DE2115208A1 - Process for producing continuous castings from steel and other metals and Vornch device for practicing the process - Google Patents

Description

PATENT LAWYERS

DIPL-ING. CURT WALLACH 911

DIPL-ING. GÜNTHER KOCH ^l ''

DR. TINO HAIBACH

13 134

8 Munich 2 29, March 1971

KaufingerstraSe 8

Telephone 240275 area code OBU

SocieU OiTiIe dite:

SOCIETE CIVILE D ¹¹ ETU-DES DE CENTRIFUGATIOH

7, Rond Point Bugeaud

P a r i β 16 / France

Process for producing continuous castings from steel and other metals and apparatus for practicing the Procedure

The invention relates to a method for the production of continuous castings from steel and other metals with comparable properties and devices for exercising this Process and products manufactured according to the process "

The invention will then be described with reference to steel continuous casting, but it actually relates to the continuous casting of metals and alloys per se, which have similar properties, in particular a melting point corresponding to the melting point of steel, which is, for example, between 3100 and 1800 ⁰ C »

The method according to the invention is of particular importance

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for quality steels and alloyed * steels, for example for chromium-nickel and chromium-nickel-molybdenum alloys » genes

As is known per se, the continuous casting of steel is based on the fact that the steel is in a liquid state in a strongly cooled casting mold, for example in a casting mold cooled by a stream of water, in order to bring about a continuous hardening of a rod, the is pulled vertically downwards with the help of drive rollers in order to bring about a continuous solidification »

Static continuous casting processes are already known, in which the molds do not rotate about a vertical axis and the cast products produced are only subjected to a vertically downward displacement. Following this procedure you can steel blanks of prismatic shape (generally with a square or rectangular cross-section) can be produced in a useful manner «,

The applicant has already proposed a centrifugal casting process for continuous steel casting, in which the mold, in which the solidification process begins, the resulting blank and also the pulling and cutting device for the finished blank can be set in constant rotation about a vertical axis, with the mold as well can be subjected to an oscillating movement running in the vertical direction with a small amplitude. According to this process, blanks or rods with a circular cross-section can be produced good quality allows the immediate production of high-quality rolled steel tubes «

The process according to the invention is used in the last-mentioned centrifugal casting process for continuous casting

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The invention provides a novel centrifugal casting process for continuous casting of steel and similar metals represents, after which the liquid metal in a mold or casting mold that revolves around a vertical axis, given and during the solidification by pulling the blank downwards and by spraying on water is vigorously cooled on the lower part of the blank protruding from the mold in order to bring about the solidification; the method is characterized in that an axial zone during solidification in at least one zone of the blank located below the casting mold Circulation of the liquid metal remaining inside the blank with the help of inside the blank induced electromagnetic fields.

According to a preferred embodiment of the invention, the induced electromagnetic fields caused by groups of inductors adjacent to each other to surround the ingot during solidification of the ingot, and the inductors are supplied as with multi-phase "· stream that pulsating electromagnetic fields are created along _t which the Shifting the axis of the blank "According to the invention, for example, an electromagnetic field can be generated with the aid of three inductors that are excited with three-phase current three-phase inductors are used »

The electromagnetic fields used according to the invention are only used to produce a circulation of liquid metal in the interior of the blank during the solidification process, this circulation in the axial direction of the

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Blanks, doh «should run in the vertical direction« This is achieved with the help of the inductors mentioned above in that the inductors have electromagnetic fields in the entire cross-section of the blank during the solidification process, the field strength is larger on the outer edge of the liquid metal than in its center o

It follows that in the area exposed to the electromagnetic fields generated by the inductors the liquid metal located in the blank during the solidification process in an axial direction running flow is set in motion, This flow runs in a predetermined direction in the central area of the blank, roughly from bottom to top, and the liquid metal arriving in the upper part of the zone exposed to the electromagnetic fields then moves into the edge zones of the liquid metal contained in the blank and there in the opposite direction to its starting point (ZcBo in the direction from top to bottom in the blank) back to its starting point «

One can imagine that, under these circumstances, in the zones which have the above-mentioned electromagnetic freedom who are exposed to a metal circle, in which the liquid metal is made to flow one after the other along the surface of the blank that is already has solidified, and then into the central zone of the blank in the area of the axis, which is about to freeze.

Such circulation provides very significant advantages in the field of metallurgy.

