KR20170054601A

KR20170054601A - Slab processing appratus

Info

Publication number: KR20170054601A
Application number: KR1020150156463A
Authority: KR
Inventors: 박영선; 임승호; 김성연
Original assignee: 주식회사 포스코
Priority date: 2015-11-09
Filing date: 2015-11-09
Publication date: 2017-05-18
Also published as: KR101751280B1

Abstract

A slab processing apparatus is provided. According to an embodiment of the present invention, the slab processing apparatus comprises: a transfer line transferring a slab; a torch unit removing a detect by scarfing a surface layer of the transferred slab; a support unit supporting the torch unit; and an injection angle adjustment unit controlling a scarfing amount by adjusting an injection angle of the torch unit in accordance with a transfer speed of the slab.

Description

[0001] SLAB PROCESSING APPRATUS [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a casting apparatus capable of adjusting a scraping amount by controlling a spray angle of a torch unit according to a feeding speed of a cast steel, and capable of easily performing inspection and maintenance of the torch unit, .

Generally, the slabs produced in the continuous casting process have many surface defects such as pinholes, inclusions and micro cracks on the surface, and they are severe in high grade steel. Rolling of such a surface-defective cast steel in a rolling mill causes a failure such as a plate break or a defect in the produced hot-rolled coil. Therefore, the cast steel is subjected to scarfing work to remove defects by spalling the surface layer after continuous casting and then hot rolling.

The scarping operation is known as a method of removing defects by sputtering the surface layer (top surface, bottom edge, etc.) of the casting with a torch unit while transferring the casting from the run-out table.

However, when the continuous casting process, the scarifying process, and the hot rolling process are performed in-line, the feed rate of the cast steel may be changed according to the production rate of the cast steel. In a conventional cast steel processing apparatus, There is a problem in that it is difficult to realize uniform scatting as a whole because the injection of the torch unit is kept constant. Particularly, a cast steel having a relatively thin thickness (40 to 120 mm) is continuously produced in the casting process and the casting speed is changed in accordance with the operating conditions. Therefore, the casting speed of the cast steel varies, It has been difficult to control the amount of scrap depending on the conveying speed.

In addition, such a batch processing apparatus needs periodic inspection and maintenance of the torch unit. Since the torch unit is located on the transfer line of the main body, it is difficult to perform maintenance and maintenance, and there is a problem that the work must be stopped for maintenance and maintenance.

An embodiment of the present invention is to provide a billet processing apparatus capable of controlling the scatting amount in such a manner that the spraying angle of the torch unit is controlled in accordance with the feed rate of the cast steel.

The embodiment of the present invention is intended to provide a casting apparatus capable of easily performing inspection and maintenance of a torch unit.

According to an aspect of the present invention, there is provided a conveyance line for conveying a slab; A torch unit for removing defects by scarring the surface layer of the casting conveyed; A support unit for supporting the torch unit; And a spraying angle adjusting unit for controlling the scraping amount by adjusting the spraying angle of the torch unit according to the feeding speed of the casting jig.

Wherein the spray angle adjusting unit comprises a torch unit driving unit for operating at least one of the torch unit and the supporting unit to adjust a tilt of the torch unit to adjust the spray angle, And a controller.

The control unit may receive the feed information from at least one of the continuous casting machine, the feed line, and the feed detection unit to sense the feeding of the cast steel, and control the operation of the torch unit driving unit.

The spray angle adjusting unit may increase the spray angle when the feeding speed of the cast steel becomes faster and decrease the spray angle when the feeding speed of the cast steel becomes slower.

According to another aspect of the present invention, there is provided a conveying line for conveying a slab; And a scarifying device having a torch unit for scarifying the surface layer of the casting being conveyed to remove defects and a supporting unit for supporting the torch unit and capable of moving to a maintenance position on the side of the conveying line .

The support unit may include a first support unit and a second support unit that move in a direction intersecting with the feeding direction of the casting, respectively, wherein the torch unit includes a first torch unit installed in the first support unit, And a second torch unit installed in the second supporting unit.

The first torch unit and the second torch unit move in the lateral direction along the guide rails to work alternately while moving in mutual close contact with each other in order to perform continuous scarping.

