Welding Technology - Davis & Company, Ltd. Marine ...daviscoltdweb.com/Engineering/documents/PDFs...

Welding Technology

Chris Barry

IBEX 2003 Session 405

3:00 PM February 6, 2003.

2IBEX 2003 Session 405 3:00 PM February 6, 2003

The opinions expressed are those of the author and do not reflect official policy of the Coast Guard.

IntroductionnWhat is Really ImportantnGoalsn Processes And EquipmentnQuality Controln Automation And Other Aidsn Design For Good Weldingn Distortion Control And Correctionn Using Distortion - Line Heatingn Sizing Weldmentsn Resources



What is Really Important (In Life)n When loved ones come home,

always run to greet them like they've been gone for a year.

n Let others know when they've invaded your territory.

n Take naps, run, romp, and play daily.

n No matter how often you're scolded, don't buy into the guilt thing and pout. Run right back and make friends.

n Avoid biting when a simple growl will do. n Delight in the simple joy of a long walk. n Be loyal but never pretend to be something you're not. n Never trust anyone until you sniff ...

From: Bird Dogs Forever



Goalsn Better Product At Lower Cost

$ Improve Quality $ Reduce Rework$ Reduce And Improve Labor

n Select The Right Process, Equipment, Materialsn Understand / Eliminate Causes of Bad Weldsn Make Welding Easier and Fastern Control And Correct Distortionn Form Metal Easily With Minimum Equipment



Ductility And Stress Concentrationn Metals Are Ductile Due To Shearn Dislocations Travel Through

Metal, Requires Low Energyn Like Moving A Carpet By

Moving A Humpn Triaxial Stress Restrains Shear

Prevents Ductilityn Triaxial Stress n Weld Shrinkagen Stress Concentration - One Sided

Forces Cause Triaxial Stresses



Processes And Equipmentn Arc Weldingn SMAW - “Stick” (Steel Only)n FCAW - “Innershield” (Steel Only)l GTAW - “TIG” (Steel And Aluminum)l GMAW - “MIG” (Steel And Aluminum)

nOtherl EXW - Explosive (Steel And Aluminum)l IW -Induction (Steel And Aluminum)l LBW - Laser (Steel And Aluminum)



SMAW - “Stick” n Steel Onlyn Low Cost: Equipment, Consumables, No Gasn Very Versatilen Slower - Changing Electrodes, ChippingnGood Labor Base, But High Skill LevelnWide Range Of Electrodes For Special Usesn Pipe Rods, “Jet Rods”, Special Alloy Rods, n Gravity Fed Electrodesn Try It - You May Like It



FCAW - “Innershield”n Steel OnlynWith or Without Shielding Gasn Combination of Gas And Core Allows Lots Of

Variations in Alloys, Chemistryn Equipment Is Common Now, Relatively CheapnGood For Thin Material (Thin Wire)n High Productivityn Easy To Usen Helps With DistortionnGood Candidate To Improve Productivity



GTAW - “TIG” (Steel And Aluminum)l Steel Or Aluminum (Cu, Ti, SS, Etc.)l Argon or Helium Shieldl Slow, Difficult Skilll Distortionl Limited Applicationl Pipingl Handrails, Etc.l Small JointslWeld Repair

l Worth Having One Setup



GMAW - “MIG” (Steel And Aluminum)l Steel Or Aluminuml Gas Chemistry (Argon, Helium, CO2, O2)l Less Variability In Wire Choicel Even In Steel, Quality Wire Is Worth It

l Short Circuit TransferlGlobular Transferl Spray Transferl Reduced Spatter, Better Out Of Positionl Requires Higher Current (Gas Chemistry)

l Pulsed - Intermittent Spray Transfer



Other (New) Technologiesl EXW - Explosive / High Pressure Weldingl “Detacouple” Joins Incompatible AlloyslMaterials Qualified to MIL-J-24445

l IW - High Frequency Current & Pressurel Joining Stiffeners to Platel Done In Special Machine

l LBW - Laser Weldingl Here Today - Lots More Tommorowl Hybrid Technique + MIG To Add Filler



Quality Controln Certification of Process, Weldor, Consumablesn Control of Parent Materials And Consumablesn Dry, Clean Plates

n Construction or Weld Thru Primersn Aluminum - Watch Water Contamination

n Dry, Clean Gases (No Air Leaks), Wire, Electrodes,n Test Weldors W/ Processes They Use, Keep Recordsn ISO Certificationn Weldors Aren’t Certified - The Whole Process Is

n Inspect Weldsn Weldors Should Inspect Their Own Work



Automation And Other Aidsn Weld Pacers: Simple, Cheap, No Programmingn Panel Line, Especially To Seam Plates

n Robotic Welding: Expensive, Programmingn Specialized Setups - Panel Line Plusn Special Uses - Tight Spacesn Derive Weld Path Data Automatically From The

CAD/CAM Product Modeln Positioning Equipment To Weld Downhandn Modular Constructionn Roll The Whole Boat



Design For Good Weldingn Locate Welds For Stressn Aluminum Welds And HAZ Are Weaker

