JPH11156415A - Continuous rolling method by continuous cold rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the continuous rolling method by the continuous cold rolling mill by which the rupture of a plate at the time of a flying change when continuous rolling is performed by the continuous cold rolling mill, can be surely suppressed. SOLUTION: When rolling continuously while performing the flying change by using the continuous cold rolling mill 6 equipping with five rolling stands 1 to 5 to a strip 10 joined with preceding steel strip 10a and succeeding steel strip 10b, with respect to a prescribed length range from the tip of the succeeding steel strip 10b, rolling is performed by the respective rolling stands 1 to 5 so that the plate thickness of the succeeding steel strip 10b is thicker than a standard plate thickness to be determined by a rolling schedule. The ratio of the tension of the preceding steel strip 10a to that of the succeeding steel strip 10b, is set to 1.5 or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous rolling method using a continuous cold rolling mill, and more specifically, to a continuous cold rolling mill for a strip in which a preceding metal strip and a following metal strip are joined. The present invention relates to a method of continuously rolling while changing the running distance using the method.

[0002]

2. Description of the Related Art In order to improve productivity by continuous strip rolling and to improve yield by reducing off gauge, etc.
The rear end of the preceding metal strip and the front end of the following metal strip are welded into a strip by a welding machine arranged on the entry side of the continuous cold rolling mill, and a continuous cold rolling mill is used for the strip. A method of continuously rolling while changing the running distance is widely known. The following description will be made by taking a case where the metal strip is a steel strip as an example.

[0003] The continuous rolling method using such a continuous cold rolling mill is not limited to a simple cold rolling of a steel strip, and recently, a cold rolling mill arranged in a line directly connected to an pickling line or a continuous annealing line. Cold rolling by (for example, a temper rolling mill) is also expanded.

[0004] In order to maximize the effect of improving productivity by continuous cold rolling, a change in running distance is performed when a welded portion of a preceding steel strip and a subsequent steel strip passes through a continuous cold rolling mill. It is extremely important how to suppress the occasional plate breakage.

For example, Japanese Patent Application Laid-Open No. 6-79326 discloses a gauge meter AG when a welded portion of a preceding steel strip made of a hard material and a subsequent steel strip made of a soft material passes through a continuous cold rolling mill.
C to change the roll gap change timing and feed forward AGC or gauge
There has been proposed an invention in which the control of the thickness of the AGC is stopped to secure the thickness of the succeeding steel strip, thereby suppressing the breakage of the sheet due to the thinning caused by the jumping phenomenon that occurs immediately after the weld.

Japanese Patent Application Laid-Open No. 9-94605 discloses that when a steel strip is cold-rolled by controlling the shape of the steel strip in the sheet width direction by work roll bending, the continuous use time of the work roll is increased. By controlling the roll bending force to be reduced together with the steel strip, the elongation rolling is always performed on the steel strip, thereby reducing the tension at the end of the sheet due to the middle elongation shape due to the heat crown, thereby suppressing the sheet breakage. Proposed.

[0007] Further, Japanese Patent Application Laid-Open No. 2-127904 discloses that the positions of welds of a preceding steel strip and a succeeding steel strip are grasped in real time, and the thickness control when the welds pass through a cold rolling mill. An invention has been proposed in which the welding is stopped to make the welded portion thicker than the reference plate thickness, thereby suppressing plate breakage in a continuous annealing process following the rolling process.

[0008]

According to the inventor's experience, the breakage of the sheet when changing the running distance is almost always caused by a weld between the preceding steel strip and the following steel strip or the following steel strip. In the vicinity of the welded portion, and also occurs in cases other than when the preceding steel strip is a hard material and the following steel strip is a soft material.

In the invention proposed in Japanese Patent Application Laid-Open No. 6-79326, it is assumed that the preceding steel strip is a hard material and the following steel strip is a soft material. , The leading steel strip: soft material, and the following steel strip: hard material).

In the invention proposed in Japanese Patent Application Laid-Open No. 9-94605, the occurrence of heat crown is smaller in the case of cold rolling than in the case of hot rolling, and its prediction is difficult. In addition, when changing between runs, a change in tension is likely to occur, and the flatness tends to be lost. Therefore, it is not possible to reliably suppress the breakage of the sheet only by reducing the roll bending force.

