CS215622B1 - A method of reinforcing machine parts with projections and devices for performing this method - Google Patents

Abstract

The invention relates to a method of strengthening machine components with protrusions, operating in particular with a variable direction of operating load, which consists in plastic deformation of the protrusion material in bending and in strengthening treatment of the surface layer of the protrusion in the area of its dangerous cross-section from the side of the bending force. The action of the bending force and the strengthening treatment of the surface of the protrusion in the area of its dangerous cross-section are carried out according to the invention simultaneously, while the strengthening treatment of the surface of the protrusion in the area of its dangerous cross-section is carried out by applying a normal pressure force, distributed over this surface, to the surface of the dangerous cross-section of the protrusion. The invention also relates to a device for strengthening components with protrusions, in particular gears, comprising pressure rollers having a tooth shape in cross-section and adapted to carry out the method according to the invention.

Description

The invention relates to the technology of strengthening machine components by changing their state of tension and the physical properties of the metal from which they are made, namely by their plastic deformation, and in particular to a method of strengthening machine components with protrusions and a device for carrying out this method.

The subject of the invention is best suited for strengthening such machine components with projections which operate with a variable direction of operating load, for example gear teeth, turbine blades and the like.

Currently, methods for increasing the strength of machine components, using plastic deformation of the component during its strengthening, are widely used. In these cases, plastic deformation is used with the aim of changing the physical properties of the metal, primarily the tensile strength, yield strength, hardness, macro- and microstructure, as well as the inherent stress.

It is known that plastic deformation of a metal capable of increasing strength leads to an increase in its tensile strength, yield strength and hardness compared to the initial values.

In addition, if a profile of a component is in an uneven state of stress during plastic or elastic-plastic deformation, residual stresses arise in this cross-section after the load is removed, which are caused by the sharply varying degree of deformation of the individual sections.

Known technological processes for strengthening metal components, which use the above-mentioned physical phenomena to plastically deform the surface of the components, are referred to as surface plastic deformation (SPC). The SPC process is particularly suitable for components with stress accumulation areas and for components with loaded protrusions operating under conditions of variable loads. This process is primarily used, as is known, for components with protrusions, such as gears, turbine blades and crankshafts. This plastic deformation is carried out by shot blasting the processed surface of the protrusions with balls or by rolling it with rollers or by pressing a diamond tool onto it.

In one known process, this strengthening, applied to gears, is carried out by plastic deformation of the tooth profile by ovalizing the tooth profile with toothed rollers. The plastic deformation of the metal is achieved in this case by temporary radial displacement of the toothed rollers, which are applied and a certain tightening corresponding to the required degree of strengthening. The rollers plastically deform the metal of the tooth profile of the gear being strengthened by performing plastic deformation of its surface, which leads to an increase in the strength values of the component.

Strengthening by plastic deformation of the surface is, for example, carried out using a device according to Soviet author's certificate 158 911, consisting of a drive mechanism and a stand on which a mechanism developing plastic deformation is mounted, and a device for fixing the part to be strengthened, whereby the plastic deformation of the surface occurs by mutual attraction between the teeth of the strengthened gear wheel and the working rollers of the said mechanism.

In the known process, the metal strengthening is distributed to a limited depth, which, for example, does not exceed 3 mm for teeth with a module of 10 to 11 mm. This leads to the fact that the depth of the residual compressive stresses at a module of m = 10 mm does not exceed 0.7 mm and therefore has a relatively insignificant effect on the stresses distributed in the components during operation. Thus, plastic deformation occurs

215 622 only a thin surface layer of material of the protrusions of the component being strengthened, and attempts to increase the depth of the strengthened layer by increasing the pull of the toothed roller do not lead to the desired result, since excessive strengthening of the material on the surface leads to its peeling.

It should be noted that the depth and nature of the distribution of residual compressive stresses significantly affect the load-bearing capacity and strength of machine components with protrusions. However, known methods of plastic surface deformation do not allow achieving such a distribution of residual stresses, in which, under the action of operational loads, the resulting stresses in the protrusion material of the relevant component are sufficiently evenly distributed over the entire dangerous cross-section of the protrusion.

The nature of the distribution of residual stresses when using known surface plastic deformation procedures leads to the fact that the maximum stresses resulting from the effects of the operating load are deposited in the surface layer of the material, while the core material, which contributes insignificantly to the absorption of the operating load, is practically excluded from the interaction.

Further, there are known methods of strengthening which use the three-dimensional strengthening of machine parts with projections in cold. In one known method of this kind, described in US Patent No. 3,851,512, this strengthening is achieved by plastic deformation of the teeth by bending, namely in the direction of the main operating load. By the fact that the teeth of the gear wheel to be strengthened are subjected to bending, which induces stresses in the tooth material above the yield point with the same sign as the stresses induced by the operating load, residual stresses arise in the dangerous cross-section of the teeth, which have a significant effect on the redistribution of stresses induced by the operating load and ensure a more favorable energy state of the tooth material, including the core material, during the operation of the gears.

Plastic deformation by bending allows for cold hardening of the material in a large part of the dangerous cross-section, which is not acceptable for strengthening methods that use plastic deformation of the surface.

Strengthening of gear teeth by plastic deformation by bending in the direction of the main operating load is carried out using a device comprising a stand on which a mechanism creating plastic deformation is mounted, a device for fastening the processed gear wheel, and a drive device for the mutual relative displacement of this mechanism and the gear wheel. The mechanism creating plastic deformation is made in the form of a ring with internal protrusions, which during the mutual displacement of the ring and the gear wheel, placed inside on the fastening device and arranged coaxially, interact with the teeth of this wheel along their length, in such a way that these teeth bend and induce stresses in the material of the teeth above the yield point with the same sign as the operating load. As a result, the dangerous cross-section is spatially deformed.

