JP4935460B2 - Manufacturing method and manufacturing equipment for hot rolled steel sheet - Google Patents

Description

  The present invention relates to a production method and production equipment for producing a hot-rolled steel sheet having good surface properties.

  Hot-rolled steel sheets are used as they are after pickling, or cold-rolled and heat-treated, and further subjected to surface treatment. In any case, good surface properties are required. On the other hand, in the hot rolling process, since the steel material is processed and heat-treated in the atmosphere at a high temperature, an Fe oxide called scale is generated on the steel material surface during the process. When this scale is generated, an element such as Ni that is noble with respect to Fe is unevenly concentrated under the scale, resulting in a patterned surface defect. In particular, in recent years, in order to prevent global warming, there is an increasing expectation for iron making using scrap that can suppress carbon dioxide emissions as an iron source. However, since the contamination of impurities such as Ni from the scrap increases, Countermeasures for surface defects are becoming increasingly important.

  A general production line for producing hot-rolled steel sheets includes a heating furnace, a rough rolling mill row, and a finishing rolling mill row from the upstream side of the line. Usually, descaling (scale removal) by high-pressure water injection is performed on the entry side of the rolling mill (or the entry side of each pass of reverse rolling) and the entry side of the finish rolling mill row. The reason why descaling is performed on the entry side of the roughing mill and the entry side of the finish rolling mill row is to prevent the scale from being caught in the rolling roll as much as possible. However, with such a series of conventional descaling, it is difficult to suppress the occurrence of surface defects due to the concentration of Ni or the like as described above.

Conventionally, several methods for preventing the occurrence of surface defects due to concentration of Ni or the like have been proposed.
For example, Patent Document 1 discloses a method for controlling the Ni concentration of the steel sheet surface layer, its concentration distribution, and further the slab heating conditions.
In Patent Document 2, the interface property between the steel material and the scale is quantified, and this is controlled to a predetermined value by adjusting the heating conditions. More preferably, after heating, the surface of the slab before hot rolling is 0.9. A method of descaling with high pressure water of ~ 4.0 MPa is shown.
Patent Document 3 discloses a method in which a hot-rolled steel sheet is pickled by a conventional method and further subjected to final pickling under specific conditions.
Further, Patent Document 4 is not intended to prevent the occurrence of surface defects due to the concentration of Ni or the like, but is a scale generated on the surface of the slab by heating in a heating furnace, and particularly removed. Aiming at removing a wedge-shaped scale (a scale that partially bites into the steel), a method of descaling the heated slab, then oxidizing it, and further descaling is shown. ing.

JP 2002-309343 A JP-A-9-52110 JP 2005-281775 A Japanese Patent Laid-Open No. 10-244312

However, the above-described prior art has the following problems.
In other words, the methods of Patent Documents 1 and 2 are significant constraints on the process, and are difficult to implement industrially stably. Further, the effect of suppressing the generation of surface defects due to the concentration of Ni or the like is not sufficient.
The method of Patent Document 3 has a problem that the processing efficiency is very low and thus the productivity is lowered and the product yield is also lowered.
Furthermore, since the method of Patent Document 4 aims to remove the wedge-shaped scale on the surface of the slab, a sufficient suppression effect cannot be obtained with respect to generation of surface defects due to concentration of Ni or the like.
As described above, the prior art has a problem that it is difficult to effectively suppress the occurrence of surface defects due to the concentration of Ni or the like, or it is difficult to implement industrially.

  Therefore, the object of the present invention is to solve such problems of the prior art, suppress the occurrence of surface defects due to the concentration of Ni and the like in the manufacturing process, and efficiently produce a hot-rolled steel sheet with good surface properties. An object of the present invention is to provide a production method and production equipment that can be produced and that are industrially easy to implement.

