RU2778315C1 - Prefabricated drawing tool - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to the production of wire on multiple drawing tools. The drawing tool contains pressure and working draw rings sequentially clamped in the housing and sealing ring-shaped gaskets located between the draw rings. An additional sealing die is placed in front of the first pressure draw ring. Pressure dies form pressure gaps with the workpiece, providing a lubrication pressure that reaches the value of the deformation resistance of the workpiece metal before the first working die. The last pressure die forms a pressure gap with the workpiece, the value of which is 1.5 times the thickness of the lubricating layer in the final working die. The first pressure die forms a pressure gap with the workpiece, providing an initial lubrication pressure of 14.7 MPa. Sealing ring-shaped gaskets are placed in the free part of the grooves of the mandrels, in which the dies are pressed.

EFFECT: as a result, the drawing effort is reduced, the wear resistance of the working dies is increased and the manufacture and assembly of the tool is simplified.

6 cl, 3 dwg, 1 tbl

Description

The invention relates to the production of wire in hardware redistribution, in particular to a technological tool for multiple mills, and mainly direct-flow drawing.

A device is known for creating conditions for hydrodynamic friction during drawing [Kolmogorov V.L., Orlov S.I., Kolmogorov G.L. Hydrodynamic lubrication. - M.: Metallurgy, 1975, 256 p., p. 14-16], which includes a working die and a pressure tube hermetically installed at its inlet, which forms a narrow gap with the drawn workpiece. The device allows, thanks to the viscous forces acting in the gap, to create a process lubricant pressure at the inlet to the working die, commensurate with the yield strength of the workpiece material.

Designs of drawing dies with pressure tubes-nozzles have significant drawbacks - the instability of work and the complexity of manufacturing. It is known that if the lubricant is represented as a linearly viscous liquid [S.A. Kuznetsov, E.A. Garber, M.Ya. Brovman, S.Yu. Semenov, A.I. Vinogradov. Simulation of the flow of ideally viscous lubricant in the pressure gaps of a drawing tool. // Sat. Proceedings of the International Conference "Information Technologies in Industrial, Social and Economic Processes", Cherepovets, ChSU Publishing House, 1999. p. 101-103], the rise in pressure Ap created by the pressure tube is expressed by the formula

where μ is the effective (reduced to a linear fluid model) lubricant viscosity;

ν ₀ - the speed of drawing the workpiece;

- длина трубки;

- tube length;

δ - gap width;

δ _p is the thickness of the lubricant layer in the working die.

Thus, the pressure created by the pressure tube is proportional to its length and inversely proportional to the square of the width of the gap. The maximum degree of pressure increase along the length of the nozzle tube occurs at a gap thickness equal to 3/2 of the thickness of the lubricant layer in the working die. Even in the liquid mode of injection of lubricant and friction in the deformation zone in the working die, the width of such a gap is measured in tens of micrometers (hundredths of a millimeter).

The hydrodynamic regime in such a gap turns out to be very sensitive to an increase in its width due to wear, which always occurs due to fatal misalignments and curvature of the incoming workpiece, as well as due to random changes in its diameter within the tolerance field. For example, expanding the gap from 0.03 to 0.045 mm causes the pressure created by the tube to drop by more than half. Qualitatively, this regularity is also valid for real lubricants.

To significantly reduce the negative effect of gap wall wear, it has to be significantly increased, for example, by an order of magnitude, but this, in turn, leads to an increase in the length of the nozzle tube by two orders of magnitude. The manufacture of pressure pipes of great length from a hard, wear-resistant material, with the exact dimensions of the inner hole, is too difficult a task.

Known "Device for drawing products in the mode of hydrodynamic friction" [USSR patent No. 1804354, MKI V21S 3/14, publ. 1993, Bulletin No. 11], consisting of a body, several pressure resilient bushings and a working die, installed in the body and tightened with a union nut. During the movement of the drawn product, the lubricant is injected under pressure into the deformation zone, providing conditions for hydrodynamic friction. In this case, each of the pressure bushings provides a certain increase in pressure in the lubricant layer. In each of the cavities formed by the pressure bushings, a circulating lubricant flow is formed, which contributes to the removal of exfoliating metal particles to the peripheral regions of the lubricating cavities.

The disadvantage of this device is the instability of the hydrodynamic regime of the lubricant flow and the creation of the necessary pressure, due to the rapid wear of the elastic bushings for the same reasons.

Indeed, since the pressure bushings are resilient, they cannot be sufficiently hard and rigid to successfully resist wear. When the bushings are worn, the forces of their pressing against the product are reduced, and, accordingly, the resulting hydrodynamic gaps increase.

In addition, the distillation of exfoliating metal particles into the peripheral regions of the lubrication cavities can occur in any prefabricated die, since such cavities exist there. In addition, lubricants are usually quite viscous, and the metal particles that cause increased wear are small, and they move with the lubricant flow and wear out the gaps, expanding them.

Known "Technological tool for drawing products in the mode of hydrodynamic friction" [A.S. USSR No. 1468630, MKI V21C 3/14, publ. 30.03.89, bull. No. 12], containing a body with a taper bushing pressed into it, a pressure and working die installed in the bushing and a sealing element placed between them, made in the form of shaped rings connected through a groove-protrusion to form an internal cavity and installed with the possibility of relative axial displacement. The pressure die is designed to provide the working die with the pressure necessary to implement the hydrodynamic friction mode in the drawing process.

The use of a standard die as a pressure die makes it possible to combine a small hydrodynamic gap with high wear resistance, since the die dies are made of special high-hard materials. The technology of their manufacture is sufficiently developed in the drawing industry. The resulting pressure in the cavity between the dies leads to a tight fit of the rings to the dies, which contributes to successful sealing.

The disadvantage of this device is the insufficiency of the lubricant pressure created in the gap of a single pressure die to significantly reduce the drawing force and reduce the wear of the working die.