The disadvantage of this method is that residual tensile stresses arise on the side of the teeth facing the application of the technological load. This limits the scope of application of the method to gears whose teeth are loaded predominantly in one direction. In addition, the consumption of potential energy of the tooth core for the expansion of the front end, which is pushed forward, reduces the absolute magnitude of the residual stresses remaining on the working side of the tooth, thereby reducing the strengthening effect. The method is also ineffective in the case of static operational loads, which limits its application to those components that operate under cyclic loads.

A method of processing components is also known, allowing to increase the strength of gears.

There is also a known method of processing components, allowing to increase the bending strength of gear wheels, which take on loads with an arbitrarily variable direction during operation. This method consists in subjecting the gear teeth to plastic deformation in bending and then exposing the surface to thermal processing in the area of the dangerous cross-section, one after the other, one after the other. As a result of this thermomechanical processing of the component along both edges of the tooth profile in the area of stress accumulation, the strength properties of the material are improved and residual compressive stresses are induced, thereby ensuring the possibility of effective and wide application of this method for components that are exposed to any degree of variability in the direction of the operating load. The residual displacements of the deformed sections of the component under technological loading on one side are reduced due to deformation in the opposite direction. This facilitates the task of achieving the original or other predetermined profile of the working section of the component.

The thermomechanical hardening method can be carried out according to any technological cycle, and to increase the effect this cycle can be baked several times. Contour hardening allows to achieve without special technological work processes to achieve an increase in the contact strength of the working surfaces of the components and their wear resistance.

This method basically consists of elastic-plastic bending with simultaneous, rapid sequential processing of the surface layer in the area of the dangerous cross-section, which first improves the plastic properties of the material in the area to be strengthened by rapid heating and then fixes the obtained strengthening by hardening. On the one hand, this provides the possibility of improving the resistance

-to strengthen components with variable direction of loading against fatigue, but on the other hand it leads to a number of shortcomings.

One of the disadvantages is that the increase in the plasticity of the material is associated with heating and thus. to a decrease in its strength and to a decrease in the core elastic resistance, which somewhat limits the magnitude of the technological bending force, the effect of spatial strengthening and the size of the strengthened area. The subsequent surface strengthening by hardening significantly reduces the plasticity of the material and therefore excludes the continuation of the strengthening of deformations under the previous technological load. In addition, heat treatment obviously increases the sensitivity of the material to the accumulation of unstressed, which somewhat reduces the effect of spatial strengthening.

The combination of external force action and simultaneous heat treatment (full cycle) on one and the same side of the profile of the part projection reduces the stability of the strengthening and limits the area of application of the method to parts in which the areas of bending force and heating are sufficiently distant from each other. The sections of the surface of the parts between these areas are required to have high strength properties, since during heat treatment a transition zone with reduced strength and residual tensile stresses is created. In addition, these circumstances significantly complicate the design of the strengthening device and the technological process of processing the part, and lead to demands on a high number and qualification of operating personnel and high energy consumption.

When processing components after their chemical-thermal hardening, the aforementioned method may also result in a decrease in the hardness and strength properties of the surface layer of the material. The change in the state of tension on the front surfaces of the component protrusions further leads to a decrease in the effect of hardening in those cases where the state of these surfaces affects the ability to take on loads. This circumstance also results in an increase in the sensitivity and decrease in the stability of the processing regime due to the significant difference in the requirements for the hardening conditions on the front surfaces β in places distant from these surfaces. This is especially evident during significant plastic deformations of the material.

When strengthening components with alternating protrusions and depressions, when performing the aforementioned method by creating a mechanical loading scheme at the points of contact of the loading device with the processed component on the surface of the processed protrusions, friction tangential friction forces arise, due to the necessary introduction of the elements of the loading device into the depressions of the component and the displacement of the loading device in these depressions. This results in the fact that for components that have small angles on the loaded surface sections, the loading method and the state of tension change dramatically. The radial loading component is larger, the effect of bending and shearing is reduced, the control of the hardening ratios becomes more difficult and the stability of the hardening also decreases.

The invention aims to eliminate the above-mentioned disadvantages. Its aim is to create a method for strengthening machine components with protrusions and a device for performing this method, which would allow strengthening by spatial plastic deformation without restrictions with regard to the variability of the direction of the external load and the nature of the cycle of its transformation, while the method would be suitable for machine components with protrusions of different shapes, operating when changing the direction of the operating load and the cyclic nature of its action, while taking into account various technological processing schemes and contributing to a significant increase in the ability of machine components with protrusions to transmit loads.

This task is solved by a method of strengthening components with protrusions, working in particular with a variable direction of operating load, which consists in plastic deformation of the protrusion material in bending with strengthening treatment of the surface layer of the protrusion in the area of its dangerous cross-section from the application of a bending force, in which, according to the invention, the application of a bending force and the strengthening treatment of the surface of the protrusion in the area of its dangerous cross-section are carried out simultaneously, while the strengthening treatment of the surface of the protrusion in the area of its dangerous cross-section is carried out by applying a normal pressure force, distributed over this surface, to the surface of the area of the dangerous cross-section of the protrusion of the component.

Strengthening by the method according to the invention allows to increase the plasticity of the material by changing the state of tension ns of the surface of the component in the strengthened area, while strengthening occurs by spatial plastic deformation of the non-drawn side of the component, which causes a favorable enistropy of the plastic properties of the component 8 increases the strength of components operating with any degree of variability of the direction of the operating load and with any cycle of previous thermal or thermochemical treatment. This effect is achieved as a result of the simultaneous increase in the plasticity and strength of the material of the surface layer of the component in the area of dangerous cross-section and elastic-plastic bending. '

This, as well as the processing by means of a surface-distributed force, which exerts hydrostatic pressure throughout the entire region of high bending stresses, makes it possible to use large bending forces and, as a result, to achieve full spatial bending strengthening and to extend this strengthening even to components with a variable direction of operating load.

