JPS58176010A - Cold rolling method for controlling shape - Google Patents

Abstract

PURPOSE:To obtain a cold rolled metallic plate free from malformation from a hot rolled metallic plate which does not contain a rimmed layer, by enlarging the diameter of a work roll at the corresponding position by a prescribed quantity, and increasing the rolling pressure at the part near the plate ends, where the hardness is increased. CONSTITUTION:The diameters of a work roll 2 at its both ends, which are the positions corresponding to the hardness increased parts of a metallic plate having the parts of increased hardness near its both ends, are made larger by 1-100mum than the diameters of the work roll 2 at the position corresponding to the starting point of hardness increasing, near the roll center. Then the metallic plate having the hardness increased parts is cold rolled. Thus the elongation at the plate ends is made larger than that of other part, and quater buckling is reduced, accordingly a cold rolled metallic plate excellent in shape and free from malformation is obtained from a hot rolled metallic plate which does not contain a rimmed layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shape-controlled cold rolling method, and more specifically to correcting pocket-like shape defects (hereinafter referred to as side pucks and V-curls) that occur near both ends of a cold-rolled metal strip. Or it relates to a preventable shape-controlled cold rolling method ζ.

Conventional cold-rolled metal strips (hereinafter sometimes referred to as cold-rolled plates).

) For poor shape, ■ear elongation, ■middle elongation.

There are compound elongations where ■■ and ■ coexist, ■quarter buckles, etc., and it has been difficult to completely modify these shapes to obtain a flat metal strip.

In particular, as hot-rolled copper strips manufactured through a continuous casting process (hereinafter referred to as continuous casting materials) have recently begun to be used as raw materials for low-carbon cold-rolled copper sheets, the shape defects peculiar to continuous casting materials have begun to occur. ■The quarter buckle mentioned above has become melted. The reason may be as follows.

In other words, conventional ingot materials such as rimmed steel and capped steel have a rim layer on the surface to varying degrees! This rim layer has fewer impurities and is therefore softer than the center. This appears as a tendency for the edges of the steel strip to be softer than the center when it is a hot-rolled steel strip. This tendency compensates for the increase in hardness that occurs because the cooling rate of the edge of the steel strip is faster than that of the center during the hot rolling process, and as a result, there is a significant inconsistency in the hardness distribution in the width direction of the hot rolled steel strip. -! Rather than causing this, the hardness of the edges tends to be lower than that of the center.

However, killed steel has almost no rim layer like rimmed steel and capped steel, and even if it does have it, it is extremely rare.
As a result of being affected by the widthwise non-uniformity of the cooling rate in the hardness compensation type IQI, the hardness in the vicinity of the edge of the hot wire steel strip is higher than the hardness in the center. generally higher. This property is unique to killed steel in general.
Although this property is not unique to killed continuous cast steel materials, the present invention mainly targets continuous cast guild steel materials, which are used in large quantities. FIG. 1 is a graph showing measured values of the hardness distribution in the width direction of a hot rolled steel strip made of rimmed steel and capped steel, which are ingot materials, and killed steel continuously cast material. In this figure, curves A and B.

C represents the hardness distribution of rimmed steel, capped steel, and continuously cast aluminum guild steel, respectively. In contrast to curves A and B, where the hardness suddenly decreases at the edge, in the case of curve C,
It can be seen that the hardness conversely increases from about 100 μ inside the edge to the edge.

Therefore, while the ingot materials shown by curves A and H are particularly susceptible to edge elongation, the continuous casting material shown by curve C is opposite. That is, if a continuous cast killed steel material is cold rolled under the same conditions as conventional rimmed steel and capped steel, almost no edge elongation will occur, but instead, middle elongation and quarterbuckles will occur frequently. Among these shape defects, medium elongation can be corrected at a comparatively high volume rate by controlling the work roll crown in a concave direction, but quarterbuckle tends to become more pronounced. Therefore, how to reduce this quarterback k is the most important issue in shape control during cold rolling of continuous cast killed steel materials.

The cause of this quarterbuckle occurrence will be described below.

