JPH0471702A - Device and method for manufacturing cold rolled strip of stainless steel - Google Patents

Abstract

PURPOSE:To efficiently manufacture a cold rolled strip of stainless steel with mirror finished face gloss by dividing the function of tandem rolling into three. CONSTITUTION:This is a device for manufacturing cold rolled strip of stainless steel which is provided by combining the following mills: A 1st stage cold rolling mill which is succeedingly provided to a pickling process and with which surface hardening rolling for preventing oil pit is done, a 2nd cold rolling mill with which the strip is finished into an objective dimension by performing high draft rolling to the surface hardened strip which is rolled with the 1st stage cold rolling mill while preventing heat scratch and a 3rd stage cold rolling mill with which finish rolling for improving the smoothness of surface is done to the strip which is rolled into the objective dimension with the 2nd stage cold rolling mill and which is connected to a finish annealing and pickling process.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides an apparatus and method for producing cold-rolled stainless steel strips having excellent surface gloss and low-chromium cold-rolled steel strips having a chromium content of 13% chromium or less. Regarding.

(Prior art) Conventionally, cold-rolled stainless steel strips are produced by box-shaped or continuous annealing, pickling, and cold-rolling in a Sendzimir mill using small-diameter work rolls with a diameter of 15 mm or less. After finishing annealing + pickling or finishing bright annealing, the reduction ratio is 0.5.
~1.5% temper rolling was performed and manufactured. However, cold rolling in such a Sendzimir mill does not allow high-speed rolling and is not very efficient.

Therefore, in recent years, a manufacturing method using a highly productive cold tandem mill instead of the Sendzimir mill has been adopted.

However, when rolling is performed using a cold tandem rolling mill with work rolls with a diameter of 150 mm or more,
Compared to the conventional Sendzimir mill having small diameter rolls, the resulting cold-rolled stainless steel strip has a disadvantage in that its surface gloss is inferior.

Conventionally, there are the following techniques for obtaining surface gloss using such a cold tandem rolling mill.

(1) As disclosed in JP-A-63-119908, the roll diameter of the final stand is 400 φl or less. (2) As disclosed in JP-A-62-137107, the roll diameter is 400 φl or less. (3) As disclosed in JP-A No. 63-290602, the roughness of the mother copper strip is controlled by rolling without lubrication as a pretreatment for tandem rolling. (4) As disclosed in JP-A No. 61-49701, tandem rolling is followed by rolling in a small-diameter Sendzimir mill, but it is still not possible to obtain the same level of surface gloss as when all passes are rolled in a Sendzimir mill. Moreover, since it is merely an attempt to secure surface gloss at the expense of efficiency, it is not sufficient from a practical point of view (problem to be solved by the invention).Therefore, the inventors of the present invention have developed a method that combines conventional Sendzimir rolling and tandem rolling. A comparative study was conducted from the viewpoints of production efficiency and mirror finish.

For example, when producing stainless cold rolled steel strip with a width of 1000 mm or more, tandem rolling with work rolls with a diameter of 250 to 600 m11 and high speed rolling is required.
Compared to Sendzimir rolling, which uses work rolls of +uw and rolls at a relatively low speed, there is a problem in that the glossiness of the product surface is lower.

As is already known, the reduction in gloss of cold rolled steel strip during tandem rolling is mainly due to three causes.

(1) Mechanical descaling methods such as shot blasting are also used when pickling copper strips, but the unevenness during pickling (hereinafter referred to as pickling pits), including the unevenness of shot beads, Remains even after rolling.

(2) During cold rolling, a large amount of rolling oil gets caught up between the rolls and the copper strip, and oil pins that occur when the rolling oil partially deforms the surface crystals of the copper strip remain even after rolling.

(3) During cold rolling, the rolling oil film in the roll bite becomes thinner, causing direct contact between the roll and the copper strip in some areas, causing heat scratches due to a kind of seizure phenomenon, which remain even after rolling.

Until now, pickling pits have been prevented by finely regulating the surface roughness of the matrix band. After pickling, the surface roughness of the mother copper strip is controlled by rolling without lubrication to eliminate or reduce pickling pits.

However, only by smoothing the mother copper strip, the pickling pits are lightly molded, but the problems of oil pits and heat scratches are not fully resolved. This is because these are largely caused by the viscosity of rolling oil, roll diameter, rolling speed, rolling load, etc. during the rolling process.

