RU2491144C2 - Method of producing hollow cylindrical articles - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be used for forging thin-wall cylindrical articles. Local radial recesses are formed at round sheet billet flange part to turn over said billet by its recesses upward and to draw it for making a cylindrical barrel. Then, extra recesses are forged at barrel cylindrical surface along its axis. Then, final barrel drawing is made with displacement of radial recesses at flange part to article cylindrical part with conserved extra recesses at the article. Note here that said local recesses in amount of 12-24 feature the depth equal to 0.4-0.6 of sheet initial thickness.

EFFECT: ruled out scallops in drawing of anisotropic materials, loss in article shape stability and shape distortion.

Description

The invention relates to mechanical engineering and can be used for the manufacture of stamping from a sheet of cylindrical thin-walled products.

Known methods for the manufacture of stamping hollow cylindrical products, for example by drawing under pressure in the cavity of the matrix of a cylindrical punch, see E.A. Popov "Fundamentals of the theory of sheet stamping" Moscow, Mechanical Engineering. 1977. S. 278. These methods have the disadvantage that the dimensional accuracy is low and the length of the workpieces is limited.

There is also a known method of manufacturing hollow articles by stamping according to copyright certificate No. 472722, IPC V21D 22/02. The central part of the product is formed from the heated billet, leaving a flange under the clamp that is equal to two to three thicknesses of the sheet from which the product billet is formed.

However, if the diameter of the obtained product is 1.7-2.0 times smaller than the diameter of the original sheet blank, then during deformation, stability is lost and wrinkles are formed at the edges of the sheet, which distorts the shape of the product and leads to marriage.

There is also a known method of manufacturing products by hood with holding a deformable workpiece by a ring located around the punch, see Japan Patent 57-168730, 821018 (application 62-5690) MKI V21D 26/04 from 1987. Compression in the direction is provided along the side surfaces of the sheet blank to the axis of the workpiece. However, for thin-walled sheet blanks used in drawing, such an effect on the side surface is ineffective.

There is a method according to the author's certificate of the USSR No. 5445406, IPC V21 D / 22.02 "Method of stamping spherical, elliptical and other dome-shaped bottoms (Bulletin of inventions 1977, No. 5). The method provides for the implementation on free areas of the workpiece of the recesses and stiffeners with curvature decreasing from the perimeter of the workpiece to the center.

However, the recesses perform an annular shape, and they do not increase the stability of the deformable workpiece during its stamping with respect to distortion of its shape and the formation of folds, which reduces the accuracy of the dimensions of the product and its allowable length.

The closest analogue of the technical solution adopted for the prototype is the invention according to the patent RU (11) 2217257 (13) C2 (51) MPK7 B21D 22/20 "Method for extracting hollow products from sheet blanks". Forming is carried out with the simultaneous formation of corrugations in the flange part with their subsequent smoothing. Preliminary application of the corrugations reduces the anisotropy of the mechanical properties of the workpiece, but the stability of the workpiece during the drawing process is not ensured, the metal consumption, the complexity of the die tooling are increased. After smoothing the corrugations in the metal of the workpiece, high residual compressive stresses arise.

The proposed method is aimed at solving the technical problem - to provide the ability to extrude from sheet blanks in the form of a disk of hollow cylindrical products of a wide range of diameters and lengths without loss of stability and the formation of folds at the edges of the workpiece. This technical problem is solved in that on the flange part of the round sheet blank, local recesses are formed uniformly around the circumference, oriented along the radii of the specified blank, with a depth of 0.4-0.6 of the initial thickness of the sheet blank and the number 12-24, then the blank is turned upside down carry out the extraction of its cylindrical part, after which additional recesses are squeezed out on its cylindrical surface, and then the final extraction of the product is carried out with the indicated angles Blenheim.

The grooves are extruded at the beginning of the manufacturing process on flat sections of the workpiece, orienting these grooves in the direction of the radii of the round sheet blanks, and on a cylindrical surface.

These recesses reduce the rigidity of the workpieces, reduce the tangential stresses during compression, and prevent the possibility of loss of stability and the occurrence of recesses (folds) of large sizes. In fact, local recesses (i.e. folds), but of such small sizes (much smaller than those that occur “naturally” with loss of stability) that the folds do not impair the properties of the obtained product during its operation, are specially formed in the deformable workpiece.

