SU2944A1 - Method and device for detecting pits in metal products - Google Patents

Description

The use of x-ray transmission of metallic objects to detect shells in them is well known, however, such translucency requires sophisticated equipment and high-power high-voltage transformers to take pictures from any thick layer of steel and is not satisfactory. items. The proposed method is based on a compensation method for measuring small amounts of radioactive substances using -7 rays and can be used for radiography of both thick steel products, theoretically up to 40 sl1, and thin rods or even wires.

In FIG. 1 schematically depicts a compensation electroscope and FIG. 2 is a schematic of a translucency device.

The indicated method of compensation of the discharge current of an electro-current by a current in an emanation chamber consists of the following. An emanational copper chamber IS, much smaller, than the electroscope, of dimensions and separated from it by a tarame, is placed above the usual, internally lined lead ™ V -electroscope A (Fig. 1). Unlike an ordinary emanation electroscope, the outer lining of the chamber is connected not with the ground, but with a potential of 200–300 V more high than the charging potential of the electroscope. A certain amount of emanation of the order of 10 Curies is introduced into the emanation chamber. For more accurate measurements, it is better to evaporate the appropriate amount of solution at the bottom of the emanation chamber. The ionization current through the chamber will charge the electroscope sheet. One of the compared preparations for the sake of is placed at such a distance from the scale that the discharge current of the electroscope is exactly equal to the charging current of the chamber and the sheet would remain on one particular division of the scale of the electroscope. Then, gradually removing the 1st preparation and the second tray, compensate the current of the chamber by the ionization current from the second preparation. The ratio of the number ttlg, metal ligram will be equal to the inverse ratio of the squares of the distances

Bf

.e

t,

Before proceeding to measure, it is necessary to clarify the limits in which the change in the intensity of the ionization current obeys the law of squares of distances

this goal is observed in the usual way the falling of the sheet by pa of different distances, measured from the geometric center of the electroscope, and panosits curve 1 (11 Iff - 2 Iff R. Measurements can be made only to the extent that the indicated dependence is expressed by a straight line. For an electroscope , with which the experiments were performed, the indicated dependence was fully observed even at a distance of 40 cjn. The observation error when using the described method is very small. Moving the drug for 0.5 lx quickly causes a noticeable deviation of the piece, 50 cm of distance gives an error of 0.1%. If we denote the discharge currents from the first and second drugs through / 1 И / 2, through / - the current in the chamber and through r - the parasitic current through the current, then А + «/ , / 2 +, whence: / i / 2, no matter what sign and what magnitude this parasitic current is, provided, of course, that does not change during the observation, as can be seen by repeated measurement. Thus, the correction for natural scattering when using this method disappears, no, therefore, and an additional error, depending on the exact definition of natural scattering no. The issue of saturation current for both drugs is also not the case here, because / 1/2. A comparison of the activity of two weak drugs, caused by currents (1 and 2) in the electroscope, is made as follows. Let any preparation compensate for an installation without a substance that needs to be compared at a distance R. If at the first measured preparation a compensating preparation is placed for the distance Ld, and at the second at the distance Hn, then we have the equations:

r I 0 -o ,,} I L)

1 + a: d 2 + / 4 M, whence

7, (- ДЗ) Да1у (Д / Щ

Below is an example of an elementary calculation of the limiting case of the proposed method. It is required to determine the presence of a shell with a thickness of 1 sgl in a piece of rectangular steel, 40 cm thick. When calculating, it is derived from the following data. For steel (iron) with a density of 7,6, the thickness D of the layer, which reduces by half the intensity of the hardest rays from 6, is 2.28 cm. Such layers in a 40 cm slab are placed slightly less than 18 (40: 2.28). Then the attenuation of the intensity / source at the rays from 40 cm of the plate will express coeffitiento (1: 2) (1: 262144). The attenuation / o, depending on the distance, is expressed by the coefficient (5: 40), t (1: 8) 1: 64 ,; where 5 cm is the closest distance from the center of the electrometer at which the radiation source can be located. At a distance of 5 cm, the sensitivity of the installation with a conventional coarse electroscope is 10 g for the sake of metal. A complete decrease in the radiation intensity, depending on the square of the distance and on absorption in the thickness of the slab, will be (1: 64) X X (1: 2.6. 10 °) - 1: 1, X 10. The ionization current will be:

7

 0.6 ./- 10-

/:

1.6-10

The calculation was made for the case / o from 1 g for the sake of or from an emanation corresponding to the strength of the preparation; the experience will probably give some worse results. With this calculation, the complexity of the beam of hard j-rays was not taken into account. In fact, with such large thicknesses, only the hardest components of the Y rays of Ra C will be used, but, on the other hand, it is possible to go further in increasing the sensitivity; way applied

thinner measuring instruments than an ordinary electroscope.

The installation of instruments and methods of operation for the proposed method are as follows. The electroscope 7 is placed on a stationary table 2 (Fig. 2), under the electroscope on the table 4 is placed the test body 3, which has a translational and rotational motion. Even lower, on a plumb line with an electroscope, is placed the preparation 5 for the sake of or emanation. The electroscope sheet (electrometer thread, etc.) is compensated for by the current in the electroscope chamber and: for the preparation, on the BI side, so that the sheet becomes stationary in the field of view of the microscope or telescope. The test body is given a rotational or translational motion in the horizontal plane, according to its geometric shape. As soon as there is a sink between the radium and the electroscope, the ionization current will increase and the electroscope sheet will deviate from the equilibrium position. By changing the distance to the side of the preparation for emanation or emanation, one can measure the change in the ionization current and get an approximate idea of the total volume occupied by the sink. To test a particular type of product, the installation can be simplified or tailored for that purpose. So, when scanning blanks for wires, it is enough to give the rod a translational motion, and when scanning the walls of the pump, it is necessary to give it, besides the translational movement, and rotational around the axis, and it is desirable to place the preparation for the inside of the mouth, etc. production is very fast, and only a small amount of time is required to determine the sink volume.

SUBJECT OF THE PATENT.

1. The method of detecting cavities in metal products, characterized by the fact that 7-rays for the sake of or emanation, passed through the test material, are taken to the ionization measuring device and, by changing the ionization current during movement and rotation of the test object, the presence of shells in it, To measure the same size of the shells, additional, with different distances, compensation for a separate preparation for the sake of is used.

2. To implement the method described in paragraph 1, the device is characterized in that it consists of a compensation electroscope / mounted on a stationary table 2, directly above the test body 3 above translational and rotational movement above the table 4, placed 5 drug for the sake of or emanation, on the same plumb line with an electroscope.

3. In the device described in item 2, the use of a compensation electroscope consisting of a conventional lead-lined 1B1 inside, 7-electroscope A, equipped in its upper part with an emanation, smaller size, copper chamber B connected to an electric source of potential 200- 300 U and with a certain amount of emanation or a different emitter placed inside it.

Tipo-lithograph “Red Geechnik, Leningrad, International, 75.

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FIG. I,

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