SU1592100A1

SU1592100A1 - Method of horizontal semi-continuous casting of metais

Info

Publication number: SU1592100A1
Application number: SU833675153A
Authority: SU
Inventors: Evgenij A Korshunov; Yurij A Samojlovich; Tatyana V Meshchaninova; Anatolij G Tarasov; Valerij L Bastrikov; Avgusta P Zakharyan
Original assignee: Uralsky Politekhn Inst; Vnii Metall Teplotekhniki
Priority date: 1983-12-28
Filing date: 1983-12-28
Publication date: 1990-09-15

Description

The invention relates to metallurgy. The known method is semi-continuous.

hyi, in particular to semi-continuous casting, according to which

casting blanks. billet cast by pe3

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movable mold with a closed end, and the liquid metal in the mold is fed through the formed workpiece, 5

The disadvantages of the method include the low casting speed and the quality of the metal in the axial zone. In addition, the method has a limit on the number of grades of cast metals and alloys (this method cannot, for example, cast aluminum alloy blanks having a wide crystallization interval)

The closest to the proposed 15 to the technical essence and the achieved result is a method of semi-continuous casting of metals, including the filling of two metal acceptors and a horizontal mold 20 between them with a liquid metal, a time delay during which the initial crust of the billet is formed in the crystallizer and the grip it with a hollow 25 seed, moving the workpiece when the liquid metal is fed into the crystallizer from the side of its ends from two metal receivers, completion. the formation of a fixed billet with the periodic movement of the liquid metal through the formed billet from one metal reservoir to another.

However, according to this method, it is difficult to ensure the stability of the process, since the two-sided extrusion of the workpiece is preceded by a gap of a sufficiently thick crust of the workpiece reliably coupled to the seed.

This gap is preferable to have dd in the middle part of the mold, however, it can occur in the part of the mold where it is undesirable, and this can lead to a violation of the process.

In addition, there is an inconvenience in the supply of liquid metal to two metal receivers when they are continuously moving. ' -50

When it is stretched to the prescribed length, the workpiece cannot be moved periodically and, therefore, in the initial period of the formation of the crust of the workpiece it is impossible to create increased pressure on it and to improve the quality of the cast workpiece,

The aim of the invention is to improve the quality of the molded blanks and increase their range.

This goal is achieved by the fact that in the method of horizontal semicontinuous casting of metals, including the filling of two metal receivers and a horizontal metal mold between them, a time delay during which the initial crust of the billet is formed in the crystallizer and its grip is attached to the hollow seed, moving the workpiece when feeding into the mold of liquid metal from its ends from two metal receivers, the completion of the formation of a fixed billet with a period By moving liquid metal through a preform being formed from one metal reservoir to another, one of the metal receivers is sealed before filling and filled with metal from the second metal reservoir through the preform formed in the crystallizer with the creation of an overpressure of gas above the meniscus of the liquid metal within 0.1-0.5 MPa The hermetically sealed metal receiver connected by means of a hollow seed to the molded workpiece is periodically moved at a speed O,, 5 m / s per step equal to 30-95% of the length of the mold, and m ^ Independent user oche before moving hearth sealed gas pressure therein is reduced to atmospheric pressure, and during the pauses between the displacements carried out in a sealed metal reservoir fluctuations of molten metal level.

Fluid level of liquid metal "in a sealed metal reservoir is carried out every 2-4 seconds, while changing the gas pressure in the metal receiver by the value of P = where y is the specific weight of the metal to be cast, N / m ³ ; H is the difference between the upper and lower levels of liquid metal, m ...

Creating an overpressure in the range of up to 0.5 MPa above the meniscus of the liquid metal in a sealed metal reservoir in the pauses between its movements allows the initial formation of the crust of the workpiece in the crystallizer under pressure sufficient to eliminate

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the shrinkage gap between the grinding cake and the mold wall, which contributes to the improvement of the quality of the cast billet.

The adhesion of the first portion of the solidified crust of the preform with a hollow sieve placed on only one metal receptacle allows one-way periodic pulling of the preform out of the crystallizer by a step close to the length of the crystallizer and corresponding to the length of the detachable part of the preform a mold that can. to take place in the case of bilateral extrusion of the workpiece from the mold.