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First of all, this cycle of the solidifying metal offers the advantage that in the metal during the solidification process contained inclusions over a larger area in the center of the blank to be able to distribute, whereby the formation of inclusions in the axis of the blank is largely avoided «

This process is particularly important in centrifugal casting processes for continuous casting, because in this case the forces based on the rotation of the liquid metal and the centrifugal effect combine " In the centrifugal casting process for continuous casting namely, the inclusion particles, like the liquid metal, are subjected to a centrifugal force, which causes the inclusions, which have a lower density than the metal, in the axis of the blank can be accumulated o According to according to the invention, this collection of inclusions in the center due to the currents generated in the liquid metal can be effectively avoided, and the Inclusions are distributed over a much larger area of space, so they cannot cause the disadvantages of massaging them in the axis of the finished product would occur »

The method according to the invention has the further advantage that the solidification process takes place more quickly and a more homogeneous central zone in the blank is achieved »

In the known methods, namely, the solidification of the metal located in the center of the blank takes place almost exclusively by heat conduction, with the amount of heat given off by the liquid metal the ever increasing thickness of the already solidified

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Metals have to pass through the outer surface Spraying with water was vigorously cooled

Since the liquid metal placed in the casting mold must necessarily have a temperature slightly above the solidification temperature if it is to be supplied under favorable conditions, it follows that the metal must first give up the amount of heat during the solidification process that the bound heat between its actual temperature and its solidification temperature corresponds to ₀

Thanks to the circulation of the liquid metal which, according to the invention, is superimposed on the rotary movement the metal located in the section of the blank that is in contact with the already solidified wall is brought up. Hence the liquid metal, which was originally in the middle of the blank and therefore had a temperature that was above its solidification temperature, a remelting of the already solidified * th surface of the blank, where it gives off part of its heat, which leads to a reduction in its temperature. It can be seen that under these circumstances the circulation of the liquid metal inside the blank limits the strength of the already solidified wall (which is an advantage for a good further heat dissipation is), and that the temperature of the metal still to be solidified is reduced to the solidification temperature or, under certain circumstances, below the solidification temperature, with the metal O is in the unstable equilibrium in the subcooling area

It follows that, under these circumstances, the total mass of liquid metals either on the

109843/1198

. Freezing temperature or brought into a range is, in which the metal is supercooled, the solidification can take place much faster than according to the previously usual procedure, with the solidification process below Release of a small amount of heat takes place and the solidification quickly in the entire liquid mass takes placeη

The method according to the invention also effectively prevents the formation of solidification bridges which occur in the last solidification phase of the liquid Metal takes place; these bridges favor the formation of voids in the axis of the blank o It is It can be clearly observed that the circulation of the liquid metal in the center of the blank with the phenomena the remelting of already solidified metal, as described above, a state of constant Maintains liquefaction throughout the zone in which the completion of the freeze is taking place, and so that the risk of developing insulated pockets with liquid metal, which provokes the formation of cavities, is considerably reduced »

According to the method according to the invention, they can also Induce changes in the crystal structure of the portion of the recovered product

It is known that in the case of continuous cast blanks obtained in the centrifugal casting process, a basalt-like structure occurs, resulting from the formation of solidification dendrites, while in the middle crystallization occurs with essentially unidirectional crystals. According to the invention it is possible to significantly reduce the occurrence of basalt-like structures

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13 i $ U

favor rectified crystal structures = zusehränkenj which phenomenon is probably due to the fact that the strength of the solidified metal ₈ is reduced by "moderately to a temperature brings _s which is during the Eretarrungsvorgangs same for all points substantially equal to the metal and the close the Erstarrungstem * = temperature _s or even lies below is caused whereby a solidification of the metal, which is comparatively "bar a sudden solidification of the total mass"

Incidentally, it is also clear that the fact _s that the strength of the solidified wall is maintained at a low value when the heat contained in the liquid metal in the interior of the blank to be discharged (which is join with the rotation), a pre = partial from the thermal point of view means because of the obstacle to heat exchange formed by the solidified part of the blank

According to a preferred embodiment of the invention, a first zone ,, in which the liquid metal circulates, below the first zone provided on the _s, the cooling takes place by spraying and the ansetzte immediately below the mold or mold

According to the invention it is also advantageous "two zones for the circulation of the liquid metal vorzu = see ξ these zones are located between zones inten" siver cooling, wherein the first, upper zone circulating liquid metal the purpose of _s is the strength of the already solidified limiting wall or ₉ by the liquid is Me "tall introduced in a luetand may even? \ x ,, Decrease of his

