RU2284241C1 - Method for knurling toothed profiles on sintered bimetallic blanks - Google Patents

Abstract

FIELD: systems for rotation plastic working of materials, namely manufacture of gear wheels with internal gearing from sintered bimetallic powder materials.

SUBSTANCE: method comprises steps of knurling toothed profile on sintered bimetallic annular blank made by simultaneously forming working layer and base and sintering blank. Said blank includes base and internal working layer with thickness t = (4.0 - 8.0 )m. Toothed profile is knurled by means of teeth knurling rollers after sintering blank at preliminarily compacting working layer by value h of technological allowance in teeth apexes h = (0.25 -1.25)m where m - gearing modulus.

EFFECT: enhanced efficiency of method, rational consumption of deficient materials.

6 dwg, 1 ex

Description

The invention relates to the field of rotational processing of materials by pressure, specifically to the manufacture of gears with internal gearing from sintered bimetallic powder materials by rolling with gear rolling rollers.

A known method of manufacturing profiled annular products, including the rolling of the toothed profile with appropriate knurls on the inner surface of the annular blank (SU 929290, 21 N 5/02). This method is used for rolling a toothed profile on blanks of compact material, but it is not effective when rolling a profile on powder sintered blanks, because its implementation does not take into account the porous structure of the initial blank and the compaction of the porous material when it is deformed. The latter leads to a significant heterogeneity of the compacted material at the apex and in the cavity of the tooth, and therefore to its insufficient strength.

A known method of rolling gear profiles on bimetallic workpieces and a device for its implementation (SU 1235604 A1, 21 N 5/00), adopted as a prototype. Distinctive features of the prototype are the preliminary profiling of the gear profile in the form of a rack, which is carried out by the knurler while heating the rack, and the subsequent connection of the tooth profile with the wheel rim by rolling in a closed caliber with preliminary application of flux to the wheel rim.

The specified method involves the preliminary profiling of the toothed profile in a separate device and the final molding in another device - a closed caliber, which requires synchronization of their joint work and compensation of possible errors in steps. The connection of the gear profile (rail) with the base (wheel rim) is carried out using several operations - applying flux, heating, deformation in a closed gauge, and therefore, additional control over the modes and parameters of each previous operation is required in order to guarantee the performance of the parameters of the subsequent operation (for example , the thickness of the flux can affect the size of the joint gap between the beginning and the end of the rail when they are connected). In some cases, the connection using flux does not guarantee sufficient mechanical strength of the connection of the layer and the base in the zone of their contact.

In addition, in the manufacture of gear profiles on bimetallic sintered blanks, this method does not allow the rolling process to be carried out efficiently, because it does not take into account the size of the working layer of the workpiece, the penetration depth of deformation when rolling in different zones of the tooth, and the interaction of materials of the working layer and the base during their joint deformation. In aggregate, this can lead either to cracks in the zones of intense tensile stresses or to the detachment of the working layer from the base.

Thus, when deforming bimetallic sintered billets, an important condition is the selection of the optimal combination of process factors such as the initial thickness of the working layer of the workpiece and the amount of compaction of the working layer in the zone of tensile stresses, due to the corresponding value of the technological allowance for rolling.

The objective of the invention is to provide an effective method for rolling tooth profiles on bimetallic sintered annular blanks, which ensures the saving of scarce materials of the working layer due to the rational choice of its initial thickness and high density and strength of the tooth profile by the optimal choice of technological allowance for compaction and shaping of the tooth profile.

The problem is solved as follows: the serrated profile is rolled on a bimetallic sintered annular billet consisting of a base and an inner working layer of thickness t = (4.0-8.0) m, which is obtained by simultaneously forming the working layer and the base and sintering, and rolling the gear profile is produced by gear rolling rollers after sintering the workpiece with preliminary compaction of the working layer by the size of the technological allowance at the tops of the teeth h = (0.25-1.25) m, where m is the engagement module.

The invention is illustrated graphic materials.

Figure 1 is a sketch of a sintered bimetallic ring billet before and after rolling a toothed profile consisting of a working inner layer (material is a powder with the desired properties, for example, bronze powder) and an outer base (ordinary, for example, iron powder). On the left side of the drawing, the workpiece is shown after pressing and sintering, on the right side of the drawing, after rolling the toothed profile.

Figure 2 - schematic diagram of the process of rolling gear profiles on bimetallic sintered blanks by gear rolling rollers;

FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are the results of a macrostructural analysis of the rolled profile for various parameters of the initial billet and various modes of compaction of the technological allowance (examples of the method).

In figures 1 and 2 presents a sketch of a bimetallic billet and a diagram of the device, revealing the work of the proposed method, where 1 is a bimetallic ring billet, 2 is a matrix, 3 is a reference gear, 4 is a clip, 5 is a knurling, 6 is a clip.

