JP2005118838A - Apparatus and method for cooling of hot rolled steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for cooling of a hot rolled steel sheet which can secure uniformity of shape characteristics and material characteristics in the transverse direction of the steel sheet at a low cost and at ease by preventing over-cooling on both side edge portions of the steel sheet, when cooling the rolled steel sheet by jetting a coolant from multiple rows of spray nozzles arranged above onto the upper surface of the hot rolled steel sheet being conveyed. <P>SOLUTION: In both the side edge portions on the upper surface of the hot rolled steel sheet restrained between a plurality of restraining rolls, banks are arranged 10-300 mm apart to the width center side from the edge of each side, and coolant pools with agitated convection are formed while the coolant jetted from the spray nozzles is restrained from flowing out to the side edge portions. After cooling the steel sheet in the coolant pool, the coolant flows out transversely to the conveying direction from openings between the rear ends of the banks and the rear restraining roll and is discharged outside through the side edge portions of the steel sheet. Here, the above bank is formed by jet stream of the sprayed coolant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a cooling device for a steel plate obtained by hot rolling, and more specifically, a cooling device and a cooling method for a hot rolled steel plate applied to obtain a rolled steel plate having good shape characteristics and uniform material. It is about.

When manufacturing a steel sheet by hot rolling, the hot-rolled hot steel sheet is cooled for conveyance to the winding or pickling process or for material control. In addition, since it is important to ensure the shape characteristics (flatness), it is necessary to control the cooling so that the temperature distribution in the sheet width direction is uniform.
As a cooling device for performing such cooling control, for example, in Patent Document 1, a cooling water chamber is formed between a hot steel plate that runs on a conveyance line after rolling and a cover that is provided so as to surround the hot steel plate. Then, jet water flow is applied to the hot steel plate in the water of the cooling water chamber, high speed water flow is generated on the hot steel plate in the cooling water chamber to enable rapid cooling, and no discharge flow in the width direction is generated on the hot steel plate. Thus, there has been disclosed a system intended to form a discharge flow path due to overflow from the front and rear of the cooling water chamber on the upper surface of the cover to eliminate uniform cooling and enable uniform cooling.
However, since the cooling device of Patent Document 1 requires a cooling water chamber having a complicated structure, in addition to the problem that the equipment cost and the maintenance burden are large, the thick steel plate is uniformly cooled over the entire width. There is a problem that the edge portion is overcooled, warping and segregation of the structure are likely to occur, and it is difficult to obtain a uniform thick steel plate.
In addition, the spray nozzle is a slit nozzle and the spray flow is uniformly formed in the width direction, but there is a cover at the top of the cooling water chamber, so convection in the cooling water chamber is suppressed, so that sufficient cooling is achieved. There is also a problem that the efficiency cannot be obtained and the cooling cost increases such as an increase in the required water amount.
JP 58-86904 A

  In the case of cooling a hot-rolled steel sheet in which a plurality of rows of spray nozzles for injecting a cooling medium are arranged on the hot-rolled steel sheet being conveyed, The present invention provides a cooling apparatus and a cooling method for a hot-rolled steel sheet that can easily prevent the uniformity of the shape characteristics and material characteristics in the width direction of the rolled steel sheet at low cost.

The present invention is summarized as the following (1) to (6) in order to solve the above problems.
(1) The hot-rolled steel sheet being conveyed is constrained by a plurality of constraining rolls, and the hot-rolled steel sheet is cooled by spraying a refrigerant from a cooling device having a plurality of spray nozzles above the constraining rolls. A cooling device that suppresses the outflow of refrigerant to both end portions at both end portions on the upper surface of the hot rolled steel plate constrained between constraining rolls, at a position 10 to 300 mm away from the side end toward the center in the width direction. A cooling apparatus for hot-rolled steel sheets, wherein a weir is formed by forming a refrigerant reservoir and forming a refrigerant discharge channel between a rear end of the refrigerant reservoir and a constraining roll.
(2) In (1), the weir has a height that allows a part of the refrigerant to overflow from the refrigerant reservoir from the middle part to the rear side, and the refrigerant overflow rate gradually increases on the rear side. A cooling apparatus for hot-rolled steel sheets, characterized in that a discharge flow path is formed.
(3) The hot rolled steel sheet cooling device according to (1), wherein the weir is formed by a plurality of spray jets injected at an angle α toward the width center side.
(4) In any one of (1) to (3), the weir is displaceable symmetrically about the center line in the width direction of the hot-rolled steel sheet, and the hot distance is variable Cooling device for rolled steel sheet.

