Method for reducing the indentation defect of foreign matters on the surface of hot-rolled strip steel

Abstract

This invention relates to the field of hot-rolled strip steel production technology, and proposes a method for reducing foreign object indentation defects on the surface of hot-rolled strip steel. The method includes: arranging purge water nozzles at the entrance of the downstream stand of a hot continuous rolling mill, with the nozzles forming an angle of 150-165° with the rolling horizontal line of the downstream stand, so that the purge water coverage area is located upstream of the looper on the entrance side of the downstream stand, thereby blowing away foreign objects that have detached from upstream from the strip's running area. This invention, by setting purge water nozzles with a specific angle and coverage area at the entrance of the downstream stand of the finishing mill, achieves precise control over blowing away foreign objects that have detached from upstream before they enter the rolling area, effectively cutting off the path of foreign objects entering the roll gap with the running strip, and significantly reducing the incidence of foreign object indentation defects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot-rolled strip production, and in particular to a method for reducing foreign matter indentation defects on the surface of hot-rolled strips. BACKGROUND

[0002] Foreign matter indentation is a common surface quality defect in conventional hot continuous rolling production. In the rolling process of a hot continuous rolling mill train, scaling is easily formed on the rolling mill equipment due to the influence of water vapor, smoke and high-temperature strip baking. As the service life of the equipment increases, rust also increases synchronously. These scaling and rusting matter falls on the surface of the strip and forms irregular pits after being rolled by the roll gap, which seriously affects the surface quality of the strip and may even cause a strip breakage accident in the subsequent pickling mill train. Especially during the head threading process of thin-gauge strips and high-strength steel, the impact vibration of the rack is larger, and scaling is more likely to fall off, so foreign matter indentation defects continue to occur frequently, seriously affecting the production organization of the production line.

[0003] In view of the above problems, the prior art discloses various schemes. For example, by upgrading the material of the guard plate, adding a blowing device, regular cleaning, optimizing the structure of the side guide plate and other measures, foreign matter indentation is controlled from different angles. However, the above schemes mainly focus on local improvement or a single means, and cannot systematically prevent and control the whole process of foreign matter generation, falling and entering the roll gap, especially lack of targeted measures for the problem of foreign matter falling from the upstream rack or equipment and entering the downstream rolling area with the strip.

[0004] Therefore, there is an urgent need for a method that can effectively remove the foreign matter falling from the upstream before entering the rolling area without increasing the cost of equipment modification. SUMMARY

[0005] In view of the lack of technical means for effectively removing the foreign matter falling from the upstream before entering the downstream rolling area in the prior art, the present application provides a method for reducing foreign matter indentation defects on the surface of hot-rolled strips, which comprises: A blowing water nozzle is arranged at the inlet of the downstream rack of the hot continuous rolling finishing mill train, the included angle between the blowing water nozzle and the rolling horizontal line of the downstream rack is 150-165°, and the blowing water coverage area is located upstream of the upstream side loop of the downstream rack, so as to blow the foreign matter falling from the upstream away from the strip running area.

[0006] In some embodiments, the number of blowing water nozzles arranged at the inlet of the downstream rack of the hot continuous rolling finishing mill train is 3, and the blowing water nozzles are arranged in sequence along the rolling direction.

[0007] In some embodiments, the jet angles of the three blowing water nozzles are adjusted so that the projections of the blowing water jets of adjacent nozzles on the rolling horizontal plane do not overlap each other, and the blowing water coverage areas of each blowing water nozzle are all located at a position upstream of the highest point of the upstream side loop of the downstream rack.

[0008] In some embodiments, the method further includes: adding a slag-receiving baffle between the baffle at the inlet of the finishing mill and the drive device, and setting a slag-receiving device behind both of them to collect the falling equipment scale.

[0009] In some embodiments, the slag receiving baffle is made of heat-resistant stainless steel and is installed at an angle between the baffle at the inlet of the finishing mill and the drive device, so that the falling scale slides down the slag receiving baffle into the slag receiving device.

[0010] In some embodiments, the slag receiving device is a detachable slag collection box.

