JP3802830B2 - Steel sheet descaling method and equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a descaling method and equipment by high-pressure water injection performed before or after a hot finish rolling mill or before or after a hot straightening machine when manufacturing a steel sheet by hot rolling.
[0002]
[Prior art]
When manufacturing a steel plate by hot rolling, it is known that a primary scale is generated in the process of heating a steel slab in a heating furnace, and a secondary scale is generated in the course of rough rolling and finish rolling.
Since these scales are bitten during hot rolling and remain on the surface of the steel sheet to generate scale wrinkles and reduce the surface quality of the steel sheet, they are described, for example, in JP-A-7-178436. As described above, it is disclosed that the primary scale is removed immediately before the start of hot rolling, and the secondary scale is removed by descaling by high-pressure water injection in the course of rough rolling and finish rolling. In the case where a straightening machine is arranged later to straighten the shape of the steel sheet, descaling is also disclosed after the straightening machine.
[0003]
On the other hand, in order to obtain uniform material properties and flatness, it is necessary to perform cooling control so that the temperature distribution in the sheet width direction is uniform. For example, Japanese Patent Application Laid-Open No. 9-57327 discloses the completion of finish rolling. In the case of performing forced correction after hot straightening, descaling is performed at least one of immediately before and after the final pass of finish rolling, and the secondary scale is grown after hot straightening after finish rolling. Disclosed is to manufacture steel sheets with excellent mechanical properties, shape, and surface properties by performing scaling immediately before forced cooling to suppress scale growth and prevent uneven cooling during straightening cooling. Has been.
[0004]
However, in the case of descaling after finish rolling according to the above-described conventional example, particularly on the upper surface side of the steel plate, for example, as shown in FIG. 7, the descaling water including the scale after descaling is not uniform on the steel plate. There is a problem that a flow is formed and stays in a wide area, and partial supercooling and uneven cooling occur due to descaling water, resulting in deterioration of material and shape characteristics.
Moreover, since the discharging power of descaling water is not sufficient, and the scale once removed (peeled) by descaling cannot be effectively discharged, there are many scales remaining on the upper surface of the steel sheet, In the hot straightening process, there is also a problem that it is difficult to produce a steel sheet having excellent surface properties by generating indentation wrinkles (scale wrinkles) due to residual scale.
[0005]
[Problems to be solved by the invention]
The present invention suppresses retention of descaling water on a steel sheet when performing descaling by high-pressure water injection on a steel sheet immediately before or immediately after hot finish rolling, or immediately before or after a hot straightening machine. It is possible to manufacture steel sheets with excellent surface properties and mechanical properties by preventing the occurrence of overcooling and uneven cooling, and suppressing the adhesion of the scale once removed (peeled) by descaling to the steel sheet surface. The present invention provides a method and equipment for descaling steel sheets.
[0006]
[Means for Solving the Problems]
The present invention basically relates to descaling by high-pressure water jet arranged before or after a hot finish rolling mill or before or after a hot straightening machine in the case of producing a steel sheet by hot rolling. The present invention is applied as equipment, and the following (1) to (8) are summarized.
(1) In the case of producing a steel sheet by hot rolling, it is applied when descaling by high-pressure water jet to the steel sheet before or after the finish rolling mill or before or after the hot straightening machine. A descaling method for performing descaling and draining of descaling water, in which 3 to 20 MPa of descaling water is injected from a high pressure water injection nozzle to collide with the steel plate, and the descaling is performed on the upper surface side of the steel plate. Flow of descaling water after collision with the upper surface of the steel sheet, with 0.2 to 2 MPa draining water injected from the low pressure water injection nozzle onto the upper surface of the steel sheet at a distance of 500 to 4000 mm from the collision point with the upper surface of the steel sheet. The steel sheet descaling method is characterized in that the collision flow is forcedly discharged from both side edges of the upper surface of the steel sheet.
(2) In (1), descaling water and draining water are collided 2 to 30 degrees outward in the width direction of the steel sheet with respect to the traveling direction of the steel sheet, and the descaling water after the collision on the steel sheet upper surface A method for descaling a steel sheet, characterized by causing a flow and a flow of drained water to collide with each other.
