WO1993022085A1

WO1993022085A1 - Method of obtaining double-layered cast piece

Info

Publication number: WO1993022085A1
Application number: PCT/JP1993/000530
Authority: WO
Inventors: Eiichi Takeuchi; Masafumi Zeze; Takashi Sawai
Original assignee: Nippon Steel Corporation
Priority date: 1992-04-24
Filing date: 1993-04-23
Publication date: 1993-11-11
Also published as: CA2112585A1; EP0596134A1

Abstract

A method of producing a double-layered cast piece by injecting molten metals (13A, 14) of different compositions into molten metal pools (1A, 1B) which are separated vertically from each other by a DC magnetic field zone (2A) provided in a casting mold (1), which method comprises inserting an alloy wire (12) into a shorter immersion nozzle (4), which is provided on a continuous casting tundish (3), through a through bore in a tundish stopper (6) to melt the wire (12), mix the resultant molten alloy with a molten metal (13) in the nozzle (4) and produce a molten metal (4) of a uniform concentration, supplying this molten metal (4) from a discharge port of the shorter nozzle (4) to an upper molten metal pool (1A) while supplying a molten metal (13) as it is from a longer immersion nozzle (5) provided in the continuous casting tundish (3) to a lower molten metal pool (1B), and cooling and solidifying the molten metals in these pools into a double-layered cast piece.

Description

Description Multilayer monolithic manufacturing method Technical field

In the present invention, in continuous steel making, molten steel of different composition is injected into molten steel pools separated vertically by a DC magnetic field zone provided in or below the mold, and the surface layer and the inner layer have different compositions. The present invention relates to a method of manufacturing a multilayer piece made of steel. Background art

Conventionally, the present inventors have divided a series of strand pools into upper and lower parts using various types of DC magnetic fields, and injected molten steel having a different composition into each of them by a separate immersion nozzle. We have proposed and implemented a method of manufacturing multi-layer pieces with the surface layer and the inner layer made of steel with different components while minimizing the mixing of steel types.

For example, Japanese Patent Application Laid-Open No. 63-108947 discloses a technique of using a magnetic flux band having a uniform density in one piece width direction from one side of a long side forming a piece to the other side. In Japanese Patent Application Laid-Open No. 309436/1991, a technique using a magnetic flux band parallel to the pulling-out direction of a piece is disclosed. We have also proposed manufacturing methods using a DC magnetic field with a configuration that is drawn from the periphery of the cross section to the center of the cross section, or vice versa.

However, in these processes, in principle, two types of molten steel are smelted using converters, electric furnaces, ladle, vacuum degassing equipment, etc., and transported separately to a continuous machine. After that two Inject into each tundish, and then use the immersion nozzles provided in each tundish to flood the two types of melt into the upper and lower melt pools in the mold, respectively, and pull out through the continuous cycling process It was intended to produce multilayer pieces.

In this way, the two types of ingots are separately melted, which is configured to produce a single-layered piece of cycline, and greatly reduces production efficiency in a manufacturing plant where various improvements have been made. It often caused drastic improvements as a fundamental problem of this process.

To solve this problem, Japanese Patent Application Laid-Open No. 63-108947 has already proposed a method of adjusting the composition by adding a wire to molten steel in a molten steel boule. In some cases, the composition did not become perfect.

In order to improve this problem, Japanese Patent Application Laid-Open No. 3-243245 has proposed a technique for stirring and mixing a solute added by a wire with an electromagnetic stirrer to make the solute concentration uniform.

