2. AN INTRODUCTION SOLID STATE WELDING: Produces fusion of materials to be joined at temperatures much below the melting point of the base materials without the addition of a brazing filler metal. Joining takes place without fusion at interface. No liquid or molten phase is present at the joint. Two surfaces are brought together under pressure. Bonding of the materials is a result of diffusion of their interface atoms. For bonding, both surfaces must be clean. - no oxide films - no residues - no metal working fluids - no adsorbed layers of gas. SOLID STATE WELDING: Produces fusion of materials to be joined at temperatures much below the melting point of the base materials without the addition of a brazing filler metal. Joining takes place without fusion at interface. No liquid or molten phase is present at the joint. Two surfaces are brought together under pressure. Bonding of the materials is a result of diffusion of their interface atoms. For bonding, both surfaces must be clean. - no oxide films - no residues - no metal working fluids - no adsorbed layers of gas.

3. Solid State Bonding – A View

4. PROS & CONS Advantages :  Weld (bonding) is free from microstructure defects (pores, non-metallic inclusions, segregation of alloying elements)  Mechanical properties of the weld are similar to those of the parent metals.  No consumable materials (filler material, fluxes, shielding gases) are required.  Dissimilar metals may be joined (steel - aluminum alloy, steel - copper alloy). Disadvantages:  Thorough surface preparation is required (degreasing, oxides removal, brushing/sanding)  Expensive equipment.

5. MEMBERS OF SOLID STATE WELDING

8. Schematic illustration of the roll bonding or cladding Process.

10. A SUMMARY A SUMMARY The process is used for joining refractory metals at temperatures that do not affect their metallurgical properties. Heating is usually accomplished by induction, resistance, or furnace. Atmosphere and vacuum furnaces are used and for most refractory metals, a protective inert atmosphere is desirable. Process is versatile and reliable. Used with wide variety of metallic & non-Used with wide variety of non-metallic materials(Including dissimilar metals (bimetallic strips)). In order to keep the bonded surfaces clean from oxides and other air contaminations, the process is often conducted in vacuum. No appreciable deformation of the work pieces occurs. Diffusion Welding is used in aerospace and rocketry industries, electronics, nuclear applications, manufacturing composite materials.

11. STRENGTH OF BOND DEPENDS ON: – Pressure. – Temperature. – Time (duration) of contact. – Cleanliness of faying surfaces.  Bonding may be facilitated by use of a filler metal at the interface.  For some materials, brittle intermetallic compounds may form at interface (prevented by electroplating the surfaces).

12. The sequence of operations in the fabrication of a structure by the diffusion bonding and super plastic forming of three originally flat sheets See also Fig 16 48 Sources: (a) After D Stephenoriginally flat sheets. See also Fig. 16.48. Sources: (a) After D. Stephen and S.J. Swadling. (b) and (c) Courtesy of Rockwell International Corp.

13. Advantages:  Dissimilar materials may be welded (Metals, Ceramics, Graphite, glass).  Welds of high quality are obtained (no pores, inclusions, chemical segregation, distortions).  No limitation in the work pieces thickness. Disadvantages:  Time consuming process with low productivity.  Very thorough surface preparation is required prior to welding process.  The mating surfaces must be precisely fitted to each other.  Relatively high initial investments in equipment.

15. A GENERAL VIEW Welded parts (plates) are metallurgically bonded as a result of oblique impact pressure exerted on them by a controlled detonation of an explosive charge. Even though heat is not applied in making an explosion weld, it appears that the metal at the interface is molten during welding. This heat comes from several sources, from the shock wave associated with impact and from the energy expended in collision. Plastic interaction between the metal surfaces is especially pronounced when surface jetting occurs. It is found necessary to allow the metal to flow plastically in order to provide a quality weld. Welded parts (plates) are metallurgically bonded as a result of oblique impact pressure exerted on them by a controlled detonation of an explosive charge. Even though heat is not applied in making an explosion weld, it appears that the metal at the interface is molten during welding. This heat comes from several sources, from the shock wave associated with impact and from the energy expended in collision. Plastic interaction between the metal surfaces is especially pronounced when surface jetting occurs. It is found necessary to allow the metal to flow plastically in order to provide a quality weld.

