Chemistry
Spectrometer analysis of samples taken during casting, reported per cast (drop) against the agreed aim and limit ranges. Hydrogen content of the melt may also be recorded.
Cast house feedstock
Aluminium Rolling Slabs & Sheet Ingots
A rolling slab, also called a sheet ingot or rolling ingot, is a large rectangular block of aluminium cast by the direct-chill (DC) process and used as feedstock for hot rolling mills. It is not finished sheet or plate: it still has to be scalped, homogenised and rolled. Metline sources rolling slabs in the alloy, size and quality class your mill specifies and ships them worldwide with full cast documentation.
- Process
- Vertical DC casting
- Typical thickness
- about 400 – 750 mm
- Alloys
- 1xxx to 7xxx wrought
- Next step
- Scalp, homogenise, hot roll
What is an aluminium rolling slab?
Every coil of aluminium sheet, foil and can stock, and almost every plate, starts life as a rolling slab. Molten metal of the correct chemistry is cast vertically through a water-cooled mould, solidified by direct water spray as it descends, and cut to length. The result is a rectangular ingot that can weigh well over ten tonnes and is shaped to fit the entry of a hot reversing mill.
Because the slab is the first solid form of the metal, its quality limits everything that follows. Inclusions, hydrogen porosity, cracks or segregation that enter the slab will show up later as surface streaks on anodised sheet, pinholes in foil, laminations in plate or failed ultrasonic tests on aerospace stock. For that reason slabs are bought against a rolling mill's own purchase specification, not against a sheet or plate standard.
The terms are used interchangeably in the trade: European cast houses tend to say "rolling ingot" or "rolling slab", North American mills "sheet ingot". Extrusion billet (round logs for presses) and remelt ingot (small pigs for foundries) are different products made in the same cast houses; see the related section for both.
From molten metal to rolling slab
- Melting and alloyingPrimary metal, alloying elements and sorted scrap are melted in a furnace and adjusted to the target analysis, usually inside the tighter "aim" range of the mill specification rather than the full standard range.
- Melt treatmentThe metal is degassed (often by an in-line rotary unit) to remove hydrogen, fluxed, and passed through ceramic foam or deep-bed filters to remove oxide and other inclusions. A grain refiner such as Al-Ti-B rod is added in the launder.
- Direct-chill castingMetal flows into an open-ended, water-cooled mould on a descending starting block. Water sprayed directly on the emerging shell completes solidification. Electromagnetic or low-head moulds are used where a smoother surface and thinner shell zone are needed.
- Butt and head sawingThe irregular start (butt) and end (head) of the cast are sawn off, and the ingot is cut to the ordered length.
- ScalpingThe rolling faces are milled to remove the as-cast surface layer and the segregated shell zone beneath it, commonly several millimetres to over 10 mm per side depending on alloy and casting method.
- Homogenising and preheatingThe slab is soaked at a high temperature, typically in the range of about 450 – 610 °C depending on alloy, to even out micro-segregation and dissolve or condition intermetallic phases, then brought to hot-rolling temperature.
Scalping and homogenising may be done by the cast house or by the rolling mill. The purchase order should say which, because it changes the delivered weight, the surface condition and the acceptance tests.
Alloys cast as rolling slabs and what they become
| Alloy family | Typical alloys | Rolled into | Casting notes |
|---|---|---|---|
| 1xxx commercial purity | 1050, 1060, 1070, 1100, 1235, 8011 | Foil, fin stock, lithographic sheet, electrical strip | Low iron and silicon control; very clean metal for foil gauges |
| 3xxx Al-Mn | 3003, 3004, 3104, 3105 | Can body stock, roofing, cookware, brazing core | Large primary intermetallics need careful homogenising |
| 5xxx Al-Mg | 5052, 5083, 5182, 5754 | Marine plate, can ends, automotive sheet, tank plate | High Mg increases oxidation and cracking risk; beryllium traces or protective atmosphere often used |
| 6xxx Al-Mg-Si | 6061, 6082, 6016 | General engineering plate, automotive body sheet | Mg/Si ratio held tight for consistent ageing response |
| 2xxx and 7xxx | 2024, 7075, 7050, 7475 | Aerospace and tooling plate | Crack-sensitive; slow, controlled casting, stress-relief treatment and strict ultrasonic acceptance |
| Clad and multi-alloy | 4xxx clad on 3xxx core | Brazing sheet | Liners may be roll-bonded or co-cast |
Chemistry is fixed at casting and cannot be corrected later, so the composition limits on the slab order are normally a narrowed version of the Aluminum Association or EN 573-3 range. A mill making can stock, for example, will hold magnesium and manganese far tighter than the standard 3104 limits allow, because small shifts change earing and strength in the finished sheet.
Typical rolling slab dimensions and weight
There is no catalogue size for a rolling slab. The cross-section is designed around a particular mill: its maximum entry thickness, roll barrel width and the coil weight it is set up to produce. The ranges below show what is common across the industry and are not a stock list.
