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INDUSTRIAL PROCESSES II INDEN 3313

INDUSTRIAL PROCESSES II INDEN 3313. Lecture 5 --Introduction to Joining Processes, Welding Metallurgy, Combustion and Electrical Welding Processes. OVERVIEW. Introduction to Welding Welding Metallurgy Welding Processes Combustion Processes. QUESTIONS TO START ??. INTRODUCTION TO JOINING.

merrill-peterson
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INDUSTRIAL PROCESSES II INDEN 3313

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  1. INDUSTRIAL PROCESSES IIINDEN 3313 Lecture 5 --Introduction to Joining Processes, Welding Metallurgy, Combustion and Electrical Welding Processes Industrial Processes II

  2. OVERVIEW • Introduction to Welding • Welding Metallurgy • Welding Processes • Combustion Processes Industrial Processes II

  3. QUESTIONSTO START ?? Industrial Processes II

  4. INTRODUCTION TO JOINING • Definition • “Joining is an all-inclusive term, covering processes such as welding, brazing, soldering, adhesive bonding, and mechanical fastening”. [Kalpakjian, p. 855] • 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) Industrial Processes II

  5. INTRODUCTION TO JOINING PROCESSES • 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. Industrial Processes II

  6. INTRODUCTION TO JOINING PROCESSES • Welding - 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? • Strong, Permanent Joints Industrial Processes II

  7. WELDING -- BASIC PROCESS • Part/Weld Function and Operating Environment is Defined • Type of Joint Selected/Analyzed • Component Parts Manufactured • Surfaces to Be Welded Are Cleaned • Components Are Aligned and Clamped • Non-Corrosive/Protective Environment Formed Around Area to Be Welded Industrial Processes II

  8. WELDING -- BASIC PROCESS • Heat and/or Pressure Applied to Components • Portion of Each Component Melts • Temperature of Fusion Reached, Maintained • Slag Produced • (Optional) Add Molten (Filler) Material • Heat From Process Affects Non-Melted Portion of Components • Grain Structure Affected • Expansion, Warping • Out Gassing, Corrosion Industrial Processes II

  9. WELDING -- BASIC PROCESS • Heat and/or Pressure Removed • Molten 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 Complete Industrial Processes II

  10. WELDING -- BASIC PROCESS • Weld Nugget, Components Cool to Room Temperature • Non-Corrosive/Protective Environment Withdrawn • Weld is Cleaned • Weld is Inspected/Tested/Approved • Paint or Other Coating Applied • Assembly is Used • Corrosion • Loading, Stress, Fatigue Industrial Processes II

  11. WELDING METALLURGY • Melting/Fusion Process Similar to Casting and Heat Treating • Casting Review • Crystalline (Grain) Growth, Dendrites • Factors Affecting Grain Size, Shape • Heat Treatment Review • Annealing • Normalizing • Grain Growth Industrial Processes II

  12. WELDING METALLURGY • The Welded Joint (Heat Dissipation) [Kalpakjian, Figure 29.1, p. 909] Q Q Industrial Processes II

  13. WELDING METALLURGY • The Welded Joint (Heat Flow - Dendrites) [Kalpakjian, Figure 29.2, p. 910] Industrial Processes II

  14. WELDING METALLURGY • The Welded Joint [Kalpakjian, Figure 27.6, p. 863] Industrial Processes II

  15. WELDING METALLURGY • Solidification of the Weld Metal • Solidification Rate and Hardness Kalpakjian, Figure 29.3b, p. 910] Industrial Processes II

  16. WELDING METALLURGY • Phase Diagram Kalpakjian, Figure 29.4, p. 911] Industrial Processes II

  17. WELDING METALLURGY • Heat Affected Zone (HAZ) Niebel, et al, Figure 14.2, p. 629] Industrial Processes II

  18. Joint Design Process Used Porosity Slag Inclusions Incomplete Fusion and Penetration Weld Profile Cracks Tears Surface Damage Residual Stresses Appearance FACTORS AFFECTING WELD QUALITY Industrial Processes II

  19. FACTORS AFFECTING WELD QUALITY • Joint 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), Industrial Processes II

  20. FACTORS AFFECTING WELD QUALITY • Joint Types Kalpakjian, Figure V.4, p 857] Industrial Processes II

  21. FACTORS AFFECTING WELD QUALITY • Joint Types • Fillet (T) • Square (Butt) • Bevel • ‘V’ • ‘J’ • ‘U’ Industrial Processes II

  22. FACTORS AFFECTING WELD QUALITY • Process 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 Industrial Processes II

  23. FACTORS AFFECTING WELD QUALITY • Porosity/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 Industrial Processes II

  24. FACTORS AFFECTING WELD QUALITY • Porosity/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) Industrial Processes II

  25. FACTORS AFFECTING WELD QUALITY • Slag 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 Industrial Processes II

  26. FACTORS AFFECTING WELD QUALITY • Incomplete 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 Industrial Processes II

  27. FACTORS AFFECTING WELD QUALITY • Incomplete 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) Industrial Processes II

  28. FACTORS AFFECTING WELD QUALITY • Weld 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 Industrial Processes II

  29. FACTORS AFFECTING WELD QUALITY • Electrode 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. 870 Industrial Processes II

  30. FACTORS AFFECTING WELD QUALITY • 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 Industrial Processes II

  31. FACTORS AFFECTING WELD QUALITY • 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) Industrial Processes II

  32. FACTORS AFFECTING WELD QUALITY • 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 Industrial Processes II

  33. FACTORS AFFECTING WELD QUALITY • 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 Industrial Processes II

  34. FACTORS AFFECTING WELD QUALITY • Lamellar 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 Industrial Processes II

  35. FACTORS AFFECTING WELD QUALITY • Surface 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 Industrial Processes II

  36. Factors Affecting Weld Quality • Residual 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 Industrial Processes II

  37. FACTORS AFFECTING WELD QUALITY • Weld 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 Industrial Processes II

  38. Destructive Tension Torsion Bend Peel Fracture Toughness Corrosion Creep Non-Destructive Visual Sonic (Brass Hammer) Radiographic (X-Ray) Magnetic Particle Liquid Penetrant Ultrasonic TESTING OF WELDS Industrial Processes II

  39. QUESTIONSOR CLARIFICATIONS ??? Reminder : Industrial Processes II

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