JP2000351002A - Hot rolled steel strip manufacturing method and finish tandem rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel strip having a required quality by performing finish rolling for a respective steel strip corresponding to the quality required for the steel strip. SOLUTION: A finish tandem rolling mill 20 is provided with plural lubrication oil tanks 7a-7c, a spray water tank 5, a spray water cooling device 4 and a spray water pump 6. A mixing device 2 connected to the lubrication oil tanks 7a-7c respectively through gear pumps 8a-8c and plural spray nozzles 3, which are connected with the mixing devices and arranged to the inlet side of rolling stands, are arranged to one stand or more. The water in the spray water tank 5, is sent into the mixing device 2 through the spray water cooling device 4 and the spray water pump 6. By this method, for a respective hot rolling steel strip and corresponding to the quality required for the hot rolled steel strip, a mixing ratio of the lubrication oils of two or more kinds is changed, the rolling oil consisting of the composition-changed lubrication oil and water is supplied to one or more rolling stands, thus, finish rolling is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot-rolled steel strip which is subjected to finish rolling while supplying rolling oil, and a tandem rolling mill for finishing. The present invention relates to a method for producing a hot-rolled steel strip having a good surface such as steel and stainless steel and a high r-value hot-rolled steel strip excellent in formability, and a finish tandem rolling mill.

[0002]

2. Description of the Related Art Hot-rolled steel strips are usually prepared by heating a slab obtained by continuous casting in a heating furnace and then hot-rolling the steel to a thickness of 20 to 50 mm.
It is manufactured by roughly rolling into a sheet bar of a certain degree, finishing and rolling to a predetermined thickness at a plurality of rolling stands, cooling, adjusting to a predetermined material, and winding up in a coil shape.

[0003] In this finish rolling, a hot-rolled steel strip according to required quality characteristics is manufactured by performing rolling while supplying rolling oil. For example, it is possible to manufacture a high r-value stainless steel strip excellent in formability by lowering the coefficient of friction, or to manufacture a hot-rolled steel strip having a good surface by preventing seizure of a roll and a material to be rolled. Proposed. The important quality characteristics required for a hot-rolled stainless steel strip are two points: a good surface and a high r-value steel strip excellent in formability.

For example, Japanese Patent Application Laid-Open No. 9-235621 discloses that
A ferritic stainless steel slab of a specific composition is heated to a specific temperature, and the final pass of finish rolling and the preceding pass are performed under lubrication conditions with a reduction of 20% or more and a friction coefficient of 0.25 or less, respectively. High r with excellent moldability
A method for producing a ferritic stainless steel containing Ti is disclosed.

As a rolling oil capable of obtaining a good surface, for example, a lubricating oil containing the following S and water are mixed, and the mixture is supplied as a predetermined concentration of a rolling oil to the entrance of a rolling stand to finish rolling. Has been proposed. JP-A-5-17927
No. 6 discloses that a base oil composed of mineral oil and fat having a molecular weight of 500 or more contains 20 to 70 wt% of a dialkyl polysulfide having an S content of 30 wt% or more and 3 to 10 wt% of a phosphite.
A lubricating oil of an incorporated composition is disclosed.

JP-A-6-33085 discloses that an ester of a fatty acid containing 15% by weight or more of a fatty acid having 20 or more carbon atoms and a polyhydric alcohol is used as a lubricating component, and an aromatic amine salt of an organic acidic phosphoric acid ester is used. A lubricating oil having a composition comprising 〜5% by weight and 1-20% by weight of an organic sulfur compound having a sulfur content of 5% by weight or more is disclosed. However, the composition of the lubricating oil used for the rolling oil at a predetermined concentration depends on the quality characteristics of a specific hot-rolled steel strip by mixing mineral oil, animal and vegetable oil, and synthetic oil, or mixing two or more synthetic oils. Because they were combined, they were not always compatible with hot rolled steel strips of different quality characteristics.

