RU2636269C1 - Method of producing magnetic and electromagnetic screen - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: tapes are laid between two polymer dielectric films heated to a temperature sufficient for double-sided adhesion of a polymer dielectric film with a metal tape, and subjected to joint moulding. The metal strip is subjected to a preliminary heat treatment at temperatures of 300-380°C for 5 to 90 minutes to create a positive saturation magnetostriction state due to the formation of a nanocrystalline structure, while during moulding a tensile stress of 1-100 MPa is applied to the strip, and immediately after moulding, the metal-polymeric material is cooled from the moulding temperature down to a temperature of 10-20°C below room temperature, held for 10-60 minutes and after holding the external tensile stress, applied to the tape, is simultaneously relieved and the material is heated up to room temperature.

EFFECT: increase in the magnetic permeability of the material and the screening coefficient.

2 cl, 1 tbl

Description

The invention relates to methods for creating composite materials based on amorphous and nanocrystalline alloys to protect technical and biological objects from constant and variable fields of industrial frequency.

Today, increasing the level of man-made magnetic (MP) and electromagnetic fields (EMF) is an urgent problem due to the possibility of causing negative consequences for the life of biological objects, including humans, up to ecological scales, as well as causing malfunctions in the electrical and electronic equipment, and therefore the task of ensuring electromagnetic compatibility (EMC) of various devices. To regulate the maximum permissible values of constant and variable magnetic fields in Russia and abroad, normative documents are being developed, which include various directives, sanitary standards for the population and maintenance personnel, standards in the field of EMC, etc., forcing equipment developers to look for ways to protect against MP and EMF, providing the necessary attenuation of the field.

Often the most effective and appropriate way to protect technical objects in order to ensure EMC, as well as biological objects, is passive shielding using special materials. For the manufacture of low-frequency screens (operating frequencies less than 300 kHz, as well as constant fields), materials with high magnetic permeability are used. Traditionally, materials such as electrical steel, permalloy, μ-metal, etc. are used for this purpose. However, due to the constant tightening of requirements, these materials do not have a set of magnetic and mechanical properties to meet these requirements.

Promising materials in this direction are amorphous and nanocrystalline soft magnetic alloys based on cobalt and iron, obtained by ultrafast melt quenching (spinning) in the form of a thin tape, about 20 microns thick. Such freshly hardened alloys possess properties that in some cases exceed the properties of traditional crystalline materials and are less sensitive to mechanical deformations during installation. Subsequent heat treatment can further increase the magnetic permeability of the alloys due to the removal of quenching stresses and partial nanocrystallization of the tape. However, due to the limited width of the tape and its fragility, it is necessary to search for methods of its installation when shielding objects.

One of the technical solutions for attaching tapes during shielding is to obtain a flexible metal-polymer screen, where the dielectric polymer film performs both mounting and protective functions, and currently there are patents for rolled composite metal-polymer screen, such as JP 11087989, JP 2004071735, RU 2274914 and the production method of such a screen RU 2375851.

However, according to available data, any coatings applied to soft magnetic alloys can lead to a decrease in magnetic permeability. For example, the manufacturer of amorphous alloys and magnetic cores based on them, Mstator OJSC (Borovichi, Russia), notes that applying epoxy powder paint to a magnetic conductor made of amorphous alloys leads to a significant deterioration in its magnetic parameters due to shrinkage stresses of the polymer [1].

Existing studies indicate that the applied coatings are magnetically active, that is, by creating additional stresses on the surface of the tape, they form the corresponding distribution of magnetization over the volume of the tape and, as a result, the final magnetic properties. Thus, studies conducted in [2] for an amorphous Fe – B – Si – C alloy with positive saturation magnetostriction showed that organic coatings create compressive stresses in the tape, which also lead to a decrease in magnetic permeability due to the redistribution of magnetization over the tape volume under the influence of stresses.

Thus, well-known technical solutions, including the prototype RU 2375851, do not allow to obtain a composite screen with a sufficiently high magnetic permeability due to its decrease when applying the coating to the heat-treated tape and, as a result, do not allow to achieve potentially possible shielding properties.

The technical result of the invention is to maintain and increase the magnetic permeability and screening coefficient of the composite magnetic protective shield.

