JP2005095926A - Continuous casting and hot-rolling apparatus, and continuous casting and hot-rolling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method suitable to manufacture a hot-rolled steel sheet of fine grained steel by continuous casting and hot rolling. <P>SOLUTION: A hot-rolled steel sheet ( rolled sheet ) Ab is manufactured by rolling a cast slab Aa which is obtained with a continuous casting machine 1 with a finishing mill 5 having a plurality of stands without cooling the slab to ordinary temperature in continuous casting and hot-rolling equipment. Different-diameter roll mills are arranged for three stands F4-F6 of the later stage including the final stage as the finishing mill 5 and also curtain wall type cooling means 7 are similarly arranged on the respective outlet sides of the three stands F4-F6 of the later stage. Curtain wall type cooling means 4 or 6 are arranged somewhere between the outlet side of the continuous casting machine 1 and the inlet side of the fourth stand F4 of the finishing mill 5 ( after all, the inlet side of the final three stands ). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The claimed invention relates to a continuous casting hot rolling facility for finish rolling a slab obtained by continuous casting without cooling to room temperature, and a continuous casting heat for producing a hot rolled sheet or the like by performing finish rolling. It is related to the rolling method.

  The technology called continuous casting hot rolling, in which the slab obtained by continuous casting is hot-rolled at a high temperature with little cooling, greatly reduces the energy for heating the slab before rolling. Is possible. In particular, equipment called CSP (Compact Strip Production) for casting thin (thickness of 100mm or less) slabs with a small continuous casting machine (especially with a low overall height) is compact in height and length. It is extremely advantageous in terms of cost, and is attracting attention as it enables integrated production of continuous casting and hot rolling in small and medium-sized steelworks. Such continuous casting hot rolling is described in, for example, Patent Document 1 and Patent Document 2 below.

On the other hand, with regard to hot rolling, in recent years, finishing mills have been developed for industrially and commercially producing steel sheets (fine-grained steel hot-rolled steel sheets) having a fine structure mainly composed of fine-grained ferrite. As shown in Patent Document 3, the outline of the technology is such that large reduction (rolling with a high reduction ratio) or the like is performed in the latter stage of the finish rolling mill, and the temperature rise due to the processing heat accompanying such reduction is strong. It is to suppress by cooling.
JP 2002-172401 A JP-A-2-213414 JP 2002-273501 A

  When a finish rolling mill as described in Patent Document 3 is incorporated into the continuous casting hot rolling facility described in Patent Document 1 and the like and then followed by a continuous casting machine, the above-mentioned advantages of continuous casting hot rolling are utilized to make the fine rolling mill fine. It becomes possible to manufacture a grain steel hot-rolled steel sheet, and it is expected that there will be a considerable merit in terms of cost and product quality.

  However, conventionally, it has been impossible to manufacture a fine-grained steel hot-rolled steel sheet by a continuous casting hot-rolling method. The reason for this is that i) In a finishing mill for producing fine-grained steel, it is necessary to suppress the processing heat accompanying large pressure and to lower the finishing temperature (700-800 ° C.) than in normal rolling. Ii) In the case of continuous casting hot rolling, the temperature of the slab is not freely adjustable by the setting of the heating furnace, but is determined from the solidification temperature of the slab, etc. The temperature at is a value (1050-1150 ° C.) that is too high as compared with a temperature suitable for fine-grained steel rolling. In other words, the temperature of the slab was not suitable for finishing rolling for the production of fine-grained steel, and a method for properly eliminating such temperature mismatch without losing the compactness of the equipment could not be found. It can be said that there was a problem.

  Patent Document 2 describes that a thin slab continuous casting machine is followed by a finish rolling mill, and after the slab is cooled strongly, a relatively high reduction is performed by the finishing mill. However, the technique is characterized by rolling the steel sheet at a temperature in the ferritic region and does not obtain fine-grained steel, and the slab is rapidly and smoothly brought to such a temperature (for example, so as not to cause surface cracks). ) It cannot be a technical reference because there is no specific cooling means for cooling.

  The invention which concerns on a claim provides the suitable installation and method which manufacture a fine-grained steel hot-rolled steel plate by continuous casting hot rolling from the above viewpoints.

