industrial processes ii industrial processes ii inden 3313 lecture 5 --introduction to joining...

Industrial Processes II

INDUSTRIAL PROCESSES IIINDUSTRIAL PROCESSES II

INDEN 3313INDEN 3313

Lecture 5 --Introduction to Lecture 5 --Introduction to Joining Processes, Welding Joining Processes, Welding

Metallurgy, Combustion and Metallurgy, Combustion and Electrical Welding Processes Electrical Welding Processes


OVERVIEWOVERVIEW• Introduction to WeldingIntroduction to Welding

• Welding MetallurgyWelding Metallurgy

• Welding ProcessesWelding Processes– Combustion Processes


QUESTIONSQUESTIONSTO START ??TO START ??


INTRODUCTION TO JOININGINTRODUCTION TO JOINING• DefinitionDefinition

– “Joining is an all-inclusive term, covering processes such as welding, brazing, soldering, adhesive bonding, and mechanical fastening”. [Kalpakjian, p. 855]

• Why Used?Why Used?– Difficult/Impossible to Manufacture as a Single

Piece– Easier/More Economical to Manufacture as

Components and then Assemble Either In-Plant, On-Site, or By Customer.

– (May) Allow Disassembly for Maintenance/Repair– Different Components Enable Different Properties

at Different Places on Assemble (e.g., Wear Surfaces)


INTRODUCTION TO JOINING INTRODUCTION TO JOINING PROCESSESPROCESSES

• Welding (Definitions)Welding (Definitions)– Metal Joining Process in Which Coalescence is

Obtained Using Heat and/or Pressure• Coalescence - (From The Random House Dictionary)

– 1. to grow together or into one body 2. to unite so as to form one mass, community, etc.; blend; fuse; join; 3. to cause to unite into one body. from the Latin “alere” meaning to grow.

– A Metallurgical Bonding Accomplished by the Attracting Forces Between Atoms

– Joining Two (or More) Pieces of Material by Applying Heat, Pressure, or Both, With or Without Filler Metal to Produce Localized Union Through Fusion or Recrystallization Across the Interface.


INTRODUCTION TO JOINING INTRODUCTION TO JOINING PROCESSESPROCESSES

• Welding - Key Elements in DefinitionsWelding - Key Elements in Definitions– “Pieces of Material” -- Same Material

Throughout– “Grow”, “Recrystallization” -- Grain Growth in

Joint– “Localized Union” -- Restricted Area/Volume

• Joint Types and Configurations– “Uses Heat and/or Pressure” -- Energy Required

to Achieve Coalescence • This Provides Basis for Process Classification and

Naming• Heat Sources -- Chemical, Electrical, Thermal,

Mechanical

• Why Use?Why Use?– Strong, Permanent Joints


WELDING -- BASIC PROCESSWELDING -- BASIC PROCESS

• Part/Weld Function and Operating Part/Weld Function and Operating Environment is DefinedEnvironment is Defined

• Type of Joint Selected/AnalyzedType of Joint Selected/Analyzed• Component Parts ManufacturedComponent Parts Manufactured• Surfaces to Be Welded Are CleanedSurfaces to Be Welded Are Cleaned• Components Are Aligned and Components Are Aligned and

ClampedClamped• Non-Corrosive/Protective Non-Corrosive/Protective

Environment Formed Around Area to Environment Formed Around Area to Be WeldedBe Welded


WELDING -- BASIC PROCESSWELDING -- BASIC PROCESS• Heat and/or Pressure Applied to Heat and/or Pressure Applied to

ComponentsComponents• Portion of Each Component MeltsPortion of Each Component Melts

– Temperature of Fusion Reached, Maintained

– Slag Produced

• (Optional) Add Molten (Filler) Material(Optional) Add Molten (Filler) Material• Heat From Process Affects Non-Melted Heat From Process Affects Non-Melted

Portion of ComponentsPortion of Components– Grain Structure Affected– Expansion, Warping– Out Gassing, Corrosion


WELDING -- BASIC PROCESSWELDING -- BASIC PROCESS• Heat and/or Pressure RemovedHeat and/or Pressure Removed• Molten Material Begins to SolidifyMolten Material Begins to Solidify

– Coalescence/Grain Formation• Size, Shape, Strength Function of Cooling

Rate

– Dissolved Gases Evolve• Out Gassing,

– Shrinkage/Expansion of Weld Nugget Due to Change in State• Stresses, Shrinkage Voids

• Solidification Of Molten Material Solidification Of Molten Material CompleteComplete


WELDING -- BASIC PROCESSWELDING -- BASIC PROCESS• Weld Nugget, Components Cool to Weld Nugget, Components Cool to

