RU2695392C1 - Method of increasing impact strength of metals - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metal processing and can be used for parts reconditioning and hardening. To increase the article operational resistance, an article is installed in the inductor, in which fatigue cracks are formed by means of clamping rings. Depending on the material, current passage value is set. After installation of the article in the inductor, current is started to flow, and the eddy currents have perpendicular direction relative to the cracks.

EFFECT: as a result of passage of current the most heated point is the crack vertex, accordingly, it is subjected to maximum micromillation and "baking".

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Description

The invention relates to the field of metalworking and can be used to restore and harden parts.

The durability of parts is mainly affected by their defects, including technological ones, which in turn reduce such an important characteristic of any material as impact strength. It is she who is the main indicator of the ability of a material to absorb mechanical energy in the process of deformation and fracture under the influence of shock loading. Defects that occur during the operation of parts in a structure can lead to the appearance and development of fatigue cracks. Continuity defects directly reduce the fatigue strength of the material and the durability of the parts, reducing the strength and service life of the machines, and hence the toughness.

A known method of hardening by induction surfacing of parts (RF patent for the invention No. 2138377, IPC B23K 13/01, B22D 19/00, publ. 09/27/1999), including applying depressions to the working surfaces, filling them with reinforcing material and then applying powder to the surface of the parts charge, while the recesses are reinforced with a granular alloy of tungsten carbides, and as a powder charge using a mixture comprising 80% cobalt alloy and 20% boron flux, the thickness of the layer of the charge is 2-3 mm in the following ratio of alloy tungsten carbides and powder mixture, wt. %: Tungsten carbide alloy - 40-60, Powder charge - 60-40.

The disadvantage of this method is the use of additional powder mixtures and alloys, which are deposited on the recesses deposited in the part, i.e. the method is more used for hardening parts working in an abrasive under shock or high dynamic load conditions, which may not be suitable for parts serving for other purposes, and in need of surface preservation without unnecessary roughness and unevenness.

The closest analogue is the method of processing products (RF patent for the invention No. 2068003, IPC C21D 1/04, C21D 7/06, publ. 10/20/1996), including cooling in liquid nitrogen, and, in order to increase operational stability, after cooling the product additionally subjected to treatment with a periodic magnetic field with a strength of less than 10 ⁶ A / m

The disadvantage of the described method is the practical absence of the hardening effect for a well-hardened product, as well as the need to use liquid nitrogen, which requires certain storage conditions.

The objective of the proposed technical solution is to increase the operational stability of products.

The problem is solved due to the fact that the method of increasing the impact strength of metals, including exposure to the treated surface of the products is produced by a pulsed magnetic field, and the eddy currents induced in the product have a direction perpendicular to the fatigue cracks formed on the surface of the product, and the magnitude of the eddy currents when exposed to cracks is important, providing micro-melting of the metal at the tops of these cracks.

Exposure to a pulsed magnetic field (IMF) with eddy currents perpendicular to the cracks induced in the product minimizes the further development of these cracks, which directly affects the operational stability of the product.

The magnitude of the eddy currents should be adjustable in such a way as to ensure only micro-melting of the metal at the tops of the cracks. If the current strengths are too high, a general overheating of the sample can occur, and radial electrodynamic forces can lead to general destruction of the product.

A device for implementing the method is represented by the following drawings:

- in FIG. 1 shows a cross-sectional front view of a diagram of a device for implementing the method;

- in FIG. 2 shows a sectional view of the left diagram of the device for implementing the method;

- in FIG. Figure 3 shows the movement of eddy currents in the crack region.

The device comprises an inductor 1 connected to a magnetic pulse installation (MIU) and containing a current lead 2, coupling rings 3 and product 4.

The implementation of the method is carried out in the invention as follows.

An article 4 is installed in the inductor 1, in which fatigue cracks are formed using the clamping rings 3. Depending on the material, the current passage is set. After installing the product 4 in the inductor 1 begin to induce current, and eddy currents have a perpendicular direction relative to the cracks. As a result of the passage of current, the most heated point is the tip of the crack, respectively, it is most subjected to micro-melting and “baking”. For a material of the 30KhGSA grade, the current most suitable for increasing the impact strength and “baking” cracks is 84–100 kA, and for an AMG6 material from 20 kA to 40 kA.

Claims (1)

A method of repairing parts with surface cracks, including applying a magnetic field to the surface of the products, characterized in that the effect is produced by a pulsed magnetic field, wherein the product is clamped with clamping rings in the inductor so that the eddy currents are perpendicular to the formed fatigue cracks on the surface of the product, and the magnitude of the eddy currents when exposed to cracks has a value from 20 kA to 100 kA.

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