However, when the solute is directly converted into a wire from the molten metal surface in the mold or added by a wire coated with a metal such as iron, as shown in Fig. 7, If no measures are taken, this powder will adhere to the wire 12A when passing through the powder layer 16 or the molten portion of the powder layer 16 in the mold 1, and this will become the remelted powder 22 and melt.鐧 It was predicted to be drawn into the melting pool of 13A and 15 and to lead to a defect inside the piece. Reference numeral 21 denotes a solidified layer of steel adhered to the periphery of the powder 20 solidified around the wire. As shown in Fig. 8, a wire 12A is added at the point where the wire 12A enters the molten metal surface, using a refractory guide tube 23 so that the powder layer 16 does not directly contact the wire 12A. However, in practice, the temperature of that part decreases and the molten steel solidifies and adheres to the periphery of the welding guide tube 23, which may hinder operation. Further, even if the problem of the powder layer 16 is solved, if the concentration of the components after the dissolution of the wire 12A is not sufficiently achieved, 铸 one circumferential direction or 铸 one piece length direction However, it is not possible to produce homogeneous multilayer pieces.

As a means to cope with this problem, it is not impossible to equalize the component concentration by electromagnetic stirring as described in JP-A-3-243245 as described above, but stirring at a position that affects the DC magnetic field band is not impossible. In some cases, the separation of components may not be successful.

On the other hand, a technique for adding a wire-like treating agent in a pouring nozzle to molten metal injected into a mold is disclosed in Japanese Patent Application Laid-Open No. Sho 51-32432.

This technology takes a deoxidizing agent and adds it to the confined flow of metal flowing from the bevel into a 铸 shape, and also prevents the continuous operation from being hindered by the improper deposition of the high-melting oxide of the additive treatment agent. This technology supplies the treating agent to the ladle nozzle through the central through-passage of the stopper rod. In this technology, the reaction product between the molten metal and the solute enriched by the wire addition during the wire addition, and the reaction product between the nozzle constituent material and the solute enriched by the wire addition, are generated in the nozzle. The contact time between the nozzle constituents and these reaction products is short because the flow rate of the molten metal passing through the nozzle is high, and the deposition of these reaction products on the nozzle wall is not significant.

Therefore, in this technique, the molten metal flow flows out of the discharge end of the short nozzle through the atmosphere to the 液 type liquid surface, and falls to the liquid surface of the mold. Due to the limitation, the treating agent cannot be added in a large amount and in a uniform concentration. Disclosure of the invention

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an advantage in that the composition of molten metal such as molten steel used in the process can be easily adjusted, and the production cost can be drastically reduced. The purpose is to provide a method of construction.

Another object of the present invention is to provide a method for producing a multilayer piece in which the concentration distribution of the components of the outer layer and the inner layer is uniform and can be continuously produced without interruption.

In order to achieve the above object, the present invention firstly injects, for example, a molten steel into a molten metal pool composed of a 铸 type and a damper bar by means of short and long nozzles provided in the lower part of the tan dish, and A magnet provided at a fixed distance from the meniscus in the manufacturing direction forms a DC magnetic field zone acting over the entire width of the piece to divide the molten steel up and down to form a continuous strand pool. I do. Therefore, the tip of each of the short nozzle and long nozzle is immersed in each pool.

Next, an alloy wire for component adjustment is added to one or both of the immersion nozzles, sufficiently dissolved in the immersion nozzle, and mixed to adjust to a predetermined concentration.

The molten steel whose concentration has been uniformly adjusted as described above is discharged into each pool. Subsequently, the molten steel is rapidly cooled and solidified to form a multilayer piece having a uniform concentration in which the surface layer and the inner layer are composed of the respective metal species. .

Thus, the present inventor, when producing a multilayer piece,

(1) Molten steel in the tundish should be one type of component. A) A DC magnetic field zone should be provided in the mold to separate the molten steel into upper and lower pools in the mold.

(3) Each time a long or short immersion nozzle is used to inject molten steel into each pool, (4) The desired additive alloy to be made into a multilayer component is sufficiently dissolved and mixed in the immersion nozzle to make the additive alloy concentration uniform.

Etc. are necessary, and in order to reliably implement the present invention,

(5) injecting an inert gas into the immersion nozzle;

is important.