The gap length required to increase the pressure Δр at its optimal width (3/2) _δр is determined by the formula

и более, что примерно соответствует обычной длине калибрующего пояска фильеры.If we accept the optimal thickness of the lubricant layer in the working die δ _p \u003d 0.02 mm, (pressure gap δ \u003d 0.03 mm), take the speed of drawing the workpiece ν ₀ \u003d 3 m / s, then when using a lubricant in the form of a dry powder based on sodium stearate (laundry soap), when the effective viscosity at operating temperatures of about 100°C is within μ=8…30 Pa⋅s, the required gap length will be

and more, which approximately corresponds to the usual length of the sizing band of the die.

However, the pressure clearance δ=0.03 mm is very small, and it is necessary to ensure the supply of lubricant to the working die in sufficient quantities, because only under this condition can the necessary pressure develop.

The density of a dry powdered lubricant is much (several times) less than the density of solid soap, so the pressure die must provide lubricant supply in a volume that exceeds the calculated one by the same number of times, while the air in the pores, when the lubricant is compacted in the gap, can only escape in the opposite direction. direction, making it difficult to feed. In addition, the effective viscosity of a loose lubricant is much lower than a solid one, which will also make it difficult for the lubricant to be captured and pumped by viscous friction forces.

и более.For liquid lubricants, one of the most viscous of which is, for example, cylinder oil, which at the same temperatures has a viscosity of μ=0.03 Pa⋅s, i.e. a thousand times lower, the required tube length will be already

and more.

Consistent composite lubricants occupy an intermediate position in terms of effective viscosity, and the length of the sizing belt of the die to create sufficient lubricant pressure is also not enough.

Another disadvantage is the unreliable sealing of the sealing element, since there are no means to prevent the lubricant from entering butt-to-butt between the rings and the die, especially at the beginning of the drawing process, when the lubricant pressure is not yet high and insufficient to push the rings apart, and after the lubricant gets there, the seal becomes inoperable.

It is also known "Device for drawing in the mode of hydrodynamic friction" [A.S. USSR No. 1360839, MKI V21C 3/14, publ. 23.12.87, bulletin No. 47], containing a body with a split conical clamping sleeve installed in it, in which the pressure and working drawing dies are clamped in it with a union nut and equipped with thermal compensation washers. The use of a standard die as a pressure die here also makes it possible to combine a small gap with its high wear resistance. The resulting pressure in the cavity between the dies leads to the deformation of the washers and their tight fit to the dies, which prevents the breakthrough and ejection of lubricant.

This known device has the same disadvantages as the previous analogue. In addition, an additional disadvantage of the known tool is the presence of a cut in the conical clamping sleeve, which increases the likelihood of lubricant breakthrough from the cavity between the dies, for example, when excessive deformation and extrusion of the most plastic material of the washers into the sleeve cut due to lubricant pressure.

Also known "Tool for drawing" [A.S. USSR No. 1810153, MKI V21S 3/14, publ. 04/23/93, bull. No. 15], including pressure and working draw with a sealing washer located between them, installed in a bushing made continuous. Thanks to the latter feature, the tool excludes the extrusion of the sealing seal into the cut of the sleeve, and therefore the breakthrough between the lubricant dies.

The disadvantage of this known device, similarly to the previous two, is the lack of lubrication pressure created with just one pressure die.

Another disadvantage is the absence in the design of the sealing washer of elements that provide self-sealing under the action of lubricant pressure, which determines the possibility of lubricant breakthrough due to bypassing the sealing washer, especially at the beginning of the drawing process, when the hydrodynamic mechanism is just beginning to operate.

Known and "Device for drawing in the mode of hydrodynamic friction" [A.S. USSR No. 1752467, MKI V21C 3/14, publ. 08/07/92, bulletin No. 29], including a body, working dies, pressed into cylindrical split bushings, placed in a body with a radial clearance.

In addition to the shortcomings noted for previous analogues, the device does not have any seals between the dies, which determines the possibility of depressurization of the internal space of the housing and the exclusion of the pressure effect.

Also known is the "Tool for drawing" [A.S. USSR No. 1687321, MKI V21C 3/14, publ. 30.10.91, bull. No. 40], containing a pressure die and two working dies clamped in the body, including the corresponding dies, pressed into separate continuous steel mandrels, and sealing gaskets placed between the dies, while the microroughness of the channel of the second working die is made 4-13.7 times less than the microroughness channel of the first working die.

The design of the pressure die and working die, pressed into separate continuous steel mandrels, makes it possible to use in this capacity a standard drawing tool, which is a die made of a hard, wear-resistant material, for example, sintered tungsten carbide cemented with cobalt, pressed into separate steel continuous mandrels, which significantly reduces the cost of construction.

The first disadvantage of this known drawing tool is the absence in the design of the sealing gasket of elements that ensure its self-sealing under the action of lubricant pressure forces, which determines the possibility of lubricant breakthrough bypassing the sealing gasket.

The second drawback of this well-known tool is the lack of lubrication pressure created in the hydrodynamic gap of a single pressure drawing die to significantly reduce the drawing force and wear of the first working die.

In the example given in this analogue, the drawing was carried out with a relatively small reduction of 3.7%. This total reduction must be distributed between the working dies so that the main part of it falls on the second die, otherwise the drawing will become impossible due to breaks from excessive counter-tension for the second working die. But with too little compression in the first working die, a very unfavorable drawing mode is realized, characterized by significant contact stresses between the wire and the surface of the die channel, which, according to the plasticity condition, are equal to the difference between the resistance of the metal to deformation and the axial tensile stress of the wire in the deformation zone of the first die. But in this zone, the axial tension, which varies from the value of the counter-tension (if any) to the stress of drawing through the first working die (with a very small reduction), is minimal, and, consequently, the contact stress, or the stress of the radial compression of the wire, is large and close to the limit metal fluidity. For this reason, drawing with very small reductions is not advisable, in particular, due to the increased wear of the dies and the relatively high energy consumption for friction. Therefore, the most intense wear of the conical channel of the die is observed near the place of its primary contact with the surface of the workpiece (near the zone of maximum elastic deformations) [Perlin I.L., Ermanok M.Z. Drawing theory - M.: Metallurgy, 1971, p. 26-39; 110; 142-144, 202].

