UA55822A - method and device for production an ingot - Google Patents

Abstract

A method for production an ingot includes pouring into mould of metal with surplus which is defined by mathematical formula, freezing of the top part of an ingot at feeding through gating system and crystallization of the ingot. The device for production of an ingot has a pan with located on it one or several moulds and gating system. In addition, the device is equipped with a capacity connected with mould for the melt located above upper point of formation of an ingot.

Description

Description of the invention

The invention relates to the metallurgy of ferrous and non-ferrous metals and can be used when casting 2 ingots from above or by siphoning.

There is a well-known method of ingot casting |1), which includes pouring metal into an insulated mold that is heated from below, freezing the upper part of the ingot with simultaneous continuous feeding through the pouring system and crystallization of the ingot with plugging of the shrink shell after 0.1 - 0.3 of the duration of complete solidification ingot 70 However, the method requires additional heating losses or pallet warming during the preparation of ingots for pouring.

There is also a known method of obtaining an ingot |2), taken as a prototype, which includes pouring metal into a mold through a pouring system, and the metal is poured with an excess of ldt, which is determined by the mathematical expression: dt:(1.05...1.07)Ктзп , where K is the coefficient taking into account the fraction of shrinkage from the mass of the ingot, cm/min"2; tz is the mass of the ingot; n is the number of ingots on the pallet.

The central one is used with a channel diameter equal to:

Rzh 7 Density of liquid steel;

A - ingot height, cm; and the metal in the pouring system is heated from the moment of the end of filling the pouring molds until the moment of complete crystallization of the metal.

This method requires additional costs for the manufacture of a heated pouring system, additional energy consumption for heating the pouring system during the crystallization of metal in the ingot, reduces production productivity and metal quality due to the intensive development of liquation and segregation processes during long-term solidification of the ingot.

At the heart of the invention is the task of creating a method of obtaining ingots and equipment for its implementation by means of actions regarding the use of new modes of obtaining ingots and the use of additional structural elements with their certain mutual location and to ensure quality improvement, reduction of cost and energy consumption, as well as increase in process productivity. co

The set task is solved as follows: 1. In the method of obtaining an ingot, which includes pouring metal into the foundry with an excess, freezing the upper part of the ingot during feeding through the pouring system and crystallization of the ingot according to the invention, the excess of the melt lt is determined by the mathematical expression: lt:(0 .0005...0.04)t zp, where tz is the mass of the ingot; « du p - the number of ingots on a tray for siphon bottling; p-1, for pouring from above. -o 2. A device for the implementation of the method, which has a tray with one or more spouts installed on it (with a hollow bottom or with a refrigerator in the upper part) and a spout system, according to the invention, with a melt container connected to the spout and located above the top points of ingot formation. In addition:

C. In the method according to p. 1 according to the invention, feeding through the pouring system is carried out during sl 395 0.0002 - 0.099 of the time of complete solidification of the ingot in the pouring vessel. 4. In the method according to p. 1 according to the invention, after 0.1 - 0.95 of the duration of complete solidification of the melt in 1 mold, the ingot is rapidly cooled. co 5. In the method according to p. 1, 4 according to the invention, after 0.3 - 0.95 of the duration of complete solidification of the melt in the pouring vessel, the ingot is turned around the horizontal axis to an angle of at least 70". ko 50 6. In the method according to p. 4 according to the invention, accelerated cooling is carried out by removing the ingot from the mold, and no later than after 0.95 of the duration of complete solidification of the melt, the ingot is plastically deformed. 7. In the device according to p. 2 according to the invention, during siphon pouring, the container for the melt is located above the central one. 8. In the device according to p. 2 according to the invention, the container for the melt is located above the pouring spout. 59 9. In the device according to p. 2, 8 according to the invention, the size of the hole in the sprue is related to the size of of the minimum cross-section in the downspout system by the ratio: yes x deKaUKE 77

To - the diameter of the opening at the top of the pouring or in the refrigerator cover, cm; 60 Where is the diameter of the hole in the minimum cross-section of the downspout system, cm;

Ko and Ko are coefficients of solidification of the melt in the materials of the casting and pouring system in the equation of solidification of the metal according to the law of the square root, cm/min 12, 10. In the device according to item 2 according to the invention, the capacity has a volume not less than the required volume of the melt for compensation of the shrinkage cavity during the time T and the crystallized melt, and T is determined from the ratio:

Ese - the radius of the opening, inscribed in the minimum cross-section of the shower system, cm;

Ko - coefficient of solidification of the melt in the shower system according to the square root law, cm/min 12,

The method is carried out as follows.