109 8 4-3 / 1198

rapid and homogeneous solidification allowed while the second _B lower zone with circulating liquid metal preferably in the vicinity of the range provided is that corresponds to the mitt * »leran portion of the ingot to the completion of solidification, wherein the circulation of the liquid metal at this point allows to work effectively against the formation of solid bridges, which favor the formation of pockets with liquid metal, which in turn lead to undesired formation of voids ₀

Since the electromagnetic fields according to the invention produced have only the purpose to bring about a circulation of the liquid metal, these fields preferably operate at a low frequency, Z ₀ B _n below 100 Hz ₁ In practice, it would be expedient to use industrial rotary stream of SO Hz, it but nothing speaks against it, much more in favor of using currents of much lower frequency, Z ₀ B ₀ of 5 »20 Hz-

In order to achieve the required effect, the currents flowing through the inductors must be very strong, for example 2000 to 10 000 A ₀ the inductors are placed <,

Since the work is done with such low voltages, there is no risk of arcs forming between the inductors and the parts they surround, and you can even continue the cooling of the blank by spraying water π in the area of the inductors

According to a preferred embodiment of the invention

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13 23 *

If the device is the electromagnetic one Fields to induce the circulation of the liquid metal generated from a series of inductors, those made of cylindrical copper disks which are laid one on top of the other and between which there is one Electrical insulation material with high heat resistance is found

As an isolating agent, e.g. that under the trade = Material distributed under the name "Sindanyo" may be used ο

The inductors thus have a single turn » and each turn is separated from the neighboring turn by an insulator plate? This way everyone can Plate be designed as a cylinder, which simplified the mechanical structure of the inductors

According to a preferred embodiment, the cylindrical inductors can also be provided with narrow bores for inserting nozzles which spray cooling water into the interior of the inductor against the surface of the blank, whereby the blank can be cooled during the solidification process and also the inductors c

The liquid metal check may be in the middle part of the raw "astride as desired, either-fen top to bottom or from bottom to move above However, it is recommended in the Einrichtungj dis the circulation of the liquid metal in the vicinity of the zone of the blank causes the almost completely is solidified, let the liquid metal flow according to the invention so that the metal descends in the middle part and in the edge area of the funnel made of liquid metal in the vicinity of the

1 0 9 8 4 37 ¹ I ⁹ I § 8

/1

solidified wall _: the blank again · rises »

It is also the purpose of the invention to produce a new industrial product that can be made from a rod consists of steel or a similar metal, which is manufactured according to the method described, wherein the rod is characterized »that it has good metallurgical properties also along its axis, in particular free from voids and uniform Distribution of the inclusions in a large volume area of their central part, and that the basalt » like solidified edge zone in favor of the central zone with solidification in crystal structures aligned in the same direction is reduced *

In order to clarify the invention, several embodiments ₉ which do not represent a limitation of the invention are explained by way of example with reference to the accompanying drawings. The drawings show 5

Fig. 1 in schematic form a representation of an Aus embodiment of the invention;

2 shows a sectional view on a larger scale of a device representing, in the invention the circulation of the liquid metal is brought about inside the blank;

Fig. 3 is a section along the line III-III in Figo 2}

Figo * t ind 5 two circuit diagrams for the electrical arrangement of the inductors according to the invention

In Figc 1 is a centrifugal casting device is schematically

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shown for continuous casting ₀ In the upper part you can see the continuous casting nozzle 1, which directs the jet 2 of liquid metal, which is intended for the production of the blank o The solidification begins in a casting mold or mold 3, which in a known manner by means of a water circuit ( Water inlet according to arrows Jf ₁ and water discharge according to arrows f ₂ ) is cooled «This creates a solidified outer skin» which holds the liquid metal S together during the further solidification process »

In a manner known per se, the bark 4 and the liquid metal 5 existing blank with drive rollers that support it in the axis of rotation and pull it vertically downwards, guided

In order to simplify the drawings, these rollers, which are used for guiding and pulling off, are not shown »

Below the mold 3, the blank is vigorously through Spraying of water from the nozzles 6 cooled in a manner known per se »

This results in a reinforcement of the solidified metal skin with a corresponding reduction in the liquid part that has remained inside the blank. At the same time, the reduction in the outer diameter of the blank, which occurs as a result of cooling occurs, supports »