In conventional finish rolling, it takes time to switch to a lubricating oil of another composition. Therefore, lubricating oil having a different composition is used for each sheet bar in accordance with the quality characteristics required for the hot-rolled steel strip. The finish rolling could not be performed with the used rolling oil of a predetermined concentration. For this purpose, for example, Japanese Patent Application Laid-Open No. 5-179
No. 276 or JP-A-6-33085 has a lubricating oil composition that can roll the surface of a thin stainless steel strip or a hot-rolled steel strip such as SUS434 satisfactorily, but has excellent formability due to its large friction coefficient. There was a problem that it was difficult to produce a high r-value hot rolled steel strip.

Further, even if an attempt is made to keep the friction coefficient small by using rolling oil in the finish rolling, the surface roughness of the work roll increases and the friction coefficient increases with the progress of rolling.
There is also a problem that a high r-value hot rolled steel strip having excellent formability cannot be stably manufactured. Furthermore, finish endless rolling, in which the preceding and succeeding materials of the sheet bar after rough rolling are joined and finish rolling is performed, is capable of high yield and stable rolling because there are few unsteady portions, but high r value. A surface with a finish plate thickness of about 4.0 mm to be bonded to a surface with a finish plate thickness of about 1.0 mm that should have a good surface. If a hot-rolled steel strip such as SUS434 is to be joined side-by-side, the same problem as described above occurs, so that there is also a problem that the expansion of the application of finish endless rolling is hindered.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a finish rolling for each hot-rolled steel strip according to the quality characteristics required for the hot-rolled steel strip. It is an object of the present invention to provide a method capable of producing a hot-rolled steel strip having required quality characteristics by applying the method. Another object of the present invention is to provide a method for manufacturing a hot-rolled steel strip in which a change in the coefficient of friction between a work roll and a material to be rolled with the progress of rolling is small.

[0010] It is still another object of the present invention to provide a manufacturing method applicable to finish endless rolling.

[0011]

According to the present invention, there are provided the following:
It is the described invention. The invention according to claim 1 is a method for producing a hot-rolled steel strip, in which a slab obtained by continuous casting is hot-rolled roughly and subjected to finish rolling at a plurality of rolling stands to obtain a hot-rolled steel strip. For each hot-rolled steel strip, the lubricating oil composition is changed by changing the mixing ratio of at least two types of lubricating oils according to the quality characteristics required for the hot-rolled steel strip, and the lubricating oil composition is changed. A hot rolling steel strip, wherein a rolling oil comprising water and water is supplied to at least one of the plurality of rolling stands and subjected to finish rolling.

According to a second aspect of the present invention, there is provided a method of manufacturing a hot-rolled steel strip in which a slab obtained by continuous casting is hot-rolled roughly and subjected to finish rolling at a plurality of rolling stands to obtain a hot-rolled steel strip. In at least one of the plurality of rolling stands, at least one rolling stand calculates a friction coefficient, according to the deviation between the friction coefficient and a target value, so that the friction coefficient is equal to or less than a target value, at least two types of The lubricating oil composition is changed by changing the mixing ratio of the lubricating oil, and the rolling oil composed of the lubricating oil with the changed lubricating oil composition and water is supplied to the rolling stand whose friction coefficient has been calculated among the plurality of rolling stands. And subjecting it to finish rolling.

According to a third aspect of the present invention, the at least two
One of the lubricating oils is a synthetic ester containing no S,
The invention according to claim 1 or 2, wherein the other is a sulfurized ester or polysulfide. The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the finish rolling is performed by sequentially joining the sheet bars after the rough rolling.

According to a fifth aspect of the present invention, a finishing tandem rolling mill having a plurality of rolling stands is provided with a plurality of lubricating oil tanks storing different lubricating oils and a spray water tank storing spray water. A mixing device that mixes the lubricating oil stored in at least two of the plurality of lubricating oil tanks with the spray water stored in the spray water tank to produce rolling oil; and the mixing device. And a spray nozzle for spraying the rolling oil obtained in (1) is provided on at least one of the plurality of rolling stands.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the Cr content is 9.0 wt%.
It is suitable for a method for producing a hot-rolled steel strip containing Cr having a content of 18.0 wt% or less and a finishing tandem rolling mill, and among them, a ferritic, austenitic, and martensitic stainless steel strip having a Cr content of 10.5 wt% or more. It is preferred to do so.

