JPS59163012A - Method and device for removing scale - Google Patents

Abstract

PURPOSE:To remove surely scale by intruding abrasive grains into cracks generated in the scale by removing the scale while providing an elongation rate equal to a given value or more to a hot rolling steel strip which is passing through a descaling device which uses the abrasive grains. CONSTITUTION:A tension is provided to a steel strip 1, advancing in the arrow direction, by bridle devices 2, 6 located at the inlet/outlet side. A bend stretching machine 3, a strip-width-camber straightening machine 4, and a brushing device 5 are arranged in sequence between the bridle rolls 2, 6, and the strip between respective devices is supported by guide rolls 8, 11, 15. At that time, plural pairs of bending rolls, consisting each of a bending roll 10 and a backup roll 9, are arranged in the machine 3 to provide a 3.5-15% elongation percentage to the strip 1. Further, the machine 4 formed by disposing a small diametral roll 14 between fixed large diametral rolls 12, 13, straightens the camber. Next, the device 5 formed by arranging roll brushes 17, constituted of NYLON ropes containing abrasive grains, oppositely to respective backup rolls 16 to alternately remove the scale of each side by each brush 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for removing scale that can reliably remove scale from the surface of hot rolled steel strip.

[Prior art]

Conventionally, surface scale on hot-rolled steel strips has generally been removed by pickling, but since it is difficult to dispose of used liquid with this pickling method, acid is not used at all or acid is not used at all. However, it is desired to develop a means for removing scale that reduces the role played by acids. However, in recent years, methods have been developed to remove scale using high-pressure jet water containing abrasives, or scrape it off with brushes, but in the former case, the abrasives bite into the steel and high pressure There are problems such as the huge amount of electricity required to spray jet water, and
The latter method has a problem of poor scale removal efficiency.

In order to facilitate the removal of these scales, as a pretreatment, the hot rolled steel strip is rolled, bent, or slightly bent and stretched to cause cracks in the scales on the surface of the copper strip, making them easier to peel off. It is known.

However, the crank produced by pre-treatment, such as a sub-meter, is merely to ensure the travel distance for the scale to peel off from the surface of the copper strip; It could not be effective.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a scale removal method and device that can strongly and reliably perform the scale removal action itself and achieve complete scale removal. With the goal.

[Summary of the invention]

In order to achieve such an object, the present invention aims to remove cracks that occur in the scale due to the difference in elongation rate between the steel strip and the scale when the steel strip is elongated, by causing the abrasive grains of the descaling device to penetrate into the scale. The peeling force is set to a value that ensures that the peeling force is applied.

First, I will explain the technical basis. The inventor stretched steel strips to various elongation rates and investigated the occurrence of scale cracks.

As a result, when a steel strip is stretched by rolling, cracks occur in the scale depending on the stretching rate, but when the stretching rate is approximately 3%,
It was found that when the temperature exceeds that level, part of the scale is also rolled and cracks are reduced, but rather the scale is compressed to the base material and becomes difficult to remove.

Father, when a steel strip is repeatedly bent many times in a zero force field or in a slight tension field, there is almost no elongation in the steel strip, and scale cracks only open and close repeatedly due to bending. No crack expansion was observed.

Therefore, we attempted to bend the steel strip under a constant tension field. In other words, the elongation (εf) of a steel strip when bending is applied in a tension field can be calculated using the following formula. Move up to. This moving distance a is ax(σm-(-(1,)=2aσ,=+71-h
From, it becomes. In this case, bending with the rollers at the - location requires a total of two bending operations, taking into account rebending, so the elongation of the IJ tube per roll is 2 a with respect to the center of the plate. hσ f RRσ.

becomes.

Moreover, since elongation includes elastic elongation, the actual plastic elongation εpt is as follows, and in the case of n rollers, the following holds true.

The thickness of the test material strip is typically 2.3 rum, the unit tension applied to the strip is 8Kp/+J, and the diameter of the roller is 10011OL+, and the elongation of the strip per roll is as follows. According to the formula, this elongation is approximately 1% and increases in proportion to the number of rollers.