[0011] In some embodiments, the method further includes: arranging compressed air purging nozzles at the outlet end of the inlet-side guide plate of the downstream stand, and controlling the opening and closing of the compressed air purging nozzles according to the bite signal of the finishing mill to remove foreign objects before they enter the roll gap.

[0012] In some embodiments, controlling the opening and closing of the compressed air purging nozzle based on the bite signal of the finishing mill includes: The purging process begins when the first downstream stand in the finishing mill equipped with the compressed air purging nozzle bites the steel and ends when the last stand in the finishing mill throws the steel.

[0013] In some embodiments, three compressed air purging nozzles are arranged on each side of the outlet end of the inlet-side guide plate of the downstream rack, and the purging flow rate of the compressed air is adjusted according to the strip specifications.

[0014] In some embodiments, the pressure range of the compressed air is 0.55~0.65MPa.

[0015] The method for reducing foreign object indentation defects on the surface of hot-rolled strip steel provided by this invention achieves precise control by setting up purging water nozzles with specific angles and coverage areas at the downstream stand entrance of the finishing mill. This effectively cuts off the path of foreign objects entering the roll gap with the strip, significantly reducing the incidence of foreign object indentation defects. Specifically, by arranging purging water nozzles at the downstream stand entrance of the hot continuous rolling mill and controlling the angle between them and the rolling horizontal line to be 150~165°, the purging water can impact the strip surface at the optimal angle, ensuring both purging force and preventing excessive temperature drop in the strip. By positioning the purging water coverage area upstream of the looper on the downstream stand entrance side, foreign objects that fall off upstream can be blown away from the strip running area before they reach the looper area with the strip, preventing them from accumulating at the looper or bouncing and falling back onto the strip surface. This effectively intercepts foreign objects before they enter the critical rolling area. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0017] Figure 1 The diagram shown illustrates an embodiment of the present invention, in which purge water nozzles are arranged at the inlet of the downstream stand of a hot strip mill finishing unit, wherein... Figure 1 (a) is a schematic diagram showing the relative position of the purge water nozzle to the inlet of the downstream frame and the spray direction of the purge water nozzle. Figure 1 (b) is a schematic diagram of the purge water nozzle; Figure 2 The diagram shown is a schematic of an embodiment of the present invention, in which a slag receiving baffle is added between the baffle at the entrance of the finishing mill and the drive device; Figure 3 The diagram shown illustrates a compressed air purging nozzle arranged at the outlet end of the inlet-side guide plate of the downstream rack, according to an embodiment of the present invention. Figure 3 (a) is a schematic diagram of the injection direction of the compressed air purging nozzle. Figure 3 (b) is a schematic diagram showing the relative positional relationship between the compressed air purging nozzle and the inlet side guide plate of the downstream frame.

[0018] Figure label: 101. Downstream frame inlet; 102. Purge water nozzle; 103. Purge water nozzle spray direction; 104. Inlet baffle; 105. Drive unit; 106. Slag receiving baffle; 107. Compressed air purging nozzle; 108. Inlet side guide plate; 109. Compressed air purging nozzle spray direction. Detailed Implementation

[0019] The following describes embodiments of the present invention. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms.

[0020] Furthermore, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements may include not only those elements but also elements not expressly listed or inherent to such process, method, article, or apparatus.

[0021] In the field of hot strip mill production, to facilitate accurate understanding of the technical solution of this invention, the relevant terms are first explained. Downstream stand of a finishing mill refers to the mill located at the rear of the rolling line in a multi-stand continuous finishing mill, typically referring to stands with a high incidence of foreign object indentation defects, such as stands F4 to F7. Rolling horizontal line refers to the reference horizontal plane formed by the strip running along the rolling direction during the rolling process. Entry-side looper refers to a looper device installed on the entry side of the finishing mill stand for adjusting strip tension and buffering speed fluctuations; it has a high point position. Upstream debris refers to foreign objects falling from equipment or areas at an earlier position relative to the current stand in the strip running direction. Strip running area refers to the spatial range traversed by the strip during the rolling process. Roll gap refers to the gap between the upper and lower work rolls, the area where the strip undergoes plastic deformation. Slag baffle refers to a plate-shaped component installed between equipment components to block and guide the falling of scale. Slag receiving device refers to a container or structure used to collect falling scale. The inlet side guide plate is a guiding device installed on the inlet side of the rolling mill to guide the strip steel into the rolling mill. The end of the strip steel closest to the rolling mill is called the outlet end.