[0007]
(3) In the case of producing a steel sheet by hot rolling, it is applied when descaling by high-pressure water injection to the steel sheet before or after the finish rolling mill or before or after the hot straightening machine. Descaling equipment The descaling equipment injects water with a pressure of 3 to 20 MPa. Descaling device with multiple high-pressure water jet nozzles And 0.2 to 2 MPa drained water is injected. A water draining device on the upper surface side of a steel plate provided with a plurality of low pressure water injection nozzles And the nozzle of the descaling device and the nozzle of the draining device face each other in the sheet passing direction, and the descaling device and the draining device are connected to a point of collision with the steel plate of the descaling water, the draining water, and the steel plate. So that the distance from the collision point is 500-4000mm Place and Said From drainer After collision with the upper surface of the steel plate Draining water The flow of , Said From descaling equipment After collision with the top surface of the steel plate The flow of descaling water, From the collision point between the descaling water and the steel plate upper surface to the collision point between the drain water and the steel plate upper surface A steel sheet descaling facility characterized in that the collision flow is caused to collide within an area and the collision flow is stably discharged from both ends of the upper surface of the steel sheet.
(4) In (3), the plurality of high-pressure water injection nozzles of the descaling device is a steel plate Top In order to form a discharge flow having an oval horizontal cross section at the point of collision with the steel plate, this discharge flow is symmetrical with respect to the width direction center line of the steel sheet and is directed to the outside in the width direction of the steel sheet. It is arranged at an angle of 2 to 30 degrees (twisting angle) with respect to the traveling direction of the steel plate, and the plurality of low pressure water injection nozzles of the water draining device are steel plates. Top The steel sheet is formed so as to form a discharge flow having a rectangular horizontal cross section at the point of collision with the steel sheet, and the discharge flow is symmetric with respect to the width direction center line of the steel plate and is directed to the outside in the width direction of the steel plate. The steel sheet descaling equipment is arranged at an angle of 2 to 30 degrees (twisting angle) with respect to the traveling direction of the steel sheet.
[0008]
(5) In (3) or (4), the high-pressure water injection nozzle of the descaling device is disposed at an angle of 0 to 30 degrees (injection angle) with respect to the vertical line, and faces this high-pressure water injection nozzle. The low-pressure water injection nozzle of the draining device arranged as described above is arranged at an angle of 2 to 60 degrees (injection angle) with respect to the vertical line so as to form a collision flow of descaling water and draining water Steel sheet descaling equipment.
(6) In any one of (3) to (5), the width-wise injection region of the steel plate for drained water by the plurality of low-pressure water injection nozzles is a steel plate for descaling water by the plurality of high-pressure water injection nozzles. of A descaling equipment for a steel sheet, wherein a high-pressure water injection nozzle of a descaling device and a low-pressure water injection nozzle of a draining device are arranged so as to be shorter than the injection region in the width direction.
(7) Any of (3) to (6) Is arranged before or after the hot finishing mill, or after or before the hot straightening machine Steel sheet descaling equipment.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, basically, in the case of producing a steel sheet by hot rolling, before or after the finish rolling mill or before or after the hot straightening machine, the steel sheet is subjected to high pressure water injection. A descaling method and equipment for performing descaling and descaling water draining applied when performing scaling, wherein 3 to 20 MPa descaling water is supplied from a plurality of high pressure water injection nozzles in the width direction of the steel plate. The angle (twisting angle) is 2 to 30 degrees with respect to the direction of travel of the steel plate, and is injected to collide with the steel plate. On the upper surface side of the steel plate, 500 to 4000 mm from the collision point with the steel plate upper surface of the descaling water. A 0.2 to 2 MPa drain water from a plurality of low-pressure water jet nozzles on the upper surface of the steel plate separated by a distance of 2 to 3 in the width direction of the steel plate with respect to the traveling direction of the steel plate (twist angle) The steel sheet is ejected toward the outside to make it collide, and the flow of the descaling water and the drained water after the collision are made to collide with the upper surface of the steel sheet, and this collision flow is forcedly discharged from both ends of the upper surface of the steel sheet. The descaling water flow is made uniform in a certain area on the upper surface to prevent partial overcooling and uneven cooling.
At the same time, the scale once removed (peeled) by descaling is floated by the collision flow, and it is more reliably discharged to prevent adhesion residue on the upper surface of the steel sheet. This makes it possible to produce a steel sheet with good surface properties and mechanical properties after straightening.