Generally speaking, if the rolling oil film is too thick, a fluid lubrication state will occur and oil pits will become dominant, whereas if the rolling oil film is too thin, a boundary lubrication state will occur where the oil film will partially run out and metal-to-metal contact will occur. This results in heat scratches.

In addition, oil pits mainly occur in the front bus,
Heat scratches tend to occur primarily in the rear buses. In particular, in the case of high-speed rolling, in the latter bus where the rolling load increases, as the rolling temperature increases, the critical rolling oil film thickness that causes partial oil film breakage and heat scratches tends to increase.

Therefore, when considering methods for preventing oil pits in tandem rolling, the following four types can be considered so far.

Measure A - Use small diameter rolls, use low viscosity rolling oil, and perform low speed rolling as used in small diameter Zendia mills, etc. to reduce the amount of rolling oil involved and prevent the film thickness from increasing.

Measure B - Tandem final stand only, 400 +u+
Method of adopting the following small or medium diameter rolls. For example, see Japanese Patent Application Laid-open No. 119908/1983.

Countermeasure C - As seen in JP-A No. 62-137107, the surface roughness of the work roll is changed, the roughness is made rougher in the first pass, and the oil pins that occur are ground by a roll with a rougher roughness. A method of rolling with rolls with reduced surface roughness in the latter pass to increase gloss.

Countermeasure D - As described in JP-A No. 61-49701, after tandem rolling of large diameter rolls, small diameter rolls (
A method of applying rolling by, for example, a Sendzimir mill).

However, each of these measures has the following disadvantages.

Regarding countermeasure A: In tandem rolling, the use of small diameter rolls tends to cause roll and plate slip and vibration problems during high-speed rolling, and lowering the viscosity of the rolling oil also reduces the risk of heat flanch during high-speed rolling. Low speed rolling is contrary to the original purpose of tandem high speed rolling.

Regarding Measure B: If a small diameter roll is used in the final stand of a tandem mill, as mentioned above, in the case of high-speed rolling, it is likely to cause operational problems such as slipping and vibration, and in the case of a single stand mill with reversible rolling. When the rolling oil film is thin, small-diameter rolls have the effect of smoothing out unevenness on the rope surface (hereinafter referred to as a correction effect). If there is, it is effective, but at high speeds (the final stand is the highest rolling stand), more rolling oil is involved, and the correction effect is halved.

On the other hand, if you try to improve the correction effect by lowering the viscosity of the rolling oil or reducing the supply amount of the rolling oil, the manufacturing conditions tend to suddenly shift to conditions that cause heat flanch, and the stable production area is too narrow. There is.

Regarding Measure C: Grinding the oil pits with coarse rolls will reduce the number of oil pits to some extent, but in the case of tandem rolling, a large amount of oil pits will be generated mainly in the front pass, so there is a limit to the amount of reduction. First of all, there is little effect unless the occurrence of oil spots itself is halved.

Regarding countermeasures: Rolling 3 to 4 passes with Sendzimir rolling with small diameter rolls after tandem rolling with large diameter rolls has the effect of correcting surface irregularities and gives the same gloss as that of full pass rolling with Sendzimir rolls. Although this is the most possible method, the cold rolling process becomes two steps, which causes disadvantages such as an increase in the amount of work in progress and an extension of manufacturing lead time, and above all, there is the problem that the cost of the cold rolling process cannot be reduced. remain.

What is noticeable about these measures against oil pitting is that the measures to prevent oil pits, which occur in large quantities in tandem mills with large diameter rolls, are incomplete and that expectations are placed too high on the correction effect of small diameter rolls. It is.

In tandem rolling using large-diameter rolls, if stainless steel strip is rolled while ensuring high productivity, one or both of heat flanch and oil pits will occur, and the correction effect will be small. Therefore, it is extremely difficult to obtain a copper strip surface gloss comparable to Zendia Mill using a small diameter roll.

On the other hand, the Sendzimir mill having small diameter rolls also has the aforementioned problems of pickling pits, oil pits, and heat scratches. However, it is easy to apply rolling conditions where oil pits and heat scratches are less likely to occur, such as changing the speed and reduction rate for each rolling pass and managing the rolling oil film.
Even if it occurs, it is relatively easy to eliminate it due to the correction effect peculiar to small-diameter rolls, so it is easy to ensure the surface gloss of the copper strip. However, the drawback is that productivity is low.