The continuous casting hot rolling facility according to claim 1 is a continuous casting hot rolling facility that manufactures a hot-rolled steel sheet by rolling a slab obtained by a continuous casting machine with a plurality of finishing mills without bringing it to room temperature. And
a) As the above finish rolling mill, different diameter roll mills or ultra-small diameter roll mills are arranged on two or more subsequent stages including the final stage, and the curtain wall type is provided on the exit side of the two or more subsequent stages including the final stage. Arrange cooling means,
b) Curtain wall type cooling means is placed at any location (one or more locations) from the exit side of the continuous casting machine to the entrance side of the final 3 stands of the finish rolling mill (the entrance side of the third stand from the back). It is characterized by that.

  The ultra-small diameter roll mill referred to above refers to a rolling mill in which both of the pair of work rolls are smaller in diameter than 600 mm, and the different diameter roll mill refers to a pair of upper and lower pairs of work rolls having different diameters. A work roll having an equivalent roll diameter (average roll diameter) of less than 600 mm in diameter. Curtain wall type cooling means is a cooling means with a high cooling capacity in which a large amount of cooling water is flown in a laminar flow state from above and below like a curtain and is applied to the upper and lower surfaces of the rolled material over the entire width. Say. As the continuous casting machine, for example, a machine for producing a thin cast slab (thin slab) having a thickness of 30 to 100 mm may be disposed.

  In this continuous casting hot rolling equipment, a finishing mill having the characteristics of a) above is used. Therefore, when a slab is supplied to the finishing mill at an appropriate temperature, it has a fine ferrite structure. Fine-grained steel hot-rolled steel sheets with a good balance of mechanical strength such as tensile strength and ductility can be produced smoothly. Because, i) In different diameter roll mills or ultra-small diameter roll mills arranged on two or more stands including the final stage, the work roll has a small diameter, so that large rolling can be performed with a low rolling load. This is because inconveniences such as roll flatness and edge drop are alleviated due to its small size, and ii) the curtain wall type cooling means provided on the exit side of the two or more subsequent stages including the final stage is powerful. This is because the cooling capacity suppresses the temperature rise (processing heat generation) of the rolled material due to the large reduction rolling at each stand and stops the grain growth of the microstructure of the rolled material immediately after rolling at each stand. . Moreover, the thin slab slab as obtained by continuous casting has a finer structure than that reheated in a heating furnace to perform normal rolling. In the case of rolling, it is possible to produce a fine-grained hot-rolled steel sheet having a fine ferrite structure and excellent strength.

  When finishing and rolling a slab obtained with a continuous casting machine at a high temperature, the temperature of the slab is often too high unlike reheating of a slab once brought to room temperature. If it is a casting hot rolling facility, the rolling temperature of the plate sent to the finishing mill is appropriately lowered to enable smooth production of the fine-grained steel hot-rolled steel plate. This is because the curtain wall type cooling means is arranged at any location from the exit side of the continuous casting machine to the entry side of the final three stands of the finish rolling mill as described in b) above. That is, by using the cooling means, the slab supplied at a high temperature can be adjusted to an appropriate temperature by the entry side of the final three stands of the finish rolling mill. With curtain wall type cooling means, by securing a sufficient amount of water and appropriately applying cooling water to the slab or rolled material, the plate can be properly fitted without losing the compactness of the equipment (short overall length, etc.). The rolling temperature can be reached. When producing a fine-grained steel hot-rolled steel sheet by large rolling, the closer the stand is to the final stage, the stronger the influence of rolling on the metal structure. Therefore, with the equipment of this claim, if the plate temperature is adjusted to the entrance side of the final 3 stands of the finish rolling mill and large reduction and strong cooling are performed at the multiple subsequent stages including the final stage, fine-grained steel Production of hot-rolled steel sheets is sufficiently possible. If the thickness of the slab is reduced to 30 to 100 mm as described above, it is possible to optimize the temperature of the plate by the curtain wall type cooling means provided at any one of the above locations up to the entrance side of the last three stands. Easy.

  In addition, the continuous casting hot rolling equipment of this claim and the other claims is provided when a tunnel-type heating furnace is provided on the outlet side (immediately after position) of the continuous casting machine, or when reverse rolling is performed before the finishing mill. When providing a mill, the case where a coil box is provided between a rough rolling mill and a finishing mill is not excluded. Also, when offsetting the line core of a finishing mill, etc. with respect to the line core of a continuous casting machine, etc., or arranging the line of a finishing mill, etc. between the two lines by arranging the continuous casting machine, etc. in two lines Can also be an embodiment of the invention.

