Luoyang Judian Metal Hot Processing Equipment Co., LTD is mainly engaged in the manufacture of complete sets of equipment in the metal thermal processing industry and the integration of the entire production line.
Frequency Selection in Induction Heat Treatment It has already been pointed out that many factors are involved in the selection of the quenching frequency. Higher frequencies (3-10 kHz; 400-500 kHz) are always used when a thin surface heating depth is required. In this case, the power supply must be accurately controlled (preferably automatically); accuracy and reproducibility are very important. In this chapter, four frequencies used for quenching steel bars are specifically compared.
These curves not only give the efficiency of the induction coil but also consider the overall frequency conversion efficiency. Within this range, several frequencies can be used for the same workpiece, except for workpieces with very small diameters. Lozinski (4, 40, 52) has done extensive work on the relationship between power input, quenching depth, frequency and heating time. This chapter is based on Lozinski's work. He mainly carried out this work for one-time heating.
Judian Medium Frequency Induction Furnace
The data in the figure have been simplified to the commonly used frequencies. The quenching temperature is between 850 and 900 °C. Hardening depths generally fall between 0.25 and 5 mm; since only a frequency of 450 kHz falls within this range, it is the most widely used frequency. Medium-frequency generators and thyristor medium-frequency power supplies are suitable for hardening workpieces with a hardening depth greater than 1.2 mm and can be used for high-power applications.
The curves in this chapter clearly show that for a given power density and heating time, thin surface layer depths require higher frequencies (where d is in millimeters). It can be seen that the effect of workpiece diameter varies significantly with frequency. Small workpieces can achieve the hardened layer depth with a given generator in a single heating application. Larger workpieces must be hardened using a moving scanning method with an automatically fed induction coil.
Quenching temperature
This chapter approximates the relationship between generator power, surface layer hardening depth, and time for the moving scanning method. Induction coil losses are included in the curves. The hardened layer depths given are the distance from the surface to the point where the hardness begins to decrease rapidly. Depending on the metal, this point is located between 50% and 80% of the actual heating depth. These curves are based on experimental data for 0.45% carbon steel.
The minimum speed and minimum diameter are given on the graphs. These results can be obtained using a single-turn induction coil and a power transformer. For a frequency of 10 Hz and a shaft diameter of 16-22 mm, the recommended minimum power density is 30 MW-m. Whenever possible, the steepest, most efficient portion of the curve should be used.
