Presentation on theme: "Fusion-Welding and Solid State Welding Processes"— Presentation transcript:
1Fusion-Welding and Solid State Welding Processes Team 6:Christopher ChavezSteve De La TorreDavid JawMatthew WitkowskiNovember 23, 2005ME260L
2Topics: General Safety General Welding OxyFuel Welding Arc Welding Solid-State Welding ProcessesElectron-beam Welding (EBW)Oxyfuel CuttingArc CuttingResistance Welding
3General Welding Safety: Every year approximately 500K Welding Accidents occurOccupational Safety & Health Administration (OSHA)Standard Welding, Cutting and BrazingInstallation of equipmentEnvironmental ControlsExposure Limits (Fumes, Vapor, and Time)Operation and MaintenanceCommon AccidentsFlash and Retinal BurnsVapor HazardsElectric ShockFires or Flammable accidents
4General Welding Safety: Personal Protective Equipment (PPE)Welder is properly groundedAdequate ventilationWork in a Firesafe zoneFirst-Aid kit
5General Characteristics of Fusion Welding Processes: Process DescriptionWelding is the process by which 2 metal parts are joined by melting the parts (application of heat) at the points of contact. Most frequently used methods are Oxy-Fuel and Electric Arc welding.There are more than 80 different types of welding operation in commercial use.
6General Characteristics of Fusion Welding Processes:
7General Characteristics of Fusion Welding Processes:
8OxyFuel or OxyAcetylene Gas Welding: OxyFuel Gas Welding is a term used to describe any welding process that uses a fuel gas with Oxygen.The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a special welding torch or blowpipe, producing, when burned, a heat of 6,300 degrees, which is more than twice the melting temperature of the common metals.Oxygen and acetylene (typically), to produce the flames.Filler Metals which may be added to the joints while molten in order to give the weld sufficient strength and proper formChemical powders, called fluxes, which assist in the flow of metal and in doing away with many of the impurities and other objectionable features.
9OxyFuel Gas Welding:Torch Practice. The actual work of welding and cutting requires preliminary preparation in the form of heat treatment for the metals, including preheating, annealing and temperingOxygen, the gas which supports the rapid combustion of the acetylene in the torch flame, is one of the elements of the air.The equipment used for oxyacetylene welding consists of a source of oxygen and a source of acetylene from a portable or stationary outfit, along with a cutting attachment or a separate cutting torch.
10OxyFuel Gas Welding:This apparatus used in gas welding consists basically of a torch, two pressure regulators and twin flexible hoses.The regulators are attached to the fuel and to the oxygen sources. The regulators are attached to the tanks and drops the pressure from about kPa (3000 lbf/in² = 200 atm) to a lower pressure for the torch.
11OxyFuel Gas Welding: General view of and Cross-section of a torch used in oxyacetylene welding. The acetylene valve is opened first; the gas is lit with a spark lighter or a pilot light; then the oxygen valve is opened and the flame adjusted.Basic equipment used in oxyfuel-gas welding. all threads on acetylene fittings are left-handed, whereas those for oxygen are right-handed. Oxygen regulators are usually painted green, acetylene regulators red.
12OxyFuel Gas Welding:Filler MetalsFiller rods or Wire, Copper alloy filler rods and fluxes enable the joining of manybase metals. They are especially useful onsteel and cast iron.FluxThe flux is to retard oxidation of the surface of the parts being welding by generating a gaseous shield
13OxyFuel Gas Welding: Flames Neutral flame Oxidizing Flame Welding is generally carried out using the neutral flame setting which has equal quantities of oxygen and acetylene.Oxidizing FlameThe oxidising flame is obtained by increasing just the oxygen flow rateCarburizing FlameThe carburising flame is achieved by increasing acetylene flow in relation to oxygen flow.
16Arc Welding Process:The term arc welding applies to a large and varied group of processes that use an electric arc as the source of heat to melt and join metals. In arc welding processes, the joining of metals, or weld, is produced by the extreme heat of an electric arc drawn between an electrode and the workpiece, or between two electrodes.Metal Electrodes. In bare metal-arc welding, the arc is drawn between a bare or lightly coated consumable electrode and the workpiece. Filler metal is obtained from the electrode.
17Various Types of Arc Welding Arc Welding Process:Various Types of Arc WeldingNonconsumable-electrode or Gas Tungsten ArcGTAW or tungsten inert gas (TIG) welding, is a manual welding process that uses a non-consumable electrode made of tungsten, an inert or semi-inert gas mixture, and a separate filler material. Especially useful for welding thin materials such as Stainless Steel and light metals.Used on Bicycle, aircraft and naval applications.Plasma ArcPAW is an extension of the GTAW process. The arc is formed between an electrode (which is usually but not always made of a sintered tungsten) and the workpiece. The key difference from GTAW is that in PAW, by positioning the electrode within the body of the torch, the plasma arc can be separated from the shielding gas envelope.
