JPS6340604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing scale attached to the surface of a hot rolled steel sheet.

Scale is generated and adhered to the surface of a hot rolled steel plate, and such scale is removed before cold rolling the steel plate. Conventionally, as a general-purpose method for removing scale, the steel strip is passed through a pickling tank filled with hydrochloric acid or sulfuric acid, and the scale is removed by a chemical reaction between the scale and the acid. A pickling method is used. However, in this method, scale removal is mainly carried out through chemical reactions, and the descaling efficiency is solely controlled by the chemical reaction rate. Therefore, in order to ensure a certain degree of descaling efficiency, a heating device is used to increase the reaction rate. It requires a large burden on equipment, such as speeding up the pickling process or making the pickling tank longer. Especially when hot rolling is performed at high temperature (630℃)
(above)), a large amount of scales of magnetite (Fe ₃ O ₄ ) and hematite (Fe ₂ O ₃ ), which are difficult to react with acids, are generated, and for this reason, the time required for immersion in acid is usually only about 30 seconds. However, it takes 2 to 5 minutes, and the pickling tank must necessarily be made longer. In addition, in the pickling method, in order to prevent strips from accumulating in the pickling tank when the line is stopped, strip storage devices must be installed on the inlet and outlet sides of the line. It is also necessary to install equipment to treat waste acid. In this way, the pickling method requires longer lines and the installation of auxiliary equipment to ensure descaling efficiency, as well as the installation of ancillary equipment such as strip stockpiling equipment and waste acid processing equipment. As a series of process lines, it becomes extremely large, and there are major problems in terms of equipment costs and operating costs.In particular, it requires a large space for installation, so This is by no means suitable as a descaling facility based on the continuous process of scaling and cold rolling.

On the other hand, recently, liquid honing, which uses iron sand, slurry, etc. as an abrasive, has been put into practical use as ^a descaling method instead of pickling. Since the cleaning agent is injected onto the strip surface, the power efficiency is extremely low, and since it requires a large amount of power to generate the above-mentioned high pressure and a nozzle that can withstand ultra-high pressure, the equipment and operating costs are by no means cheap. In addition, there is a problem in that the sprayed abrasive remains on the surface of the steel strip, which adversely affects the quality of the product in the subsequent plating step.

The present invention was devised in view of the problems of the conventional method as described above, and is a descaling method that can reliably remove scale from hot rolled steel sheets at low cost and without using large-scale equipment. The purpose is to provide a method.

In the present invention, in the descaling process of a hot rolled steel plate following hot rolling, the scale on the surface of the steel plate is crushed by rolling the hot rolled steel plate while supplying a slurry-like abrasive to a roll bite, and then the scale on the surface of the steel plate is crushed. The scale is removed from the surface of the steel plate by cleaning the scale with a surface polishing device. As described above, the present invention is characterized in that the scale is actively crushed by rolling while supplying an abrasive, and descaling is carried out by removing this with the abrasive cleaning agent. , it becomes possible to reliably remove scale with compact equipment, and it also becomes possible to easily integrate it with the cold rolling process.

Figures 1 and 2 show an example of the descaling equipment used in the implementation of the present invention and the descaling situation using the equipment. 1 is a strip, 2 is a scale layer on the surface of the strip, and 3 is a slurry-like Abrasive agent, 4 is fine particles contained in the abrasive agent 3, 5 is a rolling mill for descaling, 6, 6 are rolling rolls, 7 is the abrasive agent 3 on the roll bite of the rolling rolls 6, 6
This is a nozzle for supplying. Reference numeral 8 denotes a surface polishing device for polishing and removing crushed scale, and in this embodiment, it is constructed as a brush roll 9. 10, 10 are nozzles provided before and after each brush roll 9;
The water supplied from 10 cools the contact surface of the strip 1 with the brush roll 9, and at the same time washes away the scale that has been washed away. Also, 11 is the backup roll of brush roll 9,
12 is a rewind reel, 13 is a bridle roll,
14 is a rinse tank, 15 is a rinse header, 1
6 is a ring roll, 17 is a dryer, and 18 is a winding reel. Furthermore, 19 is a pumping device for collected slurry, 20 is a slurry tank, and 21
2 is an agitator for stirring the slurry, and 22 is a pump. In this embodiment, the abrasive agent 3 supplied to the roll bite is collected in the separating device 19 and reused, and the fine particles of scale that have been crushed and polished are is also made into a slurry and collected by the separating device 19, and this is also supplied to the roll bit as part of the abrasive.

According to this equipment, the strip 1 unwound from the unwinding reel 12 is sent to the rolling mill 5 via the bridle roll 13, where a slurry-like material is applied to the roll bite of the rolling rolls 6, 6 as shown in FIG. Rolling is performed while the abrasive 3 is being supplied. By this rolling, the scale layer 2 on the surface of the strip 1 is actively crushed by the fine particles 4 in the slurry that are pressed against the surface of the scale layer 2 by the rolling force of the rolls 6, 6, and the scale layer 2 is peeled off from the surface of the strip 1 or is easily crushed. It becomes a state where it can be peeled off. The strip 1 then passes through a bridle roll 13 to a surface polishing device 8.
The surface is then polished by a brush roll 9. The scale on the surface of the strip is completely removed by such cleaning, and the removed scale is washed away from the surface of the strip 1 by water supplied from the nozzles 10, 10.

