RU2423220C1 - Method of combined processing by grinding and surface plastic deformation - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be sued for finishing and surface hardening. Workpiece is subjected to circular surface grinding, machining by grinding wheel and hardening element made up of indenter, and is fed relative to both. Said indenter is made of material with hardness exceeding that of machined surface and brought in strip contact with workpiece. It is arranged extended relative to wheel surface in either side in feed direction. Ultrasound frequency amplitude modulated oscillations are imparted to hardening element.

EFFECT: higher efficiency and quality of processing and hardening.

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Description

The invention relates to mechanical engineering and can be used for finishing and hardening workpieces of parts such as bodies of revolution from various metals and alloys.

Known combined grinding method with friction surface hardening according to the patent of Russian Federation No. 2241587 (publ. 10.12.2004, B24B 39/00). In accordance with it, the processing is performed with a combined tool containing a common housing in the form of a sleeve and a coaxial grinding wheel and a hardening tool located on it. Improving the productivity and quality of processing in the specified method is achieved by installing a grinding wheel with axial displacement of the peripheral cutting layer with the possibility of restoring the outer diameter and changing the oscillation amplitude of its cutting layer, and the hardening tool with the ability to tilt to a plane perpendicular to the common axis of rotation of the combined tool .

The reasons that impede the achievement of the technical result indicated below when using the known method include the fact that the known method does not provide effective hardening of the surface layer of the workpiece, since a significant part of the work of plastic deformation is spent on moving the wave of the workpiece material plastically displaced by the strengthening tool. In addition, during such a combined treatment, the hardened layer is removed by the working surface of the grinding wheel. As a result, the depth of the hardened layer is relatively small.

There is also a method of combined processing by grinding and surface plastic deformation of workpieces of parts such as bodies of revolution according to RF patent No. 2006128862 (publ. 02.20.2008, V24V 39/04), adopted as a prototype. In accordance with it, the combined processing is carried out by a grinding wheel and a hardening tool at the end of the working cycle of circular external grinding with longitudinal feed, at the stage of nursing. Moreover, the hardening tool is adjusted with an interference fit with respect to the polished surface, i.e. with a departure relative to the working surface of the grinding wheel, and move during processing together with the grinding wheel along the workpiece surface. In this case, the deforming tool is placed in the same section with the grinding wheel so that the wave of the workpiece material displaced by the deforming tool is cut in a circle.

The reasons that impede the achievement of the technical result indicated below when using the known method include the fact that an indenter is used as a reinforcing element, the shape of the contact spot of which with the workpiece surface being treated has the shape of an ellipse, as a result of which the surface being hardened during processing is uneven, and the absolute value of the compressive residual stresses is relatively small. In addition, this process has low productivity due to the loss of accuracy at the speeds used in the implementation of the proposed method.

The technical result consists in improving the quality of the combined processing due to the formation of compressive residual stresses of a greater magnitude in the surface layer of the machined part and increasing the productivity of the process by superimposing amplitude-modulated ultrasonic frequency vibrations on the reinforcing element, and the plate having a strip contact with the workpiece is used as the latter and made of a material whose hardness exceeds the hardness of the material being processed.

To achieve the technical result in the proposed method of combined finishing at the end of a round external grinding cycle with a longitudinal feed, at the stage of nursing, a reinforcing element is brought to the workpiece surface having a strip contact with the workpiece surface to be machined and tightened relative to the operational size for grinding, while the reinforcing element plastically deforms and strengthens the surface layer of the workpiece with the simultaneous formation of d “waves” of extruded material. The top of this wave is cut by the working surface of the grinding wheel, while the working conditions of the smoother are facilitated, which helps to increase the degree and depth of hardening. The use of amplitude-modulated ultrasonic vibrations contributes to a significant reduction in the deformation forces required to obtain equivalent deformations, making it possible to reduce the microroughness height by 2–3 times, obtain high surface microhardness, and create compressive residual stresses in the surface layer.

Distinctive features of the proposed method are that when nursing feed the workpiece by moving it relative to the grinding wheel and the reinforcing element, and the amplifying element is informed by amplitude-modulated ultrasonic frequency vibrations, while an indenter made in the form of a plate of material is used as the reinforcing element , the hardness of which exceeds the hardness of the workpiece material, having a contact strip surface with the workpiece being machined and located th tickets relative wheel surface in one direction or another in the direction of feed movement.

This allows to improve the quality of processing due to a decrease in the height of microroughnesses and the formation of compressive residual stresses in the surface layer of the processed part, as well as to increase productivity up to 2 times while maintaining or improving the quality parameters of the surface layer of the processed part.

Information confirming the possibility of implementation is as follows.

The essence of the invention lies in the fact that the combined processing of a rotating workpiece is carried out by a grinding wheel and a hardening tool at the end of the working cycle of circular external grinding with a longitudinal feed, at the nursing stage, relative to which the workpiece is moved. An indenter having a strip contact with the workpiece surface to be treated is used as a reinforcing element. An indenter made of a material whose hardness exceeds the hardness of the material being processed is pressed against a ground surface and placed in the same section as the grinding wheel so that the wave of workpiece material displaced by the reinforcing tool is cut in a circle and the reinforcing element itself is adjusted with a projection relative to the surface of the circle in one or the other side in the direction of feed movement. As a result of trimming the wave in a circle, the fraction of the work of the reinforcing element expended in deformation and movement of this wave decreases, and the proportion directly expended in strengthening the surface layer of the workpiece increases. In this case, the reinforcing element is informed by amplitude-modulated oscillations of the ultrasonic frequency, which significantly reduce the cost of friction in the processing zone, and therefore reduce the heat-power tension.

The proposed method is illustrated in the drawing, which shows the options for combined processing. The diagram shows:

1 - grinding wheel;

2 - blank;

3 - reinforcing tool;

a, b, c - options for the relative position of the circle and the reinforcing element.

A cylindrical billet with a diameter of 50 mm and a length of 170 mm made of structural steel 40X, tool high-speed steel P18 and corrosion-resistant bearing steel 95X18 was subjected to combined hardening treatment. Processing was carried out on a circular grinding machine mod. 3M151 In a grinding wheel 24A25NS17K26 with modes: working speed of a wheel of 50 m / s, peripheral speed of a workpiece - 20 m / min, coolant - 3% emulsion Avtokat-F78, total volumetric flow rate of coolant 15 l / min, feed 0.02 mm / stroke , the peripheral speed of the workpiece 20 m / min, the speed of the longitudinal feed of the table is 30 mm / min; cutting depth - 0.02 mm. As a coolant, we used a 3% emulsion of Avtokat-F78 product, which was supplied with a volumetric flow rate of 20 dm ³ / min.

As a result of combined hardening treatment, the depth of compressive residual stresses increased up to 3 times with the arithmetic mean deviation of the treated surface profile to 0.1 μm.

Claims (1)

A method of combined processing, including round external grinding of a workpiece, at the end of the working cycle of which the rotating workpiece is processed with a grinding wheel and a reinforcing element, relative to which the workpiece is moved, characterized in that an indenter having a strip contact with the workpiece surface is used, located with a departure relative to the surface of the circle in one direction or another in the direction of feed movement and a series whose hardness exceeds the hardness of the material of the workpiece, while the reinforcing element is reported amplitude-modulated oscillations of the ultrasonic frequency.