JP2526567B2 - How to change the slab width - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention, when the width of a slab used for rolling or the like is reduced by pressing from both end faces, smoothly changes the width without causing buckling of the slab. The present invention relates to a method of changing the width of a slab that can be performed.

<Prior art and its problems> In recent years, reflecting the diversification tendency of industrial products, there is an extremely wide variety of steel sheet types and product sizes required by customers, and in particular, the product size required for steel sheets is It is becoming extremely large.

By the way, normally, to supply a steel plate of a desired size, a material suitable for the size is required, but most of the slabs used as the material are manufactured by the continuous casting method. As the number of molds increases, it becomes necessary to own a large number of molds to obtain a slab having a size suitable for the slabs, which results in a great disadvantage in terms of manufacturing cost and storage of the molds. In addition, casting slabs of various sizes leads to frequent replacement of molds, impairing the advantages of continuous casting for the purpose of improving productivity.

For this reason, recently, a slab of a certain width is cast without changing the mold, and the obtained slab is pressed from the width end face to change the width (hereinafter, “width sizing”).
The production of slabs of various widths has become popular.

The above-mentioned "width sizing of slab by pressing" means that, as shown in FIG. 4 as a plan view, the width end face of the slab 1 that moves continuously or intermittently is formed such that the inlet side in the slab advancing direction is the inclined portion 2 and the outlet It is a means for sizing by pressing with a pair of pressing dies 4, 4 having pressing faces whose sides are parallel parts 3, and the slab end face and the pressing die are in contact with each other compared to width rolling by an edger mill. Since the contact surface is large, it is possible to significantly reduce the width without causing significant dogbone (swelling deformation of the width end portion in the thickness direction), so that a multi-size slab can be manufactured relatively easily.

On the other hand, however, it has been pointed out that the slab width sizing method using a press causes a troublesome problem of causing buckling of the slab 1 as shown in FIG. 5 when a large reduction is performed.

This is because if the slab buckles as shown in FIG. 5, not only a slab having a predetermined width cannot be manufactured, but also if the degree of buckling is large, it may not be possible to bite into the subsequent horizontal rolling mill.

Therefore, as means for preventing the buckling, the sixth
As shown in Fig. (A), when the width end face of the slab 1 is pressed by a pair of pressing dies 4 and 4 to reduce the width, the central part of the slab 1 is pressed from above and below with the pressing tools 5 and 5. A method for preventing buckling has been proposed (Japanese Patent Laid-Open No. 53-22818). However, in this method, since the central portion of the slab 1 is constrained from above and below by the pressing tools 5 and 5, the thickness increase of the entire slab when the slab 1 is pressed by the pressing dies 4 and 4 causes the slab 1 to be thickened as shown in FIG. ), There is a new problem that the pressing tool 5, 5 tends to cause a flaw in the pressing portion.

Therefore, as shown in FIG. 7, the upper and lower surfaces of the slab 1 are constrained by the press rollers 7,7 which are operated by the hydraulic cylinders 6,6, and the hydraulic cylinders 6,6 are moved to the hydraulic cylinders 6,6 when the pressing dies 4,4 reduce the width. Adjust the pressing force of the hydraulic cylinder according to the acting pressure,
It is possible to prevent the slab from buckling and prevent the flaws caused by the pressing rollers 7 and 7 by performing the pressing necessary to prevent the buckling while allowing the pressing rollers 7 and 7 to retreat according to the amount of increase in the thickness of the slab 1. The means of (1) was also proposed (Japanese Patent Laid-Open No. 60-257902). But,
In this case, it is difficult to judge "whether the slab is in a buckling state or in a thickening state" only from the pressure values acting on the upper and lower hydraulic cylinders 6, 6, and the "thickness buildup speed""," Hydraulic cylinder corresponding to "buckling deformation speed",
It was difficult to deal with problems such as high responsiveness of 6 and extremely expensive equipment.

<Means for Solving Problems> From the above viewpoints, the present inventors can more effectively prevent “buckling”, which is a problem when the hot slab is width-reduced by full-length press working. In order to prevent the occurrence of buckling, various studies have been conducted on the mechanism of buckling occurrence, especially at the time of pressing the slab front and rear ends where it is apt to buckle, and various countermeasures have been repeated, and the following findings have been obtained. Of. That is, (a) Slab buckling during width reduction does not play a major role in the strong pressing force in the width direction, but is triggered by "a small force in the direction perpendicular to the width reduction direction". Is something that occurs.

(B) From this fact, an analysis of what is called a “state where no buckling has occurred” shows that the state is “the press rolling loads from both sides of the slab in the width direction are coaxial and are in equilibrium. It is a very unstable state in which the equilibrium state is easily destroyed by a slight force in the direction perpendicular to the axis.

