1. Non-Arc Welding Processes Continued

2. Lesson Objectives When you finish this lesson you will understand: High Energy Density Welding, Advantages and Disadvantages Soldering and Brazing Systems Plastics Bonding Adhesive Bonding Learning Activities 1.Look up Keywords 2.View Slides; 3.Read Notes, 4.Listen to lecture 5.Do on-line workbook 6.Do homework Keywords: Laser Beam Welding (LBW), Electron Beam Welding (EBW), Plasma Plume, YAG, Soldering, Brazing, Flux, Wave Soldering, Hot Plate Welding, Hot Gas Welding, Vibration Welding, Ultrasonic Welding, Thermoplastic, Thermoset, Adhesive Bonding, Curing Non-Arc Welding Processes (Cont.)

3. Non-Arc Welding Processes Resistive heating, chemical reactions, focused light and electrons, sound waves, and friction can also be used to join materials –Resistance welding –Oxy-Fuel Welding –Friction welding (&Solid State) –Laser and electron beam welding –Brazing and soldering –Plastics joining –Adhesive bonding Introduction

4. High Energy Density Processes Focus energy onto a small area Laser –CO 2 gas: fixed position –Nd-YAG crystal: fiber-optic delivery Electron Beam High Energy Density Processes

5. These processes focus the energy onto a small area Laser - 0.0001-inch thick stainless steel sheet Electron Beam - 0.030-inch weld width on 0.5 inch thick steel plate 0.1.1.2.1.T2.95.12

6. Laser Beam Welding (LBW) 0.1.1.2.1.T3.95.12 Laser

7. Laser Beam Welding (LBW) Single pass weld penetration up to 3/4” in steel Materials need not be conductive No filler metal required Low heat input produces low distortion Does not require a vacuum Keyhole welding Laser beam Plasma plume Molten material shielding gas nozzle (optional) workpiece motion Plasma keyhole High Energy Density Processes

8. Focusing the Beam Heat Surface Welding Cutting treatmentmodification High Energy Density Processes

9. Advantages Single pass weld penetration up to 3/4” in steel High Travel speed Materials need not be conductive No filler metal required Low heat input produces low distortion Does not require a vacuum 0.1.1.2.1.T4.95.12

10. Limitations High initial start-up costs Part fit-up and joint tracking are critical Not portable Metals such as copper and aluminum have high reflectivity and are difficult to laser weld High cooling rates may lead to materials problems High Energy Density Processes

11. Electron Beam Welding (EBW) 0.1.1.2.1.T6.95.12 EB Applications

12. Electron Beam Welding (EBW) Deepest single pass weld penetration of the fusion processes –14-inch-thick steel Fast travel speeds Low heat input welds produce low distortion High Energy Density Processes Advantages

13. Limitations High initial start-up cost Not portable Part size limited by size of vacuum chamber Produces x-rays Part fit-up is critical High cooling rates may lead to materials problems High Energy Density Processes

14. Turn to the person sitting next to you and discuss (1 min.): In laser welding, materials with high reflectivity reflect the beam right off the surface and no heat is absorbed and thus they are difficult to weld. What might we do to make these high reflectivity materials more weldable?

15. Non-Arc Welding Processes Resistive heating, chemical reactions, focused light and electrons, sound waves, and friction can also be used to join materials –Resistance welding –Oxy-Fuel Welding –Friction welding (&Solid State) –Laser and electron beam welding –Brazing and soldering –Plastics joining –Adhesive bonding Introduction

16. Brazing (B) and Soldering (S) In these processes, the base metals are heated but do not melt; only the filler metal melts –Brazing filler metals having a melting point above 840° F (450°C) –Soldering filler metals have a melting point below 840°F (450°C) Brazing and Soldering

17. 0.1.1.2.4.T18.95.12

18. Application of Low Thermal Expansion Alloys Thermal expansion mismatch in metal- ceramic joints can lead to cracks in the ceramic Thermal expansion coefficients at 25°C (10 -6 mm / mm·°C) –Alumina, 8.8 –Nickel, 13.3 –Iron, 11.8 –Kovar, 5.0 Alumina substrate Kovar lid Silicon chip Brazed joints 0.1.1.2.4.T20.95.12

19. Brazing Specifications AWS A5.8 Specification for Brazing Filler Metal –8 well-defined groups (B) plus a vacuum grade (BV) BAg-1(44-46 Ag, 14-16 Cu, 14-18 Zn, 23-25 Cd) BAu-1(37-38 Au, remainder Cu) BCuP-1(4.8-5.2 P, remainder Cu) –Standard forms: strip, sheet, wire, rod, powder –Joint design tolerances, generally ~ 0.002 - 0.006 inches –Uses for each braze material AWS C3.3 Standard Method for Evaluating the Strength of Brazed Joints Brazing and Soldering

20. Balchin & Castner, “Health & Safety…”, McGraw Hill, 1993

21. Advantages Joins unweldable materials –Base metals don’t melt –Can be used on metals and ceramics Joined parts can be taken apart at a later time Batch furnace can easily process multiple parts Portable when joining small parts Brazing and Soldering

22. Limitations Joint tolerance is critical Lower strength than a welded joint Large parts require large furnaces Manual processes require skilled workers Flux Filler metal ring surrounded by flux Brazing and Soldering

23. Turn to the person sitting next to you and discuss (1 min.): Why is joint tolerance so critical? What happens if the joint space is too large? What happens if the joint space is too small? Turn to the person sitting next to you and discuss (1 min.): What happens if we do not have sufficient flux?

