JPH0691306A - Manufacture of cold rolled stainless steel strip - Google Patents

Abstract

PURPOSE:To improve the surface gloss of a cold rolled stainless steel strip. CONSTITUTION:Preliminary cold rolling by cross roll rolling of which the draft is 5% is executed to a hot rolled stainless steel strip which is annealed and pickled and, after that, cold rolling by parallel roll rolling or the combination of cross roll rolling and parallel roll rolling is executed. The preliminary cold rolling may be executed with a specialized preliminary rolling mill, by the initial pass of usual reverse rolling or cross roll rolling at a stand on the inlet side of tandem rolling. In this way, the cold rolled stainless steel strip excellent in gloss on the surface is manufactured by proper combination of cross roll rolling and parallel roll rolling. Even by tandem rolling of high production efficiency, glossiness that is equal to that by rolling with a conventional Senzimir mill is attained.

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 cold rolled stainless steel strip, and more particularly to a rolling method for producing a cold rolled stainless steel strip having excellent surface gloss.

[0002]

2. Description of the Related Art Usually, in order to produce a cold rolled stainless steel strip, annealed and pickled stainless hot rolled steel strip is cold rolled while supplying a lubricating oil, and then further annealed and pickled or brightened. It is annealed and then temper-rolled to finish.

[0003] Stainless cold-rolled steel strip is often used as a product as it is in finish temper rolling, so that it is required to have particularly excellent surface gloss. As a method for improving the gloss of the surface of a cold rolled stainless steel strip, for example, JP-A-2
JP-A-169108 discloses a method in which a hot rolled stainless steel strip is annealed and pickled, and then cold rolled with a rolling reduction of 5% or more using a work roll provided with grooves intersecting the outer surface. It is disclosed. This method is intended to discharge the lubricating oil existing between the work roll and the steel strip to the outside of the roll bite by cold rolling with a work roll provided with a groove intersecting the outer surface. When a large amount of lubricating oil is present in the recess of the surface of the steel strip between the work roll and the steel strip, there is no escape of the lubricating oil while the work roll and the steel strip are in contact with each other in the roll bite. With the lubricating oil contained in this way, the dents on the surface of the steel strip after rolling are slightly smaller than those before cold rolling, but as a result, the surface roughness of the steel strip before cold rolling is cold. This is because it remains as it is even after hot rolling. However, JP-A-2-1691
In the method disclosed in the publication No. 08, (a) the step of performing groove processing intersecting the roll is complicated, (b) when the groove depth is deep and the number of grooves is small, the surface of the rolled material is Concavities are formed on the surface, and that part becomes a high surface pressure during the next cold rolling, causing seizure due to insufficient lubrication. (C) Crossed grooves cause clogging and wear as the rolling progresses, and the lubricating oil is discharged. There is a problem that the effect of doing is reduced.

[0004]

The number of stainless cold-rolled steel strips used as finished temper-rolled products is increasing, and the stainless cold-rolled steel strips are required to have particularly excellent surface gloss. ing. In order to improve the surface gloss of the stainless cold-rolled steel strip, it suffices to reduce the surface roughness of the stainless cold-rolled steel strip. For that purpose, should the surface roughness of the hot-rolled steel strip before cold rolling be reduced? It is known that the surface roughness of the steel strip may be reduced at the initial stage of cold rolling. However, the method described in the above-mentioned Japanese Patent Laid-Open No. 2-169108 is difficult to put into practical use, and it is difficult to meet the recent severe demands of customers for the surface gloss of stainless cold-rolled steel strip.

An object of the present invention is to provide a method for producing a stainless cold-rolled steel strip having an excellent surface gloss that can meet the recent severe demands.

[0006]

As will be described later in detail, the present invention provides a cold rolling of stainless steel which has an extremely excellent surface gloss if it is appropriately combined with cross roll rolling and parallel roll rolling. It was made based on the knowledge that a rolled steel strip can be obtained. "The annealed and pickled stainless hot rolled steel strip is subjected to preliminary cold rolling by cross roll rolling with a rolling reduction of 5% or more, and then parallel. A method for manufacturing a stainless cold-rolled steel strip, which comprises performing cold rolling by roll rolling or a combination of cross roll rolling and parallel roll rolling ”.

In the present invention, the term "cross roll rolling" refers to the material to be rolled (hot rolled steel strip 3) as shown in FIG.
Means that the upper and lower roll axes have angles (α) in opposite directions with respect to the direction perpendicular to the rolling direction (longitudinal direction), and are rolled in a plane parallel to the rolling surface. To do. In a multi-high rolling mill (4Hi mill, 6Hi mill, etc.), this inclination may be provided only on the work rolls, or the back up roll may be inclined together. "Parallel roll rolling"
The term "normal rolling" means rolling in which both the upper and lower roll axes are perpendicular to the rolling direction (longitudinal direction).

