RU2332296C1 - Method of processing defective spherical surfaces by plastic deformation - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention pertains to the technology of machine building and particularly to processing defective spherical surfaces by surface plastic deformation. There is rotatory movement of the work piece and the deforming instrument. The deforming instrument is mounted on a spindle of a device with individual actuation and made in form of a screwed coil spring. One end of the screwed coil spring is made in form of deforming ring for contact with the work piece, and the other end is wound on the above mentioned spindle. Electrical current is supplied to the deforming instrument and the processed work piece from a low voltage source and a static load is applied to the deforming ring. Rotatory motion of the deforming instrument is applied under the condition that, the deforming ring is rotated in a plane, displaced relative the centre of the spherical surface.

EFFECT: high quality and accuracy of processing spherical work pieces by surface plastic deformation.

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Description

The invention relates to mechanical engineering technology, in particular to methods based on a combination of thermal exposure and finishing hardening of incomplete spherical surfaces of parts, for example, automobile ball fingers made of steels and alloys by surface plastic deformation (PPD) with static and electric loading of the tool.

A known method of processing incomplete spherical surfaces of PPD parts, in which rotary movement is reported to the workpiece and the deforming tool, and the deformation device is informed of rotation along a circle lying in a plane offset from the center of the processed spherical surface, while the angular velocity of the deforming device is related to the angular velocity of the workpiece blanks with the ratio ω _in >> ω _d , in addition, a mathematical relationship between the loading force and the We run in [1].

The known method is characterized by low efficiency, insufficiently large depth of the hardened layer and not a high degree of hardening of the treated surface, which does not change the physical and mechanical properties of the surface layer of the workpiece, does not increase wear resistance, endurance and other operational characteristics, while the applied non-self-aligning tool does not allows you to get a high-quality machined surface.

The objective of the invention is to expand the technological capabilities of PPD through the use of electromechanical processing, based on a combination of thermal and power effects on the surface of the workpiece, which leads to a change in the surface layer of the workpiece, increase wear resistance, endurance and other performance characteristics, control the depth of the hardened layer, the degree of hardening and surface microrelief, as well as improving the quality and accuracy of processing by itself installation of the tool on an incomplete spherical surface of the workpiece.

The problem is solved by the proposed method of processing workpieces with an incomplete spherical surface by surface plastic deformation, including a message of rotational movement of the workpiece and a deforming tool, using a deforming tool mounted on the device’s spindle with an individual drive and made in the form of a coil spring, one end of which is made in in the form of a deforming ring for contact with the workpiece, and its other end face is screwed on the said spindle, In this case, an electric current is supplied to the deforming tool and the workpiece from a low-voltage source and a static load is applied to the deforming ring, and the rotational movement of the deforming tool is reported from the condition that the deforming ring rotates in a plane offset from the center of the spherical surface by h, mm, which is determined according to the formula

H = (D _SF · sinα) / 2,

where D _SF - the diameter of the spherical surface, mm;

α = arccos (H / d) is the angle of inclination of the axis of the deforming tool to a plane perpendicular to the longitudinal axis of the workpiece and passing through the center of the spherical surface, deg;

H is the size that determines the incomplete spherical surface of the workpiece, mm;

d = H / cosα is the diameter of the circle along which the deforming ring contacts the machined incomplete spherical surface, mm.

α = arccos (H / d) - the angle of inclination of the spindle axis to a plane perpendicular to the longitudinal axis of the workpiece and passing through the center of the spherical surface, deg;

H is the size that determines the incomplete spherical surface of the workpiece, mm;

d is the diameter of the circle along which the deforming ring contacts with the incomplete spherical surface of the workpiece being processed, mm.

The essence of the method of processing incomplete spherical surfaces by surface plastic deformation (PPD) is illustrated by drawings.

Figure 1 presents a diagram of the processing of surface plastic deformation of the workpiece automobile ball finger with a static loaded deforming tool; figure 2 - section a - a in figure 1.

The proposed method is used for surface plastic deformation of an incomplete spherical surface 1 in combination with the thermal and force effects of a deforming tool 2, in which the workpiece 3, for example, such as an automobile ball finger, is given a rotational movement V _s , and a rotational motion V _And and a longitudinal feed S _PR to the center On an incomplete spherical surface, while an electric current is supplied from the fixed contacts to the junction of the tool and the workpiece by rotating existing equipment items.

The method is implemented using a device for PPD of incomplete spherical surfaces, which contains an individual drive (not shown) with a spindle 4 with a deforming tool 2 mounted on it, made in the form of a coil spring 5.

A coil spring 5 is screwed onto the spindle 4 with one end face, on which a special screw groove has been cut for a fixed spring.

The second end face of the spring 5 in contact with the incomplete spherical surface 1 of the workpiece 3 is made in the form of a deforming ring 2 for contact with the workpiece.

