Aluminum Frcition Welding

Contents

• Concept of friction welding.• Types of friction welding

(Inertia, stir )• Metallurgy of friction welding.• Advantages & disadvantages.• Applications.

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Concept of friction

• What is Friction Welding?• Friction welding is a solid-state process (non-fusion) that is

achieved through frictional heat.• This heat is generated by controlled contact of two

components until material reaches its plastic state, at which time plasticized material begins to form layers that intertwine with one another.

• The friction welding machine controls this contact through a series of unique parameters for rotational speed (rpm’s), axial force and time.

• Once these parameters are established, they are recorded, stored and then repeated with each cycle of the machine

Types of friction welding

Friction welding

Inertia Stir

Types of friction welding

Inertia friction welding:

In Inertia Welding, one of theworkpieces is connected to aflywheel and the other isrestrained from rotating. Theflywheel is accelerated to apredetermined rotational speed,storing the required energy. The drive motor is disengaged andworkpieces are forced together by the friction welding force.

Types of friction welding

Stir Friction Welding:The frictional heating causes a softened zone of material to form around the probe. This softened material cannot escape as it is constrained by the tool shoulder.

As the tool is traversed along the joint line, material is swept around the tool probe between the retreating side of the tool (where the local motion due to rotation opposes the forward motion) and the surrounding undeformed material.

Advantages & Disadvantages

Advantages of Friction Welding:• Strong welds for all geometries.• Narrowest heat affected zones .• Short weld times save you time and money.• There is no melting ,hence no solidification defects occur, gas

porosity , and segregation .• Easy to manage with only two quality control parameters - RPM and

Pressure.• Used for some alloys which are not fusion weldable like , AL 7075.• Limitless panel length and width.• Join dissimilar alloys.

Advantages & Disadvantages

Disadvantages:• Worm holes• Oxide film due to Zn affecting surface

tension of weld pool reduced diffusion.• Cannot easily be used for making fillet

welds.

Metallurgy

• Deformation mechanisms:(Boundary diffusion- recrystallization ) • Strengthening mechanisms:-Fine graining

Metallurgy

Mechanical Properties:

1-Strength• Higher after process due to :

-fine graining.

+-increase of welding speed.

Metallurgy

2-Hardening:• higher due to Precipitation hardening

By aging.

Applications

Space shuttle technology:• Using frictional stir welding in external tanks

because of :

-high strength.

-low defects.• Replacing AL 2219 with

AL-LI 2195 reducing 3400kg .