In order to suppress the occurrence of surface defects due to the concentration of Ni or the like in the manufacturing process (hereinafter referred to as “Ni concentrated layer” for convenience of explanation), the present inventors concentrated Ni during the hot rolling process. A method for properly removing the layer was studied. As a result, as effective conditions for removing the Ni concentrated layer, (1) it is effective to expose the Ni concentrated layer to the atmosphere and oxidize and remove it. In particular, the scale is grown sufficiently over time. (I.e., after sufficiently oxidizing the Ni concentrated layer), it is preferable to perform descaling. (2) When the plate thickness of the material is reduced by rolling, the Ni concentrated layer is also thinned. We found the fact that it is easy to oxidize and remove the Ni-enriched layer, and (3) it is necessary to suppress the decrease in the surface temperature of the material as much as possible in order to effectively oxidize the Ni-enriched layer. . And as a result of examining a specific and optimum method for satisfying such conditions, the exit side of the heating furnace, the entrance side of each rough rolling mill in the rough rolling process (or the entrance side of each pass in reverse rolling) In addition, in addition to performing descaling by high-pressure water injection on the entry side of the finish rolling mill row, the descaling by high pressure water injection is performed at least at one point between the rough rolling mill train and the finishing rolling mill train. It has been found that the Ni concentrated layer can be appropriately oxidized and removed by carrying out the process. That is, generally, there is a long interval of about 100 m or more between the rough rolling mill row and the finishing rolling mill row, and by performing descaling at about one or two places in the middle between these, It has been found that the Ni concentrated layer can be appropriately oxidized and removed by the action effect.
(I) Descaling performed after sufficiently generating and growing a scale using a long moving distance (moving time) of several tens of meters is performed at least twice (that is, the “deposition at the intermediate position”). Scaling (one or more locations) "and" Descaling on the entry side of the finishing mill line ").
(Ii) Moreover, since the material subjected to such descaling is rough-rolled to reduce the plate thickness and the Ni concentrated layer, the Ni concentrated layer is easily removed by oxidation.
(Iii) Furthermore, unlike the case where the above-mentioned “descaling at the intermediate position” is descaled on the entry side of the rolling mill, the material does not come into contact with the rolling roll immediately after that, so the surface temperature is unlikely to decrease. Therefore, scale can be generated and grown effectively, and the Ni concentrated layer is easily removed by oxidation from this point.

The present invention has been made on the basis of such findings and has the following gist.
[1] A method for producing a hot rolled steel sheet by a hot rolling facility equipped with a heating furnace, a rough rolling mill row, and a finishing rolling mill row from the upstream side of the line, the outlet side of the heating furnace, and the rough rolling mill The inlet side of each rough rolling mill constituting the row (however, in the case of a reverse type rough rolling mill row, the inlet side of each rolling pass) and the inlet side of the finishing rolling mill row are each made of steel plates by high-pressure water injection. In the manufacturing method for performing descaling (a),
At least one position between the rough rolling mill row and the descaling (a) position on the entry side of the finish rolling mill row, descaling (a _X ) of the steel sheet by high-pressure water injection is performed, and the descaling ( a _X) position, the inlet side of the final roughing mill constituting the rough rolling mill train (provided that the descaling position (a) in the case of rough rolling mill train of reversing the entry side of the final rolling pass) for descaling (a) position in the entry side of the finishing rolling mill train, the manufacturing method of the hot rolled steel sheet characterized by having each interval of at least 40m in the line direction.

[2] A method for producing a hot-rolled steel sheet by hot rolling equipment provided with a heating furnace, a rough rolling mill row, and a finishing rolling mill row from the upstream side of the line, wherein the outlet side of the heating furnace and the rough rolling mill The inlet side of each rough rolling mill constituting the row (however, in the case of a reverse type rough rolling mill row, the inlet side of each rolling pass) and the inlet side of the finishing rolling mill row are each made of steel plates by high-pressure water injection. In the manufacturing method for performing descaling (a),
Wherein at one point between the descaling (a) the position of the rough rolling mill train and the entry side of the finishing rolling mill train, perform descaling of the steel sheet by high pressure water jet (a _X), in the line direction, wherein descaling (a _X) wherein the position constituting the rough rolling mill train final rough rolling mill entry side (but, in the case of rough rolling mill train of reversing the entry side of the final rolling pass) descaling in (a) the distance L1 between the position, the descaling _{(a X)} ratio of distance L2 between descaling (a) position in the entry side of the finishing rolling mill train and the position [L1: L2] is 4: 6 to 6: 4. A method for producing a hot-rolled steel sheet, comprising:
[3] In the manufacturing method of [1] or [2 ] above, descaling (a) on the outlet side of the heating furnace and the inlet side of each of the rough rolling mills constituting the rough rolling mill train (however, the reverse type In the case of a rough rolling mill train, the descaling (a) at the entry side of each rolling pass) and the descaling (a _X ) use high-pressure water with a discharge pressure of 10 MPa or more, respectively, and enter the finish rolling mill train. In the descaling (a), a high-pressure water having a discharge pressure of 25 MPa or more is used.

