JPH01317604A - Work roll for cold rolling - Google Patents

Abstract

PURPOSE:To increase the rolling reduction per set of upper and lower work rolls and to prevent the generation of the traces on a steel strip by forming a rough surface of the specified center line height and max. height on the work roll surface by using a high-density energy source. CONSTITUTION:While the rolls are rotated or moved axially, the rolls are irradiated regularly with laser pulses, by which craters 3 are regularly formed and the molten metal blown off sticks again to the circumference of the craters 3, thus forming build-up parts 4. The rough surface having the center line average height Ra in a 0.5<=Ra<=3.0 range and the max. height Rmax in a 1.0<=Rmax<=50.0 range is formed on the roll surfaces in this case. The rolling reduction pert set of the upper and lower work rolls is increased in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a work roll for a cold rolling mill, and particularly to a work roll suitable for use in a front stage stand other than the final stand of a tandem cold rolling mill. .

<Conventional technology> Since blind rolls are used in the front stands of tandem cold rolling mills, except for the final stand, the copper strip does not enter the roll bite area well, resulting in rapid tracking of the strip called sagging. This phenomenon caused plate breakage and roll damage. One possible reason for this is that the frictional resistance between the strip and the work roll decreases, causing the steel strip to slip.

As a countermeasure to this problem, there is a method of increasing the frictional resistance by changing the material and roughness of the work roll.

Among these methods, the method of changing the roughness has conventionally been achieved by increasing the grindstone count of the grindstone used to polish the roll surface and making the grain size finer.

<Problems to be Solved by the Invention> However, the above-mentioned method of using a fine-grained grindstone only creates minute irregularities on the entire surface of the roll corresponding to the grinding wheel count, and is easily affected by roll abrasion. 1. Processing amount per set is 170 in rolling length
~180 hours (when using grindstone 46), and increasing the throughput was an issue.

Means for Solving the Problems> The present invention provides a work roll for cold rolling that uses a high-density energy source to create a centerline average roughness Ra on the roll surface.
is in the range of 0.5≦Ra≦3.0, and the maximum height R
A rough surface with wax in the range of 1.0≦RIIIax≦50.0 is formed.

Effect> As mentioned above, the conventional method of using a fine-grained grindstone has a strong influence of roll wear and cannot be expected to extend the life of the roll surface.

Therefore, the present invention uses a high-density energy source to sparsely form irregularities on the polished roll surface, so that even if the roll wear progresses, the centerline average roughness Ra will not be affected so much ( The purpose is to extend the life of the roll surface by processing the surface of the roll so that the frictional resistance does not undergo such a large change.

Here, the center line average roughness Ra and the maximum height Rwax are:
Defined in JIS BO601.

The center line average roughness Ra is calculated by extracting a portion of measurement length l from the roughness curve in the direction of its center line, setting the center line of this sampled portion as the y=r
When expressed as (x), it refers to the value determined by the following formula expressed in micrometers (p-) (see Figure 3).

The maximum height Rmax is defined as the distance between the two straight lines parallel to the average line of a section (hereinafter referred to as the "sampled section") that is extracted from the cross-sectional curve by the standard length, and the distance between these two straight lines that is the length of the section curve. This value is measured in the direction of magnification and expressed in micrometers (μ,) (see Figure 4).
.

From this, consider roughness by dividing it into three parts: mountains, valleys, and flat surfaces.
By forming irregularities with peaks and valleys on a plane as necessary and controlling the hole shape (crest height, valley depth, large area), the required center line average roughness Ra and maximum height Rmax can be obtained. You can see what you can get.

In addition to using a high-density energy source, methods for creating unevenness on the surface of a polished roll include: ■ Sit-plast processing (a process that creates fine uneven impressions by projecting hard particles such as iron powder); ■ Electrical discharge machining ( One possibility is to create spark discharge between a roll and an electrode facing the roll circumferential surface, thereby creating fine irregularities on the roll circumferential surface, but in either case, the above hole shape (crest height, Valley depth.

Therefore, even if the center line average roughness Ra satisfies the requirements, the peak height may be locally high and Rsax may be excessive, leaving marks on the plate surface.

On the other hand, when a high-density energy source is used, ■ the hole shape can be controlled by changing the output and irradiation time of the high-density energy source, ■ the roll can be irradiated with high-density energy intermittently, and By making the high-density energy source or the roll freely movable, it is possible to form holes one by one, and the hole pitch can be varied (the roughness can be controlled), so the centerline average roughness R
It is possible to control both a and the maximum height Rmax.