The melt is poured with an excess through the sprue system into one or more pourers installed on the pallet, the upper part of the ingot is frozen while simultaneously feeding the melt into the body of the ingot through the sprue system from the capacity for the melt, installed above the upper point of the formed ingot.

The excess melt is necessary to compensate for the shrinkage of the melt before it freezes in the minimum cross-section of the pouring system or in the opening in the refrigerator cover (or at the bottom of an inverted blind-bottomed mold), 7o and also to create metallostatic pressure in the ingot, which contributes to the formation of a gas-tight strong layer of metal in in the form of a crust on its surface. This crust on the surface of the ingot, formed under the metallostatic pressure of the melt in the container, which is always above the upper point of the melt in the ingot, prevents the ingress of oxygen from the air into the ingot during its crystallization, since it is gas-tight. Therefore, in the shrinkage cavity formed after the termination of ingot feeding, the walls are not oxidized and are well welded during further 7/5 plastic deformation, namely during rolling, forging, etc.

The strength of the crust determines the minimum necessary thickness of it, sufficient for plastic deformation. In turn, the thickness of the crust (thickness of the metal crystallized on the upper end of the ingot) depends on the time of feeding the ingot with melt after filling the mold.

Formula lt-(0.0005...0.04)t zp, where: dt - excess melt mass; tz - mass of ingot; n - the number of ingots on a tray for siphon bottling; n-1, for pouring from above, derived empirically and confirmed experimentally. dt should be understood as an additional mass of melt on top of the required for the initial 10090th filling of the mold. This mass is necessary to compensate for the shrinkage of the ingot during its crystallization. According to the proposed invention, this melt mass compensates for less than 10095 shrinkage of the ingot during its solidification. It compensates for shrinkage until the shrinkage cavity is blocked, i.e. until the melt supply to the mold is stopped due to the freezing of the sprue system that feeds the ingot. with

The minimum coefficient value of 0.0005 allows obtaining a gas-tight and sufficiently strong crust. At a smaller value of this coefficient, the melt supplied after filling the mold is not enough to obtain a crust that would have the necessary strength and gas density. Such a crust must oxidize during heating under plastic deformation or collapse during plastic deformation, which will lead to delamination and a significant increase in the main cut.

The excess of molten metal depends on its amount in the capacity for the melt and the freezing time of the shower system in any of its intersections.

The use of a coefficient of more than 0.04 is impractical, since for this it is necessary to make a siphon wire of too large a diameter and/or insulate and/or heat the capacity for the melt and the shower system " (siphon wire), which leads to a decrease in the productivity of the process, as well as to an increase cost and energy consumption when implementing the method. When feeding the ingot during its crystallization during 0.0002 - 0.099 of the time of complete solidification of the ingot m in the mold, a crust is built up, sufficient to obtain a hermetic cavity in the ingot, which is completely sealed during plastic deformation.

If the ingot is fed for a shorter time, the crust will be weak and collapse during plastic deformation, as a result of which the walls of the cavity are oxidized and not welded. o For 0.099 time of complete solidification of the ingot, about 5095 mass of the ingot has time to crystallize in the mold. sl The shrink cavity formed at the same time is welded with small compressions, and in addition, it is possible to obtain a roll of the required thickness. Further expansion of the walls of the shrinking cavity is impractical, because it does not give significant advantages, but leads to a decrease in the productivity of the process. 7 50 During the solidification of the ingot in the mold, the rate of growth of the metal layer constantly decreases according to the square root law. At the same time, healing and segregation processes develop, resulting in healing

Iz (melt with a high content of carbon, sulfur, phosphorus, etc.) with a lower crystallization temperature solidifies later and, together with segregates (oxides of aluminum, silicon, titanium, etc.), concentrate in the middle of the ingot, contributing to the appearance of delamination in the product. These processes develop over time, so any reduction in the time of crystallization of the ingot leads to a decrease in liquation and segregation, that is, to an improvement in the quality of the ingot.

Accelerated cooling for liquation processes can be carried out, for example, by removing the ingot from the mold, supplying a coolant (water, gases) to the ingot, etc.

After the solidification of the main mass of the ingot sealed according to the proposed method, inside it (as in an ordinary ingot, a melt enriched with liquats and segregates accumulates, which are concentrated at the bottom of the shrinkage cavity at the level of 10 - 3095 of the height of the ingot, their quantity is much less than in ingots with a heating point, because the crystallization time of the ingot is shorter, but in some cases they can form in quantities that can be detected experimentally.