Further, the invention proposed in Japanese Patent Application Laid-Open No. 2-127904 is considered to be effective with respect to fracture of the welded portion because the welded portion is made larger than the reference plate thickness. Is not taken into account at all, and depending on the magnitude of the tension, it is not possible to suppress plate breakage in the vicinity of the welded portion of the succeeding steel strip, which occurs most frequently. In addition, the present invention is intended to prevent a sheet rupture in a continuous annealing step following a rolling step, and cannot suppress a sheet rupture at a change in running distance during rolling.

As described above, even with these conventional techniques, it was not possible to reliably suppress the breakage of the sheet when the running distance was changed during continuous rolling by a continuous cold rolling mill.

[0013] An object of the present invention is to provide a continuous rolling method using a continuous cold rolling mill that can reliably suppress the breakage of the sheet when the running distance is changed during continuous rolling by the continuous cold rolling mill. That is.

[0014]

In order to solve the above-mentioned problems, the present inventor has carried out many operational analyzes on continuous rolling by a continuous cold rolling mill having five rolling stands. As a result, it was found that the sheet fracture in the continuous cold rolling occurs when the tension difference between the preceding steel strip and the following steel strip exceeds a certain critical value.

FIG. 1 shows whether or not there is a sheet break when a continuous cold rolling mill is applied to a strip to which a preceding steel strip and a following steel strip are welded. It is a graph which shows a steel strip tension and a following steel strip tension / deformation resistance (%) of a following steel strip. From the graph shown in FIG. 1, it can be seen that the plate breakage is extremely easy to occur when the ratio of the preceding steel strip tension to the following steel strip tension is more than 1.5.

Therefore, the present inventor has determined the rolling schedule of each of the preceding steel strip and the following steel strip in advance for the strip to which the preceding steel strip and the following steel strip have been welded, while changing the running distance. When rolling continuously by a continuous cold rolling mill, the sheet thickness of the following steel strip is adjusted so that the ratio of the preceding steel strip tension to the following steel strip tension is 1.5 or less. The present invention was completed by finding out that by setting the sheet thickness larger than the reference sheet thickness determined by the rolling schedule by a certain length range from the above, it is possible to eliminate the sheet breakage at the time of changing the running distance.

Here, the gist of the present invention is to use a continuous cold rolling mill provided with one or more rolling stands for a strip in which a preceding metal strip and a following metal strip are joined. The method of rolling continuously while changing the interval, for a predetermined length range from the tip of the subsequent metal strip, by each of the rolling stands, the reference plate in which the thickness of the subsequent metal strip is determined by the rolling schedule Rolling is performed so that the thickness is greater than the thickness, and the ratio of the tension of the preceding metal band to the tension of the succeeding metal band after the rolling is set to 1.5 or less.

In the present invention, the term "tension of the preceding metal strip" and "tension of the succeeding metal strip" mean, for each of a plurality of rolling stands, the value of the tension after passing through the rolling stand. I do. For example, in FIG. 2 schematically showing a continuous cold rolling mill having five rolling stands, the tension after passing through a rolling stand i (where i = 1 to 5) shows that the leading metal strip a and the succeeding metal For each band b, Ta _i ,
It is determined as Tb _i. Thus, "the tension ratio of the preceding metal strip against the tension of the trailing metal strip", for each rolling stand is determined as Ta _i / Tb _i (except i = 1 to 5).

Further, the tension Ta _i, Tb _i calculates a preceding metal strip a and the following metal strip b each deformation resistance Km _i in the rolling stand i, the coefficient alpha _i (each in the deformation resistance Km _i seeking unit tension by multiplying the tension / deformation resistance) in the rolling stand, the unit tension was determined by multiplying the thickness h _i and plate width B in the rolling stand, the prior metal strip a and the trailing metal strip each b , Ta _i (T
As _{b i) = α i Km i} h i B, is calculated.

Further, the deformation resistance Km _i, for each rolling stand i for each material, are pre-registered as a modified resistance curve, an example of which is shown in FIG. 3, this value is used. In the continuous rolling method using the continuous cold rolling mill according to the present invention, when the rolling base material of the succeeding metal strip has a flaw, or when the rolling base material is a slab boundary material, the above ratio is determined. To
It is desirable to set it to 1.3 or less in order to surely prevent plate breakage.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a continuous rolling method using a continuous cold rolling mill according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 4 is an explanatory view schematically showing a configuration of a continuous cold rolling mill 6 including five rolling stands 1 to 5 used in the present embodiment.

