JPS6149748A - Continuous casting method of clad steel billet - Google Patents

Abstract

PURPOSE:To weld the entire surface of clad steels to uniform quality and to improve the yield of products in continuous casting of the clad steel in which a molten steel is supplied, welded and quickly cooled onto the top surface of steel strips or between a pair of the steel strips by preheating both side ends of the steel strips to a relatively high specific temp. then supplying the steel strips. CONSTITUTION:The clad steels 10, 10 are produced by supplying the molten steel 5 onto the surface of the cladding steel strips 6 or a pair of the steel strips 6, 6' moving continuously, welding the molten metal thereto and cooling quickly 15 the molten steel from the outside surface of the strips 6, 6'. The surfaces of the strips 6, 6' are preheated in heating furnaces 12, 12' within the temp. range of >=300 deg.C and lower by 200 deg.C than the solidus line temp. of the steel strips. The two side ends of the strips 6, 6' are further heated to the temp. slightly higher relatively than the central part. The welding is satisfactorily executed and the early cooling at both ends is prevented. The entire surface is thus cooled to the side ends with good quality and the product yield is improved.

Description

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

[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 the cladding material and welding the 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.

Does the explosive bonding method combine base material, laminate material, and gunpowder? This method consists of bonding using shock waves caused by an explosion. Although this method has the advantage of being applicable to a wide range of metals, it has a limited 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 time and 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 the composite material in a mold, injecting molten steel as the base material into the mold, and casting the composite material into the mold.The composite steel ingot is then pressed and crimped. This method consists of causing However, this method requires a cladding material with a thickness exceeding a certain size, which limits the cladding ratio and requires measures against inclusions, oxidation of the surface of the laminate material, etc. There is a problem. In particular, the biggest problem is that the yield decreases significantly due to melting loss of the laminate and changes in the cladding ratio due to Merrell 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 carried out to produce steel slabs by continuous casting.
No. 1 and JP-A-58-65549 disclose a method for producing clad steel slabs by casting while supplying molten steel as a base material to the surface of one cladding material or between a pair of cladding materials. A method is disclosed.

FIG. 6 is a schematic explanatory diagram of the conventional method described above. Molten steel 5 as a base material in the ladle 1 is injected into a tundish 2 provided below the ladle 1 through a nozzle 3 provided at the bottom of the ladle 1.

A horizontal molten steel discharge port 4 is provided at the bottom of the tray/dish 2, and the molten steel 5 serving as the base material in the tray/dish 2 is provided.
is discharged through the horizontal molten steel discharge port 4.

On the other hand, the laminated steel strip 6 is pulled out horizontally by a drive roll 8 from a payoff reel 7 serving as a payout device.
The molten steel is guided below a molten steel discharge port 4 provided horizontally at the bottom of the tundish 2, and moves horizontally along the lower surface of the tundish 2. Reference numeral 9 denotes a cooling device installed along the movement path of the clad steel strip 6 starting from the lower position of the molten steel discharge port 4. The molten steel 5 is supplied onto the surface of the horizontally moving cladding steel strip 6 and is welded to the cladding steel strip 6. The molten steel 5 is cooled from the back side of the cladding steel strip 6 by the cooling device 9, and becomes the cladding steel strip. It solidifies on the surface of the strip 6, thus continuously producing a clad steel slab 10.

However, the above method has the following problems.

(1) In order for the laminate steel strip 6 and the molten steel 5 as the base material to be completely welded together, the contact interface between the two must be in a certain high temperature state. However, the laminated steel strip 6
Even if the molten steel 5 is supplied, it takes time for the interface temperature to reach the temperature required for welding, and the molten steel 5 tends to form solidification nozzles due to contact with the low-temperature cladding steel strip 6. , an unwelded portion is created between the clad steel strip 6 and the molten steel 5.

