RU2206439C2 - Method for restoring mounting surfaces of parts for bearing assemblies - Google Patents

Abstract

FIELD: restoration of supporting runners of tractors, rollers of rotary excavators and other large size articles having inner openings for mounting seat of bearing assemblies. SUBSTANCE: method comprises steps of preliminarily working surface of restored part; making embedding member in the form of shell with linear expansion factor (11.0 - 1.7)•10^-6 and with thickness 10 - 12 mm; applying on surface of shell wear resistant material with thickness 2.0 - 2.5 mm by induction surfacing at temperature 1200C and equalizing temperature of shell along its contour to 800 C; realizing further mounting of shell by shrink fit; then performing electric arc flux welding of shell on surface of part on its ends. EFFECT: enhanced quality of geometry size of worn parts, increased useful life period of restored parts. 4 dwg, 1 ex

Description

 The present invention relates to mechanical engineering, in particular to methods for the restoration of supporting rollers of tractors, rollers of rotary excavators and other products weighing from 30-300 kg, having internal holes for seats of bearing assemblies operating under high contact loads.

 A known method of protection and restoration of bulky products by surfacing (see US Pat. RU 2124975, class. 23 P 6/00, 23 K 9/04, 1999, B. 2) [1], which consists in the fact that worn the surfaces of the product are prepared for embedded elements by machine tool machining, and the elements themselves are made in accordance with the predicted wear values in the form of flat inserts with a thickness of at least 4-5 mm, various configurations depending on the design dimensions of the mates operating under friction forces they are made of low alloy steels, moreover, the said inserts on the side of the movable contacts are surfaced with a wear-resistant coating of 1-2 mm with a hardness of 320-400 HB, while the inner surface of the inserts is welded to the product.

 However, the disadvantage of this method is that it is not possible to use cracks in the coatings of such inserts to use flat embedded elements with a thickness of 4-5 mm to restore the cylindrical surfaces of rollers, rollers or other similar products having seats for bearing assemblies , since such materials are not intended for tensile work, which does not allow high-quality recovery of products.

 In addition, to maintain the geometric dimensions of the seats in the known method is also difficult due to the fact that the metal of the roller itself cannot be overheated, which will cause its softening, and, accordingly, will lose hardness, which is unacceptable.

 A known method of hardening rollers of rotary excavators (see the book "Fundamentals of alloying deposited metal", L. S. Livshits, "Engineering", M., 1969, S. 171-172) [2], which consists in the fact that worn racetracks rotor rollers were surfaced with flux-cored wire of different grades with a thickness of 4-6 mm by electric arc welding, and then ground to size.

 The disadvantage of the analogue is that surfacing directly on the roller with a thick layer of metal leads to heating of the entire roller and changes the geometry of the bearing seats, which requires additional laborious and expensive boring operations, not ensuring high quality restoration of such products.

 The closest in technical essence to the claimed is a method of restoring a worn part, including preliminary machining of the working surface of the restored parts, installation of a embedded element on it, its welding and subsequent machining (IPC V 23 P 6/04 patent RU 2062204 C1, 06/20/1996 ) [3], taken as a prototype.

 The disadvantage of the prototype is the low wear resistance of the restored surface of the part due to the welding of the embedded element to the restored part without hardening it with a wear-resistant material.

 The technical result of the invention is to improve the quality of restoration of the seating surfaces of parts for bearings in the conditions of repair production.

The technical result is achieved by the fact that in the known method of restoring the seating surfaces of parts for bearings, including pre-machining the working surface of the part being restored, installing the embedded element on it, welding it and subsequent machining, according to the invention, the embedded element is made in the form of a shell having a linear coefficient expansion (11,0-12,7) • 10 ^-6, 10-12 mm thick, is applied to the mantle surface of wear-resistant material of thickness 2.0-2.5 mm on induction bench at 1200 ^o C and the temperature of the sleeve is aligned over the contour to 800 ^o C, the subsequent installation of the fitting member produced by shrink-fit, and then produce submerged arc welding the sleeve to the workpiece surface by its ends.

The essence of the invention is illustrated by the drawing, which shows the technological sequence of restoration of the seating surfaces of parts for bearings on the example of a tractor track roller, where
a) supporting roller to be restored;
b) preparing the rink for recovery includes
- groove of treadmills;
- chamfering;
c) the manufacture of the embedded element in the form of a shell includes
- cutting two workpieces and bending them;
- welding with cutting edges;
- groove of shells on the inner and outer surfaces;
- chamfering from two sides;
- surfacing of shells on the outer surface;
- equalization of the temperature of the shells up to 800 ^o C;
g) hardening of the roller
- landing shells on the rink;
- butt welding;
- grinding.

 The method is carried out according to the following technology.

