JP3601441B2 - Hot slab rolling method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for rolling a hot slab in a rolling facility provided with a sizing press device for performing width reduction rolling of a hot slab.
[0002]
[Prior art]
In order to improve casting efficiency by aiming at a wider casting slab width setting of a continuous casting machine, or to reduce the stock of rolling base material slabs by consolidating the types of casting slab widths, use a sizing press to reduce the casting slab width to a large value. In recent years, a method of freely changing a rolling base material width in hot rolling has been implemented.
[0003]
This sizing press is a wide-width reduction device capable of 300 mm or more in width, but the shape of the hot slab after the large-width reduction is a three-dimensional deformation associated with the width reduction, and the board thickness cross section is extremely extreme. It has a bone shape. The formation of this dogbone shape causes a local increase in the thickness of the sheet near the width edge of the slab, and the entry side sheet thickness increases when viewed from the group of rough rolling mills arranged at the subsequent stage of the sizing press apparatus, and as a result, The rolling reduction will increase. This involves various problems in the design of the rough rolling mill, such as the biting limit and the load torque limit.
[0004]
The design of the draft schedule in hot rolling involves first determining the slab thickness and distributing the amount of reduction of each rolling mill. It becomes necessary to design a draft schedule by adding the amount of reduction. In this case, if the rolling equipment is new, it can be easily reflected in the initial design.However, if a sizing press is introduced into the existing rolling equipment, the rolling reduction of the existing rough rolling mill will be increased to solve the above problems. Capital investment for countermeasures will be required separately. For example, remodeling such as converting the first stage of an existing rough rolling mill to a reversible rolling mill is required.
[0005]
Regarding the arrangement of rolling mills before and after a sizing press, the following prior arts are known. Japanese Patent Application Laid-Open No. 2-217101 discloses a configuration in which a reversible rolling mill (revers rolling mill) or a backpass rolling mill is arranged as the first stage of a rough rolling mill on the exit side of a sizing press. According to the configuration of the present invention, the increase in the thickness due to the width sizing can be dealt with by increasing the number of passes of the reversible rolling mill.
[0006]
Japanese Patent Application Laid-Open No. Sho 60-141301 discloses a sizing press apparatus for pressing a slab from both sides thereof, a vertical rolling mill for rolling a slab from its width direction, and a horizontal rolling mill for rolling a slab from its thickness direction. A method of arranging the slab edges in order and lightly reducing the thickness of the slab edge to flatten the slab edge is shown.
[0007]
Japanese Patent Application Laid-Open No. 1-118901 discloses a method of predicting an increase in a sheet thickness caused by a hot slab width reduction of a sizing press or measuring a thickness rise amount detector and setting a reduction of a rough rolling on a downstream side. A method for preventing a poor biting is reflected in the description.
[0008]
[Problems to be solved by the invention]
However, the above-described prior art has the following problems.
[0009]
The method disclosed in Japanese Patent Application Laid-Open No. 217101/1990 involves problems such as an increase in equipment cost for installing a reversible rolling mill, a reduction in rolling efficiency and a reduction in material temperature due to reversal rolling.
[0010]
In the method disclosed in Japanese Patent Application Laid-Open No. 60-141301, after the width of a hot slab is reduced by a sizing press, the width variation portion of the slab is reduced by a vertical rolling mill. However, since the thickened portion plastically flows in the width direction in the horizontal rolling, it is not useful for preventing the width fluctuation after the horizontal rolling, but also increases the equipment cost and causes a cost increase.
[0011]
In the method disclosed in Japanese Patent Application Laid-Open No. 1-118901, rolling may not be possible due to poor biting depending on the value of the amount of reduction of the rough rolling mill.
[0012]
An object of the present invention is to solve the above-described problems of the prior art, and to provide a hot slab rolling method capable of supplying a slab whose width has been reduced by a sizing press device to a rough rolling step with an appropriate shape and plate thickness. To provide.
[0013]
[Means for Solving the Problems]
That is, the method for rolling a hot slab by a single-stand non-reversible rolling mill capable of reducing the increase in the thickness by the dog bone according to the present invention has the following features.