[0022] One or more embodiments of the present invention will now be described with reference to the accompanying drawings.

[0023] Based on the above objectives, this invention proposes an embodiment of a method for reducing foreign object indentation defects on the surface of hot-rolled strip steel. Figure 1 The diagram shown is a schematic of a blow water nozzle arranged at the entrance of the downstream stand of a hot strip mill, according to an embodiment of the present invention. A method for reducing foreign object indentation defects on the surface of hot-rolled strip includes: arranging a blow water nozzle 102 at the entrance 101 of the downstream stand of the hot strip mill, wherein the angle between the blow water nozzle 102 and the rolling horizontal line of the downstream stand is 150-165°, so that the blow water coverage area is located upstream of the looper on the entrance side of the downstream stand, so as to blow foreign objects that fall off upstream away from the strip running area.

[0024] Specifically, the angle between the purging water nozzle 102 and the rolling horizontal line of the downstream stand is set to 150~165°. At this angle, the purging water can act on the strip surface with sufficient impact force to blow away foreign objects, without causing excessive drop in strip temperature or water mist interference with detection due to an excessively small angle. Figure 1 (a) shows the spray direction 103 of the purging water nozzle. By adjusting the spray direction 103 of the purging water nozzle, the purging water coverage area is located upstream of the looper on the inlet side of the downstream stand, meaning that the strip is purged before entering the looper. Thus, foreign objects falling off the upstream stand or equipment are blown away from the strip's running area before traveling with the strip to the looper area, preventing them from accumulating at the looper or bouncing and falling back onto the strip surface. This achieves the technical effect of removing foreign objects falling off upstream before they enter the downstream rolling area.

[0025] The aforementioned method for reducing foreign object indentation defects on the surface of hot-rolled strip steel achieves precise control by setting up purging water nozzles 102 with specific angles and coverage areas at the downstream stand entrance of the finishing mill. This effectively cuts off the path of foreign objects entering the roll gap with the strip, significantly reducing the incidence of foreign object indentation defects. Specifically, by arranging purging water nozzles 102 at the downstream stand entrance of the hot continuous rolling finishing mill and controlling their angle with the rolling horizontal line to be 150~165°, the purging water can impact the strip surface at the optimal angle, ensuring both purging force and preventing excessive strip temperature drop. By positioning the purging water coverage area upstream of the looper on the downstream stand entrance side, foreign objects falling from the upstream can be blown away from the strip running area before they reach the looper area, preventing them from accumulating at the looper or bouncing and falling back onto the strip surface. This effectively intercepts foreign objects before they enter the critical rolling area.

[0026] In some embodiments, the number of purging water nozzles 102 is optimized. Three purging water nozzles 102 are arranged at the inlet 101 of the downstream stand of the hot strip finishing mill, sequentially along the rolling direction. The arrangement of the three purging water nozzles 102 is consistent with the strip running direction, forming a continuous purging area along the rolling direction, effectively extending the purging time and improving the removal effect on upstream foreign matter.

[0027] In some embodiments, to further improve the purging effect and avoid mutual interference, the spray angles of the three purging water nozzles 102 are adjusted. By adjusting the spray angles of the three purging water nozzles, the projections of the purging water jets from adjacent nozzles on the rolling horizontal plane do not overlap, effectively preventing interference between the jets of adjacent nozzles and resulting in purging pressure loss, ensuring that each nozzle can maintain the purging force required by the design. Simultaneously, the purging water coverage area of ​​each purging water nozzle 102 is located slightly upstream of the highest point of the looper on the downstream stand inlet side. The highest point of the looper is the area where the strip is at its highest position. Setting the purging coverage area upstream of this position allows for the removal of foreign objects before the strip enters the highest point of the looper, preventing foreign objects from falling back onto the strip surface due to strip vibration at the highest point of the looper. For example, in actual adjustment, the angle of each nozzle can be gradually fine-tuned by observing the landing point of the purging water on the strip surface. Figure 1 As shown in (b), Figure 1 (b) is a schematic diagram of the purging water nozzles until the purging areas of the three nozzles are arranged in front of each other and do not overlap, and the purging area of ​​the nozzle closest to the loop is located just before the highest point of the loop.