Turning the ingot to an angle greater than 707 (for those expanding upward) and to an angle greater than 907 (for those expanding downward) contributes to the flow of melt volumes enriched with liquid and segregates to the head of the ingot, where they are dispersed in the melt and, accelerated when hardening, they do not form delaminations during plastic deformation.

Turning the ingot after removing the mold can be done at 1807. This allows you to concentrate the volumes of melt enriched with liquid and segregates near the upper end of the ingot and remove them after plastic deformation

With the main cut, increasing the quality of the metal in the ingot. Moreover, in order to remove these impurities, it is necessary to cut off a smaller portion of the ingot than when turning the ingot sideways. This technique is appropriate for a small volume of the melt enriched with liquats and segregates, that is, when most of the melt has crystallized.

The lower limit of the time to turn the ingot - 0.3 of the duration of complete solidification of the melt in the mold - is due to the following. 70 If the time before turning the ingot is shorter, a significant amount of melt will remain inside it, which, flowing into the head of the ingot, fills a larger volume, in which the melt and segregates will float to the surface of the melt, interfering with the welding of the walls of the shrinkage cavity during plastic deformation, which significantly increases main crop, reducing process indicators.

If the time before turning the ingot is greater than the upper limit of 0.95 of the duration of complete solidification of the melt in /5 Foundry, most of the liquid and segregates will have time to go into a solid-liquid state, losing their fluidity before turning the ingot, and the specified operation will not lead to an improvement in the quality of the metal.

Plastic deformation of the ingot until solidification of the melt inside it has the same goals as turning the ingot. If the plastic deformation of the ingot is started before the core solidifies, accelerated freezing of the remaining melt takes place. Increasing the contact area of the ingot with the environment and with metal tools for plastic deformation (rolls, hammers, etc.) accelerates the solidification of the core and leads to a more uniform distribution of impurities in the product, i.e. increases its quality. At the same time, this technique allows you to significantly reduce the costs of heating the ingot for plastic deformation and to strengthen individual crimps due to the higher temperature of the metal.

The method can be used both for pouring from above and for siphon pouring.

To implement the method, the equipment shown in figures 1, 2, 3, 4 is proposed.

Fig. 1 - pouring of steel with a siphon with feeding through a shower system from a container located above the central one.

Fig. 2 - pouring of steel with a siphon with feeding through a sprue system from a container located above the sprue. c zo Fig. 3 - pouring of steel from above with feeding through the sprue system from the container located above the sprue. with

Fig. 4 - pouring of steel with a siphon with feeding through a spigot system due to a heating tap installed on the pallet of a conventional pouring tap with a tap.

The device has a container for melt 1, connected through a sprue system 2 by sprues 4 (without a heating nozzle) installed on a pallet 3. The top of the sprue 5 is the dead bottom of an inverted deep-bottom sprue or a refrigerator cover installed on the upper end of a through sprue. which expands downwards. The bottom of a deep-bottom mold or a refrigerator lid can be flat or concave in the lower part and have a protrusion (a through hole for gases to escape).

The container for the melt can be a separate container (lined or ceramic, preferably insulated), "installed on the center 6 or made as one unit with the center (Fig. 1), or placed above the sprue pl") c (Fig. 2; C) and is connected to the sprue by a spigot system. The role of the shower system feeding the ingot at the beginning. crystallization, can be performed by a siphon wire when the capacity is located above the central one or a glass - when the location of the capacity above the spout.

The container for the melt, the feeding ingot obtained by the proposed method, during siphon pouring, can also serve as a part of the heating tap of the foundry (for obtaining the ingot with a tap), installed on the same pallet and connected to it by a siphon wire (Fig. 4) . At the same time, part of the heating point, the feeding ingot obtained by the proposed method, is located above the upper point of the ingot.

Go! The size of the hole in the sprue is combined with the size of the minimum cross-section in the sprue system by the ratio: о 2ие2 о where:

To 2 De Ka i7kE

Co.)

To - the diameter of the opening at the top of the pouring or in the refrigerator cover, cm;

Where is the diameter of the hole in the minimum cross-section of the downspout system, cm;

Ko and Ko - coefficients of solidification of the melt in the materials of the casting and pouring system in the equation of metal solidification according to the law of the square root, cm/min 12,

Р» This condition reflects the need for the metal in the ingot to freeze later than in the upper part of the ingot (below the ingot) and to hermetically close the cavity formed in the ingot when the ingot is fed from the capacity located above the ingot. If this condition is not met, then when the melt capacity is separated from the ingot, a hole may form in the shrinkage cavity, which will oxidize during heating for further processing and, during plastic deformation, will cause delamination in the finished product.

