RU2570252C1 - Method to cool parts in process of thermal processing and sprayer for part cooling - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention relates to the field of thermal processing, in particular, to tempering of machine parts and rolling bearings mechanisms. For efficiency of cooling and increase of process efficiency, the part in the form of a solid of revolution is cooled by supply of cooling liquids in jets onto outer surface with provision of rotary and reciprocal motion by means of a sprayer. The sprayer comprises a body with a canal for passage of parts and a facility to guide cooling liquid to outer surface of parts. The facility to guide cooling liquid is made in the form of inserts arranged symmetrically relative to the axis of the sprayer body channel, at the same time inserts have openings for supply of cooling liquid jets, passing via chords of imagined circumferences of cooled part outer surface with provision of rotary motion of parts in a layer of cooling liquid, besides, the sprayer is installed in the reservoir with the running cooling liquid.

EFFECT: increased efficiency of cooling and increased process efficiency.

8 cl, 3 dwg

Description

The invention relates to mechanical engineering, more specifically to hardening of metals, and can be used for heat treatment, in particular hardening of machine parts and mechanisms operated in various fields of technology, for example, in the production of rolling bearings and processing of parts in the form of bodies of revolution, in particular spherical .

There is a method of hardening parts in the form of bodies of revolution, in which the parts heated to the quenching temperature are cooled by jets of coolant supplied from the sprayer during rotation of the hardened parts using rotating rolls (see, for example, copyright certificate SU 231590, 1967).

The disadvantage of this method and the sprayer is that when it is used it is difficult to ensure the simultaneous start of rotation of the parts on the rolls and the supply of cooling water jets to the parts. This non-simultaneity of the beginning of rotation and intensive cooling by liquid leads to a decrease in the uniformity of cooling, the quality of quenching and an increase in energy intensity. In addition, with this method, sprayer jets cool parts only on one side, since the rolls are located on the other side, which also creates uneven cooling. The fact that with this method the supply of jets of coolant is carried out in air leads to air entering certain parts of the surface of the cooled parts and this leads to the appearance of additional uneven cooling and a decrease in the quality of quenching.

Limits the possibility of improving the quality of hardening and the fact that with an increase in the speed of rotation of the rolls and parts above a certain value, the centrifugal forces, which inevitably increase in this case, reach such a value that due to these forces the coolant is discarded from the rolls and hardened parts, and, Thus, a further increase in the speed of rotation of the rolls and parts gives not a decrease in the uniformity and quality of cooling, but a decrease.

All these disadvantages do not allow to achieve in the known method a better and more productive hardening, although its implementation requires a rather complicated system of rotatable rolls with a drive.

A known device for hardening parts containing a pipe equipped with a collector installed inside it with nozzles located tangentially to the inner surface (see copyright certificate SU 881135 A1, 1977).

Also known is a sprayer used for cooling parts, comprising a housing, perforated inserts forming an annular cavity with a housing, a guide cone, a channel for passing parts, a means for supplying liquid and a drain manifold, the operation of which implements a method of cooling parts during heat treatment (see copyright certificate SU 378428 A1, 1973).

This well-known sprayer designed for cooling parts has the disadvantage that it is impossible to create conditions in it to increase the uniformity and intensity of mass transfer of the surface of the parts and improve the quality of their hardening due to the fact that uncontrolled chaotic unevenness of hydraulic pressure on the part is created in the sprayer in the channel for passing parts and fluid flow rates, affecting the translational of individual surface sections of parts, which, in turn, leads to a decrease in uniformity hardening of the entire surface of the parts, i.e. the quality of their hardening in general.

Due to the insufficient cooling intensity and the impossibility of increasing it, the throughput of the device, the efficiency of the method and the productivity of the method and sprayer are limited.

The technical result that is achieved by the invention in terms of a sprayer and a method of cooling parts is to eliminate and mitigate these drawbacks and to increase the cooling efficiency and productivity of the cooling process and heat treatment in general.