1 and 2 are schematic views showing a typical embodiment of the method of the present invention. The method of the present invention can be roughly divided into a case where it is carried out using a dedicated preliminary rolling mill and a case where it is carried out using a normal (existing) rolling mill without using it. In either case, the material is a steel strip that has been annealed and pickled after hot rolling (hereinafter simply referred to as "hot rolled steel strip").

When using a pre-rolling machine exclusively for I (FIG. 1) The rolling machine for pre-cold rolling may be of any type as long as it can carry out roll cross rolling. For example, 1-stand 2Hi mill, 4Hi mill, 6Hi mill, etc. can be used.

After performing a cross roll rolling with a reduction ratio of 5% or more with a preliminary rolling mill, or a reverse rolling with a one-stand rolling mill (a rolling mill with a small diameter work roll such as a Sendzimir mill may be used), or Tandem rolling is performed by a multi-stage rolling mill (multi-stand rolling mill). In the case where all the reverse rolling is performed by the parallel rolling method, is the case where at least one initial pass (the first pass is preferable but not limited to this) is rolled by the roll cross rolling method, and then the parallel rolling is performed.

And are continuous rolling methods using a tandem rolling mill having a plurality of roll stands. If all of this tandem rolling (rolling with all stands) is performed by the parallel roll rolling method, at least one stand on the entry side (the first stand is preferable but not limited to this)
This is a case where the rolling is performed by the cross roll method and then by the parallel roll method.

As described above, when the cross roll rolling is first performed not only in the preliminary rolling but also in the subsequent rolling (main rolling), the surface gloss of the product steel strip becomes more excellent as described later.

After tandem rolling, parallel rolling is performed once or more by, for example, a Sendzimir mill. Regarding the tandem rolling at this time, there are a case where parallel rolling is performed on all stands and a case where rolling is performed on at least one stand on the entrance side by a cross roll method, and the latter is preferable.

II When a dedicated pre-rolling mill is not used (FIG. 2 ) This is a method in which initial rolling by a normal rolling mill is pre-rolling. This can also be carried out by either reverse rolling with a one-stand rolling mill or continuous rolling with a tandem rolling mill.

Is the case of reverse rolling. At this time, the cross-roll type rolling must be performed in the initial one to several passes. If this cross roll rolling is performed at a rolling reduction of 5% or more, this corresponds to the above-described preliminary rolling. After that, it is finished by parallel roll rolling.

In the case of tandem rolling, in this case, cross-roll type preliminary rolling is performed at one to several stands near the entrance side. Of course, the rolling reduction of cross roll rolling must be 5% or more. After that, parallel rolling is performed on the subsequent stand to finish. Although not shown in FIG.
It goes without saying that the rolling with the Sendzimir mill may be performed after the rolling with or.

[0017]

The method of the present invention is characterized in that the annealed and pickled stainless hot-rolled steel strip is subjected to pre-cold rolling by a cross roll rolling method with a rolling reduction of 5% or more, and then by a normal parallel rolling method. It is in the place of cold rolling.

FIG. 3 is a diagram showing cross roll rolling in preliminary rolling, that is, a state in which upper and lower work rolls are rolled at a crossing angle α in a plane parallel to the rolling plane.
(a) is a plan view and (b) is a side view. The material to be rolled before rolling is the hot rolled steel strip 3 and the steel strip after rolling is the cold rolled steel strip 4.

On the upper surface of the hot-rolled steel strip 3, the direction of travel of the hot-rolled steel strip 3 (X direction) and the direction of rotational peripheral speed of the side of the upper work roll 1 in contact with the hot-rolled steel strip 3 (Y direction). ) Is the same as the intersection angle α. Therefore, a slip component force in the plate width direction (Z direction) is generated on the upper surface of the hot rolled steel strip 3 by the upper work roll 1, and the surface layer portion of the upper surface of the hot rolled steel strip 3 undergoes shear deformation in the plate width direction. receive. Further, the convex portion of the ground surface of the roll moves in the plate width direction, and the metal contact between the roll and the hot rolled steel strip increases. By these actions, the surface of the steel strip is evened out, the surface roughness of the material to be rolled is reduced, and the cold-rolled steel sheet 4 having a smooth and excellent gloss is obtained. This phenomenon similarly occurs between the lower surface of the hot rolled steel strip 3 and the lower work roll 2. In order to obtain a cold-rolled steel strip having excellent gloss, it is preferable that the crossing angle α of the work rolls is 0.2 ° or more. The larger the crossing angle α, the better the gloss,
On the other hand, since a mechanical crown is generated on the surface of the cold rolled steel sheet, when increasing the crossing angle α, use a work roll having a concave crown shape (the diameter of the roll end is larger than the diameter of the central part). Good.