  The continuous casting hot rolling facility according to claim 2 is a curtain wall, in particular, between the outlet side of the continuous casting machine and the first stand of the finishing mill, and on each outlet side of the plurality of stands of the finishing mill. A mold cooling means is arranged.

  If a plurality of curtain wall type cooling means are arranged in this way, the following merits are obtained. That is, i) Even when a thick slab is manufactured and sent to a finishing mill, or when the rolling speed is increased, the temperature of the plate can be sufficiently lowered, and the fine-grained steel is heated by continuous casting hot rolling. In addition to smooth production of rolled steel sheets, ii) normal rolling performed by setting the slab temperature in a heating furnace by sufficiently lowering the plate temperature at the entrance of the first stand of the finishing mill It is also possible to carry out finish rolling similar to that (and thus accustomed to operation).

  The continuous casting hot rolling facility according to claim 3 further includes a continuous casting machine for casting a thin cast slab (thin slab) having a thickness of 30 mm to 60 mm, and the exit side of the continuous casting machine and the finish described above. A curtain wall type cooling means and a tunnel type heating furnace are arranged in this order between the first stand of the rolling mill.

Such continuous casting hot rolling equipment has the following operational advantages. That is,
i) Since the cast slab is considerably thin with a thickness of 30 mm to 60 mm, the number of curtain wall type cooling means arranged from the continuous casting machine to the final three stands of the finish rolling mill should be reduced (for example, only one). This is advantageous in terms of equipment cost, simplicity and compactness of equipment. In addition, since the slab is also made thinner, a roughing mill is not required, and it can be smoothly worn only with a finish rolling mill up to a thin steel sheet having a thickness of about 1 to 2 mm (that is, the roll is significantly worn by an excessive load). It is possible to carry out rolling.
ii) The temperature of the slab to be sent to the finishing mill can be made uniform, so that it is possible to produce a fine-grained hot-rolled steel sheet having particularly excellent quality. When performing general rolling using a heating furnace, temperature unevenness tends to occur in the slab between the part supported by the support member during heating and the part that is not, whereas when performing continuous casting hot rolling It can be said that it is inherently easy to manufacture a high-quality hot-rolled steel sheet because the cast slab of uniform temperature as it is cast is rolled. However, in the equipment of this claim, a tunnel-type heating furnace is further disposed behind (downstream) the curtain wall type cooling means, so that the temperature of the slab after the temperature adjustment by the cooling means is made particularly uniform. Because it is possible. In other words, when the slab temperature is lowered by the cooling means, the temperature of the slab surface and the four corners (corner portions) may be too low. By lightly heating again, the temperature of the surface and the four corners can be raised and the temperature of the entire slab can be made uniform. In addition, since a tunnel-type heating furnace is used, temperature unevenness (skid mark or the like) of the slab due to only a specific portion in the slab contacting the support member does not occur.

The continuous casting hot rolling method according to claim 4 is a continuous casting hot rolling method for producing a hot-rolled steel sheet by rolling a slab obtained by a continuous casting machine with a multi-stand finish rolling mill without bringing it to room temperature. And
1) At the entrance of the final 3 stands of the finishing mill (the entrance of the 3rd stand from the back), the stand is placed from the exit side of the continuous casting machine so that the plate is 900 ° C. or less (preferably 750 to 850 ° C.). To cool the plate
2) While rolling so that the accumulated strain is 0.6 or more (preferably 0.9 or more) in the final three stands of the finishing mill, at least two or more final stands (two or more subsequent stages including the final stage) The plate is cooled on each outlet side, and the finishing temperature is set to 800 ° C. or lower (preferably 700 to 800 ° C.).

In the above, “strain” means the difference between the thickness h ₀ of the steel sheet at the entrance side of each stage stand and the thickness h ₁ at the exit side divided by the average thickness of both ε = (h ₀ −h ₁ ) / {(h ₀ + h ₁ ) / 2}
Say. “Cumulative strain” is a weighted integration of the strain at each stage of the last three stands (ignoring the stand on the upstream side because the impact is small) considering the strength of the influence on the metal structure. Then, when the distortion at the last stage and its preceding and preceding stages are ε _n , ε _n-1 , and ε _n-2 , respectively,
ε _c = ε _n + ε _n-1 / 2 + ε _n-2 / 4
Ε _c represented by
Also in this invention, it is good to manufacture a thin cast piece (thin slab) having a thickness of 30 to 100 mm, for example, in the continuous casting machine.

