The end of homogenization treatment for 6XXX Aluminum billets
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The end of homogenization treatment for 6XXX Aluminum billets. Innovative Plasma Stirring (PTC) Process semi-continuous casting for Aluminum billets eliminates the necessity for homogenization before plastic deformation processes .

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The end of homogenization treatment for 6XXX Aluminum billets

Innovative Plasma Stirring (PTC) Process semi-continuous casting for Aluminum billets eliminates the necessity for homogenization before plastic deformation processes

The PTC stirring during solidification dissolves the inter dendritic phase into the grains and reduces the macro segregation in the cross section

PTC as cast

Normal casting after homogenization


Plasma stirring process for Aluminum 6XXX billets billets

  • The plasma stirring process is an add-on technology for existing casting line

  • The plasma stirs the liquid aluminum during the solidification, by applying rotating plasma arc

  • The rotating plasma arc induces very powerful magnetic and electric fields into the molten metal

  • This stirring effect eliminates the necessity for homogenization treatment, increases yield, improves mechanical properties and homogeneity and reduces DAS size


Plasma stirring billets

Creates changing current density flow in the molten metal

Induces electric and magnetic fields in the molten metal

Creates enormous shear forces by very effective stirring

Breaks the growing dendrites and creates a new nucleation center on each fracture

Creates smaller uniform dendrites and reduces significantly porosity and segregation levels


Plasma stirring process benefits for Aluminum 6XXX billets billets

  • The plasma stirring process benefits for aluminum 6XXX in comparison to homogenized (6-14 hours) normal DC billet:

  • Reducing macro segregation by distribution of the alloying elements in the billet during the solidification process

  • Reducing the micro segregation by defusing the alloying elements from the boundaries into the grains during the solidification process

  • Saving completely the homogenization treatment required for thermo mechanical process, such as extrusion, forging, rolling etc.

  • Improving significantly the surface quality of the billet and increases extrusion yield

  • Improving mechanical properties, such as elongation (e%)


Plasma eliminates the homogenization process billets

  • Normal casting

Plasma stirring as cast

  • Homogenization

  • Extrusion

  • T5 Aging

  • 5850C for 14 hours


Plasma eliminates the homogenization process billets

Extrusion of as cast billets

PTC as cast billets

End products for clients

PTC profiles without homogenization


Plasma as cast billet directly to extrusion billets

The plasma stirring was tested on more than 100 direct chilled casting (DC casting) billets on commercial lines of Aluminum 6XXX at several casting houses.

Plasma stirring casting

  • Normal casting

Casting aluminum 6XXX of 180mm diameter billets

DC casting of billets with plasma arc (at the same batch)

Casting temperature 700-710oC

Casting speed 100 -120mm/minute

No homogenization treatment was done

Extrusion was done without homogenization treatment.

Casting aluminum 6XXXof 180mm diameter billets

DC casting of billets without plasma arc (at the same batch)

Casting temperature 700-710oC

Casting speed 100-120mm/minute

10-14 hours homogenization treatment was done in 575-585oC

Extrusion was done after homogenization treatment.


Plasma stirring parameters billets

  • 40mm graphite electrodes were placed on top of the billets.

  • Several plasma stirring energies were applied – 9kWh/ton - 15kWh/ton

  • Argon flow was 6 litter/minute

  • Alumina ring was applied to allow argon surrounding around the electrode

Electrode and ring

Gripper and electrode


Extruded profiles
Extruded Profiles billets

  • Complicated types of profiles were chosen

  • Extrusion was done for homogenized normal cast billet and for not homogenized plasma as cast billet

Normal With Homogenization

PTCWithout Homogenization


Normal With Homogenization billets

PTCWithout Homogenization


Extruded Profiles billets

Complicated types of profiles were chosen

The PTC as cast billets without homogenization revealed the same extrusion behavior as normal casting with homogenization


Extrusion results
Extrusion results billets

The PTC as cast billets without homogenization revealed the same extrusion behavior as normal casting with homogenization.

The mechanical properties are in the same level. Elongation is increased

The anodize quality is in the same level

The billets were cast from secondary Aluminum thus contained very high

Levels of Copper (Cu) (0.06-0.12%) and Iron (Fe)(0.3-0.45%)

which significantly decrease the formability.


Center billets

Surface

Mid Radius

Samples for Optical Microscopy

1 rectangular samples were taken (2 cm thickness), from Mid radius

  • The samples were mounted in Bakelite

  • Polished by SiC papers and alumina suspension etched in Keller’s reagent.


Normal casting after homogenization billets

PTC 125A as cast

  • Reducing macro segregation by distributing the alloying elements in the billet during the solidification process

  • Reducing the micro segregation by defusing the alloying elements from the boundaries into the grains during the solidification process


Normal casting after homogenization billets

PTC 175A as cast

  • Reducing macro segregation by distributing the alloying elements in the billet during the solidification process

  • Reducing the micro segregation by defusing the alloying elements from the boundaries into the grains during the solidification process


Conclusions billets

The Plasma stirring:

Eliminates the necessity for homogenization treatment

The PTC as cast billets without homogenization revealed the same extrusion behavior as normal casting with homogenization

Reduces macro segregation by distribution of the alloying elements in the billet during the solidification process

Reduces the micro segregation by defusing the alloying elements from the boundaries into the grains during the solidification process

Increases yield by improving billets surface quality

The anodize quality is in the same level

Improves mechanical properties of the extruded product

Reduces and refines DAS


PTC movie billets


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