Without ceramic ferrules, arch stretching is ineffective, and welds are not very strong. To understand why it is essential to know how drawn arc stud welding works.
Drawn Arc Welding
First, set the traction bracket machine to a suitable stud diameter. Then place the studs on the plate to prepare the weld.
When the operation is activated, the mounting bolt is lifted slightly from the plate, and the pilot bracket is actuated.
This is followed by the main arc that melts the tip of the ring into the molten metal. It creates a metal basin on the board.
The machine then places the backing back on the board and fuses it with the molten metal to create the solid weld expected from stud welding.
The role of ferrules
Ferrules are necessary to contain the molten metal pool. Without the ceramic ferrule for stud welding, the molten metal spreads out, leading to a messy finish.
The primary purpose of the ceramic ferrule is to protect the studs from the air during the welding process and prevent porosity and contaminants from affecting the weld. It can also perform the role of a shield to reduce exposure to surroundings from UV rays.
The ceramic ferrule is shaped like a ring around the throat, with a fused channel between the throat and the plate. They form a weld and include molten metal in their shape to create a discreet, seamless and elegant joint.
When the process is complete, you need to remove the ferrule. Since it is ceramic, operators can easily scrape the ferrules and leave the weld finished.
The use of ceramic ferrules for welding studs
For studs with a diameter of more than 10 mm, ceramic ferrules are the most common protection. Its primary role is as follows:
- The arc can be focused on the work surface to stabilize the arch, reduce heat loss, reduce the cooling rate, and prevent the angle from spacing and exploding.
- Since the ceramic stud welding ferrule bears high temperatures, the metal vapour formed in the combustion chamber of the ceramic ferrule may escape from the cutting exhaust. This prevents the atmosphere from remaining on the surface of the work piece, reducing the atmosphere and the metal's role in the molten pool.
Welded ceramic ferrules are made of inexpensive materials and consist primarily of magnesium aluminate and aluminium oxide. The stability of temperature changes is essential. However, ceramic ferrules for stud welding can only be used for one-time welding. Ceramic ferrules should be heated and dried if wet. The ceramic ferrule and stud welding should be concentric. Ceramic ferrule mouths that are tilted and have asymmetrical contact cannot be used. If it is not used, it will affect the movement of the stud down on the welding torch, which will affect the quality of welding.
When are ceramic ferrules not required?
Ceramic ferrules are an essential part of the arc welding process, but there are some welding processes in which they are not used.
Short-cycle welds do not require stud welding ferrule and instead use an inert shielded gas. Shield gas prevents pollutants in the air from affecting the molten metal. This can change its properties and weaken the weld.