18Arc Welding Process: Gas Tungsten Arc The gas tungsten-arc welding process, formerly known as TIG (for tungsten inert gas) welding.Equipment for gas tungsten-arc welding operations. Source: American Welding Society.
19Arc Welding Process: Plasma Arc Two types of plasma-arc welding processes: (a) transferred, (b) nontransferred. Deep and narrow welds can be made by this process at high welding speeds.
20Electrodes for Arc Welding Arc Welding Process:Electrodes for Arc WeldingElectrodes are identified by numbers and letters or by color codeDimensions are in the range of 6 to 8 inches in length 1/16 to 5/16 in diameter.Classified by strength, current and type of coating.A free information web site on any and all welding processes, procedures, equipments etc…
21Arc Welding Process: Shielding Metal Arc The arc is drawn between a covered consumable metal electrode and workpiece.The electrode covering is a source of arc stabilizers, gases to exclude air, metals to alloy the weld, and slags to support and protect the weld.Shielding is obtained from the decomposition of the electrode covering.Pressure is not used and filler metal is obtained from the electrode.Shielded metal arc welding electrodes are available to weld carbon and low alloy steels; stainless steels; cast iron; aluminum, copper, and nickel, and their alloys
22Arc Welding Process: Shielding Metal Arc Schematic illustration of the shielded metal-arc welding process. About 50% of all large-scale industrial welding operations use this process.Schematic illustration of the shielded metal-arc welding operations (also known as stick welding, because the electrode is in the shape of a stick).
23Arc Welding Process: Gas Metal Arc In this process, coalescence is produced by heating metals with an arc between a continuous filler metal (consumable) electrode and the workpiece.The arc, electrode tip and molten weld metal are shielded from the atmosphere by a gas.Shielding is obtained entirely from an externally supplied inert gas, gas mixture, or a mixture o f a gas and a flux.The electrode wire for MIG welding is continuously fed into the arc and deposited as weld metal.Wire diameters 0.05 to 0.06 in. (0.13 to 0.15 cm) are average. Because of the small sizes of the electrode and high currents used in MIG welding, the melting rates of the electrodes are very high.All commercially important metals such as carbon steel, stainless steel, aluminum, and copper can be welded with this process in all positions by choosing the appropriate shielding gas, electrode, and welding conditions.
24Arc Welding Process: Submerged-Arc Basically, in submerged arc welding, the end of a continuous bare wire electrode is inserted into a mound of flux that covers the area or joint to be welded. An arc is initiated, causing the base metal, electrode, and flux in the immediate vicinity to melt. The electrode is advanced in the direction of welding and mechanically fed into the arc, while flux is steadily added. The melted base metal and filler metal flow together to form a molten pool in the joint. At the same time, the melted flux floats to the surface to form a protective slag cover.
25Arc Welding Process: Submerged-Arc Schematic illustration of the submerged-arc welding process and equipment. The unfused flux is recovered and reused. Source: American Welding Society.
32Advantages of LBW over EBW A vacuum is not requiredProcess is easier because laser beams can be shaped and manipulatedDo not generate x-raysQuality is better: less tendency for incomplete fusion, porosity, and distortion
34Oxyfuel-gas Cutting (OFC) The heat source is used to remove material instead of weld itPreheat the workpiece with fuel gasThe higher the carbon content of the steel, the higher the preheating temperatureCutting takes place after the oxidation (burning) of the steel
35Underwater CuttingTorches create a blanket of compressed air between the flame and the surrounding water
36Arc Cutting Air carbon-arc cutting (CAC-A) A carbon electrode is used, and the molten metal is blown away by a high-velocity air jet
37Plasma-arc cutting (PAC) -Produces the highest temperatures-used for rapid cutting of nonferrous and stainless-steel plates
383 distinct zones in a weld joint 1. Base metal2. Heat-affected zone3. Weld metal
39Heat-affected zone (HAZ) Within the base metalThe properties and microstructure of the HAZ depend on the rate of heat input and cooling and the temperature to which this zone was raised
40Weld QualityPorosityCaused by gases released during melting of the weld area but trapped during solidificationChemical reactions during weldingContaminants
41Slag InclusionsCompounds such as oxides, fluxes, and electrode-coating materials trapped in the weld zone
42Incomplete fusion and penetration Incomplete fusion produces poor weld beadsIncomplete penetration occurs when the depth of the welded joint is insufficient
44CracksTypes of cracks: longitudinal, transverse, crater, underbead, and toe cracks
45Lamellar Tears develop because of shrinkage of the restrained components of the structure during coolingResidual Stresses caused by expansion and contraction of the weld area during heating and cooling
