RU2464153C1 - 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 used for finishing and surface hardening. Blank is fed relative to grinding wheel and indenter. The latter is arranged level with grinding wheel face in direction of feed. Indenter has strip contact with blank machined surface and is made from material with hardness exceeding than of the blank Ultrasound frequency amplitude modulated oscillations are imparted to hardening element.

EFFECT: reduced deformation forces, developed compressing residual stresses in bank surface layer.

1 dwg, 1 tbl

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 the Russian Federation No. 2241587 (publ. 10.12.2004, B24B 39/00). In accordance with it, the processing is performed by a combined tool containing a common body 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, B24B 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 strengthening 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 contact spot of which with the workpiece surface being processed has the shape of an ellipse, as a result of which the surface being hardened during processing is uneven, and the absolute the value of compressive residual stresses is relatively small.

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

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 being machined and adjusted with an interference fit relative to the operational size for grinding, while the reinforcing element plastically deforms and hardens 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, allowing a reduction in the height of microroughnesses by 2-2.5 times, obtaining high surface microhardness, and creating compressive residual stresses in the surface layer.

Distinctive features of the proposed method are the use of a reinforcing element of higher hardness compared to the hardness of the material of the workpiece, which has a strip contact with the workpiece surface and is configured to reach the abrasive tool along the axis of the workpiece so that it is flush with the end of the circle, and superimposed on the reinforcing element amplitude-modulated oscillations of ultrasonic frequency. This allows you to form compressive residual stresses in the surface layer of the processed part, as well as increase productivity up to 2 times while maintaining or improving the specified 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. As a reinforcing element, an indenter is used having strip contact with the workpiece surface. 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 around and the reinforcing element is aligned with the end of the circle . As a result of trimming the wave around, the fraction of the work of the reinforcing element spent on deformation and movement of this wave decreases, and the proportion directly spent on hardening 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-stress intensity.

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;

Vc - table feed rate.

A cylindrical billet with a diameter of 50 mm and a length of 170 mm made of structural steel 40X, high-speed steel P18 and corrosion-resistant bearing steel 95X18 was subjected to combined hardening treatment. The processing was carried out on a circular grinding machine mod. 3M151V grinding wheel 24A25NS17K26 with modes: working wheel speed 50 m / s, peripheral workpiece speed 20 m / min, coolant 3% emulsion Avtokat-F78, total coolant volume 40 l / min, feed 0.02 mm / stroke, the peripheral speed of the workpiece is 20 m / min, the longitudinal feed rate of the table is 30 mm / min; cutting depth - 0.02 mm.

As a result of the combined hardening treatment, the depth of the compressive residual stresses increased to 2.7 times with the arithmetic mean deviation of the profile of the treated surface to 1.0 μm.

The results of studies of the quality parameters of the surface layer of billets made of steel 95X18, formed during the combined processing of grinding and carbide smoothing with the application of ultrasonic testing The clamping force of the reinforcing element P, H Maximum compressive residual stresses in the surface layer σ, MPa The average deviation of the profile Ra, microns without modulation with modulated oscillations without modulation with modulated oscillations fifty 275 301 0.44 0.4 75 292 323 0.64 0.58 one hundred 311 342 0.82 0.74 125 354 390 0.99 0.89 150 373 410 1.12 1,0

Claims (1)

A method of combined processing by grinding and surface plastic deformation at the end of the working cycle of circular external grinding with a longitudinal feed, in which at the nursing stage the processing of a rotating workpiece is carried out by a grinding wheel and a reinforcing element, relative to which the workpiece is moved, characterized in that an indenter is used as the strengthening element located at the same level with the end face of the grinding wheel in the direction of feed movement, having with the machined surface rhnostyu preform and contact strip made of a material whose hardness exceeds the hardness of the workpiece material, the reinforcing member reported amplitude-modulated ultrasonic frequency vibrations.