(2) The laminated steel strip 6 is provided with the molten steel 5 as the base material □
Rapid temperature change that occurs during feeding, i.e. 700 to 1
Due to the sudden temperature rise to 000℃, the molten steel 5 is deformed (reverse or bent) near the supply position.
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Since the widthwise end portions are easily cooled, unwelded portions are likely to occur between the cladding material steel strip 6 and @steel 5 at the widthwise end portions. Such unwelded portions cannot obtain sufficient adhesion even by subsequent hot rolling due to oxidation of the unwelded interface.

Furthermore, if the widthwise ends of the clad steel slab are unbonded and open, oxidation will progress to the unbonded interface at the widthwise center of the slab, resulting in poor bonding even after the subsequent hot rolling stage. Adhesion between the steel strip 6 and the molten steel 5 is extremely difficult, and therefore a clad steel material of excellent quality cannot be obtained.

(4) The interface weldability, soundness of quality, and manufacturing stability of the clad steel slab are determined by using the molten steel 5 as a base material supplied from the tandem unit 2 onto the surface of the clad steel strip 6, and the clad steel slab. It depends on when to start cooling from the back side of the band 6. That is, if the cooling start time is too late, not only will the molten steel 5 serving as the base material not solidify, but the cladding steel strip 6 will be damaged by the heat of the molten steel 5, and in some cases may be fused. On the other hand, if the cooling start time is too early, the molten steel 5 will be rapidly cooled through the laminating steel strip 6 and a solidified shell will be generated.
Weldability deteriorates significantly. Furthermore, there may be cases where the low-temperature laminating steel strip 6 is deformed due to the influence of a rapid temperature change due to contact with the molten steel 5.

[Object of the Invention] Therefore, the object of the present invention is to manufacture clad steel slabs by continuous casting, and to produce high-quality clad steel slabs with a sound welded interface in a stable manner with a high yield. The objective is to provide a continuous manufacturing method.

[Summary of the invention]

The method of the present invention is to supply molten steel as a base material onto the surface of one cladding steel strip or between a pair of cladding steel strips, and to transfer the molten steel to the cladding steel strip. The Schiffland steel slab is continuously welded to the strip, and then the surface of the cladding steel strip opposite to the welded surface of the molten steel is forcedly cooled to solidify the molten steel welded to the cladding steel strip. In a continuous casting method for producing clad steel slabs, before the molten steel as the base material is supplied, the clad steel strip is
The surface temperature of the side to which the molten steel is supplied is from 300°C,
The solidus temperature of the laminated steel strip is within a range of 200°C lower, and the temperature at both sides of the laminated steel strip in the width direction is also relatively lower than the temperature at the center. After preheating to a high temperature and then supplying the molten steel as the base material,
The present invention is characterized in that forced cooling of the clad steel strip is started after a predetermined period of time has elapsed since the molten steel was supplied.

[Structure of the invention]

In this invention, the surface temperature of the laminate steel strip immediately before the molten steel is supplied as the base material is increased from 300°C to the solidus temperature of the laminate steel strip on the side to which the molten steel is supplied. It is also necessary to preheat to a temperature that is 200°C lower.

That is, by preheating the clad steel strip just before the molten steel is supplied to the base material to a temperature within the above-mentioned range, when the molten steel is supplied onto the surface of the clad steel strip, both can quickly bring the interface to the high temperature necessary for welding. Therefore, the molten steel supplied onto the surface of the cladding steel strip will not be cooled and a solidified shell will be generated, and the cladding steel strip will not be deformed or buckled due to contact with high-temperature molten steel. , it is possible to stably produce clad steel slabs with a sound welded interface.

If the temperature of the preheated laminated steel strip is less than 300'C, the desired effect cannot be obtained from the above action. On the other hand, if the temperature of the preheated laminate steel strip exceeds a temperature that is 200°C lower than its solidus temperature, the tensile strength of the laminate steel strip will decrease significantly, resulting in The temperature of the deformed or broken steel strip and the molten steel supplied to the surface of the cladding steel strip rises too much, causing the problem that the cladding steel strip melts or breaks.