46Weld Testing Destructive testing Tension test: longitudinal and transverse tension tests are performed on specimens removed from actual welded jointsTension-shear test: used so the shear strength of the weld metal and the location of fracture can be determinedBend Test: determines the ductility and strength of welded jointsFracture toughness test: use impact testing techniques
49Non-destructive testing techniques -Visual-Radiographic (x-rays)-Magnetic-particle-Liquid-penetrant-UltrasonicUsed instead of destructive for critical applications where weld failure can be catastrophic
50Joint Design and Process Selection Select a type of weld and joint that is most practical for your application
52IntroductionSolid-State Welding – a process in which joining takes place without fusion at the interface of the two parts to be welded.Involves one or more of the following phenomena:DiffusionPressureRelative Interfacial Movements
53Cold WeldingPressure is applied to the work pieces throw dies or rollsCan be used to join small work pieces made of soft ductile metalsExample: Wire stock and electrical connections
54Roll Bonding Pressure is applied through a pair of rolls This process can be carried out at high temperatures
55Ultrasonic WeldingThe faying surfaces of the two components are subjected to a static normal force and oscillating shearing stresses.Frequency of oscillation is generally between 10kHz and 75kHzThe shearing stresses cause plastic deformation at the interface of the two components.The temperature generated in the weld zone is usually in the range of one-third to one-half of the melting point.
59Resistance WeldingResistance Welding- process in which heat required for welding is produced by means of electrical resistance across the two components being joinedAdvantages not requiring consumable electrodes, shielding gases, or flux.Similar or dissimilar materials can be joinedResistance welding require specialized machinery. Mostly Computer Controlled
60Resistance Spot Welding Resistance Spot Welding the tips of two opposing solid, cylindrical touch a lap joint and resistance heating produces a spot weld.Advantages limited work piece deformation, high production rates, easy automation, and no required filler materials
61Simplest and most commonly used of the resistance welding processes. Widely used in fabricating sheet-metal parts.Weld strength is significantly lower than with other welding methods, making the process suitable for only certain applications
62Different machines for specific tasks Rocker-arm type typically for smaller partsPress-type used for larger work pieces
63Resistance Seam Welding Similar to spot welding with electrodes being replaced by wheels or rollers.Continuous AC power supply is used.
64Able to create continuous seam that is liquid tight Roll spot welding current applied intermittently to create series of welds.Process used in making cans, mufflers, gasoline tanks.
65High-Frequency resistance welding Process similar to seam welding except with high frequency current.High frequency current used is up to 450 kHzUsed in making tubing, I-beams, wheel rims.
66Resistance projection welding In resistance projection welding high electrical resistance is developed by embossing one or more projections.Produces many welds in one pass, prolongs electrode life, capable of welding metals of different thicknesses.
67Flash WeldingFlash Welding also referred to as flash butt welding, heat is generated by the arc created by two members, when proper temperature is reached force is applied and weld is formed by plastic deformation of the joint.This process produces high quality welds.Used in end in end joining, joining sheets of metal, this is the process used for creating most rings.
68Stud WeldingStud welding similar to flash welding however used with a metal stud and a smaller part, often a rod.A ceramic ferrule in order to concentrate heat and prevent oxidation.Used in automobile construction, electrical panels and building construction.
69Explosion WeldingExplosive welding is a solid state welding process, which uses a controlled explosive detonation to force two metals together at high pressureThe resultant composite system is joined with a durable, metallurgical bond.
70●Radiation light shielding mask for a KEK accelerator Diffusion BondingProcess in which the strength of the bond results primarily from diffusion and secondly from deformation of the surfaces.Bonded interface will essentially have the same physical and mechanical properties as the base metal.●Radiation light shielding mask for a KEK accelerator Diffusion bonding of Cu and Al
71Diffusion bonding/Superplastic forming Sheet metal structures can be formed by combing diffusion bonding and super plastic forming.First diffusion bonded and expanded in a mold.Used in aircraft and aerospace applications.
72Questions: Oxyfuel cutting is used Resistance Spot Welding is known for its:Limited work piece deformationHigh production rate and easy automationNo need for filler metalsAll of aboveOxyfuel cutting is usedSteelAluminumNone of the aboveSolid State Welding involves healing material to a molten stateTrueFalseQuestions:What is one type of PPE is required for Welding?Eye ProtectionHearing ProtectionLent free GlovesRespiratorWhat best describes “A Neutral Flame” in a Oxy-Fuel welding process?Equal amount of oxygen and acetyleneMore oxygen than acetyleneMore acetylene than oxygen