An inert gas such as Ar gas is blown into the molten metal flow in the nozzle from the wire addition port at the tip of the stopper or from the upper part of the nozzle wall, and finely dispersed in the fluid, so that the inside of the nozzle is immersed throughout the length of the immersion nozzle This suppresses the adhesion and deposition of the reaction product of the dissolved substance and the molten metal and the reaction product of the material constituting the nozzle on the nozzle wall, thereby preventing the flow resistance in the nozzle from increasing.

As in the present invention, when the nozzle length is long, the lower part of the nozzle is immersed in the molten metal, and when the direction of the flow path is changed at the nozzle tip, the flow resistance of the entire nozzle increases, and Injection of inert gas into the immersion nozzle is extremely effective in continuous operation for a long time, because the injection of molten metal into the immersion nozzle tends to be hindered.

In the present invention, in order to smoothly adjust the flow rate to each pool, two tundishes into which the same type of molten metal is injected are arranged, and a short nozzle or a long nozzle is separately provided in each tundish. You may.

In this case, it is of course possible to inject a different kind of metal into each tande dish, and then feed the additive alloy wire to the immersion nozzle communicating with the pool requiring further component adjustment. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an overall schematic diagram of a partial cross section showing an embodiment of the present invention. FIG. 2 is a partially enlarged sectional view of FIG. FIG. 3 is a schematic sectional view showing a main part of another embodiment of the present invention. FIG. 4 is a schematic sectional view showing a main part of another embodiment of the present invention. FIG. 5 is a schematic sectional view showing a main part of another embodiment of the present invention. FIG. 6 is a schematic sectional view showing a main part of another embodiment of the present invention. FIG. 7 is a schematic sectional view showing a main part of a conventional example.

FIG. 8 is a schematic sectional view showing a main part of another conventional example.

Fig. 9 is a diagram showing the concentration distribution of Ti in a section of the present invention _c Fig. 10 is a diagram showing the concentration distribution of Ti in a section of the prior art _c Fig. 11 shows the measurement of the Ti concentration FIG. 5 is a sectional view of a half piece showing a position where the cutting is performed. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

FIG. 1 schematically shows the whole of an apparatus for carrying out the present invention, in which a magnet 2 is disposed below a mold 1 and the magnet perpendicularly extends in the machine direction (A). DC magnetic flux is applied in the direction across the thickness of the piece to form a static magnetic field zone 2 A, and an upper molten metal pool 1 A and a lower molten metal pool 1 B are formed in the mold. A tundish 3 for storing, for example, molten metal 13 is arranged at the upper part of the mold 1, and a short immersion nozzle 4 opening into the upper pool 1 A and a long immersion nozzle 4 opening into the lower pool IB are provided at the bottom of the tundish. An immersion nozzle 5 is provided.

The figure shows a state in which an additive alloy wire 12 is fed into the short nozzle 4 in order to adjust the composition of the molten steel to be injected into the upper pool 1. In the figure, reference numeral 6 denotes a tundish stopper of the short nozzle 4, which has a through-hole 6A for the alloy wire 12 and opens and closes a tandem opening 3A as shown in detail in FIG. Above the stopper 6, a seal mechanism 8 including an inert gas filling chamber 8A, a labyrinth seal 8B, and the like is provided. 9 is a straightening machine for wire drawing, 10 is an alloy wire feeding device The reference numeral 11 is a caller.

As shown in FIG. 2, the short nozzle 4 is formed so as to be integrated with the bottom of the tundish at the tundish opening 3A, and is connected to the inert gas inlet 18 as necessary. A connecting porous refractory 17 is provided.

In the above apparatus, after forming a molten steel pool between the mold 1 and a damper (not shown), the stopper is opened, and molten steel 13 in the evening dish 3 is poured into the molten steel pool. When the depth reaches the predetermined pool depth, the static magnetic field zone 2A is formed to form the upper and lower molten steel pools 1A and 1B, and then the alloy wire 12 is fed into the short nozzle 4. The alloy wire 12 is melted and mixed in the short nozzle 4, adjusted to a predetermined concentration, and discharged to the upper pool 1A.