The specified technical result is achieved due to the fact that in the device for cooling parts, made in the form of a sprayer, conditions are created to increase the uniformity and intensity of mass transfer of liquid to the surface of the parts and improve the quality of their processing, as well as the conditions for increasing throughput - productivity. The jet supply of coolant is carried out in the directions of the chords of the cross sections of the outer surfaces of the parts symmetrical about the axis of rotation of the cooled parts, and the coolant jets themselves cause the cooled parts to rotate due to their kinetic energy. The jet supply of coolant and the entire cooling process lead to a thicker layer of this fluid.

In the sprayer for cooling parts in the form of bodies of revolution during the heat treatment, comprising a housing with a channel for passing parts and means for directing the coolant to the outer surface of the parts, means for guiding the coolant is made in the form of inserts located symmetrically with respect to the axis of the channel of the sprayer body, wherein the inserts have openings for supplying jets of coolant passing through the chords of imaginary circles of the outer surface of the cooled part, with the rotational movement of the parts in the coolant layer, the sprayer being installed in a container with flowing coolant.

The means for directing the coolant to the part is made in the form of at least two inserts with holes located in the housing.

The channel for the passage of parts in the housing from the supply side is conical, while the larger diameter of the channel is made from the supply side of the parts.

The means for guiding the coolant to the parts in the form of inserts is an even number, and to ensure the translational movement of the parts in the inserts are made at an acute angle to the oblique holes forming them.

The inserts are evenly spaced around a circle whose center coincides with the center of the housing opening.

The housing contains a sealed annular cavity coaxial with its channel and communicated with the coolant supply device, and each insert has a sealed cavity communicated with the annular cavity of the housing and insert holes, the inserts being rigidly connected to the housing on one side and mounted in a circumferential circumferential the housing channel, and the other side - they are fastened together by a shank.

Each insert is equipped with a wear-resistant pad located on the side of the cooled parts.

In the method of cooling parts in the form of bodies of revolution in the heat treatment process, including the supply of coolant in jets to the outer surface of the parts by means of a sprayer, use the sprayer according to any one of paragraphs. 1-7, while the parts are imparted a rotational movement directly in the coolant layer.

The jets of coolant impart translational movement to the parts in the direction of the axis of rotation.

The parts are immersed in a coolant and cooled by means of a sprayer made as described above.

To ensure ejection by means of a jet, a region with reduced pressure is created between the surface of the jet and the surface of the inserts or wear-resistant linings.

Perforated inserts are made with holes that are directed along the chords of circles inscribed in the section of the channel for passing parts, and are located symmetrically to its axis and at least grouped in pairs, and depending on the angular position of the direction of the holes of the perforation of the inserts, they are given axial displacement to the part the step of placing these holes on the perforated insert. Perforated inserts on the channel side for the passage of parts are provided with wear-resistant abrasion pads. Providing the sprayer with a number of coolant-supplying perforated inserts, which are perforated on one side, are evenly spaced with gaps and form a channel for the passage of parts, creates conditions for the orderly movement of coolant flows in the channel near the quenched parts and attenuates the influence of local uncontrolled chaotic irregularities hydraulic pressures and speeds, which, ultimately, creates the conditions for increasing the uniformity and intensity of mass transfer dkosti on the surface and improve the cooling quality, and increase the capacity and performance of the device - the sprayer.

The implementation of inserts with holes that are directed along the chords of circles inscribed in the cross section of the channel for passing parts with their location symmetrically to the axis of this channel, provides an ordered radial tangential fluid flow to the parts, the radial components of hydraulic forces from which are mutually compensated, and the predominant paired tangential components create a torque that causes the cooled parts to rotate, while the liquid supplied to the parts itself acquires a unidirectional rotation ovoe twist around the parts, thereby increasing the uniformity and intensity of cooling, improve the quality of quenching and increase productivity. The grouping of perforated inserts depending on the angular position of the holes of the inserts and giving them an axial displacement by a part of the pitch of the arrangement of these holes on the perforated insert also contributes to streamlining the fluid supply and creating conditions for increasing the uniformity and intensity of mass transfer of liquid on the surface of the parts and improving the quality of their quenching, as well as improving device performance.