[4] A heating furnace, a rough rolling mill row, and a finishing rolling mill row are provided from the upstream side of the line. The outlet side of the heating furnace and the inlet side of each of the rough rolling mills constituting the rough rolling mill row (however, reverse type) In the case of the rough rolling mill row, on the entry side of each rolling pass) and on the entry side of the finish rolling mill row, respectively, in the hot rolled steel sheet manufacturing equipment in which the high pressure water jet type descaling device (A) is arranged ,
A high-pressure water jet descaling device (A _X ) is disposed at at least one location between the rough rolling mill row and the high-pressure water jet descaling device (A) arranged on the entry side of the finish rolling mill row. and, the high pressure water jet descaler apparatus (a _X), the rough rolling mill train high pressure water jet descaling apparatus arranged on the entry side of the final roughing mill constituting the (a), said finish rolling A hot- rolled steel sheet manufacturing facility characterized by having an interval of 40 m or more in the line direction with respect to the high-pressure water jet descaling device (A) arranged on the entry side of the machine row.

[5] A heating furnace, a rough rolling mill row, and a finishing rolling mill row are provided from the upstream side of the line, and the exit side of the heating furnace and the inlet side of each of the rough rolling mills constituting the rough rolling mill row (however, reverse type) In the case of the rough rolling mill row, on the entry side of each rolling pass) and on the entry side of the finish rolling mill row, respectively, in the hot rolled steel sheet manufacturing equipment in which the high pressure water jet type descaling device (A) is arranged ,
A high-pressure water jet descaling device (A _X ) is arranged at one location between the rough rolling mill row and the high-pressure water jet descaling device (A) arranged on the entry side of the finish rolling mill row. in line direction, the distance between the high-pressure water jet descaler apparatus (a _X) and the rough rolling mill high pressure water jet descaling apparatus arranged on the entry side of the final roughing mill constituting the column (a) and L1, the ratio of the distance L2 between the high-pressure water jet descaler apparatus (a _X) and high-pressure water jet descaling apparatus arranged on the entry side of the finish rolling mill train (a) [L1: L2] is It is 4: 6-6: 4, The manufacturing equipment of the hot-rolled steel plate characterized by the above-mentioned.
[6] In the production facility of [4] or [5 ] above, the high pressure water jet descaling device (A) disposed on the outlet side of the heating furnace and the input of each rough rolling mill constituting the rough rolling mill train The high pressure water jet type descaling device (A) and the high pressure water jet type descaling device (A _X ) arranged on the side (however, in the case of the reverse type rough rolling mill row, the entrance side of each rolling pass) Each is a descaling device that injects high-pressure water with a discharge pressure of 10 MPa or more, and the high-pressure water injection type descaling device (A) arranged on the entrance side of the finishing rolling mill injects high-pressure water with a discharge pressure of 25 MPa or more. A hot-rolled steel plate manufacturing facility characterized by being a descaling device.

Here, the descaling (a) and the descaling (a _X ) in the manufacturing method of the present invention includes a case where a plurality of stages of descaling close in the line direction are performed at one descaling position. In other words, in this case, a descaling group composed of a plurality of adjacent descaling stages is defined as one descaling (a) and descaling (a _X ). Usually, the interval between each descaling in such a descaling group is within 10 m. If the distance between the descaling is within 10 m, the generation of the scale between them is almost negligible, and they can be regarded as one descaling.
Similarly, the high-pressure water injection type descaling device (A) and the high-pressure water injection type descaling device (A _X ) in the production facility of the present invention include a case where a plurality of stages of descaling means adjacent in the line direction are included. That is, in that case, a high-pressure water jet descaling device (A _X ) and a high-pressure water jet descaling device (A _X ) are made up of the descaling means group composed of the plurality of adjacent descaling means. Usually, the interval between each descaling means in such a descaling means group is within 10 m. If the distance between the descaling means is within 10 m, the generation of the scale between them is almost negligible, and they can be regarded as one descaling device.

  According to the manufacturing method and manufacturing equipment of the present invention, it is possible to reliably oxidize and remove a concentrated layer such as Ni on the surface of the material in the manufacturing process, and to effectively generate surface defects due to the concentration of Ni or the like. It is possible to produce a hot rolled steel sheet that is suppressed and has good surface properties. In addition, in the manufacturing method and equipment according to the present invention, in addition to the conventional descaling, only the descaling is performed at least at one location between the rough rolling mill row and the finishing rolling mill row, thereby reducing the production efficiency. And can be easily carried out industrially.