Thus, in order to form the molten alloy 14 with the adjusted alloy concentration in the upper pool 1A, that is, the molten metal for the surface layer, it is necessary to satisfy the following equations (1) and (2).

L N <L + L M (1)

L N> (V X d) / 2 f (2)

Here, the average melting speed of the alloy wire 12 is f, the diameter of the wire is d, the addition speed of the wire is V, and the stopper is in a state where the opening of the tundish is closed. The distance from the tip of the stopper 6 to the meniscus 14 B in the mold is L _M , the distance from the tip of the stopper 6 to the immersion nozzle discharge port 4 A is L _N , and the distance from the meniscus 16 to the DC magnetic field zone is L M. Let L be the distance to the center position 2B of the.

The length of the long nozzle 5 for pouring the inner layer molten metal 13A, that is, the distance from the tip of the stopper 7 to the nozzle discharge hole 5A is the distance L of the center position 2B of the static electromagnetic band. It should be longer.

When the melt 13 is poured into the mold 1 as described above, the surface melt 14 in the upper pool solidifies to form a solidified shell 14A, and the melt for the inner layer is sequentially formed. 13A is also solidified to form a solidified shell 13B, and a multilayer piece having an outer layer 14A and an inner layer 13B having a uniform concentration distribution is finally pulled out from the mold.

Further, the amount of the inert gas, for example, the Ar gas blown into the pouring nozzle is desirably in the range of 0.1 to 15.0_β / min. That is, a structure that is stable for a long time in this range becomes possible.

In the embodiment shown in FIG. 3, the alloy wire 12 is fed into the long nozzle 5 through the stopper 7 in the apparatus shown in FIG. 1 to form the inner layer molten metal 15 having a uniform concentration of the added alloy, and the surface layer 13 is formed. This is an example of manufacturing a double-sided piece composed of B and an inner layer 15A to which an alloy is added.

Fig. 4 shows that the alloy wire 12 is sent to the short nozzle 4 and the alloy wire 12A is sent to the long nozzle 5 via stoppers 6 and 7, respectively. An example is shown in which a multi-layered piece composed of a surface layer 14A and an inner layer 15A to which alloys are added is manufactured.

Figures 5 and 6 show the tundish separated into a tundish 3A for storing the melt 13a and a tundish 3B for storing the melt 13b, and the short nozzle 4 and the long nozzle respectively. Fig. 5 shows an example in which an alloy wire 12 is supplied to molten steel 13b to form an inner layer molten metal 15, and Fig. 6 shows an example in which alloy wires 12 are formed in molten metals 13a and 13b. This is an example in which 12A is supplied to form a melt 14 for the surface layer and a melt 15 for the inner layer. Of course, the alloy wire may be supplied only to the melt 13a.

Providing a tundish for each layer as described above allows more effective adjustment of the amount of molten metal in each molten metal pool, and is also advantageous when pouring different metals into each layer. .

In the examples shown in FIGS. 5 and 6, as in the example shown in FIG. By spraying the molten metal into the molten metal and finely dispersing it in the molten metal, deposits on the inner wall of the nozzle are reduced, and a multi-layered piece having a uniform concentration distribution in the circumferential direction and in the forming direction is stabilized. Example that can be built

Example 1

As shown in Fig. 1, the molten steel of the inner layer components shown in Table 1 and stored in a single tundish were mixed with a continuous copper machine with a long side of 1200 thighs and a short side of 250 gangs and a damper bar. Inject into the formed molten steel pool to a predetermined depth and apply a DC magnetic field with a uniform magnetic flux density of 5000 gauss in the width direction of the piece 铸 0.63 m below (distance L) from meniscus 14B in the mold. Band 2A (DC magnetic field center position 2B) was formed, and the pool was divided into upper and lower parts in the manufacturing direction.