[0010]
The basic shape of the discharge flow of descaling water from the high pressure water injection nozzle of the descaling device and the draining water from the low pressure water injection nozzle of the descaling water draining device spreads in a fan shape from the nozzle and is long at the point of collision with the steel plate. It is a shape having a circular horizontal cross section. The oval shape referred to in the present invention is mainly a shape obtained by crushing an elliptical shape so that the long axis is long, a rectangular shape in which both ends are formed in an arc shape, or a shape similar to these shapes. It is.
The descaling is performed on the upper surface side and the lower surface side of the steel plate, and the descaling water is preferably high pressure water of 3 to 20 MPa. If the pressure of the descaling water is less than 3 MPa, the descaling capability is insufficient, and if it exceeds 20 MPa, the descaling device becomes excessive, which is not preferable.
The descaling water is preferably jetted at an angle (spray angle) of 0 to 30 degrees with respect to the vertical line. If the angle (injection angle) exceeds 30 degrees, sufficient descaling force cannot be obtained.
[0011]
The descaling water is drained on the upper surface side of the steel sheet. The draining water is a low pressure water of 0.2 to 2 MPa. When colliding with the upper surface of the steel plate, the scale removed (peeled) by descaling is floated, and in order to ensure sufficient impact force to discharge the descaling water from the steel plate, It is preferable to inject at an angle (injection angle) of 2 to 60 degrees with respect to the vertical line so as to face the flow of descaling water.
If the angle is less than 2 degrees, the impact force against the flow of the descaling water is insufficient, the scale floating action becomes insufficient, and the descaling water cannot be discharged stably in a certain region. If the angle (injection angle) exceeds 60 degrees, the collision flow between the descaling water flow and the draining water flow becomes unstable, and stable discharge cannot be performed in a certain region.
A sufficient effect can be obtained by setting the injection pressure from the injection nozzle of the drained water to about 0.2 to 2 MPa and the total injection amount (capacity) to about 20 to 60% of the total injection amount of the descaling water. . If the spray pressure of the drained water exceeds 2 MPa, the descaling effect by the descaling water tends to decrease, which is not preferable. On the other hand, if it is less than 0.2 MPa, the stable discharging effect in a certain area of descaling water becomes insufficient, which is not preferable.
[0012]
About the distance between the collision point with the steel plate upper surface of descaling water, and the collision point with the steel plate upper surface of draining water, 500-4000 mm is preferable. When the distance between the collision points is less than 500 mm, the draining water affects the descaling ability, and a phenomenon that the descaling ability is reduced occurs. This is because the colliding force of the descaling water is attenuated by the stagnant water formed by the draining water and the descaling water before the collision with the steel plate. Further, the draining ability is reduced, and the descaling water spreads beyond the collision position of the draining water, and the unevenness of the steel sheet cooling cannot be suppressed.
If the distance between the collision points exceeds 4000 mm, the steel plate will be cooled by descaling water and draining water, and the temperature will decrease significantly, or cooling unevenness will occur, which may affect the mechanical properties of the steel material. Is not preferable.
In this way, by draining the descaling water from the side edges of the steel sheet by draining the descaling water, it is possible to suppress non-uniformity of the steel sheet cooling caused by non-scaling of the descaling water on the top surface of the steel sheet. The removed scale can be stably suspended and removed.
[0013]
In the present invention, the descaling water and draining water are jetted toward the outside of the steel sheet in the width direction of the steel sheet by an angle (twisting angle) of 2 to 30 degrees with respect to the traveling direction of the steel sheet and collide with the upper surface of the steel sheet. The collision flow of drained water can be easily and stably forcibly discharged from both ends of the steel sheet. To that end, multiple spray nozzles that eject descaling water and descaling water are discharged. It arrange | positions at an angle (twisting angle) 2-30 degree | times with respect to the advancing direction of a steel plate so that a flow may be line-symmetrically set to the width direction centerline of a steel plate, and may face the outer side of the width direction of a steel plate.
If the angle (twist angle) is less than 2 degrees, the discharge characteristics from both sides of the steel sheet cannot be sufficiently applied to the collision flow of descaling water and draining water, and the discharge But It becomes unstable. On the other hand, if the angle (twist angle) exceeds 30 degrees, the number of descaling nozzles for descaling the entire steel sheet increases, which is economically disadvantageous.