The slab processing apparatus according to the embodiment of the present invention can adjust the scraping amount by adjusting the inclination angle of the torch unit according to the feeding speed of the cast steel to adjust the angle of spraying so that even when the feeding speed of the cast steel is changed, And the amount of scaping can be kept constant.

The slab processing apparatus according to the embodiment of the present invention can move the torch unit from the working position on the transfer line to the maintenance position on the side of the transfer line so that the inspection and maintenance can be easily performed.

The slab processing apparatus according to the embodiment of the present invention can work alternately between the two torch units and can realize continuous scaping while moving in mutual close contact state when the two torch units are alternated with each other. Thus, even if the tasks of the two torch units are alternated for inspection and maintenance, an uninterrupted scarping operation can be performed.

1 is a conceptual diagram of a slab processing apparatus according to an embodiment of the present invention.
Fig. 2 is a flowchart showing a casting method using the casting machine of Fig. 1. Fig.
3 is a conceptual diagram of a slab processing apparatus according to another embodiment of the present invention.
Fig. 4 is a flowchart showing a processing method of the cast steel using the cast steel processing apparatus of Fig. 3;
5 is a perspective view showing a scarfing apparatus of a slab processing apparatus according to an embodiment of the present invention.
6 is a side view showing a scarfing apparatus of a slab processing apparatus according to an embodiment of the present invention.
7 shows an example of moving the scarifying device of the slab treating apparatus according to the embodiment of the present invention to the maintenance position.
Fig. 8 shows another example of a scarfing apparatus of the slab treating apparatus according to the present invention, in which a plurality of torch units are alternately operated.
9 and 10 show an example of adjusting the spraying angle of the torch unit according to the feeding of the cast steel in the scarfing apparatus of the slab treating apparatus according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs, and the present invention is not limited thereto, but may be embodied in other forms. In order to clarify the present invention, it is possible to omit the parts of the drawings that are not related to the description, and the size of the components may be slightly exaggerated to facilitate understanding.

The cast steel described in the present invention refers to a material that is produced in a continuous casting machine and before final rolling (finish rolling). The concept of in-line is that the equipment such as continuous casting machine, reheating means, rough rolling mill, rolling mill, cooling means, winder, etc. are connected to the casting feed line (runout table) .

FIG. 1 is a conceptual view showing a method of producing a hot-rolled steel sheet by producing a cast steel S having a thick thickness S, that is, a steel strip S having a thickness of 120 to 500 mm, using the cast steel processing apparatus to which the present invention is applied. Fig. 2 is a flowchart showing a casting method using a casting machine. Fig.

As shown in the drawing, a casting method according to an embodiment of the present invention includes a casting preparation step S110 for producing a casting S in a continuous casting machine 10; A scarping step (S120) of scarfing the upper and lower regions of the slab (S) before the temperature of the slab (S) is cooled to less than 600 占 폚; A reheating step (S130) of charging the cast steel (S) into the reheating means (40) before the scarfed steel (S) is cooled to less than 600 占 폚 and heating it to a temperature higher than the recrystallization temperature; And a post-treatment step of post-treating the slab S.

The post-treatment step includes a rolling step (S140) of hot rolling the cast steel (S) to produce a steel sheet. Further, the slab processing method may include a detecting step (S150) of detecting surface defects in the upper and lower regions of the slab S before or after the scarping step (S120) and at a predetermined point thereafter.

The slab preparing step S110 is a step of producing a slab S used as a material for hot rolling and continuously producing a slab S having a thickness of 120 to 500 mm by using the continuous casting machine 10, (S) produced by using a torch cutting machine (TCM) 20 installed at the rear of the unit piece S having a weight of about 40 tons or less.

The continuous casting machine 10 is provided with a reheating means 40, a roughing mill 50, a rolling mill 70, a cooling means (not shown) for performing a reheating step S130 and a rolling step S140 by a transfer line 30 80 and the winder 90 in line.

The slab S cut by the slab cutter 20 is transferred to the reheating means 40 by being carried on a runout table constituting the transfer line 30 and the slab S to be conveyed is conveyed before the center portion temperature is cooled to less than 600 캜 The scarping step S120 proceeds.