铸 In order to make the surface layer O thickness D of the piece 25 mm, from the following formula (3), the 铸 piece extraction speed (铸 forming speed) Vc was set to O.AmZ.

D = 0.020X (L / Vc) 1/2 (3)

To achieve such a structure, the flow rate was controlled by adjusting the opening of each stopper so that the flow rate of molten steel for the surface layer was 3.36 kg / sec and the flow rate of molten steel for the inner layer was 11.04 kg / sec. When the surface molten steel passes through the short immersion nozzle 4, a wire having an A content of 70% was added into the nozzle at a rate of 1.44 gZ seconds. As a result, the A content of the obtained piece was 0.032% by weight as shown in Table 1.

When adding the A wire, Ag gas was added to the inside of the short nozzle at a rate of 0.5 iZ.

The multilayered piece was stably formed for 120 minutes, but the A concentration in the surface layer was uniform in both the circumferential direction and the lengthwise direction, and no entrainment of powder was observed. (Unit: wt%)

Example 2

A direct current magnetic field is installed at the bottom of a continuous copper mold to form a continuous piece with a long side of 1500 min and a short side of 200ππη, and the molten steel pool in the continuous strand is divided into two pools in the manufacturing direction. Then, the same ultra-low carbon steel was supplied to each pool with nozzles of different lengths, and solidification and drawing were performed. Here, the molten steel to be injected into each pool is stored in two tundishes, and the nozzle for injecting the molten steel into the lower pool corresponding to the inner layer has a through hole and a sealing mechanism as shown in Fig. 5. A wire (Ti content 70%) encapsulating a Ti alloy was added by the stopper 7 at a rate of 38.9 g Z seconds.

The center position 2B of the DC magnetic field was 60 cm below the meniscus 13C, the direction of the magnetic flux was the thickness direction of the piece, and the magnetic flux density at the center position was 5500 gauss. 7.75 kg / sec. Of molten metal for the surface layer while adjusting at a speed of 1 mZ-Adjust the opening of the stems 6 and 7 so that the molten steel pouring rate of the inner layer is 27.25 kg / sec. And controlled. The boundary between the upper and lower pools was located at the center of the DC magnetic field zone due to the solidification rate inside the mold of this connector, and the surface layer thickness was 20 mm. One

Here, Ar gas was added in an amount of 1 £ Z together with the wire from the tip of the dropper of the nozzle to which the wire was added. The construction was stable for 120 minutes and completely built all the ferrous steel.

The circumferential concentration distribution of Ti in the inner eyebrow thus manufactured is As shown in FIG. 9, 0.1% was consistent with the concentration estimated from the above manufacturing conditions, and was constant in the length direction.

FIG. 11 shows locations where the Ti concentration distribution was measured on the cross section of the piece.

Example 3

A structure was produced under the same conditions as in Example 12 except that no Ar gas was added. As a result, about 55 minutes after the start of the production, the supply of molten steel to the inner nozzle to which the Ti wire was added was reduced, and it became difficult to maintain the predetermined 27.25 KgZ seconds. As a result, mixing occurs between the upper pool and the lower pool.- The Ti concentration in the inner layer was obtained from about 55 minutes after the start of the production. 80 minutes after the start of construction, supply of molten steel for the inner layer became impossible, and the structure was interrupted. ₍ After completion of the construction, the inside of the nozzle was inspected, and the refractory of the nozzle and Ti reacted. The product was observed to adhere and accumulate on the nozzle wall.

Comparative Example 1

Production was performed under the same conditions as in Example 1-2. However, as shown in Fig. 7, the wire 1 was added from the inner powder layer toward the inner pool without passing through the stopper. Here, the wire is coated with iron and adjusted to melt for the first time in the inner layer.