The expansion of the range of components that can be processed using the method according to the invention, as well as the simplification of the technology and the increase in the stability of the hardening result from the fact that there is no combination of force application and simultaneous heat treatment on the same side of the component profile. The hardening can thus be carried out even for components of the gear type with a relatively small height of the protrusions and with high requirements for strength properties outside the area of the dangerous cross-section, as well as for components made of materials that are difficult to harden, with a significant accumulation of stress. The design of the hardening device and the technological workflow are thereby significantly simplified, and there is no need for a very high qualification of the operating personnel and the demands on their number are reduced. At the same time, the demands on energy consumption and safety technology are reduced.

The method is carried out taking into account the peculiarities of spatial strengthening that occur when processing various components.

It is expedient to develop a component in addition to the main load of the force, which is distributed over the front surfaces of the protrusion along the area of its dangerous cross-section. This will achieve that ee increases the plastic deformation of the material during bending and residual stress in the strengthened area, reduces the sensitivity to changes in the strengthening parameters and increases the ability of the components to transfer loads.

Furthermore, it is expedient to subject the adjacent protrusions of the component, forming together a common recess, to spatial plastic deformation in bending by exposing them to the simultaneous action of forces directed from the area of the common recess in mutually opposite directions.

This solution allows to achieve a state of stress of the component with residual phenomena, which are symmetrical by the nature of the distribution with respect to the axis of the recess between the reinforced protrusions, which excludes the change of the directions of plastic deformation and the associated reduction of the yield strength of the material at the root of the protrusion, the so-called Bauschinger phenomenon. In addition, the technological main forces have opposite signs and compensate each other. The resulting radial forces are also easily compensated, for example, during the simultaneous strengthening of diametrically opposed recesses.

The considerable technological forces during bending of the reinforced projection, which are possible due to the absence of thermal action on the component and due to the corresponding reduction in the strength properties of the material during processing, increase even more significantly by the distribution of the force in the area of the dangerous cross-section of the projection, the effect of which causes a technological shear force, especially in the area below the dangerous cross-section, with pressures of about 1/2 in the corner area, which are greater than the normal tensile stresses.

This peculiarity of the stress state of the component allows for effective strengthening of areas that lie significantly lower than the dangerous cross-section of the protrusion and avoiding the gradual strengthening of the material at the bottom of the recess by mechanical cold forming (which eliminates the anisotropy of the material, which is characterized by the Bauachinger effect, and the corresponding reduction in the strength properties of the component at the bottom of the recess).

In addition to eliminating the Bauschinger effect, such a scheme of technological loading of the component and the additional shear and the effect of ail acting from the common recess moves the area of maximum tensile stresses to the root of the protrusion and achieves an effective strengthening of the bottom of the recess, which increases the scope of use for longer types of processed components, for example, for components β with a thin rim, in which the rim is mounted on the rim while hot, and β with a small diameter.

It is expedient to apply a simultaneous additional force to the loaded part of the surface of the component being strengthened, acting along the lateral surface of the protrusion. As a result of such a solution, it is possible to strengthen

215 622 parts with a complicated profile of the protrusion (with profile angles increasing towards the apex) or with small profile angles. At the same time, the tangential forces do not increase the radial component of the total load, the tensile stresses of the protrusions on the side of their common recess increase, the compressive stresses on the opposite sides of their profiles decrease, and the nature of the distribution of the existing stresses improves with a simultaneous increase in their size. Even with a significant share in the profile angles of various sections of the processed surface, the absence of radial components of tangential forces facilitates, regardless of this fact, the controlled control of the strengthening parameters.

Furthermore, it is expedient that the working surfaces of the protrusions, simultaneously with the development of the main bending load on the same side of the profile, are exposed to the action of an additional force, which is distributed on it in such a way that, together with the bending of the protrusion, it induces a stress in it above the yield strength of the material, while the processing is carried out in a lubricant.

Such a solution allows, given the selected loading scheme in areas outside the geometric concentrator, where the gradient of bending stresses is significantly lower than in the concentrator, to increase not only the hydrostatic pressure and plasticity of the material, but also the magnitude of the remaining compressive stresses, the depth of their deposition* and the hardness of the surface layer, to a significant extent, while achieving the effect of spatial plastic deformation and eliminating its limitation on this surface, which would lead to the risk of cracks. At the same time, due to the influence of thermodynamic factors, namely an increase in temperature at high pressure, in combination with plastic deformation, favorable conditions for the adsorption of active substances are created, which leads to an even greater increase in the resistance of components to wear and seizure, to improving their running-in conditions, and to achieving other adaptive properties, and also contributes to improving the quality of the processed surfaces and increasing the service life of the strengthening tool.

Such processing allows the component to be strengthened outside the area of the geometric concentrator and at the same time increases the magnitude of the bending force during strengthening, as well as the strength of the component in the area of the geometric concentrator. This leads to an increase in the strengthening effect of the component.

It is expedient to expose the basic body of the component, which is connected to the dangerous cross-section of the protrusion, simultaneously with the plastic deformation of the protrusions, to a compressive force acting in a plane parallel to the dangerous cross-section. This will allow to reduce the maximum stress at the root of the protrusion and thus increase the technological load, distributed over its effective profile, as the final result of the effect of strengthening the protrusion, and thus improve the overall load-bearing ability of the component.

