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High Energy Beams and Related Welding and Cutting Process Principles

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Presentation on theme: "High Energy Beams and Related Welding and Cutting Process Principles"— Presentation transcript:

1 High Energy Beams and Related Welding and Cutting Process Principles
Chapter 25

2 Objectives Explain the use of high energy-density beam processes.
Describe the water jet cutting process. Describe the friction welding processes. Explain explosion welding.

3 Introduction Introduces some non-conventional welding and cutting processes Processes evaluated based upon distinguishing features Heat source How molten pool shielded from atmosphere Most applied in mechanized or automatic modes Require extremely accurate joint geometry and positioning

4 High Energy Beam Processes
Produce very narrow weld with very deep penetration characteristics Applied to tightly fitting joints with tolerance in inch range Table 25-1 covers capabilities of various welding processes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Comparison of electron beam weld on left (A) and gas tungsten arc weld on right (B). American Welding Society (AWS) Welding Handbook

5 Schematic Representation of Keyhold Weld
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. American welding Society (AWS) Welding Handbook

6 Electron Beam Welding (EBW)
Used for high precision and high production applications Use concentrated steam of high velocity electrons formed into beam Provides source of intense local heating Equipment consists of the following: Vacuum chamber Controls Electron beam gun Three-phase power source Optical viewing system Tracking device Work-handling equipment

7 Electric Beam Welding Electrons dispersed from electrically excited, negatively charged cathode Electron beam partially shaped by bias cup grid Electrons moving at 30–70% speed of light Beam further shaped by positive anode and magnetic focusing lens (0.04 inch in diameter) Electrons bombard metal causing rapid buildup of heat; vapor hole produced surrounded by molten metal that will form weld

8 Electron Beam Welding Three variations based on degree of vacuum used
High vacuum (EBW-HV) referred to as hard vacuum and utilizes pressure of 1 x 10-3 torr Medium vacuum (EBW-MV) utilizes pressure of 2 x 10-1 torr Nonvacuum (EBW-NV) pressure of 760 torr Torr: accepted industry term for pressure of 1 millimeter of mercury Standard atmospheric pressure = 760 torr

9 American Welding Society (AWS) Welding Handbook Committee, 2001,
Welding Science and Technology, Volume 1 of Welding Handbook, 9th ed., Miami; American Welding Society, Fig 1.34, p. 30 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10 Basic Modes of Electron Beam Welding
American Welding Society (AWS) Welding Handbook Committee, 1991, Welding Process, Volume 2 of Welding Handbook, 8th ed., Miami; American Welding Society, Fig 21.3, p. 676 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11 Advantages of Electron Beam Welding
Directly converts electric energy into beam energy, so process very efficient Depth-to-width ratios for one-pass welding on thick sections high Heat input very low Narrow heat-affected zone Minimal distortion Vacuum mode results in high purity welds

12 Advantages of Electron Beam Welding
Beam can be projected over distances in vacuum Rapid travel speeds Beam can be magnetically deflected to produce various weld shapes Fig. 25-3B Beam has long focal length, so it can tolerate broad range of work distances Dissimilar metals can be welded High thermal conductive metals like copper can be welded

13 Beam Deflection Capability of an EBW Beam as Shown by a “Bow Tie” Pattern
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

14 Limitations of EBW Capital cost of equipment very high
Joint preparation very extensive Rapid solidification can cause cracking For high and medium vacuums, chamber size limitation Long time required to draw vacuum Partial penetration may have root voids and porosity

15 Limitations of EBW Beam can be magnetically deflected, so material must be nonmagnetic or demagnetized No-vacuum welding requires part to be very close to bottom of electron beam gun column Radiation shielding must be used, and X-rays produced Ventilation required to remove ozone and other noxious gases with nonvacuum mode

16 Laser Beam Welding and Cutting
Acronym for Light Amplification by Stimulated Emission of Radiation First beam produced in 1960 using ruby crystal rod Used for welding, cutting, and drilling Laser very concentrated beam of light Coherent light (light waves synchronized and travel parallel to each other Monochromatic (light has one frequency, one color)

17 Laser Beam Welding and Cutting
Laser light has ability to stay in tight column Two types Solid state Gas Can be operated continuously or pulsed Pulsing reduces heat buildup and effective for piercing and drilling applications Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18 Laser Beam Welding and Cutting
Noncontact process Light used to heat surface being focused on No physical contact of equipment with part other than beam Material being worked on does not have to be conductor Welding is melting, burning process Heat from 10 Kilowatt rated laser can weld 1/2 inch thick material at 60 inches per minute

19 Determinates in Material Thickness and Travel Speed
Part geometry Reflectivity of the materials surface Heat conductivity Vaporization point of the alloy being used Type of alloy Surface tension of the molten material

20 Laser Beam Welding (LBW)
Generally done with inert shielding gas to shield weld pool Can be used without filler metal (autogenous) or with filler metal Little distortion Highly concentrated heat source and fast travel speed

21 Laser Beam Cutting (LBC)
Accomplished by reducing spot size of beam from to inch Kerf very small Very small heat-affected zones produced Speed drops off dramatically when material approaches 1/2 inch As thickness goes up, blowouts may occur Unwanted molten metal flying out of cut Assist gas used to blow metal from kerf

22 Schematic View of Laser Cutting Operation
American Welding Society (AWS) Welding Handbook Committee, 1991, Welding Process, Volume 2 of Welding Handbook, 8th ed., Miami; American Welding Society, Fig 16.3, p. 506 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

