JPH11319902A - Manufacturing method of bright finished high carbon steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a flaw on a steel plate in annealing and coiling by using a bright roll to upper/lower work rolls, giving a specified peripheral speed ratio to the peripheral speeds of the upper/lower work rolls and conducting wet type differential peripheral speed skinpass rolling. SOLUTION: After a final pass of cold rolling is conducted by a dull roll, by using a bright roll for upper/lower rolls, wet type differential peripheral speed skinpass rolling is conducted with a difference of 0.05-5 in a differential peripheral speed ratio. The differential peripheral speed ratio is ((V1/V2)-1)×100, wherein V1; high peripheral speed side roll peripheral speed, V2; low peripheral speed side roll peripheral speed. A friction coefficient between a high peripheral speed roll and a steel strip is made larger than that between a low peripheral speed roll and the steel strip. A lubricant oil is not supplied or is supplied a little to the high peripheral speed roll side but is sufficiently supplied to the low peripheral speed side desirably in three times or more of the thigh speed side. The surface roughness of the high peripheral speed side roll is preferably made coarser than that of the low peripheral speed side roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a bright-finished high-carbon steel strip by subjecting a high-carbon hot-rolled steel strip to cold rolling and temper rolling.

[0002]

2. Description of the Related Art In general, high-carbon cold-rolled steel sheets are often used as a bright finish, and a bright finish rolling using a bright roll is performed in the final stage of cold rolling and finish temper rolling.

[0003] Temper rolling is rolling at a light reduction rate (about 0.3 to 3%) applied to an annealed cold-rolled steel sheet to eliminate the yield point elongation of the annealed cold-rolled steel sheet, to improve the gloss and the like. This is performed for the purpose of improving the surface properties, correcting the flatness and shape, and changing the mechanical properties. Since the temper rolling is a rolling with a light rolling reduction, the elongation is used instead of the rolling reduction which is usually used as the working ratio in order to improve the accuracy of the sheet thickness.

The temper rolling includes a wet (hereinafter referred to as wet) rolling method in which rolling is performed while supplying a rolling lubricant, and a dry (hereinafter referred to as dry) rolling method in which lubricating oil is not used.

[0005] The final temper-rolled finished surface roughness of a high carbon steel sheet is required to be not more than 0.3 µm in center line average roughness Ra. However, when performing wet skin pass rolling with a bright roll having a beautiful surface, a phenomenon in which the elongation rate becomes unstable often occurs, which may hinder the rolling operation. If the elongation becomes unstable under low pressure, stable mechanical properties cannot be obtained, and the surface of the steel strip cannot be smoothed. Therefore, in the case of performing wet rolling, the operation is performed by rolling at a high elongation without causing an unstable elongation. However, operating at a high elongation rate leads to an increase in hardness of the product and a deterioration in workability.
Therefore, in order to improve the mechanical properties, it is necessary to take measures such as increasing the temperature of the annealing process, which is a pre-process, and the production cost of the product is greatly increased.

Therefore, when rolling with a bright roll, a dry rolling method capable of performing stable rolling at a low elongation rate may be adopted instead of a wet temper rolling method using a rolling oil or the like. However, when the temper rolling is performed by the dry rolling method, the following problems occur.

[0007] Since the effect of cleaning the roll and the material by the lubricating oil cannot be expected, scratches due to the roll easily occur on the surface of the steel strip, and the yield decreases.

[0008] In some cases, the coefficient of friction becomes so high that rolling at the elongation required for temper rolling cannot be performed. Therefore, since the surface smoothing effect in the final finish rolling is limited, the rolling in the final stage of the cold rolling is inevitably performed by bright rolling using a bright roll.

However, if the final pass of the cold rolling is performed with a bright finish, the surface roughness of the steel sheet is small. There is a problem that winding defects, slipping defects, etc., occur due to the co-deviation, and the yield decreases.

Japanese Unexamined Patent Publication No. 59-73104 discloses a method for avoiding an unstable elongation rate during wet rolling.
The ratio 2R / t of the roll diameter (2R) to the plate thickness (t) is set to 350
The following temper rolling method is disclosed.

