RU1773620C - Method of restoring parts - Google Patents

Abstract

Usage: restoration of broken gear teeth. SUMMARY OF THE INVENTION: First, a mold based on a sand-resin mixture is made. As a model in the manufacture of molds, a solid gear tooth is used. The mold is made in the form of a sector covering two teeth more than the number of broken teeth located one after the other. The mold is based on the adjacent broken tooth m. The gear wheel is positioned horizontally and surfaced in the mold cavity at a voltage of ... 37 V at min current (13.5 + 0.438R-hT) / (0.065--0.0018R); where min is the minimum allowable value of the surfacing current (A); Bm - the required height of the surfacing (mm); R is the shortest distance from the place of burning of the arc to the wall of the mold (mm). In order to expand the range of weldable parts, the mold is made in height from separate sections, the height of each of which is a multiple of the height of the tooth and satisfies the condition: hc 13.5-0.051 + + 0.438R + 0.0018IR. As the cavity of each section is filled, the mold is expanded along the height of the tooth by installing another section. 1 ill. /)

Description

The invention relates to the field of mechanical engineering, and in particular, to methods for restoring gears of a predominantly medium and large module by surfacing. It can be used in automotive tractor, ship, machine repair production.

The known method 1 for restoring a gear rim of a wheel, in which a tooth is cut off and welding filler material is welded. The disadvantages of this method are:

-the need for a laborious operation of cutting teeth before welding the additives, which usually require preliminary tempering or annealing (due to high hardness);

-the need for machining the weldable additive;

- use to restore welding, which gives two zones of softening of the metal, due to thermal influence, one in the gear body and the second in the tooth body, which reduces its operational properties,

h h o

- difficulties associated with welding due to the inconvenient position of the seam;

- danger due to lack of penetration. The known method 2 surfacing parts

liquid metal, with heating the surface of the workpiece to be surfaced, including placing the workpiece in the mold, filling the gap between the mold and the workpiece with molten metal and subsequent cooling, characterized in that cuts are made in the zones of highest stresses. This method has disadvantages:

- the need to make a model for the production of molds,

-the need for molten metal in a separate heating equipment and pouring metal into a mold,

-the need for heating the deposited surface before pouring.

The closest in technical essence is the method 3 for the restoration of parts, a prototype, including the manufacture of a gasified model of the worn part of the part, its molding, pouring with molten metal and subsequent cooling, while a flux is applied to the worn surface of the part in a mixture with glue that burns out during pouring, and the gasified model is made and fixed on the part at the same time as filling the mold with the foamed suspension expanded polystyrene foam placed in the restored part. This method also has the disadvantages of:

-the need for the manufacture of molds and the availability of press equipment,

-the need to purge gas through the model and the availability of such equipment and accessories,

-the need to prepare a flux-glue mixture and apply it to a worn surface,

-the need for melt preparation in separate melting equipment.

The aim of the present invention is to reduce the complexity of restoring broken wheel teeth during submerged arc welding or in shielding gas environments.

The goal is achieved in the method of restoring the part, in which the mold is manufactured, fixed relative to the part and filled with molten metal, the mold is made on the basis of a sand-resin mixture, the whole gear tooth is used as a model for manufacturing the mold, and the mold is made in the form of a sector that covers K + 2 teeth of the wheel, where K is the number of broken teeth located one after the other, then set the gear in a horizontal plane and implement basing sector extreme cavities form two neighboring broken teeth, and surfacing in the mold cavity lead to the current: I | 13.5 + 0.438 R-NT

min 0.065 - 0.0018 R

at a voltage of IN26 ... 37 V, where min is the minimum allowable value of the surfacing current (A),

hr is the required surfacing height (mm), R is the shortest distance from the arc burning point to the mold wall (mm), in addition, in order to expand the range of restored gear wheels, a sector-shaped mold is made in height from separate sections, each of which is a multiple of height tooth height and satisfies the condition

hc 13.5 - 0.0651 + 0.438R + 0.0018IR; in this case, as the cavity of each section is filled, the mold is increased in height of the tooth by installing another section.

Figure 1 shows a part of a restored gear wheel 1 with whole teeth 2, between which a group of broken teeth is located. Shown is a form consisting of separate sections 3, electrode 4, substrate 5, vectors of feed rate of electrode V3

and surfacing speed VH.