It is generally said that a quarterbuckle is produced by −+ −marization of 7 crowns on a work roll. In other words, during cold rolling, the part of the roll face outside the slope that cannot come into contact with the steel strip directly receives the plastic deformation heat of the copper strip and the heat generated by the friction between the steel strip and the work roll from its surface. Unlike the roll face in a plank road, it is not heated from the surface, so the temperature is relatively low and it does not swell. Since the temperature drop gradient of the work roll is particularly large at the edge of the steel strip, the thermal crown changes greatly near the edge of the steel strip.
Overall, the thermal crown (bulge) of the work opening and the roll becomes smaller from the center of the roll toward the ends of the roll along the roll axis direction.

This thermal crown grows as the amount of rolling increases after the work roll is installed in a cold rolling mill.

It is thought that quarterbuckles occur in areas where the thermal crown change is significant near the edge of the steel strip mentioned above.
It was thought that the extent of this increase would further increase as the thermal crown grows.

According to this principle, rimmed steel and capped steel have low hardness and deformation resistance at their edges, so quarterbuckles occur more than in continuous cast killed steel, which was thought to be a problem.

Furthermore, even in the case of continuous cast steel materials, it was thought that as the thermal crown grows, the darkness becomes more noticeable as quarterbuckles occur, as shown in ijj.

However, actual rolling results using a commercial rolling mill partially contradicted the above expectations; when the material to be rolled was continuously cast guild steel, quarterbuckles became apparent immediately after the work rolls were changed, even before the thermal crown had grown. The phenomenon that occurred was observed.

Therefore, considering this phenomenon, the principle of quarterbuckle generation in continuous cast killed steel material is not due to the growth of a round crown, but rather, as shown in Figure 1, the hardness near both edges is higher than that in the center. It seemed more natural to think that it depends on the fact that 2 is larger than that.

Therefore, the present inventors attempted a theoretical calculation using a so-called split model regarding the influence of the widthwise hardness distribution on the shape of a continuously cast killed steel material after cold rolling.

In other words, the model used for this calculation is based on a so-called split model, and the distribution of deformation resistance in the width direction of the copper strip in the calculation formula is calculated from the results of tensile testing of individual copper strips slit in the width direction of the strip. The value is used.

Figure 2 shows the shape calculation results when a continuously cast guild steel material with the hardness distribution shown in Figure 1, that is, a hot rolled steel strip with hardness increasing near the edges, is cold rolled using five continuous rolling mills. It is a graph showing (width direction distribution of elongation rate difference). Curve E in Figure 2
, F, and G are the increased bending forces applied to the roll, net, and rim of the final stand work roll, respectively, 50 tons, 2
5% (2), the calculation result of the plate shape is shown when the Qt wire is changed to I. Further, Table 1 is a table summarizing the calculation conditions at that time.

Quarterbuckles occur on both sides of the copper strip around a point about 100I31 inside from the edge, which is the point where the hardness starts to increase, and the tendency is to make the overall warb roll crown concave, that is, the further the roll is conveyed. It becomes more noticeable as the time passes. Moreover, FIG. 3 is a graph showing an example in which the shape of a continuously cast killed steel material is measured by a shape detector installed on the exit side of the rolling mill when it is actually cold rolled. In the figure, the horizontal axis represents the position in the board width direction, and the vertical axis represents the output value of the shape detector.

According to FIG. 3, it is recognized that the quarterbuckle shown in FIG. 2 has been generated at the center of the inner dot, 100 m from the edge, immediately after the work rolls were rearranged. In addition, the third
The curve H in the figure shows the shape immediately after the work rolls on the final stand are rearranged, and the curved line shows the shape after rolling 17 hot coils after the rolls are rearranged.

Furthermore, this tendency is not observed in rimmed steel (including capped steel), which does not have an increase in hardness near the edge, so quarterbuckles made of continuous cast killed steel are not thermally cracked, as was conventionally 1g. It was found that this does not occur as a result of growth, but is a property unique to killed steel, with an increase in hardness near the edges. Hereinafter, this quarterbuckle unique to killed steel will be referred to as a side buckle to distinguish it from the conventional quarterbuckle that occurs with the growth of thermal cracks.

′! Table #1 Therefore, the present inventors conducted various experiments and studies in order to find the optimal means for reducing this side buckle.

First, we performed shape simulation calculations based on roll crown control, which involves locally cooling the work roll in the area where side buckling occurs to reduce the roll diameter. Fourth
The results shown in the figure were obtained.

In other words, Figure 4 shows the case of spot googling (curve J
) is a graph showing the difference in shape between curve K and curve K. The basic conditions for calculation are the same as in Table 1.