[0028] As one specific embodiment, the present invention also includes measures to intercept the source of scale buildup in the equipment. For example... Figure 2As shown, a slag-receiving baffle 106 is added between the baffle 104 and the drive device 105 at the entrance of the finishing mill, and a slag-receiving device (not shown in the attached figure) is installed behind both to collect the scale deposits that fall onto the equipment. The baffle 104 at the entrance of the finishing mill typically refers to the protective baffle located at the very front of the finishing mill, used to guide the strip steel into the finishing rolling area. Its drive device 105 is generally a cylinder that drives the baffle to rise, fall, or swing. During long-term production, the surfaces of the entrance baffle 104 and its drive device 105 are prone to scale and corrosion due to high-temperature baking and water vapor erosion. These scale deposits are easily detached and fall onto the surface of the strip steel when the mill vibrates. By adding a slag-receiving baffle 106 between the two and installing a slag-receiving device behind it, when scale deposits fall from the surface of the baffle or cylinder, they are blocked by the slag-receiving baffle 106 and guided into the slag-receiving device for collection, thus preventing them from falling directly onto the strip steel running area. The slag-receiving device can be a detachable structure for easy periodic cleaning.

[0029] In some embodiments, the specific structure and material of the slag receiving baffle 106 are optimized. The slag receiving baffle 106 is made of heat-resistant stainless steel, such as 304 or 316L stainless steel. These materials have good high-temperature resistance and corrosion resistance, and can be used for a long time in the high-temperature and high-humidity rolling mill environment without easily rusting. The slag receiving baffle 106 is installed at an angle between the baffle 104 and the drive device 105 at the inlet of the finishing mill, so that the fallen scale can slide down the slag receiving baffle 106 into the slag receiving device. Even if the fallen scale can slide down the surface of the slag receiving baffle 106 into the slag receiving device under the action of gravity, it can avoid accumulating on the baffle and forming a secondary source of detachment.

[0030] According to several embodiments of the present invention, the slag receiving device is a detachable slag collection box, which is periodically cleaned using a high-pressure cleaner. The slag collection box is located below or at the end of the slag receiving baffle 106 to collect sliding scale. The slag collection box is designed with a detachable structure, such as using a slot-type or snap-on installation, for easy periodic removal and cleaning. During cleaning, the inside of the slag collection box is periodically flushed with a high-pressure cleaner to remove the collected scale before reinstallation. Depending on actual production conditions, cleaning can be scheduled during each scheduled maintenance or roll change. The cleaning cycle can be adjusted according to the frequency of foreign object indentation defects, for example, cleaning once a week or once after each certain tonnage production.

[0031] In other embodiments, the invention also includes measures for the final removal of residual foreign matter before it enters the roll gap. For example... Figure 3 As shown, Figure 3 The diagram shown illustrates a compressed air purging nozzle arranged at the outlet end of the inlet-side guide plate 108 of the downstream rack, according to an embodiment of the present invention. The compressed air purging nozzle 107 is arranged at the outlet end of the inlet-side guide plate 108 of the downstream rack, as shown... Figure 3(a) shows the injection direction 109 of the compressed air purging nozzle. Figure 3 (b) illustrates the relative position of the compressed air purging nozzle 107 and the inlet side guide plate 108 of the downstream stand. The outlet end of the inlet side guide plate 108 refers to the end near the mill roll gap, i.e., the position where the strip is about to enter the mill. Providing compressed air purging at this location allows foreign objects to be blown away from the strip surface at the last moment before entering the roll gap. Simultaneously, the opening and closing of the compressed air purging nozzle 107 is controlled according to the bite signal from the finishing mill, achieving synchronous control with the rolling process to remove foreign objects before they enter the roll gap. The bite signal is a detection signal generated when the strip head is bitten by the mill, typically provided by a hot metal detector or rolling force detection device at the mill inlet. Signal control ensures that purging is activated only when the strip passes through, avoiding ineffective consumption of compressed air and excessive cooling of the rolling zone.