FIG. 1 shows an embodiment of a method and equipment for producing a hot-rolled steel sheet according to the present invention. This hot-rolling equipment comprises a heating furnace 1 and a rough rolling machine 20 from the upstream side of the line. A rolling mill row 2 and a finishing rolling mill row 3 including a plurality of finishing rolling mills 30 are provided. In the figure, 4 is a material to be rolled.
Similarly to the conventional general hot rolling equipment, the exit side of the heating furnace 1, the entrance side of each of the rough rolling mills 20 constituting the rough rolling mill row 2, and the entrance side of the finish rolling mill row 3 Are respectively provided with high-pressure water jet descaling devices A ₁ , A ₂ , A ₃ (hereinafter simply referred to as “descaling devices A ₁ , A ₂ , A ₃ ”), and these descaling devices A ₁ -A By the high pressure water injection from ₃ , the descaling (a ₁ ), (a ₂ ), (a ₃ ) of the material 4 to be rolled is performed at each position. The reason for performing these descaling (a ₁ ) to (a ₃ ) and preferable conditions will be described in detail later.

The intermediate position between the rough rolling mill row 2 and the entry-side descaling device A ₃ (descaling (a ₃ ) position) of the finishing rolling mill row 3 has a high-pressure water jet descaling device A _X ( Hereinafter, simply referred to as “descaling device A _X ” is arranged, and descaling (a _X ) of the material to be rolled 4 is performed by high-pressure water injection from the descaling device A _X.
In the hot rolled steel sheet production line (hot rolling equipment), in order to prevent one rolled material from being caught in the roughing mill 20 and the finishing mill 30 at the same time, the rough rolling mill train 2 and the finishing rolling mill. The interval S between the rows 3 is configured to be longer than the entire length of the material to be rolled (rough rolled bar), and therefore usually has a length of about 100 m or more. In the present invention, the descaling performed after sufficiently generating and growing the scale using such a long moving distance of the material to be rolled is at least twice (that is, descaling (a _X )). By performing descaling (a ₃ )) at the finishing rolling mill train entry side, a concentrated layer such as Ni (hereinafter referred to as “Ni concentrated layer” for convenience of explanation) is effectively oxidized and removed.

Accordingly, in the line direction, descaling device A _X and the final rough rolling mill inlet side of 20 descaling device interval between A ₂ (distance) L1, similarly descaling apparatus A _X and finish rolling mill of the column 3 of the entry side descaling device a ₃ distance between (distance) L2 preferably has a respective length sufficient. Specifically, the distances L1 and L2 are each preferably 40 m or more.
In addition, when the descaling device A _X as in the present embodiment is provided only in one location, descaling device A _X final rough rolling machine inlet side of 20 descaling device A ₂ and finishing rolling mill train 3 since it is preferable that as much as possible located closer to the center between the descaling device a ₃ of the entry side, the ratio of the distance L1 and the distance L2 [L1: L2] 4: 6 to 6: is preferably about 4.
In order to fully oxidize the Ni concentrated layer remaining after descaling (a _X ) by the descaling apparatus A _X, it is necessary to completely remove the secondary scale by descaling (a _X ). In descaling (a _X ), it is desirable to use high-pressure water having a discharge pressure of 10 MPa or more, preferably 15 Mpa or more (discharge pressure from a nozzle; the same applies hereinafter).

As described above, in at least one place between the descaling device A ₃ of the input-side rolling mill train 3 and the rough rolling mill train 2 finish _(descaling (a ₃₎ located), de by descaling device A _X By performing scaling (a _X ), (i) Descaling is performed at least twice after sufficiently generating and growing the scale using a long moving distance (moving time) of several tens of meters. That is, descaling (a _X ) (in the present embodiment, once) and descaling (a ₃ ) on the finishing mill line entry side can be performed, (ii) such descaling (a _X ), The material to be rolled 4 subjected to (a ₃ ) is roughly rolled to reduce the plate thickness and the Ni concentrated layer is also thinned, so that the Ni concentrated layer is easily oxidized and removed. (Iii) Descaling the rolling _{(a X)} is made 4 is different from the case where descaling is performed on the entrance side of the rolling mill, and the surface temperature is unlikely to decrease immediately after contact with the rolling roll, so that the scale can be generated and grown effectively. The Ni concentrated layer can be effectively oxidized and removed by the three elements (effects) that the Ni concentrated layer is easily oxidized and removed.