FIG. 1 shows an example of a hot rolling facility to which the present invention is applied, and FIG. 2 shows an arrangement of spray nozzles used in the present invention. Here, 1 is a work roll, 2 is a mixing device, 3 is a spray nozzle, 4 is a spray water cooling device, 5
Is a spray water tank, 6 is a spray water pump, 7a, 7b,
7c is a lubricating oil tank, 8 is a gear pump, 9 is a steel strip, 20 is a finishing tandem rolling mill, 21 is a row of rough rolling mills, 22 is a heating furnace, 24 is a sheet bar coiler, 25 is a joining device, and 26 is a load cell. .

The finishing tandem rolling mill 20 of the present invention includes a plurality of lubricating oil tanks 7a, 7b, 7c, a spray water tank 5, a spray water cooling device 4, and a spray water pump 6 in the hot finishing tandem rolling mill 20. , A plurality of lubricating oil tanks 7a,
A mixing device 2 connected to gears 7b and 7c via gear pumps 8a, 8b and 8c, respectively, and a plurality of spray nozzles 3 connected to the mixing device 2 and arranged on the inlet side of the rolling stand, are connected to at least one rolling stand. It is characterized by being provided in. The water in the spray water tank 5 is sent to the mixing device 2 through the spray water cooling device 4 and the spray water pump 6.

With this configuration, the composition of the lubricating oil is changed by changing the mixing ratio of at least two types of lubricating oils in accordance with the quality characteristics required for the hot-rolled steel strip for each hot-rolled steel strip. Rolling oil consisting of lubricating oil with changed oil composition and water,
Finish rolling can be performed while supplying to at least one rolling stand. For this reason, even for each sheet bar, or a lubricating oil with a composition with excellent seizure resistance,
Since it can be used as a lubricating oil having a composition with low friction characteristics, it can be used for hot-rolled steel strip with good surface and high r.
Value hot-rolled steel strip can be manufactured.

The rolling oil used in the present invention is prepared by mixing a lubricating oil whose composition has been changed and water as described below to a predetermined concentration, and supplying the mixture to the entrance of the finishing stand. The mixing device 2 is a device that mixes two or more different types of lubricating oil and water to obtain a predetermined concentration of rolling oil, and has an orifice nozzle diameter of about 6 to 10 mm. The spray nozzle 3 sprays a predetermined concentration of rolling oil, and can use a flat type to uniformly spray in the roll barrel direction. The spray water cooling device 4 is a device for controlling the temperature of water, and a normal device using a refrigerant is used. Although three lubricating oil tanks 7a to 7c are shown,
One or more lubricating oils may be stored. The gear pump 8 controls the rotation of the gear so that a predetermined amount of lubricating oil can be supplied to the mixing device 2 from the lubricating oil tanks 7a to 7c.

The sheet bar coiler 24 winds the rolled sheet bar, and the joining device 25 presses the preceding material and the following material and joins them by induction heating. It is desirable to provide the sheet bar coiler 24 and the joining device 25. Further, in the present invention, the friction coefficient is calculated by at least one rolling stand, and the composition of the lubricating oil is changed by changing the mixing ratio of at least two types of lubricating oils so that the friction coefficient is equal to or less than the target value. By applying finish rolling while supplying rolling oil composed of lubricating oil and water whose lubricating oil composition has been changed to a rolling stand whose friction coefficient has been calculated, even if the surface roughness of the work roll increases with the progress of rolling. Since an increase in the coefficient of friction can be suppressed, a high r-value hot-rolled steel strip having excellent formability can be stably manufactured.

Here, the friction coefficient μai of the i-stand used in the present invention is obtained by inputting the measured value of the rolling load, the sheet thickness, the tension, and the like into the equation (1) based on, for example, the equation of Yanagimoto and Ohno. Ask. μai = F (kf, H, h, T ₁ , T ₀ , D, P) (1) where Kf: deformation resistance, H: input side plate thickness, h: output side plate thickness,
T ₁ : entry side tension, T ₀ : exit side tension, P: unit width load, D: roll diameter.

