RU2556846C1 - Method of producing thin-wall shells - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: flat sheet blank is used to form hollow semi-finished part with shaped bottom. Rotary drawing of thin-wall cylindrical section of the shell is performed in two-three steps at tolerable deformation degree. Note here that shell bottom depth is set by cutting the outer surface of hollow semi-finished part. outer surface of hollow semi-finished part is turned to produce circular ledge thereat with seats for connection of the article mating parts. Semi-finished part bottom shaped section is subjected to forming and cutting to get hollow cylindrical ledge inside said bottom part. Said shell cylindrical section and shaped bottom are conjugated by a hollow truncated cone. Bulged cylindrical section is formed at cylindrical section end opposite the shell shaped bottom section by rotary reduction. Said shell hollow truncated cone is produced by forming, outer surface cutting and rotary reduction. Note here that rotary drawing of conical section is combined with rotary drawing of cylindrical section.

EFFECT: higher strength.

6 cl, 5 dwg

Description

The invention relates to the processing of metals by pressure, in particular to methods of stamping and rotational drawing shell especially thin-walled parts having the form of bodies of revolution.

A known method of manufacturing thin-walled axisymmetric vessels (see patent RU N2131787, IPC B21D 51/10, 22/16, publ. 06/20/1999), adopted as a prototype. The method includes the manufacture of the cylindrical part of the prefabricated vessel from a flat sheet stock, the cold stamping of the shaped bottom part of the prefabricated vessel from a flat sheet stock, the welding of the cylindrical part of the prefabricated vessel with a longitudinal seam, the preparation of the end edges of the cylindrical and bottom parts for welding, the welding of the bottom and cylindrical parts with an annular seam , rotational extraction of the cylindrical part of the vessel with simultaneous rolling of the welds and machining of technological allowances.

The method allows to produce thin-walled axisymmetric vessels with a shaped bottom, including a spherical shape, qualitative in geometric shape and surface roughness with minimal metal consumption.

To ensure minimal metal consumption in the manufacture of bottom and cylindrical parts, it is possible to use sheet metal of various thicknesses, while the thickness of sheet metal used for the bottom of the vessel is chosen equal to the thickness of the bottom of the vessel.

The disadvantages of the method taken as a prototype are:

1. The presence of welds even with their plastic deformation during rotational drawing reduces the mechanical properties of the metal in the weld zone.

2. The manufacture of vessels highly loaded during operation, such as small-sized rocket engine chambers, as described, requires a significant amount of additional work to ensure the quality of welded joints (heat treatment; x-ray inspection; magnetic flaw detection; hydraulic tests; flushing, etc.), which significantly increases the cost manufacturing technology of vessels.

3. The method does not allow the manufacture of vessels with a thickening inwardly of a portion of the cylindrical portion opposite the bottom.

4. To ensure the necessary strength in the weld zones with an annular seam, as a rule, it is necessary to perform thickenings, which makes the vessel heavier.

The present invention solves the problem of manufacturing a monoblock thin-walled axisymmetric shell, such as a chamber of a rocket engine of a small-sized rocket, consisting of a hollow cylindrical section and a hollow shaped bottom part, including a spherical shape, interconnected. In this case, the shaped bottom can mate with the hollow cylinder by means of a hollow truncated cone; an annular protrusion can be made on the outer surface of the bottom to form landing surfaces for attaching mating elements of the product; on the shaped bottom inside the shell, a hollow cylinder mated to the shaped bottom may be located; the end of the cylindrical section, opposite the shaped bottom part, can be made with a thickening inward.

The technical result obtained by the implementation of the invention is to manufacture a shell with the strength properties of the metal not less than specified for the heat-treated state in any section of the vessel.

The specified technical result is achieved by the fact that in the method of manufacturing thin-walled monoblock shells containing a hollow cylindrical section and a hollow shaped bottom part, including obtaining a hollow semi-finished product with a cylindrical part and a shaped bottom part, rotational drawing of a cylindrical section of a hollow semi-finished product and final machining by surface cutting with technological allowances , while the hollow semi-finished product is obtained by cold stamping from a flat sheet blank, otation extraction of the cylindrical part of the hollow prefabricated product is carried out in two or three stages with an acceptable degree of deformation, while for the manufacture of a flat sheet billet, cold-rolled sheet metal is used from the standard row, the thickness of which is selected taking into account the maximum thickness of the flat sheet billet for rotational drawing of a thin-walled cylindrical section defined according to the dependence tmax = t / (1-ε ₁ ) (1-ε ₂ ) (1-ε ₃ ), where ε ₁ ; ε ₂ ; ε ₃ is the allowable degree of deformation at stages 1, 2, and 3 of the rotational hood, while the thickness of the bottom of the shell is obtained by cutting the outer surface of the shaped bottom of the semi-finished product.

When cutting the outer surface of the shaped bottom part of the semi-finished product by cutting, an annular protrusion with landing surfaces is formed on it to attach the mating parts of the product.