It is known that when drawing sheet blanks, the maximum thickness changes without loss of stability reach 40% of the initial sheet thickness, which is confirmed by a large number of experimental data, see, for example, L.A. Shofman "Theory and calculations of cold stamping processes." M .: Engineering. 1964, p. 144.

With a certain margin, recesses are artificially formed on the workpiece within 0.40-0.50 of its initial thickness, which prevents the appearance of significant distortions in the shape of the product.

It is these distinctive features that provide a solution to the technical problem. There is a direct causal relationship between the hallmarks of the method and the results of solving the technical problem. The execution on the workpiece recesses oriented along its radii prevents the possibility of loss of stability and distortion of the shape of the products.

A device for implementing the method is illustrated by the drawings of figures 1, 2, 3, 4, 5, while figure 1 shows the extrusion in the workpiece at the beginning of the process of recesses, in figure 2 an intermediate stage of drawing, in figure 3 is a top view of the deformable workpiece, in Fig.4 the shape of the product obtained during the landing and in Fig.5 - its section (along the plane AA).

Designations are accepted - 1 - the initial workpiece in the form of a disk, 2 - a stamp for extruding radial recesses. 3 - matrix, 4 - recesses oriented along the radius of the workpiece. The cylindrical part of the product - 5 is formed during the extraction by the punch 6. The recesses of the second row are indicated by 7.

Here is the operational description of the method.

The first operation of the technology for manufacturing hollow cylindrical parts is the operation of cutting round billets in the form of a disk 1 from sheet metal, and during the second operation, the workpiece 1 is deformed with a stamp 2 on a matrix 3, see Fig. 1 and radial parts are formed on the flange part of the workpiece 1 recesses 4.

The number of these recesses is taken equal to 12-18, which provides a significant reduction in the stiffness of the workpiece in compression in the tangential direction and prevents the appearance of large folds. The recesses are made with a width of "b" and a depth of "δ", see figures 1, 2, 3.

The next operation is the supply of the workpiece 1 to the press, while it is turned 180 ° so that the radial recesses will be located on top, see figure 2.

The fourth operation is an extract from a sheet of a cylindrical glass 5 with a punch 6, Fig.2, 3.

The fifth operation consists in extruding on the cylindrical surface of the workpiece 5 an additional series of recesses - 7, oriented along the axis of the workpiece. This is done by special punches in pairs by pressure of two punches, when moving them towards each other. The extrusion of a number of recesses 7 reduces the tangential compressive stresses and eliminates distortion of the shape of the product.

If the shape of the recess (both in row 4 and row 7) can be described as an arc of a circle of radius “r”, then the increase in the length of this section of the workpiece

$$\Delta l_{\mathrm{one}}=r\alpha -2r\sin \frac{\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="00000024.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}{2}$$

угол, соответствующий одному углублению шириной «b», см. фиг.3. Можно записатьWhere $$\alpha =2\arccos \left(\frac{r-\delta }{r}\right)$$

the angle corresponding to one recess width "b", see figure 3. Can record

$$\Delta l_{\mathrm{one}}=r[2\arcsin \sqrt{\mathrm{one}-{\left(\mathrm{one}-\frac{\delta }{r}\right)}^2}-2\sqrt{\mathrm{one}-{\left(\mathrm{one}-\frac{\delta }{r}\right)}^2}$$

or

$$\Delta l_{\mathrm{one}}=r\left[\mathrm{<figure-callout\; id="2"\; label="arcsin"\; filenames="00000024.png"\; state="\{\{state\}\}">arcsin</figure-callout>}\sqrt{2\frac{\delta }{r}-\frac{{\delta }^2}{r^2}}-2\sqrt{\left(2\frac{\delta }{r}-\frac{{\delta }^2}{r^2}\right)}\right]\left(\mathrm{one}\right)$$

