RU2500517C2 - Method of cylindrical part plastic forming - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to plastic forming of cylindrical parts. Roller is fed and oscillated along machined part axis by liner step drive relative to the plane perpendicular to part axis. Roller is reciprocated in direction parallel with that of said step liner drive. Roller oscillation amplitude A and frequency f are defined by formula: A=10^-3S_m(1-K_HV), mm, $$f=\frac{n_{\partial }}{60}\cdot K_{HV},\text{ Hz}$$

, Hz; roller reciprocation amount L is taken equal to L=(1.5-2.0)A, mm, where S_m is preset pitch of regular micro relief of part surface, mcm; K_Hv is the factor defined by part material micro hardness-to-roller material hardness; n_p is part rpm, rpm.

EFFECT: higher fatigue strength and surface wear resistance.

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Description

The invention relates to the field of mechanical processing of materials, namely to hardening surfaces by the method of surface plastic deformation giving it special properties and can be used in various branches of engineering.

A known method of processing cylindrical parts (see copyright certificate No. 1263510, B24B 39/04, bull. No. 38, 1986), in which the surface is applied relief in the form of periodic annular grooves along the axis of the part by radial movement of the deforming tool, which is additionally reported oscillatory movement in a direction perpendicular to its reciprocating movement along the axis, while the frequency of the reciprocating movement is chosen to be 0.0005-0.025 of the frequency of the oscillatory movement of the deforming tool deforming tool.

Signs that coincide - carry out surface plastic deformation of a cylindrical part with a deforming tool, which is additionally informed of an oscillatory movement along the axis of the part.

Reasons that impede the task - there is no way to form a regular microrelief on the surface of the part in the form of intersecting waves of a given amplitude and pitch, as well as their changes during operation.

A known method of processing cylindrical parts (see copyright certificate No. 1353596, B24B 39/04, bull. No. 43, 1987), in which carry out surface plastic deformation of a rotating part with a conical roller with constant radial force when informing him of the feed movement along the axis of the part at the same time, due to the provision of the specified orientation of the physicomechanical and geometric properties of the surface layer of the part, plastic deformation is carried out with a variable specific pressure, and the conical roller is set to perpendicular to the axis of the workpiece and give him an additional feed motion perpendicular to its main movement and tangent to the work surface.

The signs are the same - carry out surface plastic deformation of the rotating part by a roller with constant radial force when it is informed of the feed movement along the axis of the part, and the conical roller is set perpendicular to the axis of the workpiece and informs it of the additional feed motion.

Signs that impede the task - there is no way to form a regular microrelief in the form of intersecting waves of a given amplitude and its changes during operation.

The prototype adopted a known method of processing cylindrical parts (see RF patent No. 2221686, MKI B24B 39/00, 39/04, bull. No. 2, 2002), which carry out surface plastic deformation of a rotating part by a roller with constant radial force when communicating feed movements along the axis of the part are given to it, while the roller is given oscillatory movements by means of a linear step drive relative to a plane perpendicular to the axis of the workpiece, and additionally carry out the possibility of reciprocating movements phenomena parallel to its core.

Signs of coincidence - carry out surface plastic deformation of the rotating part by a roller with constant radial force when it is informed of the feed motion along the part axis and oscillatory movements by means of a linear step drive relative to a plane perpendicular to the axis of the workpiece, and additionally carry out the possibility of reciprocating movements parallel to it to the main one.

Signs that impede the task - the hardness of the materials of the workpiece and the rolling roller is not taken into account.

The objective of the present invention is the ability to form a regular microrelief on the surface depending on the hardness of the materials of the workpiece and the deforming roller, which allows to increase its fatigue strength and resistance to surface abrasion.

