How do I weld aluminium alloy 7075?
aluminiumsheet > 12-17-2019, 06:43 AM
Most aluminum alloys are weldable, but there are a fair number of them that are not, including 7075 aluminum. The reason 7075 is singled out in this example is that it is one of the highest strength aluminum alloys. When designers and welders look for an aluminum alloy to use, many will start by reviewing a table that lists all of the aluminum alloys and their strengths. But what those newcomers don't realize is that few of the higher strength aluminum alloys are weldable - especially those in the 7000 and 2000 series - and they should not be used.
The one exception to the rule of never using 7075 for welding is in the injection molding industry. This industry will repair dies by welding 7075 - but it should never be used for structural work.
Here are some simple guidelines to follow when choosing aluminum alloys:
Alloy Series
Main Alloying Elements
1000 series
Pure aluminum
2000 series
Aluminum and copper. (High strength aluminum used in the aerospace industry )
3000 series
Aluminum and manganese. (Low- to medium-strength alloys, examples of products using these alloys are beverage cans and refrigeration tubing)
4000 series
Aluminum and silicon. (Most alloys in this series are either welding or brazing filler materials)
5000 series
Aluminum and magnesium. (These alloys are used primarily for structural applications in sheet or plate metals - all 5000 series alloys are weldable )
6000 series
Aluminum, magnesium and silicon. (These alloys are heat treatable and commonly used for extrusions, sheet and plate - all are weldable, but can be crack sensitive. Never try to weld these alloys without using filler metal)
7000 series
Aluminum and zinc. (These are high strength aerospace alloys that may have other alloying elements added)
Lincoln suggests that if you have a need to design something of high strength aluminum, look to a 5000 series high magnesium alloy instead of a 2000 or 7000 series. The 5000 series alloys are weldable and will produce the best results.