By making the angle (twist angle) within the appropriate range, the collision flow of descaling water and draining water can be forced and discharged from both ends of the steel plate more easily and stably. Can be more reliably suppressed.
[0014]
The length of the area where the spray nozzles are arranged in the width direction of the steel sheet is centered in the width direction of the steel sheet in order to efficiently use the drain water and increase the discharge efficiency of the collision flow with descaling water. It is effective to make the length equal to or more than 10% of the length of the arrangement area of the descaling water injection nozzle. If it is less than 10%, it becomes difficult to discharge the entire amount of descaling water in a certain region.
Each high-pressure water injection nozzle of the descaling device has a discharge flow from the high-pressure water injection nozzle adjacent in the width direction of the steel plate in order to ensure a sufficient injection density of the high-pressure water and a sufficient descaling effect. It is preferable to arrange so that an overlapping portion d of about 5 to 10% is generated at the collision point with respect to the discharge direction.
[0015]
In addition, as descaling water and draining water, general industrial water such as soft water, hard water, or a mixed water thereof can be used, and a water quality adjusting agent such as an oxidation inhibitor is added to these industrial waters. Also consider. In the case of drained water, when cooling proceeds too much, a mixture of gases may be used.
By performing descaling and draining of descaling water as described above, it is possible to prevent scale residue once removed (peeled) by descaling on the steel sheet surface and prevent generation of scale flaws in the subsequent process. Can also be descaled water Therefore, it is possible to manufacture a steel sheet having good surface properties and mechanical properties.
[0016]
Below, the example of the descaling method of this invention and the example of an installation are demonstrated in detail based on FIGS.
In this example, as shown in FIG. 1, when the hot straightening machine 2 is disposed after the hot finish rolling mill 1 to correct the shape of the hot-rolled steel sheet 3, the front stage of the hot straightening machine 2. The descaling equipment of the present invention comprising the draining device 4 and the descaling device 5 is arranged on the surface, the scale on the surface of the hot rolled steel plate 3 is removed, and the steel plate 3 from which the scale has been removed is introduced into the hot straightening machine 2. The case of hot correction will be described as an example.
In this example, on the upper surface side of the steel plate 3, a draining device 4 is arranged at a distance L upstream of the descaling device 5, and the descaling water 6 and the draining water from the descaling device 5 are disposed as shown in FIG. The drained water 7 from the apparatus 4 is collided with the upper surface of the steel plate 3 and then collided in the region of the distance Ls, so that the collision flow 67 is forcibly discharged from both side ends of the steel plate 3.
On the lower surface side of the steel plate 3, the descaling water 6 falls by its own weight after descaling, so there is no problem of residual adhesion of the scale once removed (peeled), even when partial subcooling or cooling unevenness due to the descaling water is present. Only the descaling device 5 is arranged.
[0017]
The high pressure water injection nozzle 8 of the descaling device 5 and the low pressure water injection nozzle 11 of the water draining device 4 are long at the point where the discharge flows 6 and 7 collide with the steel plate 3 as shown in FIGS. It has a circular horizontal cross section, and is formed in a fan shape when viewed from the traveling direction of the steel plate 3 as shown in FIGS. 3 (b) and 3 (c). The high pressure water header 9 or the low pressure water header 10 are arranged in plural.
As shown in FIGS. 3B, 3C, and 3D, each high-pressure water injection nozzle 8 of the descaling apparatus 5 has a sufficient high-pressure water injection density and ensures a stable descaling effect. The discharge flow 6 of the high-pressure water injection nozzle 8 adjacent in the width direction of the steel plate 3 is arranged so that overlapping portions d and da are generated when viewed from the discharge direction.
[0018]
When a plurality of high-pressure water injection nozzles 8 of the descaling device 5 are arranged in the high-pressure water header 9, as shown in FIG. 4, the discharge holes are symmetrical with respect to the center line CL in the width direction of the steel plate 3. The low-pressure water injection nozzle 11 of the water draining device 4 is disposed at an angle of 2 to 30 degrees with respect to the length direction of the steel plate 3 so as to face the width direction of the steel plate 3. In the case where the discharge holes are arranged in the longitudinal direction, the discharge holes are twisted with respect to the length direction of the steel plate 3 so that the discharge holes are symmetrical with respect to the center line CL in the width direction of the steel plate 3 and are directed to the outside in the width direction of the steel plate 3. The angle (β) is inclined at 2 to 30 degrees.