The speed of movement of the sealed metal reservoir is recommended to take in the range of 0.1-0.5 m / s, because the speed of 0.1 m / s and more ensures that the end of the next stretchable section of the skin of the billet has an uncured liquid metal, which is necessary for high-quality casting. blanks. The speed of movement of the sealed metal receiver to 0.5 m / s is quite sufficient to quickly extend the next section of the billet from the mold at any possible length of the mold, and even at the maximum recommended speed of movement of the sealed metal receiver, the mold is filled with liquid metal and dangerous dynamic loads do not occur. in the nodes of the machine.

Some change in gas pressure above the meniscus of a liquid metal. in the sealed metal reservoir in the pauses between its movements, during this period it is possible to have a constant movement of the liquid metal in the workpiece relative to the entire solidification front, which contributes to the refinement of the structure of the molded workpiece and, consequently, to improve its quality and allows you to expand the range of workpieces cast on horizontal machines in Particularly cast on such machines billet of individual aluminum alloys of relatively large cross section, for example with a diameter of 200-300 mm.

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The recommendation to change the gas pressure above the meniscus of the liquid metal in a sealed metal reservoir after 2-4 s allows you to change the direction of movement of the liquid metal in the cast billet per unit of time, a number of times that is enough to get the same effect that is obtained in the case of reversible movement of the liquid metal reversible electromagnetic field.

FIG. 1 shows a schematic of a semi-continuous die casting machine and the process of forming the first crust of the blank; in fig. 2 - the moment of extrusion of the formed billet from the crystallizer on the set extrusion step.

The machine for carrying out the method (FIG. 1) has a fixed metal receiver 1 with holes 2 for tapping the metal in which the metal conduit 3 is placed. A crystallizer 4 is connected to the metal conductor 3 '. A sealed metal receiver 5 is attached to the crystallizer 4 in the initial position, equipped with a hollow seed 6, which is introduced into the cavity of the mold 4 and overlaps the end of the mold. In the seed placed metal pipe 7, communicating with a sealed metal reservoir 5 through the horizontal 8 and 9 vertical channels made in the refractory block 10. The refractory block 10 is placed on the drive carriage 11. The sealed metal reservoir 5 is blocked on top of the cover 12 with a hole in which the flange 13 is placed, connecting the sealed metal- 'receiver 5 with a gas system (not shown).

The method is as follows.

In the initial position (Fig. 1), the seed 6 is pressed against the crystallizer 4 and the metal receiver 5 is sealed, leaving the opening in the flange 13 uncovered. Then the liquid metal 14 is fed into the metal receiver 1, which through the hole 2 and the metal pipeline 3 enters the crystallizer 4 and then through the metal pipeline 7 in the seed 6 and the channels 8 and 9 in the refractory block 10 to the sealed metal reservoir 5, while the gas from the metal receiver 5 is removed through from 7

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A version in the flange 13, 'Having filled the mold 4 with the liquid metal and the metal receiver 5 to a predetermined level, the opening in the flange 13 is blocked and the liquid a given gas pressure is created above the meniscus of the liquid metal in the metal receiver 1. When creating gas pressure over the meniscus of the liquid metal in the metal reservoir 1, there will be a slight increase in the level of the metal in the sealed metal reservoir 5 and the compression of gas in it.

The magnitude of the gas pressure in the metal reservoirs depends on the metal being poured 15. During the casting of light alloys (aluminum, magnesium), the gas pressure can be increased to 0.2–0.3 MPa, and during the casting of steel - to 0.4–0.5 MPa. 20

To create a gas pressure in the metal, the tall acceptor 5 does not have to create an overpressure of the gas under the meniisk of the liquid metal in the metal receiver 1. When casting, for example, 25 light alloys, an induction pump can be placed between the metal receiver 1 and the mold 4 and create the required gas pressure in metal-39 receiver 5.

Creating the necessary gas pressure in the metal receivers 1 and 5, the initial formation of the crust 15 in the mold 4 is carried out. moreover, the formed crust of the workpiece is under pressure at the same time from the side of the liquid metal, which contributes to pressing it against the walls of the mold and eliminating the early formation of a gap between the surface of the crust of the workpiece and the wall of the mold,

In the conditions of horizontal casting, the exclusion of early formation of the gap allows casting blanks with dd 'uniform thickness of the crust along its perimeter.