In this invention, the preheating temperature of the laminated steel strip is determined so that the temperature on both sides of the laminated steel strip in the width direction is relatively higher than the temperature at the center part within the above temperature range. The following is p.

In other words, if the above preheating temperature is uniform in the width direction of the laminated steel strip, the heat removed by air cooling is greater on both sides in the width direction than in the center, so when molten steel as the base material is supplied. Because the solidified shell develops quickly and the interface temperature of the cladding copper strip does not easily rise to the temperature required for welding,
Welding on both sides of the cladding material copper strip in the width direction becomes insufficient.
・Thus, by making the preheating temperature on both sides of the cladding copper strip relatively higher than the temperature in the center, the formation and growth of the solidified shell described above will be suppressed, and the interface of the cladding copper strip will be welded. It makes it easy to rise to the required @ degree,
The mating material copper strip and the molten steel as the base material are reliably welded without any unwelded parts.

Even if an unwelded part occurs in the widthwise center of the cladding material copper strip due to variations in casting conditions, both sides are completely welded, so oxidation at the interface of the unwelded part can be avoided. It is possible to prevent this, and it is possible to bond it by a subsequent rolling process.

As a means for making the preheating temperature of both sides of the cladding material copper strip relatively higher than the temperature of the central portion, for example, the cladding material copper strip is heated in a heating furnace for preheating the cladding material copper strip. The temperature at the positions corresponding to both sides in the width direction is increased by adding heating coils, heating elements, etc., or by increasing the gas flow rate of the burner in a heating furnace using a gas burner9. The area where the temperature of the areas corresponding to both sides of the cladding material copper strip in the width direction is made higher than the temperature of the area corresponding to the central part by dividing the cladding material copper strip in the widthwise direction is increased, or the preheated cladding material copper strip is engaged. This can be done by, for example, strictly performing the process, especially on both sides.

Note that if the preheating temperature on both sides of the cladding material copper strip is too high than the temperature in the center, the cladding material copper strip may be deformed, and both sides may be damaged when molten steel as the base material is supplied. If the temperature is too high, melting may occur. Therefore, it is necessary to select an appropriate preheating temperature for both sides of the cladding material copper strip depending on the material, plate thickness, shape, method of supplying molten steel, etc.

Generally, the difference in preheating temperature between both sides of the copper strip and the center is approximately 100 to 400°C.

In this invention, the cladding material copper strip to which the molten steel as the base material is supplied is cooled from the back side of the cladding material copper strip onto the surface of which the molten steel serving as the base material is supplied. After a predetermined period of time determined by the plate thickness and temperature of the mating material copper strip and the pouring method of the molten steel as the base material after being supplied, the mating material copper strip and the molten steel as the base material are combined. It is necessary to start after welding is complete.

That is, by setting the cooling start timing for the cladding copper strip as described above, the cladding copper strip and the molten steel serving as the base metal can be reliably welded together.

If the cooling of the cladding material copper strip is started at the same time as or before the supply of molten steel as the base material, the above-mentioned preheating effect of the cladding material copper strip will be lost, and the temperature of the cladding material copper strip will drop. , the welding of the laminated steel strip and the base metal is significantly inhibited. In particular, when the plate thickness of the cladding material copper strip is thin, even if the cladding material copper strip is preheated, the temperature immediately drops to the surface due to cooling from the back side, making it difficult to weld it to the base material. .

FIG. 1 shows an apparatus for preparing a single-sided clad steel slab by supplying molten steel as a base material onto the surface of one cladding material copper 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. The molten steel 5 as the base material in the ladle 1 is 1. - The molten steel 5 in the tundish 2 is injected into the tundish 2 through the nozzle 3 provided at the bottom of the tundish A1, and is discharged through the horizontal molten steel outlet 4.