Conventionally, it is common knowledge that descaling during the rough rolling-finish rolling process is performed on the entry side of the rolling mill in order to prevent the scale from biting into the rolling roll. There was no recognition of any meaning or necessity for performing descaling at an intermediate position between the finishing mill rows 3. In addition, descaling by high-pressure water injection leads to a decrease in the temperature of the material to be rolled, and the energy consumption and equipment burden are large. Therefore, the descaling is limited to places where the necessity is recognized (mainly on the rolling mill entrance side). Is normal. In contrast to such conventional recognition and prior art, in the present invention, the intermediate position between the rough rolling mill row 2 and the finishing rolling mill row 3 is aimed at oxidizing and removing the Ni concentrated layer due to the above-described effects. In this case, descaling (a _X ) is performed.

The descaling (a ₃ ) on the entrance side of the finishing rolling mill row 3 is a conventional descaling, but in the present invention, the scale generated and grown again after the descaling (a _X ) is removed. By doing so, it is extremely important in the sense that the remaining Ni concentrated layer is surely removed. For this reason, in descaling (a ₃ ), it is desirable to use high-pressure water having a discharge pressure of 25 MPa or more, more preferably 30 MPa or more. If the discharge pressure of the high-pressure water is less than 25 MPa, the effect may be insufficient from the viewpoint of reliably removing the remaining Ni concentrated layer. Further, if high pressure water having a discharge pressure of 50 Mpa or more is used, the surface property is further improved because Ni can be removed from the metal Fe due to the excavation effect of the high pressure water.
Further, the descaling (a ₃ ) position by the descaling device A ₃ on the entry side of the finishing mill row 3 is from the roll biting position of the first stage finishing mill 30 in order to suppress scale generation after descaling. It is desirable to be within 10 m in the line direction.
Incidentally, when said out by the temperature drop of the rolled material 4 of descaling (a _X) becomes a problem, it should be placed in the heating apparatus of the rolled material immediately before the descaling (a ₃₎ located, What is necessary is just to heat the to-be-rolled material 4 as needed.

Next, descaling (a ₁ ) performed on the exit side of the heating furnace 1 and descaling (a ₂ ) performed on the entry side of each of the rough rolling mills 20 constituting the rough rolling mill row 2 will be described.
In the heating furnace 1, a very thick scale called primary scale is generated on the slab surface. If rough rolling is performed with this remaining, surface defects may occur due to biting of the primary scale. Therefore, descaling (a ₁ ) is performed by high-pressure water injection from the descaling device A ₁ , The scale needs to be removed. This descaling (a ₁ ) may be performed a plurality of times. In order to reliably remove the primary scale, it is desirable to use high-pressure water having a discharge pressure of 10 MPa or more, preferably 15 Mpa or more in descaling (a ₁ ).

On the entry side of each of the rough rolling mills 20 constituting the rough rolling mill row 2, descaling (a ₂₎ by high-pressure water injection from the descaling apparatus A _{2 is performed} in order to prevent surface defects caused by secondary scale biting. ) Is necessary. Further, the descaling (a ₂ ) performed here is also effective for removing the Ni-enriched layer by oxidation.
In order to promote the oxidation of the Ni concentrated layer after descaling (a ₂ ) on the entry side of the final roughing mill 20, it is necessary to completely remove the secondary scale by descaling (a ₂ ). Therefore, in descaling (a ₂ ), it is desirable to use high-pressure water having a discharge pressure of 10 MPa or more, preferably 15 Mpa or more.

Further, the descaling (a ₂ ) position by the descaling device A ₂ on the entry side of the rough rolling mill 20 is 10 m in the line direction from the roll biting position of the rough rolling mill 20 in order to suppress scale generation after descaling. It is desirable to be within.
In the production line (hot rolling equipment) for hot rolled steel sheets, the interval S between the rough rolling mill row 2 and the finishing rolling mill row 3 cannot be made longer from the viewpoint of securing the material temperature and the equipment space. In order to make the effect of the present invention particularly reliable, the interval S is desirably 120 m or more, more preferably 150 m or more.