However, in this method, in order to keep the ratio between the roll diameter and the plate thickness to 350 or less, it is necessary to have a plurality of work rolls or work rolls having a small diameter. In the former case, the roll needs to be changed every time the sheet thickness changes, and the productivity decreases. In the case of the latter small diameter roll, there is a problem that it is difficult to correct the shape, which is another major role of the temper rolling.

Japanese Patent Application Laid-Open No. 9-85305 discloses that
As a countermeasure against a steel sheet flaw by bright finishing, a method is disclosed in which the final pass of cold rolling is replaced by dull rolling by dull roll instead of bright rolling, and temper rolling is wet rolling with an elongation of 1.0% to 4.0%. I have.

However, this method has burn-in flaws during annealing,
It is effective as a countermeasure against coiling and abrasion during coiling. However, in the case of wet pressure adjustment, an unstable phenomenon of elongation is unavoidable because the conventional method is used, and as a result, a high elongation of about 4% is obtained. Forced to roll. For this reason, it is necessary to sufficiently perform softening during annealing, and it is necessary to take measures such as increasing the annealing time or increasing the annealing temperature.
Productivity decreases.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a bright-finished high carbon steel strip by cold rolling and temper rolling, in which a steel sheet surface generated during annealing or coiling after cold rolling is produced. An object of the present invention is to provide a method capable of preventing flaws and performing stable temper rolling at a low elongation rate and stable.

[0015]

The gist of the present invention relating to a method for producing a bright-finished high carbon steel strip is as follows.

1) A method of producing a bright-finished high-carbon steel strip by subjecting a high-carbon hot-rolled steel strip to cold rolling and temper rolling, wherein the final pass in the cold rolling is rolled by a dull roll. After annealing the obtained cold-rolled steel strip, bright rolls are used as upper and lower work rolls, and the peripheral speed of the upper and lower work rolls is 0.05 to 5% at a different peripheral speed ratio represented by the following formula (1).
A method for producing a bright-finished high carbon steel strip, characterized in that wet-type temper rolling at a different peripheral speed is performed with a difference in the range of:

Different peripheral speed ratio = {(V1 / V2) −1} × 100 (1) where, V1: high peripheral speed roll peripheral speed V2: low peripheral speed roll peripheral speed 2) Different peripheral The bright finished high carbon according to the above 1), wherein the rolling is performed by setting the friction coefficient between the high peripheral speed roll and the steel strip in the rapid temper rolling to be larger than the friction coefficient between the low peripheral speed roll and the steel strip. Steel strip manufacturing method.

The present inventors have found rolling conditions under which stable and efficient temper rolling can be performed with the minimum elongation required to eliminate the yield point elongation in wet temper rolling using a bright roll. Various investigations were conducted to make it possible.

As a result, as long as the conditions of the temper rolling in the conventional range are variously changed, the wet rolling by the bright roll makes the rolling unstable, and the yield point elongation of the steel sheet can be eliminated. It has been found that it is difficult to reduce the rolling reduction to the minimum that is possible and can maintain excellent workability. Therefore, as a result of various studies on rolling methods in which the deformation method of the steel sheet during the temper rolling is different due to processing, it has been found that if the so-called different peripheral speed rolling method is applied, an unstable phenomenon due to a reduction in the rolling reduction can be eliminated. Obtained knowledge.