The capacity for the melt accommodates the volume of the melt no less than it is required to compensate for the shrinkage cavity during the time t and the crystallized melt, and t is determined from the ratio: tunic? kvi, where: because Ks is the radius of the opening, inscribed in the minimum cross-section of the downspout system, cm;

Ks - coefficient of solidification of the melt in the shower system according to the square root law, cm/min72,

The theoretical basis and conclusions regarding this condition are the same as those described above for determining the diameter of the sprue system when feeding from a capacity located above the sprue, only the revealed dependence relates the time of ingot feeding to the radius of the sprue system, where the melt, the feed ingot, freezes earlier above all.

Tests of the method and equipment were carried out in the conditions of an active metallurgical production.

56 steel ingots of the St. SSP with a mass of b tons in the downward-expanded deep-bottom hoppers with a vent in the upper part (lid); 9 ingots (MoMo1 - 9) were cast from above and 36 ingots (MoMo10 - 45) were siphon cast on four local pallets. When pouring from above, a lined container with a pouring cup diameter of 50 mm, coaxial with the opening in the lid, was placed on the end of the 70 Pouring machine (lid). After filling, the mold was poured into a capacity of 100 kg. excess melt, of which 7Okg went to compensate for the shrinkage before freezing of the melt in the hole in the lid, and bOkg - froze during this time in the capacity and in the glass.

MoMo1 - C ingots after 0.1, MoMo4 - 5 after 0.4, and MoMo7 - 9 after 0.8 of the time of complete solidification of the melt at 75 Pours were taken out of the pourers and cooled with water from the quenching device, after which they were rolled with a cold charge on blooms with a cross section of 200x22Omm , and then to grade rolling - corner Mo16, which was subjected to 10095 UZK control. Rolls from MoMo4 - 9U ingots had small defects in the lower part, which were recorded during a brutal ultrasound inspection, rolls from the last ingots had defects only in MoZ ingots, and rolls from MoMo1 and 2 ingots had defects

UZK did not have. The main cut of the rolls of all nine ingots was 295, and the bottom - 3905.

MoMo10 - 45 ingots were cast by the siphon method on four-place pallets and fed from the lined capacity placed above the center, which holds 400Okg of melt, of which 280kg went to compensate for volumetric shrinkage during the solidification of the melt in siphon wires with a diameter of 5Ω, and 120kg was frozen in the capacity.

MoMo10 - 21 ingots, after 0.1 time of complete solidification of the melt, were removed from the molds, cooled in air, and after 0.5 time of complete solidification of the melt, they were turned around the horizontal axis by 94" (put on their side). After complete cooling, these ingots were heated in wells for current technology and rolled on "blooms with a cross-section of 200x200mm, and then on the Mo20 corner.

MoMo22 - 33 ingots were removed from the molds after 0.1 time of complete solidification of the melt, and after 0.7 time of complete solidification of the melt, they were placed in heating wells, and after 0.9 time of complete solidification of the Ge melt, they were rolled onto blooms with a section of 200x220 mm, and then onto a corner Mo20.

MoMo34 - 45 ingots were taken out of the molds after 0.5 time of complete solidification of the melt in the mold and immediately rolled (bypassing the wells) on blooms with a section of 200x22Omm, and then on the corner of Mo20. eh

All rolling from MoMo10 - 45 ingots is controlled by 10095 UZK. No defects were recorded in any of the rolls. The main edge of the rolls of all ingots was 295, and the bottom edge was 395. yuyu

As an example of the implementation of the method adopted as a prototype, 4 ingots were cast with heating of the melt in the central and siphon wires. Calculations according to the dependence given in the formula of the invention showed that the central one should have a powerful induction furnace with a diameter of bOOmm and a height of 2 meters. The melt in the casting hardens along all walls, and in order for the level of the melt in the center to be at a level slightly above the upper point of the melt inside the ingot (according to the prototype), it is necessary for the center to have a much larger cross-section of the casting wire in the upper part than in the lower part. The diameter of the siphon wire was bOO0mm in the upper part and gradually decreased to 100mm in the lower part. In the process of filling the mold with melt and in the initial period after its filling, accelerated solidification of the melt occurs on the surface of the mold, which is not heated. As the layer of crystallized melt grows, the liquidation and segregation processes intensify, their products move to the upper horizons of the mold and accumulate there. Therefore, the slowing down of the Crystallization process leads to the formation of a zone of positive liquation, and the concentration of segregates along the axis of the ingot - the axis of the off-axis zone of negative liquation, which worsens the quality of the ingot.

