FUNDAMENTALS OF WELDING
FUNDAMENTALS OFWELDING1.2.3.4.Overview of Welding TechnologyThe Weld JointPhysics of WeldingFeatures of a Fusion Welded Joint 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Joining and AssemblyDistinguished Joining - welding, brazing, soldering, and adhesivebonding These processes form a permanent joint betweenparts Assembly - mechanical methods (usually) of fasteningparts together Some of these methods allow for easy disassembly,while others do not 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Welding Defined Joining process in which two (or more) parts arecoalesced at their contacting surfaces by applicationof heat and/or pressure Many welding processes are accomplished byheat alone, with no pressure applied Others by a combination of heat and pressure Still others by pressure alone with no external heat In some welding processes a filler material isadded to facilitate coalescence 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Why Welding is Important Provides a permanent joint Welded components become a single entity Usually the most economical way to join parts interms of material usage and fabrication costs Mechanical fastening usually requires additionalhardware (e.g., screws) and geometric alterationsof the assembled parts (e.g., holes) Not restricted to a factory environment Welding can be accomplished "in the field" 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Limitations and Drawbacksof Welding Most welding operations are performed manually andare expensive in terms of labor cost Most welding processes utilize high energy and areinherently dangerous Welded joints do not allow for convenientdisassembly Welded joints can have quality defects that aredifficult to detect 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Faying Surfaces in Welding The part surfaces in contact or closeproximity that are being joined Welding involves localizedcoalescence of the two metallic partsat their faying surfaces Welding is usually performed on partsmade of the same metal However, some welding operationscan be used to join dissimilar metals 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Types of Welding Processes Some 50 different types of welding processes havebeen catalogued by the American Welding Society(AWS) Welding processes can be divided into two majorcategories: Fusion welding Solid state welding 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Fusion Welding Joining processes that melt the base metals In many fusion welding operations, a filler metal isadded to the molten pool to facilitate the processand provide bulk and added strength to thewelded joint A fusion welding operation in which no filler metalis added is called an autogenous weld 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Some Fusion Welding Processes Arc welding (AW) – melting of the metals isaccomplished by an electric arc Resistance welding (RW) - melting is accomplishedby heat from resistance to an electrical currentbetween faying surfaces held together underpressure Oxyfuel gas welding (OFW) - melting is accomplishedby an oxyfuel gas such as acetylene 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Arc Welding Basics of arc welding: (1) before the weld; (2) during theweld, the base metal is melted and filler metal is added tomolten pool; and (3) the completed weldment 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Solid State Welding Joining processes in which coalescence results fromapplication of pressure alone or a combination ofheat and pressure If heat is used, temperature is below melting pointof metals being welded No filler metal is added in solid state welding 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Some Solid State WeldingProcesses Diffusion welding (DFW) –coalescence is by solidstate fusion between two surfaces held togetherunder pressure at elevated temperature Friction welding (FRW) - coalescence by heat offriction between two surfaces Ultrasonic welding (USW) - coalescence by ultrasonicoscillating motion in a direction parallel to contactingsurfaces of two parts held together under pressure 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Principal Applications of Welding Construction - buildings and bridgesPiping, pressure vessels, boilers, and storage tanksShipbuildingAircraft and aerospaceAutomotiveRailroad 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Welder and Fitter The welder manually controls the path or placementof welding gun Often assisted by second worker, called a fitter, whoarranges the parts prior to welding Welding fixtures and positioners are used to assistin this function 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
The Safety Issue Welding is inherently dangerous to human workers High temperatures of molten metals In gas welding, fuels (e.g., acetylene) are a firehazard Many welding processes use electrical power, soelectrical shock is a hazard 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Special Hazards in Arc Welding Ultraviolet radiation emitted in arc welding is injuriousto human vision Welder must wear special helmet with darkviewing window Filters out dangerous radiation but welder isblind except when arc is struck Sparks, spatters of molten metal, smoke, and fumes Ventilation needed to exhaust dangerous fumesfrom fluxes and molten metals 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Automation in Welding Because of the hazards of manual welding, and toincrease productivity and improve quality, variousforms of mechanization and automation are used Machine welding – mechanized welding undersupervision and control of human operator Automatic welding – equipment performs weldingwithout operator control Robotic welding - automatic welding implementedby industrial robot 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
