RU2412776C1 - Method of assembling prefabricated structures made from refractory metals - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be sued in producing permanent joints, primarily, from homogeneous and refractory materials by riveting. Primary element and sheet to be riveted are assembled. Through bored are drilled therein. Rivets are fitted in drilled bores. Tight riveting seam is formed by fusing rivet heads in inert atmosphere or vacuum. Depth of fusion makes 0.2…0.4 of riveted sheet thickness. Spacing of rivets makes 3…15 of rivet diametre. Indent from assembly edge makes, at least, two diametres of rivet.

EFFECT: improved operating performances and longer lifer.

2 dwg, 1 ex

Description

The present invention relates to the field of mechanical engineering and can be used to obtain one-piece joints mainly from homogeneous and heterogeneous refractory metal materials by riveting.

A known method of producing rivets of rivets with electric heating, in which an electric current is passed through a rivet of homogeneous and dissimilar metals, followed by the shaping of the locking head (German patent DE 914044, 1954), analogue.

The disadvantages of this method are the difficulty of obtaining tight joints, low strength riveted joints.

There is a method of producing rivets, in which, after assembling the design and installing rivets, the rivet head is melted to form a weld pool to an arbitrary depth (I. Pokhodnya, AM Suptel, V. N. Shlepakov “Flux-cored wire welding.” Kiev, from "Science Dumka", 1972), prototype.

The disadvantages of this method of connection are the possibility of the formation of leaks and low structural strength.

There is a method of obtaining a design using electric rivets, which consists in assembling the products to be joined and fusing them with an arc to form an electric rivet, followed by rolling the electric rivet head (SU 1336375, 1985).

The disadvantages of this method are the low performance properties of compounds of most heterogeneous refractory metallic materials.

A method for producing prefabricated structures from homogeneous or dissimilar metal materials is proposed, including assembling the main element and the riveted sheet, making through holes in them, installing rivets in the holes and forming a sealed rivet seam.

The objective of the invention is to increase the operational properties and service life of riveted structures from refractory homogeneous and heterogeneous metal materials.

The technical result of the invention is to obtain a sealed riveted structure of refractory metals and an increase in the strength of the joints.

The specified technical result is achieved by the fact that the formation of a sealed rivet seam is performed by reflowing the rivet heads in an inert medium or vacuum with the formation of a common bath of molten metal to a depth of 0.2 ... 0.4 of the thickness of the riveted sheet in increments of 3 ... 15 of the diameter of the rivet and indent from the edges of the assembly (overlapping of the main element and the riveted sheet) at a distance of at least 2 diameters of the rivet.

The proposed method is illustrated by the following graphic images, in which Fig. 1 shows a diagram of a riveted joint (the dotted line shows the rivet rod before reflow); figure 2 - arrangement of several rivets in a row.

The need for flashing rivets in the process of making joints from refractory metal materials is due to the fact that standard riveting schemes with mechanical formation of the rivet head require preheating of the product to a temperature of 300-600 ° C, and rivets to 500-1000 ° C. This leads to the high complexity of manufacturing the product, low productivity and the possibility of cracking in the rivets at the stage of cooling the structure (especially in the case of the manufacture of compounds from dissimilar materials). At the same time, mechanical shock loads applied to obtain riveted joints can also lead to cracking in rivets.

To eliminate the above disadvantages, the proposed method for producing riveted joints was developed, which is carried out as follows. Parts made of refractory homogeneous or dissimilar metal materials are assembled and holes for rivets are assembled. In the holes from the side of the back riveted (sealed) sheet, pre-made rivets are installed, as a rule, from refractory metals (for example, molybdenum or tungsten) (Fig. 1) and the assembled structure is installed in a welding device.

A sheet of refractory metal, a profile, etc. can act as the main structural element.

The protruding part of the rivet (dashed line in FIG. 1) is fused with a concentrated energy source in an inert medium or vacuum to form a common bath of molten metal of the rivet and the riveted sheet to a depth of 0.2 ... 0.4 of the thickness of the riveted sheet. In this case, complete sealing of the connection is ensured by the formation of a bath of molten metal around the entire perimeter of the rivet head. When the power source is turned off, the riveted joint can be cooled in air, when inert gas is blown from the burner nozzle or in vacuum. Then, in the same manner, the following compound is obtained.

As a concentrated source of energy, any welding heating source can be used, for example, a free or compressed arc burning in an inert gas; electron beam in vacuum, laser beam in vacuum or inert gas, etc.

The quality of the riveted joint depends on the compression ratio of the sealed sheet and the main element, which is ensured by residual welding deformation after cooling the rivet head. To obtain a sealed structure, the required amount of compression force is determined by the pitch of the rivets. Experimental studies to determine the optimal pitch of rivets have shown that it should be 3 ... 15 of the diameter of the rivet. At large values of the pitch, the operational properties of riveted structures deteriorate.

Example.

A prefabricated structure was made consisting of a welded sealed muffle with a diameter of 460 mm, a height of 840 mm and a wall thickness of 1.5 mm, made of sheets of vacuum-fused molybdenum alloy grade TSM-7, and supporting shelves - from molybdenum posts with a cross section of 18 × 18 mm, obtained by the method powder metallurgy.

The manufacture of the product was carried out as follows. The muffle with the staffs was assembled together, holes 4.1 mm in diameter were drilled for rivets in 40 mm increments. After that, rivets with a diameter of 4 mm from a TSM-7 molybdenum alloy were inserted into the holes from the side of the racks. The assembled structure was mounted on a faceplate with a horizontal axis of rotation and rivets were sequentially melted using an argon-arc torch with a non-consumable electrode of the EVL-10 brand, 3 mm in diameter. The torch was supplied from a welding source VSVU-630. Rivets were fused in the following modes:

- arc voltage - 12 V;

- arc current - 180-210 A;

- argon consumption 12 l / min.

The penetration depth on the muffle side was 0.5 mm (0.3 muffle wall thickness).

The resulting design was monitored for the absence of cracks at a 10-fold increase in rivets and in the product, as well as for tightness using the kerosene test method. The penetration depth of the top sheet was determined by optical metallography on samples at the stage of selecting the rivet fusion mode.

Claims (1)

A method of manufacturing welded riveted structures from homogeneous or heterogeneous refractory metal materials, including assembling the main element and the riveted sheet, making through holes in them, installing rivets in the holes and forming a sealed rivet seam, characterized in that the sealed rivet seam is formed by fusing the rivet heads in an inert medium or vacuum with the formation of a common bath of molten metal to a depth of 0.2 ... 0.4 of the thickness of the riveted sheet with a step of rivets 3 ... 15 diameter rivets and assembly and offset from the edge by a distance not less than two diameters of the rivet.

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