Rolls made from ingots cast according to the prototype had defects recorded during the ultrasound inspection. In addition, the time to obtain the ingot according to the claimed method with crystallization in the mold without accelerated cooling and (ee) plastic deformation is 2 times shorter, and the mass of the ingot is smaller by only 1 - 3.595. When using accelerated cooling, and even more so when rolling with a liquid core, the time of obtaining the ingot according to the stated method with subsequent plastic deformation is reduced by 2-10 times. Thus performance

Kz of the proposed method is 2 - 20 times greater than that of the prototype.

In the ingots cast according to the stated method, there is no zone of negative liquation, and positive liquation is manifested in the form of a small liquation spot in the lower third of the ingot, which is fixed under strict control. If

This stain must be removed, the method involves removing the ingot from the mold, accelerated cooling and turning the ingot to an angle of more than 70" (laying on its side or head) or plastic deformation after 0.1 - 0.95 time » of complete solidification of the metal.

Thus, the above set of features solves the task.

The proposed method and the equipment for its implementation make it possible to shorten the time of crystallization and to reduce energy costs in the process of receiving the ingot, excluding the heating of the pouring system, as well as to reduce the additional costs of heating the ingot before plastic deformation, not worsening its quality, but improving it, which ensures a decrease in cost casting and increasing the productivity of the process.

Used literature: 1. Patent of Ukraine Mo26120, 8220 04/27, 06/07/99. Bul. Mo3Z. 65 2. Author's certificate of the USSR Mo1685593, B220 7/00, 27/04, 23.10.91. Bul. Mo39.

Claims (10)

The formula of the invention 1. The method of obtaining an ingot, which includes pouring metal into the mold with an excess, freezing the upper 2 parts of the ingot during feeding through the pouring system and crystallization of the ingot, which is distinguished by the fact that the excess of molten metal dtt is determined by the mathematical expression: l E (0.0005. ..0.04) tzp, where: / tz is the mass of the ingot; n - the number of ingots on a tray for siphon bottling; p-1 for pouring from above. 2. A device for implementing the method according to claim 1, which has a tray with one or more pouring spouts installed on it and a sprue system, which is characterized by the fact that it is additionally equipped with a melt container connected 75 to the sprue, located above the upper point of the ingot formation. Q. The method according to claim 1, which differs in that feeding through the pouring system is carried out within 0.0002-0.099 of the time of complete solidification of the ingot in the pouring vessel. 4. The method according to claim 1, which is distinguished by the fact that after 0.1-0.95 of the duration of complete solidification of the melt in the caster, the ingot is rapidly cooled. 5. The method according to claims 1.4, which is distinguished by the fact that after 0.3-0.95 of the duration of complete solidification of the melt in the mold, the ingot is turned around the horizontal axis by an angle of at least 70°. 6. The method according to claim 4, which differs in that the accelerated cooling is carried out by removing the ingot from the mold, and no later than after 0.95 of the duration of complete solidification of the melt, the ingot is plastically deformed. 7. The device according to claim 2, which differs in that during siphon pouring, the container for the melt is located above the central one. " 8. The device according to claim 2, which is characterized by the fact that the container for the melt is located above the pouring spout. 9. The device according to claims 2, 8, which differs in that the size of the hole in the sprue is related to the size of the minimum section in the sprue system by the ratio: с и и 2 2 зо До Дод, ДК КИ сч where: Where is the diameter of the opening at the top pouring or in the refrigerator lid, cm; co HELL. - diameter of the hole in the minimum cross-section of the downspout system, cm; у Кр and Ко - coefficients of solidification of the melt in the materials of the casting and pouring system in the equation Зо of metal solidification according to the law of the square root, cm/min 12, which 10. The device according to claim 2, which differs in that the container has a volume not less than that required by the melt to compensate for the shrinkage cavity during time 7 and the crystallized melt, and 7? is determined by the ratio: "tT-5-ri 20 tA KK min| w-v s where: h» K, - the radius of the hole inscribed in the minimum cross-section of the downspout system, cm; " Kk; - solidification coefficient of the melt in the shower system according to the square root law, cm/min 12, 1 1 (ee) ime) Ko) 60 b5