The Weld Joint The junction of the edges or surfaces of parts thathave been joined by welding Two issues about weld joints: Types of joints Types of welds used to join the pieces that formthe joints 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Five Types of Joints (a) Butt joint, (b) corner joint, (c) lap joint, (d) tee joint,and (e) edge joint 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Types of Welds Each of the preceding joints can be made by welding Other joining processes can also be used for some ofthe joint types There is a difference between joint type and the wayit is welded - the weld type 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Fillet Weld Used to fill in the edges of plates created by corner,lap, and tee joints Filler metal used to provide cross section inapproximate shape of a right triangle Most common weld type in arc and oxyfuel welding Requires minimum edge preparation 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Fillet Welds (a) Inside single fillet corner joint; (b) outside single filletcorner joint; (c) double fillet lap joint; (d) double fillet teejoint (dashed lines show the original part edges) 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Groove Welds Usually requires part edges to be shaped into agroove to facilitate weld penetration Edge preparation increases cost of parts fabrication Grooved shapes include square, bevel, V, U, and J,in single or double sides Most closely associated with butt joints 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Groove Welds (a) Square groove weld, one side; (b) single bevel grooveweld; (c) single V-groove weld; (d) single U-groove weld;(e) single J-groove weld; (f) double V-groove weld forthicker sections (dashed lines show original part edges) 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Plug Weld and Slot Weld (a) Plug weld and (b) slot weld 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Spot Weld and Seam Weld Fused section between surfaces of two sheets or plates: (a)spot weld and (b) seam weld Used for lap joints Closely associated with resistance welding 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Flange Weld and Surfacing Weld (a) Flange weld and (b) surfacing weld used not to joinparts but to deposit filler metal onto surface of a base part 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
How does seam welding is differfrom spot welding? Seam welding is same as of Spot welding. Differenceis that in case of seam welding the rotating wheel isused and it is the fast process than spot welding. Spot welding is mainly using for joining of the carbody and Seam welding is using for making of fueltank and all. 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Seam weldingSpot welding 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Physics of Welding Fusion is most common means of achievingcoalescence in welding To accomplish fusion, a source of high density heatenergy must be supplied to the faying surfaces Resulting temperatures cause localized melting ofbase metals (and filler metal, if used) For metallurgical reasons, it is desirable to melt themetal with minimum energy but high heat densities 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Power Density Power transferred to work per unit surface area,W/mm2 (Btu/sec-in2) If power density is too low, heat is conducted intowork, so melting never occurs If power density too high, localized temperaturesvaporize metal in affected region There is a practical range of values for heatdensity within which welding can be performed 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Comparisons Among WeldingProcesses Oxyfuel gas welding (OFW) develops large amountsof heat, but heat density is relatively low becauseheat is spread over a large area Oxyacetylene gas, the hottest OFW fuel, burns ata top temperature of around 3500 C (6300 F) Arc welding produces high energy over a smallerarea, resulting in local temperatures of 5500 to6600 C (10,000 to 12,000 F) 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Power Densities for 0(30)Resistance1,000(600)Laser beam9,000(5,000)Electron beam10,000(6,000)Welding process 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Power Density Power entering surface divided by correspondingsurface area:PPD Awhere PD power density, W/mm2 (Btu/sec-in2); P power entering surface, W (Btu/sec); and A surfacearea over which energy is entering, mm2 (in2) 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Unit Energy for Melting Quantity of heat required to melt a unit volume ofmetal Unit energy Um is the sum of: Heat to raise temperature of solid metal to meltingpoint Depends on metal’s volumetric specific heat Heat to transform metal from solid to liquid phaseat melting point Depends on metal’s heat of fusion 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Heat Transfer Mechanisms inWelding Not all of the input energy is used to melt the weldmetal1. Heat