RU2635980C1 - Method to produce thin-walled axisymmetric shells - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: shell elements are manufactured separately and their final hardening heat treatment is carried out. There are mounting surfaces at ends of a first element, and are made enclosing the seat surfaces, and at second and third elements-with enclosing mounting surfaces with dimensions providing guaranteed interference and connection tightness. At that the connection of shell elements is implemented with heating of the first element with enclosing mounting surfaces up to temperature providing preservation of strength properties of alloy the element is made of, and guaranteed exceeding of the dimensions of enclosing mounting surfaces of the first element above the reciprocal dimensions of the enclosing mounting surfaces of the second and third elements.

EFFECT: technological capabilities and increased geometric accuracy of the shells.

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Description

The invention relates to mechanical engineering and can be used in the manufacture of high-strength alloys of thin-walled shells of rocket engines with an internal diameter of more than 120 mm

In mechanical engineering, there is a known method of manufacturing a one-piece assembly of two parts, including cutting and hardening heat treatment of the first part with the formation of a cylindrical landing surface of the “shaft” type, cutting and hardening heat treatment of the second part with the formation of a cylindrical landing surface, of the “hole” type, with a nominal diameter smaller than the diameter of the “shaft” of the first part, heating the second part to a temperature slightly lower than the low tempering temperature of the material from which it is made level, the assembly of the first and second parts along the seating surfaces and cooling the assembly to normal temperature, while the maximum values of shear resistance by axial force are obtained when performing a hot fit with a high tightness. The method is effectively used to connect thick-walled, hard parts (Reshetov D.N., "Machine parts", Engineering, 1964, pp. 91-93).

The disadvantages of the analogue are:

1. For the connection of thin-walled parts, large tightnesses, providing maximum shear resistance, are unacceptable, including due to the rapid cooling of the enclosing part during assembly.

2. The connection of thin-walled parts with low interference reduces the pressure in the connection and, as a result, the shear resistance is reduced. To increase the shear resistance, it is necessary to increase the length of the seating surfaces, which significantly increases the consumption of metal, and also (with a large length of the seating surfaces) makes the connection impossible.

A known method of manufacturing, with a minimum consumption of metal, of a thin-walled axisymmetric vessel of complex shape, consisting of a cylindrical element connected to a curved bottom element, including separate production from sheet blanks of two simple, compared with a thin-walled axisymmetric shell, elements - a cylindrical element and a bottom element, manufacturing of one-piece axisymmetric semi-finished product of complex shape by butt welding with an annular seam of cylindrical and bottom elements, thermo the work of the semi-finished product to relieve stresses obtained during welding, quality control of the weld, rotational drawing of the cylindrical element of the semi-finished product together with the weld to obtain a thin-walled shell and final processing of the shell (patent RU 2131787, IPC B21D 51/10, B21D 22/16, publ. 06/20/1999). The method adopted for the prototype.

The disadvantages of the prototype are:

1. The strength characteristics of the metal in the weld zone is less than in the base metal by 10 ... 15%.

2. After welding, it is necessary to carry out heat treatment to relieve stresses, as well as assess the quality of the weld of critical semi-finished products by X-ray inspection, magnetic flaw detection, hydro- or pneumatic tests.

3. In the manufacture by this method of shells, such as a thin-walled chamber of a rocket engine of a small-sized rocket, from high-strength alloys, it must be hardened by heat treatment, while it is necessary to ensure high geometric accuracy of the shell.

To obtain high geometric accuracy (deviation from roundness and straightness), the shells are thermally corrected:

- shells of high-strength steel alloys hardened by quenching followed by martensitic aging during quenching on an austenitic mandrel;

- shells of high-strength steel alloys hardened by quenching with tempering during cooling after quenching on an expandable mandrel, while assembly of the shell with the mandrel should be carried out in a short period of time.