24. Non-Arc Welding Processes Resistive heating, chemical reactions, focused light and electrons, sound waves, and friction can also be used to join materials –Resistance welding –Oxy-Fuel Welding –Friction welding (&Solid State) –Laser and electron beam welding –Brazing and soldering –Plastics joining –Adhesive bonding Introduction

25. Joining Plastics Polymer - a single building block (mer) is repeated to form a long chain molecule –Thermoplastic polymers soften when heated, harden when cooled 2-liter bottles –Thermosetting polymers don’t soften when heated Car tires, caulking compound HHHH HHHH C=C H -C-C- H ··· add H 2 O 2 (Poly)ethylene Welding of Plastics

26. Joining of Plastics Plastic (polymer) is a material in which single building blocks (mers) join to form a long chain or network molecule Thermoplastic polymers soften when heated and harden when cooled –Foam cups (polystyrene), 2-liter bottles (polyethylene), Leisure suits (polyester) Thermosetting polymers become permanently hard when heat is applied and do not soften upon subsequent heating –Car tires (isoprene, isobutene), Epoxy, Caulks (silicones) 0.1.1.2.5.T22.95.12

27. Hot Plate, Hot Gas, Infrared Advantages –Provide strong joints –Reliable –Used on difficult to join plastics Limitations –Slow –Limited temperature range 0.1.1.2.5.T23.95.12

28. Hot Plate, Infrared Welding Hot plate welding Welding of Plastics

29. Hot Gas Welding Thermoplastics (hotmelts) –Adhesive is heated until it softens, then hardens on cooling Hot gas softens filler and base material Filler is pulled or fed into the joint Welding of Plastics

30. Vibration Advantages –Speed –Used on many materials Limitations –Size –Requires fixturing –Equipment costly 0.1.1.2.5.T24.95.12

31. Ultrasonic Advantages –Fast –Can spot or seam weld Limitations –Equipment complex, many variables –Only use on small parts –Cannot weld all plastics 0.1.1.2.5.T25.95.12

32. Turn to the person sitting next to you and discuss (1 min.): Make a list of some thermoplastic items you have recently seen that have been wlded.

33. Non-Arc Welding Processes Resistive heating, chemical reactions, focused light and electrons, sound waves, and friction can also be used to join materials –Resistance welding –Oxy-Fuel Welding –Friction welding (&Solid State) –Laser and electron beam welding –Brazing and soldering –Plastics joining –Adhesive bonding Introduction

34. Adhesives Thermosets form long polymer chains by chemical reaction (curing) –Heat is the most common means of curing –Ultraviolet light, oxygen - acrylics –Moisture - cyanoacrylates Thermoplastics (hotmelts) –Adhesive is heated until it softens, then hardens on cooling -Polyethylene, PVC 0.1.1.2.6.T26.95.12

35. Curing of Adhesives Thermosets form long polymer chains by chemical reaction (curing) –Heat (epoxy) –Ultraviolet light, oxygen (acrylics) –Moisture (superglue) Adhesive Bonding

36. Stress Modes - Best to Worst 4. Peel 5. Cleavage 2. Shear1. Compression3. Tension 0.1.1.2.6.T29.95.12

37. Why Adhesive Bonding? Dissimilar materials –Plastic to metal Materials that can be damaged by mechanical attachments Shock absorption or mechanical dampening Laminate structures –Skin to honeycomb structure Adhesive Bonding

38. Adhesive Selection Adhesive selection is based primarily on –Type of substrate –Strength requirements, type of loading, impact requirements –Temperature resistance, if required Epoxy Cyanoacrylates Anaerobics - metals Urethanes Silicones Pressure sensitive adhesives (PSAs) Adhesive Bonding

39. Factors that Influence Process Selection Material joining needs Capabilities of available processes Cost Environment Required welding speed Skill level Part Fit-up Process Selection

40. Advantages Joining dissimilar materials - plastic to metal Materials that can be damaged by mechanical attachments Blind joints Shock absorption or mechanical dampening Temporary alignment Laminated structures Thin substrates - skin-to-honeycomb construction Stress distribution 0.1.1.2.6.T27.95.12

41. Limitations Adhesives don’t do work, they distribute work; they are not structural materials Environmental degradation –Temperature –Oxidation Difficult to repair Curing or setting time Surface preparation Adhesive Bonding

42. Do Homework Assignment 3 on “More Welding Processes” and Turn in by next class period.