over them.Hold the wires in reducing zone of the flame until solder flow quickly.Remove and quench.
  • It is important not to introduce carbon of flame to the metals and alsoMetal must not be oxidized during the procedure.Therefore it is important to adjust the flame to the reducing zone which is blue colored,hottest part of flame and without carbon in it.Therefore it shud be used to melt the solder.
  • Soldering

    1. 1. SOLDERING & WELDING Presentation By: Garima singh MDS 1st yr 1
    2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 26. Methods Of Soldering I. Investment soldering II. Free hand soldering III. Jig soldering 26
    27. 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. 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. 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. 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. 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. 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. 32 Fracture of the joint- due to overheating Actual solution of parts- due to overheating
    33. 33. 2. Distortion of parts being soldered. causes Overheating  Thermal expansion of the metal parts 33
    34. 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. 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. 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. 37. TYPES OF WELDING • SPOT WELDING • PRESSURE WELDING • LASER WELDING • PLASMA WELDING 37
    38. 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. 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. 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. 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. 42. Thank you

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