FIG. 1 is a cross-sectional view parallel to the rolling direction, schematically showing a normal rolling process of a plate. Here, the thickness of the roll on the entry side of the rolling roll before rolling is h ₀ , the speed of the plate is v ₀ , the thickness of the rolled out side is h ₁ , the speed of the plate is v _1, and there is no widening. Since the volume is constant before and after rolling, h ₀ × v ₀ = h ₁ × v ₁ (2) That is, v ₁ / v ₀ = h ₀ / h _1. (3) Assuming that the peripheral speed of the rolling roll is V _R , v ₀ <V _R <
The point which is v ₁ and coincides with the roll peripheral speed and the passing speed of the plate is called a neutral point (N). That is, in normal rolling, the speed of the plate is lower than the peripheral speed of the roll on the entrance side of the rolling roll, and faster than the peripheral speed of the roll on the exit side. However, the surface of the steel sheet is constrained by the contact with the roll and moves at the same speed as the peripheral speed, so that the vicinity of the surface of the steel sheet is subjected to shear deformation. The degree of processing of this shearing deformation is much larger than the elongation by rolling, where fine Ruders bands are concentrated at high density. As a result, these are the starting points of deformation during processing of the steel sheet after temper rolling, suppressing the stretcher strain, and since large deformation is limited near the surface of the steel sheet, the workability of the steel sheet as a whole is It is not spoiled.
However, when wet rolling is performed using a bright roll, the restraint due to contact with the roll on the surface of the steel sheet is greatly reduced, so that the shear deformation is reduced, and the plate is almost in a state of undergoing simple compression deformation. Then, during light rolling, it exhibits a deformation behavior similar to the yield point elongation phenomenon observed in a tensile test, causing an unstable elongation rate of rolling.

FIG. 2 shows an example in which the linear load of the roll (the load on a unit length when the roll is assumed to be in contact with the steel sheet by wire) with respect to the elongation percentage of the temper rolling is measured. The symbol “△” in the figure indicates the result of wet rolling with a normal bright roll. If the elongation is low, there is a risk that the elongation may take two or more values under the same rolling load. It is thought to be causing stability. Only one elongation is determined by one rolling load after the elongation exceeds about 3%.

The measured values indicated by the circles in FIG. 2 indicate that the wet rolling using the same bright roll is performed at a different peripheral speed rolling (different peripheral speed ratio: 0.3%), that is, a pair of rolls rolling in contact with the plate. This is the result of rolling at a different rotation speed or peripheral speed. In this case, even if the elongation of rolling is low,
The elongation ratio to load corresponds to one to one.

FIG. 3 schematically shows the state of different peripheral speed rolling in the same manner as in FIG. Here, the high peripheral speed side is referred to as an upper roll, and the low peripheral speed side is referred to as a lower roll. In the case of the normal rolling with the same peripheral speed shown in FIG. 1, the neutral point N is located symmetrically with respect to the rolling direction of the steel sheet or the steel sheet surface for both the upper and lower rolls. On the other hand, in the rolling by the different peripheral speed rolls shown in FIG. 3, the neutral point _{NH with} respect to the roll on the high speed side is close to the roll bite, that is, the exit side of the portion H biting into the roll of the plate being rolled. The neutral point _NL for the side roll shifts closer to the entry side. This means that in the case of normal constant-speed roll rolling, the shear deformation was limited to the vicinity of the surface of the steel sheet, and the central part of the steel sheet was mainly a mere compression deformation. It means that the deformation is added. As a result, as indicated by the circles in FIG. 2, even at a low elongation rate, it was considered that one elongation rate would correspond if the rolling load was determined.

Therefore, it was decided to apply the different peripheral speed rolling to the temper rolling in order to investigate a limit at which the effect can be sufficiently exhibited. Assuming that the roll peripheral speed on the high peripheral speed side is V _H and the roll peripheral speed on the low peripheral speed side is _VL , the different peripheral speed ratio is {(V _H / V _L ) −1} × 100. (1) It is shown by. However, as a result of performing rolling at various different peripheral speed ratios, when the neutral point N _H on the high peripheral speed roll side is out of the roll bite, the rolling becomes unstable, resulting in a sheet called chattering. Vibration occurs.

[0025] In FIG. 3, to the neutral point in the differential speed rolling is in the roll bite, the left side of the contact point N ₀ of the low linear velocity side of the roll of the neutral point N _L roll entry side of the plate In
The neutral point N _H of the roll on the high peripheral speed side must be to the right of the point N ₁ away from the roll of the rolled plate. Now, assuming that the different peripheral speed rolling is performed in a state where the neutral point _NL is at the position of N ₀ and the neutral point N _H is at the position of N ₁ , the rolling is performed according to the above formula (3). The velocity v ₀ on the entry side of the plate is V _L
In addition, since the velocity v ₁ on the exit side of the rolled sheet is equal to V _H , h ₀ × V _L = h ₁ × V _H (4) The peripheral speed ratio of the roll is V _H / V _L = h ₀ / h ₁ (5), which is a limit because it is within the roll bite at the upper and lower neutral points. is there. Therefore, in different peripheral speed rolling,
In order for the neutral point to be within the roll bite, 1 <V _H / V _L <h ₀ / h ₁ ... (6).