  According to this continuous casting hot rolling method, it is possible to smoothly manufacture a fine-grained steel hot-rolled steel plate having a good strength balance by continuous casting hot rolling having the above-described advantages. The plate obtained by continuous casting is sufficiently cooled to the final 3 stands of the finishing mill by the cooling of 1) above to optimize the temperature, and in the final 3 stands having a strong influence on the metal structure, the above 2 This is because large rolling reduction is performed while suppressing temperature rise due to processing heat by sufficient cooling. As described above, the temperature of the plate is set to 900 ° C. or lower on the entrance side of the final three stands, and the final temperature is set to 800 ° C. by performing sufficient cooling while performing large reduction rolling with a cumulative strain of 0.6 or more. If maintained below, it is possible to produce a fine-grained steel hot-rolled steel sheet having a fine ferrite structure with an average grain size of about 10 μm or less. If the cumulative strain at the final three stands is 0.9 or more under the same conditions, a fine-grained steel hot-rolled steel sheet with an average grain size of about 4 μm or less can be produced. Considering that the thin slab slab has a fine structure (described above), a fine-grained steel hot-rolled steel sheet with a finer particle size may be produced. In addition, in order to perform continuous casting hot rolling on the conditions as described here, it is good to use the installation described in Claim 1, for example.

  In particular, the continuous casting hot rolling method according to claim 5 is characterized by cooling the plate between the outlet side of the continuous casting machine and the first stand of the finish rolling mill, so that the plate on the inlet side of the first stand can be cooled. The temperature is 1000 ° C. or less (preferably 900 to 1000 ° C.).

  According to this continuous casting hot rolling method, it is possible to produce a fine-grained steel hot-rolled steel sheet as described above by performing normal rolling (that is, accustomed to the operation) without performing a special operation in the finish rolling mill. it can. If the plate is cooled to the appropriate temperature by the first stand of the finishing mill, the finishing mill process can be performed in the same manner as normal rolling performed by setting the slab temperature in a heating furnace. Because it is enough.

  In the continuous casting hot rolling method according to claim 6, in particular, a thin cast slab (thin slab) having a thickness of 30 mm to 60 mm is cast by a continuous casting machine, and the cast slab is cooled by a curtain wall type cooling means. Heating is performed by a mold heating furnace (the vicinity of the surface and the four corners are preferentially heated), and then rolling is performed by a finishing mill.

Such a continuous casting hot rolling method has the following merits. That is,
i) Casting a very thin slab with a thickness of 30 to 60 mm and cooling it by means of a curtain wall type cooling means having a high cooling capacity, it is easy to optimize the temperature of the plate as described above. is there. Since the slab is thinned, it is possible to smoothly manufacture a thin steel sheet having a thickness of about 1 to 2 mm only by finish rolling without performing rough rolling (that is, without excessively loading the roll due to excessive load). There are also advantages.
ii) The temperature of the slab to be sent to the finishing mill can be made uniform, so that it is possible to produce a fine-grained hot-rolled steel sheet having particularly excellent quality. This is because, as described above (Claim 3), the slab after the temperature adjustment by the curtain wall type cooling means can be heated to a uniform temperature as a whole by heating in the tunnel type heating furnace. .

  The continuous casting hot rolling method according to claim 7 is characterized in that, in particular, rolling in a finishing mill is performed in the austenite region of the steel sheet. That is, finish rolling is not performed at the temperature of the ferrite region shown in Patent Document 2, but is performed in the austenite region.