The scarping step S120 scans the upper and lower regions of the cast slab S being conveyed by the scarping device 100 to remove upper and lower defects and edge defects of the slab S, To this end, it is preferable that the scarifying device 100 is installed on the transfer line 30 and the scarping of the upper and lower regions is performed during the transfer of the slab S. If scapping of the upper and lower surfaces of the cast steel S is performed, the defects of the hot-rolled steel sheet, which is the final product produced using the steel as the material, can be removed.

The reason for scapping the upper and lower regions of the slab S before the central portion temperature of the slab S is cooled to less than 600 ° C is to shorten the process of preheating the cooled slab S separately to a temperature at which scarfing is possible Or omitted to improve the process speed and to prevent cracks from growing due to cooling of the slab S and generation of new cracks.

The scarping step S120 is not limited to the transfer line 30 connecting the continuous casting machine 10 and the reheating means 40 inline as shown in Figs. 1 and 2, It may be varied in various embodiments if the central temperature can be achieved before it is cooled to below < RTI ID = 0.0 > 600 C. < / RTI > A stacking step S111 in which the slab S is cut off by the slab cutting machine 20 and is temporarily transferred to the yard where the slab S is being transported. The cast S temporarily queued in the yard can be moved to the conveying lines 30 and 31 again to perform scaping of the upper and lower regions. At this time, the screed S is conveyed to the conveying line 30 for connecting the continuous casting machine 10 and the reheating means 40 inline, while moving to the conveying line 31 provided separately from the continuous casting machine 10, Scarping can be performed.

The scalloped steel strip S can be immediately charged into the reheating means 40, but it is not limited to this, and it is possible to temporarily move to the yard. In case of temporarily waiting in the yard, it is necessary to heat the cast steel S so that the temperature of the center of the cast steel S is not cooled below 600 ° C.

When the scaping of the upper and lower regions of the slab S is performed before the center temperature of the slab S is cooled to less than 600 ° C, the time required for preheating the slab S to the scapable temperature can be shortened, (S) without surface defects can be produced because defects in the upper and lower surface regions and the right and left edge regions can be removed even in a high-temperature steel slab (S) such as a high alloy steel at a high temperature It becomes.

The scaping step S120 may include a detection step S150 for detecting surface defects in the upper and lower regions and the left and right edge regions of the cast S and the scaping step S120 may be performed in accordance with the detection result of the surface defects. The operation of the scarping device 100 can be controlled to control the scarping level of the top and bottom regions of the slab S,

The detection step S150 may be performed before the scarping step S120 to detect surface defects and then control the scarping step S120 correspondingly. Instead, as shown in Fig. 2, (S130), that is, at a predetermined point in the reheating step (S130) or the rolling step (S140). Therefore, when defects are detected in the intermediate cast steel product and the hot rolled steel product as a final product, the data can be fed back to be applied as a control factor in the production of the following cast steel and hot rolled steel. That is, the detecting step S150 may be performed before or after the scarping step S120, or may be performed in various steps. Of course, it is also possible to perform scaping on the upper and lower regions and the left and right edge regions of the cast S without performing the detection step S150 during the casting process.

The reheating step S130 is to heat the screed S to the reheating means 40 and to the recrystallization temperature or higher for hot rolling before the temperature of the central portion of the screped casting S is cooled to less than 600 占 폚. That is, the temperature of the slab S is raised to the recrystallization temperature of about 1250 ° C.

The rolling step S140 is a step of hot rolling the cast slab S to produce a hot rolled steel sheet (hot rolled coil) as a final product. The slab S is hot rolled to a desired thickness in the rolling mill 70, ). The cooled hot-rolled steel sheet is wound around a winder 90 to produce a hot-rolled coil. The rolling step S140 may be preceded by a rough rolling step (S141) in the roughing mill 50 to prevent excessive load generation in the rolling mill 70. [

Fig. 3 shows a casting apparatus for producing a hot-rolled steel sheet while continuously producing a relatively thin cast steel (S, 40 to 120 mm) in a mode different from that of the casting apparatus described above, and Fig. 4 shows a casting process using the same .

As shown in Figs. 3 and 4, the casting method includes a casting preparation step S210 for producing a casting S in the continuous casting machine 10; A reheating step (S230) of charging the cast steel (S) into the reheating means (40) and heating it to a temperature higher than the recrystallization temperature; A rolling step (S240) of hot-rolling the hot-rolled steel strip (S) at the rolling mill (70) to produce a steel sheet; The scarifying step S220 scans the surface layer of the slab S before the temperature of the slab S is cooled below the recrystallization temperature before or after the reheating step S230.