Thus, the 1st working die needs to create liquid friction conditions to a greater extent, i.e. pressure dies must provide a lubricant pressure in front of the working die, commensurate with the resistance of the workpiece to deformation - the yield strength of the metal. But, as in the previous known devices, one pressure portage is not able to provide such pressure.

зазора определяет формула (2), где необходимое давление р имеет величину порядка сопротивления деформации при обжатии, что, например, для мягких сталей составит около 400 МПа. При протяжке заготовки ∅ 6,5 мм с характерной для этого диаметра скоростью ν₀=3 м/с и при использовании смазки в виде сухого мыльного порошка, когда эффективная вязкость при рабочих температурах порядка 100°С находится в пределах: μ=8…30 Па⋅с, необходимая длина зазора составит

что, в общем случае, превышает обычную длину калибрующего пояска фильеры. Кроме того, зазор в напорной фильере δ=0,03 мм весьма мал, чтобы обеспечить ввод сухой смазки в рабочую волоку в достаточном количестве, а только при таком условии и может развиться необходимое давление смазки. Плотность сухой порошкообразной смазки обычно меньше плотности сплошного мыла в несколько раз, поэтому напорная фильера должна обеспечивать подачу смазки в объемах, превышающих обычные в такое же число раз. При этом воздух, занимающий остальную часть объема смазки, при ее уплотнении в зазоре должен выходить только в обратном направлении, затрудняя поступление новых порций смазки. Кроме того, эффективная вязкость рыхлой смазки значительно ниже вязкости сплошной, что также затрудняет захват и подачу смазки силами вязкого трения.If we assume that the lubricant pressure required for the hydrodynamic mode at the inlet to the first working die is reached and the thickness of the lubricant layer in the working die is significantly larger and is typical for the hydrodynamic mode of drawing: δ _p = 0.02 mm, then the optimal gap in the pressure die will be ( 3/2) δ _p , i.e. δ=0.03 mm, length

the gap is determined by formula (2), where the required pressure p has a value of the order of the resistance to deformation during compression, which, for example, for mild steels will be about 400 MPa. When drawing a workpiece ∅ 6.5 mm with a characteristic speed for this diameter ν ₀ = 3 m/s and when using a lubricant in the form of dry soap powder, when the effective viscosity at operating temperatures of about 100 ° C is in the range: μ = 8 ... 30 Pa⋅s, the required gap length will be

which, in the general case, exceeds the usual length of the sizing band of the die. In addition, the gap in the pressure die δ = 0.03 mm is very small to ensure the introduction of dry lubricant into the working die in sufficient quantities, and only under this condition can the necessary lubricant pressure develop. The density of a dry powder lubricant is usually several times less than the density of a solid soap, so the pressure die must provide lubricant in volumes that are higher than usual by the same number of times. In this case, the air that occupies the rest of the volume of the lubricant, when it is compacted in the gap, should only exit in the opposite direction, making it difficult for new portions of the lubricant to enter. In addition, the effective viscosity of a loose lubricant is much lower than that of a continuous lubricant, which also makes it difficult to capture and supply the lubricant by viscous friction forces.

For stronger steels, the pressure, and hence the length of the gap, must be correspondingly even greater.

The 3rd disadvantage of the known device is also its unsuitability for effective drawing in the mode of hydrodynamic (liquid) friction and in the second working die.

Indeed, high contact stresses in the first working die prevent the supply of lubrication to the second working die, the lubrication conditions of which, accordingly, worsen.

The 4th disadvantage of the known tool is that its design does not determine the diameters of the auxiliary pressure dies. This feature is more significant than roughness, and it is absolutely necessary for the implementation in the tool design of a regime in which there is an effective hydrodynamic pressure of the lubricant, which could lead to an increase in the thickness of its layer in the deformation zones in the first and second working dies.

Also known is the “Tool for drawing products in the hydrodynamic friction mode” [RF Patent No. 2011449, MKI V21C 3/14 .- 1994, bull. No. 8], consisting of a hard-alloy working drawing die, a pressure die and a sealing washer between them, placed in a clamping conical sleeve, pressed into the body and clamped with a union nut. The inner surfaces of the pressure die, the sealing washer and the working die form a chamber in which the process lubricant is placed. The drawn material moves through the pressure die to the working die. The lubricant is applied by the workpiece and injected in front of the working die, creating high pressure. The output of technological lubricant from the clamping sleeve is excluded by optimally selected parameters. The use of such a drawing tool will increase its wear resistance, reduce lubricant losses and improve the ecology of the drawing process.

The main disadvantage of the known tool is the deterioration of the drawing conditions, in particular, the increase in the drawing force due to the high microroughness of the deformation channel of the first working die.

Indeed, the lubricant moves through the system of dies in the direction of drawing the wire under the influence of the only factor - interaction with the surface of the wire (viscous friction), so the roughness of the pig wire itself, in general, contributes to this. There are two factors preventing the flow of lubricant: the pressure itself, which induces the lubricant to move in the opposite direction - in the direction of its decrease; and viscous friction against the fixed surface of the die channel, so the roughness of its channel, in the general case, prevents the lubricant from moving, since it still moves in the direction of drawing the wire. With the flow of lubricant in the gaps of the pressure bushings, under certain conditions (primarily, with a sufficiently large gap), it is possible to implement a regime with a reverse flow of lubricant near the surface of the pressure die, and then its roughness will actually prevent the outflow of lubricant from the deformation zone. But such a regime cannot be realized in a working die, where the lubricating layer (gap) is very thin, and the lubricant pressure behind this working die is already relatively small.

The results of studies of the well-known tool, performed by the authors when drawing steel wire Bst.04 with a diameter of d ₁ = 2.62 mm from a workpiece d ₀ = 3.0 mm on a (laboratory) installation at a speed of 0.5 m / s of its movement (which is quite small ) are given in the table taken from the same source.