The reason for reducing the rolling reduction by the cross roll method of the preliminary cold rolling to 5% or more is as follows.

When the rolling reduction is less than 5%, the work roll reduces the sliding component force in the strip width direction acting on the surface layer portion of the hot rolled steel strip, and the strip width received by the surface layer portion of the hot rolled steel strip. Directional shear deformation is reduced. When the rolling reduction is less than 5%, the lubricating oil introduced into the roll bite increases, and the ratio of metal contact between the hot rolled steel strip and the work roll decreases. As a result, the surface roughness of the cold rolled steel sheet does not become small, and the luster of the cold rolled steel sheet is not improved. The higher the rolling reduction, the better the surface gloss of the cold-rolled steel sheet, but the rolling reduction is about 25
%, The improvement effect is almost saturated.

The above-mentioned preliminary rolling may be carried out in one pass or in a plurality of passes so that the total reduction ratio becomes 5% or more. Under normal rolling conditions, a reduction of about 25% is possible with one pass.

As described above, there are various methods for subjecting the hot rolled stainless steel sheet to the pre-cold rolling by the cross roll method with the rolling reduction of 5% or more. One of them is a method of using a dedicated rolling mill as shown in FIG. That is, a hot rolled stainless steel strip is annealed, pickled, and then cold-rolled by a roll mill with a rolling mill having a rolling reduction of 5% or more by a dedicated rolling mill, and then an ordinary cold rolling mill (tandem rolling mill). Alternatively, finish cold rolling is performed by a reverse rolling machine, or a combination thereof. When this dedicated rolling mill is provided on the outlet side of the pickling line, pre-cold rolling is performed immediately after pickling. If this dedicated rolling mill is installed offline, independently, the hot-rolled steel strip after pickling should be wound around a coil and then pre-cold rolled before the finish cold rolling. become. When a dedicated rolling mill is used, the cost of new equipment is added, but the rolling schedule of the original cold rolling mill is not affected at all.

Another method of pre-rolling is, as shown in FIG. 2, at least the first pass (in the case of a reverse rolling mill) of an ordinary cold rolling mill (reverse rolling mill or tandem rolling mill) in the initial stage. The use of at least one stand on the entry side (in the case of a tandem rolling mill). In this case, since there is no need for a dedicated rolling mill, there is no problem in installing new equipment, but it may be necessary to change the rolling schedule of the original cold rolling mill.

After the preliminary rolling, normal cold rolling (main rolling) is performed. Here, as shown in and of FIG. 1, all may be rolled by a parallel roll system,
Further, as shown in and, cross roll rolling and parallel roll rolling can be used together. Further, as described above, a tandem rolling mill and a reverse rolling mill such as a Zanzimir mill may be used together, as described above.

When the cold rolling mill is a reverse rolling mill,
At least one initial pass (preferably the first pass) is cold rolling by the cross roll rolling method, and then cold rolling by the normal parallel rolling method is performed. When the cold rolling mill is a tandem rolling mill, cold rolling is performed by at least one stand on the entry side (preferably the first stand on the entry side) by a cross roll method, and then by a normal parallel roll method. Is applied. There is no particular restriction on the reduction ratio of the cross roll rolling at this time. As described above, after performing the preliminary cold rolling by the cross roll rolling method with the rolling reduction of 5% or more, and further performing the cold rolling together with the cold rolling by the cross roll rolling method in the main rolling, the cold rolled steel sheet can be obtained. The luster is dramatically improved.

The cold rolling by the cross-roll method in the main rolling after the preliminary cold rolling is performed as early as possible (in the case of a reverse rolling mill) or in the initial stand (in the case of a tandem rolling mill). Good. Desirably, it is carried out within 3 passes (for a reverse rolling mill) or within 3 stands (for a tandem rolling mill). Then, the rolling on the remaining remaining passes or the remaining stands is a parallel rolling cold rolling. That is, the finish of cold rolling must be performed by the parallel roll method. When the cross roll rolling is performed, the steel sheet is twisted due to the shearing force in the width direction, so that the rolling is performed by the parallel roll method to correct the twist.