If the difference between the peripheral speeds in rolling at different peripheral speeds becomes too large, the roll peripheral speed on the high peripheral speed side becomes faster than the speed of the sheet on the roll exit side. The rate of increase of the speed of the rolled material on the exit side with respect to the peripheral speed of the roll is referred to as the advance rate. In this case, the advance rate on the high peripheral speed roll side is negative, and the neutral point deviates from the roll bite. Unsatisfactory rolling becomes unstable.

The rolling reduction of the temper rolling is represented by {(h ₀ / h ₁ ) −1} × 100 (7), which is the same as that of the equation (1). As can be seen from the comparison with the equation (6), the different peripheral speed cannot be larger than the rolling reduction (or elongation) of the temper rolling. In particular, when temper rolling is performed on a hard material having a high C content and a low rolling reduction, the elongation of rolling tends to be unstable even when rolling at a different peripheral speed is performed. If the different peripheral speed ratio is increased, the elongation ratio is stabilized, but the limit of the expression (6) is exceeded and chattering is likely to occur.

According to the results of various experiments conducted by changing the conditions of the different peripheral speed rolling, the rolling can be stably performed even in a region slightly exceeding the limit of the equation (6), and the rolling immediately after the roll change is stable. However, when the rolling distance was extended, it became unstable in some cases.

In order to clarify the cause of the occurrence of rolling instability such as chattering during rolling, the advance rate was measured by the roll scribe method. The roll scribe method is a method of measuring the advanced rate of sheet rolling, in which a scribe line is formed on the roll surface and the scribe line interval of the sheet transferred by rolling is compared with the roll circumference.

As a result of the measurement of the advance ratio, in the rolling immediately after the roll change, the advance ratio on the high peripheral speed roll side was positive, but the same roll was rolled at the same peripheral speed while the different peripheral speed ratio was constant. However, at the stage where the rolling instability occurred, the advance rate was negative.

The biggest factor that changes after rolling for a while compared to immediately after the roll change is a decrease in the coefficient of friction due to roll wear. Therefore, focusing on the coefficient of friction and investigating the possibility of performing a different peripheral speed rolling stably even if the different peripheral speed ratio is increased and exceeding the limit of the equation (6), the following means are effective. I found that.

That is, rolling is performed with the coefficient of friction between the high peripheral speed roll and the steel strip being larger than the friction coefficient between the low peripheral speed roll and the steel strip. Specifically, (a) the roll bite angle of the steel sheet on the rolling entry side is made different from the upper and lower sides to increase the angle on the high peripheral speed roll side, and (b) the amount of lubricant supplied to the work roll is increased. (C) To make the difference in the surface roughness of the roll and make the surface of the roll on the high peripheral speed rougher.

The bite angle is the angle between the two surfaces at the position where the roll surface contacts the steel plate surface on the entry side.

By using such means to increase the friction coefficient on the high peripheral speed side rather than the low peripheral speed side, even if the limit of the equation (6) is exceeded, that is, the condition that the neutral point slightly deviates from the roll bite. Even if the rolling is performed at a different peripheral speed ratio, the rolling can be performed stably. Each of these means is effective for improving the stability of rolling even within the range of the expression (6).

By the roll scribe method, the above (a)
As a result of measuring the advanced ratio when the rolling was performed by the method (b) or (c), a positive value was obtained even in the rolling under the condition that the advanced ratio should be negative. The reason is that although the speed of the plate on the roll exit side is lower than the peripheral speed of the high-speed roll, the surface of the steel plate in contact with the roll is restrained due to the increase in friction coefficient, and the vicinity of the surface of the steel plate is sheared and deformed. This is because the upper neutral point is located within the roll bite, and it was presumed that rolling was stabilized.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION A high carbon steel strip to which the present invention is directed is a carbon steel having a C content of 0.1% or more in steel,
The method of the present invention is highly effective when applied to rolling of a relatively hard steel strip.