It can be seen from these data that, as the authors claim, the reduction in the drawing force is in good agreement with the parameter representing the roughness ratio. But it also agrees well with the roughness of the second working die, which accounts for the bulk of the total reduction. A slight increase in the decrease in the drawing force with an increase in the roughness of the first working die is explained by the fact that this increases the force of drawing the wire from this first die, which is simultaneously a source of countertension for the second working die, and with a relatively small compression, which nevertheless takes place in the first drawing, and with a slight increase in countertension, a slight decrease in the drawing force can be obtained, which can be seen, for example, in experiments 4 and 5. But the usual compression ratios used when drawing soft steels are about 32 ... 36%, and they are not available for such a system of drawing dies from - due to excessive drag force and breakage.

Confirmation - in the given research results there are no control data - data that could be obtained with the usual low roughness of both working dies. It seems impractical to make special dies with a high roughness of the deformation channel, since such dies are "obtained" directly in the process of using normal dies, made according to the accepted technology. Moreover, in the known tool, the high roughness of the 1st working die is obtained by itself due to accelerated wear due to the above reasons.

The extended section of the application "Prior Art" is completed by a general analysis of all analogs in order to select a prototype from them (for a bibliographic list of analogs, see the Appendix at the end of this Description).

Based on the results of this analysis, the closest in terms of the number of design features common to the claimed object (prototype) is the “Device for drawing” [A.s. USSR No. 1740091, MKI V21S 3/14, publ. 06/15/92, bull. No. 22], containing sequentially located and clamped in the body pressure and working dies, they are pressed into the grooves of individual continuous steel mandrels, and sealing ring-shaped gaskets placed between the dies in the same grooves of the mandrels. The design of the device implies the presence of a body element that keeps the pressure die in contact with the working one through the sealing ring. The device is assembled from standard single dies, regardless of the method of pressing hard-alloy dies into mandrels, which expands the possibilities of manufacturing. The ring, inflating under the action of lubricant pressure, is pressed against the outer surface of the groove and hermetically seals the lubricant in the injection zone.

The first disadvantage of the known device prototype for drawing is the lack of lubrication pressure developed in the gap of the pressure die for the full development of the hydrodynamic lubrication regime, and as a result, an excessive amount of drawing force and low wear resistance of the working dies. The rationale for this drawback, inherent in the previous analogues, is given above.

The second drawback is that when several pressure dies are used in the known device, the design does not contain features that determine the magnitude and sequence of hydrodynamic gaps formed by the cylindrical sections of the pressure die channel with the surface of the drawn workpiece, which also prevents the development of drawing processes with hydrodynamic full lubrication regimes.

The third disadvantage is the insufficient reliability of sealing the seal between the dies.

Firstly, to inflate the steel ring and seal it in the die slot, a significant internal pressure is required. But at the beginning of the drawing process, there is no pressure, and with its gradual increase, inflation of the rings, and hence sealing, does not occur, which can lead to lubricant leaks, and the pressure will not increase to values that ensure sealing.

Secondly, in the known drawing device, the diameter of the sealing ring is large, it at least exceeds the outer diameter of the die, and this also predetermines an increase in lubricant leakage, especially at the beginning of the process, including due to the inevitable roughness of the edges of the sealing rings and internal groove surfaces. If hot pressing of dies into mandrels is used, then after several cycles, due to the formation of scale, the roughness increases significantly.

The 4th disadvantage is the large volume of the hermetic cavity between the dies, which determines the long duration of the initial drawing period, during which this cavity is only filled with lubricant and the pressure in front of the working die does not increase, which causes accelerated wear of the working die during this period in the absence of both boundary and hydrodynamic lubrication regimes.

The 5th drawback is the complexity of manufacturing: in the mandrels of standard dies, it is necessary to make annular grooves for sealing rings.

The objectives of the invention are:

- increasing the pressure of the lubricant developed in the gap of the pressure die for the full development of the hydrodynamic lubrication regime and reducing the magnitude of the drag force;

- increase in wear resistance of working dies;

- determination of the magnitudes and sequence of hydrodynamic gaps formed by cylindrical sections of the channels of pressure dies with the surface of the drawn workpiece;

- increasing the reliability of sealing seals between dies;

- reduction of volumes of hermetic cavities between dies;

- simplification of manufacturing and assembly.

These tasks are solved by the fact that in a prefabricated drawing tool, including a sequence of pressure and working dies clamped in the body, containing the corresponding dies, pressed into the grooves of individual continuous steel mandrels, and sealing ring-shaped gaskets placed between the dies, also placed in the grooves of the mandrels, according to the invention , the pressure dies sequentially form gaps δ ₁ , δ ₂ , ..., δ _n with the workpiece, which together provide a lubrication pressure that reaches the deformation resistance of the workpiece metal in front of the first working die, and the last pressure die forms a gap δ _n with the workpiece, in 1.5 times the thickness of the lubricating layer δ _p in the final working die, characterizing the given mode of hydrodynamic friction, while the sealing ring-shaped gaskets are placed in the free part of the same grooves of the mandrels where the dies are pressed, and they are made of elastic material, with a groove on the inner side of the rings a.

If the pressure dies provide a lubrication pressure in front of the working die, at least equal to the resistance of the workpiece to compression deformation in front of the first working die, then the compression in it is no longer due to contact interaction with the channel surface, but due to lubrication pressure. The thickness of the lubricating layer in the working die depends on the ability of the pressure system (combination of pressure dies, lubricant and moving workpiece) to provide an additional increase in pressure. In the general case, such an excess is always present, for example, due to the pressure effect of the tapering conical part of the channel of the working die. According to the plasticity condition during drawing [Perlin I.L., Ermanok M.Z. Theory of drawing. - M.: Metallurgy, 1971, p. 184.], such a necessary pressure is equal to the contact stress of the radial compression at the beginning of the deformation zone, equal to the difference between the yield strength σ ₀₂ and the countertension stress σ _q . Usually, if there are no special process conditions, the back tension is relatively small, and it can be assumed that the required pressures are close to the yield strength of the respective materials; this is, for example, 120-150 MPa for aluminum, 250-400 MPa for copper and its alloys, 350-500 MPa and higher for steels.