The laminated steel strip 6 wound into a film is moved to a driving roll 8.
is pulled out horizontally from the payoff reel 7 as a payout device, and the tundish 2 is pulled out by the row 217.
The molten steel discharge port 4 is provided horizontally at the bottom of the tundish 2 and moves along the lower surface of the tundish 2.

A straightening roll 11 for correcting the shape of the cladding steel strip 6 along the movement path of the cladding steel strip 6 on the entry side of the tundish 2, and a heating furnace 12 for preheating the cladding copper 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 steel strip 6, and is located on the upper surface side of the cladding steel strip 6 to which the molten steel 5 is supplied from the tundish 2. It is designed to preheat the surface. Laminating steel strip 6
At the bottom of the heating furnace 12 sandwiching the heating furnace 12, a steel strip is placed along the heating furnace 12 and close to the lower surface of the laminated steel strip 6 to prevent heat dissipation from the back surface of the laminated steel strip 6 that has been preheated by the heating furnace 12. A heat insulating material 13 made of solid refractory material is provided.

The heating furnace 12 may preheat the laminated steel strip 6 from both the front and back sides 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 cladding steel strip 6 from oxidizing.

The steel strip 6 is preheated by the heating furnace 12 along the moving path of the 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 steel strip 6. A heat insulating material 14 made of a refractory material is provided to prevent heat dissipation from the back side of the joining material steel strip 6. In addition, the insulation material 14
It is more effective to form a heat insulating chamber that covers the entire surface of the laminated steel strip 6, and to create an inert gas atmosphere inside the chamber.

On the outlet side of the molten steel discharge port 4 of the tundish 2, the cladding steel strip 6, on which the molten steel 5 as a base material has been supplied on the surface along the movement path of the cladding steel strip 6, is cooled from the back side thereof. A cooling zone 15 is provided which is composed of a plurality of upward spray nozzles 15a that spray cooling water.

16 is disposed on both sides of the exit side of the molten steel discharge port 4 of the tanding 7yu 2 along the movement path of the laminating material steel strip 6 to which the molten steel 5 as a base material is supplied onto the surface thereof. Fixed or movable side grooves consisting of an endless band.

It is pulled out from the sipeio 7 reel 7 by the drive roll 8,
The steel strip 6, which is horizontally moved by the row 217, has its surface brought to the above-mentioned predetermined temperature in the heating furnace 12, and
It is preheated so that the temperature at both sides in the width direction is higher than the temperature at the center in the width direction, and then molten steel 5 as a base material is supplied onto the surface from the molten steel discharge port 4 of the tundish 2. The molten steel 5 and the cladding steel strip 6 are preheated in the heating furnace 12 so that the cladding steel strip 6 reaches the predetermined temperature mentioned above and the temperature at both sides in the width direction is higher than the temperature at the center in the width direction. It is completely welded.

In this way, the molten steel 5 and the welded clad steel strip 6 supplied onto the surface of the molten steel 5 are moved supported by the side blocks 16 until solidification at least on the short side ends, and the molten steel strip 6 is moved from the molten steel discharge port 4. Cooling zones 1 arranged at predetermined intervals
The molten steel 5 is cooled by cooling water injected from a plurality of upwardly directed spray nozzles 15a, solidifies, and becomes a clad steel slab 10.

A drive roll 8 for moving the laminating steel strip 6 is provided at an appropriate position between the payoff reel 7 and the tundish 2 and at an appropriate position downstream of the tundish 2, and is pulled out from the payoff reel 7. Laminating steel strip 6,
The molten steel 5 is guided through the heating furnace 12 at a predetermined speed to the lower part of the molten steel outlet 4 of the tanding 7 yu 2, and the molten steel 5 is supplied from the molten steel outlet 4 onto the surface of the cladding steel strip 6 to form a welded clad steel cast. The piece 10 is moved 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 clad steel strip 6. I can do it.