In the continuous cold rolling mill 6, the thickness, material, slab information (whether or not it is a slab boundary material) and flaw information ( Is sent to the host computer 8, and the host computer 8 sets and calculates the rolling schedule of each of the rolling stands 1 to 5 based on the information. The rolling schedule set and calculated by the host computer 8 is sent to the electric control unit 9, and one or both of the roll reduction amount and the roll peripheral speed of each of the rolling stands 1 to 5 are changed by a control signal from the electric control unit 9. You. In this way, using the continuous cold rolling mill 6 including the rolling stands 1 to 5, the preceding steel strip welded by the welding portion 10 c
Rolling is continuously performed on the strip 10 composed of 10a and the succeeding steel strip 10b while changing the running distance.

In the continuous cold rolling mill 6 of the present embodiment, the higher-level computer 8 makes the thickness of the succeeding steel strip 10b larger than the reference thickness determined by the rolling schedule for each of the rolling stands 1 to 5. The rolling schedule is reset so that the rolling is performed. FIG. 5 is a flowchart showing an example of the reset logic of the rolling schedule by the host computer 8.

Step (hereinafter simply referred to as “S”) 1
, The tension of each of the leading steel strip 10a and the following steel strip 10b
Ta _i, Tb _i is calculated, the process proceeds to S2. Here, as described above, the tension of the preceding steel strip 10a and the tension of the following steel strip 10b refer to the value of the tension after passing through these rolling stands 1 to 5 for each of the rolling stands 1 to 5. This means that Ta _i and Tb _i are determined for each of the preceding steel strip 10a and the following steel strip 10b. The tension Ta _i, Tb _i, as described above, prior steel strip 10a and the trailing steel strip at the roll stand i
It calculates the deformation resistance Km _i of 10b, by multiplying the thickness h _i and plate width B in the rolling stand i coefficients alpha _i in the deformation resistance Km _i (tension / deformation resistance in each rolling stand), preceding steel strip 10a and each succeeding steel strip 10b, Ta _i
As _{(Tb i) = α i Km} i h i B, is calculated. As illustrated in FIG. 3, the deformation resistance Km _i is previously registered in the host computer 8 as a modified resistance curve for each rolling stand i for each material, the value is used.

[0025] In S2, seeking a preceding steel strip 10a and the trailing steel strip 10b each tension ratio (tensile tension / succeeding steel strip 10b of the preceding steel strip 10a) Ta _i / Tb _i. Tension ratio Ta _i
If / Tb _i ≦ 1.5, the process proceeds to S5. On the other hand, if the tension ratio Ta _i / Tb _i > 1.5, the flow shifts to S3.

In S3, in order to prevent the plate from breaking,
The reference sheet thickness ha _i of the succeeding steel strip 10b determined by the rolling schedule is increased by the sheet thickness increase α _i to obtain the reference sheet thickness
(ha _i + α _i ), and shift to S4.

In S4, the tension ratio Ta _i / Tb _i is calculated based on the reference plate thickness (ha _i + α _i ) changed in S3, and if the tension ratio Ta _i / Tb _i ≦ 1.5, Move to S5. If the tension ratio Ta _i / Tb _i > 1.5, the flow returns to S3 and the reference plate thickness is again set to (ha _i + α ′ _i ), and the tension ratio Ta _i / Tb _i is calculated in S4. This loop has a tension ratio Ta
_i / Tb _i ≦ 1.5, and the tension ratio Ta _i
The thickness increase α that gives / Tb _i ≦ 1.5 is determined.

For example, the leading steel strip 10a (40 kg class high-strength steel, strip width 1158 mm) is rolled to a thickness of 3.8 mm to 0.991 mm, and the following strip 10b (ultra low carbon steel, strip width 1239 mm) is rolled. Four.
When rolling from 0 mm to a thickness of 0.738 mm, the leading steel strip 10a
Is 23.3 tons, and the tension of the succeeding steel strip 10b is 12.8 tons, so that the tension ratio is 1.82. Here, S3
In the above, when the thickness increase α = 160 μm is set in a range of 5 m from the tip of the succeeding steel strip 10b, the tension ratio calculated in S4 is reduced to 1.50 or less.

In S5, it is determined whether or not the rolling base material of the succeeding steel strip 10b has a flaw and whether or not the rolling base material is a slab boundary material based on information input from the host computer 7. I do. If there is a flaw in the rolled base material or if it is a slab boundary material, the process proceeds to S6. Otherwise, there is no risk of plate breakage, so the process proceeds to S9 to complete the setting.