[0014]
(1) In a hot slab rolling method in which a hot slab is width-down rolled by a sizing press device and then rough-rolled , the roll slab is separated from the exit side of the sizing press device by a distance not less than the maximum length of the hot slab. A single-stand irreversible rolling mill having a work roll of 1000 mm or more is arranged, and the sizing press apparatus and the single-stand irreversible rolling mill do not perform synchronous rolling of a hot slab, and are reduced in width by the sizing press apparatus. Hot slab rolling method , wherein the increased thickness of the hot slab is horizontally rolled by the single-stand irreversible rolling mill, and then rough rolling is performed.
[0016]
Since the single-stand irreversible rolling mill provided for the implementation of the method of the present invention has a light load and a low rolling torque as compared with a normal rough rolling mill, the equipment capacity can be significantly reduced as compared with a normal rough rolling mill. Inexpensive rolling mill can be constructed. At the same time, since it does not take much time unlike the reversible rolling by the reversible rolling mill, the rolling efficiency and the material temperature are not lowered.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 4 shows an embodiment of the hot slab rolling method according to the present invention. FIG. 4 (a) is a plan view of a rolling facility, and FIG. 4 (b) is a side view of the same.
[0018]
In FIG. 4, 2 is a heating furnace for heating the slab, 4 is a sizing press device for reducing the width of the slab, 5 is a group of rough rolling mills provided downstream thereof, A single-stand irreversible rolling mill 3 is disposed on the delivery side (downstream side).
[0019]
In such a facility, the hot slab 1 heated in the heating furnace 2 is first rolled down in width by a sizing press 4 as shown in FIG. The slab 1 is rolled in the thickness direction in a single-stand irreversible rolling mill 3 to reduce the increase in the thickness due to the width reduction. The hot slab 1 from which the increase in the thickness due to the width reduction has been eliminated is sent to the rough rolling mill group 5 and roughly rolled.
[0020]
The single-stand irreversible rolling mill 3 of the present embodiment is constituted by a two-high rolling mill (2Hi).
[0021]
FIG. 2 shows the thickness distribution in the width direction when the width is reduced by the sizing press device 4. In this example, a 350 mm width reduction is applied to a medium-low carbon steel slab having a slab thickness of 256 mm and a slab width of 1550 mm. According to this, the wall thickness increase is equivalent to 44 mm, which corresponds to one pass increase in the rough rolling mill in the next step. In the single-stand irreversible rolling mill 3, such an increase in the thickness is reduced.
[0022]
FIG. 3 shows the relationship between the roll diameter and the amount of reduction in consideration of the rolling material biting limit condition. A radial compressive force N acting on the contact arc, a tangential frictional force T acting on the contact arc, and a longitudinal force H of the rolled material generated by the compressive force and the frictional force act on the biting portion. Is required that the longitudinal force H is positive. If the friction angle ρ (μ = tanρ μ: coefficient of friction) is larger than the bite angle α (the angle at which the compressive force N is inclined with respect to the line connecting the roll axes), the longitudinal force H is always positive. In addition, since it is guaranteed that the rolled material bites and passes, the relationship shown in FIG. 3 is obtained. As shown in FIG. 3, when the width reduction in the sizing press 4 is 350 mm at the maximum and the wall thickness at that time is 44 mm, the roll diameter in consideration of the biting limit condition is 1000 mm. Therefore, it is understood that the roll diameter of the work roll of the single-stand irreversible rolling mill 3 is required to be at least 1000 mm or more in consideration of the thickness increase due to the normal width reduction.
[0023]
In addition, the average width return of the slab when horizontally rolled by the single-stand irreversible rolling mill 3 is at most about 21 mm, and even if only the dog bone portion is reduced, a width expansion that impairs the width reduction effect of the sizing press occurs. Turned out not to be. Here, the width return means that the dog bone thickened portion plastically flows in the width direction due to horizontal rolling, and the width increases.
[0024]
In general, the pressing speed of the sizing press 4 is about 20 mpm, but the distance between the sizing press 4 and the single-stand irreversible rolling mill 3 is set to be longer than the maximum passing slab length. Since the synchronous rolling (simultaneous biting) of the irreversible rolling mill 3 (adjusting rolling mill) can be avoided, the single-stand irreversible rolling mill 3 can be operated at a rolling speed of 70 mpm or more without lowering the efficiency. While the sizing press speed is about 20 mpm, the roll speed of the single-stand irreversible rolling mill needs to be at least 30 mpm from the viewpoint of suppressing the temperature rise of the roll surface. Therefore, the distance between the sizing press 4 and the single-stand irreversible rolling mill 3 is preferably equal to or longer than the maximum length of the hot slab.