  When performing finish rolling in the ferrite region, the slab is cooled extremely strongly so that the finish rolling machine has a low temperature with a lower limit of 300 ° C. (see the above-mentioned Patent Document 2). Cooling means that realizes strong cooling at such a short distance and does not cause surface cracks in the plate, taking advantage of the features of continuous casting hot rolling that can be made compact, cannot be assumed at the current technical level. However, if finish rolling is performed in the austenite region according to the method of this claim, it is sufficient to lower the temperature of the plate after finish rolling to around 750 ° C. by cooling. If the plate is cooled in such a temperature range, it is possible to appropriately realize the above-described curtain wall type cooling means or the like so as not to cause cracking. Therefore, it can be said that the method of this claim is a practical method for smoothly realizing the production of a fine-grained steel hot-rolled steel sheet by continuous casting hot rolling using a practical cooling means that can be used.

  According to the continuous casting hot-rolling facility according to claim 1, the rolling temperature can be appropriately lowered for the plate that is cast by the continuous casting machine and then sent to the finishing rolling mill as it is, and smooth production of the fine-grained steel hot-rolled steel plate is possible. Is possible. In other words, the advantages of continuous casting hot rolling that enables integrated production of continuous casting and hot rolling with compact equipment, and fine-grained steel heat that produces a plate with fine ferrite grain size and excellent strength balance, etc. Both effects can be obtained.

  According to the continuous casting hot rolling facility according to claim 2, even when the production capacity is increased by thickening the slab or increasing the casting or rolling speed, the fine grain steel is obtained by continuous casting hot rolling. A hot-rolled steel sheet can be manufactured smoothly. The finishing mill can be easily operated.

  The continuous casting hot-rolling facility according to claim 3 further reduces the number of cooling means because the slab is thinned, and eliminates the need for a rough rolling mill. This is advantageous. Moreover, since the temperature of the slab sent to a finishing mill can be made uniform, it becomes possible to manufacture a fine-grained steel hot-rolled steel sheet with particularly excellent quality.

  According to the continuous casting hot rolling method according to the fourth aspect, it is possible to smoothly manufacture a fine-grained steel hot-rolled steel plate having an excellent balance of strength by continuous casting hot rolling that provides advantages on equipment.

  The continuous casting hot-rolling method according to claim 5 can produce a fine-grained steel hot-rolled steel sheet by carrying out finish rolling without performing a special operation associated with continuous casting hot-rolling. Ease of operation There is a merit in stability.

  If it is the continuous casting hot rolling method according to claim 6, it is easy to further optimize the temperature of the plate, and it is possible to smoothly produce a thin steel plate having a thickness of about 1 to 2 mm without rough rolling. Since the temperature of the slab can be made uniform, there is an advantage that a fine-grained hot-rolled steel sheet having excellent quality can be manufactured.

  In the continuous casting hot rolling method according to the seventh aspect, since finish rolling is performed in the austenite region, smooth continuous casting hot rolling can be realized by practical cooling means that can be used.

  In FIG. 1, the side view (conceptual drawing) of the continuous casting hot rolling equipment which is one form on implementation of invention is shown. The equipment shown in the figure includes a continuous casting machine 1 for a thin slab, followed by a cutting machine 2, a tunnel heating furnace (tunnel furnace) 3, a finishing mill 5, a water cooling device (runout table) 8, and a winder (coiler). 9 is arranged. In the continuous casting machine 1, a slab (slab) Aa having a thickness of around 40 mm (30 to 60 mm) is cast, and the slab Aa is made into an appropriate length by the cutting machine 2 and then heated to a uniform temperature in the tunnel furnace 3. The slab Aa is passed through the finishing mill 5 without being sent to a cooling bed or the like to produce a hot-rolled steel plate (hot strip, rolled plate) Ab having a thickness of 1 to 2 mm. Among the equipment in the facility, the tunnel furnace 3 is a light heating furnace of a type in which a plurality of slabs Aa are held and sequentially transferred in the longitudinal direction. If this type is used, a fixed portion on the slab Aa cannot be brought into contact with the water-cooled member or the like for a long time during transfer, so that no skid mark is generated on the slab Aa. The cutting machine 2 is of a shear type (shear), but may be of other types such as a torch type.