In the present invention, the descaling devices A _X are arranged at two or more places between the rough rolling mill row 2 and the descaling device A ₃ on the entry side of the finish rolling mill row 3, and descaling (a _X ) is performed in each of them. May be performed.
Figure 2 is a manufacturing method and equipment of the hot rolled steel sheet according to the present invention, there is shown an embodiment in the case where a descaling device A _X in two places.
High pressure water jet descaling devices A _X1 , A _X2 are located at an intermediate position between the roughing mill row 2 and the finishing descaling device A ₃ (descaling (a ₃ ) position) of the finishing mill row 3. (hereinafter, simply referred to as "a descaling device _{a X1, a X2")} is disposed, these descaling device _{a X1,} the rolled material 4 of descaling by high pressure water jetting from _{a X2 (a X1), (} a X2 ) Is performed.

Even when a plurality of descaling devices A _X1 and A _X2 are arranged in this manner, the upstream descaling device A _X1 and the final roughing mill 20 are inserted in the line direction for the reason described above. distance between the descaling device a ₂ side (distance) L1, well spacing between the descaling device a ₃ of the entry side of the rolling mill train 3 finish the descaling device a _X2 on the downstream side (distance) L2 is sufficiently respectively It is preferable to have a long length. Similarly, it is preferable that the interval (distance) L3 between the adjacent descaling devices A _X1 and A _X2 also has a sufficient length. Specifically, the intervals L1, L2, and L3 are each preferably 40 m or more.
When a plurality of descaling devices A _X1 and A _X2 are arranged as described above, descaling is performed after sufficient scale is generated and grown between the rough rolling mill row 2 and the finish rolling mill row 3. Can be performed at least three times, that is, descaling (a _X1 ), (a _X2 ) and descaling (a ₃ ) on the finishing rolling mill train entry side.
Other configurations and preferable conditions are the same as those in the embodiment of FIG.

In the present invention, the rough rolling machine train may be of a reverse type.
FIG. 3 shows an embodiment of a method and equipment for producing a hot-rolled steel sheet according to the present invention, in which the rough rolling mill train is a reverse type.
The hot rolling equipment includes a heating furnace 1 from the upstream side of the line, a reverse rough rolling mill row 2a composed of a plurality of rough rolling mills 20a, and a finishing rolling mill row 3 composed of a plurality of finishing rolling mills 30, Descaling devices A _{1 to} A ₃ are arranged on the entry side of the heating furnace 1, on the entry side of each rolling pass in the reverse rough rolling mill row 2 a, and on the entry side of the finishing rolling mill row 3, respectively. The descaling (a ₁ ) to (a ₃ ) of the material to be rolled 4 is performed at each position by high-pressure water injection from these descaling devices A _{1 to} A ₃ . In the rough rolling mill row 2a of this embodiment, reverse rolling is performed by the first stage and second stage rough rolling machine 20a, so that the descaling device A ₂ is provided before and after the first stage and second stage rough rolling mill 20a. Are arranged, and descaling (a ₂ ) is performed on the entry side of each rolling pass of reverse rolling.
As in the embodiment of FIG. 1, the descaling device A is positioned at an intermediate position between the descaling device A ₃ (descaling (a ₃ ) position) on the entry side of the rough rolling mill row 2 and the finishing rolling mill row 3. _X is disposed, and descaling (a _X ) of the material to be rolled 4 is performed by high-pressure water injection from the descaling apparatus A _X.
Other configurations and preferable conditions are the same as those of the embodiment of FIGS.

In the descaling (a) and descaling (a _X ) in the manufacturing method of the present invention, there are cases where multiple stages of descaling close in the line direction are performed at one descaling position. That is, in that case, one descaling (a) and descaling (a _X ) are performed by a descaling group including a plurality of adjacent descaling steps. Usually, the interval between each descaling in such a descaling group is within 10 m. If the distance between the descaling is within 10 m, the generation of the scale is almost negligible in the meantime, and they can be regarded as one descaling.
Similarly, descaling device A, descaling apparatus A _X in the production facility of the present invention may have a descaling means in a plurality of stages that are close in the line direction. That is, if so, descaling means group consisting of descaling means in a plurality of stages that they close constitute one descaling device A, the descaling device A _X. Usually, the interval between each descaling means in such a descaling means group is within 10 m. If the distance between the descaling means is within 10 m, the generation of the scale between them is almost negligible, and they can be regarded as one descaling device.

