JPH0361337A - Ring transformer for electrical heating of strip - Google Patents

Abstract

PURPOSE:To allow the heating as uniform as possible in the transverse direction in accordance with strips of various sizes and various material qualities by specifying the inside size of a transformer corresponding to the thickness direction of the strips. CONSTITUTION:The inside size, i.e., intra-ring height Wh, of the transformer 10 corresponding to the thickness direction of the strip S with the heater for electrical heating of the strip S is set at least at >=100mm regardless of the width Sw of the other strip, the thickness St of the strip, the inside size (intra- ring width) Ww of the iron core corresponding to the transverse direction of the strip, and the size of the winding width Cw of primary windings. The uniform transverse heating corresponding to various kinds of the strips is possible in this way and the ring transformer 10 having high versatility is provided in this way.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a ring transformer for electrically heating a running strip in an apparatus for electrically heating a running strip to a predetermined temperature for various purposes, and more particularly for a ring transformer for electrically heating a running strip of various sizes and materials. The present invention relates to a versatile ring transformer for electrically heating a strip material, which can heat the material as uniformly as possible in the middle direction.

(Prior art) One of the joint applicants of Honmyo created an electrical heating device for running materials based on a new technical concept, and the invention directed to wire rods was published in Japanese Patent Application No. 61-272798 (Unexamined Japanese Patent Publication No. 61-272798). Showa 61128
No. 125), and an invention directed to a band material was filed in Japanese Patent Application No. 300127/1983. Both inventions are based on Figure 1 (a), which shows a device for processing, for example, strip material.
If explained according to (b), the current heating device 1
00 denotes a transformer 10 whose feeding passage passes through the ring of the annular iron core 11, a roll electrode 21 which is arranged close to both ends of the transformer IO and comes into contact with the strip material S on the feeding passage, for example, consisting of paired rolls a and b; 22, and both roll electrodes 2
The resistance R1 of the running heated strip material S between both roll electrodes 21.22 and the conductive material The relationship with resistor R2 of 3 is set to R1>>R2, and transformer 10
By supplying power to the primary winding 12 of both roll electrodes 21.
The gist of the present invention is to induce a secondary current in the strip S running between 22 and 22 with the conductive material 3.3 as a return line, thereby heating it.

(Problems existing in the prior art) By the way, the current heating device 100 does not cause any problems when heating a wire rod, but when implementing it when heating a strip material.

The problem of how to uniformly heat the interior has emerged. Also, even if the width and thickness of the heated strip material.

Even if a predetermined configuration is used to obtain uniform heating corresponding to the magnetic permeability determined by the material, the size range of the strip material that provides uniform heating is limited, and if the material of the strip material is different, even if the nine dimensions are the same, uniform heating will not be achieved. I can't get any heat. For this reason, it has been pointed out that it is necessary to prepare a large number of transformers each corresponding to nine different sizes of strips made of different materials, resulting in an increase in equipment costs.

(Purpose of the Invention) The present invention was made to solve the above-mentioned problems of the band material energization heating device, which is the invention filed in Japanese Patent Application No. 62-300127, and is compatible with band materials of various sizes and materials. It is an object of the present invention to provide a versatile ring transformer for energizing heating of a band material, which can heat the band material as uniformly as possible in the middle direction.

(Structure of the Invention) The gist of the present invention resides in a ring transformer for electrical heating of a strip material, characterized in that the inner dimension of the transformer corresponding to the thickness direction of the strip material is configured to be at least 100 mm or more.

(Example) The invention will be described in detail below with reference to FIG.

Each symbol in the figure indicates the dimensions of each part of the strip S, the iron core 1, and the primary winding 12 of the transformer 10, which are related to the present invention.

SW: Width of the strip St: Thickness of the strip WW: Core internal dimensions corresponding to the strip width direction = hereinafter referred to as ring inner dimensions Wh: Core inner dimensions corresponding to the strip thickness direction = hereinafter referred to as ring inner dimensions The winding thickness of the CW knee winding, which is called the height, and the conductor that makes up the -th winding are thin and the winding thickness is thin.
It has almost no effect on heating, so ignore it.

Therefore, in the present invention, the inner ring height wh is set to other dimensions, that is, Sw,
Regardless of the dimensions of St, Ww and Cw, they should be at least 100 mm or more.

