Joining and Cutting Processes

Engr 241-R11 Fusion Welding Processes Fusion Welding involves heating two materials above their melting temperatures (electrically or chemically). Filler (rods) metals are added to the weld area during the welding of a joint (supply additional material to weld zone).

Processes Oxyfuel Gas Arc Consumed Electrode Non-Consumed Electrode Resistance Solid State Other – “High Energy” Engr 241-R12

3 Oxyfuel Gas Welding Process that uses a fuel gas combined with oxygen to produce a flame Typically used for structural sheet-metal fabrication, automotive bodies, and various repair tasks Most common fuels used - acetylene (oxyacetylene). Manual operation, portable & flexible.Low equipment cost.

Torch allows for controlling and mixing gases

Oxygen and fuel gas cylinders

Cylinder Safety Caps on when moving Secure to truck or wall Keep upright (Acetylene) (1/7 Rule) Hand over regulator when opening Read labels – don’t rely on colors Dangers of compressed oxygen Engr 241-R16

7 Neutral Flame: 1:1 ratio (oxygen vs. fuel). Oxidizing Flame: greater oxygen supply (not for steels). Reducing (Carburizing) Flame: lower oxygen supply (lower temperature)- brazing. Oxyfuel Gas Welding- Flame Types

Neutral - the oxygen and fuel gases combine oxygen burns up the carbon and the hydrogen in the fuel gas then releases only heat and harmless gases flame temp is 5589 deg F.

Engr 241-R19 Oxyfuel Gas Welding- Flux Retard oxidation of surfaces of the parts being welded Dissolves/Removes oxides or other substances Stronger joints

Engr 241-R110 Arc Welding Processes (Consumable Electrode) Developed in the mid-1800s Heat obtained through electrical energy

Engr 241-R111 Shielded Metal Arc Welding (SMAW) Stick welding 50% of all large-scale industrial welding operations- portable process. Electric arc generated between tip of coated electrode and the workpiece. Electrode coating produces a shielding gas to protect from oxygen.

Engr 241-R112

11/12/2015 Electric arc between flux covered electrode and base metal

Engr 241-R114

Engr 241-R115 SMAW (Cont.) (DCEN) electrode negative Workpiece positive, electrode negative. Sheet metals - shallow penetration, gap joints. (DCEP) electrode positive Electrode positive, workpiece negative. Deeper penetration. (AC) Alternating current

Engr 241-R116

Engr 241-R117 Thick sections, large electrodes at max current. Manual, portable, and flexible. AC- DC machines, low cost equipment SMAW (Cont.)

Engr 241-R118 Submerged Arc Welding Weld arc is shielded by a granular flux. Flux is fed to weld zone by gravity. Flux covers molten metal which prevents spatter, sparks, UV radiation, or fumes. Flux is recovered times productivity of SMAW, automatic, horizontal, low skill,

Submerged Arc

Underwater SMAW use well insulated electrode holder and special water proof covered electrodes because of rapid cooling - use stringer beads not weaving short arc length and DCEN poor visibility - use #4 or #8 lens communication system normally have 80% of the tensile strength and 50 of the ductility of normal welds

Engr 241-R121 Gas Metal Arc Welding (GMAW) Formerly MIG (Metal Inert Gas). Argon, helium, carbon dioxide, or mix (Shield the arc to prevent oxidation). Wire fed automatically through nozzle into arc.

Engr 241-R122

Engr 241-R123 Rapid, economical, twice SMAW productivity. Most production done today Can be automated (robots), low skill, DC, medium cost equipment. GMAW (Cont.)

Engr 241-R124

Engr 241-R125

Engr 241-R126 Same as GMAW but electrode is tubular and filled with flux. Automatic feeding of wire (like GMAW). Uses no external gas source Fast growing Thin to thick sections. Can be automated (robotics), DC, medium cost. Flux Cored Arc Welding (FCAW)

Engr 241-R127

Engr 241-R128

Engr 241-R129 For welding butt joint edges vertically in one pass. Metal deposited between two pieces joined – space enclosed by copper shoes sliding upward with weld Also around pipe 1/2” to 3” thickness. Usually automated, High equipment cost. For welding bridges, pipes, tanks, ships Electrogas Welding

Electrogas - use shielding gas - flux cored wire fed in joint arc maintained between electrode and weld

Engr 241-R131 Electro-slag Welding Similar to EGW. Weld begins at part bottom, molten slag extinguishes arc. Heat then produced continuously by elect. Resist. of molten slag Very thick sections - 2” to 36”. High cost of equipment.

