RU2643285C1 - Method of thermomechanical hardening of articles - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: axial stretch force P_ax1 is applied to a heated shaft 1 having splined heads through split bushings 2 and having a value required only for correction of shaft curvature obtained during its heating and alignment of axes of splined heads and splined bushings 3. The spring-loaded splined bushings 3 are supplied to end face of the shaft heads 1 which have reciprocating motion n at shaft ends but do not perform axial movement. When the shaft splines and bushing are matched, the spring-loaded bushing 3 resiliently jumps onto the head, then higher force P₁ is applied thereto for complete conjugation of the splined bushings and the splined shaft heads, and then torque M_t is applied to the lower splined bushing 3 which is necessary for torsion deformation by twisting, axial force P_ax2 exceeding the value of the force P_ax1 and necessary for axial deformation of the shaft with the required elongation and a degree of deformation of 0.5-1.0% is applied to the split bushings 2. In this case, the lower split sleeves 2 move downward at a certain speed V_ax.p. on length Δl (the required shaft extension), which allows to maintain the axial tensile force at all time of twisting.

EFFECT: improvement of quality of strengthened products and stability of thermomechanical hardening process.

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Description

The invention relates to the hardening of products, mainly shafts with splined heads, and is intended for the processing of parts operating on static and cyclic torsion.

From the copyright certificate SU 406916, IPC C21D 8/00, publ. 1971, there is a known method of processing products, including their thermomechanical (low or high temperature) processing using torsional deformation, finishing machining (fine grinding, honing, etc.), surface hardening, for example, by rolling by rollers, shot blasting and cold deformation torsion (gritting). The direction of torsion deformation, both hot and cold, coincides with the application of operating stresses.

However, when processing according to the known method of lengthy products with a ratio of length to diameter of more than 8-10, the torsional deformation is unevenly distributed along the length of the part due to both the existing warpage of the original product and the warping arising from torsion of the part.

A known method of hardening products described in the copyright certificate SU 1013501, IPC C21D 8/00, publ. 1983, according to which, for hardening of products working on static and cyclic torsion, they are thermomechanically processed using torsion deformation, machining, surface hardening and cold torsion deformation. Simultaneously with torsion deformation during thermomechanical processing, axial deformation is carried out by tension with a degree of deformation of 0.5-1.0%.

The disadvantage of this method is that when an axial tensile force is applied simultaneously with torsional deformation, the material of the part is already in a plastic state from torsion, and axial deformation immediately reaches the required value of 0.5-1.0%. Further torsion occurs without elongation of the part, i.e. without tension, resulting in warpage of the part, and in some cases, uneven distribution of torsion strain along the length, which affects the quality of the product. In addition, in the description of the above method, there is no information about how axial tensile and torsional forces are applied to the part, which is not unimportant from the point of view of maintaining the shape of the finished product having spline heads.

The closest in technical essence and the achieved result, i.e. the prototype is a method of thermomechanical hardening of products, mainly shafts with splined heads, described in the copyright certificate SU 1686010, IPC C21D 8/00, publ. 1991. According to the known method, an axial tension force is applied to the heated shaft using split sleeves, after which the spline shaft heads are coupled to the spline sleeves. The coupling of the shaft heads with splined bushings is carried out, informing the latter at the same time of axial movement to the splined shaft heads and the reverse-rotational movement around its axis. In this case, the spline bushings are moved in the axial direction with a force of 5-10 kg, which is then increased by 5-10 times, and the rotational movement of the spline bushings is carried out with a frequency of torsional vibrations, determined from the expression:

where f is the frequency of torsional vibrations of the spline bushings, s ^-1 ;

s is the axial speed of the spline bushings, mm / s;

k is a coefficient equal to 0.10-0.25 mm ^-1 .

After complete coupling of the spline bushings with the spline heads of the hardened shaft, it is twisted by spline bushings with the simultaneous application of tensile forces through the fillet sections of the shaft using split bushings. The method allows for high-temperature thermomechanical treatment with torsional deformation and tension of the finished splined shafts without disturbing the shape and dimensions of the heated part.

The disadvantage of this method, adopted as a prototype, is that the application of axial tensile forces of equal magnitude when pairing spline bushings with splined shaft heads, and during torsional deformation, leads to axial deformation of the shaft to the required elongation even when pairing the shaft heads with splined bushings As a result, torsional deformation occurs practically without axial tension, which, in turn, leads to shaft warping and uneven distribution of torsional deformation along the length of the part. In addition, when the oscillating spline bushings move and when they come into contact with the end of the spline heads, a minimum force of 7-10 kg is maintained, sufficient to rotate the bushings and hit the bushings in the splines of the shaft heads, only at the initial moment when the spring supporting the sleeve is compressed with force 7-10 kg, with further movement of the splined sleeve in some cases of splines missing, this force increases sharply, which will lead to jamming of the sleeve from rotation and will interfere with the pairing of the splined sleeve and splined shaft head.