The hollow prefabricated product is obtained with an internal cylindrical hollow protrusion in the center of its shaped bottom part by sequential molding and machining.

The hollow cylinder of the thin-walled shell is mated with its hollow shaped bottom part by means of a section in the form of a hollow truncated cone.

The hollow truncated cone of the shell is obtained by sequentially performing the operations of molding, cutting the outer surface and rotating the hood in 1-2 steps, observing the sine law, while the rotational hood of the section in the form of a hollow truncated cone is combined with the rotational hood of the cylindrical section.

At the end of the cylindrical section, opposite the shaped bottom part of the shell, an internal thickening is formed by rotational compression.

The thickness of the sheet stock is determined according to the dependence:

$$t\max =t/\left(\mathrm{one}-{\epsilon }_{\mathrm{one}}\right)\left(\mathrm{one}-{\epsilon }_2\right)\left(\mathrm{one}-{\epsilon }_3\right);\left(\text{one}\right)$$

Where

tmax is the permissible thickness of the sheet;

t is the thickness of the thin-walled cylindrical section of the shell;

ε ₁ ; ε ₂ ; ε ₃ - the permissible degree of deformation at 1, 2, 3 stages of rotational drawing.

In the case of an equal degree of deformation at all stages of a rotational drawing, the dependence takes the form:

$$t\max =t/{\left(\mathrm{one}-\epsilon \right)}^n;\left(\text{2}\right)$$

Where

n is the number of stages of rotational drawing.

Processing by cutting the outer surface of the semi-finished product allows you to form an annular protrusion with the seating surfaces for attaching the response elements of the product.

In the process of molding and subsequent processing by cutting in the central part of the shaped bottom of the shell, a hollow cylindrical protrusion can be formed inside the bottom part to accommodate product elements.

The coupling of the cylindrical section of the shell with the shaped bottom can be performed by the section in the form of a hollow truncated cone, obtained by sequentially performing the steps of forming, machining the outer surface and rotational drawing in one or two stages, observing the Sinus law. In this case, the rotational hood of the conical section is combined with the rotational hood of the cylindrical section.

At the end of the cylindrical section of the shell opposite the shaped bottom by rotational compression of the thick-walled inlet formed after the stages of rotational drawing of the cylindrical section, a section can be formed with a thickening inward for subsequent machining by cutting precise seating surfaces.

The use of a sheet blank with a thickness according to the above dependencies allows us to produce a hollow semi-finished product of small height, which significantly reduces the required number of stages of molding, heat treatment, trimming the end allowance, applying and removing coatings, etc.

The manufacture of a monoblock shell with a rotational hood of a cylindrical section in two or three stages ensures uniform mechanical characteristics of the metal in all sections.

Processing by cutting the outer surface of the shaped bottom part of the semi-finished product slightly increases the metal consumption for the manufacture of the shell, but it becomes possible to form an annular protrusion with landing surfaces on the outer surface of the shaped bottom part for mating parts without resorting to welding.

The use of a sheet blank with a thickness according to dependencies 1 or 2 allows rotational compression from a thick-walled technological lap formed at the stages of rotational drawing to obtain a thickening of the end cylindrical section of the vessel opposite the shaped bottom inward to create an allowance for machining by cutting precise landing surfaces. When implementing the method, it is also possible the formation of cold stamping and subsequent cutting of the hollow cylindrical section located inside the shaped bottom in its Central part to accommodate the elements of the product.

To increase the length of the shaped bottom part, the coupling of the cylindrical section and the shaped bottom can be performed by means of a hollow truncated cone, which is performed by molding, turning of the outer surface and rotational hood in one or two stages, observing the Sine law. In this case, the molding and rotation extraction of the conical section is combined with the molding and rotation extraction of the cylindrical section.

The proposed technical solution is illustrated by drawings, where in FIG. 1-5 shows the sequence of manufacture of a thin-walled axisymmetric shell with all the distinguishing features set forth in the description.

In FIG. 1 shows a semi-finished hollow product made by sequentially performing forming steps from a sheet blank of thickness t ₀ , consisting of a cylindrical section “A” with an inner diameter D and a shaped bottom part in the form of a sphere with radius R and a hollow truncated cone of length B ₀ with an inclination angle α of the generatrix α ₀ °, while the angle is selected from the condition of the rotational drawing of the conical and cylindrical sections simultaneously with a universal calibration roller for cylindrical parts.

A hollow cylindrical process with a diameter d was made inside the sphere.

In FIG. 2 shows a hollow prefabricated product after processing by cutting the outer surface of the bottom to wall thickness a; b; c, while leaving an annular protrusion with the thickness of the sheet stock for processing landing surfaces.

In FIG. 3 shows the shell after the first rotational drawing of the conical section of the bottom and the cylindrical section in dimensions a ₁ ; In ₁ ; α ₁ °; t ₁ ; A ₁ ; D to obtain an overlap of length L with the thickness of the sheet stock.