Here, the object of the present invention is to provide a high speed cold rolling tandem mill having large diameter rolls without reducing production efficiency.
An object of the present invention is to provide an efficient production apparatus for cold-rolled stainless steel strips that solves the problem of deterioration of surface gloss of copper strips.

(Means for solving the problem) Therefore, the present inventor developed a conventional tandem rolling mill into three
We focused on dividing. That is, (1) the first stage cold rolling is done by hot pickling or intermediate pickling (hereinafter referred to as Hot AP).
This is done using a mill placed at the rear of the machine.

(2) The second stage cold rolling is carried out in a common steel tandem mill.
(3) The cold rolling required in the third stage is carried out in a mill placed on the finishing pickling entry side.

In this way, it has been found that by dividing the function of tandem rolling into three parts, it is possible to efficiently produce a cold-rolled stainless steel sheet strip with a specular luster, which was previously thought to be incompatible.

It is also possible to further install a preheating device placed on the inlet side of each mill and a cooling device placed before and after the mill.Q In this way, by dividing the tandem rolling mill into three parts and arranging heating and cooling devices, oil focusing can be achieved. can be prevented from occurring.

As mentioned above, the cause of oil pits is the partially softened structure of the outermost crystals of the copper strip, or the crystals that are easily deformed in crystal orientation due to rolling compression force, and rolled oil caught in large quantities during roll bite. It is generally known that this is a group of pits or pits that have been deformed by

The conventional measure to prevent oil pits has been to reduce the thickness of the rolling oil film, but as mentioned above, tandem rolling has various limitations and there are limits to how thin the oil film can be. It is.

Therefore, the present inventor conducted various studies regarding these points and obtained the following knowledge.

A) Oil pins occur mainly in the soft and unprocessed parts of the outermost crystal, but their occurrence can be significantly suppressed by hardening the surface of the copper strip or softening the inside.

Furthermore, regarding heat scratches and glossiness, the following findings were obtained.

B) The higher the rolling reduction rate in the final 1 to 2 passes, the higher the gloss level.

However, high-reduction rolling requires high-simplification and heavy-duty rolling, and high-speed rolling generates a large amount of rolling process heat. Even when the oil film is relatively thick under boundary lubrication rolling conditions, the oil film can partially run out and heat scratches are likely to occur. .

For this reason, in actual operations, the rolling reduction rate in the latter pass, which is prone to heat scratches, is limited to approximately 20% or less.
By strengthening the internal softening of the copper strip and the surface cooling of the roll or copper strip, it is possible to suppress the occurrence of heat scratches even when high-speed, high-reduction rolling is performed.

We learned that by combining these facts with conventional measures to reduce the oil film thickness, we could create a group of tandem mill rolling mills that significantly reduced the occurrence of oil pins) and heat scratches, and made the correction effect effective. The invention has been completed.

Here, the gist of the present invention is a first-stage cold rolling mill that performs surface hardening rolling to prevent oil pits, which is provided following the pickling process, and a rolling process performed by the first-stage cold rolling mill. A second stage cold rolling mill rolls the surface-hardened strip to the desired dimensions while preventing heat scratches, and the second stage cold rolling mill applies surface smoothness to the strap rolled to the desired dimensions. This is a stainless steel cold rolled steel strip manufacturing equipment that is equipped with a third stage cold rolling mill connected to the pre-process of final annealing and pickling to perform finish rolling to improve the strength of the stainless steel strip.

According to preferred LIi of the present invention, the diameter of the work roll of the second stage cold rolling mill is made larger than the diameter of the work roll of the first stage cold rolling mill, and the diameter of the work roll of the third stage cold rolling mill is The diameter of the work roll is equal to or smaller than that of the work roll of the first stage cold rolling mill.

In a more specific embodiment, the work roll diameter of the first stage cold rolling mill is 2501111 or less, the work roll diameter of the second stage cold rolling mill is more than 150 mm, preferably more than 200 + * m, and By setting the working roll diameter of the third stage cold rolling mill to 150+ll11 or less, the effects of the present invention can be exhibited more efficiently.