Shells with a complex inner surface are not always heat-treated using a mandrel for thermal dressing, therefore, the heat treatment of such shells is carried out in a free state, while the shells acquire significant deviations from roundness and straightness, some of the shells are rejected.

The present invention solves the problem of manufacturing an integral thin-walled axisymmetric shell with a complex inner surface, such as the housing of a propulsion system of a small-sized rocket, consisting of 2 ... 3 elements made of high-strength alloys.

The technical result is the provision of a given geometric accuracy of a thin-walled axisymmetric shell of complex shape. The possibility of manufacturing an axisymmetric shell of complex shape from elements made of different high-strength alloys with different mechanical characteristics (σ _B ; σ ₀₂ ; σ, etc.).

The specified technical result is achieved by the fact that in the method of manufacturing a thin-walled axisymmetric shell with a complex inner surface, including the separate manufacture of several simple elements and the subsequent connection of separately manufactured shell elements into an integral block thin-walled axisymmetric shell, the new fact is that the shell elements are made with the final reinforcing heat treatment and with landing surfaces at the ends, at the first element - with covering surfaces, and at the second (second and third) element - with mating surfaces responding to them with dimensions that provide guaranteed tightness and tightness in the connection, and the connection of the shell elements into an integral block structure is carried out with heating of the first element with covering landing surfaces to a temperature that ensures preservation strength properties of the alloy of which the element is made, and guaranteed excess of the dimensions of the surrounding seating surfaces of the first element over the response and the dimensions of the seating surfaces covered by the second (second and third) element.

The seating surfaces of the elements are made from a combination of annular protrusions and grooves, when the annular protrusions and grooves of the female surface of the first element correspond to their annular grooves and protrusions of the female surface of the second (second and third) element.

When using elements made of several parts, the elements are connected into an integral shell with angular fixation of the elements relative to each other.

The manufacture of a thin-walled shell of complex shape in the form of an integral block structure of two, three elements (including consisting of several parts), previously thermally hardened and mechanically machined, by interconnecting along the seating surfaces with an interference fit, can significantly simplify the manufacturing technology of a thin-walled shell of complex shape and increase its geometric accuracy.

The manufacture of the first covering element of the seating surfaces in the form of a combination of annular protrusions and grooves, and the second (second and third) elements of the covering seating surfaces in the form of a combination of annular grooves and protrusions allows you to reduce the guaranteed interference fit to a value that ensures the tightness of the shell, while resisting axial shear the force acting on the joint will be the sum of the force obtained from the assembly of the elements with an interference fit and the strain resistance of the annular protrusions (shear ).

The manufacture of elements is thermally hardened, to obtain the optimal strength properties of the metal, each element can simplify the manufacture of shell complex shape, because the heat treatment technology and the mandrels used are greatly simplified.

The proposed technical solution is illustrated by drawings, where:

- in FIG. 1 shows a thin-walled element 1 made of several parts with covering seating surfaces at the ends of the element from a combination of annular protrusions and grooves with sizes D, D ₁ , L and H and with an inner diameter ∅;

- in FIG. 2 shows a thin-walled element 2 made of several parts with inner diameters ∅ and ∅ ₁ and with covered seating surfaces at the end of the element from a combination of annular protrusions and grooves with dimensions d, d ₁ , l and h;

- in FIG. 3 shows a thin-walled element 3 made of several parts with inner diameters ∅ ₁ and ∅ and with covered seating surfaces at the end of the element from a combination of annular protrusions and grooves with dimensions d, d ₁ , l and h;

- in FIG. 4 shows a thin-walled shell of complex shape obtained by assembly of elements 1, 2, 3.

An example of using the proposed solution

It is required to produce a thin-walled shell of complex shape consisting of three elements, as in FIG. 4: element 1 - bottom assembly; element 2 - the starting chamber assembly; element 3 - the marching chamber assembly. Elements are made separately.

An element 1 is made with internal cavities with a diameter of ∅ = 194 mm. If structurally necessary, parts A and B are welded to the outer bottom surface. After welding and preliminary machining, element 1 is subjected to hardening heat treatment in the form of tempering with tempering. After holding at the quenching temperature, element 1 is assembled with an expanding mandrel in diameter ∅ and quickly cooled to normal temperature, while the diameter ∅ acquires a deviation from roundness of ≤0.1 mm. Make a vacation. After tempering, they are machined by cutting covering the seating surfaces at the ends in the form of a combination of annular protrusions and grooves with dimensions D = 196.1 ^+0.1 mm; D ₁ = 196.5 ^+0.1 mm; L = ^4-0.03 mm; H = 4 ^{+0 03} mm.

Successive plastic deformation operations (cold stamping, rotary hood); intermediate heat treatment for stress relieving, cutting, etc., from sheet blanks a thin-walled launch chamber with inner diameters ∅ = 194 mm and ∅ ₁ = 190 mm with a length of 380 mm and a thin-walled march chamber with inner diameters ∅ = 194 mm and ∅ ₁ = are made 190 mm, length 620 mm. If structurally necessary, parts B, D and D are welded to the outer surface of the chambers in the zone of diameters ∅ _1. After welding and preliminary processing by cutting, elements 2 and 3 are subjected to hardening heat treatment in the form of tempering with tempering. After exposure to the quenching temperature, the elements 2 and 3 are assembled with expanding mandrels in diameter ∅ and quickly cooled to normal temperature, while the diameter ∅ acquires a deviation from roundness of ≤0.15 mm, a deviation from straightness of ≤0.3 mm along the entire length of the surface with diameter ∅. Make a vacation. After tempering is treated by cutting the male seating surfaces at the ends in the form of a combination of circumferential grooves and projections with sizes d = 196,8 _-0.1 mm; d ₁ = 196.4 _-0.1 mm; h = _4-0.03 mm; d = 4 ^+0.03 mm.

Based on the dimensions of the seating surfaces of the elements 1, 2 and 3, the minimum guaranteed interference fit in the connection will be:

Δ _min = (D _1max -d _min ) = (196.5 + 0.1) - (196.8-0.1) = - 0.1 mm;

Δ _min = (D _max -d _1min ) = (196.1 + 0.1) - (196.4-0.1) = - 0.1 mm.

Element 1 is heated to a temperature of (330-350) ° C, while the surrounding surfaces increase by (0.8-0.9) mm. Elements 2 and 3 are installed in element 1. If elements 2 and 3 are welded on the elements, elements 2 and 3 are fixed relative to element 1 at the corners. The element 1 is cooled to normal temperature and a non-separable thin-walled shell of complex shape is obtained, as in FIG. 4. Make the final processing by cutting the shell according to the requirements of the CD.

Claims (3)

1. A method of manufacturing a thin-walled axisymmetric shell with a complex inner surface, including the separate manufacture of shell elements and their subsequent connection in an integral block thin-walled axisymmetric shell, characterized in that when the separate manufacture of shell elements carry out their final hardening heat treatment, while at the ends of the first element perform covering landing surfaces, and at the ends of the second and third element, the covered surfaces mating with them which provide guaranteed tightness and tightness in the connection, moreover, the connection of the shell elements into an integral block thin-walled axisymmetric shell is carried out by heating the first element with the surrounding seating surfaces to a temperature that ensures the strength properties of the alloy of which the element is made, and guaranteed exceeding the dimensions of the surrounding landing surfaces the first element above the dimensions of the covered seating surfaces of the second and third of elements. 2. The method according to p. 1, characterized in that the seating surfaces of the elements are in the form of annular protrusions and grooves, and the annular protrusions and grooves of the female surface of the first element are made corresponding to their corresponding ring grooves and protrusions of the male surface of the second and third elements. 3. The method according to p. 1 or 2, characterized in that the shell elements are made of several parts, and the connection of these elements into an integral block thin-walled axisymmetric shell is carried out with their angular fixation relative to each other.

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