RU2194595C2 - Method for forging liquid metal and impulse treating of it so called "impulse die forging" - Google Patents

Abstract

FIELD: foundry. SUBSTANCE: method comprises steps of placing billet to melting chamber for heating billet in order to create melt bath; registering time moment of billet melting by means of pickup; shifting die set placed lower than billet towards moving melt; after contact of die set with billet acting upon melt by gas pressure, by pressing and forging efforts through punch; applying upon melt mechanical and electromagnetic oscillations. EFFECT: possibility for making especially complex-shape articles of any metals and also metal-non-metal type composite articles. 8 dwg

Description

 The invention relates to the field of foundry and can be used for casting any metals, including refractory and chemically active. The closest technical solution is the method of molding with crystallization under pressure [1, (pp. 344-344)], in which pressure is used as a factor in the effective effect on the solidification and the processes occurring during it - shrinkage, gas evolution, cracking, segregation, including melt preparation in a separate melting chamber, the movement of the melt from the melting chamber using a filling device into a stamp, followed by pressing it using a piston or punch. Injection crystallization casting methods provide a high density of castings close to the density of deformable workpieces and a fairly uniform structure.

 As the closest analogue to the method of stamping liquid metal, a method is adopted that includes obtaining a melt in the melted workpiece, moving it into a stamp, moving the stamp towards the moving melt until it comes into contact with the workpiece, subsequent exposure to high pressure (application SU 96121304, class B 22 D 18 / 2, published on January 20, 1999) - [2]. These methods have found application in the manufacture of valves, connecting rods, flanges, gears, pistons, cylinder blocks, die inserts and molds.

 The aim of the invention is to increase the efficiency of use and expand technical capabilities by obtaining products of a particularly complex shape from any metals, including refractory and chemically active, as well as composite metal-non-metal products.

 This goal is achieved by the fact that in the known method of stamping liquid metal, including obtaining a melt in the melted workpiece, moving it into a stamp, moving the stamp towards the moving melt until it comes into contact with the workpiece, the subsequent exposure to it under increased pressure, characterized in that the movement of the stamp begins in the melting time of the workpiece, which is fixed by a sensor, after which the melt is subjected to gas pressure, pressing and forging pressure through the punch, while crystallizing The states impose mechanical and electromagnetic vibrations on the melt.

 The proposed method implements the installation shown in figures 1 and 2. The installation includes a melting chamber 1, which houses a remelted metal billet 2, when heated by a heater 3 (plasma torch, electron beam gun, electric arc, electrical resistance, inductor, etc. d.) a molten bath 4 is formed. When the melt 4 reaches the lower part of the workpiece 2, it is poured into a stamp 5, which is at a certain distance below the workpiece 2. At the moment of penetration of the workpiece, which is recorded by the sensor 6, begins moving the die 5 towards the moving melt 4 until it comes into contact with the workpiece 2. Then, the metal melt 4 can be affected by gas pressure 7 entering the upper melting chamber 1, low-frequency and high-frequency vibrations from vibrating devices 8 and 9, and electromagnetic fields due to inductors 10 and 11, and in addition, by pressing due to the punches 12, as well as by forging due to the strikers 13. The lower chamber 14 presses and squeezes from the upper chamber 1 due to the pneumatic cylinders 15 and 16.

 Taking certain dimensions of the installation and power parameters of energy carriers, we will calculate the forces of action on the metal.

 - Find max. metal velocity Vm at the end of the fall.

 The free fall distance of the metal is h = 0.3 m.

 Vm = √2g • h = 2.4 m / s.

 - Find max. piston speed Vn.

The diameter of the power piston - D = 0.12 m
Piston mileage - l = 0.2 m
Mass of the piston - m = 20 kg
Gas pressure on the piston - P = 1 MPa
Vn = √P • π • D ² • 1/4 • m; S = π • R ² = π • D ^2/4; Vn = 11 m / s.

 With a free fall of the metal and oncoming movement of the stamp, for the given parameters, the installation provides an average speed of filling the stamp with metal equal to 6.7 m / s. This speed of the metal corresponds to the speed of filling the metal stamp during classical injection molding. But in the proposed method does not require narrowing the flow of metal feeders, which degrade the final density of the castings obtained by this method.

We find the pressure Pp of the impact on the crystallizing metal transmitted through the punch:
punch diameter Dn = 0.01 m;
Pp = P • D ² / D ² n;
Pp = 144 MPa = 1440 at.

 When casting with crystallization under pressure on a liquid metal, the exposure pressure is 100 ÷ 200 MPa. Therefore, these installation parameters provide the average mode of classical liquid stamping.

We find the pressure Rd of the impact on the crystallizing metal transmitted through the punch when the hammer strikes it:
mileage hn of the punch to a stop - 0.005 m;
striker speed Vb = 20 m / s;
striker mass mb = 5 kg.

- Impulse of force I acting on the punch:
I = mb • Vb = 5 kg • 20 m / s = 100 N • s.

- Punch braking time:
Δt = 2 • hn / Vб = 5 • 10 ^-4 s.

