Drawn-Arc or Tip Ignition?

For thin sheets, i.e., sheets with a thickness of about 1 to 4 mm, capacitor-discharge stud welding with tip ignition is primarily used. When using tip ignition, the heat input is very small, because the welding process lasts only one to three milliseconds, and the melting zone is at the most 0.5 mm deep. That is why there is usually no thermal or geometric marking on the reverse side of the workpiece. A shielding gas is not required.

For aluminum welding, the gap method is recommended, which is characterized by particularly shorter welding times and higher plunging speeds than the contact method. Stud diameters from M3 to M6 (dia. 3 to 6) are very suitable, whereas M8 is considered insecure.

For drawn-arc stud welding, the short-cycle process with shielding gas is primarily recommended. This has similar benefits (short welding times, small thermal load of the component, very good automation capacity) as stud welding with tip ignition and, furthermore, has a very high level of process reliability.

Short-cycle drawn-arc stud welding must be carried out with sufficient gas protection so as to prevent a poor weld or decreased load-bearing capacity of the welded joint due to macropores. Ideal shielding gases are inert gases like Argon or a mixture of Argon and Helium.

Also important in drawn-arc stud welding of aluminum is the correct polarity of the welding elements in combination to the sheet metal. In case of smaller sheet thicknesses of up to 2 mm, negatively polarized studs may have advantages; in case of larger sheet thicknesses or stud diameters positively polarized studs have proven successful.