To achieve a technical result in a method for processing cylindrical parts, in which surface plastic deformation is carried out by a roller with constant radial force when it is informed of a feed motion along the axis of the part and oscillatory movements by means of a linear step drive relative to a plane perpendicular to the axis of the workpiece, and additionally carry out the ability to make a return - translational displacements, amplitude A and frequency f of the oscillatory movements of the roller are determined by mules

A = 10 ^-3 S _m (1-K _HV ), mm;

, $$f=\frac{n_d}{60}\cdot K_{HV},\text{Hz}$$

,

and the value of the reciprocating movement of the roller L is taken equal to L = (1.5-2.0) A, mm, where S _m is the step of the regular microrelief on the workpiece surface, microns; K _HV - coefficient determined by the ratio of the hardness of the processed material of the part NUD to the hardness of the material of the deforming roller HV _P ; n _d - the frequency of rotation of the workpiece, rpm

The processing method consists in applying a regular microrelief to the surface of the rotating part by surface plastic deformation when the feed motion along the part axis is communicated to it. In this case, the deforming roller is kinematically connected with a linear linear stepping drive, from which it receives oscillatory movements with respect to a plane perpendicular to the component axis, the amplitude A and frequency f of which are previously determined by the formulas

A = 10 ^-3 S _m (1-K _HV ), mm;

, $$f=\frac{n_d}{60}\cdot K_{HV},\text{Hz}$$

,

where S _m - step regular microrelief on the workpiece surface, microns; K _HV is a coefficient determined by the ratio of the hardness of the workpiece material HV _D to the hardness of the material of the deformation roller HV _P ; n _d - the frequency of rotation of the workpiece, rpm

At the same time, the roller additionally has the ability to make reciprocating movements in the direction of the action of the linear stepper drive, i.e. parallel to the main movement. The value of the additional reciprocating movement of the roller is taken equal to L = (1.5-2.0) A. As a result, when a regular microrelief is applied to the surface of the workpiece, the hardness of the material of the part and the deforming roller is taken into account, and a regular microrelief is formed on the surface in the form of intersecting waves of variable density in amplitude and step, varying in the range depending on the hardness of the materials of the workpiece and roller. This allows you to increase the fatigue strength and resistance to surface abrasion of the workpiece both due to the applied controlled regular microrelief, and the creation of a directional texture of the material of the surface layer. The regular microrelief obtained on the surface of the part, the parameters of which depend on the hardness of the materials of the workpiece and the deforming roller, can be changed during the processing of the part and allows you to create "oil pockets" that further contribute to increasing the service life of the part.

As one of the devices through which the proposed method for processing cylindrical parts can be implemented, there can be a known device for hardening the rolling of parts by surface plastic deformation, comprising a housing, a linear stepping drive, a control unit in the form of a signal generator and a deformation roller kinematically connected with stepper linear drive. In this case, the device is equipped with a spherical hinge, an axis, elastic elements and an earring. In the case of the device, guide grooves are made into which the earring is mounted. The kinematic connection of the deforming roller with a linear linear stepping drive is carried out using the specified earrings. The deformation roller is mounted between two elastic elements with the possibility of oscillatory movement relative to the plane perpendicular to the axis of the workpiece, with periodic displacement of the contact zone and mounted on a spherical hinge mounted on the axis with the possibility of reciprocating movement in the direction parallel to the action of the step drive due to the elastic elements . The amplitude A and the frequency f of the oscillatory movements of the deforming roller relative to the plane perpendicular to the axis of the workpiece are set by changing the stiffness of the elastic elements of the device depending on the hardness of the materials of the workpiece and the deforming roller using the formulas

A = 10 ^-3 S _m (1-K _HV ), mm;

, $$f=\frac{n_d}{60}\cdot K_{HV},\text{Hz}$$

,

and the value of the reciprocating movement of the roller L in the direction parallel to the action of the stepper drive is set equal to L = (1.5-2.0) A, where S _m is the regular microrelief step on the workpiece surface, microns; K _HV is a coefficient determined by the ratio of the hardness of the workpiece material HV _D to the hardness of the material of the deformation roller HV _P ; n _d - the frequency of rotation of the workpiece, rpm