Selected after the development of the rollers 1 (see drawing, a), the wear of which does not exceed 10-12 mm per side, is subjected to machining. To do this, the running or working surfaces of the roller are machined on a lathe, removing the worn layer to a diameter (D ₀ ^+0.1 ) (see drawing, b).

Then make embedded elements, which are performed in the form of shells 2 (see drawing, c). Each shell is cut from a sheet 10-12 mm thick in accordance with the wear and geometrical dimensions of the working surfaces of the roller, bent on rollers, followed by welding along the ends with cutting edges. In this case, the inner diameter of the shell D _about should be 3 mm less than D ₀ roller.

After that, on the lathe, a casing is machined both from the inner side under the bore diameter D ₀ ^-0.1 , and from the outer cylindrical surface for surfacing with a wear-resistant alloy. At the same time, a chamfer for welding is performed. Depending on the geometry of the skating rink, it can be single-flange or double-flange, and there can be one or two embedded elements, therefore, chamfers for welding are provided in each case separately. The wear-resistant alloy is dosed on the surface "A" of the shell 2 with a thickness of 2-2.5 mm and melted in the inductor field, while smoothly turning it from the drive. Thus, they produce a surfacing of each shell for two minutes along the entire cylindrical surface "A" at a temperature of 1200 ^o C.

Thus, having prepared the embedded elements (shells) for subsequent technological operations, they equalize their temperatures along the circuit within 800 ^o C. Bearing in mind this condition, embedded elements, if necessary, are either cooled or heated. After that, they are mounted on the restored surface of the roller (see drawing, g). Due to the fact that shells with a linear expansion coefficient γ = 11.0-12.7 • 10 ^-6 are hot-seated, when cooling, they tightly compress the working surface of the roller without causing large heat input to the metal of the roller itself, which ensures the preservation of the geometry of the landing places for bearing units.

 To eliminate the weakening of the landing of the shells and their rotation during operation, the latter are welded at the ends to the roller by submerged arc welding with an annular seam, and then smooth out irregularities with a grinder.

 Example.

 The roller supporting the Fiat-Fiat Hitachi tractor was subject to restoration.

Initial data
material of a roller - steel 45, HRC 45;
diameter of roller treadmills, D _damn. - 185 mm;
diameter of worn roller treadmills, D - 166 mm.

To restore the geometrical dimensions of the supporting roller (see drawing, a), which has seats for the bearing units, a groove was made on the lathe of the worn working surfaces of the roller to a diameter of 165 ^+0.1 mm and a 5 mm bevel was taken at an angle of 45 ^o from the outside each shell.

Then, two blanks with dimensions of 12x583x53 were cut from sheet steel 40 with a thickness of 12 mm. Two shells were bent on rollers from these blanks, each with an outer diameter of 186 mm and an inner 162 mm. The shells were welded at the ends with cutting edges (see drawing, c) and each was machined on a lathe with an outer diameter of up to 182.5 mm, and an inner diameter of up to 165 ^-0.1 mm.

By means of the inductor of the VChG9 60 / 0.44 installation, each shell was surfaced with the wear-resistant PG-USCH-35 alloy on the outer surface with a layer of 2-2.5 mm. Surfacing was performed within two minutes on one shell at a temperature of 1200 ^o C. As a result, the outer diameter of the shell was 185 ^+0.5 mm, with a clean surface that does not require grinding. Chamfers at the ends of the shells of 5 mm were removed at an angle of 45 ^o on one side and in hot form, since the temperature along the contour of the shells was 800 ^o C, and they were put on the working surfaces of the roller (see drawing, d). During cooling, the shells decreased in diameter and tightly pressed the working surfaces of the roller. After that, shells were welded along the ends of the roller by submerged arc welding and the irregularities were cleaned with a manual grinder.

 The proposed method allows to restore products such as rollers, rollers having seats under the bearing assemblies through the use of embedded elements made in the form of shells, fused separately from the restored product by wear-resistant alloys and hot-seated, using the crimping of the embedded element directly mounted on the product, which makes it possible to qualitatively restore the geometrical dimensions of worn-out products, maintain the landing dimensions for bearing assemblies and at the same time increase to increase the durability of the product, increasing their service life by 1.5-2 times.

Claims (1)

A method of restoring the seating surfaces of parts for bearings, including pre-machining the working surface of the restored part, installing a embedded element on it, welding it and subsequent machining, characterized in that the embedded element is made in the form of a shell having a linear expansion coefficient (11.0- 12.7) • 10 ^-6 , 10-12 mm thick, apply wear-resistant material with a thickness of 2.0-2.5 mm by induction surfacing at 1200 ^o С on the shell surface and equalize the shell temperature to a contour of up to 800 ^o C, while the subsequent installation of the embedded element is carried out by hot landing, and then electric arc welding is performed under the flux of the shell to the surface of the part at its ends.

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