JPS6345882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thick plate rolling method, and more particularly to a thick plate rolling method suitable for rectangularizing a plate width.

Generally, in the rolling process of thick plates, a slab manufactured using continuous casting equipment or a blooming mill is rolled to a specified thickness using a plate rolling mill, and then cut into product dimensions using a steel sheet shearing machine or a gas cutting machine. Products are manufactured by cutting.

Specifically, the above-mentioned thick plate rolling work includes a forming rolling process,
It consists of a tentering rolling process and a finishing rolling process. First, the slab extracted from the heating furnace is rolled in the longitudinal direction in one pass or two to three passes, with its uneven cross section being made uniform in order to obtain a reference thickness for tentering calculation in a forming and rolling process. Next, after forming and rolling, the rolled material is
It is turned 90 degrees in the horizontal plane and rolled by a predetermined amount in the width direction. Next, this rolled material is again turned 90 degrees in the horizontal plane to return to its original state, that is, a state in which the longitudinal direction matches the pass direction, and is led to a finishing rolling process as the final rolling process by a finishing mill, where shape control is performed. A finished rolled material having a predetermined thickness is obtained.

By the way, the planar shape of the steel plate during thick plate rolling is determined by the recent reduction control rolling method for correcting the planar shape (for example, the
56-21481, etc.), it has been greatly improved, but yield losses such as width cutting allowance and length cropping still occur. From such a thing,
There is a need for a thick plate rolling method that can produce a steel plate that has a rectangular shape on the side surface of the plate end and that does not require width cutting, with little variation in the width of the steel plate in the longitudinal direction after rolling, ensuring a straight edge.

A problem in manufacturing such a steel plate that does not require width cutting is the collapse of the width side of the plate as shown in FIGS. 1 and 2. That is, in the forming and rolling process, rolling is performed by the upper and lower horizontal work rolls 1 and 2, and as a result of this rolling, the side surface of the rolled material 3 has a metal layer between the surface layer, which is the contact surface with the horizontal rolls 1 and 2, and the inside. A double bulging portion 4 occurs due to the flow difference. After that, when the forming rolling shifts to the tentering rolling, the rolled material 3 is rotated 90 degrees and rolled.
As shown in FIG. 2, the double bulging portions 4 are the front and rear ends in the pass direction, and a portion remains as an overlap 5 even if edge rolling is performed by a vertical roll mill during the tentering rolling or finishing rolling in the subsequent step. Since this overlap 5 appears in the finished product,
This results in yield loss.

Conventionally, methods proposed to improve the above-mentioned yield loss include arranging a vertical roll mill for edge rolling on the front or rear side of a horizontal rolling mill;
After forming and rolling, immediately before tentering rolling, the vertical roll mill performs chamfer rolling on the side surface of the rolled material,
There is a method that leads to a tentering rolling process.

However, in the above-mentioned conventional method, since chamfer rolling is performed using a vertical roll mill, dog bones are generated on the side surfaces of the rolled material, and when the rolled material is subjected to tentering rolling, these dog bone portions become the front and rear ends in the pass direction. As a result, as shown in Figure 3A,
In the dogbone part 6, an elongated part 7 is formed by the metal flow during tentering rolling, and the chamfered area is reduced, reducing the collapse prevention effect. There is also the problem that the dot bone is crushed and the metal flow causes a bald-like flaw 10.

Furthermore, the amount of reduction in each pass of tentering rolling is generally carried out at the maximum amount of reduction regulated by the maximum capacity of the rolling mill, such as the maximum torque or maximum rolling load of the rolling mill. The amount of reduction possible in the widthwise pass of the plate rolling mill is approximately 20 mm.

Based on these conditions, if the dog bone is larger than a certain extent (in fact, it may be more than 50 mm), it becomes impossible to bite in tenter rolling, so the conventional rolling method described above cannot be used. At the beginning of tentering rolling, two to three rolling passes are required to erase only the dog bones.

However, in this rolling, each pass twice (biting,
Maintaining consistency between the processing of the detected pulse-like rolling force signal and path advance tracking requires enormous and complex computer logic, making it difficult to realize and even if it is realized. Even if it were possible, it would cause a loss of about 10% in rolling efficiency, which would be a problem.

The present invention focuses on the above-mentioned conventional problems, and minimizes the double bulging and overlapping caused by the difference in metal flow between the surface layer and the inside of the rolled material on the side surface of the rolled material. It is an object of the present invention to provide a thick plate rolling method capable of obtaining a steel plate that does not require width cutting and has a rectangular shape at the end face of the plate.