(5) The hot-rolled steel sheet being transported in the cooling zone of the hot-rolling line is used for the cooling device for hot-rolled steel sheets provided with a plurality of spray nozzles and weirs in any one of (1) to (4). It is arranged so that it can be cooled from the upper surface side, and discharge of the refrigerant injected from multiple spray nozzles from both ends of the hot-rolled steel sheet is suppressed by the weir to create a refrigerant reservoir, and the hot-rolled steel sheet is made efficient with this refrigerant reservoir A method for cooling a hot-rolled steel sheet, characterized in that it is cooled well and the refrigerant from the refrigerant reservoir is discharged outwardly from a discharge channel formed on the rear side of the weir via the side end of the hot-rolled steel sheet.
(6) In (5), the hot-rolled steel sheet cooling device having a weir formed by a plurality of spray nozzles and a plurality of spray jets in (3) or (4) is used as a cooling zone for a hot rolling line. The hot-rolled steel sheet being transported is arranged so as to be cooled from the upper surface side, and the amount of spray water in the weir formed by a plurality of spray jets is adjusted or ON / OFF to adjust the amount of refrigerant in the refrigerant reservoir. Cooling method for hot rolled steel sheet.

In the present invention, the jetting refrigerant from each spray nozzle is prevented from flowing out from both ends of the steel sheet by the weir or the jet weir, and the shape characteristics in the steel sheet width direction by overcooling the both ends of the steel sheet that is easily cooled and It is possible to prevent uneven material characteristics.
In addition, in the refrigerant reservoir where convection is active due to the refrigerant jet from each spray nozzle, the vapor film is made thin by breaking and diffusing with the pressure of the refrigerant gravity, so that the cooling efficiency can be improved and the cooling cost can be reduced. It is possible to make the change width of the temperature distribution in the width direction of the steel plate 3 after cooling to 10 to 30 ° C., and to homogenize the shape characteristics and material properties of the steel sheet.

The hot-rolled steel sheet cooling device of the present invention is, for example, as shown in FIG. 1, a hot-rolled steel sheet cooling device 1 disposed at a subsequent stage of the hot rolling machine 2, and the hot rolling machine 2 performs hot rolling. During the transfer of the high-temperature steel plate 3 having a surface temperature of 950 to 700 ° C., 700 ° C. to room temperature is injected by refrigerant (a cooling medium made of a fluid such as water, hereinafter referred to as “refrigerant”). It is particularly effective when applied to rapid cooling.
Below, the structural example of the cooling apparatus 1 of the hot rolled steel plate of this invention is demonstrated.
The hot-rolled steel sheet cooling device 1 of the present invention basically has a center in the width direction from the side edge to both side ends of the upper surface of the steel sheet 3 constrained between the constraining rolls 4a and 4b, as shown in FIG. The weirs 5a and 5b having a height h and a length L are disposed at positions (distance different depending on sheet thickness, sheet width, and rolling conditions) at a distance a (10 to 300 mm) on the side, respectively. It is configured to be able to cool while suppressing the outflow of the refrigerant to and preventing overcooling at both ends.

In addition, a refrigerant reservoir 6 is formed by the weirs 5a and 5b, the upper surface of the steel plate 3, and the restraining rolls 4a and 4b, and a full cone spray nozzle 7 in which, for example, a refrigerant collision surface 7f is arranged at an interval. Disposed at intervals, the refrigerant is sprayed from each full cone spray nozzle 7, this refrigerant jet flow is penetrated into the refrigerant reservoir 6 to create a convection zone, and by the action of pressure due to the weight of the refrigerant reservoir 6, Vapor film breakage and diffusion are promoted, and when the injected refrigerant passes through the refrigerant reservoir 6, the refrigerant in the refrigerant reservoir is entrained, and the amount of injected refrigerant is artificially increased to achieve cooling with high cooling efficiency. To do.
In this case, in order to ensure higher cooling efficiency, it is preferable to consider the conditions under which the refrigerant jet flow from each full cone spray nozzle 7 reaches the surface of the steel plate 3.
As shown in FIGS. 4A and 4B, the full conical spray nozzle 7 used here forms a full conical refrigerant jet 7a, and the refrigerant collision surface 7f with the upper surface of the steel plate 3 is circular. A nozzle 7 (hereinafter referred to as a “full cone spray nozzle”) that can disperse / splash the refrigerant over a wide range, and is connected to the header pipe 8.
In addition to the full cone spray nozzle, other spray nozzles such as a flat spray nozzle, an oblong spray nozzle, and an oval spray nozzle may be used.

