Primary aluminum ingot is sold by purity, and the A7 and A8 grade names carry specific silicon and iron ceilings. How A7 relates to P1020A and Al99.70, which form to order, and what the specification should say.
An aluminum ingot is refined aluminum cast into a shape made to be remelted. It arrives at a cast house, a foundry or an extrusion plant, goes into a furnace and becomes either an alloy or a billet. What defines it commercially is not its shape but its purity: the aluminum minimum together with the ceilings on silicon and iron. This post explains the A7 and A8 grade names and how they map onto the other designations you will see on an offer.
Two different products travel under the words "aluminum ingot". Primary ingot is smelter metal, cast from the output of electrolysis cells, and is sold by purity. Alloy ingot, usually remelted, is sold by alloy code such as EN AB-46000, because what the buyer is paying for is a target alloy chemistry rather than purity. A7 as a name applies only to the first group.
| Property | A7 | A8 |
|---|---|---|
| Aluminum (min) | 99.7% | 99.8% |
| Silicon (max) | 0.10% | 0.08% |
| Iron (max) | 0.20% | 0.12% |
| Total impurities (max) | 0.30% | 0.20% |
| Typical use | Alloy production, deoxidation, billet | Conductor alloys, tight specifications |
A7 comes from the GOST 11069 designation system, where the digit indicates the purity step. P1020A is built on a different logic: the digits encode the impurity ceiling, 10 for silicon and 20 for iron. GB/T 1196 states the purity directly as Al99.70. All three describe the same commercial tier.
| Name | Source | Al (min) | Si (max) | Fe (max) |
|---|---|---|---|---|
| A7 | GOST 11069 | 99.7% | 0.10% | 0.20% |
| P1020A | International trade designation | 99.70% | 0.10% | 0.20% |
| Al99.70 | GB/T 1196 | 99.70% | 0.10% | 0.20% |
Silicon and iron are the natural main impurities of smelter aluminum, and they are the two that a foundry's alloy recipe has to start from. Silicon raises fluidity and is deliberately added in casting alloys, so any silicon arriving in the input metal has to be subtracted from the recipe. Iron is unwanted in almost every case: it forms hard intermetallic phases that reduce ductility and fatigue life, and heat treatment does not remove them.
| Form | Typical weight | Handling | Where it fits |
|---|---|---|---|
| Small ingot | 20–25 kg | Manual or forklift | Foundry, blended charges, small batches |
| T-bar | 500–750 kg | Crane | Large melting furnace, continuous feed |
| Sow | 600–1,000 kg | Crane | High-tonnage melting, cast house |