[0032] According to several embodiments of the present invention, the opening and closing of the compressed air purging nozzles 107 are controlled based on the bite signal of the finishing mill, including: starting purging when the first downstream stand equipped with the compressed air purging nozzles 107 bites the steel, and closing purging when the last stand in the finishing mill throws the steel. For example, assuming that compressed air purging is arranged in stands F4 to F7, the control logic is as follows: when stand F4 detects the bite signal, all compressed air purging nozzles 107 from F4 to F7 are opened; when stand F7 throws the steel (the tail of the strip leaves the mill), all compressed air purging nozzles 107 are closed. This provides continuous purging protection throughout the entire process of the strip passing through the finishing mill, while avoiding energy waste when there is no steel.

[0033] In some embodiments, the number and adjustment method of the compressed air purging nozzles 107 are optimized. Three compressed air purging nozzles 107 are arranged on each side of the outlet end of the inlet guide plate 108 of the downstream frame, totaling six. This creates a uniform purging coverage along the width of the strip, preventing foreign matter from being ineffectively removed from both sides. Simultaneously, the purging flow rate of the compressed air is adjusted according to the strip specifications. For example, for wider strips, the nozzle opening can be appropriately increased to ensure effective edge purging; for thinner strips, the opening can be appropriately decreased to prevent strip vibration.

[0034] According to several embodiments of the present invention, the compressed air pressure ranges from 0.55 to 0.65 MPa, which provides sufficient purging force to remove foreign matter without causing excessive cooling of the strip surface or generating noise due to excessive pressure. Simultaneously, the compressed air pressure can be adjusted according to the strip specifications to minimize the temperature drop of the strip surface while removing foreign matter. For example, the pressure can be appropriately increased when rolling high-strength steel or thick strip, and appropriately decreased when rolling thin strip, to minimize the temperature drop of the strip surface while removing foreign matter, thus avoiding strip shape problems caused by uneven temperature.

[0035] In addition, this invention includes regular maintenance measures to ensure long-term stable performance. The purging water nozzle 102 and the compressed air purging nozzle 107 are regularly inspected and cleared to ensure they are not clogged and that the purging effect remains consistently stable. Inspections can be scheduled during each scheduled maintenance or roller replacement, such as weekly. If nozzle blockage is found, it can be cleared using a thin steel wire or by disassembling and cleaning. For the compressed air purging nozzle 107, the air pipe joints must also be checked for looseness and leaks to ensure stable air supply pressure.

[0036] To further illustrate the method of the present invention, the following specific embodiments provide further details.

[0037] Example 1 A hot rolling mill began implementing the technical solution of this invention in January 2025. The mill's finishing mill has a 7-stand layout, with stands F4, F5, F6, and F7 selected as downstream stands for modification. Three purging water nozzles 102 are arranged sequentially along the rolling direction at the inlet of each stand. The angles of the nozzles are adjusted to ensure that adjacent jets do not overlap, and the purging coverage area is located upstream of the looper's highest point. The angles between the nozzles and the rolling horizontal line are set to 150°, 155°, and 160°, respectively. A heat-resistant stainless steel slag-receiving baffle 106 is added between the baffle 104 at the inlet of the finishing mill and the cylinder of the drive device 105 (e.g., a cylinder), installed at a 45° angle. A removable slag collection box is installed behind the baffle 104 and the cylinder, and is cleaned periodically using a high-pressure cleaner. At the outlet end of the guide plate 108 on the inlet side of frames F6 and F7, three compressed air purging nozzles 107 are arranged on both the operation side and the transmission side. The opening is adjustable, the control pressure is 0.6MPa, and they are set to be interlocked with the steel bite signal: the purging is turned on when F4 bites steel, and the purging is turned off when F7 throws steel.

[0038] Statistics after implementation show that the average monthly number of foreign object indentation defects decreased from 60.2 rolls / month before implementation to 28.5 rolls / month, a reduction of 52.66%. Based on an average of 25 tons per roll, this reduces rework volume by approximately 800 tons per month, significantly improving product quality stability.