$$r\cdot \sin \frac{\alpha }{2}=\frac{b}{2};$$

$$\sin \frac{\alpha }{2}=\frac{b}{2r};$$

$$r\left(1-\sqrt{1-\frac{b^2}{4r^2}}\right)=\delta .$$

If, along a circle of radius R, “n” depressions are performed, then the total increase in length is: n · Δl ₁ and the length decreases from 2π · R to 2πR-n · l ₁ , while $$r\left(\mathrm{one}-\cos \frac{\alpha }{2}\right)=\delta ,$$

$$r\cdot \mathrm{<figure-callout\; id="2"\; label="sin\; \alpha "\; filenames="00000024.png"\; state="\{\{state\}\}">sin\; </figure-callout>}\frac{\alpha }{}\frac{}{2}=\frac{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}{2};$$

$$\mathrm{<figure-callout\; id="2"\; label="sin\; \alpha "\; filenames="00000024.png"\; state="\{\{state\}\}">sin\; </figure-callout>}\frac{\alpha }{}\frac{}{2}=\frac{b}{2r};$$

$$r\left(\mathrm{one}-\sqrt{\mathrm{one}-\frac{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^2}{\mathrm{four}{r}^2}}\right)=\delta .$$

Having decided on "r", we obtain from formula (1)

$$\frac{\delta }{r}=\frac{8{\delta }^2}{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^2+\mathrm{four}{\mathrm{<figure-callout\; id="2"\; label="\delta "\; filenames="00000024.png"\; state="\{\{state\}\}">\delta </figure-callout>}}^2}$$

$$\Delta l_{\mathrm{one}}\approx \frac{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^2}{\mathrm{four}\delta }\left[\arcsin \sqrt{\frac{16{\delta }^2}{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^2+\mathrm{four}{\delta }^2}}-\sqrt{\frac{16{\delta }^2}{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^2+\mathrm{four}{\delta }^2}}\right]\left(2\right)$$

and at small values $$\frac{\delta }{b}$$

$$\Delta l_{\mathrm{one}}\approx \frac{{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^2}{\mathrm{four}\delta }[\arcsin \left(\mathrm{four}\frac{\delta }{b}\right)-\left(\frac{\mathrm{four}\delta }{b}\right)$$

$$\Delta l=2\pi R-\frac{b^{2}n}{\mathrm{four}\delta }[\arcsin \left(\mathrm{four}\frac{\delta }{b}\right)-\left(\frac{\mathrm{four}\delta }{b}\right)\left(3\right)$$

If you use a row

, $$\arcsin u=u+\frac{{\mathrm{<figure-callout\; id="3"\; label="U"\; filenames="00000024.png"\; state="\{\{state\}\}">U</figure-callout>}}^3}{6}+\frac{3}{40}{u}^5+...$$

,

, и ограничиться двумя членами ряда, то получим уменьшение длины окружности наWhere $$u=\mathrm{four}\frac{\delta }{b}$$

, and confine ourselves to two members of the series, then we obtain a decrease in the circumference by

$$\Delta l=\frac{b^{2}n}{\mathrm{four}\delta }\frac{64{\delta }^3}{{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="00000024.png"\; state="\{\{state\}\}">b</figure-callout>}}^3}=\frac{16n{\delta }^2}{b}\left(\mathrm{four}\right)$$

and, therefore, applying “n” depressions with a width of “b” and a depth of δ along a circle of radius R is equivalent to an increase in length by Δl and a decrease in compression strain by

$$\epsilon =\frac{\mathrm{<figure-callout\; id="2"\; label="\Delta \; l"\; filenames="00000024.png"\; state="\{\{state\}\}">\Delta \; </figure-callout>}l}{2\pi R}=\frac{8\mathrm{<figure-callout\; id="2"\; label="n\; \delta "\; filenames="00000024.png"\; state="\{\{state\}\}">n\; </figure-callout>}{\delta }^{}{}^2}{\pi bR}=\mathrm{2,55}\frac{n{\delta }^2}{bR}\left(5\right)$$

For example, with n = 18, δ = 0.5 mm, b = 10 mm and R = 100 mm

$$\epsilon =\mathrm{2,55}\cdot \frac{\mathrm{eighteen}\cdot 0.25}{10\cdot 1000}=1.15\cdot {10}^{-3}$$

and the ratio of the yield strength σ _t to the elastic modulus, for example, for carbon steels $$\frac{\sigma {}_t}{E}=\frac{350}{2\cdot {10}^5}=1.75\cdot {10}^{-3}$$

величины $$\frac{{\sigma }_{т}}{Е}$$

.σ _t = 350 MN / m ² , E = 2 · 10 ⁵ MN / m ² ), therefore, unloading to $$\frac{1.15}{1.75}=0.63-9.66$$

values $$\frac{{\sigma }_t}{E}$$

.