In the present invention, as shown in FIG. 3, the mixing ratio of the lubricating oil is controlled during rolling using the difference between the target friction coefficient μmi of each stand and the actually measured friction coefficient μai derived from the above equation. It has been like that. In the figure, Qe, Q
r and Qp are the ratio of the lubricating oil E to the total oil amount Qo, the ratio of the lubricating oil R to the total oil amount Qo, and the ratio of the lubricating oil P to the total oil amount Qo, respectively.
Is a change ratio of the lubricating oil E to the total oil amount Qo.

Se, Sr and Sp are the amounts of lubricating oil actually supplied to the stand. Note that the total oil amount Qo is separately determined in consideration of the type of steel and rolling conditions. For example, depending on the quality characteristics of each hot-rolled steel strip, the initial mixing ratio of the lubricating oil in each stand is such that the high-r-value hot-rolled steel strip increases the proportion of the lubricating oil E and the hot-rolled steel with a good surface. In the band, the ratio of the lubricating oil R or the lubricating oil P is set high and is determined in advance using a table or the like. When rolling a high r-value hot-rolled steel strip, the friction coefficient is calculated at the time of rolling, and when the calculated measured friction coefficient is larger than the target friction coefficient, a coefficient K is calculated as the deviation between the measured friction coefficient and the target friction coefficient. The value multiplied by (K is a gain) is used as a change ratio to the total oil amount Qo of the lubricating oil E, and the mixing ratio of the lubricating oil E is changed so that the actually measured friction coefficient becomes equal to or less than the target friction coefficient.

As the lubricating oil used in the present invention, it is preferable that one of the lubricating oils is a synthetic ester containing no S, and the other lubricating oil is a sulfurized ester or polysulfide. By changing the content of the sulfide ester or polysulfide relative to the S-free synthetic ester within the range of 0 to 100 wt%, when the mixing ratio of the S-free synthetic ester is increased, the friction coefficient can be reduced. A high r-value hot rolled steel strip excellent in formability can be manufactured.

On the other hand, when the mixing ratio of the sulfide ester or the polysulfide is increased, the occurrence of seizure can be prevented, so that there is an effect that a hot-rolled steel strip having a good surface can be manufactured. The reason is considered as follows. The lubricating oil containing a synthetic ester containing no S as a main component is partially decomposed into C and H in the roll bite, and most of the lubricating oil remains in a liquid state to prevent contact between the roll and the hot-rolled steel strip. As a result, a high r-value hot-rolled steel strip excellent in formability can be manufactured, but since S is not contained, the effect of preventing seizure between the roll and the material is small and the surface is easily roughened.

On the other hand, lubricating oils containing S, such as sulfide esters and polysulfides, are thermally decomposed by a roll bite, and since S exhibits an extreme pressure effect in the roll bite, the effect of preventing seizure between the roll and the material is great. Although a hot-rolled steel strip having a clean surface can be produced, it is difficult to produce a high-r-value hot-rolled steel strip having excellent formability due to a large friction coefficient.

The above lubricating oil contains up to 15% by weight of methyl methacrylate for improving the adhesion of the main component to the roll.
You may make it contain. Since methyl methacrylate has a high viscosity, clogging in a pipe is liable to occur at an added amount higher than that. Synthetic esters, sulfide esters, and polysulfides containing no S used in the present invention have a large effect of reducing the coefficient of friction or preventing seizure.
Is preferable.

[0028]

[Table 1]

The lubricating oil shown in Table 1 is premixed with about 5 wt% of high viscosity methyl methacrylate to enhance the adhesion to the roll. (Basic Experiment) Here, the effect on the coefficient of friction when the finish rolling is performed using the lubricating oils shown in Table 1 will be described.

C obtained by continuous casting: 0.07 wt%, C
r: 16.5wt%, Ti: 0.002wt%, Nb: 0.003wt%, balance F
30mm thick sheet bar of ultra low carbon ferritic stainless steel (SUS430) composed of e and unavoidable impurities
1000 mm) was finish-rolled to a thickness of 3.0 mm by the finishing tandem rolling mill of the present invention shown in FIG. At that time, the composition of the lubricating oil was changed by changing the mixing ratio of the lubricating oil as shown in FIG.
When the finish rolling was performed while the lubricating oil and water were mixed and supplied to the first stand (F1) as a rolling oil having a concentration of 1.5 wt%, the actually measured friction coefficient of the rolling stand was determined from the above equation (1). .