'i! ! As in Figure J2, the horizontal axis in the figure shows the distance from the center of the plate, and the vertical axis shows the elongation rate difference.

Curve J in Figure 4 is the shape simulation result when a figure-7 depression with a width of 2001 m and a maximum diameter of μm is formed on the work roll by spot cooling, centered on the side buckle generation area. It can be seen that even if roll crown control is performed, the side buckles only move to the center of the copper band and do not disappear. In other words, it has been found that it is difficult to correct side buckles in continuous cast killed steel materials using conventional spot gooling, which involves cooling the work roll in the area where side buckles have occurred.

Therefore, as another means, the hardness increased area near the edge of the steel strip,
That is, we considered a method in which the rolling pressure is increased in areas with high deformation resistance so that the elongation of the copper strip in this area is greater than that in other areas.1: Work rolls and rounds are restricted. Fig. 5 is a graph showing the positional relationship in the roll axis direction C2 between the width direction hardness distribution pattern (curve L) of the continuous cast killed steel material and the initial crown (curve M) of the work roll when rolling this. . In FIG. 5, the horizontal axis represents the position t in the roll axis direction, and the vertical axis represents the initial crown of the work roll for curved rolls and the hardness of the plate for curved rolls. In this case, the taper start point of the work roll represented by curve 8 is made to coincide with the hardness increase start point of the curved copper strip. The distance n& between the taper start point of the work roll and the edge of the copper strip is defined as X, and the work roll diameter difference that changes during the distance X is expressed as y.

Figure 6 shows the first work roll with the values of s7 and lower roll C2 in Figure 5 being 100 mm and 20 μm, respectively.
2 is a graph showing shape simulation results when a continuous cast killed steel material having a hardness distribution C in FIG. 1 is rolled using the final rolling mill shown in the table.

gI! Looking at Figure 116, it can be seen that although the edge elongation becomes a little large at the edge of the steel strip, the side/rips/inkles have almost completely disappeared. In other words, the side buckle that occurs in killed steel continuous cast material C2 with hard penetration rising at the edge is determined by changing the work roll diameter of the part corresponding to this hardness rising part from the work roll diameter of the part corresponding to the hardness starting point. Modified 6■ ability can only be achieved by roll crown control that increases the size of the ball. The value of y varies depending on whether the hardness of the steel strip is increased and the crown of one or both of the upper F work rolls is controlled, but a range of 1 to 100 μmσ) is appropriate. yr', that is, the roll crown is not effective at a length of less than 14 m, and if it exceeds -100 μm, the occurrence of edge elongation becomes noticeable and is not practical. Therefore, the amount of roll crown control to be applied was set in the range of 1 to 100 μm.

The inventors of the present invention have thus discovered that the side buckle can be efficiently corrected by controlling the crown of the work roll in accordance with the hardness-increasing portion of the continuously cast killed steel material, and have arrived at the present invention.

An object of the present invention is to prevent or correct the defective shape of a quarter buckle that occurs when hot-rolled metal strips without a rim layer, such as killed hot-rolled steel strips, are subjected to cold pressing. The purpose of this invention is to provide a shape-controlled cold rolling method for manufacturing good cold rolled plates.

According to the present invention, in the shape control cold rolling method of a metal strip having a hardness increasing portion near the edge of the sheet, the work roll diameter at the corresponding position of the metal strip hardness increasing portion is changed to the hardness increase starting point near the center of the metal strip. A shape-controlled cold rolling method is provided that is characterized by a roll crown control rate that increases the diameter of the work roll at the corresponding position by 1 to 1004 m.

The present invention will be described in detail below using Examples.

Fig. 7 shows both ends of the upper work roll 2 in Fig. 5, fx, y.
This figure shows the condition in which the tip retainer is ground so that the values of FIG. In addition, Fig. 8 shows an example of shape measurement using a shape detector installed on the exit side of the rolling machine in this case, but it can be seen in the comparative example of Fig. 3 even though killed continuous cast steel material was rolled according to this example. The side buckles completely disappeared, and the shape after cold rolling was said to be very stable71.