[0039] Example 2 On another production line, thin-gauge strip steel (thickness ≤ 3.0 mm) and high-strength steel products are mainly produced. When implementing the technical solution of this invention, parameters were optimized specifically for the characteristics of thin-gauge strip steel. The opening of the compressed air purging nozzle 107 was appropriately reduced to avoid strip head vibration or deviation from the rolling line due to excessive purging force. Simultaneously, the compressed air pressure was adjusted to 0.55 MPa according to the rolling rhythm, ensuring effective purging while reducing strip temperature drop. The purging water nozzle 102 uses a combination of 160°, 162°, and 165° angles to ensure the purging coverage area is located upstream of the looper. The cleaning cycle of the slag receiving device was appropriately shortened to address the increased scale shedding during high-strength steel rolling. Post-implementation statistics showed a significant reduction in foreign matter intrusion defects in both thin-gauge and high-strength steel products.

[0040] Example 3 As a simplified implementation, the technical solution of this invention is implemented only on downstream stands F5 and F6. Three purging water nozzles 102 are arranged at the inlet of stands F5 and F6, placing the purging area upstream of the looper. A slag receiving baffle 106 and a slag collection box are added between the baffle 104 and the cylinder at the inlet of the finishing mill. Three compressed air purging nozzles 107 are arranged on each side of the outlet end of the guide plate 108 at the inlet side of F5 and F6, interlocked with the F5 steel bite signal to open and closed during F6 steel ejection. Statistics after implementation show a significant reduction in foreign object intrusion defects compared to before the modification, indicating that the technical solution of this invention can achieve significant results even when implemented on only some stands, demonstrating the flexibility and applicability of the technical solution.

[0041] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0042] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0043] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0044] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel, characterized in that, include: A purging water nozzle is arranged at the entrance of the downstream stand of the hot strip mill. The angle between the purging water nozzle and the rolling horizontal line of the downstream stand is 150~165°, so that the purging water coverage area is located upstream of the looper on the entrance side of the downstream stand, so as to blow foreign objects that fall off upstream away from the strip running area.

2. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 1, characterized in that, The number of purging water nozzles arranged at the inlet of the downstream stand of the hot continuous rolling mill is three, and they are arranged sequentially along the rolling direction.

3. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 2, characterized in that, By adjusting the spray angle of the three purge water nozzles, the projections of the purge water jets from adjacent nozzles on the rolling horizontal plane do not overlap, and the purge water coverage area of ​​each purge water nozzle is located slightly upstream of the highest point of the looper on the downstream stand inlet side.

4. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 1, characterized in that, The method further includes: adding a slag-receiving baffle between the baffle at the inlet of the finishing mill and the drive device, and setting a slag-receiving device behind the two to collect the falling equipment scale.

5. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 4, characterized in that, The slag receiving baffle is made of heat-resistant stainless steel and is installed at an angle between the baffle at the inlet of the finishing mill and the drive device, so that the scale that falls off slides down the slag receiving baffle into the slag receiving device.

6. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 4, characterized in that, The slag receiving device is a detachable slag collection box.

7. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 1, characterized in that, The method further includes: arranging compressed air purging nozzles at the outlet end of the inlet-side guide plate of the downstream stand, and controlling the opening and closing of the compressed air purging nozzles according to the bite signal of the finishing mill to remove foreign objects before they enter the roll gap.

8. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 7, characterized in that, The step of controlling the opening and closing of the compressed air purging nozzles according to the bite signal of the finishing mill includes: The purging process begins when the first downstream stand in the finishing mill equipped with the compressed air purging nozzle bites the steel and ends when the last stand in the finishing mill throws the steel.

9. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 7, characterized in that, At the outlet end of the inlet side guide plate of the downstream frame, three compressed air purging nozzles are arranged on each side, and the purging flow rate of compressed air is adjusted according to the strip specifications.

10. The method for reducing foreign matter indentation defects on the surface of hot-rolled strip steel according to claim 7, characterized in that, The pressure range of the compressed air is 0.55~0.65MPa.

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