As described above, the final pass of cold rolling is rolled using dull rolls because of the burn-in flaws during batch annealing after cold rolling and the steel sheet during winding and unwinding between subsequent steps. This is to prevent the occurrence of scratches due to slippage between them. By changing the cold rolling from the conventional bright finish to the dull finish, it is possible to prevent the occurrence of the above-mentioned surface flaws when the steel strip is wound in a coil shape by the dull finish. This reduces the contact area between the steel sheet and the steel sheet.

The roughness of the dull roll is determined according to JIS B06.
If the value of 01 Ra is less than 0.8 μm, the effect of preventing flaws cannot be expected so much. On the other hand, if it exceeds 3.0 μm, the surface roughness of the steel sheet becomes too large, and it is difficult to smoothen it by temper rolling.
Therefore, Ra 0.8 to 3 μ is suitable for bright finish.
m is preferable.

The reason why the passivation rolling is different peripheral speed rolling is to eliminate the yield point elongation at a low rolling reduction such that the workability can be maintained even after the temper rolling, and to perform rolling at a stable elongation. is there.

In the case of different peripheral speed rolling, a function of changing the number of revolutions of a work roll or a backup roll may be added to a normal rolling mill. Can be realized in pairs. In this case, the diameter of the work roll may be used with a difference between the diameter of the work roll in the case of driving a work roll, and the diameter of the backup roll may be used in the case of driving a backup roll.

If the diameter of the work roll is too large, it becomes difficult to roll a thin material.
It is preferable to set the range to about 800 mm. Further, in order to obtain a bright-finished steel sheet, it is preferable that the roughness of the bright roll of the temper rolling be 0.6 μm or less.

The reason why the different peripheral speed ratio is in the range of 0.05 to 5% is that if the different peripheral speed ratio is less than 0.05%, the effect of stabilizing the rolling at a low rolling reduction by the different peripheral speed rolling can be sufficiently obtained. And also
If it exceeds 5%, instability such as chattering at the time of rolling cannot be eliminated in a state where the advance rate is negative. Therefore, the different peripheral speed ratio is in the range of 0.05 to 5%.

Next, the temper rolling is made to be a wet type.
Dry passivation has an excessively high coefficient of friction and cannot be rolled at the elongation required for surface smoothing in temper rolling, so the final pass of cold rolling before temper rolling must be bright-finished. Because it will have to be done. Even if the final pass of cold rolling is dull-finished and the maximum elongation is possible by dry rolling, since the coefficient of friction is high, some irregularities on the surface of the steel strip in dull finishing during cold rolling remain, so dry rolling Not suitable for bright-finished steel strip.

The reason and means of rolling at a higher peripheral speed roll and a steel strip in a different peripheral speed temper rolling preferably with a higher friction coefficient than a lower peripheral speed roll and a steel strip are as follows. It is as follows. By rolling with a higher friction coefficient between the high peripheral speed roll and the steel strip than the friction coefficient between the low peripheral speed roll and the steel strip, the different peripheral speed rate is increased as described above to reduce the low rolling reduction. Rolling can be performed stably. By doing so, even if the rolls are slightly worn out due to rolling for a long time, it is possible to maintain the advance rate positive and extend the roll change, thereby improving the productivity. Therefore, the above method may be performed at a stage where the roll has worn to some extent rather than immediately after the roll change.

There are the following three typical means for increasing the coefficient of friction between the high peripheral speed roll and the steel strip. A) Increasing the bite angle on the high peripheral speed roll side.

This method is based on the effect that the larger the angle is, the smaller the amount of the introduced lubricant is, and the higher the coefficient of friction is. When a plane perpendicular to the plane including the rotation axis of the two rolls in a pair and a plane parallel to the roll surface is used as a normal rolling pass line, the plate surface is positioned at a position where the rolled plate first comes into contact with the work roll. It is desirable that the angle between the line and the normal pass line oscillates in the range of 0.5 ° to 10 ° toward the low peripheral speed roll. This is because when the deflection angle is less than 0.5 °, the effect of sufficiently reducing the amount of the lubricant on the high peripheral speed roll side is small and the friction coefficient cannot be increased. When the deflection angle exceeds 10 °, the effect is saturated. This is because there is no point in increasing the value.

