Reducing aluminum weld seams can be more challenging than welding steel panels, as resistance welders typically need twice the current to produce enough heat that bonds the studs together with the panel.
Arc welding can provide the solution. Proper execution can produce welds stronger than the stud itself.
Drawn Arc Stud Welding
The drawn arc stud welding process can be utilized with any diameter stud and material thickness combination, from thick materials that need stronger, more durable welds to very strong penetrative welds capable of withstanding compression, tension or bending forces. It is an especially appropriate choice when compressive stress testing requirements must be fulfilled for applications where strong, durable welds will be necessary.
Drawn arc welding requires flux-loaded studs with ceramic ferrules to help contain and form a weld base for welding molten weld metal during the weld process and to form an efficient weld pool. In addition, aluminum flux balls may also be placed at either end to easily start an arc and deoxidize weld pools during welding sessions – these type of studs can be found on heavy equipment, vehicle construction projects and in electrical or electronic component manufacturing environments.
At the core of drawn arc welding lies proper weld surface preparation and cleanliness. The weld area must be free of oils, greases and lubricants as well as rust, mill scale and other forms of oxide accumulation; additionally the weld end should have the appropriate weld base diameter and face angle. Furthermore, all components of the system such as guns must also be in working condition; damaged control cables should be addressed immediately since these often cause failure in stud welding applications.
CD Stud Welding
Capacitor discharge (CD) welding can be used to quickly weld small diameter studs to thin base materials, with each weld cycle typically lasting only milliseconds – making this technique suitable for projects with tight deadlines or where aesthetic considerations play a part, such as aesthetic appearance or when dissimilar metals need joining together.
A weld gun is placed against a workpiece and stored energy is released via its “timing” tip to melt the end of a stud and part of its base metal, forcing it into the melting material and producing welds in approximately 0.12 seconds. This method may work better for soft materials or when reverse side marking needs to be minimized; it does not perform as efficiently on hard, stiff materials which require higher fusion temperatures.
CD welding can be used with low carbon steels and alloys such as aluminium to produce strong, precise welds for various applications. It works particularly well when grounding down surfaces that may need to be ground down such as stainless steel materials used in food processing or pharmaceutical production. CD weld joints tend to be shallow so are less likely to damage or deform base materials than drawn arc welds, while their better appearance make CD welds the preferred choice over rivets or weld nuts.
Preparation for Welding
Aluminum stud welding requires specific equipment and skill, so taking time to assess your worksite and prepare materials can ensure high-quality results, reduce delays or rework, save time, and save money.
Before commencing with any welding process, all surfaces should be cleaned carefully to remove contaminants and coatings such as oils, chemicals, rust, mill scale and paint from them surfaces. Failing this can result in defects like poor fusion, porosity or lack of penetration that must be eliminated through wire brushes, abrasive media or solvents depending on what coating and surface needs cleaning.
Geometry should also be verified; precise fit between parts reduces filler metal use and helps create stronger welds. If there are large gaps between pieces, additional steps may be required such as grinding to tighten their fit or even chamfering or chamfering to close any large spaces between them.
Finally, it is essential that the welding electrode match the material being welded. A compatible electrode ensures maximum arc performance and weld quality.
Shielding gas is also essential, with 100% Argon (Ar) being optimal. An Ar/He mix (containing 25-75% He) may provide for more stable arc conditions and higher productivity due to greater ionization energy and thermal conductivity improvements, and faster re-ionization times for applications that demand quick fusion times.
Testing
Conducting tests on aluminum weld studs can uncover issues before they become an issue during production. Pre-production bend or torque tests can ensure that welding equipment is set up properly, the right materials are used and surface preparation is adequate; this helps avoid defects such as insufficient fusion or unstable arcs. Regular tests during production also ensure welding parameters remain stable, supporting high-quality welds with consistent quality standards.
Testing aluminum weld studs is similar to testing steel ones, with some minor distinctions. Because aluminum studs don’t produce as much heat when resistance welding using a standard resistance gun is applied. To offset this difference, capacitor discharge welders may be used to deliver bursts of energy directly onto the weld area to generate enough heat for fusing of the stud to the panel.
Tests conducted on stud welds may include visual, tensile and bend tests; with the latter typically administered to at least 10 test studs until failure occurs by repeatedly bending back and forth at opposing 30o angles with shear point exposed for shearing; once bent over a pin four times larger in diameter without breaking or losing contact points as evidence that welds have been performed correctly.