Although the structure was stable and completed, the flakes after the structure were examined. As shown in Fig. 10, a large variation in the inner layer Ti concentration was measured in the circumferential direction of the flake. One

In addition, a large amount of powder, which was thought to have been caught in the meniscus when the wire was added, was detected inside the piece.

The Ti concentration measurement position was as shown in FIG. 11, and the wire addition position was as indicated by 24 in the figure. Industrial applicability

As described in detail above, in the present invention, when continuously forming a multi-layered piece, the molten steel having the same base composition is melted without previously melting the molten steel having the two different compositions. When the surface layer or both of the molten steel are injected into the mold from the tundish, a wire is added from the tundish stopper, melted and uniformly mixed in the dipping nozzle, and mixed into the specified molten steel pool. By injecting into powder, it is possible to easily adjust to the desired molten steel composition, and also to reduce the entrainment of powder, and to stably produce for a long period of time. And improve chip quality.

Claims

The scope of the claims

1. Molten metal is supplied to each of the molten metal pools separated vertically by a DC magnetic field zone provided in the continuous structure or below the mold. The multilayer structure consisting of a surface layer and an inner layer In the multi-layered / single piece manufacturing method for manufacturing pieces,

A short immersion nozzle and a long immersion nozzle are provided on a continuous tundish disposed above the mold, and the molten metal is supplied into the upper molten metal pool via the short immersion nozzle; and When supplying molten metal into the lower molten metal pool via the shaking immersion nozzle, either one of the tundish stoppers detachably provided in the two molten metal discharge holes of the continuous tundish A through-hole is provided in the center of the stopper, and an alloy wire is inserted into the through-hole, and the alloy wire is melted in the immersion nozzle to produce a molten metal having a desired composition in one molten metal pool. And producing a multilayer piece by supplying the molten metal from the molten metal discharge hole of the other metal to the other molten metal pool through a dipping nozzle. Piece manufacturing method.

2. A through-hole is provided at the center of both ends of the tundish stopper, and two types of alloy wires to be added are inserted into the through-hole and melted in each immersion nozzle to melt the desired composition. The method of claim 1 wherein the metal is produced in each molten metal pool.

3. The method according to claim 1, wherein an inert gas is supplied into an immersion nozzle into which the alloy wire is inserted.

4. A multi-layer piece consisting of a surface layer and an inner layer by supplying molten metal to each of the molten metal pools separated vertically by a DC magnetic field zone provided in the continuous structure mold or below the mold. To manufacture multi-layer flakes hand,

A molten metal of the same composition is dispensed into two tundishes arranged above the mold and dispensed into each tundish.

c Supply the molten metal from the dish to the upper molten metal pool via the short immersion nozzle, and supply the molten metal from the other tandem via the long immersion nozzle to the lower molten metal pool. At this time, a through-hole is provided in the center of one of the tan dish's stoppers detachably provided in the molten metal discharge holes of the two continuous tundishes, and the through-hole is made of an alloy. A wire is inserted and the alloy wire is melted in the immersion nozzle to produce a molten metal having a desired composition in one molten metal pool, and the molten metal is discharged from a molten metal discharge hole of the other tundish. A method for producing a multilayered piece, comprising supplying the molten metal pool to the other molten metal pool through an immersion nozzle.

5. The method according to claim 4, wherein molten metals having different compositions are dispensed into the two connected tundishes.

6. Dispose molten metal of different composition to each tundish by arranging the two connected tundishes, and provide through holes in both central parts of tundish stoppers provided in each tundish. 5. The molten metal pool according to claim 4, wherein two kinds of alloy wires to be added are inserted into the through holes and melted in each dipping nozzle to produce a molten metal having a desired composition in each molten metal pool. Method.

7. The method according to claim 4, 5 or 6, wherein an inert gas is supplied into an immersion nozzle into which the alloy wire is introduced.