16. PROCESS SUMMARY

17. Schematic illustration of the explosion-welding process: (a) constant- interface clearance gap and (b) angular-interface Clearance gap. (c) Cross section of explosion-welded joint: titanium (top) and low-carbon steel (bottom). (d) Iron–nickel alloy (top) and low-carbon steel (bottom).

18. PROS & CONS Advantages:  Large surfaces may be welded.  High quality bonding: high strength, no distortions, no porosity, no change of the metal microstructure.  Low cost and simple process.  Surface preparation is not required.  The weld apparently does not disturb the effects of cold work or other forms of mechanical or thermal treatment. Disadvantages:  Brittle materials (low ductility and low impact toughness) cannot be processed.  Only simple shape parts may be bonded: plates, cylinders.  Thickness of flyer plate is limited - less than 2.5” (63 mm).  Safety and security aspects of storage and using explosives.

20. A SUMMARY Low carbon steel parts are heated to about 1800°F (1000°C) and then forged (hammered). It is a solid-phase bonding technique that uses heat and pressure to make the weld. Prior to forge welding, the parts are scarfed in order to prevent entrapment of oxides in the joint. This is one of the older welding processes and at one time was called hammer welding. Forge Welding is used in general blacksmith shops and for manufacturing metal art pieces and welded tubes. There are mainly three types of forge welding method is used - Hammer welding - Roll welding - Die welding. If weld joint is made correctly, then it posses very good quality of joint. The strength of the joint is same as base metals. Low carbon steel parts are heated to about 1800°F (1000°C) and then forged (hammered). It is a solid-phase bonding technique that uses heat and pressure to make the weld. Prior to forge welding, the parts are scarfed in order to prevent entrapment of oxides in the joint. This is one of the older welding processes and at one time was called hammer welding. Forge Welding is used in general blacksmith shops and for manufacturing metal art pieces and welded tubes. There are mainly three types of forge welding method is used - Hammer welding - Roll welding - Die welding. If weld joint is made correctly, then it posses very good quality of joint. The strength of the joint is same as base metals.

21. HOW IT IS DONE?

22. PROS & CONS Advantages:  Good quality weld may be obtained.  Parts of intricate shape may be welded.  No filler material is required. Disadvantages:  Only low carbon steel may be welded.  High level of the operators skill is required.  Slow welding process.  Weld may be contaminated by the coke used in heating furnace. Advantages:  Good quality weld may be obtained.  Parts of intricate shape may be welded.  No filler material is required. Disadvantages:  Only low carbon steel may be welded.  High level of the operators skill is required.  Slow welding process.  Weld may be contaminated by the coke used in heating furnace.

24. It is a set of processes that generates heat through mechanical friction between a moving work piece and a stationary component, with the addition of a lateral force called "upset" to plastically displace and fuse the materials. Weld joint is made by heating is created from mechanically induced sliding motion between rubbing surface in under pressure. The heat is generated by co-efficient of friction of the material. To get a quick heat from surface area, when the rotational speed is high. Friction welding is used with metals and thermoplastics in a wide variety of aviation and automotive applications. Classified as i] 1) spin welding or inertia friction welding. 2) linear friction welding. ii] Friction stir welding. It is a set of processes that generates heat through mechanical friction between a moving work piece and a stationary component, with the addition of a lateral force called "upset" to plastically displace and fuse the materials. Weld joint is made by heating is created from mechanically induced sliding motion between rubbing surface in under pressure. The heat is generated by co-efficient of friction of the material. To get a quick heat from surface area, when the rotational speed is high. Friction welding is used with metals and thermoplastics in a wide variety of aviation and automotive applications. Classified as i] 1) spin welding or inertia friction welding. 2) linear friction welding. ii] Friction stir welding.

25. SPIN WELDING PROCESS SUMMARY

26. Shape of the fusion zones in friction welding as a function of the axial force applied and the rotational speed function of the axial force applied and the rotational speed.