Pre-rolling (or at the beginning of main rolling)
Even if cross roll rolling is performed to improve the surface gloss, if the number of parallel roll rollings thereafter increases, the oil pit flaws due to the pushing of rolling oil and the occurrence of minute cracks may reduce the gloss. In such a case, it is desirable to interpose the cross roll rolling between the parallel roll rolling during the main rolling process.

The surface roughness of the work roll of the cold rolling mill used for the cross roll rolling in the method of the present invention is Ra.
The effect is great when it is in the range of 0.1 to 2.0 μm. Further, the outer diameter of the work roll need not be particularly limited,
There is no problem at all even if the outer diameter is as small as 150 mm or less, or as large as 450 mm. The lubricating oil used may be the one normally used for cold rolling of stainless steel and low carbon steel.

[0030]

[Example 1] Using annealed and pickled ferritic stainless steel (JIS SUS 430) hot-rolled steel strip (thickness: 4.5 mm) as a raw material, the following cold rolling was carried out using equipment with a line configuration shown in FIG. I went.

The pre-rolling mill used had a work roll diameter of
There are 450 mm, 350 mm, and 250 mm 4Hi mills, and work roll diameters of 120 mm and 80 mm, 6Hi mills (1 stand each). First, in these preliminary rolling mills,
Pre-cold rolling with cross-roll method under various conditions shown in Table 3, then work roll with diameter 450mm and diameter 1420
Cold rolling (main rolling) by a normal parallel rolling method was performed using a 5-stand tandem rolling mill equipped with a back roll of mm, a Sendzimir mill having a work roll of 70 mm in diameter, and a combination thereof.

Tables 1 to 3 show the roll diameter, roll crossing angle (α), roll surface roughness Ra and rolling reduction of the rolling mill used in the preliminary rolling.

All the cold rolling in the main rolling is performed by a parallel roll system, and the rolling reduction is 82% in total with the rolling reduction of the preliminary rolling.
(That is, the thickness of the final cold-rolled steel strip is 0.8 mm
Was done). Rolling with the Sendzimir mill was carried out in 8 passes, and in the case of a combination of tandem rolling and Sendzimir mill rolling, it was rolled down to 1.0 mm by tandem rolling and rolled by 1 pass with the Sendzimir mill to finish to 0.8 mm.

The lubricating oil used in the preliminary rolling and finish rolling is a synthetic ester emulsion rolling oil.

Tables 1 to 3 also show the surface glossiness of the obtained cold rolled steel strips. The glossiness was visually determined and evaluated in five grades A to E in order of good glossiness.

In order to demonstrate the effect of the method of the present invention, the pickled hot-rolled steel strip is subjected to the first cold rolling by the parallel roll system with a rolling reduction of 5%, that is, the preliminary cold rolling. A comparative example in which cold rolling with a rolling reduction of 5% was performed without using the cross roll method, and then cold rolling was performed using the normal parallel roll method, and normal parallel rolling was performed without further preliminary rolling. The results of the comparative example in which cold rolling is performed by the roll method are also shown in Tables 1 to 3.

Table 1 shows the case where the main rolling after the preliminary cold rolling was carried out by the normal parallel roll rolling by the tandem rolling mill, and Table 2 shows the case where it was carried out by the reverse rolling by the Sendzimir mill. Shows the case where the main rolling was first performed by a tandem rolling mill to a thickness of 10 mm and then by parallel roll rolling by a Sendzimir mill to a thickness of 0.8 mm.

In Table 1, Test Nos. 1 to 8 are examples of the present invention. Since the main rolling was only parallel roll rolling with a tandem rolling mill, the surface glossiness was B rank, but there was no preliminary rolling, or a comparative example in which preliminary rolling was performed by the parallel roll system
Compared with (No. 9 and 10), the remarkable effect of the method of the present invention is clear.

In Table 2, Test Nos. 11 to 18 are examples of the present invention. Performing the main rolling with the Sendzimir mill itself has the effect of improving the surface glossiness, but the effect of the method of the present invention is also clear here in comparison with Nos. 19 and 20 of Comparative Examples.

Table 3 shows an example of a combination of tandem rolling suitable for mass production and rolling with a Sendzimir mill having an effect of improving the surface gloss. In Comparative Examples Nos. 29 and 30, the effect of tandem rolling cannot be eliminated and the surface gloss is poor, but in the present invention examples (Nos. 21 to 28), the glossiness is A rank.