In order to achieve the above object, the thick plate rolling method according to the present invention uses a vertical rolling mill in which caliber rolls are provided on the upper and lower edges of the side surface of the rolled material in the middle of the forming rolling process, so that the rolling process that occurs during the width rolling process After predicting the amount of collapse that will occur and determining the amount of chamfering according to the prediction and performing a chamfering edge pass,
By carrying out more than one pass, the dogbone portion generated at the edge portion in the width direction of the rolled material by the chamfering edge pass is rolled down, and when the tentering ratio is around 1.5, the rolling process is sequentially led to the tentering rolling process and the finishing rolling process. However, this vertical rolling mill has a caliber roll and a flat roll in an integrated structure, and the mechanism is such that the use of both can be performed by shifting the rolls in the vertical direction. Furthermore, when the tentering ratio is other than around 1.5, at the end of the forming rolling process including the chamfering and horizontal rolling, or instead of the horizontal rolling, the rolled material is rolled at the center in a cross section parallel to the longitudinal direction according to the tentering ratio. This is a thick plate rolling method in which a rolling process is performed to make the part thinner or thicker than both ends, and then the plate is sequentially led to a tentering rolling process and a finishing rolling process.

Since the double bulging portion 4 generated during forming rolling grows in the subsequent tentering rolling to form an overlap 5, the present invention quantitatively grasps the amount of growth in tentering rolling, that is, the amount of metal flow, and In order to prevent the flow from overlapping 5, chamfer edging rolling is applied to the upper and lower edges of the side surfaces of the rolled material in advance according to the amount of growth during forming and rolling, and the dogbones formed by this rolling do not return in width, and This was done based on the knowledge that it was necessary to avoid an increase in load.

Now, when the rolled material 3 is chamfered and edged rolled using a vertical rolling mill equipped with caliber rolls 8 as shown in FIG. 4, the rolled material 3 becomes a dogbone shape. The amount of chamfering of this dog bone portion 6 is expressed as the width dimension a and the vertical dimension b as a cross-sectional area, and the amount of inclination (overlap length) of the side surface of the sheet width after tentering rolling is expressed as δ, and the relationship between the two is expressed with the chamfer angle θ being constant. As a result of experiments, the relationship shown in FIG. 5 was obtained. As shown in this figure, the two are in an inversely proportional relationship, and when no chamfer edging rolling is performed at all, the amount of collapse δ is maximum. Therefore, by increasing the amount of chamfering, the amount of collapse δ can be made as small as possible, and can ultimately be eliminated. In this case, since the rolled material 3 is subjected to edging rolling using flat rolls of a vertical rolling mill in the finish rolling process, the amount of collapse δ is eliminated to some extent, so the limit value for eliminating it (δ≒5 mm, broken line in Figure 5) It is sufficient to perform chamfering by the amount of chamfering corresponding to the amount of chamfering. Furthermore, from the above, when the chamfer width dimension a is constant, the larger the chamfer thickness dimension b is, and conversely, when the chamfer thickness dimension b is constant, the greater the chamfer width dimension a, the greater the collapse prevention effect. I can understand that. Here, according to experiments, the amount of collapse is greater when the amount of chamfering in the width direction (dimension a) is larger than the amount of chamfering in the thickness direction (dimension b) (a/b>1)
becomes smaller. Therefore, it is desirable to increase the chamfer width dimension a so as to increase the ratio a/b.

Moreover, by performing chamfer edge rolling, the generated dogbone portion 6 becomes higher than the surface of the rolled material 3. If the height of this dog bone becomes high, it will encourage the width return after the flat pass by the horizontal roll during tentering rolling, and the collapse prevention effect will be lost. Here, the side plate thickness B of the rolled material 3, the central plate thickness
The dogbone height is expressed as (B- _H0 ) as _H0 , and the relationship between this and the chamfering width method a is determined by changing the chamfering angle θ of the caliber roll 8, as shown in FIG. This was determined by a lead rolling experiment with the rolled material width dimension A = 100 mm, plate thickness H ₀ = 28 mm, and chamfer angles θ = 30°, 45°, 60°, and 90°, respectively. As is clear from this figure, in order to increase the chamfering effect while suppressing the dogbone height, the chamfering angle θ may be made smaller so as to increase the chamfering dimension a. However,
As the chamfer angle θ becomes smaller, the load torque on the vertical rolls increases, resulting in a load on the equipment. Therefore, in the chamfer edging rolling, the load on the vertical rolls is kept to a minimum while ensuring the chamfering effect with the chamfered cross-sectional area. The problem was solved by horizontal rolling. For this reason, the chamfer angle θ of the caliber roll 8 is set to θ≈60 degrees so as to satisfy the above conditions in order to set the chamfer angle θ such that the load tolerance limit of the vertical rolling mill is not exceeded. However, in order to respond to various changes in rolling conditions,
It is also possible to install caliber rolls other than θ=60 degrees.