The finishing mill 5 is a tandem arrangement of quadruple stands F1 to F6 each provided with a backup roll on each back of a pair of work rolls as shown in FIG. The finish rolling mill 5 is configured as follows so that a fine-grained steel hot-rolled steel sheet having a fine ferrite grain size (10 μm or less) can be produced.
i) A so-called different-diameter roll mill is disposed in the subsequent three stands F4 to F6. That is, as shown in the figure, work rolls having different diameters are arranged up and down, and only one of the work rolls having a larger diameter at the lower part is rotated by a motor or the like (not shown). The small diameter roll at the top is rotatable and does not apply a driving force. The diameter of the upper work roll is about 480 mm, and the diameter of the lower work roll is about 600 mm. These three stand F4 to F6 roll mills with different diameters have a small equivalent roll diameter, and because only one work roll is driven, a shearing force acts on the rolled sheet Ab. Rolling with a high rate (for example, a reduction rate of 50%) can be performed. Moreover, since the rolling load is small, inconvenience due to roll flattening and edge drop does not occur. Rolling under high pressure is also possible so that the cumulative strain ε _c is 0.6 to 0.9 in a series of three stands F4 to F6. In addition, the upper and lower work rolls have the same diameter of about 700 mm on the three stands F1 to F3 in the front stage, and they apply driving force to both work rolls.

ii) A curtain wall type cooling means 7 is arranged on the exit side of each mill of the three stands F4 to F6 arranged in the subsequent stage. The cooling means 7 applies a large amount of room temperature cooling water in a laminar flow state to the full width surface of the rolled sheet Ab from above and below in a curtain shape (curtain wall shape, thickness is 10 mm or more and optimum thickness is 16 mm). As a result, the rolled sheet Ab is strongly cooled. The amount of the cooling water can be adjusted within a range of 100 to 500 m ³ / h per unit width (1 m) of the rolled sheet Ab, and the temperature drop of the rolled sheet Ab due to cooling becomes 20 ° C./sec or more. Normally, cooling water of 350 m ³ / h per unit width is used, but the temperature drop of the rolled sheet Ab in that case is 60 to 80 ° C./sec (stand) when the product of sheet thickness × speed is 1200 mm · mpm. It reaches about 40 ° C./sec including the temperature rise due to each processing heat generation in F4 to F6. If this cooling means 7 is used while carrying out high-pressure rolling at the above-mentioned subsequent stands F4 to F6, the temperature rise of the rolled sheet Ab due to processing heat generated under high pressure is suppressed, and the high-pressure rolling method or the controlled rolling method is used. While maintaining the rolled material P in a suitable temperature range, it is possible to suppress the occurrence of grain growth in the fine structure after rolling, thereby producing the fine-grained steel hot-rolled steel sheet as described above. In the run-out table 8 on the downstream side of the hot rolling mill A in FIG. 1, the rolled sheet Ab is cooled at a rate of 10 ° C./sec or more with cooling water to prevent grain growth.
FIG. 2 shows the result of investigating the ferrite grain size of the rolled sheet Ab (2 steel types) when various finishing temperatures (temperature at the outlet side of the final stand F6) are set while performing appropriate cooling as described above. Indicates. It can be seen that it is effective to reduce the finishing temperature to about 800 ° C. or less in reducing the ferrite grain size.

  Since the slab cast by the continuous casting machine 1 shown in FIG. 1 is approximately 1100 ° C. and is too high to produce a fine-grained hot-rolled steel sheet by a finish rolling mill, this equipment is finished as shown in the figure. Cooling means 4 and 6 are also arranged in the first half of the rolling mill 5 and the like. That is, the curtain wall type cooling means 4 is provided on the entrance side of the first stage stand F1 of the finishing mill 5, and the curtain wall type cooling means 6 is provided on the exit sides of the first to third stage stands F1 to F3. Arranged. The cooling means 4 intends to cool the slab Aa having a too high temperature after casting to an appropriate temperature by the first stage stand F1 of the finish rolling mill 5. The cooling means 6 intends to sufficiently cool the plate Ab that has entered the finish rolling mill 5 before performing high-pressure rolling for fine graining. Depending on the thickness of the slab Aa and the cooling capacity of the cooling means 4 and 6, some of the cooling means 6 may not be used.