A discharge flow path 9 for the refrigerant discharge flow 6o of the refrigerant reservoir 6 is formed between the rear ends of the weirs 5a and 5b and the rear restraint roll 4b. The discharge flow path 9 is 20 to 200 mm high in the refrigerant reservoir 6. In order to make it possible to form a convection zone of the (depth) h refrigerant, the refrigerant pool 6 is filled with the injected refrigerant, and excess refrigerant is allowed to overflow from the upper ends of the weirs 5a and 5b.
In this case, the refrigerant overflows from the upper ends of the discharge channel 9 and the weirs 5a and 5b, flows out to the side end of the steel plate 3, and is discharged outward. However, the shape characteristics and material characteristics of the steel plate 3 are reduced. In order to surely prevent the overcooling which inhibits, it is preferable that the steel plate 3 is rapidly cooled uniformly in the width direction in the refrigerant reservoir 6 and discharged to the side end portion of the steel plate 3 after the temperature is lowered.
For example, the weirs 5a and 5b are shaped so that the height of the upper end is inclined so that the height becomes lower on the rear side as shown in FIG. 5 so that the overflow rate of the refrigerant gradually increases from the upper end to the rear side. It is also effective to do.
It should be noted that although there is a slight gap between the lower end surfaces of the weirs 5a and 5b and the surface of the steel plate 3, there is no adverse effect even if the refrigerant leaks to some extent, but the gap is further reduced in order to reduce this refrigerant leakage. Since there is a concern that wrinkles occur on the surface of the steel plate 3 in contact with the surface of the steel plate 3, for example, a sealing material such as a non-combustible cloth, a wire brush, or a roller, or a seal substitute is interposed on the lower end surfaces of the weirs 5a and 5b. Consideration such as (hanging down) is also effective.

FIGS. 6-8 shows the other structural example of the cooling apparatus of the hot-rolled steel plate of this invention, and the jet weirs 11a and 11b using the spray jet 10a from the flat spray nozzle 10 are used as a weir. In the point which was used, it differs from the cooling apparatus of the hot rolled steel plate shown in FIGS.
In the cooling apparatus for hot-rolled steel sheets shown in FIGS. 2 to 5, since weirs 5 a and 5 b are used, a gap is formed between the weir and the restraining roll 4 a 4 b and between the weir and the upper surface of the steel sheet 3. As shown in FIG. 6 and FIG. 7A, a plurality of flat sprays arranged side by side in the conveying direction of the steel plate 3 as a weir are concerned. By using the jet weirs 11a and 11b using the spray jet 10a from the nozzle 10, these concerns can be eliminated.
Here, the flat spray nozzle 10 that forms the jet weir 11 is arranged so that the adjacent spray jet 10a interferes partially above the height (depth) h of the refrigerant reservoir 6 to thereby cause the spray jet 10a to interfer. It is easy to form the jet weirs 11a and 11b by uniform jets that can prevent the refrigerant in the refrigerant reservoir 6 from flowing out from the outside.