The cast slab preparation step (S210) produces the slab S in the continuous casting machine (10). Since the slab S having a thickness of about 40 to 120 mm produces the slab S at a high speed casting, it is possible to prevent the occurrence of minute cracks near the oscillation mark at the edge of the slab and the presence of inclusions, pinholes, Lt; / RTI > Such defects such as fine cracks may be oxidized by the atmosphere inside the reheating means 40 in the reheating step, and cracks may be further exacerbated. Therefore, the scarping step S220 is preferably performed before the reheating step S230 to remove cracks and other defects in advance.

The scarping step S220 scans the upper, lower surface area, and left and right edge areas of the cast slab S being conveyed to remove defects on the surface and the edge of the slab S, respectively. As in the above example, the scarping device 100 may be provided on the conveying line 30 for scaping the slab S being conveyed.

In the reheating step S230, the scrapped cast steel S is charged into the reheating means 40 and reheated, so that the temperature of the cast steel S, which has a thin thickness and is unevenly cooled, is uniformly maintained, Prevent defects. A tunnel-type tunnel furnace can be used as the reheating means 40, and the temperature distribution can be uniformly maintained while the slab S passes through this uniform furnace.

The rolling step S240 is a step of hot-rolling the slab S to produce a hot-rolled steel sheet (hot-rolled coil), which is a final product. Since the thin slab S has a relatively thin thickness, the rough rolling process may not be separately performed.

The slab processing method may include a detecting step (S250) of detecting a defect on the surface of the slab S before or after the scarping step S220, as shown in Fig. That is, after the casting preparation step S210, after the reheating step S230, and during the rolling step S240.

As in the example shown in FIG. 4, the scarping step S220 may be performed after the reheating step S230. The scarping step S220 performed at this time can remove all the cracks and defects generated and grown in the slab preparing step S210 and the reheating step S230 and therefore the scarping step S220 of the slab S entering the rolling step S240 Quality can be improved.

5 and 6 illustrate a scarfing apparatus 100 that is installed on a transfer line 30 to perform scaping of the surface of a slab S. As shown in the figure, the scarifying apparatus 100 is disposed above and below the slab S on the transfer line 30 so as to face the upper and lower surfaces of the slab S, respectively, A torch unit 110 for supporting the torch unit 110, a supporting unit 120 for supporting the torch unit 110, And a spray angle adjusting unit 130 for adjusting the spray angle of the torch unit 110 according to the feed speed of the slab S.

The scarping device 100 includes a collecting unit 140 installed to surround the four-sided region of the slab S and collecting slag scattered during the scarping operation, A defect detection unit (150) for detecting coordinates of a detection defect; A position detection unit (160) for detecting the position of the surface and the edge region of the steel strip (S); And a control unit (not shown) for controlling the operation of the torch unit 110 and the support unit 120 according to the results detected by the defect detection unit 150 and the position detection unit 160.

The torch unit 110 is disposed separately on upper and lower surface regions of the slab S, and each of the plurality of nozzles is connected to each other and extended in the width direction of the cast steel. The width of each of the upper and lower torch units 110 is set to be longer than the width of the slab S so as to enable scaping of the edge S of the slab S as well as the upper and lower surfaces of the slab S, A gas supply unit (not shown), which is controlled by a control unit, is connected to each nozzle 111 of each torch unit 110 to supply fuel gas.

The support unit 120 supports both the upper and lower portions of the cast steel S so that the two torch units 110 can be directed to upper and lower sides of the cast steel S, So that the torch unit 110 can be moved up and down according to the change of the condition. The support unit 120 is rotatably connected to the torch unit 110 by a rotation connection part 121 so as to adjust the spraying angle of the torch unit 110.

The upper and lower support units 120 are installed so as to be movable transversely to the guide rails 170 provided so as to extend in the lateral direction (the direction intersecting the feed direction of the main body). The support unit 120 and the torch unit 120 can move laterally along the guide rail 170 so as to be out of the working position (transfer line) when the inspection or maintenance of the torch unit 110 is required.