Furthermore, when observing the change in scale shape in the bending and stretching direction when a steel strip is bent and stretched, as shown in Figures 3 to 6, the width of the scale itself is almost constant regardless of the amount of stretching; It was found that the width of cracks formed in the scale increased with elongation. In other words, Fig. 3 is a microstructure photograph at a magnification of 2000 showing the case where the steel strip is elongated by 3%, Fig. 4 shows the elongation at 3.5%, Fig. 5 shows the elongation at 10%, and Fig. 6 shows the case when the elongation is 15%. The part to the edge 1 is the scale, and the part B is the crack.

By the way, FIG. 7 is a schematic diagram showing the cross-sectional shape of a hot-rolled steel strip that has been bent and stretched. As shown in this figure, the scale 30 attached to the base material 31 is broken at approximately equal pitches due to the bending and stretching operation of the upper part, and cracks 29 are generated.

The thickness S of this scale is around 10μ, and the pitch p is 15 to 30μ.

Furthermore, when we investigated the occurrence of cracks on the scale, we found that
It was found that cracks occur almost uniformly regardless of the diameter of the roll used for bending work. From this, it was confirmed that simply stretching the steel strip without bending it was sufficient to generate cracks in the scale, and that the gap g of the cracks tended to increase with stretching.

Analyzing the above phenomenon, scale is a hard material with almost no extensibility, so as the base steel strip elongates, a sliding phenomenon occurs at the interface between the base material and the scale. It is thought that the elongation amount appears as the crack gap g.

Therefore, the crack gap g is equal to the crack pitch p
If the elongation of one base material is ε, it can be expressed as g=ε p.

Next, the relationship between the descaling device and the gap will be considered.

Examples of descaling devices that use grinding abrasive grains include those that mix the abrasive grains into a high-pressure water jet, or those that contain the abrasive grains in a resin wire such as a brush.

In the case of A2203 etc. which are often used as grinding abrasive grains,
Particle sizes of about 50 to 600 μ are mixed. However, the radius of the acute angle portion of each abrasive grain is approximately 1 μ regardless of the grain size. Therefore, when removing scale using such abrasive grains, as shown in FIG. 8, the abrasive grains 32 get caught in the cracked school by being embedded in the crack gap of the scale 30, and remove the scale. It is considered desirable to make it so that it can be removed. That is, it is thought that if the gap g of the crack is made 70 minutes larger than the sharp part of the abrasive grain, the problem of scale peeling will be improved.

In other words, if the scale is removed with a brush made of abrasive grain-containing silicon wire after the scale cracks have grown, the effect of the brush on the scale will be significantly greater, and the scale should be easily removed. .

Figures 9 and 10 show the strip steel scale removal processing speed of 20
The relationship between the elongation rate, scale removal rate, and gap of the steel strip when 0 m/excitation and the number of brushes inserted with grinding abrasive grains is set to two per one side of the steel strip. It was confirmed that as the elongation rate increased, the scale removal rate was rapidly improved. In particular, it has been found that the effect increases significantly when the elongation rate is increased to 3.5% or more. As mentioned above, this means that the growth is 3
．． It is thought that when it exceeds 5%, cracks occur because large abrasive grains can scratch the scale. If the elongation is less than 3.5%, the abrasive grains that are effective in removing scale cannot be caught, and the brush becomes shaped like stroking the surface of scale, making it difficult to remove scale and the scale removal effect is small. .

Moreover, when the elongation of the strip is 15% or more, this scratching effect is saturated, and therefore, the scale removability is also saturated.

However, when we investigated the relationship between the growth rate and the gap, we found that
When the elongation rate is 3%, since the pitch is approximately p-15 to 30μ, g=0.45 to 0.9μ (see FIG. 3).