27. LINEAR FRICTION WELDING  Linear friction welding is similar to spin welding except that the moving chuck oscillates laterally instead of spinning.  The speeds are much lower in general, which requires the pieces to be kept under pressure at all times.  This also requires the parts to have a high shear strength.  Linear friction welding requires more complex machinery than spin welding, but has the advantage that parts of any shape can be joined, as opposed to parts with a circular meeting point.

29.  A constantly rotated cylindrical-shouldered tool with a profiled nib is traversely fed at a constant rate into a butt joint between two clamped pieces of butted material.  The nib is slightly shorter than the weld depth required, with the tool shoulder riding atop the work surface.  Frictional heat is generated between the wear- resistant welding components and the work pieces.  This heat, along with that generated by the mechanical mixing process and the adiabatic heat within the material, cause the stirred materials to soften without melting.  As the pin is moved forward a special profile on its leading face forces plasticised material to the rear where clamping force assists in a forged consolidation the weld.  This process of the tool traversing along the weld line in a plasticised tubular shaft of metal results in severe solid state deformation involving dynamic recrystallization of the base material.  A constantly rotated cylindrical-shouldered tool with a profiled nib is traversely fed at a constant rate into a butt joint between two clamped pieces of butted material.  The nib is slightly shorter than the weld depth required, with the tool shoulder riding atop the work surface.  Frictional heat is generated between the wear- resistant welding components and the work pieces.  This heat, along with that generated by the mechanical mixing process and the adiabatic heat within the material, cause the stirred materials to soften without melting.  As the pin is moved forward a special profile on its leading face forces plasticised material to the rear where clamping force assists in a forged consolidation the weld.  This process of the tool traversing along the weld line in a plasticised tubular shaft of metal results in severe solid state deformation involving dynamic recrystallization of the base material. The principle of the friction- stir-welding process: Aluminum-alloy plates up to 75 mm (3 in.) thick have been welded by this process. The principle of the friction- stir-welding process: Aluminum-alloy plates up to 75 mm (3 in.) thick have been welded by this process.

30. PROS & CONS  Advantages: It requires less time operation. Operational hazardous is less. The characteristic changing of granular structure is less. The weld joint may have not heat treated again. It has no need of flux, filler. So it is free of smoke, spatter and slag. Simplicity of operation. Power requirement is less.  Disadvantages: Requires relatively expensive apparatus similar to a machine tool.  Advantages: It requires less time operation. Operational hazardous is less. The characteristic changing of granular structure is less. The weld joint may have not heat treated again. It has no need of flux, filler. So it is free of smoke, spatter and slag. Simplicity of operation. Power requirement is less.  Disadvantages: Requires relatively expensive apparatus similar to a machine tool.

32. Hot-pressure-welding is a solid state process that produces joints between the faying surfaces of two bodies, by application of heat and of pressure. Fusion temperature is not reached, filler metal is not needed but substantial plastic deformation is generated. The materials to be welded must exhibit hot ductility or forgeability. Mechanical properties tend to be near those of the base materials, but depend upon materials composition, cooling rate and quality. This type of operation is normally carried on in closed chambers where vacuum or a shielding medium may be used. Hot-pressure-welding can be an economic and successful process for performing butt joints of simple shapes if the materials are easily weldable. The materials commonly joined by Hot-pressure-welding are carbon, low alloy steels, and certain nonferrous metals. Certain dissimilar materials combinations are weldable by Hot-pressure- welding. Hot-pressure-welding is a solid state process that produces joints between the faying surfaces of two bodies, by application of heat and of pressure. Fusion temperature is not reached, filler metal is not needed but substantial plastic deformation is generated. The materials to be welded must exhibit hot ductility or forgeability. Mechanical properties tend to be near those of the base materials, but depend upon materials composition, cooling rate and quality. This type of operation is normally carried on in closed chambers where vacuum or a shielding medium may be used. Hot-pressure-welding can be an economic and successful process for performing butt joints of simple shapes if the materials are easily weldable. The materials commonly joined by Hot-pressure-welding are carbon, low alloy steels, and certain nonferrous metals. Certain dissimilar materials combinations are weldable by Hot-pressure- welding.

