1. FRICTION WELDING

2. Friction Welding Lesson Objectives
When you finish this lesson you will understand:
Continuous Drive Friction Welding & Applications
Variables Effecting Friction Welding
Variations of friction Welding Process
Dissimilar Materials Welded
Inertia Welding Process & Applications
Learning Activities
View Slides;
Read Notes,
Listen to lecture
Do on-line workbook
View Video
Keywords: Friction Welding, Inertia Welding, Forging Pressure, Orbital Friction Welding, Linear Friction Welding, Angular Reciprocating Friction Welding, Radial Friction Welding, Friction Stir Welding

3. The friction welding process is a solid state welding process where heat is imparted to the work pieces by mechanical means via the frictional rubbing of the mutual pieces together under a load and accompanied by deformation of the parts.

4. Definition of Friction Welding
Friction welding is a solid state joining process that produces coalescence by the heat developed between two surfaces by mechanically induced surface motion.
In the general case, one part is held fixed while the other is rotated. When the two parts are brought into contact, the frictional heat generated breaks down the surface asperities under the action of the load, and surface material is plastically moved out of the interface, carrying with it any surface oxide and contamination into the outside “flash” material (gray in this figure). This flash material may or may not be subsequently machined off depending upon the final use of the part.

5. Examine the Friction Weld Video on the Web Page
Link to Friction Welding Video

6. Categories of Friction Welding
Continuous drive
Inertia
There are two types of friction welding variations, continuous drive friction welding and Inertia Welding. The first uses a continuous drive motor while the other uses inertia energy stored in a flywheel to impart the frictional energy into the weldment.

7. Continuous Drive Friction Welding
One of the workpieces is attached to a rotating motor drive, the other is fixed in an axial motion system.
One workpiece is rotated at constant speed by the motor.
An axial or radial force is applied.
Workpieces
Non-rotating vise
Motor
Chuck
Spindle
Hydraulic cylinder
Brake
In continuous “direct drive” friction welding, one workpiece is attached to a rotating motor drive unit as shown above. The other workpiece is clamped in a non-rotating axial drive unit. The two workpieces are gradually brought together with one rotating and the other still. When they make contact, heat is generated at the interface due to friction. Additional axial force is applied. The axial force is raised to a final constant value and held for a predetermined time, or until a preset amount of upset takes place. The rotational driving force is disconnected, and the rotating workpiece is stopped by the application of a braking force. The axial force (forging force) is maintained or increased for a predetermined time after rotation ceases.

8. Continuous Drive Friction Welding
The work pieces are brought together under pressure for a predeter-mined time, or until a preset upset is reached.
Then the drive is disengaged and a break is applied to the rotating work piece.
Workpieces
Non-rotating vise
Motor
Chuck
Spindle
Hydraulic cylinder
Brake
Continuation of previous slide

9. Linnert, Welding Metallurgy,
AWS, 1994

10. Friction Welding Variables (Continuous Drive)
Rotational speed
Heating pressure
Forging pressure
Heating time
Braking time
Forging time

11. AWS Welding Handbook

12. AWS Welding Handbook

13. AWS Welding Handbook

14. Equipment
Direct Drive Machine
Courtesy AWS handbook

15. Questions

16. Friction Welding Process Variations

17. AWS Welding Handbook

18. Friction Welding Joint Design
Continuous Drive
Friction Welding Joint Design
The joint face of at least one of the work piece must have circular symmetry (usually the rotating part).
Typical joint configurations shown at right.
Rod
Tube
Rod to tube
Tube to disc
Rod to plate
Tube to plate

19. Orbital Friction Welding
AWS Welding Handbook

20. Angular Reciprocating Friction Welding
AWS Welding Handbook

21. Linear Reciprocating Friction Welding
AWS Welding Handbook

22. Radial Friction Welding
Used to join collars to shafts and tubes.
Two tubes are clamped in fixed position. The collar to be joined is placed between the tubes.
The collar is rotated producing frictional heat.
Radial forces are applied to compress the collar to complete welding. + F F F F F
Radial friction welding is used to weld collars to shafts and tubes. For the radial friction welding of tubes, the two tubes are clamped firmly. The collar to be joined is placed between them. The collar is rotated producing frictional heating. When heated enough by friction, radial forces are imposed along the periphery of the collar. These forces compress the collar to produce the weld. An internal expanding mandrel is often used to support the tube walls. F

