JP2000190003A - Temper rolling method for stainless steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temper rolling method to stably roll a stainless steel strip superior in surface quality even in high-elongation rolling, especially superior in luster degree even during the flow of a temper rolling agent is changing, without necessity of a large equipment investment. SOLUTION: When temper rolling is done by spraying the temper rolling agent which is made to be fine droplets by mixing gas, the target spray amount, when the spray amount of the temper rolling agent is increased, is achieved by raising the gas pressure and then increasing the liquid pressure of the temper rolling agent. The target spray amount, when it is decreased, is achieved by decreasing the liquid pressure and then decreasing the gas pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temper rolling method for a stainless steel strip, and more particularly to a temper rolling method for a stainless steel strip capable of stably rolling a stainless steel strip having excellent surface quality while suppressing uneven gloss. It relates to a rolling method.

[0002]

2. Description of the Related Art After annealing, a cold-rolled stainless steel strip is subjected to so-called temper rolling in which cold working is performed with an elongation of about 0.5% to 1.5%. The purpose of the temper rolling is to eliminate the elongation at yield point of the steel strip after annealing, to correct the shape and to impart gloss, and the like, with particular emphasis on imparting gloss to the stainless steel strip.

[0003] Methods of temper rolling of stainless steel strip include so-called wet rolling using a lubricant such as rolling oil (temper rolling agent) and dry rolling without using a temper rolling agent. Dry rolling to obtain the degree is carried out,
As the rolling mill, a two-high rolling mill provided with a large-diameter roll capable of easily removing abrasion powder and foreign matter adhering to the roll surface is used in many cases.

[0004] The mechanism for improving the gloss in temper rolling is that a stainless steel strip is rolled with a large-diameter roll having a roll surface smoothed at an elongation of about 0.5% to 1.5% to make the roll surface smooth. It is intended to further improve the glossiness by transferring to a steel strip and having a long contact arc length by a large-diameter roll.

[0005] However, in dry rolling, (1) the coefficient of friction between the roll and the stainless steel strip is so high that high elongation rolling cannot be performed. (2) The fine powder adhering to the roll wear powder and the steel strip. There is a problem that scales and the like adhere to and accumulate on the roll surface, thereby deteriorating the quality of the steel strip. Therefore, in a continuous line incorporating a temper rolling mill in the continuous annealing equipment, the elongation rate of temper rolling is limited to a low level, and it may be necessary to perform temper rolling again in another line to secure the elongation rate. , Productivity has been forced to decline.

As a countermeasure, application of wet rolling using a temper rolling agent during temper rolling has been studied. Wet rolling has the advantage of enabling high pressure and cleaning the roll surface with a temper rolling agent, making it possible to remove dirt and foreign matter adhering thereto, but also has the luster as described above. There is a problem that it is difficult to secure the degree.

As a method for improving the glossiness, Japanese Patent Publication No.
Japanese Patent No. 393982 discloses a temper rolling method for a stainless steel strip in which dry rolling with an elongation of 0.1 to 0.5% is performed in a first pass of temper rolling and wet rolling is performed in a second pass and thereafter. Have been.

In Japanese Patent Application Laid-Open No. 4-333303, two or three temper rolling mills are provided, wet rolling is performed in the first stand, and rolling oil remaining in the second and third stands (temper rolling). Temper rolling of a stainless steel strip in which temper rolling is performed using only the agent.

However, the aforementioned Japanese Patent Publication No. 57-3984
No. 2 and Japanese Patent Application Laid-Open No. 4-333303 each presuppose simple pass rolling simply in a plurality of passes combining conventional dry rolling and wet rolling. Not applicable to one-pass rolling at Further, by performing wet rolling, there is a problem that the mechanism for improving gloss by dry rolling described above is hindered, and high gloss cannot be obtained.

The present applicant discloses in Japanese Patent Application Laid-Open No. 8-215706 that a temper rolling agent and a gas are mixed and sprayed as droplets having an average diameter of 30 μm or less, and a high elongation and a high gloss are obtained by rolling in one pass. The method of temper rolling of stainless steel strip which can obtain the following is presented.

[0011]

Generally, in a temper rolling mill, a succeeding coil is sequentially welded to a preceding coil and rolling is continuously performed. At that time, it is necessary to adjust the flow rate of the temper rolling agent during rolling according to rolling conditions such as a rolling speed and an elongation rate, but there is a problem that uneven gloss is likely to occur during the flow rate change. The method disclosed in JP-A-8-215706 adjusts the flow rate of the temper rolling agent by adjusting the liquid pressure and the gas pressure of the temper rolling agent. However, there is a concern that the above-mentioned uneven glossiness may occur.

An object of the present invention is to stabilize a stainless steel strip excellent in surface quality even in high elongation rolling, and particularly excellent in gloss even during a change in the flow rate of a temper rolling agent, without requiring a large capital investment. To provide a temper rolling method capable of rolling.