As shown in FIG. 5, the injection angle (γ) of the discharge flow 6 from the plurality of high-pressure water injection nozzles 8 of the descaling device 5 with respect to the steel plate 3 is 0 to 30 degrees, and the high-pressure water injection nozzle 8 of the water draining device 4. The ejection angle (θ) of the discharge flow 6 from the steel plate 3 with respect to the steel plate 3 is inclined so as to be 2 to 60 degrees.
[0019]
In the present invention, the plurality of high-pressure water injection nozzles 8 of the descaling device 5 are arranged so that the discharge holes are symmetrical with respect to the width direction center line CL of the steel plate 3 and are directed to the outside in the width direction of the steel plate 3. The slanted arrangement with the twist angle (α) of 2 to 30 degrees with respect to the length direction of the steel plate is to uniformly spray the descaling water and to flow the descaling water mixed with the scale outward, It is for discharging efficiently.
When the twist angle α exceeds 30 degrees, the number of descaling nozzles for descaling the entire steel sheet increases, which is economically disadvantageous. Further, when the twist angle α is less than 2 degrees, the effect of discharging the descaling water 6 mixed with the scale from both side ends of the steel plate 3 becomes insufficient.
[0020]
Further, a plurality of low-pressure water injection nozzles 11 of the draining device 4 are arranged on the steel plate 3 so as to face the plurality of high-pressure water injection nozzles 8 of the descaling device 5 with a predetermined distance L, and the discharge holes are steel plates. 3 is inclined with respect to the longitudinal direction of the steel plate 3 at a twist angle (β) of 2 to 30 degrees so as to be symmetrical with respect to the center line CL in the width direction 3 and toward the outside in the width direction of the steel plate 3. When the drained water is sprayed uniformly and the discharge flow 7 is collided with the discharge flow 6 of the descaling water mixed with the scale, the collision flow 67 is applied to both ends of the steel plate 3 in a constant region (within L). This is because the fluid flows smoothly and is efficiently discharged from both side ends of the steel plate 3.
When the twist angle (β) exceeds 30 degrees, the collision energy with the discharge flow 6 of the descaling water particularly in the central region is insufficient, the scale floating effect becomes insufficient, and the scale discharge efficiency is reduced. It is insufficient. In addition, when the twist angle (β) is less than 2 degrees, the collision flow 67 with the descaling water mixed with the scale cannot be smoothly flowed to both side ends, and efficient from both side ends of the steel plate 3. Discharge becomes difficult.
[0021]
Further, the angle of attack (γ) of the discharge flow 6 from the plurality of high-pressure water injection nozzles 8 of the descaling device 5 and the discharge flow 7 of the plurality of low-pressure water injection nozzles 11 of the draining device 4 with respect to the steel sheet is 0 to 30 degrees, (Θ) is set to 2 to 60 degrees in order to ensure the collision force necessary for descaling and to apply descaling water and draining water on the steel plate 3. one Ensuring sufficient collision energy when colliding in a constant region (within L), activating floating of the scale removed (detached) by descaling, and further promoting the discharge of the collision flow mixed with this scale Because.
Thus, by disposing the plurality of high-pressure water injection nozzles 8 of the descaling device 5 and the plurality of low-pressure water injection nozzles 11 of the water draining device 4, the high-pressure water discharge flow 6 and the water draining device 4 of the descaling device 5 are arranged. The low-pressure water discharge flow 7 is collided in a certain region (within the range L) on the steel plate 3, and the scale removed by the descaling (peeling) is sufficiently floated by the collision flow 67. 3 can be effectively discharged from both ends.
At this time, since the discharge holes of the plurality of high-pressure water injection nozzles 8 of the descaling device 5 and the discharge holes of the low-pressure water injection nozzle 11 of the water draining device 4 face outward in the width direction of the steel plate 3, the collision flow 67 is It flows smoothly by the side edge of the steel plate 3 and is easily discharged.
[0022]
Further, since the collision flow of descaling water and draining water can be made uniform in a constant region (within L), partial supercooling and cooling unevenness are eliminated, and the width direction and length direction of the steel plate 3 are eliminated. The steel sheet 3 can be fed into the hot straightening machine 2 and can be hot straightened to obtain a steel plate 3 having a good shape without scale wrinkles.