The results of the actually measured friction coefficient are also shown in FIG. After the end of the rolled material bites into the first stand, the lubricating oil R starts when the length of the steel strip on the seventh stand (F7) outlet side reaches 100 m.
Is mixed with water and supplied as rolling oil with a concentration of 1.5 wt% (500 c
(c / min / 1000 mm width), the friction coefficient is slightly lower than when no rolling oil is supplied. When lubricating oil E is mixed with water and supplied as 1.5 wt% rolling oil Has a remarkably reduced friction coefficient.

The lubricating oil P is mixed with water to a concentration of 1.5 wt.
%, The coefficient of friction is almost the same as when no rolling oil is supplied. From these results, it can be seen that the friction coefficient can be controlled by changing the mixing ratio of the lubricating oil mainly composed of the sulfide ester or the polysulfide to the lubricating oil E mainly composed of the synthetic ester containing no S to 0 to 100 wt%.

According to the present invention, the finish rolling can be smoothly performed even when the preceding material and the following material of the sheet bar after the rough rolling are joined. The reason is as follows. Finish-endless rolling, in which the sheet bar after rough rolling is joined and finish-rolled, is used for finishing with a finished plate thickness of about 4.0 mm that should have a high r value and with a finished plate thickness of about 1.0 mm that should have a good surface. Even when joining or joining a hot-rolled steel strip such as SUS430, which should have a high r-value, and a hot-rolled steel strip, such as SUS434, which should have a good surface, side by side, According to the quality characteristics required for the steel strip, at least two kinds of lubricating oils are mixed to change the composition of the lubricating oil, and at least one rolling oil composed of the lubricating oil having the changed lubricating oil composition and water is used. This is because a hot-rolled steel strip having a clean surface and a high r-value hot-rolled steel strip having excellent formability can be manufactured by supplying the steel strip to one rolling stand.

Even if the surface roughness of the work roll increases with the progress of the rolling in the endless finishing rolling, at least one rolling stand calculates the friction coefficient and at least two types of the friction coefficients are set so that the friction coefficient becomes equal to or less than the target value. The composition of the lubricating oil is changed by mixing the above-mentioned lubricating oils, and the rolling oil composed of the lubricating oil with the changed lubricating oil composition and water is supplied to the rolling stand whose coefficient of friction has been calculated, and then subjected to finish rolling. This makes it possible to suppress an increase in the coefficient of friction and to produce a high r-value hot-rolled steel strip having excellent formability stably.

[0035]

EXAMPLES The lubricating oils used in the examples described below are shown in Table 1.
The lubricating oil E is mainly composed of a synthetic ester containing no S, the lubricating oil R is mainly composed of a sulfide ester, and the lubricating oil P is mainly composed of polysulfide. However, the lubricating oil P was used only in the basic experiment and was not used in the examples.

(Example 1) C: 0.07 wt%, Cr: 16.5 wt
%, Ti: 0.002wt%, Nb: 0.003wt%, the balance being Fe and stainless steel (SUS4
30) 3 slabs (200mm thickness, 1000mm width, 5000mm length) are heated to 1150 ° C, roughly rolled into a 30mm thick sheet bar, rolled up with a sheet bar coiler, and the leading and trailing materials are separated. Joining with an induction heating type joining device, changing the running thickness with a finishing mill consisting of 7 stands, the first one with a thickness of 4 mm
Then, the second one was subjected to finish endless rolling to a thickness of 2.0 mm and the third to a thickness of 4 mm, and was wound.

The work roll diameter of the rough rolling stand was 1300 mm, the barrel length was 2200 mm, the work roll diameter of the finishing roll stand was 700 mm, and the barrel length was 2000 mm. On the finishing side, descaling was performed at a pressure of 15 MPa. that time,
In the example of the present invention, as shown in FIG. 5B, the composition of the lubricating oil is changed by changing the mixing ratio of the lubricating oil E and the lubricating oil R according to the quality characteristics required for the hot-rolled steel strip. Rolling oil mixed with lubricating oil and water was supplied to all stands.