After filling the metal reservoir 5 with liquid metal and creating a set gas pressure over its meniscus, every 2–4 s, the liquid metal is repeatedly lowered and raised by a set distance Τι (Fig. 1) and thereby creates a reciprocating movement of the liquid metal relative to the crystallization front of the cast billet, which contributes to obtaining a billet with high-quality fine-grained structure.

The lowering and temperature distribution of the liquid metal by the amount b in the metal receiver 5 can be done by changing the gas pressure in the metal receiver 1, but it is more simple to lower it, increasing the gas pressure in the metal receiver 5 by introducing compressed gas through the hole in the flange 13, and raising the meniscus to its previous level Bleeding part of the gas from the metal receiver 5.

When the crust 15 of the billet section in the mold 4 reaches a predetermined thickness and adheres to the seed 6, the periodic change in gas pressure in the metal receiver 5 is stopped and the gas pressure in the metal receivers 1 and 5 is reduced to atmospheric pressure. After that, the sealed metal reservoir 5 at a speed of 0.1-0.5 m / s is moved to a fixed pitch, which can be equal to 30-95% of the length of the mold. FIG. 2 shows the moment of movement of the sealed metal receiver 5 to the installed step 1.

When moving hearth 5 mounted on the step 1 in the _same) by seeding step 6 of the mold 4 is pulled in the solidified portion of workpiece 16 and mold 4 by the two opposite ends of metallopri (emnikov 1 and 5, the liquid metal is supplied.

During the extrusion of the workpiece 16 from the mold 4 on the side of the metal pipe 3, the crust 17 of the next part of the workpiece begins to form, and between the newly formed crust 17 and the previously formed and pulled crust 15 from the mold. At a distance, the metal is in a liquid state. The value depends on the overheating of the liquid metal entering the crystallizer and on the speed of pulling the preform out of the crystallizer. After 1-2 seconds after stopping the preform from the crystallizer, the liquid phase of the metal between the newly formed crust 17 and the previously formed crust 15 disappears and at the junction of these crusts they are joined, and the strength of the said compound may be different. If later on the junction of the crusts will be carried out section 9

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It is desirable to have the smallest possible dimension of the workpiece to the measured parts, the strength in the section of the workpiece passing through the joint. If, however, the separation of the separated workpiece is not carried out at the place of the joint, then it is necessary to take measures to ensure that the adjacent crusts of the workpiece are reliably welded in the joint zone. This is achieved by eliminating the oxidation of the end parts of the crusts and their overcooling and by the fact that after the next pulling of the workpiece from the crystallizer, it is given a slight reverse displacement.

In machines for the implementation of the proposed method, it is recommended to use molds with a length of 0.751.5 m. With such crystal lengths

depending on the length of the mold, blanks can be obtained, separated by sections, the length of which will be 25 within 0.225-1.425. Industrial round billets, for example, from aluminum alloys, which, as a rule, are sent for pressing, have a length of 0.25-1.4 m. 30

Next comes a pause, during which, in accordance with the proposed method, a new crust of the workpiece is formed in the mold and the formation continues earlier 35

formed peel.

The process of casting the workpiece during its periodic movement is repeated until the sealed metal reservoir 5 is displaced by a predetermined distance corresponding to a given length of the workpiece. After moving the metal reservoir 5 at a set distance, complete the formation of the billet with a constant reciprocating movement of the liquid metal relative to the entire solidification front of the billet 16 and maintaining the established overpressure in the metal receivers.

Before complete curing of the workpiece, the reciprocating movement of the liquid metal in the workpiece is stopped and the liquid metal from the metal receiver 5 is completely removed.

Having completed the formation of the workpiece 16, the hole 2 in the metal receiver 1 overlap (the device for the ceiling

This hole is not shown), and the workpiece and the metal receiver 5 move a distance greater than the length of the mold. Then the workpiece 16 is disconnected from the seed 6, removed from the line of casting, the metal reservoir 5 is moved to its original position and start pouring the next billet.

In the case of use between the metal receiver 1 and the mold 4 of the induction pump, it is not necessary to block the opening 2 in the metal receiver 1 before removing the workpiece 16 from the casting line, since the pump prevents the leakage of liquid metal from the metal receiver 1.