Furthermore, from another aspect of the present invention, by using any of the above-mentioned apparatuses, the cold rolling rate by the first stage cold rolling mill is 30% or more, and the cold rolling rate by the third stage cold rolling mill is increased by 30% or more. This is a method for manufacturing cold-rolled stainless steel strip in which the rolling speed is 100 mm/min or less. If a sufficient rolling rate can be obtained by the first and third stage cold rolling mills, the second stage cold rolling mill can be omitted.

(Operation) The present invention will now be described in further detail with reference to the accompanying drawings.

FIG. 1 is an embodiment of the invention, showing a first stage rolling mill installed in a hot pickling line.

The hot pickling device 1 is equipped with a continuous annealing furnace 9, a mechanical descaling section 11 such as a steel plate, and a pickling tank 12. The hot pickling device 1 includes, for example, a rolling I! 2 and a rope heating bag in front of it! 3 and each rolling [12
A cooling device 4 is disposed before and after the cooling device 4, respectively.

The rolling mill 2 may be of any type, such as a double type, a quadruple type, a six layer type, or a cluster type, and may be arranged in single or multiple types. Preferably, the diameter of the work rolls of the rolling mill 2 will be described later. It should be smaller than the diameter of the work rolls of the second stage rolling mill. More specifically, the working roll diameter of this rolling mill is 25
It is less than or equal to 0 so.

In FIG. 1, a hot-rolled stainless steel strip 19 is unwound from a payoff reel 5, and after its front and rear ends are cut by a shear 6, the leading and trailing steel strips are connected by welding I17.

It passes through the entrance looper 8, is heated and annealed in the continuous annealing furnace 9, passes through the cooling zone 10, and is in a state where part of the oxide scale on the surface of the copper strip is peeled off or easily peeled off in a mechanical descaling section 11 such as shot blasting. Then pickling tank 12
Completely remove scale, rinse and dry I!
13 and then passes through the output looper 14. Then the first
In the rolling mill 2, which is a cold rolling mill, cold rolling is performed at a reduction rate of 30% or more, for example, to form a surface work-hardened structure. At this time, either non-lubricated rolling or lubricated rolling may be used, and then the shear 17 is passed through the degreasing, rinsing and drying device 16.
The wire is cut at the same time and wound into a coil 20 by a ten-line reel 18.

Further, in the case of a stainless steel strip that has been punch annealed in advance, the continuous annealing furnace 9 and the cooling zone 10 may be omitted.

FIG. 2 shows a tandem rolling line incorporating a second-stage cold rolling mill according to the present invention. In FIG. 9, devices similar to those in FIG. 1 are designated by the same reference numerals.

The steel strip 19 rolled by the first-stage cold rolling mill is unwound from the payoff reel 5, and after the leading and trailing ends are cut by the roller 6, the leading and trailing copper strips are connected by the welding machine 7. . After passing through the entrance looper 8, the copper strip is heated to 200° by the heating device 3.
C or less and then rolled by a tandem mill 52 constituting the second-stage cold rolling mill. At this time, in order to harden the surface, the surface is heated by cooling devices 4 before and after each mill.
It is cooled down.

This tandem mill 52 may also be of any type, such as a double-layer type, a four-layer type, a six-layer type, or a cluster type, like the rolling mill 2 described above. The cooling device 4 may be roll cooling, water cooling using rolling oil, or the like, but is not particularly limited. The copper strip is cut by a shear 17 on the exit side and wound into a coil 20 by a tension reel 18.

Preferably, the diameter of the work rolls of the tandem mill 52 is larger than that of the first stage rolling mill, as described above, and more specifically, the diameter of the work rolls is greater than 15 mm, generally from 250 to 600 mm.

FIG. 3 shows a third stage cold rolling mill installed in the finishing pickling line.

A continuous annealing furnace 21, a pickling section 23, and a temper rolling mill 27 are disposed behind the rolling mill 62 constituting the third-stage cold rolling mill.

The steel strip 19 cold-rolled in the first stage rolling mill or the second stage rolling mill is unwound by a payoff reel 5, and the leading and trailing ends are cut by a shear 6, and the leading coil,
The trailing coil is connected by a welding machine 7, passes through an inlet looper 8, passes through a degreasing and rinsing dryer 29 for removing rolling oil used in the second stage cold rolling mill, and then passes through a third stage rolling mill. The copper strip is cold-rolled in a rolling mill 62 that makes up the mill.6 At that time, the copper strip is heated by a heating device 3, and the surface is heated by a cooling device 4 before and after the rolling mill, in order to reduce the rolling load and achieve high rolling and high gloss. It is cooled and cold rolled in an internally softened state.

