Characteristics of aluminum alloy fasteners

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

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

　　 Bolts, screws and stud bolts made of 7075-T73 aluminum alloy (containing 1.6% copper, 2.5% manganese, 0.3% chromium, and the rest is aluminum) have made slight improvements in strength. And because of the special heat treatment process of T73, it can prevent the occurrence of stress corrosion to a large extent. However, its high cost has limited its popularity.

　　 6061-T6 aluminum alloy (contains 0.6% silicon, 0.25% copper, 1% magnesium, 0.2% chromium, and the rest is aluminum) can be used to design internal and external threads with higher requirements for corrosion resistance fastener. (Guide: The real reason for the damage of threaded fasteners)

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

　　 The full-thickness nut made of 6062-T9 aluminum alloy has enough strength to match the bolts made of 2024-T4 or 7075-T73 aluminum alloy. Machine screws, nuts and other 1/4 inch and smaller nuts are made of 2024-T4 aluminum alloy.

　　 The four aluminum alloys mentioned are the most widely used in the manufacture of threaded load-bearing fasteners, while other aluminum alloys are used in the manufacturing of other types of fasteners. The small solid, half pipe and blind rivets are made of 1100-F, 5052-F, and 5056-F aluminum alloys. 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 can drive without pre-transmission treatment. .

　　 Flat washers are usually made of aluminum-plated 2024-T4 alloy; spiral spring washers are usually made of 7075-T6 alloy; tapping screws can be made of 7075-T6 alloy; self-tapping screws are made of the same material alloy through the anode Handle it. The 2011-T3 aluminum alloy (containing 5.5% copper, 0.5% lead, 0.5% bismuth, and the rest is aluminum) can be used to make parts for thread cutting machines.

　　Strength characteristics

　　 The strength characteristics of external thread fasteners aluminum alloy materials 2024-T4, 6061-T6 and 7075-T73 are specifically discussed in ASTM F468 on page B-158; nut aluminum alloy materials 2024-T4, 6061-T6 and 6062 -T9's strength characteristics are specifically discussed in ASTM F467 on page B-184.

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