Abrasion-resistant linings on the channel side for the passage of parts, a constant gap between the parts and the surface of the housing opening formed by the plates, increase the intensity of the fluid supply and its mass transfer on the surface of the parts, and therefore, improve the quality and increase the quenching performance without fear for reducing the service life of this device or for violation of its performance.

In Fig.1 shows a General view of the proposed sprayer in a section along its axial plane, Fig.2 shows a view along aa in Fig.1 with an additional partial local cutaway, Fig.3 shows a view along BB in Fig.1 .

The sprayer has a housing 1 in which a guide cone 2 is made, a cover 3 with a nozzle 4 connected to a fluid supply device not shown in the drawing. The housing 1 with the indicated mating parts with it has an annular cavity 5 for supplying coolant. The sprayer has a means for directing the coolant to the outer surface of the parts, containing, in particular, four perforated inserts 6 (see also FIG. 2), which are perforated on one side only, rigidly connected to the housing and placed with gaps uniformly around the circumference of the axis annular cavity 5 for coolant. Each insert is connected to the housing by means of a ring, studs 8 installed in sockets 7, which are made in inserts and rings. The inserts are connected by means of bolts not shown in the drawing, located in the spaces between the perforated inserts 6, and using four sealing gaskets 9, rigidly connected to the annular cavity 5 for supplying fluid. Other free ends of the perforated inserts 6 by means of a shank with sockets 10, four other studs 8, four plugs 11, washers 12, 13, nuts 14 using the other four gaskets 9 are muffled and fastened together so that between the four perforated inserts 6 on their entire a channel 15 is formed for the passage of parts 16, which, through slotted gaps between the inserts 6, communicates with the external space. The holes 17 in the perforated inserts 6 are made so that in the assembly they are directed (as can be seen from figure 2) along imaginary chords inscribed in the cross section of the channel 15 for passing parts 16 of circles or circles of the outer surface of the cooled part. They have a mutual arrangement symmetrical to its axis in the sprayer. On both sides of the holes 17 there are oblique holes 18 made at an acute angle to the generatrix of the insert 6 and directed to the side along the parts 16 (see also FIG. 3). The perforated inserts 6 are grouped in pairs and in FIG. 2 it can be seen that in the section shown here along AA in FIG. 1. perforation holes 17 are located and are visible only in two perforated inserts 6 symmetrically positioned relative to the axis of the channel 15, having the same angular location between each other and parallel to the position of the perforation holes 17, in the other two symmetrical to the axis of the perforated inserts 6, having a different angular position of their perforation holes due to their simultaneous with the angular group axial displacement by half the pitch of the holes of the perforated inserts 6. These holes did not fall into the section along AA in FIG. 2. The perforated inserts 6 on the side of the channel 15 for passing parts 16 are provided with abrasion-resistant plates 19, for example, made of hard alloy, which are glued to them or brazed in a known manner along plane 20, or are fixed in any other way so that they face towards the channel 15 for the passage of parts 16, their surface rises above the output side of the holes 17 and 18.

For operation, the sprayer is placed in a container, not shown in the drawings, containing coolant, so immersed in the liquid that all holes 17 and 18 of the inserts 6 are in the liquid layer near its surface. From this tank, the liquid is drained while maintaining its level.

From an external device not shown in the drawing, a coolant is supplied to the sprayer through its nozzle 4 in the direction of arrow 21. When coolant is supplied to the sprayer in the channel 15 for the passage of parts 16, its orderly directed movement is created in the form of jets 22, which, due to their group displacement by a part of the step, do not interfere with each other and also entail the adjacent fluid located near them in a liquid layer in the channel 16, as well as near this channel. In particular, due to the entrainment of the fluid located in the vicinity of the inserts 6 and the fluid channel 16, which flows in the form of jets 22, a jet axial flow along the channel 15 also creates a liquid suction from its upper layers in the tank and liquid together with air from the upper layers. The removal of coolant from the channel 15 occurs through the slit gaps between the inserts 6. The parts 16 heated to the quenching temperature are supplied along the arrow 23 through the guide cone 2 to the channel 15.