Comparative tests of the proposed method for processing cylindrical parts and the prototype (see RF patent No. 2221686, MKI B24B 39/00, 39/04, bull. No. 2, 2002). Hardening treatment was carried out on cylindrical rollers with a diameter of 32 mm and a length of 250 mm, made of steel 12Kh3N, 20KHN2MA and 50KHN. Previously, the rollers were subjected to grinding on a circular grinding machine mod. 3A150, as a result of which had the following average microhardness of the material of the surface layer: steel 12X3H - HV _D = 280 kgf / mm ² ; steel 20XH2MA - HV _D = 300 kgf / mm ² ; steel 50XH - HV _D = 330 kgf / mm ² . The regular microrelief pitch of the treated surface was taken equal to S _m = 50 μm. Rollers were rolled in on a screw-cutting machine mod 1A620 using a known device for hardening rolling parts by surface plastic deformation. The deformation roller with a diameter of 48 mm and a radius of the working profile of 16 mm was made of hardened high-speed steel P6M5 and had a microhardness of the surface layer of the working profile HV _P = 480 kgf / mm ² . Accepted processing modes (break-in force P, H; longitudinal feed of the deforming roller S, mm / rev; rotational speed of the workpiece n _d , rpm) and parameters of the additional movement of the deforming roller (A, mm; f Hz; L, mm) are given in table 1.

Table 1 Modes of processing rollers and parameters of oscillatory movements and additional movement of the deforming roller Roller Material Processing Modes Movie options P, N S, mm / rev n _D , rpm A mm f Hz L mm 12X3H 500 0.15 200 0,025 2 0.04 20XH2MA 600 0.15 160 0,020 2 0,03 50XN 800 0.1 125 0.015 1,5 0,03

Fatigue strength tests of the machined rollers were carried out in a facility for testing materials for fatigue strength (see V. Butenko, “Structure and properties of materials under extreme operating conditions.” - Taganrog: Publishing House of the Technological Institute of Southern Federal University, 2007. P. 157)), and on the resistance to surface abrasion - on the installation for testing materials for wear (see Butenko VI "Scientific basis of nanotribology." - Taganrog: Publishing House of TTI SFU, 2010. P.20). During the tests, the following operational indicators were determined for the treated surface of the rollers: wear rate I, mg / h; the maximum allowable stress in the cross section of the rollers tested for fatigue strength is σ _-1 , MPa, with the specified number of loading cycles N _c = 10 ⁴ cycles. The test results are shown in table.2.

table 2 The results of comparative tests of the proposed method for processing cylindrical parts and prototype Roller Material Prototype The proposed method I, mg / h σ _-1 , MPa I, mg / h σ _-1 , MPa 12XH3A 12.5 38 6.7 56 20XH2MA 10.3 41 5.2 64 50XN 8.6 57 4,5 89

Analysis of the test results presented in Table 2 allows us to conclude that the application of the proposed method for processing cylindrical parts provides almost a 2-fold increase in the resistance of the material of the surface layer of the parts and increases their fatigue strength by 40-50%.

Claims (1)

The method of surface plastic deformation of cylindrical parts, including the implementation of surface plastic deformation of a rotating part by a roller with constant radial force when it is informed of the feed movement along the axis of the workpiece and oscillatory movements by means of a linear step drive relative to a plane perpendicular to the axis of the workpiece, while reciprocating move the roller in a direction parallel to the impact I will mention of a linear stepper drive, characterized in that the amplitude A and frequency f of the oscillatory movements of the roller are determined by the formulas
$$f=\frac{n_{\partial }}{60}\cdot K_{HV},\text{Hz}$$

,
A = 10 ^-3 S _m (1-K _HV ), mm;
and the value of the reciprocating movement of the roller L is taken equal to L = (1.5-2.0) A, mm, where S _m is the given step of the regular microrelief on the workpiece surface, microns; K _HV - coefficient determined by the ratio of the hardness of the processed material of the part to the hardness of the material of the deformation roller; n _d - the frequency of rotation of the workpiece, rpm