SU1748034A1 - Demagnetizer - Google Patents

Abstract

The invention relates to the non-destructive testing of longitudinally extended products, for example rods or pipes. The purpose of the invention is to increase; Sewing the quality of demagnetization of long cylindrical products by measuring the residual magnetization of the product and automatically adjusting the demagnetization current coaxially with it by windings 1, 8 measurements of the residual magnetization of the product 2, are connected in series and an integrator 3 with a voltage divider 4 with a variable division factor and an adder 5 whose output is connected to the input of an adjustable DC source 6, and a second integrator 9 whose input is connected to the output of the second winding 8 and the output to the second input of the adder 5 3 or with

Description

This invention relates to methods and means for non-destructive testing of longitudinally extended products, such as rods or pipes.

A device for demagnetization of products containing alternating current solenoids of various frequencies and adjustable sources of alternating current is known.

The frequency of demagnetization of the floor in these demagnetization devices depends on the thickness of the demagnetizing product. The thicker the product, the lower should be the frequency of the floor. So if in a field with a frequency of 50

Hz can be effectively demagnetized products with a thickness of 2-3 mm from a material with a coercive force of 10-15 A / cm, for demagnetization of products with a wall thickness (diameter) up to about 30 mm, the required field frequency is 1 Hz. This complicates the circuitry of these devices for by creating powerful generators with a very low frequency and dramatically reducing the speed of advancement of a bar or pipe, and thus the productivity of control

The closest to the invention of the technical nature and the achieved peVJ

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The result is a device for demagnetization of products containing a demagnetization winding and an adjustable DC source connected to the demagnetization winding

However, this device has a low quality of demagnetization of products due to the fact that there is no automatic adjustment of the demagnetization current Ј depending on the residual magnetization of the product, which depends on the product, which depends on the product on its length and the structure of the material. Moreover, constant contact is necessary for the stability of the residual magnetization. or the gap between the electromagnet and the product

The purpose of the invention is to improve the quality of demagnetization of long cylindrical products by measuring the residual magnetization of the product and automatically adjusting the demagnetization current.

The goal is achieved by the fact that a device for demagnetization of products, containing a demagnetization winding and registers and devices and a source of direct current connected to the demagnetization winding, is provided with two symmetrically positioned relative to the demagnetization winding and coaxially with the demagnetization winding, with a symmetric position relative to the demagnetization winding and coaxially with the demagnetization winding, which is located along the demagnetization winding and has coherent with the demagnetization winding and coaxially connected with the demagnetization winding. connected to the output of the first winding of the measurement of the residual magnetization of the product by a voltage divider with a variable division factor and total rum output of which is connected to the input of the adjustable constant current source and a second integrator whose input is connected to the output of the second coil remanence measurements of the article and an output connected to the second input of the adder

Fig. 1 shows the block diagram of the device for demagnetization of products, Fig. 2 shows the limiting loop and the partial cycle of the product hysteresis in Fig. 3, the residual magnetization plots along the product length.

The device for demagnetization consists of series-connected residual magnetization measuring coil 1 of product 2, integrator 3 of a voltage divider 4 with variable division ratio, adder 5 of an adjustable direct current source and winding 7 of demagnetization, measuring the residual magnetization of product 2 sequentially connected located with the winding 1 is symmetrical with respect to the demagnetization winding 7.

coaxially with it and after it in the direction of movement of the product, and the second integrator 9, the output of which is connected to the second input of the adder 5, Diagram 10 (Fig. 2) depicts the limiting hysteresis loop obtained by remagnetization of the ferromagnetic product, and Diagram 11 - the partial return loop obtained during demagnetization of the product (production B 0)

Diagram 12 (Fig 3) depicts the residual magnetization

magnetized ferromagnetic product along its length, figure 13 - residual

magnetization along the length of the product when the second circuit of the demagnetization current correction is open, diagram 14 - residual magnetization of the demagnetized product along its length