By the action of liquid jets emerging from the oblique holes 18 located at the top of the part 16, they are quickly introduced into the liquid layer into the zone of the jets 22 emerging from the holes 17, which uniformly and intensively cool the parts 16, and at the same time bring these parts into rotation with their kinetic energy high speed of the order of 20-30 thousand rpm in the direction of the arrow 24, which also helps to increase the uniformity of cooling and its intensity. During their rotation during the cooling process, the parts 16 rely on the abrasion-resistant linings 19, but the clamping of the parts to them is determined only by the difference in the mutually compensated radial components of the hydraulic forces and due to the fact that their surfaces facing the channel 15 rise above the outlet side of the holes 17 and 18. The latter, on the one hand, cannot be blocked by the parts themselves, and, on the other hand, they are not covered by wear-resistant plates from abrasion of the surface of the inserts 6. Axial jet suction a cooling liquid from below supports part 16 by this suction in channel 15 in the area of holes 17 of perforated inserts 6 and is cooled here until subsequent parts 16 coming into this zone from above displace the previous part into the zone of lower oblique holes 18, from where it acts 18 oblique jets emerging from these openings are finally pushed out of the intensive cooling zone.

As can be seen from the description of the specific case of the method, when it is used, an increase in the uniformity and intensity of cooling, and therefore, the quality of quenching and productivity, is achieved, since with the proposed method:

- provided the simultaneity of the beginning of rotation of the part and the beginning of its jet cooling;

- cooling jets enter hardened (cooled) parts from all sides symmetrically with respect to their axis and provide more uniform washing of parts and with greater speed and total coolant supply;

- excluded the possibility of air entering the surface of the cooled parts during hardening;

- achieved significantly higher speeds of rotation of parts, uniformity and intensity of their cooling.

This, in turn, indicates the achievement of the goal. Moreover, the device is simpler and more efficient.

It can be seen from the description that the sprayer has a number of perforated inserts supplying the cooling liquid, which are uniformly spaced around the gap and form a channel 15 for the passage of parts 16, creates conditions for streamlining coolant flows near the surface of the quenched parts 16 and increasing uniformity and intensity mass transfer to their surface and uniformity of cooling and hardening quality and increase the productivity of the device and method.

The fact that the perforated inserts 6 are made with holes 17 directed along the chords of the circles inscribed in the cross section of the channel 15 for passing parts 16, and are located symmetrically to its axis and that they are at least grouped in pairs and depending on the angular position of the direction of the holes 17 perforated inserts 6 they are given a group axial displacement by part of the pitch of the arrangement of these holes 17 on the insert 6, also helps to increase the uniformity and intensity of mass transfer of fluid on the surface of the parts 16 and the quality of their quenching and device performance.

Finally, the presence on the perforated inserts 6 of abrasion-resistant pads 19 with their described design also creates conditions for increasing the flow rate of the coolant and its mass transfer on the surface of the parts 16, and therefore, improving the quality and productivity of the device without fear of reducing its service life or violation its performance.

To prove the feasibility and usefulness of the proposed technical solution, the following reasoning and evaluative calculations should be given.

It is known that according to the law of thermal conductivity of materials, including steel as the material from which hardened parts are made, the specific heat flux of thermal conductivity for flat surfaces (an elementary section of any part can be considered as flat) is expressed as follows:

where q is the specific heat flux, kcal / m ² hour;

λ is the coefficient of thermal conductivity, kcal / m ² hour ° C;

dt / dn is the vector that coincides with the direction of the largest temperature increase, ° C / m-temperature gradient (See, for example, "Machine Builder's Guide", v.11, Mashgiz, M., 1951, p. 476).

