SU802379A1 - Inductor for heating cylindrical articles - Google Patents

Description

(54) INDUCTOR FOR HEATING CYLINDRICAL

PRODUCTS

It is adjacent directly to the primary winding and, thus, provides a direct electromagnetic connection between the primary winding and parts of the secondary winding.

This is a disadvantage of the known inductor. The presence of direct electromagnetic coupling between the primary and all parts of the secondary winding makes it difficult to create a smooth and stable transition zone.

For example, when changing the loop current in the primary winding, respectively, the currents in the parts of the secondary winding change unambiguously, hence the size of the transition zone depends on the instability of the heating intensity, i.e., the instability of the loop current.

The aim of the invention is to improve the quality of heat treatment by obtaining a stable transition zone between the heated and unheated parts of the product, regardless of the fluctuations of the loop current in the primary winding.

To achieve this goal, in a well-known inductor for heating cylindrical products containing a multi-turn primary winding and a secondary winding consisting of coaxially installed main and auxiliary parts, in which the main part in cross section has the shape of a trapezium facing the large base of the primary winding, the larger base of the trapezium made completely overlapping the primary winding, and an additional part of the secondary winding is made multi-turn, the turns of which are installed on both sides of the main part of the secondary windings.

Another difference is that the turns of the additional part of the secondary winding are installed with a gap relative to the main part, are mated with it along a conical surface and have a triangle shape in cross section.

Another difference of the inductor is that the inner surface of the turns of the additional part of the secondary winding is made conical.

In addition, the turns of the Additional part can be connected to the main part of the secondary winding and connected to it in opposite directions.

FIG. 1 shows a constructive diagram of an inductor, in which the turns of an additional part of the secondary winding are connected to the main part of the secondary winding and are connected to it in opposite directions. Here: 1 - multiple primary winding; 2 - the main part of the secondary winding; 3 - additional multi-turn parts of the secondary winding; 4 - heated product; And - the heated part of the product; B - transition zones between the heated and unheated parts; in fig. 2 - inductor, type

from the side with a schematic distribution of currents in the windings of the inductor and in the product: Ij is the current in the primary winding; 1d - current induced in a large base in the main part of the secondary; B - current in small

the basis in the main part of the secondary winding; C is the current branching into the secondary portion of the secondary; Is is the current induced in the product from the main part of the secondary winding; Is is the current induced in the product from the additional part of the secondary winding; c. is a branching point of current b to currents 1e and c; g is the summation point of currents b and in fig. 3 is a structural diagram of the inductor, in which the turns of the additional part 5 of the secondary winding are installed with a gap relative to

the main part of the secondary winding, mates with it along a conical surface and have a triangular shape in cross section; in fig. 4 - additional part b of the secondary winding, which has an internal surface

0 is made conical C - the angle of inclination of the inner surface of an additional part of the secondary winding to the product); in fig. 5 schematically shows the distribution of currents in the windings of the inductor shown in FIG. 3; Jy is the current induced in the additional part of the secondary winding in a place directly close to the small base of the trapezium of the main part of the secondary winding; IB is the current in the product induced from the current I; B is the current induced in the additional part of the secondary winding in the place immediately adjacent to the large base of the trapezium of the main part of the secondary winding; Bo is the current in the product, induced from the current Ig. The inductor (Fig. 1) has a primary multiwheel winding 1. The secondary winding consists of the main part 2 and the additional parts 3.

The main part 2 is a hollow coil with a slot and has a trapezoid shape in cross section. The large base of the trapezoid is facing the primary winding and completely overlaps it. Such an inductor design excludes electromagnetic coupling between the primary multi-turn winding 1 and the additional parts 3 of the secondary winding. Additional parts 3 of the secondary winding are made of several turns and mounted coaxially with the main part 2. The turns of the additional parts 3 are electrically connected to the main part in opposite directions. Connection (Fig. 2)

o produced on both sides of the slot coil of the main part.