A hot-rolled steel sheet was manufactured in a hot rolling facility in which the heating furnace 1, rough rolling mill rows 2, 2a, and finishing rolling mill row 3 as shown in FIGS. The reference numerals in the drawings correspond to FIGS. Moreover, the space | interval (distance) between a rough rolling mill row | line | column and a finishing rolling mill row | line | column is displayed on FIGS.
Descaling device A ₂ on the entry side of each rough rolling mill in the rough rolling mill row 2 in FIGS. 4 to 7, and on the rolling pass entry side by each rough rolling mill in the reverse type rough rolling mill row 2a in FIGS. scaler _{a 2} are both placed from roughing mill 20,20a at the position of 4 to 8 m. 5, 7, and 9, the descaling device _AX is disposed at one or more locations between the roughing mill row 2 and the descaling device A ₃ on the entry side of the finish rolling mill row 3. The intervals between the descaling devices adjacent in the line direction are L1, L2 in FIGS. 5 and 9, and L1, L2, L3 in FIG.

In this example, a low carbon steel slab having chemical components shown in Table 1 was used as the material to be rolled. Table 2 shows the production conditions and the evaluation results of the surface properties of the hot-rolled steel sheet. The surface texture was evaluated visually in five stages from 1 (poor) to 5 (excellent) by visually judging the density and frequency of occurrence of the surface pattern seen after pickling the hot-rolled steel sheet. A rating of 3 or higher is a practically acceptable level, a rating of 4 is a good level, and a rating of 5 is a very good level at which a pattern cannot be visually recognized.
As shown in Table 2, the hot rolled steel sheets produced in the inventive examples all have good surface properties. In contrast, no. 1, No. 1 8, no. In the comparative example of 12, since the descaling (a _X ) is not performed between the rough rolling mill row 2 and the finish rolling mill row 3, the surface property of the steel sheet is extremely high due to the pattern caused by the surface concentration such as Ni. Inferior. No. In the comparative example 4, since the descaling (a _X ) is performed at a position close to the descaling (a ₂ ) on the entry side of the finish rolling mill row 3, only the effect as the descaling (a ₂ ) group can be obtained. Therefore, this is a comparative example in which descaling (a _X ) is not substantially performed. Similar to 1 and the like, the surface properties of the steel sheet are extremely inferior.

A manufacturing method and equipment for hot-rolled steel sheet according to the present invention, explanatory view showing an embodiment in the case where a descaling device A _X in one place A manufacturing method and equipment for hot-rolled steel sheet according to the present invention, explanatory view showing an embodiment in the case where a descaling device A _X in two places Explanatory drawing which shows one Embodiment when it is a manufacturing method and installation of the hot-rolled steel plate by this invention, and a rough rolling mill row | line | column is a reverse type Explanatory drawing which shows the production line used for the Example Explanatory drawing which shows the production line used for the Example Explanatory drawing which shows the production line used for the Example Explanatory drawing which shows the production line used for the Example Explanatory drawing which shows the production line used for the Example Explanatory drawing which shows the production line used for the Example

Explanation of symbols

1 oven 2 rough rolling mill train 2a reversing roughing mill train 3 finish rolling mill train 4 the rolled material 20,20a rough rolling mill 30 finishing mill _{A 1, A 2, A 3} , A X, A X1, A _X2 descaling device _{a 1, a 2, a 3} , a X, a X1, a X2 descaling position

Claims (6)