Vertical joint - arc started between electrode & bottom

Engr 241-R133 Electrodes Strength of deposited metal. Type of coating. Size (1/16 to 5/16 in diameter).

Engr 241-R134 Electrode Classifications E6011-A1 E - arc welding electrode 60 – 60,000 psi min. tensile strength 1 – next to last digit – position 11 – last two digits together, type of covering and current to be used A1 – alloying elements

Engr 241-R135 Clay like material. Silica binders and powdered materials (Oxides, carbonates, fluorides, metal alloys, cellulose) Electrode Coatings

Engr 241-R136 1.Stabilize the arc. 2.Generate a gas shield. 3.Control rate at which the electrode melts. 4.Act as a flux to protect weld (from oxidation). 5.Add alloying elements to joint ie. Protect from becoming brittle). Electrode Coatings (Cont.)

Engr 241-R137 Arc Welding (Non- Consumable Electrode) Gas Tungsten-Arc Welding (GTAW) Plasma Arc Welding (PAW)

Engr 241-R138 Gas Tungsten-Arc Welding (GTAW) Formerly TIG (Tungsten Inert Gas). Shielding gas is supplied from an external source. Argon or helium (high cost). Filler metal is supplied from filler wire. Tungsten electrode is not consumed.

Engr 241-R140 GTAW-NCE (Cont.) Good for thin parts, high quality welds. Used for welding aluminum, magnesium, titanium, and refractory metals. all positions, AC-DC, medium distortion, portable equipment, medium cost of equipment.

Engr 241-R141 Plasma Arc Welding Argon and helium. Arc is hot ionized gas (60,000 degrees °F). Transferred- workpiece is part of circuit. Non-transferred- Arc between tungsten electrode and nozzle. High energy, deep penetration, stable arc, less thermal distortion, high speed, > ¼” thick material, high skill, medium cost of equipment.

Separate shielding gas protects the welding or cutting process

Resistance Welding Processes Spot Seam Projection Stud Flash Engr 241-R143

Engr 241-R144 1.) Resistance Spot Welding Uses pressure and resistivity of parts to form nugget. Must be clean but not oxide free Used for sheet metal parts

Spot - most common

Two pieces fused with small nugget

Engr 241-R147 2.) Resistance Seam Welding Like spot welding but with rollers. Continuous or “roll spot welding”.

two wheeled electrodes travel over metal - current passes through them

can produce intermittent seam of overlapping spots for leak proofing

Seam welding I-Beams

Engr 241-R151 3.) Resistance Projection Welding High elect resistance developed at joint by embossing projections on surfaces to be welded

form projections with dies

current passes through two pieces and is concentrated at bumps

Engr 241-R154 4.) Resistance Stud welding Similar to flash welding Threaded rod or hanger welded to flat plate

Stud no drilling or punching holes in structure

Engr 241-R156

Engr 241-R157 5.) Resistance Flash welding Also Called “Upset Welding” Heat generated from arc as ends of two bars or sheets begin to make contact and develop an electrical resistance at the joint After heating occurs and metal softens, an axial force is applied.

generally used to weld the butt ends of two pieces

parts are held in two clamps with ends together

high current passed between them high resistance causes small arcs to occur between uneven surfaces

adv: fast and no pre - cleaning of surfaces

Engr 241-R162 Solid State Welding Processes in which joining takes place without fusion of the workpiece, thus no liquid (molten) phase is present in the joint. Clean surfaces in atomic contact under pressure and maybe heat (increases diffusion) form bonds and produce a strong joint.

Engr 241-R163 Solid State Welding Cold Welding Ultrasonic Welding Friction Welding Explosion Welding

Engr 241-R164 1.) Cold Welding Surfaces degrease, wire brush, or wiped to remove oxide smudge. Roll bonding or hot roll bonding (cladding). Processes takes advantage of materials solubility (soft, ductile materials)

Tool can be hand, pneumatic, or hydraulic dies must be designed to impose proper pressure for different metals

Engr 241-R166 2.) Ultrasonic Welding Sonotrode oscillates kHz Contact causes plastic deformation. Temperature is 1/3 to 1/2 of melting temperature (except in plastics). Suited for metallic dissimilar metals and non-metallic materials (thin parts). Can use roll transducer for seams.