The cavities of the primary and parts of the BTUIC winding are filled with flowing water: to cool the windings. Primary and “torich” on the windings are isolated from each other.

In the inductor (Fig. 3), an additional part of the secondary winding 5 is its

fight two turns with a slot. The additional part 5 of the secondary winding is installed with a gap relative to the main part 2, mates with it along a conical surface and has the shape of a triangle in cross section. Here, as in the previous case, the electromagnetic coupling between the primary winding 1 and the additional parts 5 of the secondary winding is eliminated. Thus, in additional portions of the secondary winding, current is only induced from the main portion of the secondary winding. And this leads to the fact that in the product the current induced from the additional part of the secondary winding has the opposite direction compared to the current induced in the product from the main part of the secondary winding.

The flux linkage between the additional part of the secondary winding and the product can be gradually reduced in a direction from the heated part of the product to the unheated part if the inner surface of the turns of the additional part 6 of the secondary winding is tapered (Fig. 4).

The inductor operates as follows, when turning on the primary winding 1 in the high-frequency circuit, a current 1 | flows through it. In the large base of the main part of the secondary winding facing the primary winding, at the time instant in question, a reverse current b is compared with the current b. The current lines b, reaching the slot of the main part of the secondary winding, are divided at the point a by the current Is, the lines of which are closed along the small base of the main part of the secondary winding, and the current whose lines are closed by the turns of the additional part 3 of the secondary winding. The current lines Is and m are again connected at the point b.

In the product in zone A (Fig. 1), a current Is is induced from the current Is of the main part of the secondary winding (Fig. 2), which causes the product to heat up.

During the continuous heating of the volume of the metal in zone A (Fig. 1), due to the change in the properties of steel, the products of the current line ly re-concentrate and more gravitate towards the cold metal in zone B, causing its active heating. However, in zones B of the product from currents 1c. In additional parts of the secondary winding, a current 1 is induced, the lines of which are directed opposite to the line current Is. Thus, the resulting induced current in the product zones B is significantly reduced or equal to 0.

The more the area A of the product warms up, the more the current lines Is tends to move to the colder zone B, but the more it is compensated for by the current U induced from turns 3.

This is due to the fact that when zone A is heated up, current 12 at point a due to the proximity effect is divided into current b and 1+ in different proportions than in the case where zone

But it remained still cold, i.e., current 14 increased quantitatively by decreasing the current b. The effect of the counter-connected turns 3 on limiting the heating zone A and stabilizing the transition zone can be regulated by various methods: the resistance of turns 3, their diameter and number, the choice of connection points.

If the connection points of the coils 3 are located in the immediate vicinity of the slot of the main part of the secondary obmotokch, then there is the largest selection of myigms for the coils 3, which does not always satisfy the requirements of heating. When the connection points are removed from the slot, the power take-off in them decreases.

 The inductor (Fig. 3), in which the turns of the additional part are installed with a gap relative to the main part, mate with it along a conical surface and have a triangle shape in cross section, works as follows: when the primary winding 1 is connected to the circuit (Fig. 3) Kei also flows a current of 1.

FIG. 5 dots show the direction of this current at the considered moment of time.

S In the larger base of the main part of the secondary winding 2 (Fig. 3), a current It (Fig. 5) is induced, which has a reverse direction compared to the current B (indicated by crosses). The current lines Ij, due to j continuity, reach the slot of the main part of the secondary winding, close-on, along the small base of the trapezium, which adjoins the product, having received (in the plane of the drawing) the opposite direction. At the same time, the current density Ii in the small base of the trapezium, healed to the heated product, will be greater than in the larger base of the trapezoid facing the primary winding 1, due to the unequal cross section of these bases. In the product in zone A (Fig. 3), a current Iy is induced from the current la (Fig. 5),

 causing heating of the product. The direction of the current U is the opposite direction of the current Ij.