произойдет полная разгрузка материала, а при ε=1,15·10^-3 существенное уменьшение напряжений - более, чем в два раза.At $$\epsilon =\frac{{\sigma }_t}{E}$$

complete unloading of the material will occur, and at ε = 1.15 · 10 ^{-3 a} significant reduction in stresses will be more than doubled.

Usually during planting, if the ratio of the diameters of the initial billet and the cup exceeds 1.8 ... 2.0, there is a loss of stability of the disk shape at the surface of the outer diameter with the formation of 4-6 scallops (folds), see for example R. Hill, “Mathematical Theory of Plasticity. Gostekhteorizdat. 1956. P.407. To reduce the size of the recesses (folds) during the implementation of this method, they are created artificially, before the deformation of the landing and in the process of landing. And so that the dimensions of the recesses are significantly reduced, their number is increased by 3-4 times, i.e. up to 12-24 with the value of the recesses δ = (0.4 ... 0.5) h, i.e. 0.4 ... 0.5 of the initial thickness of the deformable sheet.

When the depth of 6 created recesses is less than 0.4 of the sheet thickness, it will not be possible to unload the deformable sheet from the action of high compression stresses and prevent an increase in their size. If the depth exceeds 0.6 sheet thickness, then it will be useless and will only increase the work spent on plastic deformation.

If the number of recesses is less than 12, unloading from the action of compression stresses will not be provided, and if their number exceeds 24, an additional positive effect will not be achieved, but the work of deformation will increase and the deforming tool will become unnecessarily complicated.

The above confirms the optimality of the proposed depth intervals and the number of recesses created on the workpiece.

The optimal value of the width of the recesses corresponds to 10-20 values of the thickness of the workpiece.

We give a specific example of the implementation of the method.

A batch of products was made of a filter housing with a diameter of 110 mm. From a sheet 0.5 mm thick steel 45 (GOST 19903-74), plates 680x1250 mm are first cut on sheet scissors GN-473, and blanks in the form of disks with a diameter of 210 mm are cut out from them. On a press with a force of 50MN, 18 depressions are formed by compression, oriented along the radii of the disk, 10 mm wide and 0.6-0.5 = 0.3 mm deep.

After this, the workpiece is turned over (a disk with radial recesses on top) and the product KE2330 is pressed to draw the product with a diameter of ≈ 80 mm to a height of 90 mm. After that, an additional row of recesses is applied along the ring at a distance of 90 mm from the bottom on a double-sided press (their number is 18, the depth is 0.3 mm).

After this, the hood is continued until the length of the glass product reaches 150 mm on the KE2330 press.

The deformation is carried out by lubricating the surface of the workpiece with gear oil.

After drawing out carry out the cleaning of its edge sections of the workpiece.

The recesses remain on the product without compromising its performance in this case.

The method allows to significantly expand the assortment of products by increasing the depth of cylindrical products, which can be obtained by drawing from sheet blanks by reducing their stiffness during radial metal flow and especially tangential stresses.

Claims (1)

A method of manufacturing a hollow cylindrical products, including the formation on the flange part of the circular sheet blanks of local recesses and the extraction of the cylindrical products from the blank of the cylindrical product on the press, characterized in that the local recesses are oriented along the radii of the circular blank and squeezed with a depth of 0.4-0.6 the initial thickness and are evenly distributed around the circumference with their number equal to 12-24, after which they turn the workpiece with its recesses up and draw out its cylindrical surface, then squeezed additional recesses are formed on its cylindrical surface, and the final extraction of the cylindrical product is carried out with the indicated recesses remaining on it.

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