In the continuous casting hot rolling facility configured as described above, it is preferable to perform continuous casting and finish rolling as follows, for example. That is,
1) In the continuous casting machine 1, a thin slab Aa having a thickness of about 40 mm and a width of about 1000 mm is cast. The slab Aa is cut every about 50 m by the cutting machine 12, and the temperature is made uniform by the tunnel furnace 3. The temperature of the slab Aa at the exit of the tunnel furnace 3 is about 1100 ° C.
2) The slab Aa is cooled by the curtain wall type cooling means 4 so that the temperature of the slab Aa is about 950 ° C. on the entrance side of the first stage stand F1 of the finishing mill 5.
3) In the finishing mill 5, first, the cooling means 6 is used on the exit side (any one) of the first to third stage stands F1 to F3, and the fourth stand F4 (3 counted from the last stage). The rolled plate Ab is cooled to about 850 ° C. on the entrance side of the second stand).
4) The 3 stands F4 to F6 at the subsequent stage of the finish rolling mill 5 are subjected to high pressure and strong cooling for finer graining. That is, the three stands F4 to F6 are subjected to high pressure with a cumulative strain of about 0.9, the final thickness of the rolled sheet Ab is set to 2.0 mm, and strong cooling is performed using the curtain wall type cooling means 7. The finish temperature is set to about 750 ° C. by vigorous cooling, despite the significant heat generation of the rolled sheet Ab due to the high pressure.
5) The rolled sheet Ab exiting the rolling mill 5 is cooled by the run-out table 8 and then taken up by the coiler 9.

  In addition, regarding the cooling performed to the entrance side of the first stage stand F1 in order to lower the temperature of the slab Aa, for example, a) Curtain wall type cooling on the entrance side of the finishing mill 5 is different from the example of FIG. It is possible to move the means 4 to the entrance side of the tunnel furnace 3 or b) to arrange a cooling means other than the entrance side cooling means of the finish rolling mill 5 also on the entrance side of the tunnel furnace 3. .

It is a side view which shows notionally the continuous casting hot rolling equipment which is one form regarding implementation of invention. 2 is a survey result showing the relationship between the ferrite grain size of the rolled sheet and the finishing temperature in the finishing mill in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous casting machine 3 Tunnel furnace 4.6.7. Curtain wall type cooling means 5. Finishing mill Aa Slab Ab Rolled sheet (hot rolled sheet steel)

Claims (7)

A continuous casting hot rolling facility for producing a hot-rolled steel sheet by rolling a slab obtained by a continuous casting machine with a plurality of finish rolling mills without bringing it to room temperature,
As the above finish rolling mill, different diameter roll mills or ultra-small diameter roll mills are arranged on two or more subsequent stages including the final stage, and curtain wall type cooling is provided on the exit side of the two or more subsequent stages including the final stage. Means are arranged,
A continuous casting hot rolling facility characterized in that a curtain wall type cooling means is arranged at any point from the exit side of the continuous casting machine to the entry side of the final three stands of the finishing mill.   The curtain wall type cooling means is respectively arranged between the exit side of the continuous casting machine and the first stand of the finish rolling mill and on each exit side of the plurality of stands of the finish rolling mill. The continuous casting hot rolling facility according to 1.   A continuous casting machine casts a thin cast slab having a thickness of 30 mm to 60 mm. Between the outlet side of the continuous casting machine and the first stand of the finishing mill, a curtain wall type cooling means and a tunnel type heating are used. The continuous casting hot rolling equipment according to claim 1 or 2, wherein a furnace is arranged in this order. A continuous casting hot rolling method for producing a hot-rolled steel sheet by rolling a slab obtained by a continuous casting machine with a plurality of finish rolling mills without bringing it to room temperature,
The plate is cooled from the exit side of the continuous casting machine to the stand so that the plate becomes 900 ° C. or lower at the entry side of the final 3 stands of the finish rolling mill,
While rolling so that the cumulative strain becomes 0.6 or more in the final 3 stands of the finishing mill, the plate is cooled at each outlet side of at least 2 final stands and the finishing temperature is set to 800 ° C. or less. Continuous casting hot rolling method.   The temperature of the plate on the entry side of the first stand is set to 1000 ° C or lower by cooling the plate between the exit side of the continuous casting machine and the first stand of the finishing mill. 4. The continuous casting hot rolling method according to 4.   Casting a thin slab of 30 to 60 mm in thickness with a continuous casting machine, cooling the slab with a curtain wall type cooling means, heating it with a tunnel type heating furnace, and then rolling it with a finishing mill The continuous casting hot-rolling method according to claim 4 or 5, characterized in that: The continuous casting hot rolling method according to any one of claims 4 to 6, wherein rolling in a finishing mill is performed in an austenite region of the steel sheet.

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