JPS6316207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wet blast descaling method for steel plates.

Recently, a mechanical descaling method (hereinafter referred to as a wet blast descaling method) in which a slurry containing iron sand particles is blasted under high pressure has been developed, and has been applied, for example, to remove scale from hot rolled steel strips. Conventionally, in wet blast descaling equipment, there was no device to adjust high pressure water pressure in the width direction of the board.
Therefore, the high pressure water pressure in the width direction of the header is all constant. On the other hand, the thickness and composition of the oxide film in the width direction of the original sheet passed through the descaling equipment may vary depending on the manufacturing conditions in the previous process, the conditions of the coil before being passed through the descaling equipment, etc. It's not the same either. If such a metal plate with different oxide film conditions in the width direction is processed using wet blast descaling equipment that maintains a constant high water pressure in the width direction, uneven descaling in the width direction will naturally occur. .

Conventionally, in order to prevent this unevenness, it was necessary to apply high water pressure to the entire header according to the part with the worst descaling condition, and as a result, the part that is easily descaled in the width direction becomes over-descaled. As a result, losses are inevitable in terms of yield due to pump motor power and over-descaling of the threaded material.

In general, the descaling property of the oxide film on a steel sheet after hot rolling is the best at both ends, followed by the center, and the remaining 50 to 150
The mm-wide portion tends to have the worst descaling properties. This situation is shown in Figure 1.

In the figure, descaling performance worsens in the order of 1, 2, and 3. When descaling such materials, the pressure of high-pressure water is conventionally set according to the descaling status of the 3 parts with the worst descaling properties, so in the 1 and 2 parts, there is no possibility of over-descaling. There are problems such as effective use of the electric power of the drive motor of the high-pressure pump, a decrease in the threading yield due to grinding of one or two sections of the base metal, and a decline in the quality of the finished product due to sand being eaten into the base metal.

On the other hand, descaling by the conventional pickling method is chemical descaling using acid, and when descaling is completed, the bare steel is exposed, but an inhibitor is added to the pickling solution, which prevents the bare steel from being removed. The acid corrosion of the base iron does not proceed on the surface, and only the scale dissolves and peels off, so there is no problem as described above.

FIG. 2 is a schematic diagram of a nozzle header section when conventional width direction high pressure water pressure control is not performed, and FIG. 3 is a view taken along the line aa in FIG. 2. In the figure, high pressure water is 1
The high-pressure water enters the high-pressure water chamber 2 and is distributed to each nozzle 3 through high-pressure water holes. In FIG. 3, high-pressure water from the nozzle 3 enters a high-pressure water jet hole 5 provided at the tip of the nozzle 3 through a high-pressure water hole 4 and is jetted. The iron sand slurry enters through the introduction pipe 6 and flows out through the center of the nozzle.

The pressure of high-pressure water 1 flowing into the header is controlled according to the line speed and width of the plate, but since it is commonly guided to each nozzle inside the header, the pressure cannot be changed in the width direction. In other words, in wet blast descaling equipment that accelerates the abrasive material with high-pressure water and projects it onto the metal material to remove the surface oxide film, the descaling ability has conventionally depended on the pressure of the high-pressure water. Scaling capability is achieved by high pressure water pressure changes.

The conventional high-pressure water pressure change is not performed individually for the width direction nozzles in one header, so it is difficult to deal with descaling unevenness due to oxide film remaining in the width direction of the metal plate. It was out of control.

In order to solve these problems, the present invention aims to control the high pressure water pressure in the width direction of the metal plate in accordance with the descaling state of the metal plate.

That is, the present invention improves the descaling performance in the width direction of the header in order to eliminate uneven descaling in the width direction caused by differences in the thickness of the oxide film in the width direction and differences in the structure of the oxide film that occur during the manufacturing process of the metal plate. It is characterized by making adjustments.

FIG. 4 is an explanatory diagram of one embodiment of the present invention. Based on Figure 1 showing the descaling pattern of the oxide film on the surface of the metal plate, the high-pressure water chamber 2 is divided into blocks so that high-pressure water pressure can be controlled in the width direction of the plate, and high-pressure water is supplied to each block from a separate system. Let me guide you.
Each system has a pressure control function using pressure regulating valves, etc.

In Figure 4, the high-pressure water chamber 2 has partition walls a, b, c, and d.
It is separated into , , , chambers. According to the descaling pattern of the oxide film, by showing almost the same descaling property as , these are connected and eventually become i,
It is divided into three blocks (B and C), and pressure regulating valves A, B, and C are installed in each block, so that high-pressure water pressure can be adjusted individually according to the descaling situation of the strip in the width direction. 2-3 shows the flow path to the high pressure water nozzle.

