RU2367541C1 - Manufacturing method of products made of powder materials - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: from exothermal reactionary charge of initial components it is pressed charge briquette and it is located in mould in inert powder atmosphere from friable heat insulator. On surface of charge briquette it is laid gas permeable insulating barrier, in which by whole surface there are implemented openings. Pitch between centers of openings not less than three radiuses of these openings. On insulating barrier it is laid additionally layer of charge, combustion temperature of which is equal or less than combustion temperature of charge briquette. In additional layer of charge there are installed two or more initiating devices and it is initiated combustion reaction, herewith hot products of synthesis through openings in gas permeable insulating barrier it is inflamed charge briquette. After what it is implemented pressing, extraction of product from mould and cooling.

EFFECT: increasing of outlet and quality of yield, ability of increasing of overall dimensions of objective items.

2 cl, 1 tbl, 1 dwg

Description

The invention relates to the field of powder metallurgy, and more particularly to a method for manufacturing products from powder materials in a combustion mode (self-propagating high-temperature synthesis of SHS). In practice, products manufactured by the SHS method are widely used in metallurgy, mechanical engineering, aircraft manufacturing, and aerospace engineering. Products that can be obtained by the proposed method: rolls, stamp elements, processing tools, large-sized sandblasting nozzles, protective coatings, pump parts, etc.

A known method of producing products from powder materials, including preparing an exothermic powder mixture, pressing the mixture into a briquette, placing it in a heat-insulating porous shell and in a matrix, initiating a combustion reaction and hot pressing of the combustion products together with the shell (RU 2060866 C16B 22 F3 / 23, B22F 3/14, 1996.05.27).

A known method of producing products from powder materials, including the preparation of an exothermic reaction mixture of the starting components, pressing the mixture in the form of a briquette, placing it in a mold in an inert powder medium from a loose heat insulator, bringing it to the surface of the briquette through the holes in the mold design of the initiating device, consisting of current-carrying wires and a spiral, ignition of the briquette by passing current through the igniter, after the end of the process of burning the mixture, pressing hot synthesis products and subsequent product recovery (A.P. Amosov, I.P. Borovinskaya, A.G. Merzhanov. Powder technology of self-propagating high-temperature synthesis of materials. Moscow, 2007, p. 220-223). The specified source is taken as a prototype.

The disadvantages of these known solutions is the presence of one initiating device (arson) located on the surface of the charge briquette, which does not allow to obtain fully isothermal pressing conditions. As a result, the resulting products have different densities in different parts. These defects are especially noticeable on large products. It is not possible to increase the number of arson in the briquette due to the increase in temperature caused by the encounter of combustion waves emanating from each arson, and as a result, the formation of defects in these places: chips, cracks and thermal stresses. In addition, due to the presence of one arson, the combustion time of the charge briquette increases, and by the time the pressing starts, the briquette zone located at the arson has time to cool. Such non-isothermal pressing conditions lead to different density of the material and lower quality and yield.

The technical result of the invention is to improve the quality and yield of the product, as well as the ability to obtain target products of large dimensions.

The technical result is achieved by the fact that the method of manufacturing products from powder materials involves preparing an exothermic reaction mixture of the starting components, pressing the charge briquette, placing it in the mold in an inert powder medium from a loose heat insulator, bringing it to the surface of the briquette through holes in the structure of the initiator mold a device consisting of current-carrying wires and a spiral, igniting the briquette by passing current through the igniter, after the end of the process pressing the mixture of hot synthesis products, removing the product from the mold and cooling, laying a gas-permeable insulating layer on the charge briquette, in which holes are made along its entire surface with a step between their centers equal to at least three radii of these holes to the insulating the layer is additionally laid with a charge mixture, the combustion temperature of which is equal to or higher than the combustion temperature of the charge briquette, two or more initiating devices are installed in the specified additional charge layer, they initiate combustion reaction in an additional layer, hot products of synthesis of which ignite the charge briquette through holes in a gas-permeable insulating layer. The holes are of any geometric shape with a maximum size of 4-20 mm, and for holes made in the form of a circle with a radius of 2-10 mm.

The invention is illustrated by the diagram shown in the drawing, where 1 is the mold matrix, 2 layer is bulk material, 3 is a charge briquette, 4 is a gas-permeable insulating layer with holes, 5 is an additional charge layer, 6 is an initiating device, 7 is a punch . Section AA shows the installation locations of the initiating devices (arson), section BB shows the location of the holes in the gas-permeable layer through which the charge briquette is ignited.

The method is as follows.