[0030] In S6, if the tension ratio was calculated in S4 Ta _i / Tb _i is 1.3 or less, there is no chance of the plate breaking, to complete the setting operation proceeds to S9. on the other hand,
If the tension ratio Ta _i / Tb _i is more than 1.3, the process proceeds to S7.

In S7, the reference plate thickness (ha _i + α _i ) determined in S4 is increased by the plate thickness increase β _i ,
Change and set to the reference plate thickness (ha _i + α _i + β _i ) and proceed to S8.

In S8, the reference thickness (ha
_i + α _i + β _i ), the tension ratio Ta _i / Tb _i is calculated. If the tension ratio Ta _i / Tb _i ≦ 1.3, the process proceeds to S9 to complete the setting. If the tension ratio Ta _i / Tb _i > 1.3, return to S7 and set the reference plate thickness again (ha _i + α _i + β ′ _i ).
As to calculate the tension ratio Ta _i / Tb _i in S7. This loop is repeatedly performed until the tension ratio Ta _i / Tb _i ≦ 1.3 is reached, the thickness increase β _i that provides the tension ratio Ta _i / Tb _i ≦ 1.3 is determined, and the setting is completed.

As described above, in the continuous cold rolling mill 6 according to the present embodiment, when the running distance is changed, the thickness of the succeeding steel strip 10b is changed by the upper computer 8 by the respective rolling stands 1 to 5 according to the rolling schedule. The rolling schedule is further changed so that the rolling becomes larger than the determined reference plate thickness. As a result, after rolling by each of the rolling stands 1 to 5, the tension ratio of the preceding steel strip 10a to the tension of the succeeding steel strip 10b becomes 1.5 or less, especially
In the case where the rolled base material of b is flawed or the rolled base material is a slab boundary material, the tension ratio is reduced to 1.3 or less.

Therefore, according to the relationship shown in the graph of FIG. 1 described above, in the present embodiment, remarkable suppression or elimination of plate breakage at the time of changing the running distance is performed. In the present embodiment, the range in which the reference plate thickness is changed may be a predetermined length range from the tip of the succeeding steel strip 10b. For example, in FIG.
When c passes, the distance may be longer than the distance. When the distance between the rolling stand 4 and the rolling stand 5 is 5 m, the distance may be 5 m or more.

As described above, according to the present embodiment, it is possible to significantly suppress or eliminate the breakage of the plate at the time of changing the running distance, and to remarkably improve both the yield and the operation efficiency.

In this embodiment, since the thickness of the succeeding steel strip 10b is set to be large in a range of about 5 m from the front end, the off-gauge may be increased at first glance. However, this range is a range that must be cut off due to a flaw or the like due to handling before passing through the final line and becoming a final product. Therefore, the yield does not decrease according to the present embodiment.

[0037]

EXAMPLES A continuous rolling method using a continuous cold rolling mill according to the present invention will be described in detail with reference to examples.

(Embodiment 1) FIG. 6 shows that the continuous cold rolling mill 6 shown in FIG. 4 changes the running distance of the strip 10 in which the preceding steel strip 10a and the following steel strip 10b are joined. FIG. 6 (a) is a graph showing the reference sheet thickness when continuous rolling is performed and the tension ratio of each of the preceding steel strip 10a and the succeeding steel strip 10b, and FIG. 6 (a) shows the reference sheet thickness determined by the rolling schedule. FIG. 6 shows a case of a conventional example in which rolling is performed.
(b) shows a case according to the present embodiment in which the reference plate thickness is further changed to reduce the tension ratio to 1.5 or less.

In this embodiment, the reference plate thickness of the succeeding steel strip 10b is set to 160 μm with the arrival of the welded portion 10c (change point between running distances).
m, and linearly decreased to the initial reference plate thickness when it passed a range of 5 m from the tip of the succeeding steel strip 10b. As a result, the tension ratio in the weld zone where the plate breakage easily occurs and in the range of 5 m in the vicinity thereof was reduced to about 1.4.
As a result, regardless of the strength of the welded portion, it was possible to reliably prevent the plate from breaking.

On the other hand, in the conventional example, the tension ratio in the welded portion where the plate breakage easily occurs and in the range of 5 m in the vicinity thereof is
It is 1.8, which is high, and it is understood that there is a high possibility that a plate fracture occurs at or near the welded portion depending on the strength of the welded portion.