For components with a thin rim, it is also useful to compress the component at the moment of deformation of the protrusions with a force distributed over the base or surface of the bearing until the necessary form of the deformation state and the rim stress is achieved, which imitates the effect of the bearing during operation. This provides the possibility of simulating the stress field characteristic of a pressed bearing during the spatial deformation of the protrusions in bending. The mutual overlapping of the two stress states, namely the bending stress and the stress induced by compression, during the subsequent casting into the supporting Component, favorably affects the reproduction of the symmetrical residual stress diagram inherent in the reinforced protrusions, and the compressive stresses acting on both sides of the dangerous protrusion cross-section. In addition, pressing the root of the protrusion at the moment of bending increases the normal component of the bending force that is required for strengthening, which leads to an increase in the depth and degree of surface hardening of the active sections of the protrusions.

It is also expedient that during the processing of the projection of the component, an additional shear force is developed in the area of strengthening, which acts against the shear effect of the force causing plastic surface deformation. This makes it possible to strengthen machine components with projections of great length with a large arm of bending force, while the state of tension of the component is not disturbed, since the advantages of spatial plastic deformation by bending are fully realized by the compensating loads.

It is advantageous to subject the basic body of the component adjacent to the area of the dangerous cross-section to torsion at the same time as the deformation of the projection. This will allow strengthening to be carried out while creating a predetermined depth and direction of the residual stress field in the body of the component, and will increase the ability of the component to take on various types of loads during operation, which in turn allows for extending the service life of components such as gears, rotating parts such as shafts, turbine blades, etc. The deformation of the component by torsion creates a plastic anisotropy of the material of its projection, with which the possibilities of controlled deformation by bending are in good agreement.

It is also advantageous to apply the load using a force evenly distributed over the surface of the protrusions, e caused by the action of the compressed medium on the surfaces of adjacent protrusions forming an intermediate recess, s on their end faces. Such a solution allows to achieve strictly identical loading conditions for all protrusions of the part, and contributes to high stability of the strengthening process, minimizes technological power losses, reduces wear and thus results in improved product quality and increased equipment utilization.

The invention further relates to a device for carrying out a method of strengthening machine parts with protrusions, comprising pressure rollers having a tooth shape in cross-section and a head formed by a transition curve of two adjacent teeth of the processed gear wheel and with a heel, and a drive device for pressing the pressure rollers onto the teeth of the processed gear wheel, wherein according to the invention each pressure roller consists of inner plates, side plates and closing plates, mounted on a support connecting to the heel of the pressure roller, wherein the heel of the pressure roller is formed by inner plates and side plates and has a wedge shape in cross-section, the angle of which (2JLU) is equal to the angle between the tangents to the modified profile of two adjacent teeth of the processed gear wheel, and the head of the pressure roller is formed by the closing plates.

This solution provides the possibility of subjecting the protrusions of the processed component to spatial plastic deformation by bending with simultaneous plastic deformation of the surfaces of the protrusions in the area of their dangerous cross-section, which contributes to increasing the strength properties of the component material. High specific pressures that arise at the points of contact between the pressure roller and the tops of the reinforced protrusions lead to profile modifications of the heads of these protrusions.

It is expedient if the inner plates are formed as elastic elements that complement each other and are spaced apart with respect to the support, and the side plates ae and ae touch these inner plates.

This solution allows to carry out all technological operations for spatial plastic deformation by bending, and at the same time provides the possibility to increase the strengthening effect by using the adaptive properties of the structure of both the device itself and the material being strengthened. The use of internal plates, which have characteristic properties similar to spring elements, allows to implement technological loads during strengthening with any predetermined accuracy and to use the damping properties of the device, which take into account such characteristic properties of the strengthened component as compliance, manufacturing accuracy of the profile and surface hardness. The design according to the invention thus allows to respond gently to changes in the above-mentioned parameters and in this case to use the adaptive properties of the device itself.

It is expedient that when strengthening machine components with protrusions that are characterized by different compliance and adaptation properties, the internal plates of the device are designed, for example, as disc springs. This will allow expanding the range of use of the device by changing the force characteristics of its elements and introducing nonlinearity of stiffness parameters.

The support is preferably provided with holes for supplying lubricant to the bridges of the inner plates. This will allow various types of lubricants to be supplied to the contact points of the plates, which will significantly change the friction coefficients and thus the adaptive properties of the device itself. This will provide the possibility of adjusting these values in a wide range according to the requirements imposed on the conditions of consolidation.

As a result, the stability of the consolidation process increases.

The invention is explained in more detail in the following description, containing specific examples of conditions and parameters when performing a number of technological procedures for strengthening machine components according to the invention.

Example 1

An example of the method according to the invention for a component with a single protrusion is observed (Fig. 1).

A component intended for reinforcement, forming part of the drive mechanism of a device for granulating mixed feed, and designed in the form of a shaft with a projection 1 of height H - 100 mm with a thickness S ==22 mm, with a geometric concentrator in the form of a circular arc with a radius of 40 mm, made of chromium-nickel steel with the chemical composition: C = 0.45, Si = 0.18, Mn = 0.60, Ni = 1.15, P - 0.035, s = 0.035 and with a yield strength of 58 kp/mm, is subjected to spatial plastic deformation with a force of 70 kp/mm on the side ab of the profile, which creates a stress above the yield strength of the material in the area of the dangerous cross-section ec, and at the same time is exposed to the effect of a force distributed in the area of the dangerous cross-section ac as a result of the action of the cutter 2 pushing with a force B ₂ ^with Kp/mm, which evokes *

normally forces up to 30 kp/mm, creating a triaxial state of tension on the surface of the component, the effect of hydrostatic pressure, an increase in the plastic properties of the component in the pressure area of the protrusion, and their decrease on the opposite side of the protrusion.