Room TemperatureRoom Temperature• Non-Corrosive/Protective Non-Corrosive/Protective

Environment WithdrawnEnvironment Withdrawn• Weld is CleanedWeld is Cleaned• Weld is Inspected/Tested/ApprovedWeld is Inspected/Tested/Approved• Paint or Other Coating AppliedPaint or Other Coating Applied• Assembly is UsedAssembly is Used

– Corrosion– Loading, Stress, Fatigue


WELDING METALLURGYWELDING METALLURGY

• Melting/Fusion Process Similar to Melting/Fusion Process Similar to Casting and Heat TreatingCasting and Heat Treating

• Casting ReviewCasting Review– Crystalline (Grain) Growth, Dendrites– Factors Affecting Grain Size, Shape

• Heat Treatment ReviewHeat Treatment Review– Annealing– Normalizing– Grain Growth



• The Welded Joint (Heat Dissipation)The Welded Joint (Heat Dissipation)

[Kalpakjian, Figure 29.1, p. 909]

QQ



• The Welded Joint (Heat Flow - The Welded Joint (Heat Flow - Dendrites)Dendrites)




• The Welded JointThe Welded Joint




• Solidification of the Weld MetalSolidification of the Weld Metal– Solidification Rate and Hardness

Kalpakjian, Figure 29.3b, p. 910]



• Phase DiagramPhase Diagram

Kalpakjian, Figure 29.4, p. 911]



• Heat Affected Zone (HAZ)Heat Affected Zone (HAZ)

Niebel, et al, Figure 14.2, p. 629]


FACTORS AFFECTING WELD FACTORS AFFECTING WELD QUALITYQUALITY

• Joint DesignJoint Design

• Process UsedProcess Used

• PorosityPorosity

• Slag InclusionsSlag Inclusions

• Incomplete Incomplete Fusion and Fusion and PenetrationPenetration

• Weld Profile Weld Profile • CracksCracks

• TearsTears• Surface Surface

DamageDamage• Residual Residual

StressesStresses• AppearanceAppearance



• Joint DesignJoint Design– Definition

• Selection of the Relative Positioning of the Components to be Welded

• Controls Area of Contact (Weld Strength - Anisotropic), Accessibility to Area to be Welded (Time, Skill Requirements, Welding Method)

– Types• Single or Double • Square, ‘V’, Flare (Fillet), Bevel, ‘J’, ‘U’, ‘T’, • Corner, Edge, Butt, Lap (Overlap),



• Joint TypesJoint Types

Kalpakjian, Figure V.4, p 857]



• Joint TypesJoint Types

– Fillet (T)

– Square

(Butt)

– Bevel

– ‘V’

– ‘J’

– ‘U’



• Process ImpactProcess Impact– Temperature Applied/Reached– Heat Flux (BTU/Min)– Size of HAZ– Protective Environment Provided– Amount of Material Supplied– Cost Of Equipment– Operator Skill (Cost)– Position (Vertical,

Horizontal,Underwater, ...) Allowed



• Porosity/VoidsPorosity/Voids– Definition

• Discontinuities (Absences) in Weld Nugget

– Causes• Trapped Gasses (Out-gassing from Metal or

Flux, Smooth Spherical H2 , O2 , N)

• Shrinkage Voids (Irregularly Shaped)• High Freeze Rate• Oil, Paint, Moisture, or Rust on Base Metal• Improper Arc Length or Current• Zinc Volatilization in Copper or Galvanized

Base



• Porosity/VoidsPorosity/Voids– Cures

• Control Input Materials (Molten Materials)• Control Environment, Parameters• Control Process (Reduce Rate of

Temperature Change, Control Solidification (from Interior))

• Preheat, Pre-clean• ECuSi Electrodes (for Copper)• E6010 Electrodes (for Galvanized)


FACTORS AFFECTING WELD FACTORS AFFECTING WELD QUALITYQUALITY• Slag InclusionsSlag Inclusions

– Definition• “Foreign” (Not the Base Material) Objects

That are Trapped in the Weld Nugget

– Causes• “Tramp” Materials in Rod, Components,

Slag from Previous Pass• Corrosion or Combustion Products Trapped

in Weld Nugget (Fast Freeze)• Residual Flux Materials

– Cures• Compatibility of Rod, Component Materials• Control ‘Cleanliness’ of Workplace,

Components• Control Cooling Rates



• Incomplete FusionIncomplete Fusion– Definition

• Lack of Complete, Regular Crystalline Structure Throughout Proximate Base Material and Weld Nugget