That is, the first and third hot-rolled steel strips to be made into a high r-value hot-rolled steel strip were prepared by mixing lubricating oil in which lubricating oil E was made 100 wt% and water to make rolling oil having a concentration of 1.5 wt%. In the second thin-finished steel strip that should be a good hot-rolled steel strip, lubricating oil E was
t%, lubricating oil with lubricating oil R of 70 wt% and water are mixed,
Rolling oil with a concentration of 1.5 wt% was used. On the other hand, in the conventional example, FIG.
(A) As shown in FIG.
The lubricating oil in wt% and water were mixed to form a rolling oil having a concentration of 1.5 wt%, and all three were finish-rolled with lubricating oil having the same composition. Other conditions were the same as those of the invention example.

In the conventional example, the lubricating oil E was 70 wt% and the lubricating oil R was 30 wt%.
The reason for wt% is to match the general composition of conventional oils. Continuous annealing to the hot rolled steel strip of the above-mentioned invention example and the conventional example
After pickling (annealing temperature 900 ° C.), the surface was observed. As a result of surface observation, the surfaces of the first to third hot-rolled steel strips of the present invention were good, whereas seizure occurred in the second hot-rolled steel strip of the conventional example. After washing, it was necessary to grind the surface. Further, since the roll surface was roughened by the second rolling in the conventional example, the scale was cut into the third hot-rolled steel strip, and the grinder had to be cleaned.

Then, further cold-rolled to a thickness of 0.9 mm,
Continuous annealing at 880 ° C. for 10 seconds was performed to obtain a cold-rolled steel strip. Using this cold-rolled steel sheet as a test material, the r value was measured by the following method.
r value: After applying 15% tensile strain using JIS13 test piece,
The average r value was determined by a three-point method. The r values of the first and third lines of the invention example were 1.45 and 1.00, respectively.

The r values of the first and third lines of the conventional example were 1.20 and 0.75, respectively. From the results of the above surface observation and measurement of the r value, according to the quality characteristics required for the hot-rolled steel strip, at least two types of lubricating oils are mixed to change the lubricating oil composition, and the lubricating oil and water are mixed. It is understood that by performing finish rolling while supplying the obtained rolling oil to at least one rolling stand, a hot-rolled steel strip having a higher r value and a hot-rolled steel strip having a good surface can be manufactured as compared with the conventional example.

Example 2 C: 0.004 wt%, Cr: 19.5 wt%
%, Mo: 2.0wt%, Ti: 0.002wt%, Nb: 0.003wt%,
Slab of ferritic stainless steel (SUS434) consisting of the remainder and unavoidable impurities (200 mm thick, 1000 mm wide, 5000
mm length) and a SUS430 slab having the same composition and dimensions as in Example 1 were heated to 1150 ° C, roughly rolled into a 30 mm thick sheet bar, wound up with a sheet bar coiler, and the first was SUS430, 2
The first material was SUS434, and the third material was SUS430. The preceding material and the succeeding material were sequentially joined by an induction heating type joining device, and finish-endless rolling was performed.

At this time, in the example of the present invention, as shown in FIG. 6, depending on the quality characteristics required for the hot-rolled steel strip, the lubricating oil E
In addition, two types of lubricating oils having different lubricating oils R were mixed to change the composition of the lubricating oil, and a rolling oil in which the lubricating oil and water were mixed was supplied to all the stands. That is, the first and third steel strips to be made into high r-value hot-rolled steel strip were prepared by mixing lubricating oil in which lubricating oil E was 100 wt% and water to make rolling oil having a concentration of 1.5 wt%, and having a good surface heat resistance. In a second SUS434 having a thin finish to be formed into a rolled steel strip, lubricating oil E having a lubricating oil E of 0 wt% and lubricating oil R of 100 wt% was mixed with water to obtain a rolling oil having a concentration of 1.5 wt%. Other conditions were the same as in Example 1.

On the other hand, in the conventional example, as shown in FIG. 5 (a), lubricating oil E of 70 wt% and lubricating oil R of 30 wt% were mixed with water to obtain a rolling oil having a concentration of 1.5 wt%. Since the composition of the lubricating oil could not be changed, all three were finish-rolled with the lubricating oil having the same composition. Other conditions were the same as those of the invention example. Continuous annealing and pickling (annealing temperature 900 ° C.) were performed on the hot-rolled steel strips of the above-mentioned invention examples and the conventional examples, and the surfaces were observed.

