JPH01262006A - Manufacture of crome plated roll for rolling - Google Patents

Abstract

PURPOSE:To extend the roll life and to improve the productive efficiency of products by performing the crome plating on the surface of bright roll having a specified roughness, then, by forming a regular rugged pattern on the plated surface through the beam working with high energy density. CONSTITUTION:The bright roll surface having the roughness Rmax<7.0mum is roughened by electrolytical etching 5, and the chrome plating 6 is performed on its surface. Then, the high energy beam working such as the laser beam is performed on the chrome plated surface to form the regular recess parts 1 and projection parts 2. Because the chrome plating is performed after the etching working is performed on a roll base material 4, the adhesion of the plated layer 5 is improved. Further, at the time of the rolling, the surface pres sure loaded on the dull peak does not promote the exfoliation of the plating, the roll life is extended. The productive efficiency of the products is improved by reducing the roll cost, decreasing the number of the roll exchangings, etc.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is a rolling roll, particularly used for rolling a cold rolled steel plate, and is used to transfer a regular uneven pattern to the surface of the roll to improve the quality of the cold rolled steel plate. The present invention relates to a rolling roll that provides improved image clarity and workability, and a method for manufacturing the same.

(Prior Art) Cold-rolled steel sheets include so-called bright steel sheets with smooth surfaces and dull steel sheets whose surfaces are moderately roughened by dull finishing. Cold-rolled steel sheets, which are widely used in automobile exterior panels and home appliances, require excellent workability for forming by press working, etc., so dull steel sheets with good lubricant retention properties are usually used. Ru.

In recent years, beautiful appearance of steel sheets has been required for the above-mentioned applications. This beauty refers to the clear appearance of the finished product after it has been painted, and is commonly referred to as image clarity. It is also known that the image clarity after painting is greatly influenced by the surface condition of the underlying AI board.

In order to improve image clarity, it is desirable to make the surface of the steel plate as smooth as possible, a so-called bright surface.

However, as mentioned above, for applications that require press molding, a dull finish is essential to ensure workability.

That is, it is generally extremely difficult to satisfy both image clarity and processability with a single surface condition.

The present inventors have previously developed a cold-rolled steel sheet that has both excellent image clarity and workability.
and No. 62-140533). In that invention (hereinafter referred to as the "prior invention"), a pattern of regularly arranged minute recesses was formed on the surface of a steel plate, and a new concept of flatness ratio was defined from the area of the recesses and the area of the smooth part. By keeping the ratio within a certain range, we succeeded in simultaneously providing excellent image clarity and processability.

The inventors of the present invention have continued to develop a steel plate that has both good image clarity and workability as described above, and have also worked on developing a method for manufacturing such a steel plate as efficiently and inexpensively as possible. As a result, it has been found that it is practical to apply a desired pattern to the surface of a rolling roll by transferring a pattern previously provided on the surface of the roll during the final step of rolling, for example, temper rolling. It has also been found that a processing method using a high energy density beam, such as a laser beam or an electron beam, is suitable for surface processing of the rolls used in such rolling. Such a processing method is described, for example, in Japanese Patent Publication No. 62-11922.
It is introduced in the issue.

In order to provide a steel plate with excellent workability and sharpness at the same time, the pattern (size and arrangement of recesses) on the surface of the steel plate must be appropriately controlled. It must be an accurate pattern. Further, even if the pattern on the roll surface is initially formed accurately, if the convex portions are worn out with each repeated rolling, the surface pattern of the product steel sheet will become disordered. To prevent this, it is necessary to increase the frequency of roll replacement and repair, which poses problems such as the cost of processing the rolls, the number of man-hours for replacement, and the interruption of rolling operations during replacement, which greatly affects the manufacturing cost of steel sheets.

In order to solve this problem, the present inventors developed a rolling roll characterized by having a regular uneven pattern on its surface and covered with a chrome plating film, and The manufacturing method is [the roll has a regular uneven pattern formed on its surface by high energy density beam machining, is electrolytically etched in a black-and-white caulking solution to roughen its surface, and then black-plated and plated. A method for manufacturing rolling rolls was proposed. (Tokugan Sho 6
No. 2-152529) The above chromium-plated roll has already been used in the production of high-definition steel sheets. However, in order to further reduce the cost of manufacturing steel sheets, rolls with a longer service life are required.

(Problems to be Solved by the Invention) An object of the present invention is to provide a chrome-plated dull roll for producing high-definition steel sheets, which is even more durable than the one previously proposed by the inventor. It is an object of the present invention to provide a method for manufacturing a roll that is made of aluminum.

(Means for Solving the Problems) In the process of manufacturing chrome-plated dull rolls, the present inventor has found that, in the process of manufacturing chrome-plated dull rolls, it is possible to obtain a smooth roll surface with a bright finish, rather than dulling a base material roll before plating and then applying chrome plating. After applying chrome plating to the chrome plated surface, I learned that it was possible to produce a durable roll with excellent plating adhesion by dulling the chrome plated surface to create irregularities. That is,
When a dull roll and a bright roll are chromium-plated and rolled under the same conditions, the surface pressure during rolling is applied more uniformly to the bright roll, resulting in less peeling of the plating film and ultimately extending the life of the roll.