[0013]

Means for Solving the Problems As a means for solving the above-mentioned problems, the present inventors have proposed a method for temper rolling a stainless steel strip by spraying a temper rolling agent into fine droplets by mixing gas. In addition to confirming the conventional knowledge of the following a and b by this method, various investigations were made by paying attention to the droplet diameter of the temper rolling agent when changing the spray amount of the temper rolling agent, and the following c and d I got new knowledge.

A. By performing a temper rolling by spraying a temper rolling agent into fine droplets by mixing a gas, high gloss can be obtained even in high elongation rolling.

B. However, when the droplets become coarse, spot-like gloss unevenness is generated on the roll surface, and the gloss unevenness is transferred to the coil surface, thereby deteriorating the coil surface properties. In a continuous line, once gloss unevenness occurs on the roll,
Uneven gloss is continuously transferred over a long distance after the next coil, and the yield is reduced, and the line must be stopped.

C. When changing the spraying amount of the temper rolling agent, it is necessary to change the gas pressure (also referred to as gas pressure) and the liquid pressure of the temper rolling agent. The diameter becomes coarse.

FIG. 1 is a graph schematically showing a pressure change when the gas pressure and the liquid pressure are simultaneously changed and the pressure is reduced. As shown in the figure, the pressure drop of the liquid pressure is slower than the gas pressure. Therefore, during the change of the spray amount, the liquid pressure becomes relatively higher than the gas pressure, and the droplet diameter becomes coarse.

D. When increasing the spraying amount, increase the gas pressure and then increase the liquid pressure.When decreasing the spraying amount, decrease the liquid pressure and then decrease the gas pressure to reduce the droplet diameter. Coarsening can be suppressed.

The present invention has been completed on the basis of the above-mentioned findings, and the gist of the invention is that "a temper rolling agent formed into fine droplets by mixing a gas with a stainless steel strip annealed after cold rolling. A temper rolling method performed by spraying, when increasing the spraying amount of the temper rolling agent during temper rolling, increasing the pressure of the gas, and then increasing the liquid pressure of the temper rolling agent When the spraying amount is reduced, the hydraulic pressure is reduced, and then the pressure of the gas is reduced to obtain the target spraying amount, whereby a temper rolling method for a stainless steel strip is performed. It is.

[0020]

FIG. 2 is a schematic view schematically showing a temper rolling apparatus according to the method of the present invention.
2 is a work roll, 3 is a nozzle, 4 is a stainless steel strip,
5 is a gas pressure setting device, 6 is a liquid pressure setting device, 7 is a flow rate calculation device, 8 is a setting change instruction device, and 9 is a tracking device.

As shown in FIG.
Nozzles 3 are installed on the inlet side of the temper rolling mill 1 having the following conditions. The temper rolling agent and gas are supplied to each nozzle 3 and mixed to form fine droplets. Injection and temper rolling. The position where the temper rolling agent is injected onto the stainless steel strip is preferably on the stainless steel strip surface or the work roll surface on the side of the temper rolling mill. Here, the temper rolling agent is a liquid used for lubricating the work roll and the stainless steel strip at the time of temper rolling, and an aqueous solution in which an organic lubricant is mixed with water at a concentration of several% is usually used. Used. Droplet size is 3
0 μm or less. Air is usually used as the gas mixed with the temper rolling agent. In addition, temper rolling mill,
It may be a four-high rolling mill provided with a work roll and a backup roll.

FIG. 3 is a schematic diagram illustrating the method of the present invention.
FIG. 7A shows the case where the amount of the temper rolling agent sprayed is reduced.
FIG. 6B shows a case where the spray amount is increased.

The method of the present invention is a method of performing a temper rolling by spraying a temper rolling agent into fine droplets by mixing a gas onto a stainless steel strip, and reduces the spray amount of the temper rolling agent. At this time, as shown in FIG. 3 (a), the liquid pressure of the temper rolling agent is reduced, then, after Δt time, the gas pressure is reduced to the target spray amount, and when the spray amount is increased, As shown in FIG. 3 (b), the gas pressure is increased, and then after Δt time, the fluid pressure is increased to a target spray amount. With this method, it is possible to prevent the droplet diameter from becoming coarse while the spray amount is being changed, and to prevent the occurrence of spot-like uneven gloss. Preferably, when reducing the spray amount, the hydraulic pressure is reduced, then the gas pressure is reduced, and the change of the hydraulic pressure is terminated during the change of the gas pressure.

Next, the change in the droplet diameter during the change of the spray amount in the method of the present invention will be described.

FIG. 4 is a graph schematically showing an example of a change in the spraying amount of the temper rolling agent and a change in the droplet diameter when the liquid pressure and the gas pressure are changed in the method of the present invention.