Therefore, using a high-density energy source, we investigated the relationship between the life of the roll surface and the occurrence of marks by changing the centerline average roughness Ra and maximum height Rwax.
We obtained the results shown in the figure.

Figure 5 shows the relationship between the center line average roughness Ra (horizontal axis) and rolling 1h per set of upper and lower work rolls (I axis). The present invention shows better effects than the conventional technology.

In addition, Figure 6 shows the relationship between the maximum height Rmax (horizontal axis) and the number of mark generating coils (vertical axis).
．． In the range of 0≦Rtaax≦50, it shows superior effects than the conventional technology.

<Example> Roughness is formed using, for example, a laser as a high-density energy source.

That is, while rotating the roll l shown in FIG.
Laser pulses are successively projected onto the surface of the roll 2, and the laser energy regularly melts the roll surface 2 to form regular lattice-shaped recesses.

FIG. 2 is an enlarged sectional view of the roll surface portion A in FIG.
In Fig. 2, 3 is a crater-shaped recess (hereinafter simply referred to as a crater) formed on the roll surface, and around the crater 3, the molten roll base metal rises in a ring shape from the roll surface and forms a flange. A shaped raised portion 4 is formed.

To explain this process in detail, the metal forming the roll heated by the laser instantly turns into metal vapor due to the high irradiation energy density, and the vapor pressure generated at this time blows away the molten metal on the roll surface 2, creating a crater 3. , and the blown molten metal re-fixes around the crater 3 to form a raised portion 4 surrounding the crater 3. These series of reactions can be carried out more efficiently by spraying an auxiliary gas such as oxygen gas toward the reaction point.

The depth, elevation and diameter of the crater 3 on the roll surface 2 formed by the laser pulse are determined by the magnitude of the incident laser energy and the projection time.

By regularly irradiating the roll 1 with laser pulses while rotating or moving it in the axial direction, the craters 3 described above are formed regularly, and the roll surface is formed by a collection of these craters 3 formed one after another. 2, a substantially regular rough surface can be formed.

Here, the distance between adjacent craters 3 is the roll l
For the rotational direction of roll 1, by changing the frequency of the laser pulse in relation to the rotational speed of roll 1, and for the axial direction of roll l, the laser pulse is moved in the roll axial direction every time roll l rotates once. Eleven sections are possible by changing the moving pitch of the laser irradiation position.

As described above, the center line average roughness Ra and the maximum height R
max can be controlled and the 0-rule of the present invention can be obtained.

If the rough surface has the shape shown in Figure 2, the crater portion 3 will not come into contact with the steel strip, so the crater portion 3 will have less influence on the flange portion 4 and the polished surface 5 during roll wear, and will last for quite a long time. Roughness can be maintained. As a result, the life of the roll can be extended compared to a conventional roll having only the polished surface 5.

Furthermore, although the above description is based on the case where a laser is used as the high-density energy source, the same applies to the case where a high-density energy source such as plasma or an electron beam is used.

Next, specific examples will be described.

Craters were regularly formed on the work roll of the first stand of a four-high rolling mill by the method of the example, and Ra =
When rolled to a roughness of 1.54g, RIlax -25.8n, the throughput per set of upper and lower work rolls was previously about 170-180kl, but increased to about 200-220kl. The life of the roll surface was extended by 10-30%.

Further, no marks were generated at this time.

<Effects of the Invention> As described above, the present invention has the excellent effect of being able to significantly increase the amount of rolling per set of upper and lower work rolls, and eliminating the occurrence of steel strip marks.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing the work roll of the present invention, FIG. 2 is an enlarged sectional view of section A in FIG. 1, FIG. 3 is a diagram showing the definition of center line average roughness Ra, and FIG. The figure shows the maximum height Rma
A diagram showing the definition of x, Figure 5 is a graph showing the relationship between the center line average roughness Ra of work rolls and the rolling amount per set of work rolls, and Figure 6 is a graph showing the maximum height Rwa of work rolls.
It is a graph showing the relationship between x and the number of trace generating coils. 1... Work roll, 2... Roll surface, 3
... Crater, 4... Swelling part, 5
...Polished surface. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] Using a high-density energy source, the center line average roughness Ra of the roll surface is in the range of 0.5≦Ra≦3.0, and the maximum height Rmax is in the range of 1.0≦Rmax≦50.0. A work roll for cold rolling characterized by forming a certain rough surface.