Example. A round billet with a length of 5 m is cast from an aluminum alloy with a diameter of 250 mm through a mold with a length of 1.05 m.

We take the step of moving the metal receiver 5 (Fig. 1 and 2) 1m, the average speed of movement of the metal receiver 5 0.2 m / s, the pause between successive movements of the metal receiver 5 55 s, the time of initial filling of the mold 4 with metal 5 s, the formation time of the first crust of the workpiece in the mold 55 s.

In the pauses between the periodic movements of the metal receiver 5 and after it moves on. a given distance the gas pressure in it is set to 0.2 MPa, and then change in

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the direction of increase and decrease in accordance with a given value of lowering the meniscus of a liquid metal N.

If the value of H (Fig. 1) is taken to be 0.25 m, then this pressure will need to be increased by 6,750 MPa.

In the accepted mode of casting the workpiece, the time from the beginning of the supply of liquid metal to the mold to the end of the periodic movement of the metal receiver 4 at a set distance will be 4 minutes 5 seconds (~ 4 minutes).

If the average crystallization coefficient for aluminum alloy is K = 3.5 cm.min "® ^, then the time of complete solidification of the workpiece after moving the metal receiver 5 at a set distance, and in this case by 4 m, will be 13 minutes. The total time for forming the workpiece, taking into account time for periodic

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the movement of the metal receiver 5 at .5 m 'will be 17 minutes.

Three minutes will be required to remove the blank from the casting line and to return the metal receiver 5 to its original position. The total cycle of casting the billet. Will be 20 minutes.

Average hourly casting speed will be 15 m / h, Yu

On the known machines of semi-continuous casting of metals of the vertical type, aluminum alloys, for example, grades D16-, AKB, AK4 and a number of others are poured into round billets with a diameter of 200-250 mm at a speed of 5-8 m / h, i.e. approximately two times smaller

These alloys can be cast by the proposed method only if, during the formation of the preform, a constant movement of the liquid metal relative to the solidification front is ensured. For this 25

example, it will be provided if every 3 seconds a cycle is repeated.

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lowering and raising the meniscus liquid

metal in the metal reservoir 5 at a distance of 200-250 mm.

The proposed method compared to the prototype allows casting in stable conditions of high quality with the productivity of one installation stream, one and a half to two times larger when casting, for example, round billets with a diameter of 200-300 mm and a length of 5-6 m.

This method is possible casting a number of alloys, for example, aluminum, which do not spill on installations of the horizontal type. These alloys can not be bottled and the method adopted for the prototype.

The proposed method allows to expand the range of cast billets of various metals and alloys, cast on horizontal-casting machines, which from the economic point of view are the most profitable. Their construction is cheaper and easier to operate.

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Claims

one . A METHOD OF HORIZONTAL SEMI-CONTINUOUS METAL CASTING, including the filling of two metal receivers and a horizontally positioned Γο between them a crystallizer with liquid metal, a time delay,

during which, in the mold, the initial formation of the crust of the preform and its adhesion to the hollow seed, the preform is transferred when the liquid metal is fed into the crystallizer from its ends. two metal reservoirs, the completion of the formation of a fixed billet with periodic displacement of the molten metal through the billet being formed from one metal reservoir to

the other, characterized in that, in order to improve the quality of the cast blanks and increase their range, one of the metal receivers is sealed before filling and filled with metal from the second metal receiver through the billet formed in the mold with overpressure of the gas above the meniscus metal within 0, 5, 5 MPa, sealed metal receiver, connected by means of a hollow seed with the molded workpiece, is periodically moved at a speed of 0.1-0.5 m / s in a step equal to 30-95% of the length of the mold, and Before the next displacement of the sealed metal receiver, the pressure in the gas in it is reduced to atmospheric, and during the pauses between the movements in the sealed metal receiver, the level of the liquid metal fluctuates.

2. The method according to p. 1, characterized by the fact that the fluctuations in the level of the liquid metal in a sealed metal reservoir are carried out every 2-4 seconds, while changing the gas pressure in the metal receiver by the magnitude of P = ub, where 2Г ”The specific weight of the cast metal, N / m ';

B - the difference between the upper and lower levels of the liquid metal, m

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