The thermal conductivity coefficient of carbon steel, for example, steels in the temperature range 100 ÷ 700 ° C is in the approximate range of 25 ÷ 47 kcal / m hour ° C (see also p. 489).

Considering the approximate validity of the specific heat flux given by expression (1) for finite temperature increments Δt and layer thickness Δn in a material with a temperature difference Δt (which for small Δn is fairly accurate even for large Δt), we write expression (I) in the form :

where q and λ correspond to the notation of expression (I);

Δt is the final temperature difference in the layer thickness; ° C;

Δn - final, but small thickness of the material layer, m

If we take into account that 1 kcal = 4187 W / s and 1 hour = 3600 s, then the thermal conductivity of steel λ _st and the specific heat flux q _{Pow. article} in its cooled surface layer during the course of this cooling, on the basis of expression (2) we can write in the form:

q _{rep. st} - specific heat flux in the surface layer of the steel part near the cooled surface, W / m ² ;

λ _st = (25 ÷ 45) · 4187/3600 = 29 ÷ 55 - coefficient of thermal conductivity of steel, W / m ° C;

Δt is the temperature difference from quenching to final in the surface layer with a thickness of Δn, ° C;

Δn is the thickness of the layer on the surface of the part, within which, at the moment, during the cooling process, a temperature difference is created from quenching to final, m.

Defined by the expression (3) specific heat flux q _{POV. Article} in the surface layer of the cooled steel part is nothing but the density of power given by the part from the inside through its surface layer to its surface due to the energy stored in the part, expressed in W / m ² .

If the task is to ensure the hardening of parts with a depth of the surface layer with partial tempering structures such as reed, reed marten, etc., by no more than some acceptable value Δn _d , then this means that, starting from cooling to this depth, subsequent cooling in the nearest after this point in time should be capable of not less but the same or greater power from the surface.

In this case, the cooled layer located deeper than it will not be able to undergo reheating from the inside, due to the accumulated energy in the part due to the lack of external power take-off and the risk of layer release with the appearance of other structures will no longer arise.

Let us first evaluate the practical order of magnitude of this power density given to the surface of the part, starting, for example, by cooling the surface itself to a final temperature of 20 ° C, when the initial quenching temperature, for example 900 ° C, is, say, at a depth

Δn _d = 0.01 mm = 10 ^-5 m.

The power density on the surface for this will be:

It should be emphasized here that the magnitude of this power density is quite impressive, it exceeds, for example, the power density invested in almost many cases when induction heating parts for hardening by hundreds or thousands of times.

We turn now to the means of cooling the surface of the part. It is the means of cooling the surface of the part that should be able to take power from the surface of the part, the density of which we have defined above as the power that the part gives out to its surface.

When used as a coolant, for example, water, we take into account that bringing its temperature from zero to 100 ° C and subsequent transition to a vapor state occurs with the absorption of heat content i = 639.2 kcal / kg or 639.2 kcal / dm ^{3 of} source water (see pages 440-441).

Considering that cooling water has its own positive initial temperature, and converting the heat content from kcal / dm ³ to W · sec / m ³ , we limit the used increment of heat content, which can at most be reported to cooling water, to 600 kcal / dm ³ or

where Δi _isp - the maximum used increment of heat content, reported cooling water when it is used for quenching, W · sec / m ³ .

Dividing the power density, to give details of the surface q _{Stand. article} (3), the maximum effective increment of the heat content of cooling water (5) can be obtained necessary effective intensity of water supply v _eff.

where: v _eff. - effective intensity of water supply, m / s;

q _{rep. st} is the specific heat flux in the surface layer or the power density given by the part from the inside to the surface, W / m ² ;

Δi _isp is the maximum used increment of the heat content of cooling water when it is used for quenching W · sec / m ³ ;

λ _st - the coefficient of thermal conductivity of steel, W / m ° C;

Δt is the temperature difference from quenching to final in the surface layer, ° C;

Δn _d - the permissible depth of the layer with different etched structures after quenching, m

In order to determine the necessary averaged speed of the water supply jets on the parts v _page, an effective water supply intensity v _{eff is} necessary _. multiply by the ratio of the areas of the cooled surface of the part to the cross-sectional area of the jets falling on this area, i.e. multiply expression (6) by S _rep. / S _p

where v _p. - the speed of the supplied water in the jets, m / s;

S _pov. , S _p - the area respectively of the surface to be cooled and the cross section of the cooling jets falling on this surface, m ² .

