RU2037380C1 - Hot pressing method and apparatus - Google Patents

Abstract

FIELD: plastic working of material. SUBSTANCE: method involves direct heating of billet in die in fluidized bed of refractory powder by positioning gas-distributing grate and flame burner in lower part of die. Main evacuator embedded into press has auxiliary module-chambers mounted in fixed position on in-out table and flexible energy-carrier supply devices. EFFECT: increased efficiency, simplified construction and improved quality of pressed product. 3 cl, 1 tbl

Description

 The invention relates to the field of engineering, and more specifically to the technology of manufacturing products from powder and composite materials.

 A known method of hot isostatic pressing [1] in which the powder is enclosed in an airtight capsule, heated and pressed by transmitting pressure to the outer wall of the capsule with an isostatic medium, for example gas.

The specified method has several disadvantages:
significant costs for the manufacture of sealed capsules;
significant duration of cycles of heating, pressing and cooling of the capsules;
high complexity and uniqueness of the equipment used;
special requirements for the placement of equipment and significant specific areas.

 A known design of a hot pressing device in a vacuum [2] including a mold, a heater and a vacuum chamber integrated in the press.

The disadvantages of the known design are:
low productivity of equipment;
restriction of overall dimensions of the processed products;
insufficient accuracy of maintaining isothermal pressing conditions.

 The closest in technical essence to the proposed method is a method of hot isostatic pressing [2] in which a powder billet is loaded into a graphite mold and filled with flake graphite powder.

 The mold is placed in a furnace built into the press, it is heated and then the workpiece is pressed through a punch and the granular medium is pressed under isostatic pressure conditions.

The disadvantages of this method are:
low productivity of the process;
high level of manual labor;
relatively high specific energy consumption.

 The closest in technical essence is the device of the stamping block [3] including the main chamber built into the press and two auxiliary vacuum chambers connected to the main chamber by hermetic closures and designed one for loading, preheating the workpiece, the other for cooling the pressed part in inert gas.

 Successive pre-heating of the workpiece and cooling the pressed part in different chambers reduces the productivity of the equipment due to the significant length of time for pre-heating the workpiece.

 The aim of the invention is to increase the productivity of the process. This goal is achieved by the fact that in the known method and device, the heating and cooling of the product is carried out directly in the mold in a pseudo-boiling volume of inert refractory powder using plasma heating and as a plasma-forming medium of inert gas.

 In order to implement the process, a plasma torch and a gas distribution grill are mounted in the lower part of the mold, and the mold itself is mounted on a sliding table and flexible energy supply leads are connected. A sliding table with a mold and flexible energy supply is installed in a vacuum module chamber, which is connected through a technological vacuum shutter to the main chamber mounted in the press.

 In order to ensure difficult operating conditions of the mold (high temperature, pressure, change of heating and cooling modes), the walls of the mold are made water-cooled, the lining and structural elements are made of graphite and ceramic.

 The use of plasma heating and a pseudo-boiling medium provides the ability to fully automate the process of loading and unloading equipment with products from the mold, as well as isothermal and non-oxidizing conditions for pressing powder materials.

 Using the modular design of the auxiliary chamber with the placement of a mold permanently mounted on the drawer table, which is connected by flexible leads to the energy supply device, allows the press to be equipped with several auxiliary chamber-modules, which reduces the duration of the pressing process.

 In FIG. 1 presents a process flow diagram; in FIG. 2 device for hot isostatic, isothermal pressing of products from powder materials.

 The device (Fig. 2) includes an isothermal pressing press 1, a movable crosshead 2, a punch 3, a main vacuum chamber 4, an auxiliary chamber module 5, technological vacuum shutters 6, 7, a sliding table 8, a device 9 for flexible energy supply to the mold , mold 10, snap 11 with products.

 The mold 10 includes a water-cooled housing 12, a plasma torch 13, a gas distribution grid 14, a lining 15.

 The device operates as follows.