The stated condition for the sequence of values of pressure hydrodynamic gaps δ ₁ /δ ₂ /…/δ _n-1 /δ _n , expresses the requirement that each previous gap, in addition to providing its share of the total pressure, must supply the subsequent gap with lubricant in sufficient quantities, otherwise this the subsequent gap will not provide its own, large share of the pressure. In addition, if a dry lubricant is used, for example, a powder based on metal soap (sodium stearate), then, as the workpiece sequentially passes through the gaps, the soap powder is compacted, its properties approach those of a viscous liquid, and in previous gaps, where these properties closer to the bulk material, the capture of the lubricant is difficult due to its lower density and viscosity, so the previous gaps should be made large to facilitate the capture of the lubricant and supply subsequent gaps with it in sufficient quantities, especially taking into account compaction. The equality of the gaps, corresponding to the most efficient increase in pressure from gap to gap, can take place, for example, only in the case when the properties of the lubricant are close to those of an incompressible liquid, i.e. with a low content of dissolved gases and air, as well as low saturated vapor pressure. Otherwise, due to high pressure differences, breaks in the continuity of the lubricating film (cavitation) are possible, mainly in the first working gap. If the tensile strength of the liquid film is low (dissolved gases, porous filler particles, volatile impurities), then a decreasing sequence should be selected so as not to create significant rarefaction (Bernoulli's law) in the first gaps, where the total pressure is still small.

и шириной δ давление выразится формулойThe claimed condition, according to which the last pressure die forms a gap δ _n with the workpiece, 1.5 times greater than the thickness of the lubricating layer in the first working die, which characterizes the given fluid friction mode, is explained by the requirement for the most efficient increase in the generated pressure, which is associated with the need to use the least amount pressure dies to create the necessary pressure, taking into account all the above conditions. It is known [S.A. Kuznetsov, E.A. Garber, M.Ya. Brovman, S.Yu. Semenov, A.I. Vinogradov. Simulation of the flow of an ideally viscous lubricant in the pressure gaps of a drawing tool. // Sat. Proceedings of the International Conference "Information Technologies in Industrial, Social and Economic Processes", Cherepovets, CGU Publishing House, 1999, p. 101-103], which is created by a pressure gap with a length

and width δ, the pressure is expressed by the formula

where μ is the effective (apparent) viscosity of the lubricant, if we imagine it as a linear-viscous liquid;

ν ₀ - the speed of the workpiece;

q - lubricant consumption (calculated) through the working die, determined by the entire system of dies, and mainly by the conditions in the working die;

q _cr - characteristic critical flow rate for a given gap of width δ, at which viscous stresses on the fixed wall of the gap are zero, determined by the expression

If it is assumed with a high degree of certainty that the pressure in the lubricating layer of the working die does not change significantly further along the length, then the lubrication rates change linearly along the thickness of this layer from 0 on the surface of the die to v ₀ on the surface of the workpiece (the “sticking” condition), then the consumption lubrication through the working die is determined [ibid.]:

where δ _p is the thickness of the lubricant layer in the working die, which determines the flow regime of the lubricant and the coefficient of friction during drawing.

Using these expressions, we obtain formula (1), in which the pressure created by the gap width δ is expressed through the thickness δ _P of the lubricating layer in the working die. If we further take the derivative of the generated pressure with respect to the width δ of the gap, we get:

, при которой повышение давление по длине

максимально. То, что данный экстремум является именно максимумом, доказывает то, что при меньшей ширине δ_р давление понижается, а при ее значительном увеличении -давление также снижается - см. формулу (1).Equating the derivative to zero, we obtain the extreme value of the gap width

, at which the increase in pressure along the length

maximum. The fact that this extremum is precisely the maximum proves that with a smaller width δ _р , the pressure decreases, and with its significant increase, the pressure also decreases - see formula (1).

Thus, if the last pressure die forms a gap δ _n with the workpiece, which is 1.5 times greater than the thickness δ _{p of the} lubricating layer in the first working die, then the pressure created by it will be the maximum possible, and since the rest of the pressure gaps are associated with this gap, it becomes possible to select the smallest number of pressure dies that provide the required pressure.

The claimed design feature, according to which, sealing ring-shaped gaskets are placed in the free part of the same grooves of the mandrels where the dies are pressed, and the fact that they are made of elastic material and with a groove on the inner side of the ring, with its maximum simplicity, ensures a high degree of reliability of the sealed connecting the fibers to each other. The installation of annular gaskets does not require special grooves in the die mandrel - annular gaskets are made with an outer diameter equal to the outer diameter of the dies pressed into the mandrel, and with a width equal to the width of the remaining free part of the mandrel groove in which the die is located. The fact that the annular spacers are made of an elastic material, such as rubber, with a groove on the inner side of the ring, leads to effective self-sealing with swelling both outward and sideways, with a tight fit of the adjacent surfaces of the dies and their mandrels.

Thus, the task is fulfilled - the most effective achievement of the hydrodynamic friction mode and, due to this, a decrease in the drawing force and an increase in the wear resistance of working dies, as well as simplification of manufacturing and assembly through the use of a minimum number of pressure dies.

In addition, the sequence of pressure clearances δ ₁ , δ ₂ , ..., δ _n can be a geometric progression. This ratio between the pressure clearances is most acceptable if a lubricant is used for drawing, the properties of which (density, effective viscosity) change significantly with increasing pressure, for example, loose powdered lubricant based on metal soap with a filler of particles of a colloidal nature that form skeleton structures. In the initial state, the conditions for the capture of the lubricant are facilitated, which corresponds to large gaps in the first dies.

In addition, the sequence of pressure gaps δ ₁ , δ ₂ , ..., δ _n can be an arithmetic progression. Such a relationship between pressure gaps is more acceptable if a lubricant is used for drawing, the properties of which change less significantly or slightly with increasing pressure, for example, greases based on mineral oils filled with organic substances or particles of soft materials, or liquid lubricants and emulsions.