In a mold 1 located on the press, a compressed charge briquette 3 of an exothermic mixture is placed on a layer of granular material 2 according to the shape of a given product, a gas-permeable insulation layer 4 is laid on the charge briquette, in which openings are made along its entire surface with a pitch of at least three radii between hole centers, an additional layer 5 of a charge is laid on the insulating layer, the combustion temperature of which is equal to or higher than the combustion temperature of the charge briquette. Two or more initiating devices 6 are installed in the indicated additional charge layer, they are filled with bulk material 2 (sand) from above and the mold is closed with a punch 7. A current is applied to all initiating devices installed in the additional charge layer, the combustion reaction is initiated in the layer, and charge briquette is ignited by hot synthesis products, through openings in a gas-permeable insulating layer. After the combustion of the charge briquette is completed, hot deformation is started. The finished product is removed from the mold, cooled, and then additional layers are separated mechanically, if necessary by grinding.

The ignition of the charge briquette occurs through a large number of holes in the gas-permeable layer. Moreover, this charge layer additionally heats the charge briquette, due to which the time of briquette combustion is reduced, and defects from arsons remain in the gas-permeable layer. Due to this, pressing occurs in isothermal conditions, which is especially important when obtaining large-sized products.

Thus, during the burning of a briquette through holes in a gas-permeable layer, the number of flash points increases many times, and defects from counterpropagating combustion waves are minimized. Installed two or more arson on an additional layer of the charge reduces the combustion time of the charge briquette.

Example 1

For the manufacture of carbide billets with a diameter of 240 mm and a height of 50 mm, which are used as die tooling elements, an exothermic mixture of the following composition, wt.%: Ti 88.0; pre-mixed in a ball mixer was used for a charge briquette; B 12.0 (mixture I), the burning temperature of which is 1600 ° C, for an additional layer an exothermic mixture of the following composition, wt.%: (Ti + C) 80.0 and Ni 20.0 (mixture II), the burning temperature of which is 2800 ° C. A mixture of briquette weighing 10,000 g by cold pressing was prepared from mixture 1. As thermal insulation used sand. Sand was poured into a metal mold 1 with a diameter of 250 mm, placed on a press, and a charge briquette 3 was placed on it, a gas-permeable insulating layer 4 was laid on the charge briquette, in which holes with a radius of 2.5 mm and a pitch of 7.5 mm were made over its entire surface between the centers of the holes. A layer 5 of a mixture of mixture II (1500 g) was placed on it, the combustion temperature of which is 2800 ° C. In this additional charge layer, four initiating devices 6 were installed (section A-A in the drawing), consisting of a nichrome spiral and current-carrying wires passed through special holes in the mold. A sand layer 2 is placed on top of the additional layer and the mold is closed with a punch 7. Current is supplied to nichrome spirals 6, ignite mixture II and ignite the charge briquette 3 through the holes in the gas-permeable layer 4. The pressing pressure was 2000 kg / cm. After pressing, the briquette is removed from the mold, cooled, and then the workpiece is separated from the additional and insulating layers.

Example 2

For the manufacture of a roll of carbide material with an outer diameter of 205 mm and an inner diameter of 130 mm, a height of 50 mm, an exothermic mixture of the following composition, wt.%: (Ti + C) 70.0; Ni 22.0; Mo 8.0 (mixture I), the burning temperature of which is 1800 ° C, for an additional layer an exothermic mixture of the following composition, wt.%: (Ti + 2B) 70.0 and Cu 30.0 (mixture II), the burning temperature of which is 1800 ° C. The gas-permeable layer is prepared in the form of a ring with a diameter of 205 mm, an inner diameter of 130 mm. Holes with a maximum size of 8 mm are placed on the surface of the layer in increments of 12 mm. In an additional layer (mixture II) set three arson. Further, as in example 1.

The table shows the comparative characteristics of the product rolls and stamp elements obtained by the prototype and the claimed method. It can be seen that the proposed method makes it possible to obtain products with higher physical and mechanical properties, in addition, the yield of suitable products also increases by 10-20%.

Table Product Density, g / cm ³ Hardness, ed. Hra Bending Strength, MPa Max deviation of the height of the product from a given value, mm The element of the stamp obtained by the prototype 5.7-5.8 86.0-87.5 900-980 +5 -5 The stamp element obtained by the claimed method 5.9-6.0 89.5-90.0 1100-1200 +1 -0.5 Prototype roll 4.4-4.5 84.0-86.0 760-850 +4 -3 The roll obtained by the claimed method 4.65 87.0-88.0 950-1000 + 0.5-0.5

Claims (2)

1. A method of manufacturing products from powder materials, including the preparation of an exothermic reaction mixture of the starting components, pressing a charge briquette, placing it in a mold in an inert powder medium from a loose heat insulator, initiating a combustion reaction, pressing hot synthesis products, removing the product from the mold and cooling, characterized in that a gas-permeable insulating layer is laid on the charge briquette, in which openings are made over the entire surface with a pitch between their centers, at least three radii of these openings, an additional charge layer is laid on the insulating layer, the combustion temperature of which is equal to or higher than the combustion temperature of the charge briquette, two or more initiating devices are installed in the additional charge layer and initiate the combustion reaction, while the hot fusion products through the holes in a gas-permeable insulating layer ignites the charge briquette. 2. The method according to claim 1, characterized in that the holes are made in the form of a circle with a radius of 2-10 mm

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