The steel strip that has been annealed and recrystallized in the continuous annealing furnace 21 and the cooling device 22 passes through the pickling section 23 and the rinsing and drying device 24, where the oxidized scale on the surface is removed, and the steel strip is sent to the exit looper 14.
After that, in order to ensure the surface gloss of the final product and remove the elongation at the yield point, it is rolled with a temper rolling 6127, adjusted to shape with a tension reformer 28, cut with an exit shear 17, and rolled into a coil 20 with a tension reel 18. It is wound up.

The manufacturing apparatus according to the present invention is equipped with a combination of rolling mills at each stage shown in FIGS. 1 to 3, and their functions will be further explained below.

In the hot pickling line, the first stage cold rolling mill located after the continuous annealing and pickling section uses low speed, small diameter rolls,
Low viscosity rolling oil can be used, and conventional measures to thin the oil film can be taken. Honto pickling is usually carried out at a line speed of 30 to 40 wp-, and in the first stage cold rolling mill, the rolling reduction is 50 wp.
%, the cold rolling exit speed is suppressed to 80 mp- or less,
Low speed rolling is possible, and troubles caused by small diameter rolls and heat scratches caused by low viscosity rolling oil do not occur.

Furthermore, by placing a heating device just before the rolling mill and a cooling device before and after the rolling mill, the entire surface is heated and then the surface is cooled to harden the surface and soften the inside, thereby preventing the formation of oil pits. Further, by controlling heating and cooling, it is possible to control the temperature to an area where no oxide film (temper color) is generated.

The cold rolling rate in the first stage cold rolling mill is preferably 30
% or more is the lower limit value for obtaining a surface work-hardened structure to suppress the occurrence of oil pins during tandem rolling in the next second stage rolling mill. However, if it exceeds 50%, the rolling speed in the first stage becomes too high,
Oil pints may occur in the first stage, in which case the speed of the entire hot pickling line must be reduced.

The reason why the work roll diameter for the first stage cold rolling is limited to 250 mm or less is that the diameter is preferably as small as possible from the viewpoint of preventing oil bit generation and reducing rolling load, but if the diameter is too small, the convex part of the pickling bit will cover up. There is a risk and to some extent,
This is because a medium diameter of 2501 or less is effective in ensuring the roughness of the matrix band.

A heating device placed in front of the common steel tandem mill, which is the cold rolling mill required for the second stage, and a cooling device placed on the inlet and outlet sides of the mill are used to prevent oil pits and temper. Color can be prevented.

In addition, in the first stage cold rolling on the hot pickling line, rolling is carried out with a reduction ratio of 30% or more, and the surface hardening of the copper strip has progressed, so from this point of view, the second stage cold rolling is required. It is highly effective in preventing oil pints in inter-rolling mills.

Furthermore, cooling after the middle pass of the second-stage cold rolling mill is strengthened to prevent heat scratches. The temperature of the copper strip increases due to the heating at the entrance of the tandem mill and the processing heat of rolling, and the rolling load is 20 to 3 at 5US304.
0% and 5US430, the reduction is about 5 to 10%, but it is easy to cause heat scratches due to lack of oil film, and to prevent this, in addition to the conventional lubrication and cooling from the entrance side of the rolling mill stand, cooling between stands and rolling mill. We will strengthen the cooling on the exit side, lower the roll surface temperature and copper strip surface temperature, and achieve internal softening of the copper strip. Examples of enhanced cooling include cooling of the copper strip with a roll having a cold temperature, inter-stand cooling with low-temperature high-pressure water or low-temperature lubricating oil, and the like.

In the third-stage cold rolling mill located in front of the continuous annealing furnace seen in the finishing pickling line, the heating device located in front of the mill and the cooling device located on the exit side of the mill are connected to the hot pickling line. , and as in the case of tandem mill lines, this is to prevent oil pits, temper color, and heat scratches.