UT spot welds

UT seam welds with lateral drive rollers

Engr 241-R169 3.) Friction welding One component rotates at high speed while other is stationary. Pressure contact causes heating. Part must be stopped fast to avoid shearing weld. Wide variety of materials, good joint strength Solid bars up to 3” & tubes up to 10”. Surface speed 3000ft/min. Automated, low skill, high machine cost.

Friction welding

Engr 241-R171 4.)Explosion Welding Pressure generated by detonating a layer of explosive placed over one of the components. Causes wavy interface and cold pressure welding by plastic deformation. Good bond strength. Clad dissimilar metals.

“Other” High Energy Welding Processes involves concentrating a lot of energy on a small spot produces deep narrow welds two processes include: Electron beam LASER beam Engr 241-R173

Engr 241-R174 Electron beam welding (EBW) Electrons-focused, Vacuum required. High quality welds, very expensive equipment

Engr 241-R176 Laser Beam Welding (LBW) Focused laser Good quality, little distortion, good strength, ductile, non-porous. Automated, high equipment cost.

Cutting Engr 241-R178

Engr 241-R179 Oxyfuel Gas Cutting Cuts mostly by oxidation For ferrous metals Rough surface, high distortion, can cut underwater.

Cutting

Alignment of torch tip orifices with the kerf one orifice should proceed and one should follow the cut

Engr 241-R182 Plasma Arc Cutting (PAC) Highest temperatures Rapid cutting, good surface, narrow kerf, popular with Robotics/Flexible automation

Separate shielding gas protects the welding or cutting process

Transferred vs. Non Transferred Arc

Engr 241-R185 Lasers & Electron Beam Cutting Accurate Wide variety of material Good surface, narrow kerf.

Engr 241-R186 Brazing, Soldering, Adhesive Bonding, and Mechanical Fastening Processes

Engr 241-R187 Brazing Characteristics filler metal is placed at or between the faying surfaces to be joined. temperature is raised to melt the filler metal but not the work piece. Above 840 deg F. surface should be cleaned. Flux prevents oxidation. removes films from work piece surfaces.

Engr 241-R188 Soldering Characteristics solder fills joint by capillary action. use of soldering irons, torches, ovens. lower temperature than brazing. (below 840) Copper, Silver and Gold are easy to solder while Aluminum and stainless steels are not.

Engr 241-R189 Flux Inorganic acids or salts Zinc ammonium chloride solution- cleaning. Remove afterward to avoid corrosion. Non-corrosive resin based fluxes Electrical application.

Engr 241-R190 Adhesive Classifications Chemically reactive Pressure sensitive Hot Melt Evaporative or diffusion Film and tape Delayed tack Electrically and thermally conductive

Engr 241-R191 Adhesives Advantages Interface gives strength, sealing, insulation, electrochemical corrosion from dissimilar metals, reduces vibration and noise. Distributes load, gives structural integrity (no holes), improved appearance. Good for thin, fragile, and porous parts. Limited distortion because of low temperature.

Engr 241-R192 Service temperatures. Possibly long bonding time. Great care in surface preparation. Difficulty in testing bonded joints nondestructively. Limited reliability of adhesively bonded structures during service life. Adhesives Limitations

Engr 241-R193 Mechanical Fastening Characteristics Ease of manufacture. Ease of assembly and transportation. Ease of disassembly, maintenance, replacement or repair. Ease on creating designs for movable joints (hinges, sliding mechanisms, adjustable components, fixtures). Lower over all cost of manufacture of the product.

Engr 241-R194 Mechanical Fastening Methods Threaded fastener. Rivets. Metal stitching or stapling. Seaming. Crimping. Snap-in fasteners. Shrink & Press fit.

Engr 241-R195 Thermoplastic Joining External heat sources Hot air, gasses, elect resist, lasers Internal heat sources Ultrasonic, Friction

Engr 241-R196 Thermoset Welding Threaded or molded inserts Mechanical fasteners (self tapping screws) Solvent bonding