A method of manufacturing a hot rolled steel sheet by a hot rolling facility equipped with a heating furnace, a rough rolling mill row, and a finishing rolling mill row from the upstream side of the line, comprising the outlet side of the heating furnace and the rough rolling mill row Descaling of steel sheets by high-pressure water injection at the entry side of each rough rolling mill (however, in the case of a reverse type rough rolling mill row, the entry side of each rolling pass) and at the entry side of the finish rolling mill row ( In the manufacturing method of performing a),
At least one location between the rough rolling mill row and the descaling (a) position on the entry side of the finishing rolling mill row, descaling of the steel sheet by high-pressure water injection (a _X ),
The descaling (a _X) position, the descaling in the inlet side of the final roughing mill constituting the rough rolling mill train (However, if the rough rolling mill train of reversing the entry side of the final rolling pass) ( a) a position, with respect to descaling (a) position in the entry side of the finishing rolling mill train, the manufacturing method of the hot rolled steel sheet characterized by having each interval of at least 40m in the line direction. A method of manufacturing a hot rolled steel sheet by a hot rolling facility equipped with a heating furnace, a rough rolling mill row, and a finishing rolling mill row from the upstream side of the line, comprising the outlet side of the heating furnace and the rough rolling mill row Descaling of steel sheets by high-pressure water injection at the entry side of each rough rolling mill (however, in the case of a reverse type rough rolling mill row, the entry side of each rolling pass) and at the entry side of the finish rolling mill row ( In the manufacturing method of performing a),
Descaling the steel sheet by high-pressure water injection (a _X ) at one location between the rough rolling mill row and the descaling (a) position on the entry side of the finishing rolling mill row ,
In line direction, the descaling (a _X) at a position between the rough rolling mill train constituting the final rough rolling mill entry side (but, in the case of rough rolling mill train of reversing the entry side of the final rolling pass) the distance L1 between the descaling position (a), the descaling (a _X) ratio of distance L2 between descaling (a) position in the entry side of the finishing rolling mill train and the position [L1: L2] 4 : 6 to 6: 4. A method for producing a hot- rolled steel sheet. Descaling (a) on the outlet side of the heating furnace, and the inlet side of each rough rolling mill constituting the rough rolling mill row (however, in the case of a reverse type rough rolling mill row, the inlet side of each rolling pass) In descaling (a) and descaling (a _X ), high pressure water having a discharge pressure of 10 MPa or more is used, and in descaling (a) on the entry side of the finishing rolling mill row, a high pressure of 25 MPa or more is used. Water is used, The manufacturing method of the hot rolled steel plate of Claim 1 or 2 characterized by the above-mentioned. A heating furnace, a rough rolling mill row, and a finish rolling mill row are provided from the upstream side of the line, and the outlet side of the heating furnace and the inlet side of each rough rolling mill constituting the rough rolling mill row (however, reverse rough rolling) In the case of a machine train, on the entry side of each rolling pass), and on the entry side of the finish rolling machine train, respectively, in the hot rolling steel sheet manufacturing equipment in which the high pressure water jet type descaling device (A) is arranged,
A high-pressure water jet descaling device (A _X ) is disposed at at least one location between the rough rolling mill row and the high-pressure water jet descaling device (A) arranged on the entry side of the finish rolling mill row. And
The high pressure water jet descaler apparatus (A _X), said rough rolling mill high pressure water jet descaling apparatus arranged on the entry side of the final roughing mill constituting the column (A), said finish rolling mill train A hot- rolled steel sheet manufacturing facility characterized by having a distance of 40 m or more in the line direction with respect to the high-pressure water jet descaling device (A) disposed on the inlet side of the steel sheet. A heating furnace, a rough rolling mill row, and a finish rolling mill row are provided from the upstream side of the line, and the outlet side of the heating furnace and the inlet side of each rough rolling mill constituting the rough rolling mill row (however, reverse rough rolling) In the case of a machine train, on the entry side of each rolling pass), and on the entry side of the finish rolling machine train, respectively, in the hot rolling steel sheet manufacturing equipment in which the high pressure water jet type descaling device (A) is arranged,
A high-pressure water jet descaling device (A _X ) is arranged at one location between the rough rolling mill row and the high-pressure water jet descaling device (A) arranged on the entry side of the finish rolling mill row. ,
In the line direction, the distance between the high-pressure water jet descaler apparatus (A _X) and the rough rolling mill high pressure water jet descaling apparatus arranged on the entry side of the final roughing mill constituting the column (A) L1 When the ratio of the distance L2 between the high-pressure water jet descaler apparatus (a _X) and high-pressure water jet descaling apparatus arranged on the entry side of the finish rolling mill train (a) [L1: L2] 4 : 6-6: 4 Hot rolled steel sheet manufacturing equipment, High pressure water jet descaling device (A) arranged on the outlet side of the heating furnace and the inlet side of each rough rolling mill constituting the rough rolling mill train (however, in the case of a reverse type rough rolling mill train, each rolling The high pressure water injection type descaling device (A) and the high pressure water injection type descaling device (A _X ) arranged on the entrance side of the path are each a descaling device that injects high pressure water with a discharge pressure of 10 MPa or more. There, finishing mill high pressure water jet descaler device disposed on the entry side of the column (a) is according to claim 4 or 5, characterized in that a descaling device for injecting high-pressure water or the discharge pressure 25MPa Manufacturing equipment for hot-rolled steel sheet according to 1.

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