The dual frequency induction heating process is applied to obtain a more uniform temperature field model of bevel gear. There are many factors affecting the quality of dual frequency induction heating of bevel gear, including structural parameters and electrical parameters. This section mainly analyzes the influence of electrical parameters on the dual frequency induction heating process of bevel gear, such as medium and high frequency current density ratio, frequency ratio, etc.
Based on the characteristics of electromagnetic induction heating and considering the skin effect, the thermal conduction heating method is adopted to analyze the influence of the electrical parameters of dual frequency current on the induction heating process. Uneven temperature is an important factor causing uneven surface hardening layer of bevel gear. The requirements for hardening layer of bevel gear tooth root and tooth surface are different in production. When ensuring the austenitizing depth of 2.5mm, analyze the temperature uniformity from the angle of bevel gear tooth width direction and tooth profile direction, and take the temperature difference as an important index to evaluate the quality of induction heating.
The magnitude of the induced current is directly related to the current density. The greater the current density, the greater the induced current on the gear surface, and the induced current is also directly proportional to the current frequency. Therefore, in the process of dual frequency induction heating, in order to evenly heat the tooth profile, the selection of high and medium frequency current density is inversely proportional to the current frequency. In this section, it is assumed that the current frequency, current density and frequency of intermediate frequency of high frequency remain unchanged, the intermediate frequency current density is changed, and the numerical analysis of dual frequency induction heating of bevel gear is carried out with the ratio of medium and high frequency current density (intermediate frequency current density / high frequency current density) as the variable.
The electrical parameters of dual frequency induction heating are as follows: the high frequency current density is 6.0 × 107a / m2, high frequency current frequency is 100kHz, medium frequency current frequency is 6KHz, and medium frequency current density is 1.2 respectively × 108A/m2、1.35 × 108A/m2、1.5 × 108a / m2, the corresponding medium and high frequency current density ratio is 2.0, 2.25 and 2.5 respectively, the medium and high frequency output time ratio is 2:1, the switching times is 30, and the total induction heating time is 45s.
Cut a section in the middle of the bevel gear tooth width and select two paths as shown in the figure, namely, path L1-L2 and path L3-L4 at the depth of 2.5mm. Later, these two paths will be used to analyze the uniformity of temperature field in the tooth profile direction after dual frequency induction heating of bevel gear.