According to the invention, an arrangement 7 is provided below the cooling zone defined by the spray nozzles 6, that of the creation of circulatory streaks in the liquid metal serves as it has been explained above »

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The Figo 1 can be seen, moreover, that the occurrence of these circulation flows result has * that the wall thickness remains substantially unchanged while a temperature compensation and a drop in the overall temperature of the liquid metal takes place ₀

Below the inductor device 7 there is a further cooling zone which has spray heads 8, the Spray water on the outside of the blank «In In this zone, the liquid metal 5 solidifies more quickly because of the homogenization of the temperature and achieved in the area of the inductors 7 the lowering of the mean temperature of this liquid »

According to this embodiment, there are located below the cooling zone formed by the spray heads 8 of the invention inductors 9, which form a second zone with circulating liquid metal o As in Fig. indicated schematically, this second zone is located near the area of the solidification closure of the liquid metal sc. According to a preferred embodiment of the invention, the inside of the liquid Metal induced currents such that the metal flows down and down the axis of the blank ah the solidified metallic Wtlang run upwards »

Finally, further spray heads 10 are arranged below the inductors 9 in order to continue the cooling of the blank.

In Figures 2 and 3 is on a larger scale current-inducing device 7 drawn from FIG

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According to Figures 2 and 3, the induction device consists of three inductors H ₉ 12 and 13, which are separated from each other and which are held by plates 14, 15, 16 and 17 made of heat-resistant electrical insulating material

To simplify the assembly, these insulating plates If ₉ IS ₉ 16 and 17 have a square shape »as can be seen from Figo 3 SU

These insulation panels can for example be made of the material sold under the trade name "Sindanyo" *

Figures 2 and 3 algen that the inductors 11, 12 and 13 are equal to one another »They consist of a flat copper rod that has been so deformed that it becomes one forms a single winding, the ends of which ila and 11b separated from one another by an insulating piece 18 and attached to the Power source are connected o

In the embodiment according to Figures 2 and 3 are the electrodes 11, 12 and 13 pierced, and in the bores there are spray heads 19 through which a Cooling water jet can be directed onto the outside of the blank "which runs inside the induction arrangement". With this cooling water, both the inductors as well as the insulating plates separating them are cooled

The induction arrangement described can be set in rotation independently at the same speed as the blank, but it can also be held in place to make it easier to attach the device _{or the like}

-W-

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BRANCH

Furthermore, the bark of solidified metal can be seen in FIGS. 2 and 3, which holds the liquid metal 5, which is subjected to thorough mixing as a result of the circulation according to the invention _D

In Fig. 2, a direction of circulation is indicated by arrows of the liquid metal 5 indicated, after which the metal in the vicinity of the axis.des blank down flows while it rises at the edge along the inside of the solidified metal skin 1 o Of course this direction of rotation of the liquid metal is determined by the electrical switching of the inductors 11, and 13 certain

In Fig. H the circuit diagram for the power supply of the inductors 11, 12 and 13 is drawn.

A three-phase transformer connected to a three-phase network is used for this o In Figc H are the three primary windings 20, 21 and 22 of the three-phase transformer drawn, its secondary windings in the present case by the individual turns 23, 2 * » and 25 are displayed «

It is of course possible to work with transformers that have a slightly on the secondary side have a larger number of turns. However, it is It is recommended that the number of turns of the secondary windings of the transformer be as low as possible to hold, because you are at the lowest possible voltage at the connections of the inductors 11, 12 and 13 interested.

As the figure shows, every turn is secondary

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connected to an inductor in such a way that an electromagnetic field is generated which is displaced in the vertical direction along the axis of the blank _{or the like}

_{The field is a field 0} pulsating with the frequency of the three-phase transformer

With this circuit it is possible to generate a current from a three-phase network of 3100 V between the phases to get der.mit about 5000 to 6000 A at a voltage of about 1 V through each inductor ο

Of course, one remains within the scope of the invention if one uses the inductors 11, 12 and 13 described, the have a single turn, through inductors of the usual type with a limited number of turns, with about 5 turns, replaced

In Fig «S is the circuit diagram for the supply of six inductors divided into two groups of three inductors each by means of a three-phase transfer = mator drawn; the inductors are connected in pairs, one behind the other, in a circle that is connected to the The secondary side of the transformer was lying

Under these circumstances the same effect of the circulation of liquid metal in a larger area of the blank is achieved »