As mentioned above, the radius of the acute-angled part of the abrasive grain 32 is usually 1μ or more, and if the elongation rate is 3% or less, the abrasive grain hits the gap g, and the abrasive grain slides on the surface of the scale. It was found that it was not effective in removing scale under certain conditions.

On the other hand, when the elongation rate is set to 3.5%, the gap g is 0.
．． 52 to 1.05μ, it becomes possible to obtain a high degree of stability for the scale. If the elongation is further increased to about 4%, the crack gap becomes 0.6 to 1.2μ, which increases the scratching effect of the abrasive grains on the scale, making it easier to remove the scale (Figure 4). ~See Figure 6).

However, when the elongation reaches 15%, as shown in Figure 6, the number of cracks increases compared to when the elongation is 10% (Figure 5).
It was confirmed that the crack gap in Kamura would not widen any further. Therefore, the scraping effect of abrasive grains is 15
If the elongation exceeds %, it becomes saturated. Therefore, from an economic standpoint, it is effective to suppress the upper limit of growth to 15%.

As a result of elucidating the above phenomenon, in the present invention, the scale is removed by a scale removal method using a mechanical descaling device such as a grinding abrasive-containing chiplash while the steel strip is sufficiently stretched.

In addition, in order to perform the scale removal of the present invention sufficiently effectively,
It is desirable to arrange the equipment as described above.

That is, a place for applying tension to the steel strip is provided, and in the case of the bending/stretching method, rollers for repeatedly bending the steel strip are first arranged in this tension field.

The bending rollers may be set based on the number of rollers and the applied tension σf according to the above-mentioned ζ equation.

In addition, when reducing the number N of rollers, appropriate measures such as increasing the tension σf may be taken.

Next, it is desirable to provide a width warpage correcting machine for correcting warpage in the width direction of the strip caused by this bending roller.

In addition, a brush with a backup roller is provided, and the steel strip is wound around the roller in a tension field, so that the brush can be applied well and the removal property by the brush can be improved.

Further, in the brush portion, a device is provided to correct the warp so that the steel strip does not warp in the width direction.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to FIG.

In this embodiment, a bending/stretching type stretching device is used.

That is, in the figure, the steel strip 1 moves in the direction of the arrow (to the right in the figure), and the tension on the steel strip 1 is applied by the priddle device 2.6 on the exit side. These bridle devices are composed of a plurality of rollers 6°, 7, 18, 19, etc.

A bending/stretching machine 3, a strip width rectification correcting machine 4, and a brushing device 5 are arranged in this order between the priddle devices 2 and 6 on the exit side.

The steel strip 1 between each device is supported by guide rollers 8, 11, 15, etc.

The bending and stretching machine 3 is composed of a large number of bending roller pairs each consisting of a bending roller 10 and a reinforcing roller 9 that supports the bending roller 10.
As mentioned above, the steel strip 1 is given an elongation rate of 3.5% or more.

The width rectifier 4 has a fixed somewhat large diameter roller 12.1.
A small-diameter roller 14 is placed between the three, and by moving the roller up and down, the irregularities can be corrected.

has been completed. The brushes 17 are arranged opposite to a bank up roller 16 that supports the steel strip while bending it, and each brush is used to alternately remove scale from one side.

In this example, the thickness of the steel strip was 1.6 to 4.5 m+n, the plate width was 700 to 1500 B, and the processing was performed at a speed of 100 to 250 m/meter.

In addition, the number of bending and stretching rollers is around 100 mm in diameter,
The number of brushes was about 2 to 12, and about 1 to 3 brushes were used for each side.

According to this example, it was confirmed that scale could be almost completely removed.

In the above embodiment, the bending device and the brush device were arranged separately, but the present invention is not limited to such a device. For example, as shown in FIG. After the steel strip 1 has been stretched to a certain extent, a brush 17 containing grinding abrasive grains may be provided on the back side of a bending roller that further stretches the steel strip 1, and a brushing action for removing scale may be performed while the steel strip 1 is being bent and stretched. In this case, the warpage of the steel strip 10 is corrected in order to smoothly convey the strip to the next process.