In addition, in the case of powdered lubricants, it is advisable that the first pressure die forms a pressure gap δ ₁ with the workpiece, providing an initial lubricant pressure of 14.7 MPa. So, it is known that with an increase in pressure, the rheological (effective viscosity) and mechanical (density) properties of a powdered lubricant change significantly only up to a given pressure, and with a further increase, these properties change only slightly [Kolmogorov V.L., Orlov S.I. , Kolmogorov G.L. Hydrodynamic lubrication. - M.: Metallurgy, 1975, 256 p. With. 100-101], therefore, in this case, the gap in the first pressure die should be selected empirically, since the calculation with variable properties of the initial lubricant cannot give reliable results, and the gaps of the remaining pressure nozzles can be calculated, for example, according to the above dependencies.

In addition, an additional sealing die can be placed in the prefabricated drawing tool in front of the first pressure die. This can be done when the first pressure die cannot provide the required lubricant pressure of 14.7 MPa, which is sufficient to convert the powdered friable lubricant into a liquid that is little compressible, even if very viscous.

In addition, in this prefabricated drawing tool, there should be at least two and no more than three working dies, and the countertension value for each of these dies is close to, or may slightly exceed, the critical value.

Indeed, according to recognized literary data [Perlin I.L., Ermanok M.Z. Drawing theory - M.: Metallurgy, 1971, p. 199], countertension is the value at which it begins to influence the drawing force. If it reaches and slightly exceeds the critical, boundary value of the force of pulling the wire from the previous die, it begins to increase. Consequently, then the “overcritical” countertension becomes a harmful factor, it begins to interfere with the drawing process, that is, it leads to breaks. If the countertension does not reach a critical value, then it does not increase the drawing force at all, but only leads to an increase in the longitudinal reaction of the die. This value can be approximately expressed by the formula:

where μ _Σprev. - total (total) metal drawing after the last annealing (preliminary);

μ _Σmax - possible maximum total drawing between annealings;

σ _0.2prev. - conditional yield strength before drawing through a given die (preliminary). It is also known [S.A. Kuznetsov, A.I. Vinogradov. Theory of drawing and pressing. - Teaching aid for laboratory work. Publishing House of ChGU, Cherepovets, 1998] that, for example, for steels of ordinary quality, the critical countertension is approximately 40% of the pulling force through the working die. For example, when pre-drawing wire rod in a technological production line before drawing through means of acid-free cleaning of wire rod from scale. For some other steels and alloys, the critical backtension may be about 20% of the drawing force. It is clear that there can be no more than 3 such working dies (those whose diameter is less than the diameter of the workpiece). If the pulling force through the 3rd working die is determined as the maximum possible with sufficient reliability of the drawing process, then the pulling force through the previous 2nd working die, which is approximately the critical countertension for the 3rd one, will be 40% of the pulling force through this 3rd working die. th die. The pulling force through the 1st working die will be 40% of 40%, that is, 16%o, since this force is also approximately the critical counter-tension for the 2nd working die. If there were another die before the 1st one, then the pulling force through it would have to be 40% of 16%, that is, only 6%, which can be even less than the friction force with minimal reductions. Such a small effort will be provided by a scale breaker and other means of mechanical cleaning of wire rod.

In addition, the side wall of the inner groove of the annular gasket can be made thinner towards the center of the ring.

Indeed, this will additionally increase the elasticity of the edge of the sealing ring, facilitating and improving its fit to the surfaces to be sealed even under low pressure, including in the initial period of the drawing process, when the pressure only increases and this contributes to the rapid achievement of the hydrodynamic friction mode and reduces the wear of the dies .

In addition, the body can be mounted on a horizontal axis of rotation perpendicular to the direction of drawing, with the possibility of bringing it into a vertical position with the working die down.

Indeed, due to this, before the task of the pointed blank into the pressure section, if the body is brought to a vertical position and the outlet of the working section is closed, the powdered lubricant from the soap dish will enter the common channel of the prefabricated drawing tool under the action of gravity and fill it. With the further task of the pointed workpiece, a partial compaction of the lubricant powder will occur. Significant time spent on filling the cavities with lubricant after the start of broaching will not be required and, thereby, the time required to establish the drawing process in the hydrodynamic friction mode will be reduced. When applying lubricant under the action of the movement of the workpiece, it is only necessary to carry out a further increase in its pressure. This thus reduces the time of operation of the device in transient mode and reduces the wear of the dies.

In addition, the lubricant under pressure in the chambers between the working dies can be brought into mechanical contact with sources of vibrations in the ultrasonic range.

Indeed, it has been established that, by imparting vibrations to the drawing tool, it is possible to achieve a significant reduction in drawing forces and stresses. With a decrease in forces and stresses, it is possible to increase the degree of deformation per transition [I.L. Perlin, M.Z. Yermanok. Drawing theory, p. 87]. Drawing with the application of mechanical vibrations of ultrasonic frequency cannot be considered only from the standpoint of the mechanical addition of the translational movement of the workpiece point along the generatrix of the die channel and movement in the direction of vibration propagation. When drawing with ultrasonic vibrations, a wave process occurs when the wavelength is commensurate with the dimensions of the tooling and the distance from the die to the traction device (drawing drum).

Ultimately, the energy of ultrasonic vibrations is absorbed in the deformation zone, being transferred to it necessarily through the lubricant layer. It does not matter how the ultrasonic vibrations are transmitted to the lubricant, either through vibrations of the tool, or vibrations of the workpiece, or in any other way. In this case, the power of the vibration source (0.5…3.0 kW for ∅ 6.5 mm) is much less than the direct costs of the deformation process.

Piezoelectric or magnetostrictive emitters are used as sources of mechanical ultrasonic vibrations.

In a piezoelectric emitter, an inverse piezoelectric effect is used: in crystals of quartz, Rochelle salt, tourmaline, etc., under the action of an alternating electric field, alternating deformations occur.