, действующая на металл:
F= I/Δt =2•10⁵Н;
Рд = 4•F/π•D²n = 4•2•10⁵/3,14•(10^-2)² = 2,6•10⁹ = 2,6 ГПа = 26000 ат.- Average net power

acting on metal:
F = I / Δt = 2 • 10 ⁵ N;
Rd = 4 • F / π • D ² n = 4 • 2 • 10 ⁵ / 3.14 • (10 ^-2 ) ² = 2.6 • 10 ⁹ = 2.6 GPa = 26000 at.

 Such pressures arise during the processing of metals by explosion. Consequently, the technological scheme of the installation, even with these parameters, allows for the first stage to fill the stamp with metal with a high flow velocity of 5 to 10 m / s, which will contribute to good form filling without disturbing the laminar flow. At the next stage, the operation scheme of the installation provides liquid stamping of metal with a pressure reaching 150 MPa, and ensures the production of a metal with a fine-grained, close-packed structure, and also at this stage of casting, the metal structure partially transforms to the processed one. At the final stage of the process, the metal is treated with high impact pressure, of the order of 2.5 GPa, which is capable of deforming a fully crystallized metal. Thus, it becomes possible to obtain forged metal with higher mechanical properties than that obtained with various types of casting, in one transition.

 The proposed workflow for Pulse Die Forging plants allows the use of various technological processes that exist as independent technologies: casting, gas injection molding, injection molding, injection molding and crystallization. Thus, to obtain products with a high-quality structure, the number of transitions is sharply reduced, additional heatings disappear, equipment and the equipment required by classical technological processes are reduced. Consequently, the cost of production and time for its production is reduced.

The choice of metal processing scheme using the method of "Pulse volume stamping" (IOS) takes into account the following:
- getting the melt in the fused billet, it is possible to avoid overheating and reduce the time it takes to move to the stamp;
- at the time of the transition of the melt from a liquid to a solid state, it is processed by electromagnetic, vibrational, pulsed, etc. influences that greatly affect the preparation of a defect-free fine crystalline structure of the product;
- the transition time from the liquid phase to the solid is reduced and therefore the energy consumption when exposed to the metal, by almost all methods of external influences, will be insignificant.

 The basic design of the IOSH installation for implementing the method allows you to quickly fill the die with the melt by adding the speed of its free fall and counter acceleration of the stamp, thereby there is no need to use narrowing in the construction of the gate system, which negatively affects the final structure of the product. In addition, the vacuumization of the IOSH installation allows the melt to be refined and reduces the resistance when filling a stamp with metal.

 The IOS method provides a reduction in the crystallization interval while simultaneously applying low-frequency and ultrasonic vibrations to the metal at the same time, which makes it possible to control the formation of the micro-macro structure of the product and increase its physical and mechanical properties.

 The ability to act on a metal during shaping by an electromagnetic field and gas pressure using an IOS setup leads to a decrease in the crystallization interval and a large supercooling of the melt, and therefore, the quality of the resulting products increases. In addition, using an electromagnetic field, it becomes possible to concentrate the flow of metal falling into the stamp and increase the ability to more complex form filling.

In contrast to the casting method with crystallization under pressure, where in the manufacture of products the metal is prepared in a separate container, overheating it for transportation, and then acting on it in a die with static pressure, the proposed method allows to achieve the following advantages:
- avoid overheating of the molten bath;
- Achieves very fast movement of the melt into the stamp.

Unlike the closest analogue (application SU 96121304, class B 22 D 18/2, publ. 20.01.1999), [2], the claimed method allows to process metal more efficiently, since the method more accurately determines the moment of penetration, thereby pressure superimposed on the melt in a shorter period of time. At the same time, to achieve the same metal processing effect, less pressure is required than in the closest analogue. Common advantages over analogues are the following:
- at the time of crystallization of the melt, it is possible to influence it by almost all known methods of external influence, which can improve the final structure of the product;
- reduce energy consumption when exposed to various pressures on the melt by reducing the solidification time of the product;
- receive a particularly fine-grained and close-packed structure of the product with simultaneous complex form filling.

 In FIG. 2 shows one of the schemes for processing a molten metal in a closed die, where it is possible to achieve particularly high pressures exceeding the pressures of high-speed forging machines.

 All this allows us to consider the proposed method as economically viable and useful for use in production, especially for the manufacture of high-quality products from refractory and chemically active metals.

LITERATURE
1. Efimov V.A. et al. - Special casting methods. Handbook, M.: "Engineering". 1991 year

 2. Application SU 96121304, cl. B 22 D 18/2, publ. 01/20/1999

Claims (1)

 A method of stamping molten metal, which includes obtaining a melt in a melted workpiece, moving it into a stamp, moving the stamp towards the moving melt until it comes into contact with the workpiece, subsequent exposure to increased pressure, characterized in that the movement of the stamp begins at the moment of penetration of the workpiece, which is fixed by the sensor, after which the melt is affected by gas pressure, pressing and forging pressure through the punch, while during crystallization, mechanical and electro agitation vibrations.

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