JPS6149750A - Continuous casting method of clad steel billet - Google Patents

Abstract

PURPOSE:To weld satisfactorily the entire surface of a clad steel billet and to improve product yield in continuous casting of the clad steel in which a molten metal is supplied, welded and quickly cooled onto the surface of a moving steel strip by pouring the molten steel onto the preheated steel strip which is held at both ends by L-shaped refractories and cooling quickly the intermediate part after prescribed time. CONSTITUTION:The steel strip 6 which is preheated to an adequate temp. in a preheating furnace 12 is held at both side ends by the endless L-shaped refractories 16 to prevent the outflow of pouring 5 and to insulate both side parts, by which the welding is improved. The intermediate part is quickly cooled by spray nozzles 15 while both sides are held insulated upon lapse of the prescribed time after the pouring 5. The clad steel billet 10 has the defectless weld quality without the unwelded part and the product yield is improved.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides a clad copper cast slab that can efficiently produce high-quality clad steel slabs at low cost and with a high yield through continuous casting. This relates to a method for constructing a series of pieces.

[Prior art and its problems]

The following methods are known as methods for manufacturing clad steel materials.

(1) Rolling method (2) Explosion bonding method (3) Overlay method (4) Casting method The rolling method involves overlapping the base material and cladding material and welding four circumferences.
This method consists of crimping by hot rolling.

However, this method requires time and effort in pre-rolling, such as polishing the surfaces to be joined, then welding the four circumferences, and creating a vacuum between the base material and the laminate to prevent oxidation. , manufacturing cost is high and mass production is difficult.

The explosive bonding method is a method in which a base material, a laminate material, and gunpowder are layered and bonded together using shock waves from an explosion. Although this method has the advantage of being applicable to a wide range of metals, there is an upper limit to the area that can be manufactured, and because it uses expensive explosives, the manufacturing cost is extremely high, and the explosion noise is loud. There are also environmental issues.

The overlay method is a method that involves directly overlaying and welding a cladding material onto the surface of a base material. Although this method has the advantage of being able to form a cladding after forming the base material, it requires a lot of effort in welding and is not suitable for manufacturing large-area products, resulting in poor productivity.

In the casting method, a composite steel ingot is prepared by setting a composite material in a mold, injecting molten steel as the base material into the mold and casting the composite material, and then rolling this composite steel ingot. This method consists of crimping. However, this method requires a cladding material with a thickness exceeding a certain dimension, which limits the cladding ratio and requires measures against inclusions, oxidation of the surface of the laminate material, etc. , has a neck. In particular, the biggest problem is that the yield is significantly reduced by a large amount of χ due to melting loss of the laminate and changes in the cladding ratio due to metal flow during rolling.

As mentioned above, all conventional methods for manufacturing clad steel have low productivity and high manufacturing costs, so the reality is that it is difficult to achieve cost benefits and increase demand.

Therefore, in recent years, research has been conducted on methods for manufacturing clad steel slabs by continuous casting, and for example, the following methods are known.

(1) A method for continuously manufacturing clad steel slabs by continuously inserting clad steel strips into the inner wall of a continuous casting mold according to the casting speed (Japanese Patent Laid-Open No. 51-11
No. 1458).

(2) By supplying molten steel as a base material to the surface of one cladding steel strip or between a pair of cladding steel strips and welding the molten steel to the cladding steel strip, a clad steel cast slab is produced. (JP-A-53-2341, JP-A-58-65549) (3) Laminated steel along at least one side of a pair of endless heat-resistant recursive rings whose backs are forcibly cooled. A method for continuously manufacturing clad steel slabs by supplying molten steel as a base material while rolling the strip (Japanese Patent Application Laid-open No. 119438/1983).

However, in the methods (1) and (2) above, since the clad steel strip and the molten steel as the base metal are completely welded,
Although the contact interface between the two needs to be at a certain high temperature (e.g. solidus temperature), since the clad steel strip is at room temperature, even if molten steel is supplied as the base material, While it takes time for the interface temperature to reach the temperature required for welding, a solidified shell is likely to form in the molten steel due to contact with the low-temperature cladding steel strip, so there is no space between the cladding steel strip and the molten steel. There is a whistle while the weld area occurs.

In the method (3) above, cooling is performed via the heat-resistant repeating ring band, and since the clad steel strip and the heat-resistant repeating ring band are moving synchronously and at the same speed, there is no uneven contact between them. If this happens, it immediately causes uneven cooling, and there is a problem that the welding condition at the interface between the cladding steel strip and the molten steel as the base material tends to become uneven.