As a result, a special anisotropy of the plastic properties of the component arises during spatial deformation, which allows obtaining a three-layer residual stress diagram and significant residual stresses of a negative sign in the peripheral regions of the dangerous cross-section.

After the effect of the load by force P^ and the pressure of the punch 2 has disappeared, the projection 1 of the component is subjected to spatial plastic deformation by force P^ =80 kp/mm on the side cd of the profile, which in the zone of the dangerous cross-section ae induces a stress above the yield strength of the material, 8 at the same time it is exposed to the action of a distributed force in the area of the dangerous cross-section ac by the pressure of the punch 2 with force Pg* = 80 kp/mm. As a result, spatial deformation occurs only on the side cd, which strengthens the previously obtained three-layer diagram of residual stresses Cp, which shows the presence of significant compressive stresses in the area of the peripheral sections of the dangerous cross-section.

The method is carried out using a universal device with hydraulic or mechanical presses and punches.

The result of processing the component in the described manner is an increase in the shaft's ability to transmit bending loads by more than 1.5 times.

Example 2

An example of implementing the method according to the invention on a component with small thicknesses with end faces is observed (Fig. 2). The component, which is the axis of the drive mechanism for a compound feed granulation device, made of steel with a yield strength of 58 kp/mm ² , is loaded with a bending force P^ = 80 kp/mm, which causes plastic deformation of the material in the area of the geometric concentrator (circular arc with a radius of 20 mm), while at the same time on the drawn side of the projection 1 with a height H ~ 158 mm, thickness S » 34 mm and length L - 100 mm, a force P ₂ - 300 kp/mm acts on the plastically deformed material using a punch 2 and on the end faces using cutters 2 forces Pj = 120 kp/mm, thereby developing pressure in the areas of plastic deformation of the material.

In this case, various devices can be used to carry out the strengthening method, for example, a cold rolling device with rollers whose diameter is approximately equal to half the width of the component being processed, these rollers being provided with coaxially arranged circulating stops, etc.

The above-mentioned strengthening of the described type of components does not create a biaxial state of tension on their front surfaces (on a surface not exposed to external loads, the normal stress is ^n ⁼ ® ^and the tangential stress is 6^ = 0), which could lead to brittle fracture in components hardened to high hardness, and to increases in material on the front surfaces in components of low hardness (and consequently to a reduction in residual stresses and weakening of the component in this area).

The result of processing the component in the described manner is an increase in the service life of the reinforced transmission axis by 2.2 times.

Example 3

An example of the method according to the invention, used for processing a component with alternating protrusions and depressions, is shown in Fig. 3. The driven gear £ of the traction rod of a diesel locomotive with parameters: module m ~ 10 mm, number of teeth Z = 75, width of the gear rim b = 140 mm, feed coefficient of the basic profile X = 0.437, basic profile with profile angle A = 20°, with coefficients of the radius of rounding of the tool contour and height of the tooth head of 0.40 and 1.25, made of steel with a yield strength of 58 kp/mm , was subjected to sector hardening of the teeth by high-frequency currents with removal of the hardened layer.

The adjacent projections, i.e. the teeth 5, (i of the gear wheel are exposed to the simultaneous action of the following forces acting from the area of the common deepening of the teeth, i.e. the gaps between them: bending forces P^ = 300 kp/mm and the pressure of the punch 2 with a radial force P^, which causes in the area of the dangerous cross-section (located at the beginning of the effective profile) the effect of distributed forces, these forces being equal to the values of 30 kp/mm and in the area of maximum tensile stresses, located at the base of the tooth, the values of 75 kp/mm.

215,622

The adjacent projections g and I, forming adjacent depressions, are similarly processed by the cutter 2, the forces acting from the area of the common depression, i.e. the forces P^ and P£, corresponding to the values stated above.

The result of processing the component in the described manner is an increase in the load-bearing capacity of adjacent protrusions at a level not falling below the values obtained for individual protrusions, which are more than 50%.

Example 4

An example of the method according to the invention, applied to the processing of a component with a complicated profile, shown in Fig. 4, is shown.

Spur gear 4 with straight teeth that cannot be hardened, designed for drawbars o

diesel locomotives, is made of steel with a yield strength of 58 kp/mm and is manufactured on the basis of a basic profile with an angle A. = 20°, with a module m = 10 mm, a number of teeth Z = 75, a feed of the basic profile X = 0.437, a coefficient of the radius of curvature of the tooth of the basic tool profile and the height of the tooth head of 0.4 and L.25.

Along the teeth lubricated with liquid hypoid oil, a loading device 8 extends in the recess between the teeth, formed in the form of a wedge with a side angle = 10° of effective sections, in such a way that its side surfaces touch the wheel at the tops of the adjacent teeth, in the transition areas and at the base of the recess, thereby developing a normal force P^ = 600 kp/mm, distributed along the length of the gear ring, a distributed normal load with an intensity of 60 kp/mm and tangential forces ns on the contact surfaces of the wheel teeth, which are 460 kp/mm resp.

100 kp/mm.

In this case, there are no tangential forces in the radial direction and therefore the compressive force P,j does not increase, which reduces the effect of the bending force P^, which improves the state of tension of the teeth during their strengthening.

Calculations show that as a result of processing in the described manner, the residual, compressive stresses and the range in which they act increase significantly, the degree of this increase being determined primarily by the profile angle of the geometric concentrator zone and the deformation properties of the material. Thus, in the case of teeth with a profile modification of the heel, in which this angle is reduced even further, the qualitative picture of the spatial deformation of the deformations changes in principle, due to the use of tangential force along the tooth.