FIG. 6 shows the temperature change in the length direction of the steel plate 3 obtained by hot straightening. When descaling and draining of descaling water are performed by the descaling method and equipment according to the present invention. Shows that a much more stable temperature distribution can be obtained as compared with the case where draining is not performed only by descaling.
[0023]
【Example】
[Example 1]
Examples of the descaling equipment for steel sheets according to the present invention will be described below.
In this example, the slab heated in the heating furnace in the example of the equipment arrangement shown in FIG. 1 is hot-rolled and finish-rolled to a steel plate 3 having a thickness of 30 mm and a width of 3000 mm. The steel plate 3 after descaling was introduced into the hot straightening machine 2 by the descaling equipment of the steel plate of the present invention consisting of the descaling device 5 and the draining device 4 as shown in FIG.
In the descaling device 5 in this embodiment, the twist angle α of the plurality of high-pressure water injection nozzles 8 disposed in the high-pressure water header 9 is set to 15 degrees, the injection angle γ of the high-pressure water injection nozzle 8 is set to 15 degrees, and the steel plate 3 The height h from the surface to the tip of the high-pressure water jet nozzle 8 was 120 mm. Descaling was performed by ejecting high pressure water of 14 MPa from each high pressure water injection nozzle 8 of the descaling apparatus 5 at a water amount of 28 liters / minute per nozzle.
[0024]
On the other hand, in the descaling water draining device 4, the low-pressure water header 10 provided with a plurality of low-pressure water injection nozzles 11 is arranged at a position whose center position is a distance L 2.3 m from the center position of the high-pressure water header 9. Then, the plurality of low-pressure water injection nozzles 11 are arranged so that the collision position with the steel plate surface of the drained water is a distance (distance between the collision points) Ls 1.6 m away from the collision position with the steel surface of the descaling water. Arranged. General industrial water was used as descaling water and draining water. The twist angle β of the plurality of low-pressure water injection nozzles 11 was 15 degrees, and the height h from the surface of the steel plate 3 to the tip of the low-pressure water injection nozzle 11 was 600 mm.
In this draining device 4, 0.5 MPa low-pressure water is sprayed from each low-pressure water spray nozzle 11 at a water amount of 76 to 110 liters / minute per nozzle and collided with the upper surface of the steel plate 3. The draining water is made to flow outward in the width direction of the steel sheet, and collides with the upper surface of the steel sheet 3 to the descaling water that has flowed outward in the width direction of the steel sheet. 1.6 m), colliding within a certain area, forcibly discharging this collision flow from both ends of the steel plate 3, draining the descaling water, and then introducing this steel plate 3 into the hot straightening machine 2 Corrected for a while.
[0025]
Regarding the steel sheet 3 after the hot straightening, the temperature distribution in the length direction and the width direction of the steel sheet is investigated, and at the stage when the temperature is lowered to room temperature, the surface properties and the surface layer structure are investigated, and the descaling and descaling water are detected. The draining effect was evaluated.
As a result, the temperature in the length direction and width direction of the steel sheet after hot straightening is in the range of ± 10 ° C, the non-uniformity of cooling due to descaling water (and draining water) is eliminated, and the surface layer structure is It was highly uniform and no deterioration factor of mechanical properties was observed. This means that the cooling by descaling water and draining water was highly uniform. Further, the shape of the steel plate 3 was good, no generation of scale wrinkles was observed, and the surface quality was good. This means that there was no residue remaining on the scale once removed by descaling.
[0026]
[Example 2]
In the case of Example 1, when the twist angles α and β of the high-pressure water injection nozzle 8 and the low-pressure water injection nozzle 11 are 5 degrees, the temperature in the length direction and the width direction of the steel sheet after hot correction is Within the range of ± 20 ° C., the non-uniformity of cooling due to descaling water (and draining water) was eliminated, the surface layer structure was generally uniform, and no factor of deterioration in mechanical properties was observed. This means that the cooling by descaling water and draining water was almost uniform.
Although the shape characteristics of the steel plate 3 were generally good, generation of scale wrinkles was observed although it was very slight. This is because the discharge of descaling water and draining water after descaling is somewhat unstable, and there is an adhesion residue of the scale once removed by descaling although it is very slight.