Specifically, the method for determining the optimum amount of chamfering using the lead model is as follows.

Plate thickness H ₀ = 28 mm, tentering ratio Hp (ratio between the target width of the rolled material after final rolling and the width of the slab before rolling)
When is 2.5, the chamfered area (S = 1/2ab) that eliminates sagging in finish rolling is 20 mm ² , and it has been found that the effect of reducing sagging is proportional to the chamfered area.

Therefore, considering this condition that the optimum chamfered area is proportional to the square of the plate thickness, S/H ₀ ² =const, and therefore S/H ₀ ² =0.025 can be found.

On the other hand, due to the roll load, the chamfer angle is θ=
60 degrees, and the amount of chamfering is given by the chamfer width dimension a, and defined as a=αH ₀ , S=1/2ab=1/2a ²・tanθ=1/2(αH ₀ ) ² ta
nθ, it is given as S/H ₀ ² = 1/2α ² tanθ = 0.025 ∴α = 0.17, and the relationship between the plate thickness H and the amount of chamfering a is given by the following equation.

a=0.17H ₀ (However, the width ratio is 2.5) Here, since the above formula is for the width ratio 2.5,
Assuming that the amount of chamfering is proportional to the amount of tenting, the optimum amount of chamfering is a=0.17・H ₀・Tentration ratio −1/2.5−1.0.

Furthermore, as mentioned above, in the forming and rolling process, if chamfer edging rolling is performed, then horizontal rolling is performed in the longitudinal direction, and then tentering rolling is started, collapsing is prevented, but the planar shape of the rolled material changes after rolling is completed. If it becomes a pincushion-like shape where the width at both ends is larger than the center width, or a drum-like shape where the width at both ends is smaller than the center width, side clots will eventually occur. Therefore, unless the planar shape is also made rectangular, it is not possible to obtain a steel plate that does not require cutting to a sufficient width. Therefore,
If necessary, after the rolling process including the chamfer edge rolling, in the longitudinal direction of the rolled material,
As a measure against the pincushion shape, a rolling process is added to make the center part thicker than both ends, or as a measure against the drum shape, a process is added in which the center part is made thinner than both ends. That is, according to experiments, the shape of the side crop portion of the rolled material after the final rolling process is largely influenced by the tentering ratio Hp, as shown in Fig. 7, and the side crop portion may be pincushion-shaped or drum-shaped. The tenting ratio, which is the boundary between the two, is Hp≒1.5. Here, the tentering ratio Hp is expressed as the ratio between the target width of the rolled material after the final rolling is completed and the width of the slab before rolling.

For this reason, in the present invention, rolling (forming) that changes the plate thickness in a cross section parallel to the longitudinal direction of the rolled material is particularly advantageous.
MAS rolling), and optimal rolling control is performed to make the planar shape rectangular according to the tenting ratio of the rolled material. Specifically, when the tentering ratio is Hp<about 1.5, the predicted planar shape of the side crop portion is pincushion-shaped. In this case, when the forming pass is completed, the thickness of the rolled material is controlled to have a drum cross-sectional shape in a cross section parallel to its longitudinal direction, such that the thickness at the center is thicker than at both ends. On the other hand,
When the width ratio is Hp > approximately 1.5, the predicted planar shape of the side crop portion will be drum-shaped. In this case,
At the completion of the forming pass, the thickness of the rolled material is controlled so that it has a pincushion cross-sectional shape in a cross section parallel to its longitudinal direction, with the thickness at the center being thinner than at both ends.

Here, the specific amount of thickness change Δh(x) to be given to the rolled material is as follows. In other words, the slab dimensions before rolling are t x w x l (thickness x width x length)
The slab dimensions at the completion of the forming pass are T ₁ × W ₁ ×
If L ₁ (average thickness x width x length) and the final rolled product dimensions are T x W x L (thickness x width x length),
The volume to be reduced by the minute portion Δx at the rolling direction position x whose thickness is controlled at the completion of the forming pass shown in FIG. 8A, and the longitudinal direction position X of the thick plate after rolling is completed as shown in FIG. 8B. As a result of experiments, it is recognized that the volume corresponding to the side crop shape change amount Δw(X) of the minute portion ΔX has a constant volume relationship.