For example, as shown in FIGS. 8 (a) and 8 (b), the flat spray nozzle 10 forms a refrigerant jet flow 10 a having a substantially rectangular cross section via a divergent guide tube 10 k, and a refrigerant collision with the upper surface of the steel plate 3. The surface 7f is formed in a substantially rectangular shape, and means a nozzle 10 (hereinafter referred to as “flat nozzle”) that can disperse and collide the refrigerant in a wide range in one direction.
When the jet spray weirs 11a and 11b are formed by the flat spray nozzle 10, the longer diameter side of the jet flow 10a is set in the transport direction, and the adjacent jets 10a are arranged to interfere with each other. At both end portions of the upper surface of the steel plate 3 constrained between 4b, jet weirs 11a and 11b having a length L are formed at positions separated by a distance a (10 to 300 mm) from the side end toward the center in the width direction. The refrigerant reservoir 6 having a height (depth) h of 20 to 200 mm can be formed by suppressing the outflow of the refrigerant to both side ends of the gas, and the refrigerant reservoir 6 can efficiently prevent overcooling at both ends. It is configured so that it can be cooled.
In this case, as shown in FIG. 7B, the flat spray nozzle 10 is disposed with an angle α (preferably 0 to 45 degrees) inclined from the side end side of the steel plate 3 to the center side, and the spray jet 10a is arranged. The refrigerant flow from the jet weir 11 to the side edge of the steel plate 3 is caused to collide with the refrigerant jet flow 7a from the full cone spray nozzle 7 injected into the refrigerant reservoir 6 so as to push it back to the center side of the steel plate 3. While suppressing, a dam function can be strengthened and the convection of the injection refrigerant in the refrigerant reservoir 6 can be further activated.

Further, in the case where the jet weirs 11a and 11b are provided as the weirs, the refrigerant discharge amount from the refrigerant reservoir 6 can be adjusted (the refrigerant reservoir depth is adjusted) by adjusting the spray injection amount and the injection pressure. Is possible. Alternatively, it is possible to adjust the discharge amount of the refrigerant from the refrigerant reservoir 6 by ON / OFF of the spray injection.
Further, in this case, by allowing the spray injection amount and the injection pressure to be adjusted in the transport direction, it is possible to provide a gradient in the refrigerant discharge amount from the refrigerant reservoir 6 in the transport direction.
The weirs 5a and 5b or jet weirs 11a and 11b used in the present invention are arranged in a range of 10 to 300 mm from the side end of the steel plate 3 and suppress cooling of the side end portion of the steel plate 3. When the size (especially width) of the steel plate 3 is changed, it is necessary to change the arrangement position of the steel plate 3 in the width direction. Therefore, it is possible to displace symmetrically about the center line in the width direction of the steel plate 3 and to make the distance between the weirs variable. In addition, it is also considered that the cooling conical spray nozzle 7 for cooling can be displaced symmetrically about the center line in the width direction of the steel plate 3.

The above-described hot rolled steel sheet cooling device of the present invention is arranged such that the hot rolled steel sheet 3 being transferred to the cooling zone of the hot rolling line of the steel sheet as shown in FIG. The outflow from the both ends of the steel plate 3 of the sprayed refrigerant from the spray nozzle is suppressed by the weir (jet flow weir), thereby preventing the unevenness of the shape characteristics and material properties due to the overcooling of the both ends of the steel plate 3. it can.
Moreover, the refrigerant | coolant reservoir | reserver 6 in which convection is active is formed by the refrigerant | coolant jet from each spray nozzle 7, and a vapor | steam film is made thin by the pressure by a refrigerant | coolant gravity, and it destroys and spread | diffuses. When the refrigerant passes, the refrigerant in the refrigerant reservoir is entrained, and the amount of the injected refrigerant is increased in a pseudo manner to achieve cooling with high cooling efficiency.
Therefore, according to the present invention, the cooling efficiency can be increased to reduce the cooling cost, and the width of the temperature distribution in the width direction of the steel plate 3 after cooling can be set to 10 to 30 by increasing the uniformity of the width direction cooling of the steel plate. The shape characteristics and material characteristics of the steel plate 3 can be homogenized by setting the temperature to ° C.

For example, as shown in FIG. 1, a steel plate having a thickness of 30 mm, a width of 1300 mm and a surface temperature of 800 to 820 ° C. that is hot rolled by a hot finish rolling mill 2 is used. 3 is constrained between a plurality of constraining rolls 4a and 4b, and water is spray-injected as a coolant by using the hot-rolled steel sheet cooling device of the present invention having a structure as shown in FIGS. This is for cooling to 420 ° C.
Constraining rolls 4a in this embodiment 1, 4b are those whose diameter is disposed in the conveyance direction at a distance of 1000mm at 400 mm, at both ends of the steel plate 3 was arrested state between constraining rolls, the height The weirs 5a and 5b having a length h of 200 mm and a length L of 500 mm are arranged at a position 150 mm from the side edge of the steel plate 3, and the refrigerant reservoir 6 is formed on the steel plate 3 by the weirs and the restraining rolls 4a and 4b. Thus, the refrigerant discharge passage 9 was formed between the rear ends of the weirs 5a and 5b and the rear restraint roll 4b.