Furthermore, the methods (1), (2), and (3) above have the following problems. That is, both sides of the laminate steel strip to which molten steel as a base material has been supplied are likely to be cooled, as well as the center, so that unwelded portions are likely to occur on both sides. In such unwelded parts, even after subsequent hot rolling, sufficient adhesion cannot be obtained due to oxidation of the unwelded interface.Furthermore, the widthwise ends of the clad steel slab are unbonded and open. As a result, oxidation progresses to the unbonded interface at the center in the width direction of the slab, making it extremely difficult to bond between the laminated steel strip and the molten steel gutter even during the subsequent hot rolling stage. , therefore, it is not possible to obtain a clad steel material of excellent quality.

[Purpose of the invention]

Therefore, it is an object of the present invention to produce a clad copper slab of excellent quality, which has a sound welded interface, and in particular has complete welding on both sides of the slab, when manufacturing a clad 8+1 slab by continuous casting. The object of the present invention is to provide a method for stable and continuous production with high yield.

[Summary of the invention]

The method of the present invention involves supplying molten steel as a base material onto the surface of a continuously moving cladding band or between a pair of cladding bands, and transferring the molten steel to the laminate conditioning band. The siflad steel slab is continuously welded to the strip, and then the surface of the cladding strip opposite to the welded surface of the molten steel is forcedly cooled to solidify the molten steel welded to the cladding strip. In a method for continuous casting of clad steel slabs manufactured by Both sides of the cladding band to which molten steel has been supplied are held by L-shaped refractory holding members to prevent the molten steel from flowing out from the both sides and to keep the both sides warm; The method is characterized in that the middle part of the cladding band to which the molten steel is supplied is forcibly cooled on the side opposite to the welding surface of the molten steel after a predetermined period of time has elapsed since the molten steel was supplied.

[Setup of invention]

FIG. 1 shows an apparatus for producing a single-sided clad steel slab by supplying molten steel as a base material onto the surface of one cladding strip, as one embodiment of the apparatus used in the method of the present invention. FIG. A tundish 2 is provided below the ladle 1, and a horizontal molten steel discharge port 4 is provided at the bottom of the tundish 2. Molten steel 5 as a base material in the ladle 1 is injected into the tongue tissue 2 through a nozzle 3 provided at the bottom of the ladle 1, and the molten steel 5 in the tongue tissue 2 is passed through the horizontal molten steel outlet 4. It passes through and is discharged.

The laminating material @ band 6 wound into a coil shape is pulled out horizontally from a payoff reel 7 as a dispensing device by a drive roll 8, and is pulled out by a roller 17 to a molten steel discharge port 4 provided horizontally at the bottom of the tundish 2. It moves along the lower surface of the tandish 2.

A straightening roll 11 for correcting the shape of the laminate strip 6 along the movement path of the laminate strip 6 on the entry side of the tundish 2; and a heating furnace 12 for preheating the laminate strip 6. is provided.

The heating furnace 12 is provided immediately before the tundish 2, and in the illustrated example, is located on the upper surface side of the cladding band 6, where the molten steel 5 is supplied from the tundish 2. It is designed to preheat the surface. Laminating material tone band 6
At the bottom of the heating furnace 12 sandwiching the heating furnace 12, the heating furnace 12 is placed along the heating furnace 12 and close to the lower surface of the laminate strip 6 to prevent heat dissipation from the back surface of the preheated laminate strip 6. A heat insulating material 13 is provided for this purpose.

The heating furnace 12 may preheat the laminate @band 6 from both the front and back surfaces thereof. In this case, the heat insulating material 13 is not necessary. The inside of the heating furnace 12 is desirably kept in an inert gas atmosphere in order to prevent the laminate strip 6 from being oxidized.

The molten steel strip 6 is preheated by the heating furnace 12 along the moving path of the molten steel strip 6 from the outlet side of the heating furnace 12 to the vicinity of the molten steel discharge port 4 of the tundish 2, and brought close to the back side of the laminate strip 6. A heat insulating material 14 is provided to prevent heat dissipation from the back side of the laminate strip 6. Note that it is more effective if the heat insulating material 14 is formed into a heat insulating chamber that covers the entire surface of the laminate strip 6, and the inside thereof is filled with an inert gas atmosphere.

Along the moving path of the KH1 laminate strip 6 on the outlet side of the molten steel discharge port 4 of the tundish 2, on the surface thereof (to cool the laminate strip 6 to which the molten steel 5 as the base material has been supplied is cooled from its back surface). A plurality of upward spray nozzles 15 are provided to spray cooling water.

16 is disposed on the exit side of the molten steel discharge port 4 of the tundish 2 along the movement path of the cladding band 6 to which the molten steel 5 as a base metal is supplied onto the surface thereof, and on both sides thereof. A pair of refractory holding members made of an endless band.

Each of the pair of holding members 16 is shown in FIG. 2 as a schematic plan view, FIG. 3 as a partial plan view taken in the direction of arrow A in FIG. 1, and FIG. , as shown in FIG. 5 as a partial side view in the direction of arrow C in FIG. to move in the direction of the arrow.