Note that in Figure ii1%8, the shallow elongation that occurs very close to the edge is caused by making the value of y too large. If the value of y is set to a small value, the extension of the edge can be prevented, although some residual T will remain in the site knot. In this example, the fifth
As shown in the figure, a taper-ground roll with a straight ζ2 taper roll face was used. If the direction is to increase the hardness, the work roll face at a portion corresponding to the hardness increasing portion may be ground in a curved manner. For example, the roll end taper of the work roll can be made into a chevron curve P as shown in FIG. 9, instead of a simple linear taper as shown in FIG.

By folding it in this way, you can effectively prevent side buckling while also suppressing the occurrence of selvage stretching. In addition,
Curve N in FIG. 9 is the hardness distribution in the width direction of the copper strip.

In another embodiment shown below, the above function is improved so that it can be applied to metal strips of different widths.

In other words, a conventional 4-high rolling mill was modified so that both the upper and lower work rolls could be moved in the axial direction, and each work roll itself had a tapered end on one end of the roll face. They are placed symmetrically so that they are sandwiched from both sides by thick retainers. This will allow you to easily apply the present invention to different metal strips in the machine.

Below, specific embodiments of this embodiment will be described.

FIG. 10 is a sectional view of an apparatus used in an embodiment of the present invention.

As described above, the upper and lower thick tapered work rolls are movable in the direction of the arrow.

Now, move one side of the upper and lower wires and rolls in Figure 10 to the fifth
The values of “+Y” shown in the figure are 1100a and 40μ, respectively.
Regarding the influence of the axial movement of the work rolls on the shape after cold rolling when a killed steel continuous cast material is rolled by grinding with a thick tip so that it becomes In and is assembled into a final stand with 5 continuous cold pressure Mfi. state In Figure 11, X is 50 mJt due to the axis movement of the work roll.

The curves Q, R, and is in Figure 11 are graphs showing the changes in the shape measured by the shape detector installed on the exit side of the rolling mill when changing the shape to 100m and 150m. , 100 tpx, and 150 wx. As the value of X increases, the shape shifts in the direction of edge elongation. However, due to the axial movement of the work roll, X can be adjusted to an appropriate value (in this example, I is 100
It has been found that side buckling of continuous cast killed steel materials with different plate widths can be sufficiently prevented if the plate width is maintained at

As yet another embodiment, a case will be described in which a work roll is subjected to roll crown control using a heating/cooling mechanism in the axial direction. The main part of the heating/cooling mechanism is a nozzle that injects heating/cooling medium onto the roll. These nozzles can also move independently in the roll axis direction.

This embodiment attempts to control the thermal strain of the opposing work rolls so that the thermal strain at the hardness increasing portion (g) at the end of the plate is constantly greater than the thermal strain at the hardness increasing portion.

FIG. 12 and FIG. 1J13 are diagrams showing embodiments of the present invention. 2.3 shows the upper and lower work rolls, respectively. A packet 8 is made of snow on a coolant header 10 for cooling the rolls and a cobble guard 9 for draining. 12.13
are a heating medium nozzle and a cooling medium nozzle, respectively, specially provided for the purpose of this invention, and are provided in a shielding box 11 that is shielded except for the work roll side in order to prevent heat from flowing in and out. . Further, the shielding box 11 is constructed integrally with the arm 16, and has a mechanism that can be moved in the roll axis direction by rotation of the trapezoidal screw 14. The vertical movement of the shielding box 11 is restrained by the shielding box 11. Figure 14 shows the changes in the shape detection exudation cover turn provided on the exit side of the rolling mill when a continuous cast of killed steel is rolled using this equipment and the final stand C2 of a five-set continuous cold rolling mill. It is a graph.

Note that the conditions of this apparatus at that time are as shown in Table 2.

Curve U in FIG. 14 is the shape ratio cover turn (comparative example) before using this device. In this case, side buckles centering around the part where the hardness of the plate starts to increase are clearly visible. Curve V is the shape ratio cover turn (embodiment of the present invention) after heating the vicinity of the edge portion for 30 minutes with a heating medium.

It can be seen from this that the side buckles are significantly reduced.

In addition, in commercial mills, rimmed steel and capped steel, which are ingots, are often rolled next to continuous casting of killed steel, so as a countermeasure in that case, cooling medium is applied to the heated roll part. Some water? The results of spraying and adjusting the roll curve (30 minutes heating + 30 minutes cooling) are the first results.
This is shown by curve T in Figure 4. Looking at this, the side buckles are noticeable compared to the continuously cast guild steel material, indicating that roll crown control can be achieved as intended.