B) Increase the coefficient of friction by changing the supply amount of the lubricant.

In this case, it is desirable that the lubricant is not supplied to the high peripheral speed roll side, or that the lubricant is supplied only slightly, and the lubricant is sufficiently supplied to the low peripheral speed roll side. When supplying lubricant to the high peripheral speed roll,
It is preferable to supply at least three times the amount to the lower circumferential side.

C) The surface roughness of the high peripheral speed roll is made coarser than that of the low peripheral speed roll.

In this case, the surface roughness of the high peripheral speed roll is R
a: It is preferably 0.1 to 0.6 μm, and it is desirable to give a difference of 0.1 μm or more in Ra with respect to the low peripheral speed roll. This is because when the difference in Ra is less than 0.1 μm, the coefficient of friction is too small, the apparent neutral point falls off the roll bite, and when the roughness exceeds 0.6 μm, it cannot be said that it is a bright finish. It is.

[0051]

EXAMPLES (Example 1) High-carbon steel having a chemical composition shown in Table 1 was hot-rolled, cold-rolled into various thicknesses having a width of 1500 mm, and used in the final cold-rolling pass. The roll mat has a bright finish and a dull finish.

[0052]

[Table 1]

After batch annealing these cold-rolled steel strips, using a bright roll having a roll diameter of 500 mm and a surface roughness Ra of 0.3 μm at a rolling speed of 300 m / min and wet rolling using a lubricant. , Different peripheral speed rolling and normal peripheral speed rolling as a comparative example were performed. Also,
As comparative examples, dry rolling without using a lubricant and temper rolling with a small-diameter roll having a diameter of 300 mm were performed. An aqueous solution containing 7% of an organic lubricating oil was used as a lubricant, and in the case of wet rolling, the upper and lower rolls were rolled while supplying an amount of 0.35 l / min per 1 cm in the width direction of the rolls. The temper rolling elongation rate was 1.5
%.

After the cold rolling, flaws due to winding and unwinding during batch annealing and in the course of the process were examined, and the degree of occurrence was evaluated by yield. The result of the temper rolling was evaluated by rolling a coil having a total length of about 3000 m, and evaluating the stability of the elongation during that time and the flatness of the rolled sheet. The gloss is
The steel plate was evaluated for roughness Ra (JIS B0601) and JIS 45 ° gloss.

Table 2 shows the thickness of the steel sheet used in the test, the roll mat for cold rolling, the roll diameter during temper rolling, and the different peripheral speed ratio, and also shows the above evaluation results.

[0056]

[Table 2]

As is clear from the table, according to the method for producing a bright steel strip of the present invention, there is no seizure flaw and no flaw between coil layers, and the elongation of rolling is stable by wet rolling of a bright roll. In addition, it is possible to obtain a high carbon steel strip having good flatness and brightness of the steel sheet. In contrast,
In Comparative Examples not satisfying the conditions specified in the production method of the present invention, satisfactory results were not obtained in any of the yield, product quality and rolling stability.

Example 2 S55 having a C content of 0.55%
For steel equivalent to C, a steel strip having a width of 1000 mm is cold-rolled to a sheet thickness of 0.5 mm, and after annealing, a diameter of 560 m
Temper rolling was performed using a bright roll having a m and a surface roughness Ra of 0.2 μm. The rolling speed was 300 m / min as in Example 1, and the lubricant was also supplied under substantially the same conditions as in Example 1. The peripheral speed of the work roll is set to 0%
0.5%, 1% and 2%, elongation of temper rolling 5%
Rolling was carried out in the range up to and the elongation and the rolling linear load were measured.

FIG. 4 shows the measurement results and shows the relationship between the elongation and the rolling linear load. As is clear from the figure,
In the case of different peripheral speed ratio 0%, that is, normal constant peripheral speed rolling, in the range of small elongation, after showing a large load corresponding to the upper yield point, an unstable behavior in which the change in elongation does not correspond to the load Was presented. This behavior is a phenomenon of elongation of the elongation of rolling, and it is understood that up to 4% of elongation, a stable behavior of one elongation for one load is not exhibited. On the other hand, in the case of the different peripheral speed rolling of the present invention, the load and the elongation are almost proportional to each other from the low elongation, and a stable rolling result is obtained.