The device works as follows

In the initial state, the magnetized ferromagnetic product is switched by switching the maximum intensity

magnetic field Hp along the limiting loop of magnetic hysteresis (figure 10 in fig. 2) after removing the magnetic field has residual magnetic induction Br (point A in chart 10). Moreover, it is possible

magnetization of the product and along a partial symmetric hysteresis loop. From this diagram it is seen that for the complete demagnetization of a pre-magnetized ferromagnetic product (obtaining

magnetic induction B - 0) it is necessary to ensure that the magnetic field H0 (current B in diagram 10) is such that, after removing the demagnetization field, the residual magnetic induction of the part of the partial hysteresis loop (diagram 11 in Fig. 2) returns to the zero state

A product 2 of a certain length (Fig. 1) along the roll table is moved sequentially through the residual measurement winding 1

magnetization of the product, winding 7 demagnetizing and winding 8 measuring residual magnetization of the product. Since the product was previously magnetized, a signal proportional to the rate of change of the magnetic flux appears at the output of the winding 1 for measuring the residual magnetization of the product.

-W

d ° -WSdB

dt

dt

ABOUT)

where I is the instantaneous electromotive force;

d F- change in a short time dt of the total magnetic flux;

W is the number of turns of the winding;

S - winding area

From expression 1 it can be seen that the emf of the output signal of the winding measuring the residual magnetization of the product is proportional to the residual magnetic induction of the product.

Therefore, the signal received by the passage of the magnetized product 2 through the winding 1 at the output of the latter is transmitted to 6 integrator 3, the output signal of which

(t)

(2)

is obtained directly proportional to the residual magnetic induction (diagram 12 in Fig. 3) and through a divider 4 voltage with a variable division factor is applied to one of the inputs of the adder 5, the second input of which through the integrator 9 receives a signal from the winding 8 measuring the residual magnetization of the product. The output signal of the adder 5, equal to the sum of the input signals, controls, via an adjustable direct current source, the demagnetization current in the winding 7

The initial demagnetization current was set as follows.

A pre-magnetized solid product is inserted into the demagnetizing zone and by changing the division factor of the voltage divider 4 at the output of the regulated constant current source exposes such demagnetization current so that the residual magnetization curve of the standard along its length is minimal and symmetrical about the axis ( diagram 13 in FIG. 3) In this case, the second control loop, consisting of the second winding 8 of the measurement of the residual magnetization of the product, the integrator 9 and the second input of the adder 5 should t open. After this, the second control loop closes, which is needed because the hysteresis loops of different samples may differ slightly from the reference, and the transfer coefficient of the first circuit is established based on the dependence of the difference (Br) for the reference. Therefore, there may be a magnetization reversal and undereflection of the product. The device is ready for operation in the automatic degaussing current control.

Now, if in the demagnetization zone there appeared a product with a non-uniform structure along the product length and different from the standard, by which the expansion device was tuned, then at the output of the first measuring winding 1 measuring the residual magnetization of the product the signal will be different from the previous one, which through the integrator 3 and divider A voltage

0, the variable division factor will be fed to the output of the adder 5, the changed signal of which will correspondingly change the demagnetization current of the regulated source 6 of the direct current. Now, if the magnification and remapping of the product occur, then this will be signaled by the output signal of the second winding 8 of the residual magnetization measurement of the product, which through the integrator 9

0 and the second input of the adder 5 will correct the demagnetization current (chart 14 in Fig. 3).

A device for demagnetization of products allows improving the quality of demagnetization of products at any preliminary degree of magnetization in particular hysteresis loops by measuring the residual magnetization of the product and automatically controlling the demagnetization current.

Claims (1)

Claims An apparatus for demagnetizing products comprising a demagnetize winding and an adjustable DC source, 5 connected to the demagnetization winding, characterized in that in order to improve the quality of demagnetization of long cylindrical products, it is equipped with two symmetrically located with respect to the demagnetization winding and coaxially with it the windings of the residual magnetization measurement of the product, connected in series by an integrator connected to the output of the first 5 windings for measuring the residual magnetization of the product, a voltage divider with a variable division factor and an adder, the output of which is connected to the input of an adjustable DC source, and a second integrator, the input of which is connected to the output of the second winding measuring the residual magnetization of the product and the output with the second input of the adder five Zw. five.