(Function of the Invention) The present invention has an effect of reducing the influence of leakage magnetic flux from the secondary winding and promoting uniform heating in the width direction of the strip material, for each of various strip materials having different materials, widths, and plate thicknesses. be.

(Progress until completion of the invention) The present invention was completed through current density analysis during electrical heating, heat conduction analysis, and experiments using an actual machine.

(1) Current density analysis during energization heating: The density distribution of the current induced in the strip S by the transformer 10 during energization heating is determined by the width Sw of the strip S, the plate thickness St, and the winding weight CW of the next winding 12. , and the internal dimensions of the transformer IO (annual inner diameter Ww and height wh) were analyzed using a computer using the finite element method. Some of them are disclosed below.

Basic equation of electromagnetic equation In the above equation (1), if it is assumed that the x-y' one-dimensional field is isotropic and that A changes sinusoidally, then
Equation (1) becomes as follows.

・・−・−m=・−・−(2) However, A: Magnetic vector potential (W b / m)
Az: Z-direction component of magnetic vector potential (W b / m) Jo
: Forced current density (A/m2) Joz: Z-direction component of forced current density (A/m2) μ : Magnetic permeability
(H/m)σ: Electrical conductivity
(tr/m)ω: Angular frequency (ra
d/s)φ: Potential (V)A
, using the above formula (2), set the common analysis conditions and physical property values as follows, and take, for example, a steel strip that is a general material to be heated.The plate thickness St is constant 3 mm, but 3 mm in the pot
For each strip material whose w was changed from 250 mm to 500 mm in 50 mm increments, the widthwise surface current density 5 distribution of the strip material at the time of the strip material conductivity σ5 = 3XI06, that is, when the heating temperature is approximately 300 ° C. The values were calculated for each of the two transformers described below, which differ only in the inner ring height wh.

○Common analysis conditions and physical property values: f = 60 (Hz) μc = 6000 (relative magnetic permeability of the iron core) μw-1 (relative magnetic permeability of the -th winding) μ5 = 30 (relative magnetic permeability of the strip material) However, -The next winding current Joz is the average current density of the strip material is 1
．． It was set to be 0.times.IO' (A/m2).

○Transformer: Inside the ring Ww - = 560mm (constant) Inside the ring height Wh =
110mm, 310mm winding width Cw = 500mm
(Constant) Figures 3 (a) and (b) are surface current density J distribution diagrams from the center of the strip material to the edges, showing the analysis results when the inner ring height wh of the transformer is 110 mm and 310 mm, respectively. The numerical value written at the end of each curve in each figure indicates the width of the strip (unit: mm).

From the consideration of both figures, the following common points are found for the plate ff and the St3mm (7) strip material.

■Current density J is high on the edge side and low on the center side.

■Relationship between Cw in the winding and Sw in the pot: A. The deviation of the current density J distribution is (Cw) >> (3w) -...- Large (Cw)
> (S w ) −−−−−−−−−−−One maximum (C
W) = (Sw) -・-11---Small edge, tea towel S
The edge side responds sensitively to changes in w.

Furthermore, by comparing and considering both figures, the following becomes clear.

■When the inner ring height wh is high, the deviation of the current density 4 distribution is (Cw
)>>(Sw) and (Cw)>(SW).

■For the relationship (Cw) = (Sw), the inner ring height (
Even if wh) is high, the deviation of the four current density distributions does not improve, and on the contrary shows a slight tendency to increase.

B0 The present inventor further analyzed a steel strip having a thickness St different from that described above, and investigated whether the above-mentioned results were qualitative or not.

The analysis conditions are the same as those for the above analysis, and the plate thickness is St2mm.
Figures 4(a) and (b) show the analysis results for 5.
The analysis results for mm are shown in FIGS. 5(a) and 5(b) as current density J distribution diagrams, respectively. The case where the inner ring height of the transformer is whllomm is each (3),
The case of 310 mm is shown in (b).

Further, the numerical value written at the end of each curve in each figure indicates the width (unit: mm) of the strip material.

From Figures 4 and 5, it can be seen that although there are some differences in absolute values, the plate pJ
The same tendency as in the above considerations ■ to ■ for St3mm was observed, and the deviation of the current density 4 distribution was determined by the inner ring height wh
It was also found that (b), which has a high value, was far less than (a), confirming the qualitative nature of the study results.

