High frequency quenching hardened layer shallow (1.5 ~ 2 mm), high hardness and difficult to oxidation, deformation small, quenching are of good quality, high efficiency, suitable for work under the condition of friction parts, such as general smaller gear, shaft (materials for 45 # steel, 40 cr); Intermediate frequency quenching hardened layer deep (3 ~ 5 mm), applicable to twist, under pressure load of parts, such as crankshaft, wheel, grinding spindle (materials for 45 # steel, 40 cr, 9 mn2v and ductile of high frequency quenching, surface hardening for a short period of time! Crystal tissue is very thin!
The stress ratio of the small medium frequency surface of the structure is smaller than that of the high frequency, which is called the working frequency, and the heating depth of 5-10, 000-10, 000 hz is called the middle frequency 10000HZ, and the high frequency “high frequency quenching” and “intermediate frequency quenching” are the same in principle. Using high frequency (or medium frequency, frequency) induction current, the surface of steel is rapidly heated and then cooled immediately. Its principle is: when in a conductor through certain frequency of alternating current coil, the coil inside and outside will produce a magnetic field with the same frequency communication, if the workpiece is placed within the coil, the artifact will induction alternating current, and make the workpiece heating. The distribution of inductive current in the workpiece is not uniform, and the current density is the largest on the surface, which becomes the “surface effect”.
Induced current penetration depth on the surface of the workpiece depends on current frequency (week/SEC), the higher the frequency, the current penetration depth more shallow, the hardening layer thin, so, can choose different frequencies to achieve different depth of hardening layer. According to the current frequency, induction heating can be divided into: high frequency induction heating (20,000 ~1000000 weeks/second), medium frequency induction heating (5000 ~10000 weeks/second) and the working frequency induction heating (50 weeks/second).