Understanding the aluminium numbering system

It is our job to ensure that our clients have access to a great supply of metal products. They need these items for all sorts of uses. Regardless of their needs, we make sure they receive the most appropriate goods. This could be aluminium bar and plate in grade 5251 or another alloy or material.

There are many aluminium combinations

Aluminium is a material that can alloy with a huge array of other elements. This is to enhance its chemical or mechanical attributes. So, there are many combinations of alloying elements to choose from and a lot of unique alloys.

So that we can make sense of this, an aluminium numbering system exists. The Aluminium Association is responsible for creating it. They are also the ones who preserve the system. You will find that there are all sorts of rules for labelling all the alloys. Firstly, you must know whether your aluminium alloy is cast or wrought.


These alloys make use of a 4 digit system. The first number designates the main alloying element. For instance, 1XXX alloys specify a mainly pure alloy while a 5XXX alloy shows that substantial amounts of magnesium are in the alloy. Contact us if you need aluminium bar and plate in grade 5251.

As for the second digit here, it tells us that there has been a specific alteration to an alloying substance. Such controls get registered with IADS and demand the right documentation.

The third and fourth digits label the alloy. These numbers are inconsistent apart from in the 1XXX series. Here, they reveal the minimum aluminium content is between 99% and 100%.

Cast aluminium

This also employs a 4 digit system, with the main difference being a decimal point (XXX.X). Not unlike wrought, the initial digit of this system shows the major alloying elements or element.

The second and third digits of this system are arbitrary too. They indicate the alloy. The only exception is 1XX.X. Like the wrought alloy system, these numbers specify aluminium purity over 99%.

As for the last digit after the point, it marks whether your aluminium alloy is an ingot or casting. A “1” indicates the first while a “0” indicates the latter.

Temper designations

With temper designations, they are able to follow the digits for both cast and wrought aluminium alloys. They show what processing has been done to the metal to enhance its mechanical attributes.

For instance, if there is an “F”, it indicates that it has been fabricated. To put it in other terms, there has been no special processing to augment its mechanical features.

The “O” designates an annealed aluminium alloy and “H” means strained handled. As for the “W”, it shows thermal heat treating and “T” tells you the aluminium has had thermal treatment.

It is vital that you remember these designations when using aluminium in procedures that generate enough heat to change the strain hardening or heat treatment.

The best aluminium bar and plate in grade 5251 and more

At Brindley Metals, we aim to give our customers the best experience every time. To do so, we supply high calibre materials and lots of useful services. In addition, we offer competitive pricing, and can provide knowledge and advice on every product.

So, if you would like to shop with us for aluminium bar and plate in grade 5251 or other alloys, feel free to get in touch. We can cater for many needs, including bulk orders.

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