In the refrigerant reservoir 6, a plurality of full conical spray nozzles 7 for injecting water are arranged at a position 150 mm from the surface of the steel plate 3. From each filled cone spray nozzle 7, 0.02 m ³ / min of water was sprayed at a spray pressure of 0.3 MPa to cool the steel sheet to a target temperature of 400 to 420 ° C.
The cooled water from the refrigerant reservoir 6 collides with the restraining roll 4b that also has a draining function, and is discharged outwardly from the discharge channel 9 via both side ends of the steel plate 3. The cooling water overflowed from the upper end of the weir was joined to the cooling water discharge and discharged.
As a result of cooling the steel plate under the above conditions, the change width of the surface temperature distribution in the width direction of the steel plate 3 immediately after passing through the rear restraint roll 4b was about 20 ° C., and the shape characteristics were satisfactory without warping. It was.
Further, when a sample was collected and analyzed for texture, the uniformity of the surface structure was sufficiently satisfactory, and no reduction factor of mechanical properties was observed.
In the case where no weir is provided, the variation width of the surface temperature distribution in the width direction of the steel plate 3 is as high as 60 ° C., and the cooling uniformity may not be sufficiently ensured.

As shown in FIGS. 6 to 8, the second embodiment is different from the first embodiment in that instead of the weirs 5a and 5b, the spray jet 10a from the flat spray nozzle 10 is used as the jet weirs 11a and 11b. Is. Since others are generally common, description of common parts is omitted.
A plurality of flat spray nozzles 10 are arranged close to each other in the conveying direction at both ends of the steel plate 3 constrained between the restraining rolls, and the jet weirs 11a and 11b having a length L of 500 mm are collided with the spray jet 10a. Is arranged at a position 150 mm from the side edge of the steel plate 3, and a refrigerant reservoir 6 having a depth of 150 to 200 mm is formed on the steel plate 3 by the weirs and the restraining rolls 4a and 4b, and the jet weir 11a, Between the rear end of 11b and the restraining rolls 4a and 4b, a space (gap) without the spray jet 10a from the flat spray nozzle 10 or a discharge flow path 9 by a sparse jet was formed.
The flash plate nozzle 10 for forming the weir is inclined at an angle α (20 degrees) on the center side in the width direction of the steel plate 3, and the jet flow from this nozzle collides with the refrigerant reservoir to fill the full cone spray nozzle 7. The jet water flow is pushed back, and the jet water flow is arranged so as not to flow out to the side end portion of the steel plate 3. Each flat spray nozzle 10 was sprayed with 0.1 m ³ / min of water at a spray pressure of 0.3 MPa to form jet weirs 11a and 11b by spray jet 10a.

In the refrigerant reservoir 6, similarly to the first embodiment, a plurality of full cone spray nozzles 7 for injecting water are arranged at a position 150 mm from the surface of the steel plate 3. From each filled cone spray nozzle 7, 0.02 m ³ / min of water was sprayed at a spray pressure of 0.3 MPa to cool the steel sheet to a target temperature of 400 to 420 ° C.
The cooled water collided with the restraining roll 4b having a draining function and was discharged to the outside from the discharge flow path 9 via both end portions of the steel plate 3.
As a result of cooling the steel sheet under the above conditions, the change width of the surface temperature distribution in the width direction of the steel sheet 3 immediately after passing through the rear restraint roll 4b was about 15 ° C., and the shape characteristics were satisfactory without warping. It was.
Further, when a sample was collected and analyzed for texture, the uniformity of the surface structure was sufficiently satisfactory, and no reduction factor of mechanical properties was observed.

  In addition, this invention is not limited to said content. For example, the structure of the weir, the arrangement conditions, the type of each nozzle, the structure, the arrangement conditions, the refrigerant and its injection conditions, etc. are the steel plate conditions (material, size, temperature) to be cooled, Depending on the cooling conditions set in consideration of the mechanical properties and the like, there is a change within a range satisfying the above claims.

