TechnologyPoints of Interest
When Using
Aluminum Drawn
Arc Weld Studs
Prelude:The information provided has some basic guidelines needed to employ drawn arc aluminum
stud welding. The use of aluminum weld studs has grown in popularity over the past 8 years
because of their light weight and electrical grounding with integrated nut (Earth Stud). The
goal is to touch on important questions about using aluminum drawn ac weld studs.

What

are a few special concerns withwelding aluminum material?

Aluminum forms an oxidic skin when exposed to the environment.
Aluminum oxide can also form during welding and is not advantageous.
Also, there is concern about hydrogen dissolubility. When in the molten
state, aluminum can react with hydrogen and create gas pockets inthe solidified weld, making a porous material. The material must be
free from moisture and lubricants. During welding the arc and moltenmaterial must be shielded by an inert gas, generally Argon.

What

are the basic aluminum materials
to attach a drawn arc stud onto?

Assuming a suitable surface is available, aluminum studs canbe welded properly to components made of aluminum sheet stock,extrusions, and castings. Successful weld results in sheet stock 3xxx
series (Al-Mn), 5xxx series (Al-Mg) (considered excellent weldability) &6xxx series (Al-Mg-Si), castings 3xxx and 5xxx series, and extruded 6xxx
series. Still, each application should be evaluated for weldability using
proper welding equipment.

Are

there dimensional and application
limitations?

Whatis meant by backing theweld area?

Backing is defined as a solid non-ferrous material (Copper)
block approximately the diameter of the gas shield touching thematerial and centered directly behind the weld zone. Usually,
the backing block is spring mounted providing 178N to 222N
of force (40 to 50 pounds).

What

are the key aluminum
panel surfaces conditions?

The material surface has a direct impact on the welding
result. It is best to clean the components and subject them to apickling passivation procedure to obtain a dry and contaminant
free surface with a thin and even oxidic skin. Drawn arc
welding uses AC welding machines which tolerate a small
amount of dry lubricant. There are limits for maximum
quantity and type of dry-film lubricants suitable for aluminum
stud welding. Also, any additional lubrication with oil will
have an adverse impact on the welding quality. These dry-film
lubricants and oil must be studied, verified, and held constantif suitability testing shows it is feasible.

The minimum possible wall thickness of aluminum components tobe stud welded is 1.0 mm without cracks appearing on the component
back side. Recommendations are indicated in Table 1 that may differ
depending on the joining variables. Therefore, the greater the weld
f lange diameter (see Graphic 1) of a stud, the larger the material
thickness of a component must be to successfully weld aluminum studs.

Graphic 1.
Weld Flange Diameter
location on studs.

Weld Flange

Table 1. Weld Flange Diameter vs. Weld Condition
Weld Flange Dia. (mm)Weld without
Backing
Weld withBacking

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Min. Panel Thickness, Cleaned & Passivated (mm)Min. Panel Thickness with Some Dry Lube (mm)Min. Panel Thickness, Cleaned & Passivated (mm)Min. Panel Thickness with Some Dry Lube (mm)Fastener World no.204/2024 惠達雜誌

4.2
1
1.2
1
1.1

7.5
1.1
1.211.18
1.2
1.3
1.1
1.2

9
1.4
1.6
1.2
1.4

10
1.7
2
1.5
1.7

112
2.5
1.7
2

TechnologyCan

moisture on the aluminum sheet
panels be a concern?

Yes, condensation on panels will affect welding quality. Example,
cold panels just delivered during the cold winter months should have time
to warm up.

What

are some of the key process
limitations and conditions?

Resistance Spot Welding cannot be in the same station as drawn arc.
Studs cannot be placed over joints with adhesive. Avoid inconsistent orexcessive stamping draw lubricants. The best orientation is downward (seeGraphic 2). The limit is 45 degrees. Gravity may impact distribution of
fillet under certain conditions, larger studs and thick materials requiring
longer weld times (see Graphic 3).

Graphic 2.
The best orientation to weld
studs shows gas cover andsecondary shield boot.

Graphic 3.
Hot aluminum fillet can drip
during welding process due togravity, shown at 90 degrees.

Isthere particular material handling ofAluminum drawn arc weld studs?

Incoming aluminum weld studs are packaged in plastic bags. The studs
have a one-year shelf life because old studs have aged thus changing their
physical properties and require a modified weld schedule to be used. If studbags are opened, the shelf life is compromised.

Are

there specific stud and nut
surface finishes?

Common surface finishes for studs are BONDERITE
M-NT 2040 (a.k.a. Henkel Alodine 2040), or equivalent,
which provides a consistent known oxide layer and ashelf life of about 1 year. The nuts have a dry lubricant
Microgleit DF921, or equivalent, to provide a constant low
friction for torque performance and reduce the potential
for mating thread galling.

Are

there reprocessing solutions
for improper welds?

If the stud breaks off or welding is not possible and thewall thickness is < 1.5 mm, then a break-stem rivet withthreaded mandrel could be used. These rivets are made ofsteel and require special sealing and corrosions avoidance.
If the wall thickness is >1.5 mm, replacement aluminumstuds can be welded after the damaged stud has been
removed and the joining zone has been cleaned. Further
reprocessing solutions such as MIG weldable aluminum
plates with replacement aluminum drawn arc weld studs
already attached can be used. If the walls have larger
holes, then weld a stud to a similar piece of coupon andattach the coupon to the part.

What

are the key functionsof a drawn arc weld
Ground Stud Assembly (Earth Stud)?
For quality control, the nut has a removal torquerequirement (a.k.a. break-away torque) before paint.
The stud and nut flange design serves 4 functions. See
Graphic 4.
1.

The clamp load is generated against the flange
providing a strong joint without putting the weldzone in tension.

2.

The nut is seated flush to flange preventing theintrusion of paint onto the grounding surface.

Aluminum studs must not be stored outside. Ideal storage is dry, lowheated rooms with low air humidity. Cold studs should be allowed to warm
up to avoid condensation from air humidity. At least once every 6 months, allstuds retained in the feeding drum or hopper should be removed and disposedof before refilling.

3.

The octagon shape provides the opportunity, in aproduction environment, to quickly test the weldusing existing tools without changing the breakaway nut torque.

What4.

The octagon can be used for anti-rotation withappropriately sized winged terminals that arecurrently available.

Whatis the proper storage of aluminumstuds?

are some of the stud and nut
materials and preparations?

Many studs are made of AlMg5 (EN AW-5019, designated EN AWAl Mg5) and the nuts are AlMg2,5 (EN AW-5052, designated EN AW-Al
Mg2,5) or equivalent. Next, they undergo a surface treatment characterized
by a series of pickling and cleaning, with a final passivation coating/finish
process. The studs are then placed into sealed bags for transportation andstorage. These bags should not be opened until the time of use.

Graphic 4.
Ground Stud Assembly(Earth Stud)Copyright owned by Fastener World / Article by Ralph White惠達雜誌 Fastener World no.204/2024

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