In FIG. 4 shows the shell after the second rotational drawing of the conical section of the bottom and the cylindrical section to the final dimensions a; AT; α °; t; A; D.

In FIG. 5 shows the shell after rotational compression inside a cylindrical section opposite the bottom, with dimensions D ₁ and e.

An example of using the proposed solution in the manufacture of a thin-walled shell (as in Fig. 5) with geometric dimensions: D = 150 mm; t = 0.9 mm; A = 203 mm; B = 60 mm; a = 0.9 mm; α ° = 7 °; b = 2.2 mm; D ₁ = 148 mm; e = 3.7 mm; R = 120 mm; d = 49 mm; c = 2 mm from ChS4VI maraging steel.

According to dependence 2, the maximum thickness of the sheet stock is determined, which can be used in the manufacture of the shell in two stages of rotational drawing with an acceptable degree of deformation = 0.6.

tmax = 0.9 / (1-0.6) ² = 5.6 mm.

From a standard row of cold-rolled sheet products, a sheet with a thickness of t ₀ = 5 mm is selected.

A circle with a diameter of 330 mm and sequential molding on a hydraulic press with a force of 400 tonnes is cut from a sheet blank. a hollow prefabricated product is made, as in FIG. 1 with geometric dimensions: D = 150 mm; A = 115 mm; the radius of the sphere R = 120 mm; with a hollow cylindrical process located inside a sphere with a diameter of d = 49 mm, with an angle of inclination of the generatrix of the conical section α ₀ ^о = 30 ° and a length B ₀ = 15 mm.

The outer surface of the shaped bottom of the semi-finished product is processed by cutting on a lathe, as in FIG. 2 in dimensions a ₀ = 3.7 mm; b = 2.2 mm; c = 2 mm, while leaving an annular protrusion with a thickness t ₀ necessary for processing the landing surfaces.

After machining, the conical section of the shaped bottom part and the cylindrical section of the semi-finished product are subjected to rotational drawing on a St40-22CNC rolling mill and a shell is obtained, as in FIG. 3 with dimensions a ₁ = 2.2 mm; α ₁ ° = 17 °; In ₁ = 25 mm; t ₁ = 2.2 mm; A ₁ = 177 mm; D = 150 mm and inlet L = 50 mm. The resulting shell is thermally processed to relieve stresses, then the second stage of rotational drawing is carried out on a rolling mill and a shell is obtained, as in FIG. 4 with dimensions a = 0.9 mm; α ° = 7 °; B = 60 mm; t = 0.9 mm; A = 203 mm; D = 150 mm and inlet L = 50 mm. Then, on the rolling mill, the end of the cylindrical section (inlet), opposite to the shaped bottom, is compressed and a shell is obtained, as in FIG. 5 with a diameter of the compressed section D ₁ = 148 mm and a wall thickness of e = 3.7 mm. The resulting shell is subjected to aging and final processing by cutting the seating surfaces.

Claims (6)

1. A method of manufacturing thin-walled monoblock shells containing a hollow cylindrical section and a hollow shaped bottom part, comprising obtaining a hollow semi-finished product with a cylindrical part and a shaped bottom part, a rotational hood of a cylindrical section of a hollow semi-finished product and final machining of surfaces with technological allowances, while a hollow semi-half is obtained cold stamping from a flat sheet billet, rotational hood of the cylindrical part of the hollow The sinter is carried out in two or three stages with an acceptable degree of deformation, while for the manufacture of a flat sheet billet, cold-rolled sheet metal is used from the standard row, the thickness of which is selected taking into account the maximum thickness of the flat sheet billet for rotational drawing of a thin-walled cylindrical section, determined by the dependence tmax = t / (1-ε ₁ ) (1-ε ₂ ) (1-ε ₃ ), where ε ₁ ; ε ₂ ; ε ₃ is the allowable degree of deformation at stages 1, 2, and 3 of the rotational hood, while the thickness of the bottom of the shell is obtained by cutting the outer surface of the shaped bottom of the semi-finished product. 2. The method according to p. 1, in which when machining the outer surface of the shaped bottom of the semi-finished product by cutting, an annular protrusion with landing surfaces is formed on it to attach the mating parts of the product. 3. The method according to p. 1, in which a hollow prefabricated product is obtained with an internal cylindrical hollow protrusion in the center of its shaped bottom part by sequential molding and cutting. 4. The method according to p. 1, in which the pairing of the hollow cylinder of a thin-walled shell with its hollow shaped bottom part through a section in the form of a hollow truncated cone. 5. The method according to claim 4, in which the hollow truncated cone of the shell is obtained by sequentially performing the steps of forming, cutting the outer surface and rotating the hood in 1-2 steps, observing the sinus law, while the rotational hood of the section in the form of a hollow truncated cone is combined with a rotational a hood of a cylindrical section. 6. The method according to p. 1, in which at the end of the cylindrical section opposite the shaped bottom part of the shell, an internal thickening is formed by rotational compression.

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