The magnetostrictive emitter uses the effect of magnetostriction. It lies in the ability of some ferromagnetic materials to change their dimensions in an alternating magnetic field. The most commonly used magnetostrictive materials are pure nickel, an alloy of nickel with iron (permalloy), and an alloy of cobalt with iron (permendur).

In this case, it seems appropriate to use a magnetostrictive source, since the magnetostrictive material is a metal that is capable of absorbing significant stresses. Piezoelectrics are usually brittle dielectric crystals that cannot withstand large voltages.

In order to study the state of the art, a patent search was conducted for known pressure drawing devices under section IPC B21C 3/14 - “matrix holders with devices for guiding the material being drawn or with devices for cooling, heating or lubricating” with a depth from 1970 to 2009, as a result which drawing devices with the entire claimed set of distinctive features aimed at solving these problems have not been found.

The design of the prefabricated drawing tool is shown schematically in Fig. 1, 2, 3:

- fig. 1 - prefabricated drawing tool, longitudinal section; its body, so as not to clutter up the drawing, is conditionally shown as one-piece; the volume occupied by the lubricant is conditionally highlighted by hatching with dots; the lubricant located in the channel of the prefabricated drawing tool, so as not to clutter up the drawing, is conventionally not shown; the direction of drawing is indicated by a contour arrow; the direction of bringing the body to a vertical position is indicated by an arcuate arrow;

- fig. 2 - ring-shaped seal, in section (enlarged);

- fig. 3 - cavity between working dies filled with lubricant brought into mechanical contact with a source of ultrasonic vibrations.

Prefabricated drawing tool is arranged as follows (Fig. 1, 2).

The workpiece L, which at first is a wire rod, after leaving the prefabricated drawing tool, is a wire, which we will call finished. The prefabricated drawing tool includes a steel body 2, in which pressure 3 and working dies 4 are sequentially clamped. Pressure dies form a sequence of gaps δ ₁ , δ ₂ , ..., δ _n with the workpiece, and δ ₁ /δ ₂ /.../δ _n-1 / δ _n , the last pressure die forms a gap δ _n with the workpiece, 1.5 times exceeding the thickness of the lubricating layer δ _P in the final working die, characterizing the given mode of fluid friction. The dies consist of corresponding dies pressed into the grooves of individual continuous steel mandrels 5. The dies are standard, which are usually used at the enterprise. In the same grooves of the mandrels, between the dies, there are sealing ring-shaped gaskets 65 made of an elastic material, for example, rubber reinforced with strong fibers. Grooves are made on their inner side, and the side walls of these grooves are made with thinning towards the center of the ring (Fig. 2). The sequence of pressure clearances δ ₁ , δ ₂ , ..., δ _n can form a geometric or arithmetic progression. The 1st pressure die forms a pressure gap δ ₁ with the workpiece, providing an initial lubricant pressure of 14.7 MPa. An additional sealing die 7 is placed in front of the 1st pressure die. There are three working dies, no more, and their diameters are made such that the hoods μ ₁ , μ ₂ , μ ₃ form an increasing sequence, such that the value of the countertension for each of these dies is close to critical. The body of the entire prefabricated drawing tool is mounted on a horizontal axis 8 of rotation, perpendicular to the direction of drawing, with the possibility of bringing it into a vertical position with the working section down. A lubricating bath (soap dish) containing dry powdered lubricant 9 is installed in front of the body of the prefabricated drawing tool.

In the case when the lubricant in the cavity between the dies is brought into mechanical contact with a source of ultrasonic vibrations, the prefabricated drawing tool is designed as follows (Fig. 3): ; 13 - ultrasound source (powerful vibrator); spring 14 balanced with process lubricant pressure.

Prefabricated drawing tool works as follows.

The workpiece 1 is pulled through a prefabricated drawing tool, which includes a steel body 2, in which several (shown 3) pressure 3 and 3 working dies 4 are successively clamped (Fig. 1). The pressure dies are pressed into mandrels 5 and form a sequence of decreasing gaps δ ₁ , δ ₂ , ..., δ _n with the workpiece, which together provide the process lubricant pressure, which reaches the value of the deformation resistance of the workpiece in front of the working dies, and the last pressure die forms a gap δ with the drawn workpiece _n , 1.5 times greater than the thickness of the lubricating layer δ _P in the final working die, characterizing the achieved mode of fluid friction. The annular spacers 6 are made, for example, of rubber reinforced with strong fibres. Grooves are made on their inner side; they are placed in the same grooves of the mandrels where the dies are placed. The side walls of the grooves in the gaskets are made with thinning towards the center of the ring (Fig. 2), which reliably seals the dies between each other. Since the 1st pressure die forms a pressure gap with the workpiece, which by itself should provide an initial lubricant pressure of 14.7 MPa, but cannot cope with this, since the powdered lubricant is very loose, an additional sealing die is placed in front of the 1st pressure die. die 7, which converts the lubricating powder into an incompressible viscous liquid. Under such conditions, the 1st pressure die is already able to create the specified pressure. There are no more than 3 working dies, and the sequence of their extracts μ ₁ , μ ₂ , μ ₃ form an increasing sequence, such that the value of the countertension for each of these dies is close to critical, which does not increase the drawing force. Since the body of the entire prefabricated drawing tool is installed on a horizontal axis 8 of rotation perpendicular to the direction of drawing, before starting work, it must be given a vertical position with the last working die down, and then, after covering, for example, with a finger, the hole of this die, the lubricant that was originally in soap dish 9, is poured into the prefabricated drawing tool and fills its cavities. When filling the pointed end of the workpiece into the prefabricated drawing tool, some compaction of the initial powdered lubricant occurs, and in a relatively short time, the hydrodynamic regime using rational countertensions is successfully achieved.

In the case when the lubricant in the cavity between the dies is brought into mechanical contact with the source of ultrasonic vibrations, the prefabricated drawing tool works as follows (Fig. 3): the ultrasonic sound source or simply a sufficiently powerful vibrator 13 through the rod 11 acts on the plunger 10. placed in the hydraulic cylinder 12, while the spring 14 balances the lubricant pressure. In this case, the lubricant located in the sealed cavity acts on the metal in the deformation zone, which leads to a decrease in contact stresses and all the above positive effects.

