RU2236335C2 - Method for restoring wells of aluminum-alloy housings of gear pumps - Google Patents

Abstract

FIELD: restoration of worn parts of aluminum alloys, for example restoring and strengthening wells of housings of gear pumps.

SUBSTANCE: method of restoring wells of gear pump housings of aluminum alloys comprises steps of building-up restored wells by reducing them at heating up to temperature 510 C; terminating reduction at temperature no less than 440 C; performing micro-arc oxidizing in electrolyte containing 8 g/l of melt glass at electric current density 25 A/sq.dm for time period of oxidizing equal to 1.5 h.

EFFECT: lowered intensity of wear, enhanced wear resistance of wells of gear pump housings, improved efficiency of restoration of wells due to shortened time period of strengthening them.

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Description

The invention relates to the field of recovery of worn parts from aluminum alloys, for example, for restoration with hardening of wells of gear pump housings of the NSh or NSh-U type.

In the repair industry, a known method for restoring worn surfaces of parts is that the worn surface is deformed by rolling with rollers - electrodes with simultaneous electric heating, which is carried out by current pulses of 3 ... 6 kA with a pulse duration of 0.02 ... 0.06 s and the duration of the pauses of 0.2 ... 0.04 s, while the rolling speed is taken equal to 0.2 ... 1.0 m / min [1].

However, this method does not allow to restore the wells of gear pump housings of the NSh or NSh-U type, since it is not possible to introduce rollers into them - electrodes that deform worn surfaces.

A known method of restoring wells of gear pump housings of the NSh or NSh-U type, including compression, subsequent hardening of the restored housing (quenching in water and tempering for 5 hours) and their boring to the nominal or nearest repair size [2].

The wells of gear pump housings, restored by this method, have low wear resistance.

Closest to the proposed method in terms of technical nature and the achieved result is a method of restoring worn parts from aluminum and its alloys, including increment (surfacing in a protective gas environment), boring of the restored surface to a certain size, taking into account their increase during microarc oxidation and hardening by microarc oxidation in an alkaline electrolyte containing caustic potassium 1 g / l and water glass 6 g / l at a current density of 15 A / dm ² [3].

However, when this method is restored by wells of gear pump housings, the thickness of the coating formed on them by microarc oxidation is only 70 ... 90 μm, which leads to low durability of the restored pump as a whole.

The objective of the invention is to increase the thickness of the coating formed on the restored wells of the housing of gear pumps of the NSh or NSh-U type, the durability of the restored parts, and also to increase the productivity of the restoration of the wells of the housings by reducing the duration of their hardening.

The problem is achieved in that in the known method of recovering worn parts from aluminum and its alloys, including increment, boring of the restored surface to a certain size, taking into account their increase during microarc oxidation and hardening by microarc oxidation in an alkaline electrolyte containing 1 g / l potassium hydroxide and water glass, according to the invention, the increment of the restored wells of the body is carried out by compression with heating to a temperature of 510 ° C and the completion of compression at a temperature Ur not lower than 440 ° C, and microarc oxidation is carried out in an electrolyte with a content of 8 g / l of sodium silicate at a current density of 25 A / dm ² and duration of oxidation 1.5 hours.

The method is as follows.

The restoration of worn wells of the gear pump housing of the NSh or NSh-U type includes its mechanical treatment until the wear traces on the twin-spindle boring machine of type 2705 are removed. After the machining, the gear pump housing is loaded into the furnace, heated to a temperature of 510 ° C, maintained for 30 ... 35 min and crimped in a special mold for a period of 10 ... 15 s. For this, the pump housing is installed in the matrix block with the upper position of the press slider. When the slider moves down, the punch is inserted into the pump casing, and when the upper plate is pressed on the matrix block, they move down the inner conical surface of the mold casing and compress the pump casing. When the slider moves up, the punch is removed from the pump housing. The ejector pushes the matrix block out of the mold body together with the compressed pump housing. The compression is completed at a temperature not lower than 440 ° C, otherwise the ductility of the alloy decreases sharply.

After crimping, the wells of the gear pump housing are bored to the nominal or nearest repair size with allowance for microarc oxidation. Draft boring modes: tool rotation speed - 950 min ^-1 , cutting depth - 0.3 ... 0.4 mm, feed - 0.6 mm / min. Finishing boring modes: tool rotation speed - 1500 min ^-1 , cutting depth - 0.1 mm, feed - 0.25 mm / min.

Then hardened wells of the gear pump housing are hardened by microarc oxidation in an alkaline electrolyte of the following composition: caustic potassium - 1 g / l, liquid glass - 8 g / l. Processing modes: current density - 25 A / dm ² , electrolyte temperature - 18 ... 23 ° C, oxidation time - 1.5 hours. The thickness of the coating formed by microarc oxidation on the restored wells of the casing is 100 ... 120 microns.

The durability of the restored wells of gear pump housings was evaluated according to the results of comparative accelerated tests at the stand KI-4815M-03, which is intended for testing hydraulic drive units of agricultural machinery. The tests were carried out in accordance with the recommendations of the guidance document RD 70.0009.006-85 “Instructions on the methods of accelerated testing of reconditioned parts for the main brands of tractors, combines and other machines” developed by VNPO “Remdetal”.

The results of comparative tests of the proposed method and prototype are presented in the table.

As can be seen from the table, the proposed method for the restoration of wells of gear cases of gear pumps made of aluminum alloys makes it possible to increase, on average, 1.4 ... 1.5 times the thickness of the coating formed on them by microarc oxidation, as a result of which the durability of the restored parts increases by 1.6 times. At the same time, the hardening time decreases by 25%, which leads to an increase in the productivity of restoration of wells of gear pump housings of the NSh or NSh-U type.

Sources of information

1. A.S. 1004062, B 23 P 6/02, publ. in BI No. 10, 1983.

2. Prince Reliability and machine repair, ed. Kurchatkina V.V. - M .: Kolos, 2000 .-- 776 p., S. 409 ... 410.

3. RF patent 2119420, 23 P 6/00, publ. in BI No. 27, 1998 - a prototype.

Claims (1)

A method of restoring well wells of gear pumps made of aluminum alloys, including incrementing, boring of restored wells of a housing to a certain size, taking into account their increase during microarc oxidation and hardening by microarc oxidation in an alkaline electrolyte containing 1 g / l caustic potassium and liquid glass, characterized in that the increment of the restored wells of the shells is carried out by compression with heating to a temperature of 510 ° C and the completion of compression at a temperature not lower than 440 ° C, and microarc oxidation is carried out in an electrolyte containing 8 g / l of liquid glass at a current density of 25 A / dm ² and a duration of oxidation of 1.5 hours