The method is implemented as follows: the gear wheel 1 (Fig. 1) to be surfaced is cleaned, a group of K broken teeth is examined and the number of whole teeth n K + 2 required for manufacturing the mold covered by the sector is calculated.

A sand-resin mixture is prepared from refractories and pulverbakelite, the portion of wheel 1 with the required number of teeth is heated to 300 ° С, and the molding mixture is poured onto it, limiting the molding portion to a flask of easily deformable metal strip. Then, the mold 3 is removed, based on the group of broken teeth by the extreme cavities along the whole tooth m 2 adjacent to the broken ones, the shape is fixed by pressing against the gear wheel in the radial direction, set

assembly on a substrate 5 with a vertical axis of the gear 1 and surfacing is performed at a voltage of 26 ... 37 V, The deposition current is determined from the condition:

i «l - 13-5 + 0.438 R -hT

1min - 0.065-0.0018 R

After surfacing, the mold is removed and the teeth are machined. The gears are thermally or chemically heat treated to obtain the desired properties.

At milking, the tooth is larger than the maximum permissible electrode extension or at an unacceptably low value of the current that ensures shaping in order to expand the range of restored wheels, the mold is made in the form of separate sections 3 in height. First, the first section is based and fixed from the bottom, then surfacing is performed. When surfacing in shielding gas, the arc burning process is not interrupted, and as the first section is filled, another is installed, etc. When surfacing under flux, the arc is interrupted, the surfacing is cleaned of slag and flux, the second section is installed and the surfacing process is continued.

The invention is illustrated by the following example: a gear tooth was restored with a module of m 12 mm with the number of teeth z 100 in this method. The mold was made from a sand-resin mixture with the composition: 6% pulverbakelite (by weight)

1.5% kerosene

the rest is electrocorundum E-40.

A group of three teeth was heated in the flame of a gas burner to 300 ° C, having previously formed around them a flask of nickel strip 1.5 mm thick. A moldable mixture was poured onto warmed teeth. After 5 minutes, the mold was removed and cut into three sections 10 mm high each. The gear wheel was placed in a horizontal plane and fixed over the broken tooth the first section of the mold in the lower part of the tooth, based on its extreme cavities along the adjacent to the broken tooth m. A plate of a polymerized mixture of the same composition as the mold was used as a substrate. The NP-40X2G2M electrode with a diameter of 2.0 mm was directed to the workpiece in its lower part along the axis of the tooth. The shortest distance from the place of burning of the arc to the mold wall was R 5 mm, the maximum deposition height in one section was Lt 10 mm. Surfacing current value:

I (13.5 + 0.438 5-10) 7 (0.065-0.0018 5) -100 A. The electrode feed rate V0 of 87.7 m / h was assigned to the current for the electrode at a voltage of U 26 V. Surfacing was carried out in a carbon dioxide medium until the tooth cavity of the section was completely filled, then, without interrupting the surfacing, the shape was increased due to the remaining sections until the tooth was completely restored. After restoration, the tooth was machined with a 1.2 mm allowance. The gear wheel was put into operation.

The proposed method reduces the complexity of restoring broken gear teeth.

Claims (2)

1. The method of restoring parts in which the mold is made is fixed it relative to the part and is filled with molten metal, characterized in that, in order to reduce the complexity of the restoration of broken gear teeth during electric arc surfacing under using flux or in the environment of shielding gases, the mold is made on the basis of a sand-resin mixture, the whole gear tooth is used as a model for making the mold, and the mold is made in in the form of a sector that covers K + 2 teeth of the wheel where K is the number of broken teeth located one after the other, then the gear is installed in a horizontal plane and basing sectors with the extreme cavities of the mold along two adjacent to the broken teeth, and surfacing into the mold cavity is carried out at a current calculated by the formula 13.5 + 0.438 R -hT 1min - - 0.065-0.0018 R where 1Min is the minimum allowable value of the surfacing current, A; hr — required surfacing height, mm; R is the shortest distance from the place of burning of the arc to the mold wall, mm; at a voltage of 26-37 V. 2. The method according to claim 1, characterized in that, in order to expand the range restored gears, the shape in the form of a sector is made in height from separate sections, the height of each of which is a multiple of the height of the tooth and satisfies the condition hc 13.5 -0.065I + 0.438R + 0.0018IR, in this case, as the cavity of each section is filled, the shape is increased in height of the tooth by installing another section. /