In this third stage of cold rolling, the surface hardening of the steel strip is progressing, and the line speed for finishing pickling is up to 10
0m/min, for example, at a low speed of about 50+w/min,
Since it is equipped with the above-mentioned heating and cooling device, it is possible to almost completely prevent the occurrence of oil pits and heat scratches, and it is possible to roll at a high reduction ratio of, for example, 30%, and the immlml surface surface is kept clean. The effect is also greater and the gloss level is improved.

In the present invention, if the oil pit generation area ratio (described later) of the first and second stage cold rolling mills is 10% or more, the number of stands for the third stage cold rolling is required to be three or more. ,
If the generation area ratio is less than 10%, one or two stands are sufficient. If the strip rolled in the first and second stage cold rolling mills is used, the area ratio of oil pits can be reduced by approximately 4 to 7%.
It can be suppressed to no more than 10%.

Furthermore, if a small diameter roll of 150 mm or less in diameter is used in the third stage cold rolling mill, heating and cooling devices are installed, and rolling is performed at a high reduction of 25% or more, the correction effect is stronger than the normal Sendzimir correction effect. As shown in FIG. 3, even one stand is sufficient and the oil pit generation area ratio can be suppressed to approximately 3% or less.

In addition, the maximum oil pit occurrence area rate in a normal tandem mill is around 40%, and the maximum oil pit occurrence area rate after the first pass at normal operating speed in a Sendzimir mill is 10 to 15%, and after the final pass. It is about 2-3%.

As mentioned above, tandem rolling is divided into three parts, and the first and third stage cold rolling mills are incorporated into the conventional hot pickling and finishing pickling lines, so there is no need to add any new processes. Furthermore, in the case of ordinary steel tandem mills, when rolling stainless steel, 5 to 6 stands or more are required, but in the present invention, 2 to 4 stands are sufficient. Furthermore, it is possible to use relatively high viscosity rolling oil to prevent heat flanch, and to perform rolling at high speeds exceeding 100100O.

Although the present invention has been explained above with a focus on stainless steel strips, mainly chromium-based stainless steel strips, it is also applicable to nickel-based stainless steel strips and Ti thin plates. Using the device according to the present invention,
Cold-rolled steel sheets with good surface gloss can be obtained while ensuring high productivity.

It is also conceivable that the second stage rolling be performed at high speed with a single reversible rolling mill instead of a tandem mill.

Next, the effects of the present invention will be specifically explained using examples.

(Example) In this example, using each of the cold rolling mills shown in FIGS. 1 to 3, a 5US430 stainless steel plate was hot-rolled into a 3.2 m-thick copper strip. Thickness 0.8
It was cold rolled to am'.

The cold rolling conditions at this time were as summarized below.

Heating temperature: 180°C Hot pickling: Sulfuric acid tenfluoro-nitric acid finishing Pickling: Salt bath + sodium sulfate electrolytic pickling #Ait rolling ratio: 1.1% Table 1 shows other manufacturing conditions and the results obtained in this example. The results of evaluation tests on the surface properties of cold-rolled stainless steel strips are summarized below.

The procedures and evaluation criteria for each characteristic evaluation test were as follows.

<Area ratio of oil pints> The surface of the copper strip after cold rolling was examined at a certain microscope magnification (in this example, 4
When magnified at 00x), the concave bone appears black and the other parts appear white. The area of this black part was determined, and the average value of the 10 visual fields divided by the area of the entire visual field was defined as the oil pit occurrence area ratio (p), and the following 5-level evaluation was performed.

In order to eliminate the influence of pickling pits, a copper strip whose pickling bit roughness was regulated to Ra≦1.0μ was used as a test copper strip.

ar p<3 (%) b: 3≦p<6 (%) c: 6≦p<10 (%) d: 10≦p<30 (%) e: 30≦p (%) <Glossiness GS 20 '> JIS Z 8741 Glossiness measurement method 5 (GS20°
)by.

<Visual Glossiness> The surface of the copper strip after temper rolling was visually inspected under a fluorescent lamp, and was conveniently divided into the following four grades for evaluation.

A: The background is black and shiny, or there is slight clouding, and the outline is clear under fluorescent lighting.

B: The background is black and shiny, or there is slight clouding, and the outline of the fluorescent light is slightly blurred.

C: The background is slightly cloudy and the outline of the fluorescent light is slightly blurred.

D= The white cloudiness of the ground is noticeable (fail).

However, D) is a failing level, and A) is the best.

The following points can be found from the results shown in Table 1.