transfer efficiency f1 - actual heat receivedby workpiece divided by total heat generated atsource2. Melting efficiency f2 - proportion of heat receivedat work surface used for melting The rest is conducted into work metal 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Heat Transfer Mechanisms inWelding 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Heat Available for WeldingHw f1 f2 Hwhere Hw net heat available for welding; f1 heattransfer efficiency; f2 melting efficiency; and H total heat generated by welding process 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Heat Transfer Efficiency f1 Proportion of heat received at work surface relative tototal heat generated at source Depends on welding process and capacity toconvert power source (e.g., electrical energy) intousable heat at work surface Oxyfuel gas welding processes are relativelyinefficient Arc welding processes are relatively efficient 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Melting Efficiency f2 Proportion of heat received at work surface used formelting; the rest is conducted into the work Depends on welding process but also thermalproperties of metal, joint shape, and workthickness Metals with high thermal conductivity, such asaluminum and copper, present a problem inwelding because of the rapid dissipation of heataway from the heat contact area 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Energy Balance Equation Net heat energy into welding operation equals heatenergy required to melt the volume of metal weldedHw Um Vwhere Hw net heat energy delivered to operation, J(Btu); Um unit energy required to melt the metal,J/mm3 (Btu/in3); and V volume of metal melted,mm3 (in3) 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Typical Fusion Welded Joint Cross section of a typical fusion welded joint: (a) principalzones in the joint, and (b) typical grain structure 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Features of Fusion Welded Joint Typical fusion weld joint in which filler metal has beenadded consists of: Fusion zone Weld interface Heat affected zone (HAZ) Unaffected base metal zone 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Heat Affected Zone Metal has experienced temperatures below meltingpoint, but high enough to cause microstructuralchanges in the solid metal Chemical composition same as base metal, butthis region has been heat treated so that itsproperties and structure have been altered Effect on mechanical properties in HAZ isusually negative It is here that welding failures often occur 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
FUNDAMENTALS OF WELDING 1. Overview of Welding Technology 2. The Weld Joint 3. Physics of Welding 4. Features of a Fusion Welded Joint 2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
6.3 Mechanised/automatic welding 114 6.4 TIG spot and plug welding 115 7 MIG welding 116 7.1 Introduction 116 7.2 Process principles 116 7.3 Welding consumables 130 7.4 Welding procedures and techniques 135 7.5 Mechanised and robotic welding 141 7.6 Mechanised electro-gas welding 143 7.7 MIG spot welding 144 8 Other welding processes 147 8.1 .
seam butt welding resistance butt welding flash butt welding resistance butt welding shielded unshielded other process plasma laser resistance butt welding inert gas welding submerged arc welding atomic hydrogen shielded metal arc welding (coated electrode) esepl w w w . e u r e k a e l e c t r o d e s .
the welding processes most often used in today's industry including plasma arc cutting, oxyfuel gas cutting and welding, Gas Metal Arc Welding (GMAW), Flux-Cored Arc Welding (FCAW), Shielded Metal Arc Welding (SMAW), and Gas Tungsten Arc Welding (GTAW). Flat welding positions and basic joints will be practiced. Pipe and tube welding
3. Classification of Underwater Welding Underwater welding may be divided into two main types: a) Wet welding b) Dry welding Fig. 3.1 Classification of underwater welding 3.1 Wet welding 3.1.1. Wet welding with coated electrode Wet welding is performed at ambient pressure with the welder-diver in the water and no physical barrier
10.6 Braze-welding 460 Exercises 466 11 Joining processes (welding) 467 11.1 Fusion welding 468 11.2 Oxy-acetylene welding 468 11.3 Manual metal-arc welding 490 11.4 Workshop testing of welds 504 11.5 Miscellaneous fusion welding processes 506 11.6 Workholding devices for fusion welding 509 11.7 Resistance welding 515
Welding residual stresses and stress relieve Formation of the weld metal Solidification of the weld metal Phase transformations during welding Basics of welding methods used in welding of zirconium alloys TIC Laser Welding Electron Beam Welding Upset shape welding Resistance Appendix C -R
affected zone. Welding processes that are commonly used with the corrosion-resistant alloys are shown in Table 1. In addition to these common arc welding processes, other welding processes such as plasma arc welding, resistance spot welding, laser beam welding, electron beam welding, and submerged arc welding can be used. Because of
the limited depth of underwater welding. Welding equipment transformed from manual welding to underwater automatic welding. The efficient and low-cost underwater welding was achieved[7]. In order to study the automatic welding technology under larger deep-water environment, the underwater automatic welding system was designed in this paper. The