23. Friction Surfacing
AWS Welding Handbook

24. Friction Stir Welding Parts to be joined are clamped firmly.
A rotating hardened steel tool is driven into the joint and traversed along the joint line between the parts.
The rotating tool produces friction with the parts, generating enough heat and deformation to weld the parts together.
Butt welds
Unlike conventional friction welding, the parts to be joined by friction stir welding are not rotated. The parts are clamped firmly in a restraining device. A rotating tool traverses along the joint line. During rotation, the tool generates frictional heating, deformation, and welding along the joint line of the workpieces. Butt joints, corner joints, T joints, and fillet-butt joints can be welded by friction stir welding.
Overlap welds

25. Friction Stir Welding Clamping force clamping force Step -1 Step -3

26. T-section ( 2- component top butt)
Friction Stir Welding
900
Corner welds
T-section ( 2- component top butt)

27. Friction Stir Welding
Fillet butt welds

28. Questions

29. Friction Welding Applications
Continuous Drive
Friction Welding Applications
Frequently competes with flash or upset welding when one of the work pieces to be joined has axial symmetry.
Used in automotive industry to manufacture gears, engine valves, and shock absorbers.
Used to join jet engine compressor parts.

30. Friction Welded Joints
Applications
Friction Welded Joints
Friction Welded Joint
Friction Welded Automotive Halfshaft
Courtesy AWS handbook

31. Friction Welded Joints
Applications
Friction Welded Joints
Camshaft Forging Friction
Welded To Timing Gear.
Cross Section of Aluminum Automotive Airbag
Inflator. Three Welds Are Made Simultaneously
Courtesy AWS handbook

32. Friction Welds Applications A Jet Engine Compressor Wheel
Fabricated by Friction Welding
Inertia Welded Hand Tools
Courtesy AWS handbook

33. Dissimilar Metals – Friction Welded
Aluminum to Steel Friction Weld

34. AWS Welding Handbook

35. Photomicrograph of Aluminum (top) to Steel (bottom)
AWS Welding Handbook

36. Friction Weld Tantalum to Stainless Steel Note: mechanical mixing
AWS Welding Handbook

37. Continuous Drive Friction Weld of Titanium Pipe
Ti-6Al-4V-0.5Pd
246 mm diameter
14mm wall thickness
No shielding used
This is an example of continuous drive friction welding of a titanium alloy for use in offshore applications. Although there was considerable “flashing” observed, both the weld center and the heat affected zone were free from defects, and very little (if any) change in hardness was noted across the weld.
Center HAZ
Froes, FH, et al, “Non-Aerospace Applications of Titanium” Feb 1998, TMS

38. Radial friction weld of Ti-6Al-4V-0.1Ru
The radial Friction Welding process offers the cost effective production of high quality welded titanium alloy risers offshore. The present study evaluates the metallurgical and mechanical properties of RFW welded titanium pips (9mm thick, 170mm outside diameter). The microstructural features of the weldments have been investigated by optical microscopy. The mechanical properties of the welded joints were characterized by micro hardness tests, conventional tensile and micro flat tensile tests. The microstructural investigations showed a fine transformed microstructure in the weld region (incl. HAZ). The tensile test results revealed higher weld region strength compared to the pipe material due to the observed fine transformed microstructures in this region. The weld ductility of the higher strength weld and HAZ regions remains high due to a process induced beta gain refinement by recrystallization.
Properties in Weld Better than Base Metal
Froes, FH, et al, “Non-Aerospace Applications of Titanium” Feb 1998, TMS

39. Linear Friction Weld Repair of Fan Blades
Turbine
Fan
Compressor
Combustor
This is a process for joining a base for an airfoil to a disk for an integrally bladed rotor stage in a gas turbine engine The process includes bringing the root surface into contact with a recessed surface in the rim and linear friction bonding the two.
Walker, H, et al, “Method for Linear Friction Welding and Products made by such Method” US Patent 6,106,233 Aug 22, 2000