[0027]
[Comparative Example 1]
In the case of Example 1, when low-pressure water of 5 MPa is injected as draining water, the temperature in the length direction and width direction of the steel sheet after hot straightening is in the range of ± 15 ° C., and descaling water and draining are performed. Cooling with water became uniform, the uniformity of the surface layer structure was sufficient, and there was no cause for the deterioration of the mechanical properties. However, generation of scale wrinkles or peeling unevenness was observed, which was a problem in terms of quality. This is due to the fact that the descaling effect is reduced due to the excessive supply of drain water, and the removal (peeling) of the scale on the surface of the steel sheet becomes insufficient due to an increase in the accumulated water on the upper surface.
[Comparative Example 2]
In the case of Example 1, a plurality of low pressures are set such that the collision position with the steel sheet surface of drained water is a distance (distance between collision points) Ls 4.5 m from the collision position with the steel sheet surface of descaling water. When the water injection nozzle 11 is arranged, the temperature in the length direction and the width direction of the steel sheet after hot correction is in the range of ± 40 ° C., and the nonuniformity of cooling by the descaling water becomes remarkable, and the surface layer There was some concern about the homogeneity of the tissue, and there was a concern that it would be a factor of lowering mechanical properties. This is because the descaling water and draining water after descaling flowed in a long region, the discharge became unstable, and the cooling by the descaling water and draining water became non-uniform.
Moreover, the shape of the steel plate 3 was slightly unstable, and generation of scale wrinkles was recognized although it was slight. This is due to the fact that the colliding force of descaling water and draining water is reduced, the discharging power of the scale is not sufficient, and there is slight adhesion of scale on the steel plate surface.
[Comparative Example 3]
In the case of Example 1, when the descaling water draining device is not operated, the temperature in the length direction and the width direction of the steel sheet after hot correction is in the range of ± 60 ° C., and cooling with descaling water is performed. The non-uniformity of was remarkable. This is because the descaling water discharge after descaling is unstable, and the descaling water stays in a wide area on the steel plate in a non-uniform distribution.
Moreover, the shape of the steel plate 3 was somewhat unstable, and the occurrence of clear scale wrinkles was observed. This is due to the fact that the scale remains once removed by descaling.
[0028]
In addition, this invention is not limited to the content of said each Example. For example, regarding the arrangement conditions, descaling conditions, draining conditions, etc. of descaling equipment and draining equipment, the steel material to be rolled (especially the material), the size of the steel plate (especially the plate thickness), the rolling conditions (especially temperature), and the requirements for the steel plate Depending on the surface quality, shape, mechanical properties, etc. to be applied, there are variations within the scope of the above claims.
[0029]
【The invention's effect】
In the present invention, when performing descaling by high-pressure water injection on a steel sheet after hot rolling, the descaling water is drained simultaneously by low-pressure water injection within a certain region. By stably discharging the descaling water after it collides with the upper surface, preventing uneven cooling of the steel plate due to the descaling water, and promoting floating discharge of the scale removed (peeled) by descaling, scale As a result, the uniformity of cooling during controlled cooling can be secured, and the surface quality, shape and mechanical properties of the steel sheet can be secured stably.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a conceptual explanatory diagram showing an example of equipment arrangement for carrying out a method for producing a steel sheet according to the present invention.
FIG. 2 is a conceptual explanatory view showing an example of arrangement and an example of a draining state of the descaling device and draining device in FIG.
FIG. 3 is an explanatory diagram showing an example of nozzle arrangement in the descaling device and draining device in FIG. 2, a discharge state from the descaling water injection nozzle and the draining water injection nozzle, and an example of the shape of the discharge flow; Side explanatory view showing an example of discharge state of descaling water and drained water, (b) Figure is a back side explanatory view showing an example of discharge state of drain water, (c) Figure shows an example of discharge state of descaling water Back surface explanatory drawing and (d) figure are plane conceptual explanatory drawings which show the plane collision shape example with the thick steel plate of the discharge flow of descaling water and draining water in (a) figure-(c) figure.
FIG. 4 is an explanatory plan view showing an example of nozzle arrangement and an example of a discharge flow formation state in the descaling device and draining device in FIG. 2;
FIG. 5 is an explanatory side view of FIG. 4;
FIG. 6 illustrates temperature distribution in the direction of travel of a thick steel plate after hot straightening when descaling and draining of descaling water are performed, when only descaling is performed, and when descaling is not performed Figure.