(C) Therefore, in order to prevent buckling of the slab during width reduction without any particular inconvenience, it is necessary to take measures to stabilize the above "balanced state" without difficulty.

(D) By the way, the "slightly small force in the direction perpendicular to the width reduction direction" described in the item (a) is surprisingly because the slab at the time of pressing is "longitudinal direction" against the width end face pressing die. The most important cause is to have a "tilt angle", and even if the tilt angle is extremely small, it causes buckling.

FIG. 8 is a graph showing the relationship between the table tilt angle in the longitudinal direction at the start of the width reduction press (hence the slab longitudinal tilt angle) and the amount of buckling. It can be seen that if the slab has an inclination angle in the longitudinal direction with respect to the pressing die, even a slight slab causes buckling.

(E) However, when the width end face is pressed down to reduce the width of the slab, a pair of presser rollers equipped with a mechanism for advancing and retracting by a cylinder are arranged above and below the center of the slab width, and the lower presser roller is used. Position control is performed so that the slab becomes horizontal, and on the other hand, if width reduction work is performed while pressing the slab with a constant pressing load at all times during pressing by the upper pressing roller, the cause of the above-mentioned buckling will be To be able to obtain a high quality desired width slab stably without being swept away and causing buckling, and without causing a pushing flaw by a roller.

This invention was made based on the above findings, and the width end faces of the slab are sequentially pressed by a pair of left and right pressing dies having a pressing surface composed of an inclined portion and a parallel portion following the inclined portion. When changing the, place the presser roller that can adjust the vertical position at the vertically symmetrical position of the central part of the slab,
The position of the lower presser roller is adjusted to control the horizontal attitude of the slab at the start of pressing and maintain the slab position after the start of pressing, and the upper presser roller is always used to keep 2 to 8% of the pressing load by the pressing die. The width of the slab can be changed to a desired dimension without causing buckling or roller pushing flaws by changing the width while pressing the slab with the load.

FIG. 1 is a conceptual diagram showing an embodiment of the present invention. FIG. 1 (a) is a plan view thereof, FIG. 1 (b) is a front view, and FIG. 1 (c) is a right side. The views are shown respectively.

In FIG. 1, a slab 1 that has been cast to a constant width dimension by continuous casting and requires a reduction in width is a pair of left and right pressing dies.
When the slab 1 is introduced into a width press working apparatus having 4,4 and a pair of upper and lower presser rollers 8 and 9 arranged in the widthwise center of the slab, the slab 1 is vertically adjustable in its lower presser roller. Position control is performed by 8 so that the posture at the start of pressing is always horizontal. Because, as I explained earlier,
This is because if the slab at the start of pressing has a tilt angle in the longitudinal direction with respect to the pressing die, even a slight amount thereof will cause buckling.

The position of the lower pressing roller 8 is set so as to maintain the above position after the pressing is started. This is because by holding the position of the lower pressing roller 8 as it is even after the start of pressing, the increase in the thickness of the lower surface of the slab is suppressed,
This is to ensure a cross-sectional shape that does not change so much on the bottom surface as shown in FIG. In other words, by holding the cross-sectional shape in this way, it is possible to suppress the inclination in the longitudinal direction due to the buildup of the wall thickness of the slab (which further stabilizes the prevention of buckling), and there is a problem especially in the case of a narrow slab. ”Falling of the slab in the width direction after pressing [3rd
The phenomenon that the slab tilts in the width direction as shown in Fig. 3 (b) due to the bottom surface bulging as shown in Fig. 3 (a) "can be stably prevented.

On the other hand, the upper pressing roller 9 which is also movable up and down
Applies a relatively light pressing load to the slab 1 from the symmetrical position of the lower presser roller 8 during pressing.

In this state, the slab 1 is pressed by the pressing dies 4, 4 from the width end face. During the pressing operation, the hydraulic cylinder is controlled so that the upper pressing roller 9 always presses the slab with a relatively light constant load of 2 to 8% of the pressing load. On the other hand, the pressing roller 9 does not move upside down, and the upper pressing roller 9 due to the buckling symptom is restrained with a sufficient counter force against the pushing back force, so that the pressing roller is prevented from being pushed in. At the same time, it is possible to prevent buckling of the slab. Moreover, since the control of the hydraulic cylinder that operates the upper presser roller is merely to keep the pressing load constant, there is no need for specially complicated and expensive equipment.

By the way, in the method of the present invention, the upper pressing roller 9
The pressing load of the slab was limited to the above range because buckling of the slab could not be prevented when the load was less than 2% of the pressing load of the pressing die, while the pressing by the pressing die was used. This is because if the load is larger than 8%, the upper pressing roller 9 is likely to cause a flaw to be pushed into the slab surface. Of course, it may be possible to prevent the occurrence of indentation flaws by increasing the length of the upper pressing roller 9 close to the width dimension of the slab, but in this case, the pressing device is increased in size and the equipment cost is increased. In addition, since the maintainability of the device also deteriorates, it is not a method that can be adopted at all.