In the additional part 5 of the secondary winding, in a place directly close to the current 1a of the main part of the secondary winding, a current I is induced in the direction opposite to the current Ij. The current 1y, in turn, causes in the zone B (FIG. 5) of the product a current Ij inverse to the direction of the current Ij in zone A of the product.

Thus, when in the process of continuous heating of the volume A of the product covered by the small base of the main part of the secondary winding 2, the properties of the steel of the product change and the electromagnetic field is redistributed, it tends to close for

the cold part B of the product (outside zone A), then the induced current U in zone A of the product folds with the current Ij in the product in the direction reversed by an additional part of the secondary winding 5. The resulting current in zone B becomes smaller, which is significantly reduces active heating zone B than if it were in the absence of an additional part of the secondary winding 5.

Thus, in the zone B (transition zone) of the product, currents of two directions are induced: from the main part of the secondary winding 2 a current Is is induced due to the redistribution of the electromagnetic field during the deep heating of the area A of the product, and from the additional part of the secondary winding 5 a current Ig is induced. The currents b and ig by magnitude ultimately depend on the primary current 1 | and repeat all possible variations. In the absence of an additional part of the secondary winding 5, there would be no current IB, in which case the stability of the transition zone B would largely depend on the stability of the current 1 | in the primary winding. If there is an additional part of the secondary winding 5, the stability of the transition zone B is significantly increased, since current fluctuations 1 | in the primary winding, similar oscillations of the 1-I currents 1 and Ij in the product are caused, and the resultant currents in the zone B remain constant.

In an additional part of the secondary winding 5, in a place immediately adjacent to the large base of the trapezium, a current Is is also induced that is inverse to the current Ij in the large base of the trapezium. This current due to continuity, reached the slot, closes, due to the proximity effect, through the base of the additional part of the secondary winding 5, which is directly adjacent to the product. A current of 1 | o arises in the product, which can cause undesired heating of this part of the product. To eliminate this effect, the internal surface of the additional turns of the secondary winding 6 (Fig. 4) is conical, i.e., with a variable gap (angle oi) with the product in the direction of increasing the gap as it moves away from the heated part of the product. The proposed inductor was tested under laboratory conditions.

The rod was inserted into an inductor (frequency 8000 Hz) and heated for 4 s to a temperature of 1200 ° C, after which it was soaked in water. Measurement of the hardness of the areas adjacent to the heating zone A showed that the tempering zone (transition zone) was in all cases 25-28 mm. With similar heating modes in the same inductor, but without additional parts of the secondary winding, the tempering zone was 75-90 mm, i.e. exceeded the allowable requirements for products and did not differ in stability.

Creating a stable transition zone between the heated and unheated parts of the product allows the proposed inductor to be used in automatic lines, for example, the track finger production line.

Claims (4)

1. An inductor for heating cylindrical articles containing a multi-turn primary winding and a secondary winding consisting of coaxially installed main and auxiliary parts, the main part in section having a trapezoid shape facing a large base towards the primary winding, characterized in that improving the quality of heat treatment by obtaining a stable transition zone between the heated and unheated parts, the larger base of the trapezium completely covers the primary winding, and an additional part It is not multiturn, the turns of which are installed on both sides of the main part 2. The inductor according to claim 1, characterized in that 0 that the turns of the additional part of the secondary The windings are installed with a gap relative to the main part, are conjugated to it along a conical surface and have the shape of a triangle in cross section. 3.Inductor on PP. 1 and 2, characterized in that the inner surface of the turns of the additional part of the secondary body is made conical. 4. The inductor according to claim 1, characterized in that the turns of the additional part are connected to the main part of the secondary winding and are connected to it oppositely. Sources of information taken into account in the examination 1.Slukhotsky A.E. and Ryskin S.E. Inductors for induction heating. “Energie. Leningrad branch, 1974, fig. 10-14. 2. USSR author's certificate No. 484259, cl. C 21 D 1/12; H 05 B 5/18, 1973. : h $ 1 / 2.2 /////// tLLllv., 1 6 eight FIG. five