40. Friction Welding for Mounting Ti Alloy Rotor Blades
Shielding Gas &
Induction Pre-heat
Weld Nub
Force
This invention is directed to a friction welding process for mounting blades of a rotor for a flow machine. A plurality of oblong welding surfaces “nubs” are provided at a circumferential surface of a carrier and are respectively welded to a surface of the blade. The welding temperature is obtained by external induction heating which is protected by shielding gas flow and the pressing application of oscillating friction relative motion between the blade and the carrier.
Linear Friction Weld
Schneefeld, D,et al. “Friction Welding Process for Mounting Blades of a Rotor for a Flow Machine”, US Patent 6,160,237 Dec 12, 2000

41. Friction Welding Connector to Imbedded Window Wires
Silver Based Ceramic Paint
Wire
Conductor
Glass
An automotive body glass comprising (a) a laminated glass with (b) conductive leads on or in the glass and having one or more conductive lead terminals, (c) an ultra thin pad of noble metal deposited onto a small zone of the glass in connection with a terminal, has a terminal clip connected to the noble zone using friction welding.
White, D et al, “Friction Welding Non-Metallics to Metallics”, US Patent 5,897,964 Apr. 27, 1999

42. Friction Stir Welding – Tool Design Modification
Hard Tool Tip Buried in Work Piece
Metal Flow
Force
A modification in the tool design is recommended in this patent where a tip with ridges is buried beneath the surface during friction stir welding at a slit angle to the perpendicular. This forces metal flow and good weld mixing and results in improved friction stir welding.
Travel Speed
Midling, O, et al, “Friction Stir Welding” US Patent 5,813,592 Sep. 29, 1998

43. Friction Stir Welding – Automation Moving Device
Elevation Platform and fixture device
Friction Stir Welder
This friction stir weld system has a base foundation unit connected to a hydraulically controlled elevation platform. The base unit may be connected to a movable support in order to provide mobility to the system.
Mobile Support System
Ding, R. et al, “Friction Stir Weld System for Welding and Weld Repair”, US Patent 6,173,880 Jan 16, 2001

44. Questions

45. Inertia Welding

46. Inertia Welding Process Description
Inertia Drive
Inertia Welding Process Description
One of the work pieces is connected to a flywheel; the other is clamped in a non-rotating axial drive
The flywheel is accelerated to the welding angular velocity.
The drive is disengaged and the work pieces are brought together.
Frictional heat is produced at the interface. An axial force is applied to complete welding.
Spindle
Workpieces
Non-rotating chuck
Hydraulic cylinder
Flywheel
Motor
Chuck
In inertia friction welding, one of the workpieces is connected to a flywheel, and the other is connected to a non-rotating axial drive system. The flywheel is accelerated to a predetermined rotational speed, storing the required rotational kinetic energy. The drive motor is disengaged and the workpieces are brought together. This causes the faying surfaces to rub together under pressure. The kinetic energy stored in the rotating flywheel is dissipated as heat through friction at the weld interface as the flywheel speed decreases. An increase in friction welding force (forging force) may be applied before rotation stops. The forge force is maintained for a predetermined time after rotation ceases to complete the weld.

47. Inertia Welding Where E = Energy, ft-lb (J)
I = Moment of Inertia, lb-ft2 ( kg-m2)
S = Speed, rpm
C = 5873 when the moment of inertia is in lb-ft2
C = when the moment of inertia is in kg-m2
Eu = Unit Energy, ft-lb/in2 (J/mm2)
A = Faying Surface Area

48. Inertia Welding Variables
Inertia Drive
Inertia Welding Variables
Moment of inertia of the flywheel.
Initial flywheel speed.
Axial pressure.
Forging pressure.