Example 5

An example of implementing the method according to the invention is shown on the component shown in Fig. 6. This component is a gear rack and a module m = 10 mm made of steel with a yield strength of 58 kp/mm ² with protrusions

1. The rack is compressed by cutters J, which act on its side wall with a height of h = mm in the direction of the arrows indicated in Fig. 6 with a force of 1000 kp/mm, while at the same time the punch 2 is loaded with a force P^, which develops a bending force P^ = 400 kp/mm on the protrusions i and forces distributed on the effective sections cd and ef of the profiles of the protrusions 1 with an intensity equal to 30 kp/mm ² . The protrusions 1, which are to be strengthened, lie on a compressed base, as a result of which the maximum tensile stresses o

in the area of the concentrator de they decrease by approximately 20 kp/mm and an increase in the bending force Ρ _χ is achieved. In this case, the bending stresses in the area of the effective profiles increase and the strengthening effect of the tooth profiles of the rack ee increases.

The result of processing the component in the described manner is that the component life is increased by approximately three times.

Example 6

An example of the method according to the invention is shown in the case of a distributed load (Fig. 5). The gear 4 ae is fixed immovably and on the side sb of the tooth profile 2 is loaded with a bending force P^, which induces a stress G _N on the tooth surface 5 and plastic deformation in the transition section ac in the area of the geometric concentrator. At the same time, the effective surface of the tooth 5 (in the effective section of the profile) is subjected to an additional force q, which is distributed along the profile in such a way that, together with the bending force, it induces a stress in the teeth of the gear wheel above the material proportionality limit. Before processing, the effective surfaces of the teeth are covered with a layer of molybdenum disulfide.

The result of processing in the described manner is a significant increase in the contact strength of the gear wheel and its overall load-bearing capacity. The technical and economic benefits are an increase in the service life of the wheels by a factor of several times and a reduction in dimensions by 10 to 20 56.

Example 7

An example of the method according to the invention is followed when processing components with a thin flange (Fig. _Bt 7, 8, 9). As a reinforced object, an epicyclic wheel of the final gear of a grain thresher with a module m = 4, a number of teeth Z = 69, a width of the rim b = 40 mm, a width of the rim 14.6 mm, a diameter of the bearing cylinder 0 315 + 0J205 made of normalized steel 5 with a hardness of HB = 210 of the following chemical composition: C = 0.18, Mn = 0.85, Cr = 1.1, Ti = 0.1 (in percent).

The deformation of the teeth of the wheel 2 is carried out by the weighting devices § (Fig. 8), the profile of which (ebc) is shown in Fig. 9. The deviation of the modification line bc from the apex of the tooth 5 is 0.2 mm.

According to the principle of the proposed method, the epicyclic wheel 2 is compressed with a force of 80 Mp distributed over the bearing surface (approx. 4.1 kp/mm), thereby achieving the correct shape of the bearing cylinder in the tolerance field 0 315 + ο’οοο*. The cancellation of the last value* by the effect of the mentioned force imitates the stressed-deformed state of the rim, which corresponds to the pressed bearing of the wheel 2 in the gearbox.

In three equally spaced depressions of wheels 2, the loading device 8 moves along the depression with a pull of /v 0.07, and causes plastic bending deformation of the teeth 2 with a resulting force of 10 Mp while simultaneously loading the wheel 2 with a force q = 30 .... 35 kp/mm, which is distributed over sections in the area of the dangerous cross-section (transition curves eb) and along the sides of the teeth 5. The teeth 2 are deformed along their entire length to a position that corresponds to the modified profile bc.

The same procedure is then repeated for the remaining recesses, whereby the teeth 2 are brought back to their initial position. After all the teeth of the wheel 2 have undergone the aforementioned processing, the loading device 8 is removed from the recesses, and the force distributed over the bearing surface is cancelled.

As a result of processing thin-rim components, for example gear rims, in the manner described according to the invention, an increase in the rigidity of the component is achieved at the time of hardening, thereby achieving a non-stressed-deformed state that corresponds to real operating conditions. This accurately reproduces the predetermined geometric and strength parameters of the hardened gear rim, and the load-bearing capacity of the threshing machine increases by more than 1.8 times, while the kinematic bending is reduced to a minimum.

Example 8

An example of the method according to the invention, applied to the component shown in Fig. 10, is followed. The processed component, which is the axis of the transmission device of the device for granulating mixed feeds, made of steel, and provided with one projection 1 of great length H = 158 mm at S - 34 mm, is loaded at the top of the projection 1 with a bending force P^ = 300 kp/mm, and simultaneously on the pulled side of the component with a force distributed in the area of the geometric concentrator od with an intensity q = 30 kp/mm, and on the opposite side with a force of 660 kp/mm, which acts in the area of the geometric concentrator ef and compensates in the dangerous cross-section sb the additional shear resulting from the distributed force q. The stress state of the component is thus not disturbed by the additional shear and the advantages of bending strengthening can be applied.

The technical benefit of using the method described above lies in increasing the strengthening effect and extending the service life of components with large bending force arms by approximately 1.3 times.

Example 9

An example of carrying out the method according to the invention with joint deformation by bending and twisting is followed (see Fig. 11).

The described method according to the invention processes a steel driven wheel 4 of a diesel locomotive drawbar. The wheel is made as a forging, normalized and tempered, with strength properties: hardness (HB) = 255·«.311, fracture toughness 105 kp/mm, and with geometric parameters: number of teeth Z = 75» module m » 10 mm, rim width b « 140 mm.