The longitudinal arrangement of the coil spring 5 makes it possible to simultaneously transmit the rotational movement V _AND from the spindle 4 and the static load to the deforming tool 2 due to the longitudinal feed S _{PR of the} entire device, while the spring realizes the possibility of self-centering of the deforming tool relative to the workpiece.

Due to the design feature of the workpiece 3, namely the unusable spherical surface 1, the device is offset from the center of the sphere by a value of h, determined by the formula

h = (D _sf · sinα) / 2, mm;

where D _sf - diameter of the processed incomplete spherical surface 1, mm;

α = arccos (H / d) - the angle of inclination of the axis of the spindle of the device to a plane perpendicular to the longitudinal axis of the workpiece and passing through the center O of an incomplete spherical surface, deg;

H is the size that determines the incomplete spherical surface of the workpiece, mm;

d is the diameter of the circle along which the deforming ring contacts the machining incomplete spherical surface, mm.

The deforming element - ring 2 rotates in a circle with a diameter d lying in a plane that is offset relative to the center O of the incomplete spherical surface being machined by the value h, depending on the design features of the workpiece being processed.

The diameter of the circle d along which the deforming ring contacts the machining incomplete spherical surface depends on the size H, which defines the incomplete spherical surface of the workpiece, and the angle of inclination of the spindle axis of the device to a plane perpendicular to the longitudinal axis of the workpiece and passing through the center O of the incomplete spherical surface, and determined by the formula: d = N / cos α, mm. This diameter can be considered the inner diameter of the deforming ring 2 of the tool.

The incomplete spherical surface of the workpiece being processed forces the longitudinal axis of the head to be set at an angle α relative to a plane perpendicular to the longitudinal axis of the workpiece, the value of which also depends on the design features of the workpiece.

The spring connection 5 of the spindle 4 with the deforming tool - the ring 2 allows for self-centering and self-installation of the latter on the workpiece 3 with a random deviation of the longitudinal axis of the spindle 4 from the center O of the incomplete spherical surface 1. The value of the static deformation force created by the longitudinal movement of the device depends on properties of the spring 6, namely, from the material of the wire from which the spring is wound, its diameter, the diameter of the turns of the spring and the number of working turns, laid between the end face of the spindle 4 and the ring 2.

In order to reduce the value of the static deformation force, which is chosen to be the largest among those providing elastic contact deformations of the processed material, an electric current from a low-voltage source was supplied to the deforming tool and the workpiece [2].

PPD with the supply of electric current leads to a change in the physico-mechanical and geometric parameters of the surface layer and, as a result, to increase wear resistance, endurance and other operational characteristics. The effect of PPD with the passage of electric current is achieved due to the fact that superfast heating and cooling rates are realized and a high degree of fineness of the austenitic grain is achieved, which determines the fine-crystalline quenching structures of the surface layer, which has high physical, mechanical and operational properties.

When implementing PPD with electric current transmission, direct and alternating current were used. The use of direct current with small efforts can significantly reduce the initial roughness. So, with the same current strength, the height parameters of the initial surface roughness can be reduced by 2 ... 3 times, with alternating current they can be increased by 4 ... 6 times. This is due to better heating of micro-irregularities, a decrease in their resistance to deformation and a decrease in vibration. However, when hardening by direct current, there is a sharp difference in the hardness of the hardened layer and the unhardened core, which can lead to peeling of the surface layer and to a decrease in fatigue and contact strength.

The use of alternating current provides a smooth transition of hardness from the surface to the core, a greater depth of hardening and a higher microhardness of the hardened layer.

The accuracy of the shape of the processed incomplete spherical surface of the workpiece by the proposed method with the help of an electrodeforming device increases and decreases the roughness due to self-centering and self-installation of the tool on the workpiece during its beating and vibration.

The depth of the hardened layer of the proposed method reaches 0.5 ... 1.5 mm, which is significantly (1.5 ... 2 times) more than with traditional hardening. The highest degree of hardening is 15 ... 25%. As a result of processing the proposed method in comparison with traditional PPD, the effective depth of the layer, hardened by 20% or more, increases by 1.5 ... 2.2 times, and the depth of the layer hardened by 10% or more, by 1.3 ... 1.6 times.

Example. To assess the quality parameters of the surface layer hardened by the proposed method, experimental studies of the processing of an automobile ball finger using an electrodeforming device were carried out. The workpiece of the ball upper finger 2101-2904187, installed in a special electromechanical device, was strengthened on the machine mod. 16K20 by the proposed method. The blank is made of steel 40X GOST 1050-74. An incomplete sphere with a diameter of 32.7 ± 0.1 was processed; the initial roughness parameter Ra = 3.2 μm, achieved - Ra = 0.63; deforming tool in the form of a cylindrical helical spring made of heat-treated steel grade 65G, the working surface of the spring deforming ring was polished to Ra = 0.08 ... 0.16 μm. The incomplete scope of the workpiece was processed in the following modes: workpiece rotation speed V _s = 10 m / min (n _s = 100 min ^-1 ); the strain rate V _and = 50 m / min (n _and = 500 min ^-1 ); longitudinal feed S _CR = 0.1 mm ^{-1 of the} deforming tool was carried out until the magnitude of the force of static pressing of the tool to the work surface P _article ≥25 ... 40 kN .; the depth of the layer of high hardness was 0.15 ... 0.20 mm; current density 700 ... 1500 A / mm ² .