The technical result is achieved by applying a dielectric polymer film to an amorphous tape of the Co-Ni-Fe-Cr-Si-B-Mn system, which has undergone preliminary heat treatment, under the influence of simultaneous heating to create better adhesion and tensile stresses applied along the tape axis, leading to the redistribution of magnetization along the axis of the tape and contributing to an increase in magnetic permeability. There is a formula linking the sensitivity of the magnetic properties of a material with applied external voltages [3]:

where S _m is the coefficient of sensitivity of magnetic properties to mechanical stresses; μ is the magnetic permeability; dμ - change in magnetic permeability; σ _k - mechanical tensile stress.

Based on formula (1), the lower the sensitivity of the magnetic properties of the alloy to external mechanical stresses, the greater the external stress must be applied to obtain the effect of changing properties. In this case, also to increase the effect of the influence of external mechanical stresses during coating, it is possible to apply additional mechanical pressure perpendicular to the plane of the tape, orienting the magnetization in the plane of the tape, and also increasing the adhesion of the coating. However, when applying stresses, it is necessary to remain in the elastic region of the tensile diagram of the alloy, avoiding the formation of micro-discontinuities and fracture of the alloy, leading to irreversible degradation of the magnetic properties, therefore, to obtain a technically significant effect, it is proposed to apply an external tensile stress of 1-100 MPa, and additional mechanical pressure, if necessary, in the range of 0.5-10 MPa.

In this case, the task of preliminary heat treatment is to remove quenching stresses, as well as to create a state of a tape with positive saturation magnetostriction, since, according to [4, 5], this characteristic for amorphous alloys is structurally sensitive and can be controlled by setting special heat treatment modes. A change in the sign of magnetostriction according to this work was detected at temperatures of the order of 350 ° C.

Further, after coating, it is necessary to cool the resulting composite material, and to temperatures below room temperature by 10-20 ° C, while maintaining the effect of tensile stresses along the axis of the tape. At this stage, the heated deformed polymer shrinks and naturally narrows, leading to compressive stresses at the film-tape interface, however, due to tensile stresses applied to the tape, stress relaxation during holding occurs without reorienting the magnetization in the orthogonal direction and does not reduce the magnetic permeability. Further, after holding at a low temperature with the simultaneous action of tensile stresses, these stresses are removed and the material is heated to room temperature. In this case, a slight natural expansion of the dielectric polymer film occurs, leading to additional tensile stresses in the plane of the tape and the orientation of the magnetization in this direction, which helps to maintain or increase the magnetic permeability and the screening coefficient.

Examples of the invention are presented in Appendix 1.

Information sources

1. www.mstator.ru

2. V All-Union Conference "Amorphous precision alloys: technology, properties, applications." Gorlanova M.A., Skulkina N.A., Khanzhina T.A., Shirokova E.A., Ivanov O.A. Rostov the Great: b.n., September 23-27, 1991. The effect of the electrical insulation coating on the magnetic and electromagnetic properties of the amorphous alloy Fe81B13Si4C2. p. 86-87.

3. V. B. Ginzburg. Magnetically controlled sensors. - Moscow: Energy, 1970, 72 p.

4. Ivanov, O.G. Aftoref. dis. Ph.D. Features of the formation of physical properties and the development of new amorphous soft magnetic alloys based on cobalt. b.m .: MSTU im. N.E. Bauman, 2004

5. Kekalo I. B., Mogilnikov P. S. The effect of bending stresses on high-frequency magnetic properties and their temporary stability in an amorphous cobalt-based alloy with very low magnetostriction. Journal of Technical Physics. 2015, T. 85, 12, pp. 80-87.

Claims (2)

1. A method of obtaining a magnetic and electromagnetic screen using tapes of soft magnetic alloys, in which the tape is placed between two polymer dielectric films, heated to a temperature sufficient for double-sided bonding of a polymer dielectric film with a metal tape, and subjected to joint molding, characterized in that the metal tape subjected to preliminary heat treatment at temperatures of 300-380 ° C for 5-90 min in order to create a state with positive magnetostriction saturation due to the formation of a nanocrystalline structure, while during molding a tensile stress of 1-100 MPa is applied to the tape, and immediately after molding the metal-polymer material is cooled from the molding temperature to a temperature of 10-20 ° C below room temperature, is held for 10-60 minutes Exposure simultaneously removes external tensile stress applied to the tape, and the material is heated to room temperature. 2. A method of producing a magnetic and electromagnetic screen according to claim 1, characterized in that during the molding of the material, a mechanical pressure of 0.5-10 MPa is applied, which is removed upon final heating to room temperature.