The present invention is aimed at eliminating the above disadvantages, namely, improving the quality of the products and the stability of the thermomechanical hardening process.

To solve the problem in the method of thermomechanical hardening of products, mainly shafts with splined heads, including the axial tension of the heated shaft using split sleeves, pairing the splined shaft heads with splined sleeves by communicating the last axial displacement and rotational motion around its axis, subsequent shaft deformation axial tension and torsion, according to the invention, in the process of axial tension, an axial tensile force of dressing is applied to the heated shaft, and which is necessary and sufficient to correct the curvature of the shaft after heating and alignment axes heads splined shaft and splined sleeves.

Another difference of the proposed method is that to pair the spline shaft heads with the spline bushings, spring-loaded spline bushings are first brought to the end of the shaft heads, which are told to rotate back and forth without axial movement, and the axial movement of the spline bushings begins only after the splines of the shaft heads enter the splines of the bushings and complete until the pairing of the shaft head and the sleeve.

Another difference of the claimed invention lies in the fact that during torsional deformation, the axial tension is increased to a value that ensures axial deformation of the shaft using split sleeves, which report axial displacement at a speed determined from the expression:

where V _oc.p. - the axial speed of the split sleeves during the twisting of the shaft, mm / min;

Δl is the required shaft elongation, mm;

K - shaft twisting frequency, rpm;

N is the number of revolutions of the twisting of the shaft, about.

Comparative analysis with the prototype shows that the claimed invention is distinguished by the sequence and modes of operations, as well as another condition for the operation of pairing the spline shaft heads with spline bushings, fundamentally different in magnitude of the axial force of the shaft tension when pairing the spline bushings and when the shaft is twisted, and also strictly regulated by the magnitude of the speed of movement of split sleeves in the process of torsion.

A patent search showed that it is currently unknown, a method of thermomechanical hardening of products, mainly shafts with splined heads, which has the same set of essential features as the proposed one. Thus, the claimed technical solution meets the criteria of the invention of "novelty."

When studying the level of technology known in the art, the features that distinguish the claimed invention from the prototype were not identified, and therefore they provide the claimed technical solution with the criterion of "inventive step".

Applying at the initial moment of processing to the heated shaft through split sleeves an axial tension force of the magnitude necessary and sufficient to straighten the curvature of the shaft in the elastic region, ensures the alignment of the axes of the splined bushings and the splined shaft heads. At the same time, with this small effort, premature axial plastic deformation of the shaft does not occur, which should occur only during the torsion of the shaft for uniform distribution of torsional deformation along its length.

Bringing to the end of the shaft heads of the spring-loaded spline bushings, which are first informed of the rotational motion without axial movement, provides 100% alignment of the splines of the bushings and shaft heads, as a result of which the sleeve “pops up” onto the shaft head without jamming it, and the subsequent axial the movement of the splined sleeve with the necessary force ensures its full conjugation with the shaft head.

An increase in the axial tensile force during torsional deformation provides axial plastic deformation of the shaft only during torsion.

The movement of the split sleeves through which the axial tensile force is transmitted, with a strictly regulated speed, which is determined from expression (1), allows for the presence of axial tension throughout the torsion time and, as a result, the uniform distribution of torsional deformation along the shaft length, as well as the elimination of warpage shaft in the process of torsion.

All this taken together will provide an increase in the quality of the processed products and the stability of the thermomechanical hardening process.

The above proves that the combination of features distinctive from the prototype provides the possibility of using the claimed technical solution for thermomechanical hardening of parts working on static and cyclic torsion, i.e. it meets the criteria of the invention of "industrial applicability".

The present invention is schematically illustrated by drawings, where:

- FIG. 1 shows the application of axial tensile forces to a shaft with splined heads and bringing to the ends of the heads of spring-loaded splined bushings having only a rotational motion;

- FIG. 2 - the moment of full pairing of spline bushings and spline shaft heads;

- FIG. 3 - shaft deformation by axial tension and torsion.

The inventive method of thermomechanical hardening of products, mainly shafts with splined heads, is as follows.

_An axial tensile force P _{oc1 is} applied to the heated shaft 1 through the split sleeves 2, which has the minimum level of correction necessary only to correct the curvature of the shaft obtained by heating it, and to combine the axes of the splined heads and splined sleeves 3. The axial force P _oc1 deformation of the shaft does not occur (Fig. 1).