In the present invention, the strain rate given to the strip 1 by the rolling rolls 6, 6 varies somewhat depending on the particle size of the fine particles in the abrasive, but is as shown in FIG. Generally speaking, 6% to 15% is appropriate; if it is less than 6%, sufficient scale crushing effect cannot be obtained, and if it is more than 15%, the rolling capacity becomes too high, requiring a large amount of power and grinding. Fine particles in the agent and scale itself once crushed become embedded in the strip metal, making subsequent cleaning difficult.

Further, as the surface polishing device 8, a polishing roll or the like may be employed in addition to the brush roll 9 described above, or a combination of this and a brush roll may be employed. As the surface polishing device, other appropriate devices such as liquid honing can be used. In addition, the brush roll 9 described above is preferably made of metal wire or nylon containing an abrasive agent in order to improve its cleaning performance, and the wire diameter of the brush is approximately 0.15 to 0.30 mm. is preferred. This is because if the brush wire diameter is less than 0.15 mm, the cleaning performance is poor, and if it exceeds 0.30 mm, the power consumption during brushing becomes too large and the strip metal is worn out. Furthermore, the amount of reduction of the brush roll should be controlled within the range of approximately 0.3 to 3.0 mm. This is because the brush may buckle, resulting in increased wear and tear on the brush, as well as a decrease in polishing ability and an increase in power consumption. When the polishing roll is used, the surface material of the polishing roll is preferably an abrasive-containing nonwoven fabric or the like in order to improve the contact performance with the strip.

Furthermore, in a preferred embodiment of the present invention, prior to rolling by the rolling rolls 6, 6,
Hot-rolled steel sheets are rapidly cooled, or in some cases are cooled quickly after heat retention.This makes the scale more likely to be crushed, making subsequent crushing and polishing more reliable. . Furthermore, by performing pickling over a relatively short range after cleaning, descaling performance can be made more reliable.

In addition, in the above embodiment, the rolling roll 6,
Although the number of passes by No. 6 and the number of passes by the brush roll and polishing roll are not particularly limited, it is more effective to perform multiple passes under light pressure within the above ranges of the amount of distortion and amount of reduction.

In addition, as the fine particles constituting the slurry-like abrasive supplied to the roll bite, appropriate hard fine particles such as sintered bodies of alumina or silica, hydrocarbons, glass powder, iron sand, etc. can be adopted. It is appropriate that the diameter is about 10μ to 500μ. Furthermore, the slurry concentration of the abrasive is 20% by volume.
It is preferable to set the amount to about 80%. If it is less than 20%, there will be little effect when supplied to the roll bite, while if it exceeds 80%, it will be almost impossible to force feed it to the nozzle. FIG. 4 shows the relationship between the particle size of the fine particles constituting the slurry-like abrasive and the resulting descaling rate after rolling. 50%) and was rolled at a reduction ratio of 8%.

FIG. 5 shows an embodiment of a process line in which descaling equipment and cold rolling equipment are connected to each other for implementing the present invention described above, in which 23 is an unwinding reel, 24 is a welder, and 25 is a welder. 2 is a side trimmer, 26 is a strip accumulator, 27 is a bridle roll, A is a descaling equipment used for carrying out the method of the present invention, 28 is a ringer roll, 2
9 is a tandem rolling mill, 30 is a flying shear,
31 is a take-up reel. As described above, according to the method of the present invention, it can be carried out using extremely compact equipment, and therefore, it can be easily integrated with the cold rolling process.

According to the descaling method of the present invention described above,
It is possible to descale hot rolled steel sheets at low cost and reliably without requiring huge equipment or many auxiliary or incidental equipment as in the past. It can be said that this method is extremely suitable as a descaling method based on the premise of continuous process.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of descaling equipment used in carrying out the present invention. FIG. 2 is an explanatory diagram showing the implementation status of the present invention using the equipment shown in FIG. FIG. 3 shows the relationship between the reduction ratio of the rolling rolls and the descaling ratio after rolling.
FIG. 4 shows the relationship between the particle size of the fine particles of the abrasive and the descaling rate after rolling. Figure 5 is the first
It is an explanatory view showing a continuous process line of descaling equipment and cold rolling equipment shown in the figure. In the figure, 1 is a strip, 2 is a scale layer, 3 is an abrasive agent, 6 is a rolling roll, and 8 is a surface polishing device.

Claims (1)

[Claims] 1. Scale on the surface of the steel plate is crushed by rolling a hot-rolled steel plate while supplying a slurry-like abrasive to a roll bite, and then the crushed scale is polished and cleaned using a surface polishing device. 1. A method for descaling a hot rolled steel sheet. 2. The method for descaling a hot rolled steel sheet according to claim 1, wherein the scale is polished and removed using a rotating brush roll. 3. The method for descaling a hot rolled steel sheet according to claim 1, wherein the scale is polished and removed using a rotating polishing roll.