 Open the technological vacuum shutter 6 of one of the module-chambers 5 and extend the table 8 to the loading position with the mold 10 installed on it. Refractory inert powder is poured into the mold 10 and through the flexible energy supply device 9, a gas distribution grid 14 to the lower part the molds supply an inert gas in an amount necessary to create a pseudo-boiling medium. Next, the tooling 11 with the products is loaded into the mold 10 and the drawer 8 is moved to the auxiliary module-chamber 5. The process shutter 6 is closed, the plasma torch 13 is turned on and the products are heated to a predetermined pressing temperature. Then at the same time, the inert gas consumption is reduced and the chambers 4, 5 are evacuated to a predetermined vacuum, the technological vacuum shutter 7 is opened, and the table with the mold 10 is moved to the main chamber 4. Upon reaching the specified parameters (temperature, holding time, vacuum), the movable travel is activated the traverses 2 of the press 1 and through the granular medium by the punch 3 compress (compact) the product with a given strain rate. At the end of the pressing process, the traverse 2 is turned back on, the plasma heating is turned off, and the mold 10 is moved back to the auxiliary module chamber 5, the shutter 7 is closed, and a cooling gas medium is supplied to the gas distribution grid 14. At the same time, a second mold with products is moved from the other camera module 5 to the main chamber 4. Upon reaching the ambient temperature in the first module chamber 5 by the processed products, the shutter 6 is opened and the table 8 is advanced to the unloading position. Tooling 11 with products is unloaded, the next tooling with products is loaded, and then the cycle repeats.

 PRI me R. Technical processing of samples with a diameter of 15 mm and a length of 60 mm was carried out from pre-sintered powder material of grade Zh-6.3 in an experimental setup including a hydraulic press, lower and upper support plates, a mold with an integrated plasma torch, a gas distribution grid, a feed system and energy outlet, punch, tight movable seal, equipment.

 Installation works as follows. The working volume of the mold is filled with refractory powder, the energy carriers (electric power, water, inert gas) are connected, the vacuum pump and the outlet of the gas medium are fed into the gas distribution grid and a pseudo-boiling volume of powder is created, the equipment with the samples is loaded into the working cavity of the mold matrix turn off the gas supply. Next, mount the punch, the movable seal. The mold is mounted on the lower base plate of the hydraulic press.

 The table shows the mechanical properties of the samples processed in the experimental setup in comparison with the mechanical properties of powder samples made by traditional technology (cold pressing + sintering).

Using the proposed method of isostatic and isothermal pressing and a device for its implementation provides, in comparison with known methods, the following advantages:
the possibility of obtaining increased strength properties of powder billets due to isostatic and isothermal pressing;
increasing process productivity by reducing processing time and the possibility of complete automation and mechanization of the process.

Claims (3)

 1. The method of hot pressing, including placing the tool with the products in the mold, feeding it the pressure medium in the form of a refractory inert powder, heating to the pressing temperature, quasi-isostatic loading, subsequent cooling and unloading of the tool with products from the mold, characterized in that, in order to increase productivity, the pressure-transmitting medium is fed into the mold before placing equipment with it in it and a pseudo-boiling volume of inert powder is formed by feeding of inert gas, then when gas is arranged to snap-products, are heated using a plasma and plasma gas heating and loading is carried out under isothermal conditions.  2. A device for hot pressing, containing the main chamber, built into the press, and auxiliary chambers for loading and unloading with a sliding table, connected to the main chamber through airtight shutters, characterized in that, in order to increase productivity, it is equipped with an inert gas supply unit , the main chamber is made with a mold with a gas distribution grill and a plasma torch mounted under the grill in the lower part of the mold, which is stationary mounted on a drawer, and the working cavity is pre the ss-forms are communicated through a grate, a plasma torch and a flexible supply with an inert gas supply unit, and the mold and the burner are made water-cooled.  3. The device according to p. 2, characterized in that it is equipped with several molds and module chambers for their placement and alternate work.

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