Which stud shapes are available?

Depending on the customer, the component, the material and the process requirements, welding studs with different geometric forms and materials can be used in the various stud welding processes, which is crucial for achieving the right quality. The optimum working ranges differ, among other things, in the diameter of the welding element, the materials and component surfaces used, the sheet thickness and working position, the customer's quality criteria and the process requirements (automation, quality and reproducibility, workshop or site conditions), etc.

Depending on the external stud geometry, the stud welding processes or the weld pool protection, different types of studs have been developed with different significance.

Weld pool protection

As commercially available welding elements for stud welding, in principle 3 types of studs are offered as standard types according to DIN EN ISO 13918 [1], which differ in geometry with regard to the stud function.

Rule of thumb:

• The welding process determines the welding geometry.
• The ignition geometry of the stud influences the process through its shape.
• The component function determines the external geometry.

For the actual welding process, the geometric shape outside the welding plane and the stud length are of no significance. The design of the required welding geometry or stud tip depends on the welding process used. The longer the welding time, the greater the melting volume and the more tapered the stud tip. For example, the ignition cone of welding elements for tip ignition is flatter than that of welding elements for drawn arc ignition.

Drawn arc stud welding - Auxiliary ceramic ferrule

Drawn arc stud types with a ceramic ferrule feature a pressed-in aluminum ball at the tip to more easily ignite the arc and deoxidize the weld pool. The ceramic ferrule is a decisive factor in drawn arc studwelding with ceramic ferrule. In accordance with the standard, ceramic ferrules must always be supplied by the supplier as a unit to match the stud. Ceramic ferrules may only be used in dry conditions. Damp ceramic ferrules lead to pores and thus to a deterioration of the welding result.

A ceramic ferrule is used

• for standard stud types, pins or headed studs larger than 6 mm in diameter (welding diameter),
• when welding in forced positions (overhead position or vertical wall), and
• when welding under construction site conditions.

Disadvantage: Welding with ceramic ferrules is not suitable for automated series production due to the handling, feeding and associated technical effort.

Welding elements for stud welding with tip ignition (CD) - ignition tip

There are good reasons that the ignition tip in tip ignition is called the "ignition tip", since its shape determines the arc ignition process and thus the procedure. It must not be damaged or deformed and has a narrow qualitative tolerance in terms of length and diameter in DIN EN ISO 13918. The ignition tip is therefore not a "centering tip". For positioning the stud on the component, the stud position should only be marked using scribe marks. Deep marking, especially the use of manual center punches, shortens the welding time. The use of automatic center punches is recommended to obtain uniformly pronounced (shallow) marks.

The ignition tip on studs for tip ignition is responsible for the ignition process and the welding time; it is not a centering tip for positioning.

CE marking of studs

Unfortunately, you can always find data or certificates that give the impression that studs are CE certified. Welding studs, in particular threaded studs, are regulated in DIN EN ISO 13918 [1]. Since this standard is not a harmonized standard, welding studs according to DIN EN ISO 13918 [1] may not be marketed with a CE mark. As proof of compliance of the geometric, mechanical and chemical properties with the requirements of the standard, these studs must be supplied with acceptance test certificate 3.1 to DIN EN 10204.

An exception is the CE marking of (welded) construction products according to DIN EN 1090 "Execution of steel structures and aluminum structures", e.g., "headed studs on plate". This CE marking means in principle that the conformity verification procedures defined for this construction product with regard to conformity with the technical specification on which the CE marking is based have been successfully undergone and that the construction is thus such that it can meet the essential requirements when properly designed and executed.

Note: For welding tasks that are carried out in the regulated (e.g., building inspection) area, only studs that are listed in and comply with the applicable standardization – DIN EN ISO 13918 - should be used. When using non-standardized, manufacturer-specific welding elements, the end customer or the certification authorities should always be consulted.