In FIG. 4, it is assumed that a change is made from point A to point C having the same droplet diameter M and different target spray amounts. In this case, according to the method of the present invention, the droplet diameter changes as shown by the curve 1 in the figure, and the droplet diameter can be set to M or less even while the spray amount is being changed. The change in the droplet diameter when the change from the point C to the point A is performed is shown by a curve 2. Similarly, the droplet diameter can be set to M or less even during the change of the spray amount. Thus, according to the present invention, it is possible to prevent the droplets from becoming coarse during the change of the spraying amount of the temper rolling agent.

Next, an embodiment of the method of the present invention will be described with reference to FIG. In FIG. 2, the tracking device 9 is a setting change instructing device 8 that outputs information such as a welding joint point between coils.
To communicate. The setting change instructing device 8 obtains the timing for changing the spray amount based on the information and conditions such as the rolling speed.
The flow rate calculating device 7 calculates the fluid pressure and the gas pressure necessary for changing the spraying amount based on data obtained in advance by experiments, and outputs information on the change start time and the pressure change amount per unit time to the gas pressure setting device 5. And the fluid pressure setting device 6. In the gas pressure setting device 5 and the liquid pressure setting device 6, the change timing of the gas pressure and the liquid pressure and the pressure are controlled, and the spray amount is changed.

FIG. 5 is a sectional view showing an example of a nozzle used in the present invention. 3 is a nozzle, 10 is a first injection pipe,
11 is a second injection pipe, 12 is a temper rolling agent, 13 is a gas, 1
There are four droplets.

As shown in FIG. 5, the nozzle 3 has a structure having a second injection pipe 11 for injecting a temper rolling agent into the inside thereof and a first injection pipe 10 for injecting a gas to the outside thereof. The gas 13 can be mixed with the agent 12 and ejected as fine droplets 14.

The method of the present invention is preferably applied to a case where the target elongation is changed during rolling or a case where the rolling speed is changed.

[0031]

(Embodiment 1) An apparatus having the structure shown in FIG.
Lead coil (steel type: SUS430, size: plate width 100)
0 × 0.3mm thickness) and subsequent coil (steel type: SUS43)
0, size: temper rolling of a continuous coil connected to a sheet width of 1000 × sheet thickness of 0.4 mm). Temper rolling mill
It is a two-high rolling mill equipped with a work roll having a diameter of 700 mm, and a nozzle 3 having an opening diameter of 0.2 mm having a structure shown in FIG. Equipped. In addition, an organic lubricant is used as a temper rolling agent in an amount of 10%.
% Was used as the aqueous solution and the gas. The rolling speed was 100 m / min.

The target elongation of the leading coil and the trailing coil is 0.8%, and the spraying amounts of the temper rolling agent are 120 cc / min and 100 cc, respectively, due to the limitation of the maximum rolling load.
/ Min. The gas pressure / liquid pressure is 3.0 kgf / cm ² /1.2 kg for each of the leading coil and the trailing coil based on the spray amount and the target droplet diameter (20 μm).
f / cm ² and 2.4 kgf / cm ² /0.8 kgf
/ Cm ² .

As shown in FIG. 3 (a), the amount of spray from the preceding coil to the succeeding coil was reduced by changing the hydraulic pressure and then changing the gas pressure.
Table 1 shows the time at which the gas pressure and the hydraulic pressure change start and the time at which the change ends, as the elapsed time from the start of the hydraulic pressure change. The table also shows an example in which the change of the gas pressure and the change of the liquid pressure were simultaneously started as a comparative example.

[0034]

[Table 1]

As shown in Table 1, in the example of the present invention, the change of the liquid pressure is first started at a pressure reduction rate of 0.1 kgf / cm ² / s,
Next, 3 seconds after the start of the change of the liquid pressure, the pressure reduction rate is 0.5 kg.
The change of the gas pressure was started at f / cm ² / s, and the change of the gas pressure was completed 0.2 seconds after the change of the liquid pressure was completed. The time required for changing the hydraulic pressure and the gas pressure was 4.2 seconds, during which the length of the unsteady portion coil was about 7 m.

In the comparative example, the change of the fluid pressure and the gas pressure were started simultaneously, and the change of the fluid pressure was completed 2.8 seconds after the completion of the change of the gas pressure. Note that the pressure reduction rates of the liquid pressure and the gas pressure are the same as the conditions of the present invention.

Table 1 shows the occurrence of gloss unevenness of the coil after temper rolling. As shown in the table, in the example of the present invention, there was no gloss unevenness in the non-stationary part and the rear coil, and the result was good. The elongation percentages of the leading coil and the trailing coil were 0.8% as expected.