Further, as shown in FIG. 1, the position of the pressing rollers 8 and 9 in the longitudinal direction of the slab is such that the distance X from the corner position where the parallel part and the inclined part of the pressing die 4 intersect is [X ≦ 300 m.
It is good to set it so that it is in the range of [m]. By arranging the pressing roller in the position within this range, buckling of the slab can be prevented more reliably.

Next, the present invention will be specifically described with reference to examples.

<Example> Using a slab press width sizing device having the same structure as that shown in FIG. 1, various positions of the upper and lower presser rolls were used, and each width: 1600 mm, thickness: 270 mm, length : 7000
Place the mm test slab on the roller table with the table inclination angle [ω] = 0.7 °, and move intermittently by 400 mm, press 175 mm from left and right with a pair of pressing dies, and perform width sizing. A width slab was produced.

At the time of this width sizing, the lower presser roller is adjusted so as to be flush with the upper end of the roller of the roller table, and the pressing load of the upper presser roller is set to be 3% of the press load for width sizing. I had it.

The buckling condition of the slab at this time was investigated, and the result is shown in FIG. 9 in relation to the press roll position.

It is clear from the results shown in FIG. 9 that the width sizing can be performed while the buckling of the slab is sufficiently suppressed by carrying out the method of the present invention. It can also be seen that when is separated from 400 mm, 500 mm, and 600 mm, some buckling occurs. However, if the distance X is within 300 mm, it can be confirmed that the effect of the pressing roller is sufficiently exerted and buckling deformation is completely prevented.

In addition, the slab after pressing was inspected for the state of the indentation flaw by the presser roller, and it was found that the indentation flaw was slightly generated only when the slab longitudinal position (distance X) of the pressing roller was set to 10 mm. No defects were found under the conditions. Moreover, the indentation flaw that occurred when the distance X was set to 10 mm was extremely slight, and disappeared due to the rolling performed thereafter and did not cause the surface flaw.

<Effects of the Invention> As described above, according to the present invention, it is possible to easily and surely prevent the buckling and the pressing flaw caused by the presser roller, which are problems when the width of the slab is sized by the press. This makes it possible to carry out a stable slab width changing operation without the need for facilities that would increase the cost, which is an effective industrial effect.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an implementation situation of a slab width changing method according to the present invention. FIG. 1 (a) is its plan view, FIG. 1 (b) is a front view, and FIG. Figure (c) shows a right side view. FIG. 2 is a cross-sectional view in the width direction of a slab obtained when carrying out the present invention. FIG. 3 is a conceptual diagram illustrating “tilt of slab by press” that tends to occur during width sizing, and FIG. 3 (a) shows a situation before slab collapse, and FIG. 3 (b). ) Indicates the situation in which the slab collapsed. FIG. 4 is a schematic diagram for explaining width sizing of a slab by pressing with a pressing die. FIG. 5 is a schematic diagram showing a buckling state of a slab during width sizing by a press. FIG. 6 is a schematic diagram showing an example of width sizing according to the conventional method. FIG. 6 (a) shows a situation before pressing, and FIG. 6 (b) shows a situation after pressing. FIG. 7 is a schematic view showing another example of width sizing by the conventional method. FIG. 8 is a graph showing the influence of the inclination of the slab mounting table (inclination in the longitudinal direction of the slab) on buckling. FIG. 9 is a graph showing the relationship between the presser roller position and the amount of buckling when the slab width sizing method according to the present invention is carried out. In the drawings, 1 ... slab, 2 ... inclined part of pressing die, 3 ... parallel part of pressing die, 4 ... pressing die, 5 ... presser tool, 6 ... hydraulic cylinder, 7 ... Presser roller, 8 ... Lower presser roller, 9 ... Upper presser roller.

Claims (2)

(57) [Claims] 1. When a pair of left and right pressing dies having a pressing surface composed of an inclined portion and a parallel portion following the inclined portion are used to sequentially press the width end surfaces of the slab to change its width, the center portion of the slab width is changed. A presser roller whose vertical position can be adjusted is arranged at a vertically symmetrical position, and the lower presser roller is position-adjusted to control the horizontal attitude of the slab at the start of pressing and to maintain the slab position after the press is started. A slab width changing method characterized in that the width of the slab is changed while pressing the slab with a load of 2 to 8% of the pressing load applied by the pressing die with a roller. 2. The position of the pressing roller is set at the intersection of the inclined part and the parallel part of the pressing die surface, and from the position to the inclined part side.
The slab width changing method according to claim 1, wherein the slab width is between 0 mm apart.