SU1093398A1 - Method for reconditioning components with internal hollow - Google Patents

Abstract

THE METHOD OF RESTORING DETAILS WITH THE INTERNAL CAVITY, which involves installing a part on the mandrel, magnetic impulse pressing of the powder layer onto the outer surface of the part, sintering and mechanical processing, differing from the fact that, in order to improve the efficiency of the process by excluding the shells metal, before the magnetic pulse pressing of the powder layer, the part is compressed on the mandrel and placed in the cavity of the matrix, and the pressing is carried out by distributing the part in the cavity of the matrix, at ohm the radius u of the mandrel is chosen from the conditions (i-a N iz mec.L AAVhl)) and the radius of the cavity of the matrix from the condition b,,) Opr SLLP. Od where RM is the nominal inner radius of the part, 9, 9,, 0 / j, respectively, the density of the powder in the backfill state, after pressing and sintering,; ; respectively start on machining of the inner and CO 00 outer surfaces of the part; oo wear rate H-JH Hg nominal thickness CX) details.

Description

The invention relates to powder metallurgy, in particular, to methods for restoring machine parts with metal powders and can be used to restore the internal surfaces of thin-walled cylindrical parts.

There is a known method for restoring the inner surfaces of cylindrical parts, including placing the powder in the cavity of the part and its rotation with simultaneous induction heating ij.

However, the application of this method is limited by the complexity of the induction heating of parts from non-ferrous metals. In addition, to restore small diameter parts, it is necessary to ensure high rotational speeds, which in some cases is very difficult.

There is also known a method of restoring worn surfaces of cylindrical parts by the method of magnetic-pulse pressing of powder and subsequent sintering. According to this method, the powder is loaded into the cavity between the inner worn surface of the part and the electrically conductive sheath, it is compacted with the energy of a pulsed magnetic field, the sheath is removed, the sintering of the formed layer and the subsequent mechanical treatment of the resulting coating 21,

However, this method does not allow the material to be used as it is worn. This circumstance significantly limits the scope, as in a number of cases. It turns out to be very difficult to ensure the physicomechanical and operational properties of the powder coating, the completely identical properties of the monolithic part.

The closest to the invention to the technical essence and the achieved result is a method of restoring parts with an internal cavity, including mounting a part on a mandrel of nominal internal size of the part, placing powder between the outer surface of the part and coaxially installed electrically conductive sheath with magnetic impulse pressing simultaneous compression of the part on the mandrel, removal

shell, sintering and machining of the restored parts s1. J A significant disadvantage of this method is the need to use electrically conductive shells made of non-ferrous metal (copper, aluminum, brass, bronze), which is due to the inability to compact the powder by directly acting on a pulsed magnetic field. This is due to the extremely low electrical conductivity of the powder in the free filling state.

The aim of the invention is to increase the efficiency of the process by eliminating non-ferrous metal shells.

The goal is achieved in that according to the method of restoring parts with an internal cavity, which involves installing a part on a mandrel, magnetic pulse pressing of the powder layer onto the outer surface of the part, sintering and mechanical processing, before the magnetic pulse pressing of the powder layer, the part is pressed onto the mandrel and placed into the cavity dies, and pressing is carried out by distributing the part in the die cavity, the radius of the mandrel being chosen from the condition

opr n / lehl a bo S) .i mech.g

.a radius R of the cavity of the matrix of

g, 0 Ym opr from “about yien me) (. 21)

where Р „- nominal internal

part radius;

QjS.Gj-, respectively, the density of the powder in the state of filling, after

pressing and sintering;

..o accordingly allowance

for mechanical processing of the internal and

external surfaces of the part; And wear rate of wear,

H -, nominal thickness is 5 parts.