23 Laser Beam Drilling (LBD)
Can be done on very hard materials Holes as small as inch Blowouts occur when hole diameter small in relation to thickness of material being drilled Blowout more common in continuous wave lasers than pulse wave lasers

24 Schematic Representation of Elements of an Nd: YAG Laser
American Welding Society (AWS) Welding Handbook Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

25 Laser Beam Advantages Very low heat input allowing for hermetic sealing Single-pass welds made on material up to 1-1/4 inch thick Noncontact process Beams readily focused, aligned, and directed by optical elements Very small beams used to make very small welds, cuts, or holes Dissimilar metals can be welded

26 Laser Beam Advantages Wide variety of materials can be processed
Can be readily automated for high speed work Not affected by magnetic fields Can weld on very restricted access joints Fig. 25-6 Metals with dissimilar physical properties can be processed Nonvacuum or X-ray shielding required High 10:1 depth-to-width ratios attainable Beams can be deflected for multiple uses (welding, cutting, marking, drilling)

27 Laser Beam Limitations
Joint must be very accurate Surfaces must be forced together Limitation of beam power for welding, cutting, and drilling Highly reflective materials will deflect beam Require mechanism to deal with plasma Low power conversion efficiency of <10% Rapid cool rates lead to porosity and brittleness

28 Laser Assisted Arc Welding
Hybrid application of several processes Laser beam and gas metal arc Laser beam (CO2 or Nd: YAG) combined in one weld pool with gas metal arc Allows flexibility in which materials can be joined and types of welds made by addition of filler metal Gas metal arc power determines width of weld Laser process related to formation of keyhole Determines depth of penetration and reduces ignition resistance of arc

29 Laser Assisted Arc Welding
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Idaho National Engineering and Environmental Laboratory

30 Laser Assisted Arc Welding
Idaho National Engineering and Environmental Laboratory LASER/MIG hybrid welding head designed for mounting on a robot arm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

31 Water Jet Cutting High velocity jet of water used to cut variety of materials including metals and nonmetallics Sapphire nozzle with hole from to inch has water forced through it at high pressures ranging from 30,000 to 60,000 p.s.i. Two types Uses water Kerf tapering Uses water mixed with abrasive material

32 Water Jet Cutting Process easily automated and can be used with robotic control Cuts cleanly, without ragged edges, without heat and generally faster than band saw Versatile because cuts many types of materials Narrow kerfs produced – very cost effective when cutting expensive materials Table 25-4 lists materials and cutting speeds

33 Water Jet Schematic Bold arrows indicate water flow direction. Water pressure boosted from low tap water pressure to approximately pounds per square inch. Then forced through tightly constricting orifice and exits at speeds approaching 2.5 times Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

34 Water Jet Cutting Advantages
Cold cutting (no heat-affected zones, no hardening, no cracking) Reduces dust and hazardous gases Environmentally friendly Cuts in any direction Perforates most materials without starting holes Cuts virtually any material (including food products)

35 Water Jet Cutting Advantages
Net-shape or near-net-shape parts (no secondary processing required in many applications) Minimal fixturing required Saves raw materials (small cutting kerf width, nesting capabilities) Faster than many conventional cutting tools Does not induce stresses into material while being cut Flexible machine integration

36 Water Jet Cutting Cold cutting properties main advantage
Other cutting methods burn, melt, or cause cracking in heat-affected zone Fig B Materials undergo no thermal stress Considered very environmentally friendly

37 Friction Welding (FRW)
Solid-state process using heat produced by compressive forces generated by materials rotating together in friction mode Solid-state welding group of processes producing coalescence by application of pressure at welding temperature below melting temperatures of base metal Mechanical energy converted into heat energy Used to join wide variety of dissimilar metals

38 Schematic Illustration of Friction Welding
American Welding Society (AWS) Welding Handbook Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

39 Friction Stir Welding Process variation where probe or tap with diameter of 0.20 to 0.24 inch rotated between square groove faying edges on butt joint Shouldered nonconsumable collar has smoothing effect on top surface Temperatures of 840 to 900ºF generated as tilted rotating probe travels along length of joint Stirring action heats and moves hot metal from front of probe to rear of probe creating weld

40 Schematic of Friction Stir Welding
American Welding Society (AWS) Welding Handbook Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

41 Friction Stir Welding Welding speeds up to 24 inches per minute on 0.25 inch aluminum sections typical Only material commercially welded is aluminum High quality welds with no porosity or cracks Principal advantage: parts do not need to be rotated against each other Limitation is type of metals process currently usable on

42 Explosion Welding (EXW)
Solid-state process that uses controlled detonation to impact two workpieces at very high velocity Impact and sliding forces create weld Typically done at ambient temperature Explosion deforms prime component locally and detonation progresses, prime component quickly crosses standoff distance and impacts base component Welding accomplished by plastic flow of metal pieces across faying surfaces Used to join metals that have sufficient strength to withstand detonation

43 Schematic of Explosion Welding
American Welding Society (AWS) Welding Handbook Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

44 Summary AWS defined and described over 110 various joining and cutting processes and process variations Master chart of processes shown in Figure 25-16 Processes grouped into three areas Fusion, solid-state, and brazing and soldering Further broken down to energy source, thermal source mechanical loading, shielding, and process description and abbreviation


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