The holding member 16 has an L-shaped cross section as shown in FIG. The molten steel 5 is held so that the molten steel 5 supplied above does not flow out. In this way, the holding member 16 allows the laminate material adjustment band 6 to
The molten steel 5 supplied above is prevented from flowing out, and the molten steel 5
Due to the static pressure, the laminate strip 6 is pressed onto the horizontal portion 16a of the holding member 16, so that the molten gA5 is pushed onto the holding member 1.
There is no leakage from the horizontal portion 16a of 6.

As shown in FIG. 4, a slight gap is provided between both ends of the laminate strip 6 and the inner surface of the vertical portion 16b of the holding member 16.
By flowing the molten steel 5 into this gap so that both sides and the upper surface of the cladding strip 6 are cast with the molten steel 5, a decrease in the yield of the cladding strip 60 can be prevented.

The surface of the laminate strip 6 which is pulled out from the payoff reel 7 by the drive roll 8 and moved horizontally is preheated to a predetermined temperature by the heating furnace 12, and then the conventional discharge port of the tundish 2 is formed on the surface. Molten steel 5 as a base material is supplied from 4. The molten steel 5 and the laminating material adjustment band 6 are the lamination material adjustment band 6.
has been preheated to a predetermined temperature by the heating furnace 12,
Completely welded.

In this way, the molten steel 5 is prevented from flowing out of the cladding band 6 on which the molten steel 5 is supplied by the holding members 16 that support both sides thereof, and the both sides of the copper band are kept warm. During this time, both sides of the copper strip are completely bathed with molten steel.

Next, the cladding band 6 is cooled by cooling water injected from a plurality of upward spray nozzles 15 arranged at predetermined intervals from the molten steel discharge port 4 of the tundish 2, and the molten steel is 5 solidifies to become a clad steel slab 10.

A drive roll 8 for moving the laminate strip 6 is provided at an appropriate position between the Biofreel 7 and the tundish 2 and at an appropriate position on the downstream side of the tundish 2. The finished laminated strip 6 is
The molten steel 5 is guided at a predetermined speed through the heating furnace 12 and below the molten steel outlet 4 of the tundish 2, and the molten steel 5 is supplied from the molten steel outlet 4 onto the surface of the cladding strip 6 to form welded clad steel sections 10. , move at a predetermined speed.

When manufacturing clad steel slabs using the above-mentioned apparatus, the thickness of the base metal should be controlled by the flow rate of the molten steel 5 discharged from the molten steel discharge port 4 of the tundish 2 or the moving speed of the cladding band 6. I can do it.

As described above, the cladding band 6, on which the molten steel 5 has been supplied, moves while being supported by the holding members 16 on both sides, and after a predetermined period of time has elapsed since the molten steel 5 was supplied, the cladding band 6 is Since the middle part of the back surface of the laminate strip 6 is forcibly cooled by the cooling water sprayed from the spray nozzle 15, there is a cooling difference in the width direction of the laminate strip 6, and under the condition that both sides are completely welded. Then, the solidification of the molten steel 5 progresses. Therefore, there is no unwelded portion on both sides of the cladding strip 6, and a high-quality clad steel slab in which the molten steel 5 is completely welded to the cladding strip 6 can be manufactured.

Note that the holding member 16 does not necessarily need to be moved in synchronization with the laminate band 6, and may be of a fixed type. Further, in order to prevent heat removal from the molten steel 5 by the holding member 16, it is effective to preheat the holding member 16.

The preheating temperature of the cladding band 6 immediately before the molten steel 5 as the base material is supplied is such that the narrow surface temperature on the side to which the molten steel is supplied ranges from 300°C to the solidus temperature of the cladding band. Preferably, the temperature range is less than 200°C.

That is, by preheating the cladding material strip immediately before the molten steel serving as the base material is supplied to a temperature within the above-mentioned range, when molten steel is supplied onto the surface of the cladding material conditioning strip,
The interface between the two can be quickly brought to a high temperature necessary for welding. Therefore, the molten steel 5 supplied onto the surface of the cladding band 6
is not cooled to produce a solidified shell, and
Clad copper slabs having a sound welded interface can be stably produced without causing deformation or buckling of the cladding strip 6 due to contact with the high-temperature molten steel 5.

In addition, in this invention, the molten steel 5 as the base material cools the laminate strip 6 onto which the molten steel 5 as the base material is supplied from the back surface of the laminate strip 6. After a predetermined time has elapsed from the time the material is supplied to the surface of the lamination material strip 6, which is determined by the thickness and temperature of the lamination material strip 6 and the pouring method of the molten steel 5 as the base material, the material preparation strip is It is necessary to start the process after 6 and the molten steel 5 as the base metal are completely welded together.