33. PROCESS SUMMARY Heat is generally applied by flames of oxyfuel torches directed on the surfaces to be joined. Upon reaching the correct temperature, the torches are suddenly removed, and the two bodies [solid bars or hollow sections] are brought to contact and upset together under pressure [hydraulic equipment]. This variant is properly called the open joint process. Alternatively, when the parts are making contact under pressure before heat application from the outside, also by electrical induction, it is called the closed joint process. In either case flash material is expelled and a bulge is formed at the joint. Hot-pressure-welding is similar to both friction welding and flash welding although the source of heating is different. For obtaining the best results the surfaces should be machined square and clean. Some beveling can be used to control the amount of upset. Materials that easily form on the surface adherent oxides upon heating cannot be easily welded in air by this process, typically among them are aluminum alloys and stainless steels. Heat is generally applied by flames of oxyfuel torches directed on the surfaces to be joined. Upon reaching the correct temperature, the torches are suddenly removed, and the two bodies [solid bars or hollow sections] are brought to contact and upset together under pressure [hydraulic equipment]. This variant is properly called the open joint process. Alternatively, when the parts are making contact under pressure before heat application from the outside, also by electrical induction, it is called the closed joint process. In either case flash material is expelled and a bulge is formed at the joint. Hot-pressure-welding is similar to both friction welding and flash welding although the source of heating is different. For obtaining the best results the surfaces should be machined square and clean. Some beveling can be used to control the amount of upset. Materials that easily form on the surface adherent oxides upon heating cannot be easily welded in air by this process, typically among them are aluminum alloys and stainless steels.

34.  Advantages: Simple process. Simple joint preparation. Relatively low cost equipment. Quick weld production. High quality joints. No filler metal needed. Minimally skilled operators required.  Limitations: Not all metals are weldable. Not easily automated. Length of cycle dependent on time for heating. Removal of flash and bulge required after welding. Only simple sections readily butt weldable.

36. Roll-welding [also called Roll Bonding] is a process that joins together a stack of sheets or plates that is fed through a cold rolling mill under sufficient pressure to produce significant deformation. These can just be stacked, possibly tack welded at certain locations, and then rolled. Thickness reduction is generally more than 60% for the first pass. To lessen the reduction required and to get solid state welding, one can preheat the stack and perform hot rolling, provided that the metals will not undergo excessive oxidation. For processing reactive metals, a version of the process called pack Roll- welding, entails the complete enclosure of the starting sheets in a pack sealed by fusion welding of the edges after removing all air. This permits processing of reactive metals or of multi-layer stacks. Metals should be ductile, like copper, aluminum, low carbon steel, nickel. Titanium alloys are more difficult to Roll-weld because of narrow range of possible working parameters. They are enclosed under vacuum in a steel envelope or can. This process is similar to forge welding except that pressure is applied by means of rolls rather than by means of hammer blows. Roll-welding [also called Roll Bonding] is a process that joins together a stack of sheets or plates that is fed through a cold rolling mill under sufficient pressure to produce significant deformation. These can just be stacked, possibly tack welded at certain locations, and then rolled. Thickness reduction is generally more than 60% for the first pass. To lessen the reduction required and to get solid state welding, one can preheat the stack and perform hot rolling, provided that the metals will not undergo excessive oxidation. For processing reactive metals, a version of the process called pack Roll- welding, entails the complete enclosure of the starting sheets in a pack sealed by fusion welding of the edges after removing all air. This permits processing of reactive metals or of multi-layer stacks. Metals should be ductile, like copper, aluminum, low carbon steel, nickel. Titanium alloys are more difficult to Roll-weld because of narrow range of possible working parameters. They are enclosed under vacuum in a steel envelope or can. This process is similar to forge welding except that pressure is applied by means of rolls rather than by means of hammer blows.