Processing by spatial plastic deformation by bending with simultaneous application of force, distributed in the area of the transition surfaces of the teeth, is carried out with a roller tool with a diameter of 120 mm and a technological force of 20 x 10^ kp, as well as simultaneous deformation of the entire wheel by twisting using two opposite moments (M), developed by a hydraulic power drive of 220 kp.

The result of the processing is that the load-bearing capacity of the component increases by 1.2 to 1.3 times compared to components in which only bending was used, the service life of the component increases by 6 to 10 times, and the area of application of the method expands to components of various types.

Example 10

An example of the method of strengthening a toothed koala is shown in Fig. 12, 13.

The wheel 4 is fixed immovably and the cavity of one of the recesses between the two teeth g, 6 is hermetically sealed in such a way that the surfaces abc and cde of the teeth 5 and 6, which face into the recess, as well as the front surfaces fce (Fig. 13) of the teeth near the stress accumulation area (i.e. the transition curve area) remain free. Into the closed hollow space thus formed, the

215 622 is a medium, for example a liquid, which compresses it up to such a hydrostatic pressure, the height of which is determined by the strength and geometric parameters of the reinforced component, while the compressed liquid acts on the free surfaces of the component and causes them to be loaded with a distributed force. Simultaneously with the surface loading, plastic deformation of the teeth occurs % & 6 by bending due to the bending component of the resulting force, which is exerted on each of the teeth at a unilaterally acting uniformly distributed hydrostatic pressure.

The liquid may contain adsorptive active substances, for example molybdenum disulfide.

Such strengthening is performed on two-tooth test specimens measuring 64 x 47 x 28, cut from the spur gear of the traction rod of a diesel locomotive, with straight teeth, with a module m = 11 and a number of teeth Z = 68, made of steel heat-treated to a hardness of HB = 311...255. The test specimens are milled at the mounting points, while the end surfaces are additionally ground to a size of 28 - 0.05»

The strengthening is carried out in a device adapted on the basis of a 50 megapound press, while the loading of the test specimen is carried out by a distributed normal force of the compressed medium acting on the surface surfaces of the teeth facing the recess and on the front surfaces near the area of stress accumulation, i.e. the area of the transition curves. The height of the hydrostatic pressure of the kydroplast, which was used as the compressed medium, is in this case 3.3 kbar, which leads to residual displacements of the teeth at the tops by 0.45 mm, as well as to the indentation of the material in the area of the transition curves of these teeth to a depth of 0.35 mm.

The result of processing the component in the described manner is an improvement in the strength properties, including, inter alia, the contact strength, bending strength, resistance to galling, as well as a general increase in the load-carrying capacity by 35 to 40%, simplification of the strengthening procedure of the components and expansion of the range of applications in terms of the types of components considered. The possibility of overdosing the technological forces, contributing to high stability of the strengthening, will also be improved. The use of a liquid characterized by adsorption activity, in addition, allows the creation of protective or antifriction surface layers in the components and in this way further improve the operational properties.

The examples given demonstrate that strengthening of machine components by the method according to the invention allows achieving a number of advantages over the main types of surface strengthening that are currently widespread and which consist of heat treatment or plastic surface deformation or a combination of both.

The method according to the invention does not have the disadvantages inherent in many thermal methods, such as toxicity, laboriousness and space requirements.

To clarify the essence of the invention, specific examples of the method of strengthening machine components with protrusions, working in particular with a variable load direction, are further described, namely, an example of a device for carrying out the method according to the invention, with reference to the drawings, in which Fig. 14 shows a diagram of the device in which the strengthening device according to the invention is used, Fig. 15 a cross-section of the said device in the operating position, Fig. 16 a cross-section of one of the possible variants of the device according to the invention, also in the operating position, and Fig. 17 the same cross-section as shown in Fig. 16, but in a transit rest state.

Fig. 14 shows an example of a production plant in which a gear tooth strengthening device according to the invention is used.

A reciprocating hydraulic cylinder 11 is vertically arranged on the cast stand 10, in the upper part of which a mandrel 12 with a processed gear £, indicated in the figure by a dashed line, is fixed, which is fixed with respect to the hydraulic cylinder 11 by means of a pressure bar and a nut 1£. The piston rod 1g of the hydraulic cylinder 11 is fixed to the base of the stand 10 and is formed by two concentric tubes 16 and 1j, one of which is connected to the upper and the other to the lower internal space of the hydraulic cylinder 11. Such an arrangement allows the hydraulic cylinder 11, the mandrel 12 and the processed gear £ to move reciprocatingly up and down from simultaneous rotation relative to the piston rod 15 in the direction of the arrow M indicated in the figure.

In the upper part of the stand 10, on cantilevered supports 18 on both sides of the wheel £, hydraulic cylinders lg are placed for pressing the pressure rollers 20. The pressure rollers 20 are loosely mounted on the transverse axes 11 in cylindrical bushings 21. Each of the bushings 21 is placed in ball guides 22 and is connected via a support bearing 2£ to the piston 2j of the hydraulic cylinder lg, as a result of which it can freely rotate and move forward.

The device shown in Fig. 15 is formed by a pressure roller 2g (view from Fig. 14 in the direction of arrow A), the profile of which has the shape of a protrusion in cross section, the heel of this protrusion being made as a wedge 2J>, connected to the head 26. The sides cd and c'ï of the wedge 2g are formed by the modification lines of the heads of two adjacent teeth 5 ^with É of the modified profile, which is given in advance by the parameters h,Ú A/a 2AM, which always represent the height of the modification of the profile of the protrusion head and the angle of the wedge sides, which is equal to the angle between the tangents to the modified profile of the tooth heads 2 ⁸ 6. The effective sections ab and ab of the head 26 are defined by the transition curves of the tooth profiles 2 and 6 and are connected to the sections dc and ïc of the wedge by means of the sections of the curves bc and bc*, which envelop the profile of these teeth.