The collecting unit 140 collects slag scattering in a direction opposite to the slab conveying direction when the torch unit scans the upper and lower surface areas of the slab S to protect surrounding facilities. The collecting unit 140 includes a chamber part 141 surrounding the four-sided area or the to-be-searched area of the slab S and opening a surface facing the torch unit 110 to collect scattered slag therein; A spray nozzle (not shown) for spraying cooling water into the chamber part 141 to cool the sprayed slag; An exhaust part 143 for exhausting water vapor generated in the chamber part 141; And a discharge portion 145 for guiding the discharge of scattered slag and cooling water in the chamber portion 141.

The defect detection unit 150 detects defects in the upper and lower surface areas of the slab S being conveyed. The defect detecting unit 150 may be a camera for collecting image information on the surface of the slab S, or a magnetic sensor for collecting leaked magnetic field information by irradiating a magnetic field on the surface of the slab. The defect detection unit 150 can detect surface defect S of the cast S before the scarping operation as in the example of FIG. 5, but the present invention is not limited thereto and may be provided on the rear side of the scarping device 100, S) You can also check the surface condition.

The position detecting unit 160 detects the position of the surface and the left and right corner areas of the slip S being conveyed so that the torch unit 110 keeps a certain distance from the upper and lower surfaces of the slip S and moves right and left, So that the position can be determined. The position detecting unit 160 includes a laser sensor for irradiating the surface of the cast steel S with a laser and collecting the signal, an ultrasonic sensor for irradiating the surface of the cast steel with ultrasonic waves and collecting the signal, And a contact-type displacement sensor for collecting positional information of the sensor.

6, the spray angle adjusting unit 130 includes a torch unit driving unit 131 that adjusts the spray angles? 1 and? 2 in such a manner that the torch unit 110 is operated to adjust the inclination of the torch unit 110, And a control unit (not shown) for controlling the operation of the torch unit driving unit 131 on the basis of the conveyance information of the slab S.

6, 9, and 10, the torch unit driving unit 131 connects the back side of the torch unit 110 to the support unit 120 and connects the back side of the torch unit 110 to the torch unit 110 110 or a rotary device installed in the rotary connection part 121 of the support unit 120 and the torch unit 110. In this case, Although the present embodiment shows a mode in which the torch unit driving section 131 rotates the torch unit 110 to control the spray angles? 1 and? 2, at least one of the torch unit 110 and the supporting unit 120 So that the inclination angle is controlled by adjusting the tilt. 9 and 10, the spray angles? 1 and? 2 mean the internal angle between the spray direction of the fuel gas injected from the torch unit 110 and the top surface of the billet S, as shown in FIGS.

The control unit of the spray angle adjusting unit 130 is configured to detect the feed information S of the slab S from the continuous casting machine 10, the feed line 30, the feed detecting unit that senses the feed of the slab S, (In particular, the conveying speed) of the conveying unit 110 to control the operation of the torch unit driving unit 131 to adjust the spraying angle. Or to control the operation of the torch unit driving unit 131 so as to adjust the spray angle based on the thickness information of the slab S measured after scaping.

9, when the feed speed of the slab S is slow, the spray angle adjusting unit 130 adjusts the inclination of the torch unit 110 to reduce the spray angle? 1 to adjust the scraping amount As shown in FIG. 10, when the feed speed of the slab S is relatively high, the inclination angle of the torch unit 110 can be adjusted to increase the spray angle? 2 to adjust the scraping amount.

This is because, even if the feed rate of the cast steel S varies depending on the operating conditions, even if the feeding speed of the cast steel is changed, stable scuffing is realized by controlling the scuffing amount through the control of the spray angle and the scuffing amount is kept constant In order to make it possible.

In general, the control method of the scrapping amount is to control the feed rate of the cast steel and the feed flow rate of the fuel gas. However, since the feed rate of the cast steel is related to the productivity of the cast steel, There is a limit to use in scaping amount control due to the problem that scaping does not occur below a certain pressure.

However, if the scapping amount is adjusted by controlling the spray angles? 1 and? 2 as in the present embodiment, it is possible to control the scrap amount by controlling the injection angle? Even when the conveyance speed of the convenience is changed, a stable scarping operation can be performed by controlling the amount of scatting.