FIG. 5 is an example of the elongation chart of the rolling at this time. However, in the conventional peripheral speed rolling, the elongation cannot be controlled if the elongation is 3% or less, because the elongation becomes unstable. On the other hand, in the method of the present invention, the elongation percentage changes stably from a low to a high point, and it can be seen that the rolling can be sufficiently controlled even in the required low elongation percentage range.

(Example 3) SK3 having a C content of 0.80%
A considerable high carbon steel was cold rolled into a steel strip having a width of 1200 mm and a thickness of 0.3 mm. After annealing the steel strip, diameter 560m
Temper rolling was performed using a bright roll having a m and a surface roughness Ra of 0.2 μm. The rolling conditions such as the rolling speed and the lubricant were the same as in Example 1. The position of the deflector roll was raised, and the bite angle was set to 3 ° with respect to the normal pass line. The elongation rate of the rolling was 1%, the different peripheral speed rate was 1%, and the peripheral speed of the upper roll was higher or lower than that of the lower roll, and the two were compared.

In each case, at the start of rolling, the unstable phenomenon of elongation was eliminated, and stable rolling was possible. However, when the upper roll is set to a high peripheral speed, that is, when the lower roll having a large bite angle is set to a relatively low speed, an unstable phenomenon appears when the length of the rolled steel strip exceeds 200 km. I needed to change it. In contrast, when the upper roll had a low peripheral speed, stable rolling was possible even if the length of the rolled steel strip exceeded 400 km.

[0063]

According to the method of the present invention, seizure flaws and slip flaws between coil layers generated on the surface of a steel strip after cold rolling can be prevented, and wet rolling by a bright roll in temper rolling can be performed. It can be performed stably to a low elongation without causing an unstable phenomenon, and since a roll having a large diameter can be applied, the shape of the plate is improved. Reduction of seizure flaws and slip flaws, and reduction of rolling load by reduction of elongation, coupled with the use of large-diameter rolls, drastically reduced the frequency of roll changes, reducing the production cost and yield of high carbon steel bright finished steel strip. The industrial value is great because it is improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a relative relationship between a steel sheet and a rolling roll in a case of normal constant peripheral speed rolling.

FIG. 2 is a diagram showing a measurement result of a relationship between a rolling elongation and a rolling load (linear load) in temper rolling using a constant peripheral speed roll or a different peripheral speed roll.

FIG. 3 is a diagram schematically showing a relative relationship between a plate and a rolling roll in the case of different peripheral speed rolling.

FIG. 4 is a diagram showing a measurement result of a relationship between a rolling elongation rate of temper rolling by a different peripheral speed roll and a rolling load (linear load) when the different peripheral speed rate is changed.

FIG. 5 is a diagram showing an elongation chart in a case where the elongation is changed during the rolling in the normal rolling with the constant peripheral speed roll and the rolling with the different peripheral speed roll.

[Brief description of reference numerals]

Claims (2)

[Claims] 1. A method for producing a bright-finished high-carbon steel strip by subjecting a high-carbon hot-rolled steel strip to cold rolling and temper rolling, wherein a final pass in the cold rolling is rolled by a dull roll,
After annealing the obtained cold-rolled steel strip, bright rolls are used as upper and lower work rolls, and the peripheral speed of the upper and lower work rolls is 0.05 to 5% at a different peripheral speed ratio represented by the following formula (1). A method for producing a bright-finished high-carbon steel strip, characterized in that wet-type temper rolling at a different peripheral speed is performed with a difference in the range. Different peripheral speed ratio = {(V1 / V2) -1} × 100 (1) where, V1: high peripheral speed side roll peripheral speed V2: low peripheral speed side roll peripheral speed 2. A rolling method wherein the friction coefficient between the high peripheral speed roll and the steel strip in the different peripheral speed temper rolling is made larger than the friction coefficient between the low peripheral speed roll and the steel strip. 2. The method for producing a bright-finished high carbon steel strip according to item 1.