Typical industry envelope
- Thickness (as cast)
- about 400 – 750 mm; 500 – 600 mm is very common
- Width
- about 1,000 – 2,500 mm, matched to the finished sheet width plus edge trim
- Length
- about 3 – 9 m, set by the furnace and mill entry
- Weight
- from a few tonnes to over 30 tonnes per slab
- Shape
- Rectangular with rounded corners; rolling faces may be slightly convex or concave by mould design
- Condition
- As-cast, sawn to length, scalped, or scalped and homogenised
Weight is calculated from the actual section, not a perfect rectangle, because cast corners are radiused and mould faces are profiled to compensate for contraction. As a rough guide, a 600 × 1,800 × 6,000 mm envelope is 6.48 m³, or about 17.5 tonnes at 2.70 t/m³; the real slab will weigh slightly less. Scalping 10 mm from each rolling face of that slab removes roughly 0.6 tonne of metal, which returns to the cast house as scrap.
| Envelope (mm) | Volume (m³) | Theoretical mass at 2.70 t/m³ (t) |
|---|---|---|
| 450 × 1,250 × 4,000 | 2.25 | 6.1 |
| 500 × 1,500 × 5,000 | 3.75 | 10.1 |
| 600 × 1,800 × 6,000 | 6.48 | 17.5 |
| 600 × 2,000 × 7,000 | 8.40 | 22.7 |
| 700 × 2,300 × 8,000 | 12.88 | 34.8 |
How rolling slabs are inspected and accepted
A slab has no tensile test, because its mechanical properties tell you nothing about the finished rolled product. Acceptance rests on four areas, each of which should be written into the purchase specification.
Internal soundness
Ultrasonic scanning or sectioned slices to check for cracks, porosity, oxide films and inclusions. Aerospace and can-stock mills set the strictest limits.
Geometry
Thickness, width, length, squareness of sawn ends, straightness and face profile, measured at agreed points.
Surface
Freedom from cold shuts, bleed-outs, laps, deep folds and surface cracks that scalping will not remove.
Grain structure
Macro-etched slices to confirm uniform, fine equiaxed grains and no feathery or columnar zones.
Traceability
Each slab marked with cast number, slab position in the drop and alloy, carried through to the coil records.
Certification is normally an inspection document to EN 10204 3.1 listing the cast analysis and the results of agreed internal-quality checks. Ask for the document before shipment, not after unloading.
Points to agree before ordering
- Whose specification governs: the rolling mill's purchase specification should be the reference document, with any standard (EN 573-3, Aluminum Association limits) cited inside it
- Delivered condition: as-cast, sawn, scalped, or scalped and homogenised; state scalping depth per face and per edge if the supplier does it
- Chemistry aim: give aim values and tolerances, not just the standard range; include limits for trace elements that matter to the end product (for example sodium in 5xxx, or iron and silicon in foil stock)
- Internal quality class: the ultrasonic method and acceptance level, and the sampling frequency
- Weight basis: invoiced on actual weighed mass, with crop and scalping losses tracked separately from net rolled yield
- Handling: lifting points, dunnage, securing for sea freight and protection of scalped faces from damage and corrosion
How to order rolling slabs from Metline
- SpecifyAlloy and chemistry aim, slab section and length, delivered condition, quantity in slabs and tonnes, internal-quality class and the rolling mill specification that applies.
- QuoteWe confirm alloy, temper, tolerances, certification, packing and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessSlabs are sourced to your specification, sawn and scalped where ordered, inspected for geometry and surface, and marked for traceability.
- DocumentEach shipment carries an EN 10204 3.1 inspection document with cast chemistry and agreed internal-quality results, plus packing list and weight notes.
- ShipSecured on dunnage with lifting provision, shipped as break-bulk or in suitable containers on FOB, CIF or DAP terms.
References and standards
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets)
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- EN 10204 – Metallic products: types of inspection documents
- ASM Handbook, Volume 15 – Casting (direct-chill casting of aluminium ingots)
- Hydro – Sheet ingot (cast house products)
Aluminium rolling slabs: frequently asked questions
What is the difference between a rolling slab and a sheet ingot?
None in practice. Both terms describe the same DC-cast rectangular ingot used as hot-rolling feedstock. "Sheet ingot" is more common in North America, "rolling slab" or "rolling ingot" in Europe and Asia.
Why does a rolling slab need scalping?
The outer layer of a DC-cast ingot contains oxide, surface folds and a segregated shell zone. If it were rolled in, these would become surface defects on the sheet. Milling the rolling faces removes this layer before homogenising and rolling.
Can I order a rolling slab by tensile strength?
No. Strength is created by rolling, heat treatment and ageing at the mill. A slab is ordered and accepted on chemistry, internal soundness, geometry and surface condition.
How heavy is an aluminium rolling slab?
It depends on the mill. Slabs commonly weigh between about 5 and 30 tonnes. Calculate from the actual cross-section and length at 2.70 t/m³, remembering that rounded corners and profiled faces make the real slab lighter than a perfect rectangle.
What is homogenising and who does it?
Homogenising is a long, high-temperature soak that evens out the chemical segregation formed during solidification and conditions intermetallic particles so the metal rolls and finishes well. It can be done by the cast house or the rolling mill; the order should state which.
Do you supply aluminum rolling slabs for export?
Yes. Metline sources rolling slabs to the purchaser's specification and ships them worldwide with cast documentation, packed and secured for break-bulk or container transport.
Need rolling slabs for your mill?
Send your purchase specification, alloy, section, length and tonnage. We will reply with sourcing options, inspection documents and a delivered price.