That is, by setting the cooling start timing for the cladding material strip 6 as described above, it is possible to reliably weld the laminate material conditioning strip 6 and the molten steel 5 as the base material.

If the cooling of the laminate strip 6 is started at the same time as or before the supply of the molten steel 5 as the base material, the preheating effect of the laminate strip 6 described above will be lost and the laminate strip 6 will be cooled. Due to the temperature drop in 6, the welding of the laminate material sputum band 6 and the molten steel 5 is significantly inhibited. In particular, when the thickness of the laminate strip 6 is thin,
Even if we take the pains to preheat the cladding strip 6, the temperature immediately drops to the front surface due to cooling from the back surface, making it difficult to weld it with the molten steel 5.

[Embodiments of the invention]

Next, the present invention will be further described in detail with reference to examples.

Using the equipment shown in Figures 1 to 5, stainless steel
Clad steel slabs were manufactured. A copper strip of 18-8 stainless steel (5US304) with a thickness of 5-1 and a width of 1000 mm was used as the laminating material, and molten steel of ordinary carbon steel (containing 0.10% C) was supplied as the base material. The stainless steel strip used as the cladding material was a hot-rolled coil, which was pickled before use. A stainless steel strip as a laminating material is preheated to approximately 900°C in a heating furnace with an argon + 3% hydrogen atmosphere, and molten steel is placed on its surface for approximately 40 minutes.
It was supplied so as to have a thickness of zero.

The temperature of the molten steel as the base material supplied onto the surface of the clad steel strip is approximately 1570° C. The moving speed (casting speed) of the laminate strip is 2 m/r11. The cross-sectional shape of the molten steel discharge port provided in the tundish was a flat slit shape, and the direction of the molten steel discharge flow was set at 25 degrees with respect to the direction of the laminating material.

The back side of the laminated steel strip to which molten steel was supplied as the base material was kept warm with a heat insulating material for 75c+++ from the molten steel supply position, and then the middle part in the width direction was air-cooled, and then water-cooled.

Both sides of the cladding steel strip were supported from before the molten steel supply position by L-shaped holding members that moved in synchronization with the molten steel strip until solidification of the molten steel was completed. The holding member was made of a refractory material with good heat retention, and was sufficiently preheated before use, and the back side was heated with a burner during casting. Between the inner wall of the holding member and both ends of the cladding steel strip, approximately 10
A gap of +++ m was provided, and the upper surface side and both sides of the cladding steel strip were cast with molten steel.

As a result, we were able to produce Clarard steel slabs with a sound weld interface.

The present invention is not limited to the case where a single-sided crat steel slab is produced by supplying a welded amount as a base material onto the surface of one cladding steel strip as described above, but is applicable to a pair of cladding steel strips. Of course, this method can also be applied to the case where molten steel is supplied as a base material between the two sides to produce a double-sided clad steel slab.

〔Effect of the invention〕

As explained above, according to the method of the present invention, it is possible to stably and economically produce high-quality clad steel slabs having a sound welded interface with no unwelded parts at the interface and a high yield. Q that can bring about superior industrial effects

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing one embodiment of an apparatus used in the method of the present invention, FIG. 2 is a schematic side view of a holding member, and FIG. 3 is a partial plan view taken in the direction of arrow A in FIG. , Figure 4 is the third
FIG. 5 is a sectional view taken along line B-B, and FIG. 5 is a partial side view taken along arrow C in FIG. In the drawing, 1... ladle 2...
・Tanditshu'' 3...Nozzle 4・
... Molten steel discharge port 5 ... Molten steel 6 ... Laminating material adjustment band 7 ... is Iofuriel 8, 9 ... 1 Drive roll 10 ... Clad steel slab 11 ... Straightening roll 12 ...・Heating furnace 13.14...Insulating material 15...Spray nozzle 16...Holding member 17
···roller

Claims (1)

[Claims] Molten steel as a base material is supplied onto the surface of one cladding steel strip or between a pair of cladding steel strips that move continuously, and the molten steel is transferred to the cladding steel. The clad steel slab is continuously welded to the strip, and then the surface of the clad steel strip opposite to the welded surface of the molten steel is forcedly cooled to solidify the molten steel welded to the clad steel strip. In the continuous casting method of clad steel slabs manufactured in
Both sides of the clad steel strip supplied with molten steel are held by L-shaped refractory holding members to prevent the molten steel from flowing out from the both sides and to keep the both sides warm. , on the other hand, a clad steel characterized in that the middle part of the surface opposite to the welding surface of the molten steel of the cladding steel strip to which the molten steel is supplied is forcibly cooled after a predetermined period of time has elapsed from the time when the molten steel was supplied. Continuous casting method for slabs.