The inventive method is as follows. The metal preform is pressed, for example, in a rigid matrix, so that the initial thickness of the working layer before rolling is t = Rk-Rp = (4.0-8.0) m, where Rk is the radius of the contact zone of the working layer and the base; Rp is the inner radius of the workpiece. The process of rolling the toothed profile on the working layer of the workpiece, including pre-compaction of the working layer and the subsequent shaping of the toothed profile with the help of knurls is illustrated by the diagram depicted in figure 2. The sintered bimetallic ring billet 1 is placed in the matrix 2 coaxially with the reference gear 3 and secured with a clamp 4. The knurls 5, mounted rotatably in the yoke 6, are engaged with the reference gear 3, rotated and simultaneously moved with a predetermined axial force . As the axial movement of the knurls, the technological stock h is sequentially compacted with the input part of the knurl L1 and the teeth are actually rolled using the forming section L2. At the end of the tooth rolling process, the holder 6 with the knurls 5 returns to its original position, and the finished part is removed from the matrix 2. The density of the knurled teeth on the porous sintered workpiece depends on many factors, among which the technological allowance is a parameter that allows controlling the compaction process within certain limits. First of all, the technological allowance should provide the required compaction and shaping of the tooth apex, i.e. its value should be h = Rb-Rp, where Rb is the radius of the tooth apex. With the used initial relative density of the sintered material 0.75-0.85, we can recommend the value of the technological allowance h = (0.25-1.25) m, which, as follows from the experimental data, is optimal. Moreover, the maximum compaction of the sintered material in the zone of the tooth cavity allows you to achieve a density of 0.96-0.98. The density of the sintered material in the area of the tooth apex will be about 0.92-0.94. Thus, a rational choice of the thickness of the working layer and the size of the technological allowance allow to save the special material of the working layer and to obtain products with serrated profiles of high density and strength.

An example implementation of the method

The proposed method was implemented in the manufacture of bimetallic gears with internal gearing with the following parameters:

- material of the working layer - bronze powder DO5N5;

- base material - iron powder ANS.100.29;

- engagement modulus m = 1.5 mm;

- number of teeth - 76;

- the diameter of the tips of the teeth - 2Rv = 111 mm;

- diameter of tooth cavities - 2Rvp = 117 mm;

- the thickness of the working layer of the workpiece t = 5-15 mm;

- technological allowance h = 0.2-2.0 mm;

The initial thickness of the working layer was varied by pressing it with an eccentricity of 5 mm relative to the center of the base. As a result, blanks with a variable thickness of the working layer were obtained. To obtain different values of the technological allowance, the workpiece 1 was installed in the matrix 2 with a given eccentricity relative to the reference gear. As a result of testing the proposed method and studying the obtained gears by measuring the relative density and analysis of the macrostructure in the characteristic zones of the samples, the following results were obtained:

- when rolling with significant technological allowances of more than 1.25m defects appear at the base of the tooth (Fig. 3), since as a result of over-compaction of the material of the working layer and its extrusion, significant deformations of its tension arise;

- when rolling with a minimum technological allowance of less than 0.25 m, cracks are observed on the tops of the teeth (Fig. 4), since uncompressed porous material does not withstand the tensile stresses arising in this zone;

- when the thickness of the working layer is less than 4.0 m, defects in the interface between the working layer and the substrate are observed in the form of cracks and delaminations (Fig. 5). Defects are caused by significant shear deformations at the interface;

- when the thickness of the working layer is more than 8.0 m, no defects are observed, but the cost of the product increases sharply and the use of bimetallic sintered materials becomes ineffective;

- in the zone of thicknesses of the working layer from 4.0m to 8.0m during knurling with technological allowances from 0.25m to 1.25m, teeth with a good quality of the outer surface, with a fibrous grain structure in the contact areas, without defects and cracks were obtained the volume of the working layer of the product (Fig.6). The density of the material at the peaks was 0.92-0.94, and the density of the troughs was 0.96-0.98.

Optimization of the thickness of the working layer of the bimetallic billet depending on the rolling gear mesh module ensures the saving of the special material of the working layer and the production of teeth with high operational characteristics, and the rational choice of the technological allowance allows achieving sufficient density in the material of the tooth apex and the maximum required density in the material of the depressions, which expands on the whole the technological capabilities of the process of rolling gear and splined profiles on special bimetallic powder blanks.

Claims (1)

A method of rolling tooth profiles on sintered bimetallic billets, characterized in that the tooth profile is rolled on a bimetallic sintered annular billet consisting of a base and an inner working layer of thickness t = (4.0-8.0) m, which is obtained by simultaneously forming the working layer and warp and sintering, and the rolling of the tooth profile is carried out by gear rolling rollers after sintering the workpiece with preliminary compaction of the working layer by the amount of technological allowance at the tops of the teeth h = (0.25-1.25) m, where m - The module links.

Images