How to choose aluminium slug for battery shell extrusion

Auminium cold extrusion process is a good approach to produce aluminium parts with short lead time, material saving, high dimension precision. A lot of aluminium parts are choosing cold extrusion as production method to improve quality and increase production efficiency. Aluminium battery shell is one of cartridge cans produced by cold extrusion. Since the aluminum battery container is a thin-wall, high depth, there are difficulties in production control to reduce wall thickness fluctuation, we have to choose good quality of aluminium slugs with high purity and even metal distribution as raw material to get qualified extrusion parts. This article introduces how to choose 

aluminium slugs for below aluminum battery design.

Example design of aluminium battery shell

How to choose aluminum slug

The gauge of aluminium slugs.Since the aluminium battery shell is a shape of rectangle cartridge, the round aluminium slugs shall lead to lack of material on the four corners and serious eccentric material flow cause extrusion failure. We have to choose rectangle aluminum slugs as raw blank and calculate the gauges according to principle of volume-invariance.

Total volume of battery shell: V=56262mm³, the width and length of aluminium slug should be similar to finished aluminium shells choosing: S=55mmx55mm, so the aluminium slug thickness H=V/S=18.5mm. Then the gauge of aluminium slugs are fixed as 55mmx55mmx20mm

Aluminium slug pretreatment

1) Annealing, the aluminium slugs should be annealed in furnace and decrease its hardness and increase the aluminium ductility. Annealing process shall make the slugs easier to be extruded. Annealing process include heating temperature 420℃ and holding on 3 hours, cold the slugs by nature air.

2) Surface treatment, the burs and surface light scratches are removed by tumbling treatment, which improves surface metal mechanical parameters too. The aluminium slugs should be tumbled with lubricant powder(Zinc stearate powder), and keep the surface roughness value Ra<0.8μm³. Then the aluminum slugs are ready to be charged for extrudsion.