37. PROCESS SKETCH Metal sheets which are to be welded are pre-heated. Then they are made to travel in between the rollers. Due to the heat and pressure applied, coalescence occurs. Metal sheets which are to be welded are pre-heated. Then they are made to travel in between the rollers. Due to the heat and pressure applied, coalescence occurs. Variation of roll welding, depending on whether heating of work parts is done prior to process :  If no external heat, called cold roll welding  If heat is supplied, hot roll welding Variation of roll welding, depending on whether heating of work parts is done prior to process :  If no external heat, called cold roll welding  If heat is supplied, hot roll welding

38. Mild or low-alloy steel can be clad with a high-alloy material such as stainless steel. Strip cladding of copper with cupro-nickel by Roll-welding is used for making the composite material needed for minting certain coins. One important application is the production of heat exchanger panels with integral flow tubes embedded. Such elements are used for refrigerator evaporators, for radiators, for solar water heater panels and for industrial thermal controllers. It is also used for making bimetallic materials for the instrument industry. A modification of the process called Laser Roll-welding, was explored by Japanese scientists in 2002 in research studies and developed for joining dissimilar metals. "Steel sheet was heated with CO 2 laser beam, immediately followed by pressing it against the underlying aluminum sheet by means of a roll. Joints were made by inserting aluminum-brazing flux and shielding with argon gas to avoid surface oxidation. Temperature profiles across the section were simulated to identify suitable laser power and travel speed.”

40. It is a Solid State Welding process, in which two work pieces are bonded as a result of a pressure exerted to the welded parts combined with application of high frequency acoustic vibration (ultrasonic). Ultrasonic vibration causes friction between the parts, which results in a closer contact between the two surfaces with simultaneous local heating of the contact area. The temperature at the weld is not raised to the melting point and therefore there is no nugget similar to resistance welding. Inter atomic bonds, formed under these conditions provide strong joint. Ultrasonic cycle takes about 1 sec. The frequency of acoustic vibrations is in the range 20 to 70 KHz. Thickness of the welded parts is limited by the power of the ultrasonic generator. The metallic bonding is carried out in solid state, without applying of heat, filler rod or high pressure. Weld strength is equal to the strength of the base metal. Most ductile metals can be welded together and there are many combinations of dissimilar metals that can be welded. Dynamic shear stresses are generated in-between the metal interface due to the combine application of static load and high frequency. Because of dynamic stress a plastic deformation is occurred at the interface.

41. PROCESS SUMMARY  Welding occurs when the ultrasonic tip or electrode, the energy coupling device, is clamped against the work pieces and is made to oscillate in a plane parallel to the weld interface.  Ultrasonic energy will aid in cleaning the weld area by breaking up oxide films and causing them to be carried away.  The contacting face of weld tip and anvil is made of HSS or High Speed Steel because of here wear can occur during welding (HSS is the wear resistant metal).  The sonotrode and anvil in which surfaces to be contacted with work piece, that should be well surface finish.  This coupled with the clamping pressure provides for coalescence across the interface to produce the weld.  The vibratory energy that produces the minute deformation comes from a transducer which converts high-frequency alternating electrical energy into mechanical energy.

42. PROCESS SUMMARY  It is usual to have a slightly radius surface on the sonotrode tip face, the ratio is about 50 to 100 times the thickness of the weld material.  A frequency converter is employed, which is converted the line frequency 50Hz into high frequency electrical power.  A transducer attachment converts the electrical frequency into ultrasonic high frequency energy.  The high frequency energy is transmitted to the weld joint through the welding tip.  This produces minute deformations which create a moderate temperature rise in the base metal at the weld zone.  A coupler is made as the bridge between welding tip and transducer.  The tip oscillates on the weld joint with the help of some mechanism.  The transducer is coupled to the work by various types of tooling which can range from tips similar to resistance welding tips to resistance roll welding electrode wheels.

43. (a) Components of an ultrasonic-welding machine for making lap welds. The lateral vibrations of the tool tip cause plastic deformation and bonding at the interface of the work pieces deformation and bonding at the interface of the work pieces. (b) Ultrasonic seam welding using a roller as the sonotrode. (a) Components of an ultrasonic-welding machine for making lap welds. The lateral vibrations of the tool tip cause plastic deformation and bonding at the interface of the work pieces deformation and bonding at the interface of the work pieces. (b) Ultrasonic seam welding using a roller as the sonotrode.

44. PROS & CONS

45. Wire terminations and splicing in electrical and electronics industry. Eliminates need for soldering Assembly of aluminum sheet metal panels Welding of tubes to sheets in solar panels Assembly of small parts in automotive industry