49. Linnert, Welding Metallurgy,
AWS, 1994

50. Inertia Welding Machine
Equipment
Inertia Welding Machine
Courtesy AWS handbook

51. Linnert, Welding Metallurgy,
AWS, 1994

52. Questions

53. Homework

54. A
Few
Specific
Examples

55. Super-speed (750 SFM) Inertia Welding of Jet Turbine Components
In this example, rather large diameter components are made from nickel base superalloy materials for various jet engine components. Typical forms of welding locally melt the parent material and are not useful for welding superalloys in view of the attendant change in microstructure thereof which significantly reduces their high temperature strength capability. In addition, the forging temperature range can be a low as 200F thus precise control of inertia welding variable must be maintained.
Problems
Melting Destroys Properties
Low (200F) Forging Temp Range – Need Precise Control
Ablett, AM et al, “Superspeed Inertia Welding”, US Patenmt 6,138,896, Oct. 31, 2000

56. Super-speed (750 SFM) Inertia Welding of Jet Turbine Components
Control Parameters
Workpiece Geometry (size)
Applied Weld Load Contact Stress)
Initial Contact Speed (surface velocity
Unit Energy Input (moment of inertia, radius of gyration)
Because of the large diameter parts, the surface speed is greater than most ordinary inertial welding applications and this further necessitates precise control of the weld parameters. The controllable parameters are listed above. Through experimentation, the working equations listed here have been defined as relationships between these parameters. As an example, a unit energy input E of 50,000 ft-lb/sq. in, and the contact area of 67.9 sq. in., a required rotary speed from the equation of 99.8 RPM is calculated which is within the operational limit of the specific welding machine with all the flywheels installed obtaining a maximum flywheel inertia of 2,000,000WK2. Correspondingly the initial contact speed requires 1880 SFM which is substantially greater than the SFM range according to conventional practice.
Where E = unit energy input
W = flywhel weight
K = radius of gyration
RPM = initial rotation
SFM = contact speed
D = diameter
A = contact area
Ablett, AM et al, “Superspeed Inertia Welding”, US Patenmt 6,138,896, Oct. 31, 2000

57. Titanium Engine Valve Inertia Weld Titanium Aluminides Titanium Alloyor
Titanium Borides
(Brittle at RT)
Titanium Alloy
(Ductile)
This example provides a titanium engine valve fabricated with discrete head and stem portions joined by inertia welding. The joint is located well up on the valve stem so that it iw not exposed below the valve guide. The head portion consists of a cast or forge heat trated titanium intermetallic compound. However the stem portion which is not directly exposed to the hostile environment of the combustion chamber, may be fabricated with mill anneal conventional titanium alloy rod stock. The valve is much less expensive to manufacture without sacrificing any mechanical or environmental characteristics in the portions of the valve subjected to high stress or those portions subjected to high temperatures.
Jette, P , Sommer, A., “Titanium Engine Valve”, US Patent 5,517,956 May 21, 1996

58. Hot Inert Shielding Gas
Inertia Welding of Magnesium and Aluminum Wheels for Motor Vehicles
Inertia Weld
Hot Inert Shielding Gas
Wheel
Spider
Aluminum Magnesium
Mg AM60 Mg AE42
Mg AM60 Mg AZ91
Mg AE42 Mg AZ91
This is a process for manufacturing a wheel for a motor vehicle, in which a wheel spider and a rim ring are connected with one another by means of inertia friction welding. At least one of the wheel parts consists of a magnesium alloy. The controlling of the speed of the start of the friction and compression process takes place as a function of physical characteristics of the magnesium alloy.
Welding parameters determined by the lower-deforming alloy or the alloy with higher melting point
Separautzki, R,et al, “Process for Manufacturing a Wheel for a Motor Vehicle” US Patent 6,152,351 Nov 28, 2000

59. Similarities between Continuous Drive and Inertia Drive
In both methods, welding heat is developed by frictional heat and plastic deformation.
Both methods use axial force for upsetting purpose.
In both methods the axial pressure may be changed (usually raised) at the end of rotation.

60. Differences between Continuous Drive
and Inertia Drive
Inertia drive
One of the workpieces is connected to the flywheel.
Rotational speed decreases continuously to zero during the process.
Kinetic energy of the flywheel dissipates through friction and plastic deformation producing heat.
Continuous drive
One of the workpieces directly connected to a rotating motor drive.
Rotational speed remains constant until the brake is applied.
Rotational energy of the workpiece dissipates through friction and plastic deformation, producing welding heat.