JPS5933512B2 - Liquid honing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for increasing grinding efficiency when performing grinding processes such as descaling of steel plates by liquid honing. ).

Conventionally, as a descaling method for removing scale from the surface of a steel plate, there is a so-called liquid honing method in which an abrasive material such as iron sand slurry is accelerated with a high-pressure fluid.

There are two types of liquid honing methods that can be roughly divided into two methods: a method of mixing an abrasive material and a high-pressure fluid.

One is an internal mixing method and the other is an external mixing method.

Generally, in the internal mixing method, the abrasive material flows inside the nozzle at high speed, so the problem of nozzle wear is unavoidable.

On the other hand, in the external mixing method, since the abrasive is mixed outside the nozzle, there is naturally no problem with wear.

Furthermore, there is no problem of nozzle clogging due to abrasive material, and it can be said that this method is superior to the internal mixing method.

Figures 1a and 1b are explanatory diagrams showing a nozzle used in a conventional liquid honing method using an external mixing method. As shown in Figure b, high-pressure water is injected into a cylindrical injection part A through a plurality of holes (six holes in the figure) arranged in a circular manner so as to converge at one point. .

The iron sand slurry flow flows out from the slurry outlet hole, flows in such a state that it is surrounded by the six high-pressure water beams, and is accelerated at the focal point of the high-pressure water beams.

Therefore, if the steel plate 3, which is the material to be ground, is placed near or after the focus of the high-pressure water beam as described above, the iron sand grains accelerated by the high-pressure water will collide with the high-speed steel plate 3 and perform grinding. I can do it.

Further, as another example of the conventional external mixing method, there is a method previously developed by a group of the inventors and proposed in Japanese Patent Publication No. 3103/1983.

In this method, a slurry flow of abrasive material such as iron sand is accelerated using a flat spray nozzle.

This method is superior to other methods, such as the method using multiple high-pressure water beams, in terms of workability, such as grinding efficiency and the problem of nozzle clogging.

However, the flat spray method, which has a higher grinding efficiency than other methods, also has the following problems.

Grinding efficiency characteristics differ depending on the spatial arrangement of the material to be ground, such as a steel plate, and the grinding efficiency in the vertical direction is lower than in the horizontal direction (however, in both cases, the direction in which the high-pressure fluid is ejected is is set downward from above with respect to the steel plate).

Figures 2a and 2b are explanatory diagrams showing an example of the method disclosed in Japanese Patent Publication No. 55-3103. 1 is a flat spray nozzle;
2 is an abrasive supply pipe, and 3 is a steel plate as a material to be ground.

The conveyance direction of the steel plate 3 in figure a is a vertical direction, and the spray angle θ of the flat spray nozzle 1 is such that θ>0, where the plane that intersects horizontally with the conveyance direction (vertical direction) of the steel plate 3 is set to 0. The conveying direction of the steel plate 3 in Figure b is horizontal, and the spraying direction of the flat spray nozzle 2 is set downward from above as shown in the figure.

In the case of such a spatial arrangement of the steel plate 3, the grinding characteristics, that is, the conveyance speed at which complete descaling is performed, are as follows.

(1) High pressure water nozzle: Flat spray type (2) Injection pressure crab 20 o1y/crAG (3) Injection water amount: 30
J/mη (4) Iron sand slurry flow rate: 251/mvL (5) Slurry concentration near 0% (6) Hot-rolled plate feeding speed in complete descaling state: 20 m/mm for vertical conveyance, horizontal conveyance In the case of 30 m/mm, the difference in grinding characteristics shown by the difference in the amount of transported dust mentioned above is considered to be due to the following reasons.

First, in the case of figure a, considering the case where the spray direction of the flat spray nozzle 1 is set from above to below, if the steel plate 3 is conveyed in the vertical direction, it will be accelerated by high-pressure water and high-pressure water. After the iron sand slurry flow collides with the steel plate 3, it flows downward from the collision part.

At this time, the slurry flow does not all flow down along the steel plate 3, but a stagnation portion (shown in Figure A) of the slurry flow is generated in a portion sandwiched between the steel plate 3 and the high-pressure water stream.

On the other hand, in the case of figure b, where the steel plate 3 is conveyed in the horizontal direction, the above phenomenon is not observed, and the high-pressure water stream and iron sand slurry flow flow along the steel plate 3.

The stagnation portion of the iron sand slurry flow that occurs during vertical conveyance is considered to be the main cause of the decrease in grinding efficiency.