Therefore, △x・W ₁・△h(x)=△X・T・△w(X)
...The relationship (1) holds, and the following equation holds.

△h(x)=△X・T・△w(X)/△x・W ₁ ……
(2) Here, the slab width W ₁ at the completion of the forming pass is equal to the slab width w before rolling, and △X/△x=L/
Since there is a relationship _L1 , the above △h(x) becomes △h(x)=△w(X)/W·T ₁ (3). In other words, the specific amount of thickness change △h(x) that should be given to each rolling direction position x of the rolled material at the completion of the forming pass is the amount of side crop shape change △w(X) at position X, the target of the final rolled product. It can be calculated based on the width W and the slab average thickness T ₁ at the completion of the forming pass, which is set in the pass schedule.

The specific amount of thickness change △h (x ₀ ) that should be given to the center of the rolled material at the completion of the forming pass is △h (X ₀ ) = △w/W・T ₁ ...(4) , can be calculated based on the side crop amount Δw determined from the tenting ratio Hp in FIG. 7A.

For this reason, the thick plate rolling method according to the present invention quantitatively predicts the amount of collapse that occurs during tentering rolling, and removes the upper and lower edges of the side surfaces of the plate that contribute to the collapse before the tentering rolling process. Final step of forming and rolling
Before ~3 passes, chamfer edging rolling is performed using a chamfering caliber roll of a vertical rolling mill, and then at least one forming pass is passed to roll down dog bones that occur at the side edges of the plate during chamfer rolling. Further, when the tentering ratio Hp exceeds 1.5 or becomes less than 1.5, it becomes necessary to make the plane rectangular, and in such a case, so-called forming MAS rolling is performed. After that, the rolled material is turned 90 degrees and subjected to a width-setting pass and a finishing pass, thereby making it possible to manufacture a steel plate that does not require width cutting. This pass schedule is shown in FIG.

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

First, horizontal rolls 1 and 2 are applied to the target rolled material 3.
Accordingly, the rolled material is passed through one pass or multiple passes along the longitudinal direction, and forming rolling is performed to average and even out the uneven cross section in order to obtain a reference thickness for tentering calculation (FIG. 10 A1). At this time, a double bulging portion 4 is generated on the side surface of the rolled material 3 (B1 in the figure). Next, in the middle of the forming and rolling process, before the last one to three passes of the forming pass, chamfering edging rolling is performed using a vertical rolling mill equipped with chamfering caliber rolls 8 (A2 in the figure). In this case, etching is performed with the chamfering angle θ by the caliber roll 8 being θ≒60 degrees, but this is the optimum angle obtained through repeated lead rolling experiments. Slab thickness≧
This is the conditional angle that minimizes the amount of collapse in the case when the tentering ratio is 260 mm. The amount of chamfered by this chamfer-edging rolling is set to such a size that the collapse elimination limit value δ = 5 mm (in Fig. 5, 1/2・a・b=200mm ² ), taking into consideration the edge rolling in the later finish rolling. The above shall apply. By this chamfer edge rolling, the rolled material 3
The cross-sectional shape is a dogbone shape, and the rolled material 3
Dogbone portions 6 are formed on both sides of (B2 in the same figure). In reality, the greater the thickness of the slab, the greater the amount of collapse, which may be 40 mm or more, and in this case, assuming θ = 60°, the chamfer amount a must also be 40 mm or more. Therefore, the dog bone height (B-H) is also 50mm.
As mentioned above, if the height of the dog bone section 6 is not kept below a certain limit, it will cause equipment load on the horizontal rolls during tentering rolling, and the chamfered area will be reduced due to the metal flow during tentering rolling. At this point, add at least one molding pass (see A in the same figure).
3). In this forming pass using horizontal rolls 1 and 2,
The chamfered area after the dogbone portion 6 is reduced is at least the collapse elimination limit value δ.
= 5 mm or larger (B3 in the same figure).

Next, when the tentering ratio Hp of the material to be rolled is 1.5, it can be directly led to the tentering rolling process, but when the tentering ratio is Hp > 1.5 or Hp < 1.5, so-called shaped MAS rolling is performed. . In other words, when Hp > 1.5, it is predicted that the planar shape will be drum-shaped, so horizontal rolls 1 and 2 will continue.
The thickness is controlled along the longitudinal direction. This controls the thickness so that the thickness at the center is thinner than at both ends (A, B4 in the same figure). This thickness control amount may be a value calculated using equations (3) and (4) above. Conversely, when Hp<1.5, the thickness may be controlled so that the thickness at the center is thicker than at both ends.