As can be seen from Tables 1 to 3, the cold rolling according to the method of the present invention makes the surface of the cold rolled steel strip extremely good. Further, it can be seen that this surface gloss is improved by about one rank in the rolling using the Sendzimir mill having the work rolls having the small diameter, as compared with the tandem rolling mill having the work rolls having the large diameter. However, even in cold rolling using only a tandem rolling mill, according to the method of the present invention, the surface gloss is greatly improved as compared with the case of using the conventional rolling method, and it was said that conventional rolling can only be achieved with a Sendzimir mill. Surface gloss is obtained. This means that a stainless cold-rolled steel strip having a good surface gloss can be efficiently produced by a tandem rolling mill.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

Example 2 This is an example of cold rolling by a combination of cross roll type and parallel roll type rolling in the main rolling after the preliminary cold rolling. The material to be rolled was annealed and pickled ferritic stainless steel (JIS SUS 430) as in Example 1.
This is a hot rolled steel strip (4.5 mm thick). Pre-rolling is Example 1
The various rolling mills used in 1. were used under the conditions (1) to (4) shown in Table 4. 10 in Table 4 is a case where preliminary rolling is not performed by these rolling mills.

For the main rolling, the same tandem rolling mill consisting of 5 stands as used in Example 1 was used.
~ Cross-roll cold rolling on at least one of the 3rd stand, then normal parallel roll cold rolling on the following stand, thickness 0.8mm
Finished. The lubricating oil used in both pre-rolling and main rolling is a synthetic ester emulsion rolling oil.

Tables 5 and 6 show the pre-rolling conditions (see Table 4).
No. ~ 10) and various conditions of cold rolling by the cross roll method of main rolling are shown. Also, after this cross roll rolling,
Tables 5 and 6 show the glossiness of the cold rolled steel sheet finished by parallel roll rolling. The evaluation criteria for glossiness is Example 1
Is the same as.

In Tables 5 and 6, test Nos. 1 to 16
Are all examples of the present invention. In test No. 13, the pre-rolling mill uses the parallel roll method, but after that, the first stand of the tandem mill is used to perform cross-rolling with a reduction rate of 25%. It has become. In addition, in Test Nos. 14 to 16, direct rolling was performed on the first stand, the first and second stands, or the first to third stands of the tandem rolling mill without rolling by the preliminary rolling mill, and the cross roll rolling method was used. This is a case where preliminary rolling is performed and then cold rolling is performed by the parallel rolling method using the same tandem rolling mill.

That is, in Test Nos. 14 to 16, the initial rolling in the tandem rolling is the preliminary rolling.

Comparing the surface glossiness of Table 1 with those of Table 5 and Table 6, preliminary cold rolling by the cross roll system was performed, and further, in the main rolling, cold rolling was first performed by the cross roll system. Then, it can be seen that the luster of the cold rolled steel sheet is dramatically improved by performing the cold rolling by the normal parallel rolling method thereafter. Tests in Table 5 and Table 6
Since Nos. 13 and 14 were subjected to the cross roll rolling only once, they were substantially the same as those in Example 1, but the preliminary rolling was not performed by the dedicated rolling mill, but the preliminary rolling was directly performed by the original rolling mill. It can be seen that the same effect can be obtained by performing cold rolling corresponding to rolling.

The examples of ferritic stainless steels have been described above. As an example of austenitic stainless steels, when the cold rolling of the present invention is performed using a hot rolled steel strip of JIS SUS 304 steel strip as a material, A cold-rolled steel strip having an excellent surface gloss could be manufactured as well.

[0052]

[Table 4]

[0053]

[Table 5]

[0054]

[Table 6]

[0055]

According to the cold rolling method of the present invention, a stainless cold-rolled steel strip having excellent surface gloss can be obtained. In particular, in the cold rolling using a large diameter work roll such as a conventional tandem rolling mill, it was completely impossible to secure the same level of gloss as the cold rolling using a small diameter work roll such as a Sendzimir mill. Even in continuous rolling using a tandem rolling mill, the cold rolling method of the present invention can dramatically improve the surface gloss of the cold rolled stainless steel strip.

[Brief description of drawings]

FIG. 1 is a schematic view of a rolling line illustrating an embodiment of the method of the present invention using a preliminary rolling mill.

FIG. 2 is a schematic view of a rolling line illustrating an embodiment of the method of the present invention that does not use a preliminary rolling mill.

FIG. 3 is a diagram illustrating the principle of cross roll rolling, (a)
Is a plan view and (b) is a side view.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Tomizawa 4-533 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1. Annealed and pickled stainless hot rolled steel strips,
Pre-cold rolling by cross roll rolling with a rolling reduction of 5% or more, and then cold rolling by parallel roll rolling or a combination of cross roll rolling and parallel roll rolling. Production method.