Example 2 The continuous rolling method using the continuous cold rolling mill according to the present invention was applied to the strip rolling using the continuous cold rolling mill 6 shown in FIG.
Rolled 10,000 tons. Then, the rate of occurrence of sheet breakage in this rolling was measured, and a comparison was made with the rate of occurrence of sheet breakage according to the conventional method of performing rolling at a reference sheet thickness determined by a rolling schedule as 1. The results are shown graphically in FIG. As shown in the figure, according to this example, the rate of occurrence of plate breakage was reduced by half, thereby improving the operation rate of the cold rolling line.

[Modification] In the description of the embodiment and examples, a steel strip is taken as an example. However, the continuous rolling method by the continuous cold rolling mill according to the present invention is not limited to such an embodiment. For example, the present invention can be equally applied to other metal strips such as a stainless steel strip and an aluminum alloy strip.

In the description of the embodiments and examples,
Although the case where the number of rolling stands is five is taken as an example, the continuous rolling method by the continuous cold rolling mill according to the present invention is not limited to such an embodiment, and includes one or two or more rolling stands. It is equally applicable to continuous rolling using a continuous cold rolling mill.

In the invention proposed in the above-mentioned Japanese Patent Application Laid-Open No. 2-127904, it is assumed that the preceding metal band is made of a hard material and the succeeding metal band is made of a soft material. In the continuous rolling method using a continuous cold rolling mill, such a limitation is unnecessary, and the ratio of the tension of the preceding metal band to the tension of the following metal band is reduced to 1.5 or less by increasing the thickness of the following metal band. Equally applies where possible.

For example, the leading metal band and the following metal band are
In both cases, even if continuous rolling is performed under the same material, same rolling reduction rate, and same sheet thickness, if the sheet width is different (for example, the sheet thickness is reduced from 4.0 mm to 1.0 mm, Is the leading metal band: 1500mm, the following metal: 1000mm)
The present invention can also be applied to further,
Depending on conditions, the present invention can be applied to a case where the preceding metal band is a soft material and the following metal band is a hard material.

[0046]

As described in detail above, the continuous rolling method using the continuous cold rolling mill according to the present invention reliably suppresses the breakage of the sheet when changing the running distance in the continuous rolling by the continuous cold rolling mill. It became possible to do.

According to the present invention, since it is possible to suppress the breakage of the sheet without imposing any restrictions on the welding conditions of the preceding metal strip and the subsequent metal material, it is possible to simplify the rolling schedule for diversified production types. It is an invention that can be assembled and has a very high practical applicability.
The significance of the present invention having such an effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is a graph showing whether or not there is a sheet break when a continuous cold rolling mill continuously rolls a strip to which a preceding steel strip and a following steel strip are welded. It is a graph which shows about the following steel strip tension / the deformation resistance of the following steel strip.

FIG. 2 is an explanatory view schematically showing a continuous rolling mill including five rolling stands.

FIG. 3 is a graph showing an example of a deformation resistance curve.

FIG. 4 is an explanatory view schematically showing a configuration of a continuous cold rolling mill including five rolling stands used in the embodiment.

FIG. 5 is a flowchart showing an example of a reset logic of a rolling schedule by a host computer.

FIG. 6 shows a reference sheet thickness when a continuous cold rolling mill shown in FIG. 4 continuously rolls a strip in which a preceding steel strip and a following steel strip are joined while changing the running distance, and FIG. 6 (a) is a graph showing the tension ratios of the steel strip and the following steel strip together. FIG. 6 (a) shows a case of a conventional example in which rolling is performed at a reference plate thickness determined by a rolling schedule, and FIG. ) Further changes this reference thickness to increase the tension ratio.
This is the case according to the present embodiment with 1.5 or less.

FIG. 7 is a graph showing the results of Example 2.

[Explanation of symbols]

 1-5 Rolling stand 6 Continuous cold rolling mill 10 Strip 10a Leading steel strip 10b Trailing steel strip

Claims (1)

[Claims] 1. A continuous cold rolling mill having one or more rolling stands is continuously rolled on a strip in which a preceding metal strip and a following metal strip are joined, while changing the running distance. The method, for a predetermined length range from the tip of the subsequent metal strip, by each of the rolling stands, so that the thickness of the subsequent metal strip is larger than a reference plate thickness determined by a rolling schedule. A continuous rolling method using a continuous cold rolling mill, wherein the ratio of the tension of the preceding metal band to the tension of the succeeding metal band after the rolling is performed is 1.5 or less.