Note that it is also possible to use the forming MAS pass for dog bone reduction after chamfer edge rolling.

In this way, along with the forming rolling process including chamfering and rolling, forming
The rolled material subjected to MAS rolling is rotated 90 degrees in a horizontal plane, and then subjected to tentering rolling by alternately using horizontal rolls and a vertical rolling mill as appropriate. In this case, the vertical rolling mill is provided with a flat roll portion 9 on the roll surface with a caliber, and the roll is shifted upward to perform etching during tentering. After that, the rolled material is turned 90 degrees again, and finish rolling is similarly performed by alternately using horizontal rolls and vertical rolling mills as appropriate to make the width of the material uniform in the longitudinal direction, achieve the target thickness, and achieve the desired shape. It is possible to finally manufacture a steel plate that does not require width cutting.

As explained above, according to the thick plate rolling method according to the present invention, chamfer edging rolling is performed during forming rolling, and the rolling of the dogbone portion to be formed is carried out by forming rolling without sending it directly to the tentering rolling process. By performing at least one pass or more of horizontal rolling with horizontal rolls and performing forming MAS rolling as necessary, the strip width control effect is extremely high, and the shape of the strip width end face is rectangular, resulting in a steel plate that does not require width cutting. It has the excellent effect of being able to produce

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the rolling situation during forming and rolling;
Figure 2 is a cross-sectional view showing the rolling situation during tentering rolling;
3A and 3B are cross-sectional views showing the metal flow condition of the dock bone portion during tentering rolling, respectively. FIG. The figure is a graph showing the relationship between the amount of fall and the amount of chamfering, Figure 6 is a graph showing the relationship between the dogbone and the amount of chamfering, Figure 7A is a graph showing the relationship between side crop amount and tenting ratio, and Figure 7B is a graph showing the relationship between side crop amount and width ratio. FIG. 8A is a plan view showing the side crop shape after rolling, and FIG.
FIG. 8B is an explanatory diagram showing the shape of the thick plate after rolling,
FIG. 9 is a flowchart of the thick plate rolling method of this embodiment, and FIGS. 10A and 10B are rolling cross-sectional views and perspective views of the rolled material corresponding to each step of the forming rolling. 1, 2... Work roll, 3... Rolled material, 4...
...Double bulging part, 5...Overlap, 6
...Dotsugubone Club, 8...Calibur Roll.

Claims (1)

[Claims] 1. A thick plate rolling method in which a rolled material is sequentially guided through a forming rolling process, a tentering rolling process, and a finishing rolling process to form a side end shape into a rectangular rolled material,
During the forming rolling process, a rigid rolling mill equipped with caliber rolls on the upper and lower edges of the side surfaces of the rolled material predicts the amount of collapse that will occur during the tentering rolling process, determines the amount of chamfering according to the prediction, and performs chamfering. After performing the etching pass, by performing at least one pass of horizontal rolling in the longitudinal direction of the rolled material, which is the same direction as the etching pass, the chamfering etching pass causes the edges in the width direction of the rolled material to be perpendicular to the longitudinal direction of the rolled material. A thick plate rolling method characterized in that the dogbone portion is rolled down, and when the tentering ratio is around 1.5, the plate is sequentially led to a tentering rolling process and a finishing rolling process. 2. In a thick plate rolling method in which a rolled material is sequentially introduced into each step of a forming rolling process, a tentering rolling process, and a finishing rolling process, and the side end shape is formed into a rectangular rolled material,
During the forming rolling process, a rigid rolling mill equipped with caliber rolls on the upper and lower edges of the side surfaces of the rolled material predicts the amount of collapse that will occur during the tentering rolling process, determines the amount of chamfering according to the prediction, and performs chamfering. After performing an etching pass, horizontal rolling is performed for at least one pass in the longitudinal direction of the rolled material, which is the same direction as the etching pass. If the dogbone part is rolled down and the tenting ratio is not around 1.5, then at the end of the forming rolling process or instead of the horizontal rolling, the rolled material is rolled at the center in a cross section parallel to the longitudinal direction of the rolled material according to the tenting ratio. A method for rolling a thick plate, characterized in that rolling is carried out to make the thickness of the part thinner or thicker than that of both ends, and after the end of the process, the process is sequentially led to a widthwise rolling process and a finishing rolling process.