In other words, because of the stagnation part, the iron sand particles accelerated by high-pressure water collide with the residual iron sand before colliding with the steel plate 3.
Some of the momentum it possesses is lost,
Therefore, it has been confirmed through research by the inventors that the grinding efficiency is significantly lower in vertical conveyance than in horizontal conveyance.

The present invention has been developed in view of the above-mentioned problems, and in the process of continuously removing scale from the surface of a steel plate, such as descaling of a hot-rolled steel plate, the steel plate is conveyed vertically from the viewpoint of equipment space and scale. Often, even in this case,
This was done in order to obtain grinding efficiency equivalent to or close to that of horizontal conveyance, and as a result, the purpose is to reduce the power required for grinding and also to reduce the equipment space. .

That is, in the present invention, when a steel plate is descaled by liquid honing in which the abrasive is accelerated by a flat spray, and the steel plate is conveyed in a vertical or inclined direction, the spray angle of the flat spray is set to -20° to -20°. This is a liquid honing method characterized by honing within a range of 70°.

FIG. 3 is an explanatory diagram showing an embodiment of the liquid honing method of the present invention, and all the reference numerals in the figure are the same as those in FIG. 2.

That is, 1 is a flat spray nozzle, 2 is an abrasive supply pipe, and 3 is a steel plate as a material to be ground.

In addition, the angle at which the flat spray nozzle 1 is set as the spray angle θ with respect to the vertical conveyance direction of the steel plate 3 is a "+" angle with respect to the horizontal direction in the conventional method. In this method, the angle is set to "-".

Next, conditions for applying the liquid honing method of the present invention will be shown.

(j) High pressure fluid nozzle: flat spray type (11)
Injection pressure: 150 to 9/cr; IG (iii) Water volume (per nozzle): 801/TIti11 (iV)
Iron sand slurry amount: 607/mm (v) Slurry concentration: 60-70% (■1) Hot-rolled steel plate thickness: 2.3 mm As is clear from the above application conditions, other conditions are held constant. If the spray direction of the flat spray nozzle is set from below to above (as shown in FIG. 3) with respect to the conveying direction of the steel plate, that is, the vertical direction, the grinding efficiency will be improved.

In other words, in the conventional method, the spray direction was set from above to downwards, but in the present invention, from the viewpoint of grinding efficiency, the spray direction is set from below to above, and this angle is set at an angle with the horizontal plane. The range is -20° to -70°.

It is not preferable to achieve the object of the present invention if this angle is less than -20° or more than -70°.

In addition, in the liquid honing method of the present invention, the conveying direction of the material to be ground such as a steel plate may be a vertical direction or an inclined direction close to this, and the traveling direction may be either from top to bottom or from bottom to top. This is true regardless of the type of flat spray nozzle used, pressure, flow rate, etc.

FIG. 4 is a graph showing the relationship between the spray injection angle θC) and the complete descaling limit feed speed (m/mm) when liquid honing is performed by the method of the present invention.

Example (a) Application purpose: Continuous descaling line for hot-rolled steel coils (b) Hot-rolled coil size: Width: 850 mm, plate thickness: 2
．． 3mm (e) Liquid honing conditions: (+) High pressure water nozzle Flat spray type (11) Injection pressure 150kg/C4G (iii) Injection water amount (per nozzle) 907
/mm (iV) Iron sand slurry flow rate 701/ynj
A(V) Iron sand slurry concentration 60±5%(vi)
High-pressure water injection angle -45° (d) Processing amount: Hot-rolled steel coil feeding speed max. 300
m/m (limit speed at which complete descaling is possible) Maximum hot-rolled steel coil feeding speed (limit speed at which complete descaling is possible) when using the conventional method with an injection angle of +45° and other conditions being the same ) was 200 m/m.

The liquid honing method of the present invention can be applied not only to descaling but also to surface roughness adjustment, film removal process, scratch removal process, etc.

[Brief explanation of drawings]

Figure 1 shows the structure of a nozzle used in the conventional external mixing method, where a is a vertical cross-sectional view, b is a bottom view, and Figure 2 is an explanatory diagram of the conventional method. For example,
FIG. 3 is an explanatory diagram of the method of the present invention, and FIG. 4 is a graph showing the relationship between the spray injection angle and the limit conveying speed for complete descaling in the present invention.

Claims (1)

[Claims] 1 When descaling a steel plate by liquid honing in which the abrasive is accelerated by a flat spray, the spray angle of the flat spray is in the range of -20° to -70° when carrying the steel plate in a vertical or inclined direction. A liquid honing method characterized by: