3Principle of the process Structure and configurationProcess modelingDefectsDesign For Manufacturing (DFM)Process variation
4WeldingProcess in which two (or more) parts are coalesced at their contacting surfaces by application of:Heat and pressureSome welding processes use a filler material added to facilitate coalescence
5Principle of weldingAssembly two parts together by creating a fusion and/or deformation in the interaction area, which is further based on the physics laws such as fusion and solid state deformation.Add pic of assembly by no fastenersOr give example
6Principle of welding Fusion welding (FW) Heat materials to melt the materials of compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the materialAdd pic of assembly by no fastenersOr give example
7Solid State welding (SSW) Principle of weldingSolid State welding (SSW)On the interface between two materials there is no melting that happens but the interface of materials is reconfigured to form many structure.Add pic of assembly by no fastenersOr give example
8Two Categories of Welding Processes Fusion welding - coalescence is accomplished by melting the two parts to be joined, in some cases adding filler metal to the jointExamples: arc welding, oxyfuel gas welding, resistance spot weldingSolid state welding - heat and/or pressure are used to achieve coalescence, but no melting of base metals occurs and no filler metal is addedExamples: forge welding, diffusion welding, friction welding
9The general function of welding Provides a permanent jointOne of the most economical ways to join parts in terms of material usage and fabrication costsMechanical fastening usually requires additional hardware (e.g., screws) and geometric alterations of the assembled parts (e.g., holes)Not restricted to a factory environmentWelding can be accomplished "in the field"
10Limitations and Drawbacks of Welding Most welding operations are performed manually and are expensive in terms of labor cost.Most welding processes utilize high energy and are inherently dangerous.Welded joints do not allow for convenient disassembly.Welded joints can have quality defects that are difficult to detect.
11Solid State Welding (SSW) Fusion Welding (FW)Solid State Welding (SSW)Arc Welding (AW)
12Principle of the process Structure and configurationProcess modelingDefectsDesign For Manufacturing (DFM)Process variation
13Fusion Welding: Arc Welding (AW) A fusion welding process in which coalescence of the metals is achieved by the heat from an electric arc between an electrode and the workElectric energy from the arc produces temperatures ~ 10,000 F (5500 C), hot enough to melt any metal.Most AW processes add filler metal to increase volume and strength of weld joint.- Uses an electric arc to generate heat- Electric arc melts the metal parts that you are welding & it also melts the filler metal to increase the strength of the weld joint
14Fusion Welding: Arc Welding (AW) A pool of molten metal is formed near electrode tip, and as electrode is moved along joint, molten weld pool solidifies in its wake
15Solid State Welding (SSW) Fusion Welding (FW)Solid State Welding (SSW)Arc Welding (AW)Consumable electrodesNon-consumable electrodes
16Two Basic Types of Arc Welding (Based on Electrodes) Consumable electrodesconsumed during welding processadded to weld joint as filler metalin the form of rods or spools of wireNon-consumable electrodesnot consumed during welding process but does get gradually erodedfiller metal must be added separately if it is added
17Arc welding (AW): Arc Shielding At high temperatures in AW, metals are chemically reactive to oxygen, nitrogen, and hydrogen in airMechanical properties of joint can be degraded by these reactionsArc must be shielded from surrounding air in AW processes to prevent reactionArc shielding is accomplished byShielding gases, e.g., argon, helium, CO2Flux
18Arc welding (AW): FluxA substance that prevents formation of oxides and other contaminants in welding, which comes fromgranules that are created from the welded material.a coating on the stick electrode that melts during welding to cover operation.a core that is within tubular electrodes and is released as electrode is consumed.Melts during welding to be liquid slag that hardens when cooled. The slag should be removed for a clean look by brushing or grinding off.
19Consumable Electrode AW Processes Shielded Metal Arc Welding (or Stick Welding)Gas Metal Arc Welding (or Metal Inert Gas Welding)Flux‑Cored Arc WeldingElectro-gas WeldingSubmerged Arc Welding2 main processes are:
20AW: Consumable: Shielded Metal Arc Welding (SMAW) Uses a consumable electrode consisting of a filler metal rod and coating around rod.Coating composed of chemicals that provide flux and shielding.Low cost welding system: Power supply, connecting cables, and electrode holder available for $300 to $400.
21SMAW ApplicationsUsed for steels, stainless steels, cast irons, and certain nonferrous alloys.Not used or rarely used for and its alloys, copper alloys, and titanium.Can be used in windy weather.Can be used on dirty metals (i.e. painted or rusted surfaces).Good for repair work.Makes thick welds.good for all purpose welding
22AR: Consumable: Gas Metal Arc Welding (GMAW) or Metal Inert Gas (MIG) Welding Uses a consumable bare metal wire as electrode with shielding by flooding arc with a gasWire is fed continuously and automatically from a spool through the welding gun.Shielding gases include argon and helium for aluminum welding, and CO2 for steel welding.Bare electrode wire (no flux) plus shielding gases eliminate slag on weld bead. No need for manual grinding and cleaning of slagMedium cost welding system: $1000 to $1200
24GMAW Advantages over SMAW Continuous welding because of continuous wire electrode. Sticks must be periodically changed in SMAW.Higher deposition rates.Eliminates problem of slag removal.Can be readily automated.Has better control to make cleaner & narrower welds than SMAW.
25GMAW ApplicationsUsed to weld ferrous and various non-ferrous and metals.Good for fabrications such as frames and farm equipment.Can weld thicker metal (not as thick as SMAW).Metal must be clean to start weld.
27AW: non-consumable: Gas Tungsten Arc Welding (GTAW) or Tungsten Inert Gas (TIG) Welding Uses a non-consumable tungsten electrode and an inert gas for arc shieldingMelting point of tungsten = 3410C (6170F).Used with or without a filler metal. When filler metal used, it is added to weld pool from separate rod or wire.Applications: aluminum and stainless steel mostly.High cost for welding system: $4000.
28Gas Tungsten Arc Welding Filler rodFiller rod is fed separate
29Advantages and Disadvantages of GTAW High quality welds for suitable applications- Welds are cleaner and narrower than MIGNo spatter because no filler metal through arcLittle or no post-weld cleaning because no fluxDisadvantages:More difficult to use than MIG weldingMore costly than MIG welding
30GTAW ApplicationsUsed to weld ferrous and various non-ferrous and metals.Can weld various dissimilar metals together.Good for fabrications such as aircraft or race car frames.Used for welding thinner metal parts (not as thick as MIG).Metal must be very clean to start weld.
31Solid State Welding (SSW) Fusion Welding (FW)Solid State Welding (SSW)Arc Welding (AW)Oxyfuel gas welding
32Oxyfuel Gas Welding (OFW) Group of fusion welding operations by a high temperature flame that burns various fuels mixed with oxygenOxyfuel gas is also used in flame cutting torches to cut and separate metal plates and other partsMost important OFW process is oxyacetylene welding (has high temperatures – up to 3480C)Filler metal is sometimes addedComposition must be similar to base metalFiller rod often coated with flux to clean surfaces and prevent oxidationLow cost for welding system: $400
34Oxyacetylene TorchMaximum temperature reached at tip of inner cone, while outer envelope spreads out and shields work surface from atmosphereShown below is neutral flame of oxyacetylene torch indicating temperatures achieved
35Oxyacetylene Gas Welding Applications Suitable for low quantity production and repair jobsUsed for welding thinner parts
36Solid State Welding (SSW) SummaryFusion Welding (FW)Solid State Welding (SSW)ShieldingFluxOxyfuel weldingArc weldingConsumable electrodesNon-consumable electrodesVarious welding processes (AW) are developed to address the two issues: shielding and flux