Now consider one example, in which we take as input:

D is the diameter of the cooled parts 16, D = 16 mm;

d is the diameter of the jets 22, equal to the diameter of the holes 17 of the inserts 6, d = 2 mm;

t _holes -. Step arrangement of holes 17 in the inserts 6, t = 2d = _holes 4mm.

. For this case, given that the section parts a length equal to t step _holes, there are four plane, we can write:

S _pov. / S _p = πD t ./(4πd _holes ^2/4) = 2D / d = 2 * 16/2 = 16,

and now, in accordance with expression (7), for the case considered above, we determine the velocity of the supplied water in jets under the conditions:

Δn _d = 10 ^-5 , Δt = 880 ° C, λ _st = 29 ÷ 55 W / m ° C, Δi _isp = 25 · 10 ⁸ W · s / m ³

v _p = _{-. (.} S _dressing / S _p) · (λ _v · Δt / Δi _d · Δn _es) = - 16 + (29 ÷ 55) · 880) / 25 × 10 ⁸ × 10 ^-5 =

= (16.3 ÷ 31) m / s.

The estimated analysis, despite the fact that simplifying assumptions were made during its implementation, on the basis of an approximate quantitative assessment of the occurring physical phenomena, reveals the influence on the cooling process of individual parameters and determines the practical order of magnitude of these parameters, and also clearly shows the relevance of the problem posed in the application.

The range of speed obtained, for example, in the last calculation, in the streams of supplied water, taking into account their relatively dense direction to the surface of the parts, corresponds to a rather high cooling intensity. This and higher intensities and at the same time with uniformity are achievable in the proposed method and device due to their distinctive features.

Claims (8)

1. A sprayer for cooling parts in the form of bodies of revolution during heat treatment, comprising a housing with a channel for passing parts and means for directing coolant to the outer surface of the parts, characterized in that the means for guiding the coolant is made in the form of inserts arranged symmetrically with respect to the axis of the channel of the sprayer body, while the inserts have holes for supplying jets of coolant passing through the chords of imaginary circles of the outer surface of the cooled details providing rotational movement of parts in the coolant layer, the sprayer being installed in a tank with flowing coolant. 2. The sprayer according to claim 1, characterized in that the means for directing the coolant to the part is made in the form of at least two inserts with holes located in the housing. 3. The sprayer according to claim 1, characterized in that the channel for the passage of parts in the housing from the supply side is conical, while a larger hole diameter is located on the supply side of the parts. 4. The sprayer according to claim 1, characterized in that the means for guiding the coolant to the parts in the form of inserts is an even number, and to ensure the translational movement of the parts in the inserts are made at an acute angle to their oblique forming holes. 5. The sprayer according to claim 2 or 3, characterized in that the inserts are evenly spaced around a circle whose center coincides with the center of the housing opening. 6. The sprayer according to claim 1, characterized in that the housing contains a sealed annular cavity, coaxial to its channel and in communication with the device for supplying coolant, and each insert has a sealed cavity communicated with the annular cavity of the housing and insert holes, the insert being one side rigidly connected to the housing and installed in it around the circumference, coaxial to the channel of the housing, and the other side they are fastened together by a shank. 7. The sprayer according to claim 1, characterized in that each insert is equipped with a wear-resistant pad located on the side of the part to be cooled.      8. The method of cooling parts in the form of bodies of revolution in the heat treatment process, comprising supplying coolant in jets to the outer surface of the parts by means of a sprayer, characterized in that they use the sprayer according to any one of claims 1 to 7, while the parts are imparted a rotational movement directly in the layer coolant.

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