In order to perform more precise control, it is also possible to increase the number of divisions of the high-pressure water chamber 2 and to perform pressure control for each divided small chamber without connecting it to the high-pressure water chamber. In addition to controlling the opening of the control valve, the pressure can also be controlled by providing a high-pressure pump for each block and controlling its rotation speed.

Pressure control for each block involves manual intervention by the operator to increase or decrease the high-pressure water pressure, depending on the surface finish of the plate after descaling, which is determined by the line speed and the pressure determined by the plate width. It is also possible to automatically control the pressure in the width direction and longitudinal direction based on the residual scale detector signal on the plate surface after descaling.

Other embodiments of the present invention include a method (1) of inserting a metal cylinder with partition walls at both ends as shown in FIG. be. In Figure 5 1,
,, indicates the divided metal cylinder 2-1,
This is shown to be sequentially pushed into the high pressure water chamber 2 of FIG. 1 from the end. Further, FIG. 5 2 shows a structure in which a plurality of high pressure water chambers 2-2 are arranged and integrated.

It should be noted that, in anticipation of the fact that most types of steel plates to be descaled have a descaling difficulty distribution in the width direction as shown in Fig. 1, for example, the descaling difficulty is The nozzles in the areas with poor performance should have a large capacity such as flow rate.

That is, it is known that the descaling ability can be changed not only by changing the high water pressure but also by changing the flow rate of the slurry applied as the abrasive material or the concentration of the slurry. This is a phenomenon in which the descaling efficiency changes depending on the amount of abrasive used. Utilizing this fact, it is possible to use a method of changing the slurry flow rate or slurry concentration in the width direction, instead of using the above-described method of changing the high water pressure in the width direction of the steel plate. Changing the slurry flow rate and concentration is less effective than changing the high water pressure.

In other words, with the method of changing high water pressure, it is possible to save the power required for descaling by preventing over-descaling, whereas with the method of changing the slurry flow rate or concentration, it is possible to save the power required for descaling by preventing over-descaling. This is because although it is possible to prevent product quality degradation due to sheet threading yield loss and descaling unevenness, it is not possible to save the descaling power consumed by the high-pressure water that is projected regardless of the flow rate or concentration of the slurry.

However, compared to changing the pressure of high-pressure water, changing the flow rate and concentration of the slurry has the advantage that it can be done relatively easily because it deals with a low-pressure system.

Figure 6 shows an example of a device that changes the slurry flow rate.
FIG. 7 shows an example of an apparatus for changing the slurry concentration. In FIG. 6, reference numerals 1 to 3 indicate throttle valves for changing the flow rate of slurry, and reference numerals 4 to 10 indicate injection nozzles. The throttle valve for each block of each nozzle is adjusted depending on the scale distribution of the steel plate or the properties of the steel plate after descaling. The above-mentioned object can be achieved by a device that can change the flow rate of the slurry in the width direction.

In Fig. 7, 1 to 3 are throttle valves for changing the makeup water concentration, 4 to 6 are slurry supply systems, and 7 to
9 is a slurry tank, 10 to 12 are slurry agitators, and 4 to 10 are nozzles. The throttle valve for each block of each nozzle is adjusted depending on the scale distribution of the steel plate or the properties of the steel plate after descaling, but the adjustment of this throttle valve changes the amount of replenishment water, and therefore the degree of dilution of the slurry in the slurry tank. This changes the slurry concentration and allows the descaling ability to vary across the width.

In order to vary the concentration and flow rate of the slurry, it is possible to apply not only the examples shown in FIGS. 6 and 7 but also a device in which the slurry generation mechanism is multiplexed.

As described above, according to the present invention, the descaling performance is adjusted by controlling the high pressure water pressure in the width direction of the steel plate,
It is possible to eliminate the occurrence of uneven descaling, and the industrial effects thereof are great.

[Brief explanation of the drawing]

Figure 1 is a graph of the width distribution of the descaling rate, Figure 2 is an explanatory diagram of the conventional projection nozzle, and Figure 3 is the graph of the width distribution of the descaling rate.
Figure a-a arrow view, Figure 4 is an explanatory diagram of the present invention, Figure 5
The figures are explanatory diagrams of another example of the present invention, FIG. 6 is an explanatory diagram of another example of the present invention, and FIG. 7 is an explanatory diagram of still another example of the present invention. 1: High pressure water, 2: High pressure water chamber, 3: Nozzle, 4:
High pressure water hole, A, B, C: Pressure control valve.

Claims (1)

[Claims] 1. When descaling a continuously running steel plate by wet blasting, the wet blast nozzle group is divided into a plurality of blocks in the width direction of the steel plate, and each block is descaled according to the descaling situation in the width direction of the steel plate. A method for descaling a steel plate, comprising adjusting at least one of the high water pressure of a block system, the amount of slurry, and the concentration of slurry in the width direction of the steel plate.