According to one test result, the amount of steel plate that could be rolled by a bright roll and a dull roll, which were similarly chromium-plated, before the rolls were replaced was about five times that of the latter.

This is thought to be due to the fact that when the dull roll is chromium plated, the surface pressure during rolling is concentrated on the dull peak area, making it easy for the plating film to peel off at that area. Therefore, the surface of the brightly finished roll is first plated with chrome, and then the desired unevenness pattern is imparted to the chrome plated surface to form a dull roll. Thus, the gist of the present invention lies in the following (1) and (2).

■Rax less than 7.0 μm The surface of the bright roll is electrolytically etched to make it rough, then chrome plated.The chrome plated surface is then subjected to high energy density beam processing to create regular irregularities on the surface. A method for manufacturing a chrome-plated roll for rolling, characterized by forming a pattern.

■ After chrome plating, the surface is R, a, 7.0
The method for manufacturing a chromium-plated roll for rolling according to item (2) above, which comprises polishing to a roughness of less than μm, and then performing high-energy density beam processing to form a regular uneven pattern on the surface.

FIG. 1 is a partially enlarged schematic diagram of the surface of a roll manufactured by the method of the present invention, and FIG. 21 is a cross-sectional view taken along the line bb--b in FIG. In the figure, reference numeral 1.2 indicates a regular pattern of protrusions and recesses formed on the chromium plating layer 6 on the roll surface. A roll having such irregularities is manufactured as follows.

The surface of the roll base material 4 to be plated is first of R,,X
Polish to less than 7.0 μW, for example, R, 0.1 to 0.3 μm. Rather than immediately applying plating to this brightly finished surface, the adhesion of the plating film increases if the surface is roughened by electrolytic etching and then plated. The reference numeral 5 in FIG. 2 indicates the surface of the base material that has been roughened by electrolytic etching. This roughening imparts fine irregularities to the surface of the roll to which chrome plating is applied, providing an anchoring effect for the chrome plating film.

Electrolytic etching can be performed in the same bath as the next chromium plating. However, it goes without saying that the roll side is used as the anode, contrary to the case of plating. Examples of the bath composition and other conditions are as follows.

Electrolyte...Chromic acid 100-300 g/ρ sulfuric acid sulfuric acid 1-F Temperature: 20-60 °C Current density...20-60/dm2 hours...
...2 to 15 minutes It is preferable that the degree of this electrolytic etching be controlled by PPI (Peak Count per Inch) as specified in the SAE standard. This is a surface roughness evaluation method widely used in the industry. (For more information, please refer to "Surface Polishing and Finishing Technology Collection J Nikkei Technical Book θaki P.
233) In the electrolytic etching process of the present invention,
It is desirable to increase the number of peaks measured by PPI by 1.3 to 15 times compared to before etching.

The longer the electrolytic etching is carried out and the PPI is increased, the more the adhesion of the plating film is improved. However, excessive etching makes the surface of the roll too uneven, which also affects the surface of the plating film. That is, the irregularities on the surface of the base material appear as irregularities on the surface of the plating film, for example, Rff1aX
may exceed 70 μm.

The roll whose surface has been roughened (activated) by the above-mentioned electrolytic etching is plated with chromium in the same bath by reversing the polarity and using the roll side as the cathode. Of course, electrolytic etching and plating may be carried out in separate, suitably adjusted baths. The thickness of the plating is determined by taking into account the usage conditions of the roll, the required lifespan, etc., but in the method of the present invention, taking into account that regular unevenness is created on the plating surface by high energy density beam processing, Plating thickness is 15~40μ
m is appropriate. If it is thinner than 15 μm, the base material may be exposed during beam processing, while a plating film thicker than 40 μm tends to peel off easily. A practically preferable range is 15 to 20 μm.

One way to further improve the adhesion of the plating film and further extend the life of the roll is to strengthen electrolytic etching. However, as mentioned above, when etching is strengthened, the surface of the plating film is affected by the unevenness of the underlying layer. It is desirable that the surface of the plating film before beam processing be as smooth and bright as possible. Therefore, the second part of the present application
In the invention, in order to improve the adhesion of the plating film, chrome plating was performed using relatively strong electrolytic etching, and the roughness of the surface of the plating film was corrected by light finishing polishing before beam processing. The thickness should be less than .0 μm.

Light final polishing refers to removing irregularities (surface roughness) on the chrome plating surface to restore the original bright surface (R03X0, 7μm).
polishing to the extent that it is less than In practice, such polishing can be performed using a soft brush such as a brass wire brush, a nylon brush, or a fibrous abrasive material such as Ithaf.

At this time, if a powdered oil-based liquid polishing agent such as chromium hydroxide, alumina, or iron oxide is used in combination, the efficiency of the final polishing will be increased.

