Productive Aluminum Machining - Part1

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Global Industry Project Manager - Aerospace, Power Generation and Medical

Aluminum is one of the most popular metal alloys used in manufacturing. The strength-to-weight ratio and the characteristics of the alloys, from both the manufacturing as well as the intended-use aspects, are very desirable for many industries. However, if the demands of machining aluminum are not well understood, the perceived ease of machining aluminum can lead to some misconceptions and create problems for manufacturers who need to be able to compete profitably.

Aluminum alloys are produced by adding alloying elements to pure aluminum to enhance the properties and characteristics depending on the requirements needed in the final component(s). The types and percentages of alloying elements added to the pure aluminum affects the properties of the material produced. It is important to note that each series can also have different temper (hardness condition), can be wrought, cast, or billet, and the finished parts have their own unique requirements. These variables can alter the machining strategy, the demands on the cutting tools and the machine tool. Understanding the basic differences for each type of alloy is a good place to start.

The most common industry-standard specification is the AA (Aluminum Association) and is specific for aluminum. It is a basis for aluminum standards and designations worldwide and uses a four-digit system to differentiate the various alloys based on the alloying elements for each series.

The system is as follows:

• First digit: indicates the principal alloying elements.
• Second and third digits: specific alloy designation (number has no significance but is unique). .
• Fourth digit: Casting (0) or ingot (1, 2) designation. .

• 1xxx series alloys are almost 99% pure commercial aluminum typically used in the chemical and food industries.
• 2XXX are primarily alloyed using copper and some magnesium. The most popular aluminum alloy in the aerospace industry, by volume, is 2024. Also used for automotive wheels, aircraft structure parts, and engine parts (Cylinders & Pistons). It can be heat-treated to improve strength and toughness. Although copper improves the workability of the alloy, it diminishes corrosion resistance in comparison to other aluminum alloys.
• 3XXX is alloyed primarily with silicon, copper and magnesium when cast, or manganese when wrought. It is used extensively for automotive applications such as cylinder blocks, and cylinder heads, wheels, compressors and fittings.
• 4XXX series is alloyed with silicon and is often used on applications like cast pump housings.
• 5XXX series uses magnesium as the primary alloying element, though smaller percentages of magnesium are also used in many other aluminum alloys. These alloys have moderate to high strength, good corrosion resistance in marine environments (aluminum 5083), and good weldability.
• 6XXX series uses magnesium and silicon as the primary alloying elements. These alloys can be solution heat-treated to improve strength. They are extensively used in marine frames, aircraft and truck frames, fasteners, heat exchangers and heat sinks, with 6061 being the most widely used alloy in this series. You will notice that 6xxx series aluminum is typically used in extruded or wrought form.
• 7XXX series uses zinc as the primary alloying element, along with small amounts of magnesium, as well. Produces a heat-treatable, high-strength alloy. The added zinc decreases the machinability of these alloys. Aluminum 7050 and 7075 are widely used in aircraft manufacturing to produce fittings, gears & shafts, regulating valves, and other items where the high strength is beneficial. *See notes regarding additional alloying agent lithium / Al-Li Alloys.
• 8XXX is much less common overall with typical uses being for bearing applications such as bi-metal slides for internal combustion engines, and others uses.

There are many differences within the alloy groups depending on the material condition and the process used to form it. The following table shows which are the main alloying elements for each cast aluminum series, the main characteristics that highlight each series and some example applications:

The following table shows the main alloying elements for each of the wrought aluminum series, the main characteristics that highlight each series, and some example applications:

Within the cutting tool industry, the ISO Material Designation for aluminum alloys is the letter “N” in a green background which will look similar to this:

By following the recommendations for this ISO material group and understanding which alloy you are machining and the properties of the alloy, you can optimize your ability to profitably compete by selecting the appropriate tooling, cutting conditions and application techniques for each. For support on your application needs, YG-1 is an industry leader in aluminum tooling solutions globally.

Please visit "Contact Us" on the YG-1 HQ website for more information and to find local technical support.

*Aluminum Lithium Alloys (Al-Li Alloys)
These alloys were developed specifically for use in applications where high strength and light weight are important such as motorsport and aerospace. They are lower density alloy variants which allow significant weight reduction, high stiffness, superior damage tolerance, and excellent corrosion resistance over the more traditionally used alloys. The corrosion resistance of Alloy 2099 is much better than 7075-T6511 and 2024-T3511. Fatigue crack growth resistance also shows improvement vs 2024-T3511, which has been a standard product for applications considered fatigue critical. These alloys do machine quite differently than some of the alloys they replace and can present real challenges to tool life comparatively.