As a result of surface observation, the surface of the SUS434 after the second pickling of the present invention was good. Of course, the surfaces of the first and third hot rolled steel strips of the present invention were also good. on the other hand,
In the conventional hot-rolled steel strip, seizure occurred in the second SUS434 and the scale got into the scale, and after the pickling, the grinder had to be cleaned. Further, since the roll surface was roughened by the second rolling in the conventional example, the scale was cut into the third hot-rolled steel strip, and the grinder had to be cleaned.

Then, further cold-rolled to a thickness of 0.9 mm,
Continuous annealing at 880 ° C. for 10 seconds was performed to obtain a cold-rolled steel strip. Using this cold-rolled steel sheet as a test material, the r value was measured in the same manner as in Example 1. The first and third r values of the invention example are respectively
They were 1.45 and 1.00. The first and third r of the conventional example
The values were 1.20 and 0.75, respectively.

From the results of the above surface observation and measurement of the r value,
Depending on the quality characteristics required for the hot-rolled steel strip, at least two
By changing the composition of the lubricating oil by mixing the kinds of lubricating oils, by performing the finish rolling while supplying the rolling oil obtained by mixing the lubricating oil with the changed lubricating oil composition and water to at least one rolling stand, It can be seen that a hot-rolled steel strip having a higher r value and a hot-rolled steel strip with a clean surface can be manufactured as compared with the conventional example.

Example 3 The same components and dimensions as in Example 1 were used.
The SUS430 slab is heated to 1150 ° C, roughly rolled into a 30 mm thick sheet bar, wound up by a sheet bar coiler, and the preceding and succeeding materials are joined by an induction heating type joining device, consisting of 7 stands All of the three rolls were subjected to finish endless rolling to a thickness of 3.0 mm by a finish rolling mill and wound up.

At this time, in the example of the present invention, the final stand (the seventh stand) is used.
Calculate the coefficient of friction at the stand) and set the coefficient of friction to the target value of 0.15
The lubricating oil E and the lubricating oil R were mixed at the ratio shown in FIG. 7 to change the composition of the lubricating oil as follows, and the lubricating oil and water were mixed at a concentration of 1.5 wt%. Rolling oil was supplied to the final stand. On the other hand, as a conventional example, after the steel strip has been bitten by the final stand (seventh stand), as shown in FIG. 5 (a), lubricating oil E and lubricating oil R having lubricating oil R of 30 wt% and water are mixed together with water. Was mixed to obtain a rolling oil having a concentration of 1.5 wt%. Other conditions were the same as those of the invention example.

FIG. 8 shows a change in the coefficient of friction between the invention example and the conventional example. From this result, even if the rolling progresses in the present invention, it is possible to stably achieve a friction coefficient of 0.15 or less, but in the conventional example, the surface roughness of the work roll increases with the progress of the rolling and the friction coefficient increases. . In addition, continuous annealing and pickling (annealing temperature 900
℃) and cold-rolled to a sheet thickness of 0.9 mm,
Continuous annealing at 10 ° C. for 10 seconds was performed to obtain a cold-rolled steel strip. Using this cold-rolled steel sheet as a test material, the r value was measured in the same manner as in Example 1.

Table 2 shows the measurement results of the r value.

[0052]

[Table 2]

From this result, the coefficient of friction was calculated in at least one rolling stand, and the composition of the lubricating oil was changed by mixing at least two types of lubricating oils so that the coefficient of friction was equal to or less than the target value. Finish rolling is performed while supplying a rolling oil obtained by mixing a lubricating oil having changed composition and water to a stand for which a friction coefficient has been calculated. It can be seen that a high r value can be obtained in

[0054]

As described above, according to the present invention,
Hot-rolled strips with good quality properties, even if hot-rolled steel strips that require different quality characteristics such as high-r-value hot-rolled steel strips with excellent formability and hot-rolled steel strips with good surfaces are adjacent Steel strip can be manufactured. In addition, even if the surface roughness of the work roll increases with the progress of rolling, the increase in the coefficient of friction can be suppressed by changing the composition of the lubricating oil. Can be manufactured.