In the context of the invention, it is possible to use inductors with multi-phase current, but instead of with Three-phase current can be fed with six-phase current, for example «

«= 16 =» 1 0 9 8 A 3/1 1 9 8

13 13 «4

The invention thus shows a simple way »to get inside the liquid metal during the first» to generate circulation flows, which develop vertically along the axis of the blank and superimpose the rotation

The procedures described here are intended as a Examples are to be understood within the scope of the invention any possible variations that may be required

In particular, the number of induction arrangements attached to a continuous casting plant can obviously be as large as desired, with each induction arrangement in turn being equipped with a different number of indications, provided that only an electromagnetic field is induced that causes a displacement of the liquid metal. Also dia electrical data, which have been mentioned in the foregoing description, serve only possible for explaining embodiments, and it goes without anoint _s that the electrical values in each particular case, * in particular depending on the dimensions of the blank are particularly determined must “However, the electrical currents fed to the inductors must be chosen so that the heating remains as successful as possible. Therefore, it is particularly important to use low-frequency currents

Since the electrical effects Lh wesesfttlisteB b @ ixa Plies <sen of a very strong Str-c ^ a are obtained in the Indmktörön, the tvii ^ liäii & u .i ^ i ^ ktormi άά n & lw should be low voltages ,, υι · 4 ^{:. !} ^ Ηΐ «i ils. isöXatiü ^ aschwlerigkeitsn seha ⁵ vei-iäd ^ 'te;:,; ri ^% rf ί /; ΐ "?:.}: ₄ « ϊ "ϊ danger> 3 a cooling by Auispsd tintr. y -,; .. i i- | j ,; _; j «nr Ja Beadi-i * üsr Indo} ctoren success« «k ^ äiB» --..-..-. ^.

Claims (1)

A centrifugal casting process for the production of continuous castings from steel and similar metals, characterized in that, during solidification, the blank in at least one zone causes an axial circulation of the liquid metal Ci) inside the blank with the aid of electromagnetic fields i ^, which are generated by inductors C7, 9) arranged around the blank »method according to claim 1, characterized in that the circulation of the liquid metal <5) near the axis of the blank when solidifying in one direction and near the The outer surface formed by the solidified metal takes place in the opposite direction. The method according to address 19 is characterized by the fact that the liquid metal (5) circulates in a zone during the first phase of the blank takes place, in which the resulting® GuShaut CH) © ine Star = ke has »which is essentially the same as half the radio of the blank. sm ums1 Aasp ^ öahe 1 to 134, characterized in that a circulation of the liquid metal (5) takes place in a zone of the blank which corresponds to the completion of the first getting of the liquid metal (S) Circulation of the liquid metal (5) in the zone 6 of the blank is brought about, which is close to the completion of the solidification, and that the metal flows downwards near the axis of the blank and upwards along the already solidified walls. 6c Method according to one of Claims 1 to 5, characterized in that the circulation of the liquid metal (5) is brought about by the electromagnetic field which is generated by a group of several inductors which are arranged on the edge of the blank, and in each case are fed by one phase of a multiphase current »Method according to claim 7, characterized in that currents with a current strength between approximately 2000 and 10 OQO A flow in the inductors. 8c Method according to claim 6 or 7, characterized in that a low voltage, for example of a few fractions of a volt or a fair volt, is applied to the inductors "- 19-109843/1198 to method according to one of claims 6 to 8, characterized characterized in that a low-frequency polyphase current is used which has, for example, a frequency below XOO Hz and preferably a frequency between § and 60 Hz. Method according to one of the preceding claims, characterized in that cooling water is sprayed on in the area of the inductor arrangement, the device used to cool the blank and to maintain a low temperature of the inductor arrangement that a group of inductors with a single cylindrical turn (CIl) is provided, that each inductor is separated from the adjacent inductor and that it is held by a plate of insulating material which is insensitive to a certain increase in temperature. Device according to claim 11, characterized in that at least one of the inductors (7, 9) is provided with at least one bore in which a water spray head (19) is arranged to cool the blank and the inductor arrangement made of steel or a metal with equal - 20 - 109843/1198 1.3 in 211520a Properties »produced according to the process one of claims 1 to 11, characterized in that it is outstanding in its central area Has metallurgical properties, in particular has no voids and a uniform distribution of Inclusions in a large volume of metal, and that the edge zone with a basalt-like crystal structure is reduced is in favor of the central zone with a crystal structure in the same direction ο - 21 109643/1198