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Aluminum Alloy Fastener Characteristics

Mar. 14, 2019

The tensile strength of pure aluminum is about 13,000 psi, and it is possible to increase the strength by a small amount of alloying elements. The aluminum alloys of 2XXX, 6XXX, and 7XXX have a good effect on heat treatment. Therefore, virtually all threaded fasteners used for load transfer are made of these three types of aluminum alloys. There are four aluminum alloys that are almost exclusively used.

The 2024-T4 aluminum alloy (containing 4.5% copper, 1.6% manganese, 1.5% magnesium, and the balance aluminum) is a heavy-duty alloy. It achieves a perfect balance of strength, corrosion resistance, manufacturability, and economy, and is widely used in the manufacture of threaded fasteners.

High Quality Bolts

High Quality Bolts, Round Self Drilling Screws, and studs made of 7075-T73 aluminum alloy (1.6% copper, 2.5% manganese, 0.3% chromium, and the rest aluminum) have a slight improvement in strength, and due to " T73" special heat treatment process, which can prevent stress corrosion to a large extent. But the high cost makes its popularity limited.


6061-T6 aluminum alloy (containing 0.6% silicon, 0.25% copper, 1% magnesium, 0.2% chromium, and the rest aluminum) can be used to design internal and external thread fasteners with higher requirements for corrosion resistance.

Round Self Drilling Screws

The 6062-T9 aluminum alloy (containing 0.6% silicon, 0.25% copper, 1% magnesium, 0.09% chromium, 0.5% lead, and the balance aluminum) is almost exclusively designed for the nut. This alloy is stronger than the 6061-T6 aluminum alloy and has relatively good corrosion resistance.


The full thickness Plain Finish Hex Nuts made of 6062-T9 aluminum alloy has sufficient strength to match the bolts made of 2024-T4 or 7075-T73 aluminum alloy. Machine screws, nuts and other 1/4" and smaller nuts are made of 2024-T4 aluminum alloy.


The four aluminum alloys already mentioned are the most widely used in the manufacture of thread-loaded fasteners, while other aluminum alloys are used in the manufacture of other types of fasteners. Small solids, half tubes, and blind rivets are made of 1100-F, 5052-F, 5056-F aluminum alloys, respectively. The heat-treatable 2017-T4, 2117-T4, 2024-T4, 6061-T6 aluminum alloy, and the relatively newly developed 7075-T73 aluminum alloy have superior shear strength and do not require “pre-drive treatment”. Can be driven.


Flat washers are usually made of aluminized 2024-T4 alloy; coil spring washers are usually made of 7075-T6 alloy; tapping screws are made of 7075-T6 alloy, and self-tapping screws are obtained by anodizing of the same material alloy. The 2011-T3 aluminum alloy (containing 5.5% copper, 0.5% lead, 0.5% niobium, and the balance aluminum) can be used to make parts for thread cutting machines.


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