Next, spring-loaded spline sleeves 3 are fed to the end of the shaft heads 1, which have a rotational motion n at the shaft ends, but their axial movement is absent. After one or two vibrations of the spline sleeve 3, the splines of the shaft and the sleeve are combined, and the spring-loaded sleeve 3 “pops up” onto the shaft head for a short length. Thereafter splined sleeves applied more largest force P ₁ necessary to ensure complete mating splined sleeves and splined shaft 3 heads 1 (FIG. 2).

Then, the torque Mkr necessary for torsion deformation is applied to the lower splined sleeve 3, and an axial tensile force P _{ex.2 is} exerted on the split sleeves 2, exceeding the magnitude P _oc1 and necessary for axial plastic deformation of the shaft with the required elongation and degree of deformation 0.5-1.0%. In this case, the lower split sleeves 2 move down with a certain strictly regulated speed V _oc.p. along the length Δl (necessary shaft elongation), which allows supporting the axial tensile force during the entire twisting.

This speed is V _oc.p. connected with torsion parameters and is determined from expression (1):

where V _oc.p. - the axial speed of the split sleeves during the twisting of the shaft, mm / min;

Δl is the required shaft elongation, mm;

K - shaft twisting frequency, rpm;

N is the number of revolutions of the twisting of the shaft, about.

Example.

The specific implementation of the proposed method, we consider the example of thermomechanical hardening of a shaft with spline heads, which, however, does not limit all the possibilities of the claimed invention.

First, the induction heating of the shaft 1 is carried out to a temperature of 920 ± 10 ° C. After that, the shaft is transferred to the twist position, where first, the axial force P _OS = 15 kN is applied to the fillet portions of the shaft 2, which is necessary and sufficient to correct the curvature of the shaft after heating and aligning the axes of the spline heads of the shaft 1 and the spline bushings 3 ( Fig. 1). Next, spline sleeves 3, spring-loaded with a force of 10-12 kg, are brought to the ends of the shaft heads, to which a reciprocating movement with a frequency of n = 2s ^{-1 is} reported without axial movement. In this case, for 1-2 oscillations of the splined bushings, the splines of the shaft heads and splines of the bushings are combined and the spring-loaded bushings “pop up” to a small length equal to 10-12 mm from the end of the shaft heads, after which an axial displacement force P _{1 is} applied to the splined bushings 3 = 120 kg and move them to the full interface with the spline shaft heads (Fig. 2).

Then a torque Mkr of 1800 N · m is _applied to the _{spline bushings} and the axial tensile force P _{oc2 is increased} to a value of 30 kN, sufficient for axial plastic deformation of the shaft. Next, the shaft 1 is twisted with a speed of K = 60 rpm by N = 5 revolutions, and the split sleeves 2 are moved with a speed of V _oc.p = 72 mm / min over a travel length of 6 mm equal to the shaft elongation Δl corresponding to the optimal axial deformation a shaft equal to 0.5% (Fig. 3). The speed of movement of the spline bushings is strictly regulated and is determined from the expression (1):

Studies have shown that when the speed of the split sleeves V _{oc.p is} less _than 72 mm / min, the shaft elongation Δl does not reach 6 mm and the axial deformation of the shaft does not reach its optimum value of 0.5, during the twist of the shaft by five turns % When the speed of movement of the split sleeves is greater than 72 mm / min during a five-turn shaft twist, the shaft elongation Δl will reach 6 mm earlier than the shaft twist ends and the last twist turns will occur without axial shaft tension, which leads to uneven distribution of torsion deformation along the length of the shaft.

Thus, the implementation of thermomechanical hardening of products such as shafts with spline heads operating on static and cyclic torsion, in accordance with the proposed method, provides 100% conjugation of the shaft heads and spline bushings, as well as uniform distribution of torsion strain along the shaft length, which is positive affects the quality and stability of the thermomechanical hardening process.

Claims (5)

The method of thermomechanical hardening of products, mainly shafts with splined heads, including the axial tension of a heated shaft using split sleeves, pairing of splined shaft heads with splined sleeves by communicating axial displacement and rotational motion around its axis to the sleeves, subsequent shaft deformation by axial tension and torsion, characterized in that in the process of axial tension, an axial tensile force of dressing is applied to the heated shaft, the value of which provides correction the curvature of the shaft after heating and alignment of the axes of the splined shaft heads and splined bushings, in order to pair the splined shaft heads with splined bushings, spring-loaded splined bushings are first brought to the end of the shaft heads to which a reciprocating rotational movement without axial movement is reported, and their axial movement begins after the splines of the shaft heads fall into the splines of the bushings and complete until the shaft head and the bush are fully mated, and when torsionally deformed, the axial tension is increased to a value that provides axial formation of the shaft, using split sleeves, which reported an axial movement at a rate determined by the formula:

where Δl is the required shaft elongation, mm; K - shaft twisting frequency, rpm; N is the number of revolutions of the twisting of the shaft, about.

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