The second variant of the device for strengthening machine parts with protrusions, shown in Fig. 16 and I?, represents a structure comprising a plate system formed from inner plates 2J for transferring forces from outer deforming side plates 2g and from a closing plate 2Q. Inner plates 2J are formed in the form of spring pressure elements, supported by a support 28 and arranged with guaranteed gaps K relative to each other. Side plates 2g and closing plates jO are profiled in accordance with the surface of the teeth 5 and 6 of the processed wheel £ and are supported by inner plates 22.

To connect the plate assembly to the common support 28, it is possible to use fastening members of any known type that limit axial displacements of the plates in the unloaded state.

During the strengthening process, changes in the gap size K are possible in the range 0 = K = K _m8X « where denotes the gap size in the unloaded state, while the zero value can only occur in the final position of the strip element at its greatest compression and displacement under the influence of maximum internal loads.

If the force characteristic of the spring member is known, it is possible to determine the size of the gap K nspríklsd numerically according to standard methodological procedures for springs.

If necessary, when using pressure rollers with non-linear deformation characteristics, a variant of the deformation plates in the form of disc spring members is also possible.

At the locations where the inner plates 2J are mounted on the common support 28, channels 21 for supplying lubricant are formed.

The device of Fig. 14 operates as follows. The wheel 4 to be processed is placed and fixed by means of a pressure bar 12 and a nut LJ on the mandrel 12. The pressure roller 20, shown in detail in Figs. 15 and 16, is inserted into the recess between two adjacent teeth 5 and £ of the wheel 4, after which a predetermined force is applied to it, which causes bending deformation and plastic deformation of the pressure-hardened component.

During the hardening process, the processed wheel £ undergoes a reciprocating movement together with the hydraulic cylinder 11. At the same time, the hydraulic cylinders 1g impart a certain force to the pressure rollers 20, which is determined by the conditions of the deformation of the teeth 5 and £. At the same time, the pressure rollers 20 move along the recess of the gear wheel and deform its teeth 5 and 6 to the required degree of hardening. At the end of each double stroke, the height of which exceeds the width of the gear rim, the wheel £, for example, rotates by a certain angular step, after which another pair of teeth is deformed, and so on. After all the teeth of the wheel 4 have undergone the hardening treatment, the drive of the working devices of the device is switched off, and the processed wheel is removed.

The effect of using the method according to the invention consists of the following benefits:

- increased service life,

- increasing the ability of components to transfer loads and therefore the performance and load capacity of machines, in

- reduction of the metal content and machine dimensions while maintaining the same strength,

- reduction of annual costs of not carrying out repairs.

The method according to the invention is well suited for various technological processing schemes of machine components and allows for the wide application of universal equipment. The simplicity of the method implementation guarantees the possibility of full automation and control of the production process.

Claims (12)

A method of strengthening machine parts with protrusions operating in particular and in a variable direction of operating load, which consists in plastic deformation of the protrusion material in bending and in making processing of the protrusion of the protrusion in the area of its dangerous cross-section by bending force, The reinforcement treatment of the protrusion surface in the area of its dangerous cross-section is carried out by applying a normal pressure force distributed uniformly over the surface of the projection area of the dangerous area of the projection of the component. 2. Method according to claim 1, characterized in that the strengthening of the components with the projections defining the common depression is achieved by applying the bending force and the distributed normal compressive force from the region of the common depression of the projections to opposing directions. 3. A method according to claim 2, characterized in that the bending force β divided by the normal compressive force acts on the projections along their side surfaces. 4. Method according to claims 1 to 3, characterized in that the component is in the area of the dangerous cross-section And, it compresses the projection by counter-directional compressive forces acting in a plane parallel to the plane of the dangerous cross-section, simultaneously acting with the bending force and the distributed normal printing force. 5. A method according to claim 1, characterized in that, under the action of a distributed normal compressive force and a bending force, it is compressed in its base surface until the desired widths are reached. 6. A method according to claim 1, characterized in that, simultaneously with the bending force and the distributed normal compressive force, the projection is subjected to a shear caused by a force applied at the base of the projection and in directions opposite to the direction of the distributed normal compressive force. 7. Method according to claim 1, characterized in that, simultaneously with the action of the bending force and the normal compressive force, the foot of the projection is subjected to a cruel action. 8. The method of claim 7, wherein the bending force and distributed normal compressive force is applied to the surfaces of adjacent depressions forming the depressions together and to the faces thereof by a compressed medium of low viscosity. Apparatus for carrying out the method according to items 1 to 5, in particular for machining gears, comprising pressure rollers having a cross-sectional tooth shape with a head formed by a transition curve of two adjacent teeth of the gear to be treated and a foot; gear, characterized in that each pressure roller (20) consists of inner plates (27), side plates (29) and closing plates (30) mounted on a support (28) connecting to the foot of the pressure roller (20) ), wherein the presser foot (20) is formed by inner plates (27) with side plates (29) and has a wedge (25) in cross-section whose angle (2 * 11) is equal to the angle between tangents to the modified profile of two adjacent of the toothed gear (4) being processed, and the pressure roller head (20) being formed by the closure (30). Device according to Claim 9, characterized in that the inner plates (27) are formed as resilient elements which complement each other and are supported with a gap (K) with respect to the support (28), and the side plates (29) contact these inserts (27) · Device according to claim 9 or 10, characterized in that the side plates (29) are designed as disc springs. Device according to claim 9, characterized in that the support (28) is provided with channels (31) for supplying lubricant to the insertion points of the inner plates (27).