Than Parent Metaln Accessibilityn Important With MIG, Especially Spool-On-Gun

n Downhand Position If Possiblen Balanced Thicknessn Enough Metal At Weld Not To

Burn Away - Seal Weld Linen Welds Shouldn’t Meet



How Distortion Worksn In Parent Metal:n Metal Near Weld Heats, Expands, Gets Softn Is Restrained By Cold Parent Metaln Lump Forms Out Of Plane, Cools, Hardens, n Since Some Metal Is In The Lump It Shrinks

n In Weld Metal:n Liquid Metal Is Cast Into Controlled (Or Even Expanded

- Due To Heat - Space)n Fills Space, Cools, Hardens, Shrinks

n Weld And Adjacent Material Shrink



Top Ten Rules For Distortionn 1 - Don’t Over Weldn 2 - Don’t Over Weldn 3 - Don’t Over Weld n 4 - Don’t Over Weldn 5 - Don’t Over Weldn 6 - Don’t Over Weldn 7 - Don’t Over Weldn 8 - Don’t Over Weldn 9 - Don’t Over Weldn 10 - Don’t Over Weld



Controln Sequence n Backstep Sequence - Reduces Distortion 47%n Symmetrical Sequence P/S, Fore & Aft, Etc.

n Center Welds About Neutral Axisn Pre-Bending, Allow For Shrinkagen Jigging To Restrain Shrinkagen Minimize Heat Into Weldn Fast Traveln High Deposition Ratesn Downhand Welding If Possible

n Minimize Welding: Flange, Intermittent Welding



Correctionn Welds Will Always Show Through A Bit Due To

Thickening IWO Weld Heat - Grindn Apply Heat (Steel Only)n Apply Counteracting Welds (X’s & O’s)n Note That X’s & O’s Are Meeting Welds

n Stiffener / Frame Creasing (Hungry Horse)n Heat Or Weld Opposite Sides

Pulls In opposite Directionn Remember That The Fillet Weld Also Shrunk

The Plate Edges - Get Rid Of Excess Metaln Tipping, Bending And Twistingn Release Restrain, Heat, Apply Force



Using Distortion - Line Heatingn We Can Use Heat To Form (Steel Only)n Very Good For Forming Double Plates

n Gradual Process, Very Accuraten Very Good For Accuracy Control (Joining Modules)

n Simple Equipmentn Concentrated Heat - Cutting Torch Tip (Oxygen OFF!)n Water Hose or Compressed Air With Water Aspirator

n Apply Restraint To Counter Initial Expansionn Speed of Travel Controls Bending or Shrinkagen Use Sight Templates To Control Shapen CAD/CAM Software Provide Templates Automatically



Line Heating Fundamentals“When You’re Given A Lemon, Make Lemonade” - Ann Landers

n Heat Expands Metaln Metal Softens,n Is Restrained By

Adjacent Cold Material n Increases In Thicknessn Cools, Solidifies, Shrinksn Metal Pulls In To

Make Up Lost Volumen Fast Travel, More Bendingn Slow Travel, More Shrinkage

(Use For Double Curving)Hashimoto & Fujishiro, “Line Heating …”The SNA of Japan, 1961



Photos Courtesy Lou Chirrilo, IHI (Japan),NSNet, (http:www.nsnet.com)National Shipbuilding Research Program



English Wheel - For Aluminumn Can’t Use Line Heating On Aluminumn Heat Reduces Strength Properties, Low Melting Point

n Do The Opposite - Stretch The Metal By Pushing In n Easy To Get Enough Pressure - Push On Small Arean Use Spherical Pressure Pointn Double Curved Wheel On One Siden Cylindrical Wheel As Supportn Roll Metal Between Wheels - Lines Of Expansionn Use Sight Templates - Just Like Steeln CAD/CAM Software Can Acount For Shrinkage Or

Expansion & Direction Of Distortion Field



Photos CourtesyGraham Radford Yacht Design PO Box 1155Brookvale NSW 2100 Australia



Sizing Welding Jointsn Simple Process - Use Standard Formulas For Bracketsn Treat Line Of Weld Same As Section Properties n Look At Shear In Beam (Intermittent Welds)n Class Rules, NAVSHIPS 0900-060-401,

Blodgett; “Design Of Welded Structures”n Continuous Weldsn Steel In Weather (Seal With Fillers?)n Vibration Or Shock (Under Engines)n At Radius Of Welded On Flanges

Forces Change Directionn Avoid Welding “For Decoration”



Resourcesn www.sname.org

n Marine Technologyn Journal Of Ship Productionn Ship Production Symposiumn T&R Panels

n Ship Structures Committeen ASTM / ISO / IACS Standardsn NSRP: www.USAShipbuilding.com, www.nsnet.com n AWS: www.aws.orgn ShipConstructor: www.albacoreresearch.comn MAESTRO: www.proteusengineering.comn Books, Videos, Magazines, Awards: www.lincolnelectric.comn Welding Design & Fabrication: www.penton.com/n FMA: www.thefabricator.com; PMA:www.metalformingmagazine.comn AISC: www.modernsteel.comn Yahoo Group: Tinboats ([email protected])



ReviewnGoalsn Processes And EquipmentnQuality Controln Automation And Other Aidsn Design For Good Weldingn Distortion Control And Correctionn Using Distortion - Line Heatingn Sizing Weldmentsn Resources

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