Since the prefabricated drawing tool consists of the corresponding pressure and working dies, pressed into the grooves of individual continuous steel mandrels, their manufacture is carried out according to the usual technology adopted at the enterprise. Dies are standard, such as are usually used at the enterprise. Since drawing through a prefabricated drawing tool with a hydrodynamic friction mode in the deformation zone is characterized by an indefinite final diameter specified by the hydrodynamic modes and countertensions, and also due to the fact that the reduction is dictated not so much by the diameter of the last working die, but is carried out by the lubricant pressure, the finished wire is characterized by some diameter and surface quality uncertainty, this assembly drawing tool is only intended for use in intermediate transitions of multiple drawing mills. These intermediate reductions, according to calculations, for steels of ordinary quality should reach and even exceed 40%, which will lead to a decrease in the mill ratio.

In conclusion, it should be noted that this claimed technical solution will be part of a single inventive concept. It will promote the industrial application of a drawing tool with a hydrodynamic grip and injection of technological lubricant into the deformation zones during repeated drawing at all intermediate transitions. The initial, opening inventions of this idea were patents of the Russian Federation No. 2539520, IPC B21 s 1/12, published on 01/20/2015 in Bulletin No. 2 (priority 09/20/2013) "Multiple direct-flow drawing mill for sizing blanks" and No. 2741395, IPC V21 s 1 /12, published on January 25, 2021, bulletin No. 3 (priority July 11, 2019) "Direct-flow drawing machine for coarse-medium wire drawing", which were designed to bring into logical harmony the procedure for ensuring hydrodynamic modes of lubrication of rubbing surfaces in deformation zones during repeated wire drawing .

It is clear that in this application only the 1st transition is considered in detail, and here it is shown how the sectional drawing tool is assembled, consistent with this technical solution. The tools for the following transitions are arranged in a similar way, while for individual components other, smaller standard sizes of conventional dies in mandrels used in drawing and sizing production are used.

Sources of information taken into account when drawing up the application (analogues):

1. Kolmogorov V.L., Orlov S.I., Kolmogorov G.L. Hydrodynamic lubrication. - M.: Metallurgy, 1975, 256 p. With. 14-16; (pressure tube).

2. Device for drawing products in the mode of hydrodynamic friction. USSR patent No. 1804354, IPC B21C 3/14, publ. 1993, bull. No. 11; (several pressure elastic bushings).

3. Technological tool for drawing products in the mode of hydrodynamic friction. A.s. USSR No. 1468630, IPC V21C 3/14, publ. 30.03.89, bull. No. 12. (groove ring).

4. Device for drawing in the mode of hydrodynamic friction. A.s. USSR No. 1360839, IPC V21C 3/14, publ. 12/23/87, bull. No. 47; (pressure die, working die, split sleeve, thermal compensation washers).

5. Drawing tool. A.s. USSR No. 1810153, IPC V21C 3/14, publ. 04/23/93, bull. No. 15; (solid taper bushing).

6. Device for drawing in the mode of hydrodynamic friction. A.s. USSR No. 1752467, IPC V21C 3/14, publ. 07.08.92, bull. No. 29.

7. Drawing tool. A.s. USSR No. 1687321, IPC V21C 3/14, publ. 30.10.91, bull. No. 40; (roughness).

8. Tool for drawing products in the mode of hydrodynamic friction. RF patent No. 2011449, IPC V21C 3/14. (Sokolov I.A., Orlov S.I. and others) - 1994, bull. No. 8.

9. Drawing device. A.s. USSR No. 1740091, MKI V21C 3/14, publ. 06/15/92, bull. No. 22. (ring in annular grooves), (prototype).

Claims (6)

1. A prefabricated drawing tool containing pressure and working dies sequentially clamped in the body, including the corresponding dies, pressed into the grooves of individual continuous steel mandrels, and sealing ring-shaped gaskets located between the dies and placed in the grooves of the mandrels, characterized in that it is equipped with an additional sealing by a die placed in front of the first pressure die, the pressure dies are made with the possibility of forming pressure gaps δ with the workpiece_one, δ₂, …, δ_n, collectively providing a lubrication pressure that reaches the deformation resistance of the workpiece metal in front of the first working die, and the pressure gaps δ_one, δ₂, …, δ_n form a sequence, the last pressure die is configured to form a pressure gap δ_n, the value of which is 1.5 times greater than the thickness of the lubricating layer δ_R in the final working die, which characterizes the given mode of fluid friction, the first pressure die is made with the possibility of forming a pressure gap δ with the workpiece_one, providing an initial lubrication pressure of 14.7 MPa, working dies, the number of which is at least two and no more than three, are made with a diameter that provides drawings, the values of which are μ_one, μ₂, μ₃form an increasing sequence with the provision of a countertension value for each of these dies that does not reach a critical value, and sealing annular gaskets are placed in the free part of the grooves of the mandrels in which the dies are pressed, and are made of elastic material and with a groove on the inner side of the ring. 2. Prefabricated drawing tool according to claim 1, characterized in that the sequence of pressure gaps δ ₁ , δ ₂ , ..., δ _n forms a geometric progression. 3. Prefabricated drawing tool according to claim 1, characterized in that the sequence of pressure clearances δ ₁ , δ ₂ , ..., δ _n forms an arithmetic progression. 4. Prefabricated drawing tool according to claim 1, characterized in that the side wall of the annular gasket is made with thinning towards the center of the ring. 5. Prefabricated drawing tool according to claim 1, characterized in that the body is mounted on a horizontal axis of rotation perpendicular to the direction of drawing, with the possibility of bringing it into a vertical position with the working die down. 6. Prefabricated drawing tool according to claim 1, characterized in that it is configured to bring the lubricant under pressure in the chambers between the working dies into mechanical contact with ultrasound sources.

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