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Ferrules
What are weld stud ferrules? Ferrules, also called arc shields, are single use rings that sit around the base of a weld stud during drawn arc welding. They do four things at once: contain the molten pool so it forms a proper fillet instead of spreading across the plate, concentrate the arc heat where it is needed, shield the weld from air so it does not go porous, and vent the gases the process generates. Without one, the drawn arc process does not produce a sound weld. AlbanyCountyFasteners.com stocks ceramic ferrules sized from 3/8 through 7/8 inch to match our weld stud range.
Why the ferrule is not optional
It is easy to look at a ferrule as packaging and it is nothing of the sort. Drawn arc welding creates a pool of molten steel at the joint, and without something containing it that pool spreads across the plate surface. Two things then go wrong: there is not enough metal left at the joint to form a proper fusion when the stud plunges, and there is no fillet around the stud base where the design assumes one. The ferrule also excludes air from the weld zone, which is what prevents porosity, and its vents let weld gases escape rather than becoming trapped in the metal. It is a consumable, but it is a functional part of the weld rather than an accessory to it.
Why ferrules matter to weld quality
- Contains the molten pool so a proper weld fillet forms around the stud base
- Concentrates arc heat at the joint instead of letting it dissipate
- Shields the weld zone from air, preventing porosity and contamination
- Vents weld gases so they do not become trapped in the metal
- Shields the operator from some of the arc flash, though proper PPE is still required
Using ferrules correctly
- One ferrule per stud, matched to the stud diameter
- The ferrule seats in a grip on the gun that holds it concentric with the stud
- An off centre ferrule produces an uneven fillet and a compromised weld
- After the weld cools, break the ferrule away to expose the fillet for inspection
- Order extra to allow for handling breakage, since the material is brittle
Sizes stocked
- 3/8, 1/2, 5/8, 3/4, and 7/8 inch, matching our full weld stud range
- Match the ferrule to the stud diameter, not to the plate or application
- Thru-deck applications require a different ferrule profile than flat plate welding
Order ferrules alongside your studs, whether headed concrete anchor studs or shear connector studs, since every drawn arc weld consumes one.
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Ferrule FAQs
Can ferrules be reused?
Standard ceramic ferrules are single use. The thermal shock of the weld, well over 1,300 degrees Celsius at the arc, cracks the material, and they are broken away afterwards to expose the fillet. Reusable designs exist in specialist materials but are not the norm.
How many should I order?
One per stud plus a margin for breakage. Ceramic is brittle and ferrules can crack in transit or handling, and the occasional weld needs redoing. Around ten percent extra is a common allowance.
What size ferrule fits my stud?
Match the ferrule to the stud diameter. A 3/4 inch stud takes a 3/4 inch ferrule. Using the wrong size means the ferrule does not seat concentrically, which produces an uneven fillet.
Do I need ferrules for capacitor discharge welding?
No. CD welding is a much faster, lower energy process that does not create the same molten pool, so no arc shield is needed. Ferrules are specific to drawn arc welding.
What are they made from?
A moldable technical ceramic, commonly cordierite, chosen for thermal shock resistance and low cost since the part is consumed on every weld. The vents moulded into the base let weld gases escape.
Do I need a different ferrule for thru-deck welding?
Yes. Welding through metal deck puts a standoff between the ferrule base and the beam flange, so a thru-deck profile is used rather than a standard flat ferrule. Contact us if your application requires them.