RU2727780C1 - Method for determining depth of penetration of electromagnetic field into metal - Google Patents

Abstract

FIELD: physics.SUBSTANCE: invention relates to electromagnetic control methods. Method for determining penetration depth of alternating electromagnetic field into metal includes successive introduction into alternating magnetic field of screens of different thickness and selection of standard screen, in which change of field parameters is stopped, wherein reference is heated simultaneously with sample-witnesses of flat or cylindrical section with thickness from smaller depth of current penetration into metal to higher, wherein the current penetration depth into the metal is determined from the distribution of hardness on the cross-section of the witness and reference sample.EFFECT: reduction of labor intensity and simplification of hardware design at induction deposition and heat treatment of thin-walled parts and billets.1 cl, 1 dwg

Description

The invention relates to electromagnetic control methods in welding and can be used for hardening by induction surfacing of working bodies of soil-cultivating, forage-making machines and forage harvesters.

A known method for determining the depth of penetration of an electromagnetic field into a metal (analogue) based on a theoretical calculation of measurements of the parameters of the emitter, depending on the thickness of the metal workpiece, electrical conductivity and magnetic permeability, as well as the frequency of the electromagnetic field [Dorofeev L.A. and others, Theory and industrial application of the eddy current method, M., "Mechanical Engineering", 1969, p. 17-22].

However, the accuracy of determination by this method is relatively low, since the known inverters used for heating billets during induction surfacing and heat treatment have a frequency range that varies depending on the load of the inductor with billets having a thickness difference in the rolling process (GOST 19903-74), up to 1 mm, and the proposed method fixes the depth of penetration of the electromagnetic field into the metal only for a certain frequency.

The closest in technical essence to the proposed invention is a method for determining the depth of penetration of an electromagnetic field into a metal, which consists in the fact that screens of various thicknesses are introduced into the investigated electromagnetic field and the depth of penetration through the thickness of the screen is determined, at which changes in the parameters of the electromagnetic wave emitter stop ( A.s. 868656, 09/30/1981, prototype).

The disadvantage of the known method for determining the depth of penetration of the electromagnetic field into the metal is the high labor intensity and complex hardware design.

The problem solved by the present invention is to reduce labor intensity and simplify the hardware design for determining the depth of penetration of an electromagnetic wave into a metal.

The technical result of the implementation of the proposed method for determining the penetration depth of the electromagnetic field into the metal by the technological breakdown is to reduce the labor intensity and simplify the hardware design for induction surfacing and heat treatment of thin-walled parts and workpieces.

This result is achieved by the fact that in the method for determining the depth of penetration of an alternating electromagnetic field into a metal, including the sequential introduction of screens of various thicknesses into an alternating magnetic field and the choice of a screen-reference in which the change in field parameters stops, the reference is heated simultaneously with the witness samples of a flat or cylindrical section , with a thickness from a smaller depth of current penetration into the metal to a larger one, while the depth of current penetration into the metal is determined by the distribution of hardness over the cross section of the witness sample and the standard.

The technical result of the invention is achieved due to the following:

- reduction of labor intensity when optimizing modes of induction surfacing or heat treatment;

- the thickness of the penetration of the electromagnetic field into the metal is determined by the reference sample and the samples - witnesses made of the same steel grades placed simultaneously in the same electromagnetic field;

- simplified hardware design, due to the use of shop equipment - an inverter for heating the technological sample and a hardness tester for determining the hardness and surfacing materials for induction surfacing.

FIG. 1 shows a standard sample and witness samples in an inductor connected to an ELSIT-100-70 / 40 inverter.

1. - inductor; 2, 3, 5, 6 - witness samples; 4 - standard; 7 - asbestos substrate.

The method for determining the depth of penetration of the electromagnetic field into the metal is carried out as follows. On the asbestos substrate 7, placed in the inductor 1, place the sample standard 4 and at equal distances from it to the left, witness samples 2 and 3 with a cross-section greater than the penetration depth of the electromagnetic wave into the metal are placed, and to the right of it, witness samples 5 and 6 having the cross section is less than the depth of penetration of the electromagnetic wave into the metal.

An ELSIT-100-70 / 40 inverter was used as a radiator of high-frequency electromagnetic waves, to which a solenoid inductor was connected.

Example 1. In the inductor, there was a standard sample made of 65G steel (20 * 12 * 5.5 mm), on which, previously, a surfacing charge was poured through a stencil with dimensions of 10 * 6 * 4 mm (hard alloy PG-US25- 85%; flux P-0.66 - 15%) with a thickness of a poured layer of 2.0 mm, and thus witness samples were prepared, but having a different thickness in cross section, less than the thickness (4.5 and 3.5 mm) of penetration to the thickness of its larger (6.5 and 7.5 mm). Simultaneously, a reference sample and four reference samples with different cross-sectional thicknesses were placed in the inductor. The surfacing charge was heated and melted on the test specimens at a fixed time of 60-62 s.

After cooling of the samples, the quality of the surfacing was assessed visually. On specimens where the thickness of the cross-section is less than the depth of penetration of the electromagnetic field into the metal, melting of the surfacing charge did not occur. On the reference sample, the quality of the deposited layer was satisfactory. Specimens with a cross-sectional thickness of 6.5 mm had high-quality surfacing, and on a specimen with a thickness of 7.5 mm, separate bare areas were formed on the surface to be welded, due to significant overheating of the alloy being hardened. Thus, six tests were carried out.

Example 2. A standard sample and witness samples were cut out of 65G steel, structurally made in the form of cylinders (40 mm long): standard sample with a diameter of 5.5 mm, and witness samples with diameters of 3.5; 4.5; 6.5 and 7.5 mm, 6 pieces each. Then they were heated in a solenoid inductor in a longitudinal electromagnetic field simultaneously for 50-53 s. Then it was cooled in water. The hardness of the hardened samples was determined by the Rockwell method. On samples: the standard and with witnesses with a diameter of 6.5 and 7.5 mm, it corresponded to HRC 60-62, and with a diameter of 3.5 and 4.5 mm it was HRC 32-44.

The proposed method for determining the penetration depth of the electromagnetic field into the metal by the technological breakdown allows one to determine the minimum thickness of the workpiece or part for which this frequency of the electromagnetic field of the inverter will provide effective heating during heat treatment and melting of the hardened material on the surface of the part during induction surfacing.

Claims (1)

A method for determining the depth of penetration of an alternating electromagnetic field into a metal, including sequential introduction of screens of various thicknesses into an alternating magnetic field and the choice of a reference screen, in which the change in field parameters stops, characterized in that the reference is heated simultaneously with the witness samples of a flat or cylindrical section with a thickness from a smaller depth of current penetration into the metal to a greater one, while the depth of current penetration into the metal is determined by the distribution of hardness over the cross section of the witness sample and the standard.

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