FIG. 2 shows, as another embodiment of the apparatus used in the method of the present invention, an apparatus for producing a double-sided clad steel slab by supplying molten steel as a base material between a pair of clad steel strips. It is a schematic explanatory diagram.

The first laminate steel strip 6, which is pulled out from the payoff reel 7 by the drive roll 8 and moved horizontally, is heated in the heating furnace 12 so that its surface reaches the predetermined temperature mentioned above, and the temperature on both sides in the width direction reaches the temperature in the width direction. The central part is preheated so that the temperature is higher than that of the central part, and then molten steel 5 as a base material is supplied from the molten steel discharge port 4 of the tundish 2 onto the surface of the molten steel, and the molten steel discharge port 4
As in the apparatus shown in FIG. 1, cooling is performed by cooling water injected from a plurality of upward spray nozzles 15a in a cooling zone 15 arranged at predetermined intervals.

In this embodiment, the second cladding material steel strip 6' is placed on top of the molten steel 5 serving as the base material, which is supplied from the molten steel discharge port 4 of the tundish 2 onto the surface of the first cladding material steel strip 6. The molten steel 5 as a base material is interposed between a pair of cladding steel strips consisting of a first cladding steel strip 6 and a second cladding steel strip 6', thus forming a double-sided clad steel slab. 10' is manufactured.

The second steel strip 6' is pulled out from the steel strip 7' by a driving roll 8', and after its shape is corrected by a straightening roll 11', the surface in contact with the molten steel 5 is heated by a heating furnace 12'. It is preheated to the above-mentioned predetermined temperature and so that the temperature on both sides in the width direction is higher than the temperature in the center part in the width direction. Heat insulating materials 13' and 14' are provided below the heating furnace 12' and along the passage of the second cladding steel strip 6' from the heating furnace 12' to the molten steel discharge port 4 of the tundish 2.

The cooling zone 15 provided on the outlet side of the molten steel discharge port 4 of the tundish 2 includes a plurality of upward spray nozzles 15a for cooling the back surface of the first cladding material steel strip 6, and a plurality of upper spray nozzles 15a for cooling the back surface of the first clad steel strip 6, and A plurality of downward spray nozzles 15bd for cooling the back surface of the second cladding material steel strip 6' are provided at positions facing the "/"Xk 15a.

According to this embodiment, the molten steel of the tundish 2 is placed between the first cladding steel strip 6 and the second cladding steel strip 6' whose surfaces have been preheated to a predetermined temperature by the heating furnace 12.12'. Molten steel 5 as a base material is supplied from the discharge port 4, and then
The molten steel 5 is cooled by cooling water injected from a plurality of upward spray nozzles 15a and a plurality of downward spray nozzles 15b in a cooling zone 15 arranged at a predetermined interval from the molten steel discharge port 4. It solidifies and becomes a double-sided clad steel slab 10'.

FIG. 3 shows still another embodiment of the apparatus used in the method of the present invention, in which a vertical continuous casting apparatus is used to supply molten steel as a base material between a pair of cladding material steel strips, and to form a double-sided caster. FIG. 1 is a schematic explanatory diagram showing an apparatus for manufacturing clad steel slabs.

In this embodiment, molten steel 5 as a base material is vertically discharged through a nozzle 3 provided vertically downward into a molten steel discharge port 4 provided on the bottom wall of a tundish 2, and is discharged vertically to a payoff reel 7. The double-sided clad steel slab 10' is produced by being supplied between the first cladding steel strip 6 and the second cladding steel strip 6' which are drawn out from 7' and moved vertically. This embodiment is the same as the embodiment shown in FIG. 2, except that molten steel 5 as a base material is vertically supplied between vertically moving cladding steel strips 6 and 6'.

In addition, in the case of this embodiment, by continuously supplying a pair of cladding steel strips to the short sides as well as to the long sides and welding them with the molten steel as the base metal, It is also possible to produce clad steel slabs whose faces are entirely covered with laminated steel strips. In this case, support by a side glock is not necessarily necessary.