FIG. 1 shows the position of the external inductor, part and mandrel before the part is crimped; in fig. 2 - the location of the crimped part in the cavity of the matrix; FIG. 3 shows the location of the part and the internal inductor in the cavity of the matrix after the distribution of the part J in FIG. 4 - part with pressed and baked powder layer. The proposed method is as follows. The sleeve 1 (Fig. 1) is compressed by a pulsed magnetic field with the help of inductor 2 onto the mandrel 3. Then the mandrel is removed, and the sleeve 1 is placed into a cylindrical cavity of a rigid matrix 1 4 (Fig. 2). Powder 5 is placed in the gap between the surfaces of the sleeve and the die, and magnetic impulse pressing is performed by distributing sleeve 1 by using an internal inductor 6 (Fig. 3). The sleeve 1 with the pressed layer 5 is removed from the matrix 6, sintering and sintering the powder is performed at a temperature of (0.8-0.9) TP (TRD is the melting temperature of the materialtala powder) and mechanical processing of its external and internal surfaces (Fig. four). Example. The inner surface of the cylindrical bronze thin-walled bushing of the upper head of the connecting rod of the YaMZ-236 engine was repaired. Bronze-graphite powder of the BGrZ type, 2, was used to press-in the mold: Rf, 25 mm ymehm. 2 2 mm; b 0.38; e, 0.8, - 02 0.9; & Yen 0.3 mm; H 3 mm. Calculations by the formulas give KO „Р% 24,0 mm; RM 28.7 mm. The sleeve was compressed by the magnetic-pulse method on a steel mandrel with a radius of 24 mm. The installation was used Impulse-A. The discharge energy was 8.2 kJ. After removing the mandrel, the sleeve was installed in the cylindrical cavity of the steel matrix (RM 28.7 mm), powder was poured into the sample gap between the latter and the outer surface of the sleeve, and sealed it on the vibrator (frequency 50 Hz, amplitude 0.2-0.3 mm ) to a density of 0.38. A cylindrical inductor working in distribution was placed in the cavity of the sleeve, and a magnetic-pulse pressing of the powder onto the outer surface of the sleeve was carried out by distributing it onto the matrix. The energy of discharge, ensuring the density of the powder after pressing b, 0.71-0.81, was 9.8 kJ. After pressing, the sleeve with the pressed-up powder layer was removed from the matrix and the powder was sintered in an endogas atmosphere for 2.4 hours at 1120K. At the same time, the density of the powder layer increased to a value of .02 0.89-0.92. The inner and outer surfaces of the reconstructed bushing were machined with an allowance of 2.8 0.18–0.22 mm. . The adhesive strength of the powder layer was 130-135. MPa. The coating had a thickness of h Lysis UMex.i 0.3+ (0.18 - 0.22) 0.48 - 0.52 mm. In the proposed method of repairing parts with an internal cavity, there is no need to use electrically conductive shells. Pressing the powder onto the outer surface of the part is carried out by its radial deformation (distribution) in the die cavity. In this case, the distribution is provided by the direct action (without shells) of the pulsed magnetic field of the internal inductor on it. The possibility of such a deformation due to the relatively high electrical conductivity of the metal parts. Thus, the restoration of the part according to the proposed method is carried out by successive reduction and distribution by pressing directly the part without the use of electrically conductive shells.

1

Claims (1)

METHOD FOR RESTORING DETAILS WITH INTERNAL CAVITY, which involves installing the part on a mandrel, magnetically pulsing a powder layer onto the outer surface of the part, sintering and machining, characterized in that in order to increase the efficiency of the process by eliminating non-ferrous metal shells, before magnetic by pulse pressing the powder layer, the part is crimped onto the mandrel and placed in the cavity of the matrix, and the pressing is carried out by distributing the part in the cavity of the matrix, while the radius ₽ _FROM p mandrels are selected from the condition ^ οπρ ⁼ ^ Η ' ^Δ Μβ * .4 ⁺ θ2 (θ · _ο ' θ ^ ·) ^ ⁴ em ⁺⁴ mech. < ^{+ 4} > and the radius R _{M of the} cavity of the matrix from the condition t ^r m * ^R onp ^{+ n} ' ⁴ and * n ^{+ 4 me} * · <* " -. ... * where R _M is the nominal internal radius of the part, * θ ,, © _а is the density of the powder in the state of filling, after pressing and sintering, respectively). ⁴ mechch ' ⁴ mechg ~ respectively - start, machining of the inner and outer surfaces of the part; Aiz ~ wear value) N - nominal thickness of the part.