FIG. 7 is an explanatory plan view showing an example of a descaled water retention state on a steel plate when only descaling is performed.
[Explanation of symbols]
1 Hot finishing mill 2 Hot straightening machine
3 Steel plate 4 Draining device
5 Descaling device 6 Descaling water discharge flow
7 Discharge water discharge flow 8 High pressure water injection nozzle
9 High pressure water header 10 Low pressure water header
11 Low pressure water injection nozzle

Claims (7)

  When producing steel sheets by hot rolling, the descaling applied when descaling by high-pressure water jet is applied to the steel sheets before or after the finish rolling mill or before or after the hot straightening machine. A descaling method for draining scaling and descaling water, wherein 3 to 20 MPa of descaling water is injected from a high-pressure water injection nozzle to collide with the steel plate, and on the upper surface side of the steel plate, the descaling water steel plate A 0.2 to 2 MPa drained water is injected from the low-pressure water injection nozzle onto the upper surface of the steel sheet separated by a distance of 500 to 4000 mm from the collision point with the upper surface, and the descaled water flow and drained water after the collision are applied to the upper surface of the steel sheet. The steel sheet descaling method is characterized in that the collision flow is forcedly discharged from both side edges of the upper surface of the steel sheet.   The descaling water and draining water are collided in the width direction of the steel sheet toward the outside by 2 to 30 degrees with respect to the traveling direction of the steel sheet. The steel sheet descaling method according to claim 1, wherein the steel plate is caused to collide. Descaling applied when descaling by high-pressure water jet on steel plate before or after finish rolling mill or before or after hot straightening machine when manufacturing steel sheet by hot rolling The descaling equipment is a descaling device having a plurality of high pressure water injection nozzles for injecting water at a pressure of 3 to 20 MPa and a plurality of low pressure water injections for injecting 0.2 to 2 MPa drained water. A draining device on the upper surface side of the steel plate provided with a nozzle, the nozzle of the descaling device and the nozzle of the draining device face each other in the plate passing direction, and the descaling device and the draining device are connected to the descaling water. distance between the collision point and the collision point and the draining water and the steel plate of the steel plate are arranged to be 500～4000Mm, opposition between the steel plate top surface from the draining device The flow of draining water after the flow of descaling water after collision with the steel plate top surface of the descaling device to the collision point between the draining water and the steel plate top surface from the collision point between the steel plate top surface of the descaling water The steel sheet descaling equipment is characterized in that the collision flow is stably discharged from both side edges of the upper surface of the steel sheet.   A plurality of high-pressure water injection nozzles of the descaling device form a discharge flow having an oval horizontal cross section at the collision point with the upper surface of the steel plate, and this discharge flow has the center line in the width direction of the steel plate as an axis of symmetry. It is arranged at an angle of 2 to 30 degrees (twisting angle) with respect to the traveling direction of the steel sheet so as to be line-symmetrical and directed outward in the width direction of the steel sheet. In order to form a discharge flow having an oval horizontal cross section at the point of collision with the steel plate, this discharge flow is symmetrical with respect to the width direction center line of the steel sheet and is directed to the outside in the width direction of the steel sheet. 4. The steel sheet descaling equipment according to claim 3, wherein the descaling equipment is disposed at an angle of 2 to 30 degrees (twisting angle) with respect to the traveling direction of the steel sheet.   The high pressure water injection nozzle of the descaling device is arranged at an angle of 0 to 30 degrees (injection angle) with respect to the vertical line, and the low pressure water injection nozzle of the water draining device arranged so as to face the high pressure water injection nozzle is In order to be able to form a colliding flow of descaling water and drained water, they are arranged at an angle of 2 to 60 degrees (injection angle) with respect to the vertical line. Descaling equipment for listed steel sheet.   The high pressure water injection of the descaling device is such that the injection area in the width direction of the steel plate of the drained water by the plurality of low pressure water injection nozzles is shorter than the injection area in the width direction of the steel plate of the descaling water by the plurality of high pressure water injection nozzles. The steel plate descaling equipment according to any one of claims 3 to 5, wherein a nozzle and a low-pressure water injection nozzle of a water draining device are disposed. The steel sheet descaling equipment according to any one of claims 3 to 6, wherein the equipment is disposed before or after the hot finish rolling mill, or after or before the hot straightening machine.

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