In the comparative example, the droplet diameter became about 50 μm on average during the change of the liquid pressure, and spot-like gloss unevenness occurred on the back surface of the coil. Spot-like gloss unevenness occurred on the surface of the lower work roll of the rolling mill, and the unevenness was copied over the entire length of the subsequent coil, causing gloss unevenness.

Example 2 Using the apparatus having the structure shown in FIG. 2, the rolling speed was changed from 100 mpm to 150 mpm during temper rolling of a SUS430 coil (sheet width 1000 mm × sheet thickness 0.3 mm). The temper rolling mill and the nozzle were the same as in Example 1. The target elongation of the coil is 0.7%
Due to the restriction of the maximum rolling load, the spraying amount of the temper rolling agent was 1 at rolling speeds of 100 mpm and 150 mpm, respectively.
20 cc / min and 250 cc / min. The gas pressure / liquid pressure is determined by the spray amount and the target droplet diameter (20 μm).
respectively rolling speed 100mpm and 150mpm from m) was 2.5kgf / cm ² /1.0kgf/cm ² and 3.5kgf / cm ² /1.8kgf/cm ^2.

As shown in FIG. 3 (b), the increase in the amount of spraying caused by the change in the rolling speed was performed by a method in which the change in the gas pressure was started and then the change in the liquid pressure was started. Table 2 shows the start time and the end time of the change of the gas pressure and the liquid pressure by the elapsed time from the start of the change of the gas pressure. The table also shows, as a comparative example, an example in which the changes of the gas pressure and the liquid pressure were started at the same time.

[0041]

[Table 2]

As shown in Table 2, in the example of the present invention, first, the gas pressure change was started at a pressure increase rate of 0.5 kgf / cm ² / s, and then, one second after the start of the gas pressure change, the pressure increase rate was reduced to 0 kgf / cm ² / s. .
The change of the liquid pressure was started at 5 kgf / cm ² / s, and the change of the liquid pressure was completed 0.6 seconds after the change of the gas pressure was completed. The time required to change the liquid pressure and the gas pressure was about 2.6 seconds, and the length of the unsteady portion coil during that time was about 4.3 m.

In the comparative example, the change of the fluid pressure and the gas pressure were started at the same time, and the change of the gas pressure was finished 0.4 seconds after the completion of the change of the fluid pressure. The pressure increasing rates of the liquid pressure and the gas pressure are the same as the conditions of the present invention.

Table 2 shows the occurrence of uneven gloss on the coil after temper rolling. As shown in the table, in the example of the present invention, there was no gloss unevenness in the non-stationary part and the rear coil, and the result was good. The elongation percentage of the leading coil and the trailing coil was 0.7%, which was the target.

In the comparative example, the average droplet diameter became 50 μm or more during rolling of the unsteady portion, and spot-like gloss unevenness occurred on the surface of the rolling roll. The gloss unevenness was transferred to the coil, and the irregular portion and the subsequent coils showed uneven gloss over the entire length.

[0046]

According to the present invention, it is possible to stably roll a stainless steel strip having excellent gloss even while changing the spraying amount of the temper rolling agent. Therefore, even in continuous rolling performed by connecting coils, a high-quality stainless steel strip can be rolled without stopping the line, and economic effects such as an improvement in production efficiency and an improvement in yield can be expected.

[Brief description of the drawings]

FIG. 1 is a graph schematically showing a pressure change when a gas pressure and a liquid pressure are simultaneously changed.

FIG. 2 is a schematic diagram schematically showing a temper rolling apparatus according to the method of the present invention.

FIGS. 3A and 3B are schematic diagrams for explaining the method of the present invention. FIG. 3A shows a case where the spray amount is reduced, and FIG. 3B shows a case where the spray amount is increased.

FIG. 4 is a graph schematically showing an example of a change in a spraying amount of a temper rolling agent and a change in a droplet diameter when a liquid pressure and a gas pressure are changed in the method of the present invention.

FIG. 5 is a sectional view showing an example of a nozzle used in the present invention.

[Explanation of symbols]

1: temper rolling mill, 2: work roll, 3: nozzle, 4:
Stainless steel strip, 5: gas pressure setting device, 6: hydraulic pressure setting device, 7: flow rate calculation device, 8: setting change instruction device, 9: tracking device, 10: first injection pipe, 11: second injection pipe, 12: temper rolling agent, 13: gas, 14: droplet.

Claims (1)

[Claims] 1. A temper rolling method in which a temper rolling agent is formed by mixing gas and spraying fine droplets on an annealed stainless steel strip after cold rolling, and the temper rolling is performed during temper rolling. When increasing the spraying amount of the temper rolling agent, the pressure of the gas is increased, then increasing the liquid pressure of the temper rolling agent to the target spraying amount, and when decreasing the spraying amount, the hydraulic pressure is increased. And then reducing the pressure of the gas to achieve a target spray amount.