INSTITUTE OF TECHNOLOGY OF METALS

DEVEOPMENT OF THE INSTITUTE :: High-Frequency Pulse Hardening of Surfaces

        The proposed technology is designed for surface hardening of steel and cast-iron machine articles for enhancing their operational lifetime. The process includes rapid heating of the article surface by powerful high-frequency pulses and subsequent rapid self-induced hardening of the heated layer by heat release inward the metal. Formation of disperse hardening structures (martensite, carbide, etc.) increases hardness and wear resistance of the article. Equipment for changing typical HF generators with a power up to 200 kW to a continuous-pulsed operating mode and sets of special inductors were developed; technological processes of hardening of articles made of different types of steel and cast iron were elaborated.

        The steel-layer hardness reaches 65 HRC, and the hardening depth varies from 1.5 mm (generator frequency is 440 kHz) to 3 mm (generator frequency is 66 kHz).

        The efficiency of the process is up to 15 cm2 of the article surface hardened per second (with a generator power   of 60 kW).

        Hardening of shaft surfaces, rollers, wheels, bodies of revolution, inner surfaces of sleeves, diesel cylinders, hardening of guides, frames, arbitrary surfaces, tools, stamps, cutting edges, articles of a curvilinear shape, etc.

        - Advantages

        − absence or very low warpage; lower shortness due to a plastic core and grain dispersion; possibility of local hardening of outer and inner surfaces of various articles; lower heating-energy expenses; engineering simplicity, easy automation.

        High-Frequency Pulse Quenching

        The process includes rapid heating of the hardened surface by a pulse high-frequency field with a subsequent quick self-quenching of the heated layer by heat transfer to cold deep material layers. This leads to formation of a martensite structure and grain dispersion, which increases the lifetime of treated parts.
Basic technical characteristics:
        - Maximum hardness of the reinforced layer, НRС units – 65; Maximum depth of hardening, mm - 3.5; Maximum density of radiation flux, kW/cm2 - 102;
        - Maximum heating rate, K/s - 106; Production rate of the unit, cm2/min - up to 100.
        Range of products quenched: Shafts, bushings, friction couples, guides, internal surfaces, cranks, cutters, pinion gears, including long-length articles.

        Microphotographs of the St45 article surface before and after hardening