The conceptual explanatory drawing which shows the example of arrangement | positioning of the cooling apparatus of the hot rolled steel plate of this invention. Plan explanatory drawing of the cooling apparatus of the hot rolled steel plate of this invention. 1A is a side explanatory view of FIG. 1, and FIG. 1B is a partially cutaway front explanatory view of FIG. (A) The figure is a three-dimensional conceptual explanatory diagram showing an example of the shape of the full cone spray nozzle and the refrigerant jet used in the present invention, and (b) is the steel plate surface of the refrigerant jet injected from the full cone spray nozzle in (a) figure. The conceptual explanatory drawing which shows the example of a collision surface shape. Side surface explanatory drawing which shows the other example of a shape of the weir used by this invention. Plane | planar explanatory drawing which shows the other structural example of the cooling device of the hot rolled steel plate of this invention. (A) The figure is side explanatory drawing of FIG. 6, (b) The figure is a partially notched cross-sectional front explanatory drawing of FIG. (A) A figure is a front conceptual explanatory drawing which shows the flat spray nozzle and spray spray flow shape example which are used by this invention, (b) A figure is a side conceptual explanatory drawing of (a) figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooling apparatus of hot-rolled steel plate 2 Hot finish rolling mill 3 Steel plate 4a, 4b Restraining roll 5a, 5b Weir 6 Refrigerant reservoir 6o Discharge flow 7 Full cone spray nozzle 7a Spray jet 8 Header pipe 9 Discharge flow channel 10 Flat spray nozzle 10a spray jet 10k guide tube 11a, 11b jet weir

Claims (6)

  A cooling device that cools the hot-rolled steel sheet by injecting a refrigerant from a cooling device having a plurality of spray nozzles on the upper part between the constraining rolls by constraining the hot-rolled steel sheet being conveyed with a plurality of restraining rolls. In addition, the refrigerant is prevented from flowing out to both side end portions at the side edge portions of the upper surface of the hot-rolled steel plate restrained between the restraining rolls at positions 10 to 300 mm away from the side ends in the width direction center side. An apparatus for cooling a hot-rolled steel sheet, wherein a weir is formed and a weir is formed between a rear end of the refrigerant reservoir and a restraining roll to form a refrigerant discharge passage.   The weir has a height from which a part of the refrigerant can overflow from the refrigerant reservoir from the middle part to the rear side, and a refrigerant discharge passage is formed so that the refrigerant overflow rate gradually increases on the rear side. The apparatus for cooling a hot-rolled steel sheet according to claim 1.   The cooling device for a hot-rolled steel sheet according to claim 1, wherein the weir is formed by a plurality of spray jets injected at an angle α toward the width center side.   The weir is displaceable symmetrically about the center line in the width direction of the hot rolled steel sheet, and the distance between the weirs is variable, cooling the hot rolled steel sheet according to any one of claims 1 to 3 apparatus.   The hot-rolled steel sheet cooling device having a plurality of spray nozzles and weirs according to any one of claims 1 to 4 is placed in the cooling zone of the hot-rolling line, and the hot-rolled steel sheet being conveyed is viewed from the upper surface side. The refrigerant is arranged so as to be cooled, and the discharge of the sprayed refrigerant from a plurality of spray nozzles from both ends of the hot-rolled steel sheet is suppressed by a weir to create a refrigerant reservoir, and the hot-rolled steel sheet is cooled in this refrigerant reservoir, A method for cooling a hot-rolled steel sheet, wherein the refrigerant from the reservoir is discharged outwardly from a discharge passage formed on the rear side of the weir via a side end of the rolled steel sheet.   The hot-rolled steel sheet being transported to the cooling zone of the hot-rolling line with the cooling device for a hot-rolled steel sheet provided with a weir formed by a plurality of spray nozzles and a plurality of spray jets according to claim 3 or 4 The heat according to claim 5, wherein the heat is arranged to be cooled from the upper surface side, and the amount of water in the weir spray formed by a plurality of spray jets is adjusted or turned on / off to adjust the amount of refrigerant in the refrigerant reservoir. Cooling method for hot rolled steel sheet.

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