7 shows an example of moving the torch unit 110 from the working position A on the transfer line 30 to the maintenance position B on the side of the transfer line 30 for the inspection and maintenance of the torch unit 110 . The scarfing device 110 of the present embodiment requires that the support unit 120 supporting the torch unit 110 move laterally along the guide rail 170 Can be moved to the maintenance position (B) on the side of the transfer line (30), so that maintenance and maintenance can be performed easily.

8 shows another embodiment of the scarping device. The example of FIG. 8 shows a scarfing device having two torch units 110A, 110B that they can alternately work on or maintain. The scarfing device includes a first support unit 120A and a second support unit 120B which are installed on both sides of the guide rail 170 and move in a direction intersecting the conveying direction of the slab S, A first torch unit 110A provided on the first support unit 120A and a second torch unit 110B installed on the second support unit 120B. In other words, it operates two scarping devices that can work on both sides alternately.

Therefore, when the first torch unit 110A scatters at the working position A (on the transfer line), the second torch unit 110B can move to the maintenance position B1 and can perform maintenance, The first torch unit 110A can be moved to the opposite maintenance position B2 to perform the maintenance when the unit 110B performs the scaping operation in the work position A. [

In the example of FIG. 8, when the first torch unit 110A and the second torch unit 110B alternate with each other, they move in close contact with each other and can perform continuous scarping. That is, the first and second torch units 110A and 110B perform scarping together with the feed of the slab S even at the time of alternating the duty, so that continuous scaping can be performed. At this time, the torch unit deviating from the working position A stops supplying the fuel gas when the nozzles are out of the working position (scribe scarfing area), and the torch unit entering the working position A moves the nozzles to the working position It is possible to perform an uninterrupted scarping operation by starting the supply of the fuel gas.

10: Continuous casting machine, 30: Transfer line,
40: reheating means, 70: rolling mill,
80: cooling means, 90: winder,
100: Scarping device, 110: Torch unit,
120: support unit, 130:
131: torch unit driving unit, 140: collecting unit,
150: defect detection unit, 160: position detection unit,
170: guide rail.

Claims

A conveying line for conveying the slab;
A torch unit for removing defects by scarring the surface layer of the casting being transferred;
A support unit for supporting the torch unit; And
And a dispensing angle adjusting unit for adjusting the dispensing angle of the torch unit according to the feeding speed of the casting jig to control the scaling amount.

The method according to claim 1,
The spray angle adjuster
A torch unit driving unit for operating at least one of the torch unit and the supporting unit to adjust a tilt of the torch unit to adjust the spray angle;
And a control unit for controlling the operation of the torch unit driving unit on the basis of the feed information of the cast steel.

3. The method of claim 2,
Wherein the control unit controls the operation of the torch unit driving unit by receiving the feed information from the continuous casting machine, the feed line, and the feed detection unit for detecting the feed of the main feed.

The method according to claim 1,
Wherein the spray angle adjusting unit increases the spray angle when the feeding speed of the cast steel becomes faster and decreases the spray angle when the feeding speed of the cast steel becomes slower.

The method according to claim 1,
Wherein the support unit is movable along a guide rail in a lateral direction intersecting with a conveying direction of the casting.

6. The method of claim 5,
Wherein the support unit includes a first support unit and a second support unit provided on both sides of the guide rail,
Wherein the torch unit includes a first torch unit installed on a first support unit, and a second torch unit installed on the second support unit.

The method according to claim 6,
Wherein the first torch unit and the second torch unit move in a lateral direction along the guide rails to work alternately while moving in mutual close contact upon alternation of tasks to allow continuous scarping.

A conveying line for conveying the slab; And
And a scarifying device having a torch unit for scarifying the surface layer of the casting conveyed to remove defects and a supporting unit for supporting the torch unit and capable of moving to a maintenance position on the side of the conveying line.

9. The method of claim 8,
Wherein the support units each include a first support unit and a second support unit that move in a direction intersecting with a feeding direction of the casting,
Wherein the torch unit comprises a first torch unit mounted on a first support unit and a second torch unit mounted on the second support unit.

10. The method of claim 9,
Wherein the first torch unit and the second torch unit move in a lateral direction along the guide rails to work alternately while moving in mutual close contact upon alternation of tasks to allow continuous scarping.