The following conclusions are drawn from the above analysis results and considerations.

Originally, in energization heating, the deviation of the four current density distributions is large at the start of energization, and gradually becomes uniform as the temperature increases. This has been obtained from numerous analyzes and experimental results, including the above analysis. The accumulation of four current density distributions during the temperature process will accumulate the final heating result.

Therefore, if the analysis results are taken as a point in time during the heating of the strip material to a predetermined temperature, by increasing the inner ring height wh, the relationship between the width 3w of the strip material and the CW in the winding becomes at least as small as possible.

It is concluded that when (Cw)>>(Sw) and (Cw)>(Sw), it is possible to heat the various heated belt materials as uniformly as possible in the middle direction.

(Experimental Example) Next, the present inventor conducted a heating experiment using the electrical heating device 100, and compared the results with the above analysis results. Some of them are disclosed below.

In the experiment, the inner ring WW was the same 560 mm, and the height wh was 1.
Two types of transformers, 10 mm A and 310 mm B, were used, and both transformers A and B heated the same strip material, respectively. However, the applied heating conditions were changed in consideration of obtaining as uniform heating in the middle direction as possible depending on the size of the strip material.

Heating was carried out under static conditions by penetrating the specimen into the transformer, and when at least a portion of the specimen was heated to 500° C., the temperature of the surface in the middle direction near the exit of the transformer was measured using a thermocouple.

Table 1 shows the dimensions of each specimen, the winding (Cw), and the temperature measurement results for both transformers A and B, respectively.

From the same table, it is clear that B, which has a high inner ring height wh of the transformer, shows a tendency for uniform heating in the middle direction, regardless of the plate thickness St, even when heated by an actual machine, and the effect of the present invention can be verified. Ta.

(Other Examples) In order to ensure the accuracy of temperature measurement, the above experimental example was conducted with the specimen in a stationary state. However, the current heating device equipped with the transformer according to the present invention is Since the purpose is to heat the material to a predetermined temperature, the strip material will of course run at a predetermined speed between both roll electrodes 21 and 22 during actual operation.

In addition, the results obtained by the present inventor from analyzes and experiments other than those disclosed in this specification, that is, the relationship between 3w in the band and Cw in the winding, for example, when the plate thickness St is relatively thin, ( If the present invention is implemented in conjunction with a condition such that Sw=Cw) is optimal, or (Sw>Cw) is better as the plate thickness St increases, the above conditions can be relaxed.

(Effects of the Invention) By carrying out the present invention, it is possible to heat strips as uniformly as possible in the width direction in response to strips of various sizes and materials. It is awarded as a prize.

[Brief explanation of drawings]

FIG. 1(a) is a front view of an electrical heating device to which the present invention is applied, FIG. 1(b) is a sectional view taken along line X-X in FIG. 1(a), and FIG. 2 illustrates the present invention. Perspective views of the ring transformer, Figures 3 to 5 show computer analysis results (a) and (b), respectively, when strip materials of various thicknesses are heated by transformers with different internal dimensions in the thickness direction. It is a current density distribution map. 100.-----1--Electrification heating device 1
(L-----------・-・・・・・・-(Ring)
Transformer 11-・・・・・−・−−−−−One iron core 12・−・−・−・・−・・−−Primary winding 21.22・
−−−−−−One roll electrode 3・−−One−−・−・・−・
--1~---Conductive material L---1---1・
−・−・・−Feeding path S−・−1−−−−−・−・−−
−−−−−−One strip St・−・−・−1−−−−・Thickness of the strip material Wh−・・−−−−1−−・−−1−−−− In the plate thickness direction Corresponding transformer internal dimension patent distributor Nippon Steel Corporation Koshuha Netoren Co., Ltd.

Claims (1)

[Claims] A transformer in which a feed passage passes through the ring of a circular iron core, roll electrodes that are arranged close to both ends of the transformer and in contact with the strip material on the feed passage, and a conductive material that electrically connects the two roll electrodes. In the transformer of the heating device, which heats the strip running between the roll electrodes by inducing a secondary current with the conductive material as a return wire by supplying power to the primary winding of the transformer, 1. A ring transformer for electrical heating of a band material, characterized in that the internal dimensions of the transformer in the thickness direction of the transformer are at least 100 mm or more.