– Causes• Incomplete Melting (Mushy Zone or

Insufficient Heat Flux)• Impurity or Void That Blocks Grain Growth

– Cures• Increase Heat Flux, Temp. Reached, Preheat• Avoid Impurities and Voids• Improve Fit



• Incomplete PenetrationIncomplete Penetration– Definition

• Weld Nugget Not ‘Deep’ Enough

– Causes• Heat Dissipation Exceeds Heat Flux (Input)

– Cures• Slow Welding Rate, Increase Heat

Flux/Insulate• Preheat Components• Weld from Both Sides (Double vs. Single

Joints)



• Weld ProfileWeld Profile– Definition

• Uniformity of Weld Cross-Section (Overlap, Under-Cut, Under-Fill)

– Causes• Insufficient Filler Material• Melt Away Base Material (esp. Vertical)• Too Slow Freeze Rate (Vertical)

– Cures• Proper Electrode/Position Combination• Proper Welding Technique, Parameters



• Electrode Notation/ParametersElectrode Notation/Parameters– E => Arc Welding (Ferrous)

– 2-3 Digits => Tensile Strength (kpsi)

– 1 Digit => Position (1=All, 2=Flat, ...)

– -Suffix => Coating Composition and Current to be Used

– e.g., E7011-C1

• See Kalpakjian, Figure 27.4, p. 870See Kalpakjian, Figure 27.4, p. 870



• Cracks (Weld Nugget)Cracks (Weld Nugget)– Definition

• Rupture or Tear (Physical Discontinuity) in Weld Nugget

– Causes• Joint Too Rigid• Excessive Alloy Pickup from Base Metals• Defective Electrodes• Poor Fit (Variance in Nugget, Shrinkage)• Bead Too Small• High Sulfur in Base Metals



• Cracks (Weld Nugget)Cracks (Weld Nugget)– Cures

• Preheat Joints (Reduce Cooling Rate)• Use Correct Polarity, Welding Speed, Current• Change Electrode• Reduce Gap• Use Larger Electrode• Use Sulfur Fixing Elements (EXX18

Electrodes)• Fill in (Filler Metal) Shrinkage Prior to

Withdrawal of Electrode (Similar to Concept of Riser in Casting)



• Cracks (Base Components)Cracks (Base Components)– Definition

• Rupture or Tear (Physical Discontinuity) in Weld Nugget

– Causes• H2 in Welding Atmosphere

• High Strength - Low Ductility Material• Hot Tears (Copper Alloys)• Excessive Stress (Expansion/Warping)• High Hardenability• High Lead Content



• Cracks (Base Components)Cracks (Base Components)– Cures

• Use Hydrogen Free Process (GMAW, GTAW, Submerged Arc)

• Change Material or Anneal• Use Electrode with Similar Melting Point

(Alloying)• Redesign Joint• Preheat, Slow Cooling Rate• Change to Lead Free Material



• Lamellar TearsLamellar Tears– Definition

• Tears or Cracking Along Grain Boundaries in Anisotropic Materials

– Causes• Directional Cooling (Dendritic Structure)• Rolled Base Materials

– Cures• Joint Redesign (Direction of Grain), Slower

Cooling, Anneal or Stress Relief• Change Materials



• Surface DamageSurface Damage– Definition

• Undesired Physical Changes to the Surfaces or the Base Materials

– Causes• Spatter (Solidified Droplets), Pitting (Arc

Strikes)• Excessive Heat (Discoloration)

– Cures• Welding Technique• Surface Rehabilitation


Factors Affecting Weld Factors Affecting Weld QualityQuality

• Residual StressesResidual Stresses– Definition

• Unrelieved Forces Remaining in the Material Due to Limited Motion of Material (Constraints)

– Causes• Differential Cross-Sections• Temperature (Size) Differentials Across

Constrained Weldment When Weld Nugget Fuses

– Cures• Redesign of Weldment, Fixturing• Preheating



• Weld Bead AppearanceWeld Bead Appearance– Definition

• Regularity/Consistency of Weld Bead

– Causes• Varying (Filler) Material Deposition/Fusion

Rates• Inconsistent Oscillation of Arc or Stick

– Cures• Improved Welding Automation or Manual

Technique


TESTING OF WELDSTESTING OF WELDS

• DestructiveDestructive– Tension– Torsion– Bend– Peel– Fracture

Toughness– Corrosion– Creep

• Non-DestructiveNon-Destructive– Visual– Sonic (Brass

Hammer)– Radiographic (X-

Ray)– Magnetic

Particle– Liquid Penetrant– Ultrasonic


QUESTIONSQUESTIONSOR OR

CLARIFICATIONCLARIFICATIONS ???S ???

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industrial processes ii industrial processes ii inden 3313 lecture 5 --introduction to joining...

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