Further, in each of the above embodiments, the case where the bending device 1 is used is shown, but the present invention is not limited to such a device.
As shown in FIG. 3, the scale may be removed by a grinding brushing device 43 containing grinding abrasive grains so as to stretch the steel strip l in a continuous stretcher manner. That is, the steel strip 4 is inserted between the front bridle roller 40 and the rear bridle roller 42.
1, the steel strip 41 is stretched without being bent while applying a tension that is close to the yield point but slightly exceeding this.

In addition, for safety, it is also possible to provide a small number of pickling devices after the priddle device 6.

In addition, descaling devices are not limited to brush devices.
[Effects of the Invention] As described above, according to the present invention, a descaling device using abrasive grains can be used to stretch a steel strip by a certain value or more. Since the scale is removed, the abrasive grains are inserted into the gaps in the scale, thereby achieving powerful and reliable scale removal, achieving the initial objective.

[Brief explanation of the drawing]

Figures 1 and 2 are theoretical diagrams explaining the present invention in detail, Figures 3 to 6 are micrographs showing the surface structure of the steel strip with respect to scale gaps, and Figure 7 shows the gaps. An explanatory diagram, FIG. 8 is an explanatory diagram showing the relationship between the gap and the abrasive grain, FIG. 9 is a characteristic diagram showing the relationship between the elongation rate and the scale removal rate, and FIG. 10 is a characteristic diagram showing the relationship between the elongation rate and the gap. FIG. 11 is a diagram showing the structure of an example scale removing device. 1.41... Steel strip, 2,6... Tension applying device, 3.
...Bending device, 5,26.43...Descaling device,
32... Abrasive grain. Agent Patent Attorney Tatsuyuki Unuma Accent 1 Illustration Name 2 Illustration q Illustration House 8 Illustration 9 Strip I Nakahi (n,) House Illustration 10 Illustration I 1 Paper mache (Separate Procedural Amendment (Direction 2 1. Case) Indication 1980 Patent Application No. 36926 2 Name of the invention Scale removal method and device 3 Relationship with the case of the person making the amendment Patent applicant name (510) Hitachi Ltd. 4 Agent 5 Date of amendment order 7 , Column for detailed explanation of the invention of the specification subject to amendment, column for brief explanation of drawings, and drawings (Figures 6 to 6). 8. Contents of amendment (1) Page 7, line 8 of the specification (2) Correct "micrograph" on page 16, line 11 of the specification to read "diagram." (3) Figures 6 to 6 are corrected as shown in the attached sheet. Figure 3, Figure 4, Figure 6 above.

Claims (1)

[Scope of Claims] 1. In a scale removal method in which scale on the coated surface of the hot-rolled steel strip is removed by a descaling device using grinding grains while continuously feeding the hot-rolled steel strip, the strip passing through the descaling device A scale removal method characterized by imparting longitudinal elongation of 3.5% or more to steel. 2. The method for removing scale according to claim 1, characterized in that the upper limit of the elongation of the steel strip is set to 15% or less. 3. The scale removal method according to claim 1, wherein the step of imparting elongation to the steel strip includes a step of imparting bending to the steel strip before the steel strip enters a descaling device. . 4. A tension applying device that applies elongation in the longitudinal direction to the hot rolled steel strip is installed in a certain area of the conveying device that continuously conveys the hot rolled steel strip, and a tension applying device that applies elongation in the longitudinal direction to the hot rolled steel strip is provided, and a tension applying device is provided in the area where elongation occurs in the strip steel based on this tension applying device. A scale removal device characterized by being equipped with a descaling device using grinding abrasive grains. 5. The scale removing device according to claim 4, wherein the tensioning device includes a bending device disposed upstream of the descaling device to bend the steel strip. 6. Claim 4, characterized in that the descaling device has a scale removal brush equipped with grinding abrasive grains.
Descaling equipment as described in section.