The required roughness and accuracy of an incomplete spherical surface was achieved in T _m = 0.7 min (against T _m ^bases = 2.75 min according to the basic version in the traditional processing of PPD at the Oryol steel rolling mill OSPAZ). The control was carried out by an indicator bracket with an indicator ICh 10 B cells. 1 GOST 577-68 and on the profilometer mod. 283 type AII GOST 19300-86. In the processed batch (equal to 100 pieces), no defective parts were found. The deviation of the treated surface from sphericity was not more than 0.02 mm, which is acceptable TU.

The processing showed that the roughness parameter of the processed incomplete spherical surfaces decreased to Ra = 0.32 ... 0.63 μm with the initial Ra = 3.2 ... 6.3 μm, the productivity increased more than three times in comparison with traditional warping.

Studies of the stress state of the hardened surface layer showed that the maximum residual stresses are close to the surface, as when chasing, which is favorable for most of the mating parts of mechanisms and machines. Comparison of the depths of the stressed and hardened layers, the stress gradient and the hardening gradient shows that the depth of the stressed layer is 1.1 ... 1.3 times greater than the depth of the riveted layer, which is consistent with the theory of surface - plastic deformation.

The maximum roughness value achieved during processing by the proposed method is Ra = 0.08 μm; a possible initial roughness reduction of 4 times is possible.

The static load created by the self-centering device favorably affects the working conditions of the tool - the ring. Self-centering leads to a more even distribution of the load on the deforming tool - the ring, and the use of electric current facilitates the normalization of the hardened surface.

When applying a static load, the deforming surface of the tool - the ring wears out equally, which helps to increase the overall durability of the device.

The proposed method extends the technological capabilities of PPD due to the use of electrodeformation with a self-centering deforming tool - a ring, which makes it very easy to control the depth of the hardened layer, the degree of hardening and the surface microrelief, and also improves the quality and accuracy of processing by self-installing the tool on an incomplete spherical surface of the workpiece.

Electrodeformation allows achieving not only the required surface roughness, but also the ability to obtain a hardened surface layer structure with increased wear resistance, which is caused by its high hardness, strength and fine-grained structure. Compressive residual stresses in the surface layer favorably increase the contact strength. In addition, the wear resistance is increased due to the formation after electrodeformation of a large bearing capacity of the profile than after mechanical and heat treatment, which reduces the running-in time.

Information sources

1. RF patent 2031770, MKP ⁶ V24V 39/04, 39/00. A method of processing incomplete spherical surfaces of parts by surface deformation. Gavrilin A.M., Samoilov N.N. 5045958/27; 04/14/92; 03/27/95. Bull. No. 9 is a prototype.

2. Suslov A.G., Gorlenko A.O., Sukharev S.O. Electromechanical processing of machine parts. // Reference. Engineering Journal, No. 1, 1998. P.15-18.

Claims (1)

A method of processing workpieces with an incomplete spherical surface by surface plastic deformation, including a message of rotational movement of the workpiece and a deforming tool, characterized in that they use a deforming tool mounted on the device’s spindle with an individual drive and made in the form of a coil spring, one end of which is made in the form of a deforming rings for contact with the workpiece, and its other end face is screwed on the said spindle, while the electric ca. to the deforming tool and workpiece by a low voltage source and is applied to the deforming ring static load, and rotational movement of the deforming tool reports the condition of the rotation of the ring deforming in a plane offset from the center of the spherical surface by an amount h, mm, which is defined by the formula h = (D _sp · sinα) / 2, where D _SF - the diameter of the spherical surface, mm; α = arccos (H / d) - the angle of inclination of the axis of the deforming tool to the plane perpendicular to the longitudinal axis of the workpiece and passing through the center of the spherical surface, deg; H is the size that determines the incomplete spherical surface of the workpiece, mm; d = H / cosα is the diameter of the circle along which the deforming ring contacts the machined incomplete spherical surface, mm; α = arccos (H / d) - the angle of inclination of the spindle axis to the plane perpendicular to the longitudinal axis of the workpiece and passing through the center of the spherical surface, deg; H is the size that determines the incomplete spherical surface of the workpiece, mm; d is the diameter of the circle along which the deforming ring contacts with the incomplete spherical surface of the workpiece being processed, mm.

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