[0025]
On the other hand, the rolling reduction of the single-stand irreversible rolling mill 3 can always be set to a constant gap value, that is, "the original slab thickness-mill elongation" without considering the size of the dog bone. Here, the mill elongation is obtained by calculating the total rolling load from the rolling reduction and dividing by the mill constant, and is usually several mm. Therefore, for example, if the original slab thickness is 256 mm and the mill elongation is 4 mm, the reduction setting may be 252 mm.
[0026]
By arranging the single-stand irreversible rolling mill 3 on the exit side of the sizing press 4 in this manner, the rolling reduction of the downstream rough rolling is increased, the draft schedule is not changed, and the efficiency of the rough rolling (t / h) is reduced. ), Slab width sizing is possible without lowering the slab width.
[0027]
【Example】
As shown in FIG. 4, a small two-high rolling mill (2Hi) was disposed as a single-stand irreversible rolling mill 3 on the exit side of the sizing press device 4. The specifications of the sizing press 4 and the single-stand irreversible rolling mill 3 are as follows.
(A) Specifications of the sizing press 4 1) Maximum width reduction 350mm
2) Press speed 20 mpm / 50 spm (shot per minute)
3) Press output 3500kw
4) Slab thickness, width, length 256mm thickness, 950-1900mm width, 9400mm length before press (b) Specifications of single-stand non-reversible rolling mill 3 1) Mill type Work roll 2 stage rolling mill 2) Roll diameter 1260mm
3) Rolling load 2000t or less 4) Rolling speed 70mpm or more 5) Rolling output 2000kw (300% overload)
6) Stand installation position 15 m downstream from the sizing press 4 Using such equipment, the hot slab 1 having a thickness of 256 mm, a width of 1550 mm, and a length of 9400 mm is rolled down by the sizing press 4 with a width reduction of 350 mm. When horizontal rolling was performed by a single-stand irreversible rolling mill 3 and then rough rolling was performed, the thickness increase in width reduction by a sizing press device 4 was 44 mm at the maximum, and the increase in sheet thickness due to the width reduction was simply reduced. As a result of horizontal rolling by the stand irreversible rolling mill 3, the rough rolling by the rough rolling mill group 5 was then able to perform rolling without any problem.
[0028]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a hot slab supply method capable of supplying a slab whose width has been reduced by a sizing press device to a rough rolling step with an appropriate shape and thickness. Moreover, the single-stand irreversible rolling mill used on the downstream side of the sizing press in the present invention has a lighter load and lower rolling torque than a normal rough rolling mill, so that the equipment capacity can be significantly reduced compared to the conventional one, It is advantageous in that it can be constructed at low cost and does not cause reduction in rolling efficiency and material temperature.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an example of a change in the cross-sectional shape of a hot slab in the hot slab rolling method of the present invention. FIG. 2 is a cross-sectional view of a hot slab rolled down by a sizing press in a sheet width direction. FIG. 3 is an explanatory diagram showing a thickness distribution (dog bone profile). FIG. 3 shows a relationship between a roll diameter and a rolling reduction in consideration of a biting limit of a single-stand irreversible rolling mill used in the hot slab rolling method of the present invention. FIG. 4 shows one embodiment of a rolling facility used for carrying out the hot slab rolling method of the present invention, wherein (a) is a plan view and (b) is a side view.
DESCRIPTION OF SYMBOLS 1 Hot slab 2 Heating furnace 3 Single stand irreversible rolling mill 4 Sizing press device 5 Rough rolling mill group

Claims (1)

After the hot slab is rolled down by the sizing press device, in the hot slab rolling method for rough rolling , the roll diameter is 1000 mm or more at a distance of at least the hot slab maximum length on the exit side of the sizing press device. A single-stand irreversible rolling mill having work rolls is arranged, and the sizing press apparatus and the single-stand irreversible rolling mill do not perform synchronous rolling of the hot slab, and the hot work by width reduction in the sizing press apparatus is performed. A hot slab rolling method characterized by horizontally rolling the increased thickness of the slab by the single-stand irreversible rolling mill, and then rough rolling.

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