FAQ: Does heat treatment change the frequency of steel horns and boosters? I prepare my horn with untreated cold work tool steel (H2379) and when the frequency optimization is done, I send them to heat treatment. I'm about to send my pieces now and I can't change their dimensions easily after heat treatment. Mr. O.D.
The hardening process changes the frequency of tool steel sonotrodes.
Hardening by quenching and tempering decreases the frequency of steel horns, percentages within the 0.75-3.50 % range (150-700Hz @ 20kHz) are common for D2 and K110 steels. It is necessary to take this frequency shift into consideration to tune the horn before hardening. The decrease percentage depends on the horn material, geometry and aspect ratio; it is necessary to learn the real decrease percentage for each case by experimentation. Since it is not feasible to tune the horn after hardening, any mistake may place the horn final frequency out of tolerance range.
Heat treatment decreases the frequency of steel horns because it affects dimensions, density, microstructure and elastic properties. The frequency is determined by the dimensions, density and elastic properties (Youngs’ modulus, shear modulus and Poisson coefficient). Note: The elastic properties also change when the sonotrode temperature rises during operation, causing the frequency to decrease.
Learn more about tuning of ultrasonic horns.