Penetration depth of eddy current
Eddy current penetration depth is the depth below the surface at which the current density has dropped to a fraction of its surface value. It depends on frequency and conductivity.
Physicochemical mechanism of action
An eddy current generates a magnetic field direction in a metal that is linked to the current direction. The eddy current penetration depth depends on the frequency and conductivity of the material. At high frequency or low conductivity, the current density drops faster.
Metallurgical relevance & risks in welding
Too shallow penetration depth can cause the eddy current not to penetrate deep enough into the material structure, affecting the hardness and strength of the weld. Too deep penetration increases the risk of hot cracking and distortion.
Shop practice & instructions
To achieve optimal penetration depth, choose the correct frequency and current strength based on the metal. For highly conductive materials like aluminum, a low frequency (e.g., 10 kHz) is suitable, while for low-conductivity steels, a higher frequency (e.g., 50 kHz) is required. The penetration depth should be in the range of 2 to 4 mm.