Although it is difficult to carry out the present invention by cooling alone, it is quite possible to divide the roll into sections in the axial direction of the roll and use both cooling and heating.

In addition, it is also possible to combine the above-mentioned tapered work roll, a tapered work roll that moves in the axial direction, and these heating/cooling methods.

Note that the shapes (elongation rate differences) at both ends of curve G in Figure 2, curves J and K in Figure 4, and curves in Figure 6 are not included in this graph because the calculated shape values for those portions are extremely large. Therefore, it is shown with a chain double-dashed line to distinguish it from other parts.

By the way, the background of the present invention lies in the discovery of problems in cold rolling using guild steel hot-rolled steel strip manufactured through a continuous casting process. Metal can be similarly overused as long as it is a hot-rolled metal strip without a rim wIA.

By carrying out the invention described in detail below, it is possible to produce a cold-rolled metal strip with a good shape and no quarterbuckle-like defects from a hot-rolled metal strip without a rim layer.

- [In other words, it is possible to prevent or correct the quarterbuckle-like defective shape, which has been difficult to prevent in the past.

[Brief explanation of the drawing]

Figure 1 is a graph showing the measured value of the hardness distribution in the width direction of hot-rolled steel strip, Figure 2 is a graph showing the calculated shape value during rolling of continuous cast guild steel, and Figure s3 is a graph showing the calculated value of the shape during rolling of continuous cast guild steel. A graph showing the measurement results of the sheet shape on the exit side of the rolling mill using a shape detector. Figure 4 is a graph showing the difference in shape calculation results with and without spot googling. Figure 5 is a graph showing the results of continuous casting of guild steel. A graph showing the positional relationship in the roll axis direction between the hardness distribution pattern in the board width direction of the material and the initial crown of the work roll when rolling this. Figure 6 shows the board shape on the exit side of the rolling machine when the present invention is implemented. A graph showing the calculation results, and Figure 7 is a cross-sectional view showing the relationship between the □ plate and work roll during rolling. Figure J8 is a graph showing the measurement results of the plate shape by a shape detector on the exit side of the rolling mill when the present invention is implemented, Figure 9 is a graph showing an example of the initial crack of the work roll in the present invention, and Figure 10 is a graph showing an example of the initial crack of the work roll in the present invention. The figure is a front view of a four-high rolling mill used in the present invention, FIG. 11 is a graph showing the measurement results of the plate shape on the exit side of the rolling mill using a shape detector when the present invention is implemented, and FIGS. 12 and 13 1A and 1B are a side view and a front view, respectively, showing an embodiment of the present invention.
FIG. 4 is a graph showing the results of measurement by a shape detector of the plate shape on the exit side of the rolling mill when the present invention is implemented. 1...-Pressure board, 2.3...Upper and lower work rolls, 4.5...h, -F backup roll, 6.7...・・Upper and lower spindles, 8・・・・−・Packet, 9・・・・・・・・・・
・Cobble guard, 10... Coolant header, 11... Shielding box, 1
2.---Heating medium nozzle. 13・・・・・・・・Cooling medium nozzle, 14・
...-... Trapezoidal screw, 15... Guide shaft, 16... Middle arm. 20 years old, about 3 years old. Skill 4 figure 4 age 5I27 t'rr;h age 81 age 9 figure age 10 figure age 11f! U/2ffl

Claims (1)

[Claims] (1) In the shape control cold rolling method of a metal strip having a hardness increasing portion near the edge of the sheet, the work roll diameter at a position corresponding to the hardness increasing portion of the metal strip is set closer to the center of the metal strip. 1 to 10 times larger than the work roll diameter at the position corresponding to the hardness increase start point.
A shape-controlled cold rolling method characterized by controlling the roll crown so that the thickness is less than 0QI. (The shape-controlled cold rolling method according to claim 1, wherein the two-roll crown control is a roll crown control using a heating/cooling mechanism in the axial direction of the work roll. Alternatively, the shape according to any one of claims 1 to 2 is a roll crown control using a work roll having a tapered initial crown whose diameter increases as the end portions get closer to each other at both ends. Controlled cold rolling method. (4) Shape controlled cold rolling method according to claim 2, wherein the heating and cooling mechanisms are movable independently in the axial direction of the work rolls. The shape control rolling method according to claim 3, wherein the rolling method is axial movement.