A regular uneven pattern is applied to the smooth bright chrome plated surface obtained as described above using a high energy density beam, such as a laser beam.

What is shown in FIGS. 1 and 2 described above is an example of a pattern processed using a laser beam. As shown in the figure, the portion of the surface of the chrome plating film that is hit by the beam is melted and pinched to form a recess 1, and around it there is a protrusion 2 in which molten metal bulges and solidifies. Although FIG. 1 illustrates that the convex portion is ring-shaped around the concave portion, the planar shape of the convex portion may take various shapes such as a circle, an ellipse, and a half-moon shape. In any case, this convex portion is transferred to the surface of the steel sheet during rolling, forming an inverted concave portion on the steel sheet.

As clarified in the prior invention, in order to give a steel plate excellent workability and sharpness, the surface flatness ratio (F)
It is necessary to set the value to 0.55 to 0.95.

The flat ratio (F”) of the rolling roll required to give the above flat ratio to the surface of the steel plate is 0.20 to
It is 0.90. This F'' is defined as follows.

F' = A' / (A" + B') Ao Area of the portion where the maximum height Rmax of the unevenness on the surface of the two rolls is less than 7.0 μm.

B': Same (area of the part where Rmax is 7.0 pm or more.

In FIG. 2, A1, A2, ... and B1, B2
, ... are the flat part of the roll (Rmax 7.0
If it represents the area of the area of the uneven portion (portion of Rmax7.O6m or more), then A' - A
I+A2+... (-ΣAi)B' -BI+B
2+... (-ΣBi).

A major feature of the method of the present invention is that the chromium-plated surface of the roll mentioned above is processed with regular irregularities using a laser beam or the like so that the flat ratio as described above is obtained. The chrome plating film has good adhesion and can withstand long-term rolling.

(Example) 600mmφX 1700mm l forged steel bright roll (Ra=0.2um, Rmax=2.1p
m, PPI = 50) at a temperature of 50°C, chromic acid 225g/E, and sulfuric acid 2.5g#! The substrate was immersed in a chromium plating bath, and electrolytically etched for 4 minutes at a current density of 3OA/dm2. With this process, Ra-0.5ttm,
A surface state of Rmax −6 pm and PPI =200 was obtained.

Next, in the same chromium plating bath, the polarity was reversed and plating was performed for 40 minutes at a current density of 30 A/dm.
Chrome plating was applied to a thickness of m. After washing with water and drying and confirming that there were no abnormalities, the hardness was measured and found to be Hv -1100.

The above-mentioned roll was attached to a roll grinder, and while applying an oil-based liquid abrasive containing chromium hydroxide powder to the surface of the roll, it was polished to R, IaX-1 μm using a cotton cloth huff. after that,
A concavo-convex pattern was formed on the chrome-plated surface under the following conditions.

Processing method: Laser beam Laser output...1200W Intermittent beam by mechanical chopper Atomist gas
...Average diameter of one oxygen unevenness pattern (d in Figure 1)...2008m Average interval between unevenness (l in Figure 1)...280μm Flat ratio...
-0.90 Using this roll, a rolling test of a cold rolled steel plate was conducted to examine the roll life. The rolled steel plate is an annealed material equivalent to JIS 5PCC. The rolling is temper rolling (reduction ratio: 1.0%) using the above-mentioned rolls as upper and lower work rolls. The results are shown in Table 1. The rolling amount in the table is the amount of steel plate that can be rolled before the rolls need to be replaced.

As is clear from Table 1, the rolls produced by the method of the present invention have a longer groove life than rolls without chrome plating as well as rolls with chrome plating after dulling. This is because, as mentioned above, the adhesion between the roll base material and the plating film is good, and the surface pressure applied to the dull peak during rolling does not promote peeling of the plating film.

(Effects of the Invention) According to the present invention, the service life of expensive rolls that have been precisely processed by laser beams, electron beams, etc. is further extended, and production efficiency is improved by reducing roll costs and reducing the number of roll replacements. Many practical effects can be obtained, such as improving the surface quality of the product steel sheet and making the surface quality of the product steel sheet more homogeneous.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged view illustrating the uneven pattern on the surface of a roll produced by the method of the present invention, and FIG. 2 is a sectional view taken along the line bb in FIG. 1. A + , A z . . . , B, , B2 . in FIG.
...indicate the area of the flat portion and the uneven portion, respectively.

Claims (2)

[Claims] (1) The surface of a bright roll with an Rmax of less than 7.0 μm is electrolytically etched to make it rough, then chrome plated, and then high energy density beam processing is applied to the chrome plated surface to form a regular uneven pattern on the surface. A method for producing a chrome-plated roll for rolling, characterized by: (2) After applying chrome plating, the surface Rmax7.0
Manufacture of a chromium-plated roll for rolling according to claim 1, characterized in that it is polished to a roughness of less than μm and then subjected to high energy density beam processing to form a regular uneven pattern on the surface. Method.