SU722957A1 - Method of inductional heating of articles - Google Patents

Description

(54) METHOD OF INDUCTION HEATING OF PRODUCTS

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The invention relates to electrothermal and can be used for induction heating of products with a low coefficient of heat (1C) of hydration.

The known method of induction heating products, including heating currents of industrial frequency 1 and 12.

The disadvantage of the method is that it is suitable only for ferromagnetic products of small diameters (up to 120 mm) and unsuitable for products From non-magnetic materials of large diameters (400 mm and more).

The aim of the invention is to improve the quality of heating of large-diameter products from non-magnetic materials and to reduce metal losses.

For this, the product is pre-heated by currents with a frequency of 10-25 Hz, heating the surface of the product to a temperature of 100-200 ° C and lower than the temperature of accelerated metal oxidation, then producing a gradual decrease in the power induced in the product, in proportion to the controlled surface temperature rising to 20-30 % of the initial inductive power for 40-70 minutes by heating the central part of the product to a predetermined final temperature, and the surface - by 100–200 ° C, higher than the temperature accelerated by oxidation thallium.

An example of the proposed method. A large diameter billet, for example 500-1000 mm, of a non-magnetic material, for example titanium, is placed in an induction heater, with increased (up to 15-25% of the induced power in the billet) specific heat losses to the environment, due to increased thermal conductivity of insulation between billet and inductor. In the first heating stage, the inductor is connected to a power source with a frequency of about 10-25 Hz and is heated to obtain a temperature on the workpiece surface 100-200 ° C below the temperature of accelerated metal oxidation (i.e., to about 500 ° C for titanium) .

Claims (2)

Then proceed to the second stage of heating. Gradually, by turning the power regulator of the inductor, the power induced in the workpiece is reduced by 20–30% of the initial value for 40–70 min, depending on the parameters of the workpiece (diameter, thermal conductivity, etc.). Due to the increase in {1 heat loss from the surface of the billet into the environment by 13-1.7 times compared to conventional heat losses, which are 10-15% of the power induced in the billet, the thermal efficiency during heating will be reduced to 75-85%, Therefore., The power required to compensate for heat loss in the second stage of heating will be 1525% of the original inductor power. Due to the overheated layer that forms with in the workpiece in the first stage of heating, on. The second stage, due to the specified power control, heats the central part of the workpiece to a predetermined horse temperature, for example 900 ° C, and heats the surface of the workpiece to a temperature 100–200 ° C above the accelerated metal oxidation temperature, i.e. 700-800 ° C for 1 hour. At the same time, the overheated layer at a depth of about 200 mm from the surface will be heated to 930950 ° C. Next, the transition to the thermoelectric stage of heating. The inductor is switched to industrial one often at 50 Hz for 10 minutes; In this case, the preyad layers of the preform are pre-alloyed (Foif temperatures of 90 ° C or 30–50 ° C higher, i.e., up to 920–950 ° C. 7. 4 The proposed method makes it possible to sharply reduce metal oxidation and improve the quality of heating. The method of induction heating of products, including heating by the current of the sawn frequency, characterized in that, in order to improve the quality of heating of products of larger diameter from non-magnetic materials and reduce metal losses, the product is subjected to preliminary heating by currents with a frequency of 1025 Hz, heating the surface and built up to a temperature of 100–200 ° C below the temperature of accelerated metal oxidation, then gradually reducing the induced power into the product, in proportion to the increase in the controlled surface temperature to 20–30% of the initial value of the induced power for 40–70 min, heated the central part the product to a given final temperature, and the surface by 100–200 ° C higher than the temperature of accelerated metal oxidation. Sources of information taken into account in the examination 1. Authors certificate of the USSR N 62658, cl. C 21 D 1/10, 1943. 2. USSR author's certificate number 322374, cl. From 21 D 1/42, 1970.