In the endless end rolling, even if hot rolled steel strips having different quality characteristics such as a high r-value hot rolled steel strip excellent in formability and a hot rolled steel strip having a good surface are joined, A hot-rolled steel strip having good quality characteristics can be manufactured. Further, even if the surface roughness of the work roll increases with the progress of the finish endless rolling, the increase in the coefficient of friction can be suppressed, so that a high r-value hot-rolled steel strip having excellent formability can be stably manufactured.

Since the objects of the endless rolling can be expanded, it is possible to manufacture a hot-rolled steel strip with a stable operation and a high yield.

[Brief description of the drawings]

FIG. 1 is a schematic layout view of a hot rolling facility used in the present invention.

FIG. 2 is a schematic layout diagram of a spray nozzle used in the present invention.

FIG. 3 is a flowchart of friction coefficient control used in the present invention.

FIG. 4 is a graph showing the effect of the lubricating oil used in the present invention.

FIG. 5 (a) is a graph showing a change in lubricating oil composition of a conventional example. FIG. 5B is a graph showing a change in the lubricating oil composition of the example of the present invention.

FIG. 6 is a graph showing another change of the lubricating oil composition of the example of the present invention.

FIG. 7 is a graph showing another change of the lubricating oil composition of the example of the present invention.

FIG. 8 is a graph showing the effect of the present invention on the coefficient of friction.

[Explanation of symbols]

 1: Work roll 2: Mixing device 3: Spray nozzle 4: Spray water cooling device 5: Spray water tank 6: Spray water pump 7a, 7b, 7c: Lubricating oil tank 8a, 8b, 8c: Gear pump 9: Steel strip 20: Finishing tandem rolling mill 21: Rough rolling mill row 22: Heating furnace 24: Sheet bar coil 25: Joining device 26: Load cell

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Kitahama 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Inventor Masao Yarida 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture (72) Inventor Shinzo Uchimaki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture F-term (reference) 4E002 AA07 AD02 AD04 AD07 BA01 BB09 BC08 BD05

Claims (5)

[Claims] 1. A method for producing a hot-rolled steel strip, wherein a slab obtained by continuous casting is hot-rolled roughly and subjected to finish rolling at a plurality of rolling stands to obtain a hot-rolled steel strip. For each band, depending on the quality characteristics required for the hot-rolled steel strip, change the lubricating oil composition by changing the mixing ratio of at least two types of lubricating oils, and change the lubricating oil composition to a lubricating oil and water. A finishing oil is supplied to at least one of the plurality of rolling stands for finish rolling. 2. A method for manufacturing a hot-rolled steel strip, wherein a slab obtained by continuous casting is hot-rolled roughly and subjected to finish rolling at a plurality of rolling stands to obtain a hot-rolled steel strip. A friction coefficient is calculated by at least one of the rolling stands among the stands, and a mixing ratio of at least two types of lubricating oils is determined according to a deviation between the friction coefficient and a target value such that the friction coefficient is equal to or less than a target value. Changing the lubricating oil composition by changing the lubricating oil composition and supplying the rolling oil composed of the lubricating oil composition and water to the rolling stand having a calculated coefficient of friction among the plurality of rolling stands to perform finish rolling. A method for producing a hot-rolled steel strip. 3. The method of claim 1, wherein one of the at least two lubricating oils is
The method for producing a hot-rolled steel strip according to claim 1 or 2, wherein the synthetic ester containing no S is used, and the other is a sulfurized ester or polysulfide. 4. The method for producing a hot-rolled steel strip according to claim 1, wherein the sheet bars after the rough rolling are sequentially joined and the finish rolling is performed. 5. A finishing tandem rolling mill having a plurality of rolling stands, comprising: a plurality of lubricating oil tanks for storing different lubricating oils; and a spray water tank for storing spray water. A mixing device that mixes the lubricating oil stored in at least two of the lubricating oil tanks with the spray water stored in the spray water tank to produce rolling oil; and the rolling device obtained by the mixing device. A finishing tandem rolling mill, wherein a spray nozzle for spraying oil is provided on at least one of the plurality of rolling stands.