Comparative product A was rolled in 7 baths in a Sendzimir mill. The oil pit generation area ratio is 3% or less, and the visual gloss is also good. However, the rolling speed is 250s+p
Q is quite low.

Comparative product B was rolled in 5 baths using a tandem mill.

The area ratio of oil pits is more than 30%, and G52
Both the 0" gloss and visual gloss are poor.

Comparative product C was reduced by 15% in a non-lubricated skin bath as a preliminary treatment, but the area where oil pits were generated was slightly larger.
The visual gloss level is also low, and the product requirements cannot be met.

The product of the present invention, E, is a case without preheating, the product E of the present invention is a case in which the first stage cold rolling is performed without lubrication, and the product F is a case in which the first stage cold rolling is performed without lubrication.

Inventions F and G are cases where preheating and cooling are used.
uses a mineral oil emulsion. When beef tallow-based emulsion rolling oil is used, the incidence of oil pits is somewhat high.

It is also shown that when preheating and cooling are performed, a high rolling reduction can be achieved, and one pass is sufficient for the third stage rolling in particular.

Inventive product H shows the case where the second stage was omitted because a sufficient rolling rate could be ensured in the first and third stages.

Although only the example of 5US430 steel strip was shown this time, the same can be said of other stainless steel strips, low chromium steel strips, and Ti thin plates.

(Effects of the Invention) As described above, according to the present invention, while maintaining the high productivity of the tandem rolling mill, it is possible to produce high-quality cold-rolled stainless steel strip that suppresses the occurrence of oil pits and heat exchange as much as possible. As a result, it is possible to obtain a cold-rolled steel strip whose surface gloss is comparable to that cold-rolled by a full-pass Sendzimir mill, which improves productivity and quality when manufacturing stainless steel cold-rolled steel sheets. This has great practical significance as it also provides improved properties that have not been compatible in the past.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a hot pickling line including a first-stage cold rolling mill according to the present invention; Fig. 2 is a schematic illustration of a tandem rolling line having a second-stage cold rolling mill according to the present invention. Explanatory drawings; and FIG. 3 are schematic explanatory drawings of a finishing pickling line having a third-stage cold rolling mill in the present invention. 1; Hot pickling device 2: Rolling mill 3: 5 Near: 9: 11: 12: 14: 17: 19: 2I: 23: 27: 29: 52: Heating device 4 Payoff reel 6 Welding machine 8 Continuous annealing furnace 10 Mechanical descaling pickling tank 13 Output side looper 16 Shear 18 Steel strip 2° annealing furnace 22 Pickling section 24 Supplementary rolling Ill 28 Dryer tandem mill 62 : Cooling device: Shear two-person side looper: Cooling band ring part: Dryer :Drying device: Tension reel: Coil: Cooling device: Drying device: Tennoyon roller: Rolling machine

Claims (4)

[Claims] (1) A first-stage cold rolling mill that performs surface-hardening rolling to prevent oil pits following the pickling process, and heat scratches on the surface-hardening strip rolled by the first-stage cold rolling mill. A second-stage cold rolling mill performs high-reduction rolling to finish the strip to the target dimensions while preventing the rolling process, and the strip rolled to the target dimensions by the second-stage cold rolling mill is subjected to finish rolling to improve surface smoothness. , a stainless steel cold rolled steel strip production equipment equipped with a combination of a third stage cold rolling mill connected to the pre-process of finish annealing and pickling process. (2) The work roll diameter of the second stage cold rolling mill is made larger than the work roll diameter of the first stage cold rolling mill, and the work roll diameter of the first stage cold rolling mill is set to be larger than the work roll diameter of the first stage cold rolling mill. 2. The apparatus for producing cold rolled stainless steel strip according to claim 1, wherein the roll size is equal to or smaller than that of a work roll of a staged cold rolling mill. (3) The work roll diameter of the first stage cold rolling mill is 2
50 mm or less, the work roll diameter of the second stage cold rolling mill is more than 150 mm, and the work roll diameter of the third stage cold rolling mill is 150 mm or less. Obi manufacturing equipment. (4) Using the apparatus according to any one of claims 1 to 3, the cold rolling rate by the first stage cold rolling mill is 30% or more, and the rolling speed by the third stage cold rolling mill is 100 m/min or less. A method for producing cold-rolled stainless steel strip.