[Embodiments of the invention]

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

A stainless clad steel slab was manufactured using the apparatus shown in FIG. Thickness 5 mm, width 1000 FIB, 1
A steel strip of 8-8 stainless steel (SUS304) 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 cladding material was preheated in a heating furnace in an argon + 3 chloride hydrogen atmosphere, and molten steel was supplied onto its surface to a thickness of about 40 mm. At this time, the stainless steel strip was preheated to 850°C on both sides in the width direction, as shown in Figure 4.
700℃ in the center and 700℃ in the entire width direction.
The experiment was conducted at two different temperatures, including 00°C.

By measuring the weight of the ladle and the dish 2, the change in the remaining amount of molten steel in the ladle and the dish 7 is calculated, and the ladle and dish 2 are measured so that the amount of change, that is, the amount of molten steel discharged, is kept constant. The thickness of the base metal was controlled by adjusting the discharge flow rate of molten steel from the tundish.

The laminate steel strip was cooled from the back side by an upward spray nozzle provided at a position 8QC1n away from the molten steel supply position, and the molten steel was solidified.

The temperature of the molten steel as the base material supplied onto the surface of the cladding steel strip is 1570 to 1580°C, the moving speed (casting speed) of the cladding steel strip is 2 m/-, and the angle of the molten steel outlet provided in the tundish. was set at 25 for the laminated steel strip.

The state of welding at the interface of the clad steel slabs produced in this way was investigated using ultrasonic flaw detection, cross-sectional microscopy, etc. ◇Figure 5 shows the relationship between the distance from the center of the width of the clad steel strip and the interface welding rate. It is a graph showing a relationship.

As is clear from Fig. 5, when the entire widthwise direction of the cladding steel strip is preheated to 700°C, the interface welding rate on both sides decreases; year,
When the temperature at the center was 700° C., the interfacial welding rate in the entire width direction could be 100%.

The clad steel slab of the above-mentioned embodiment is made of 18-8 stainless steel and ordinary carbon steel, but according to the method of the present invention, in addition to the above combination, it can be made of various stainless clad steels or mild steels. Various clad steel slabs can be easily produced in combination with high carbon steel.

〔Effect of the invention〕

As explained above, according to the method of the present invention, it is possible to stably and economically manufacture high-quality clad steel slabs with a healthy welded interface with no unwelded parts at a high yield. Excellent effects are brought about.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the apparatus used in the method of the present invention, FIG. 2 is an explanatory diagram showing another embodiment, and FIG. 3 is a schematic diagram showing still another embodiment. Explanatory drawings, Figure 4 is a graph showing the preheating temperature in the width direction of the laminated steel strip, Figure 5 is a graph showing the relationship between the distance from the center of the width of the laminated steel strip and the interface welding rate, and Figure 6 is FIG. 2 is an explanatory diagram showing an example of a conventional device. In the drawings, 1... Ladle, 2... Tundish, 3... Nozzle, 4... Molten steel outlet, 5... Molten steel, 6.6'...
- Laminated steel strip, 7.7'...Payoff reel, 8,
8'... Drive roll, 9... Cooling device, 10,
l O'...Clad steel slab, 11, 11'...
Straightening roll, 12, 12'... heating furnace, 13.13
', 14.14'...insulation material, 15, 15'...
Cooling zone, 15a, 15b... Spray nozzle, 16.
...Side Glock, 17...Lola.

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
is within a temperature range 200°C lower than the solidus temperature of the laminated steel strip, and the temperature at both sides of the laminated steel strip in the width direction is relatively higher than the temperature at the center. The clad steel is preheated to a high temperature, and then, after supplying the molten steel as the base material, forced cooling of the clad steel strip is started after a predetermined time has elapsed from the time of supply of the molten steel. Continuous casting method for slabs.