REMELT AND CASTING OPERATIONS

Bought-in scrap and scrap from Hulamin’s manufacturing processes are melted together with primary aluminium and alloying elements such as magnesium, manganese, zinc, silicon and copper in Hulamin’s remelt operation.

The molten metal is then treated, filtered and skimmed before being cast into rolling slab and extrusion billet, the feedstock for the rolling and extruding processes.

ADDING VALUE

By adding small amounts of other elements to pure aluminium, strong alloys are produced which can be further conditioned in the heating, rolling, extruding and finishing processes to create products with the appropriate properties that our customers require.

Since aluminium is an infinitely recyclable product, all scrap produced in Hulamin’s manufacturing processes, as well as scrap recovered from our local fabrication customers and post-consumer scrap, is remelted and reused.

THE ROLLING PROCESS

The rolling process must produce plate, coil or sheet with not only accurate dimensions, but such other attributes as flatness, edge quality and correct thickness profile, specified physical properties and freedom from surface defects.

In the hot rolling process, slab is heated and then processed through the reversing hot roughing mill (where the thickness of the rolling slab is reduced by up to 95% and the length increased by up to 24 times) before being transferred to the hot finishing mill to ensure that it is rolled to a tight tolerance intermediate thickness.

In the cold rolling process, hot rolled coils are further rolled, at ambient temperature, to achieve the required tight gauge tolerances and mechanical properties required. Foil rolling is a specific cold rolling process designed for very thin products and certain alloys. Hulamin’s stand-alone foil mills can reduce cold rolled products to gauges as low as six microns.

ADDING VALUE

Hot rolling increases density, strength and ductility and cold rolling is used to further harden and strengthen the product, balancing between strength and ductility as required. Further finishing processes deliver the appropriate properties and qualities required for each specific product application, and include:

Annealing

A re-heating process performed to regulate the mechanical properties or permit further reductions in thickness during cold rolling.

Coating

The application of paint and lacquer to clean and pre-treated aluminium coil, followed by oven curing, is required for certain applications such as beverage can-ends.

Processing

Further processing is often required to obtain the appropriate widths, lengths or coil sizes, flatness and metal surface cleanliness required by customers. This is achieved through further processing through precision slitters, cut-to-length lines, shears, tension levellers, embossing rolls and degreasing lines.

THE EXTRUSION PROCESS

Extrusion billet is heated and passed through an extrusion press, a powerful hydraulic device in which a ram pushes the softened metal through a unique die to produce the desired profile.

The completed extrusion is cut off the die, cooled, mechanically treated and aged to give it the required mechanical strength properties, and may be further coated, anodised and/or fabricated to provide the final specification required by the customer.

ADDING VALUE

The extrusion process supports unlimited possibilities for design. With the appropriate alloy and controlled thermal treatment, extrusions offer a wide range of application opportunities.