JPH06279B2 - Method for manufacturing dull roll for rolling steel sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to the production of a dull roll for rolling a steel sheet for producing a steel sheet having good formability in pressing and the like and having a bright luster and a matte surface. Regarding the method.

[Conventional technology]

Among cold steel sheets, a material that is subjected to a forming process by a pressing machine or the like usually has innumerable minute irregularities formed on the surface thereof. This innumerable minute uneven pattern is called a dull, and the surface of the dull-finished steel plate has a matte surface called a matte skin.

This is because the surface of the steel sheet is dull-finished, for example, in order to prevent the seizure with a die or the like and to improve the formability by allowing the lubricant to stay in the minute irregularities on the surface of the steel sheet during press working. To do this, the work roll surface at the time of temper rolling is preliminarily dull processed, and this work roll is pressed to transfer the dull pattern to the steel plate surface. Further, in order to perform dull processing on the work roll surface, hitherto, a shot blasting method in which steel grit is projected onto the roll surface at high speed to form irregularities, or discharge between the roll surface and the electrode in an insulating liquid An electric discharge machining method in which the surface is melted by electric discharge energy to form irregularities has been put into practical use.

[Problems to be solved by the invention]

However, the shape of the minute irregularities on the roll surface formed by the conventional shot bright method or the electric discharge machining method is such that, as shown in the sectional characteristics shown in FIG. Does not exist. The concavo-convex pattern of the steel sheet transferred by such a roll gives a perfect matte surface, and the luster of the steel sheet surface disappears at all. When such a steel sheet is coated, the gloss reflectivity after coating and the distortion of the image are generated, resulting in a marked decrease in commercial value.

Cold-rolled steel sheets are applied with paint after press forming to become products such as automobile bodies, but in recent years, sharpness after painting has been emphasized as a product. It is said that the evaluation of the sharpness is excellent as it has less irregular reflection, has a reflection characteristic closer to a mirror surface, and has less distortion of the image and an accurate and clear image. Although this is an evaluation after coating, it is also affected by the coating technology, but it is greatly affected by the dull of the cold-rolled steel sheet as the coating base, that is, the size and shape of the irregularities.

In the conventional dull pattern by the shot blasting method and the electric discharge machining method, as shown in Fig. 2, irregular irregularities are already continuous and there is no flat portion, so the coating film is formed along the slope of the irregularities. As a result, specular reflection and sharpness are deteriorated.

Also, in temper rolling, the unevenness of the roll surface is pressed against the steel plate surface to form a matte surface, but with the increase in the number of transfers, the projections on the roll surface wear away and become wavy. It is different from the pattern. This change also significantly reduces the commercial value. This abrasion depends on the hardness of the roll surface, and the harder it is, the less abrasion is. However, the shot blasting method, which is a conventional processing method, cannot in principle increase the roll surface hardness beyond the hardness of the projected grit. Therefore, the roll surface hardness is limited by itself. Further, in the electric discharge machining method, the roll surface hardness is not restricted, and if the material of the roll surface is a conductor, pattern processing is possible. However, the roll used for general temper rolling is a material called high carbon forged steel quenching roll and has a martensitic structure, but since it is heated to high temperature by receiving discharge energy during processing, this martensite is austenitic. Be converted. Since the austenite structure is soft, the hardness of the austenite structure is drastically reduced, and the projections are worn away at an early stage, requiring frequent roll replacement. FIG. 3 shows the change in roll hardness by the electric discharge machining method.

The present invention has been made in consideration of such problems caused by the size and shape of the conventional unevenness and the problem of pattern nonuniformity due to abrasion of the unevenness of the work roll surface. It is an object of the present invention to solve the above-mentioned problems by polishing the hard chrome plating described above and then forming an uneven pattern by high-density energy radiation.

[Means for solving problems]

The present invention relates to a work roll for cold rolling or temper rolling of a steel plate, after hard chromium plating is applied to the surface of the work roll, the center line average roughness of the plated surface is Ra.
This is a method for producing a dull roll for steel plate rolling, in which polishing is performed so that ≦ 0.3 μm, and thereafter, crater-shaped minute recesses are formed on the plated surface by high-density energy radiation.

[Action]

When performing dull processing on the surface of the work roll for steel plate rolling, first apply hard chrome plating on the roll surface, and then
Since the plated surface was polished so that the center line average roughness Ra ≦ 0.3 μm, the work roll surface was extremely hard and formed into a flat surface close to a mirror surface. By forming crater-shaped minute recesses on such a flat surface by high-density energy radiation, a work roll having both a flat surface close to a mirror surface and a dull pattern is obtained. Therefore, when the steel sheet is rolled by this roll, a flat surface and a dull pattern which are close to a mirror surface are transferred to the steel sheet, so that a coated surface which is excellent in gloss reflection after coating and has no image distortion can be obtained. Further, since the surface of the roll is extremely hard, the formed dull pattern has high abrasion resistance.

〔Example〕

An embodiment of the present invention will be described below with respect to a work roll for temper rolling and a dull working method having a flat portion.

A general work roll for temper rolling is a high carbon forged steel quenching roll, and its surface hardness is Hv = 850 at the maximum.
Therefore, at this level of hardness, abrasion of the dull convex portion is likely to occur, and after the start of rolling, the original dull pattern changes into a wavy uneven pattern in a short time, and the quality of the steel sheet rolled by this roll is improved. Unevenness is not preferable. Therefore, after the roll surface is hard chrome plated before the dull processing, the plated surface is finished by buffing or the like to be a mirror surface.

The hardness of the hard crawling surface is Hv ≦ 1000, which is extremely hard and has excellent wear resistance, and the initial dull pattern does not change even after a long time has passed after the start of rolling. Here, the thickness of the chrome plating is selected in the range of 5 μm to 100 μm in proportion to the size of the unevenness formed by the next dull process.
Further, the surface roughness of the roll after polishing by buffing or the like is such that the center line average roughness Ra ≦ 0.3 μm.

Next, in order to improve the regular reflection property and sharpness of the rolled steel plate, it is the weight that the uneven portion transferred to the surface of the steel plate as the coating base is reduced and the proportion of the flat portion is increased. As such a dull processing method, a dull processing method using a laser pulse is adopted in this embodiment. This laser processing method is a method of rotating a work roll, which has been hard chrome plated and polished as described above, at a predetermined speed, and one method is to move a laser oscillator along the rotation axis of this roll to regulate laser. This is a method of forming minute recesses (craters 1) in a regulated arrangement on the roll surface by irradiating with a pulse. On the surface of the roll irradiated with the laser, the chrome metal layer instantly becomes vapor due to the large radiant energy of the laser, and the molten chrome is blown off by the vapor pressure generated at that time, and the crater 1 as shown in FIG. Is formed. The depth and diameter of the crater 1 are determined by the energy level of the projected laser and the projection time, and the selection is made in consideration of the degree of forming strictness of the steel plate rolled by the roll due to press working or the like. Normally, the size of the crater 1 is 10 μm to 500 μm in diameter and 3 μm to 50 μm in depth.

Also, the crater 1 that does not receive the laser irradiation on the roll surface
The remaining part remains as a flat part 2 that is polished close to the mirror surface, and this part is transferred as a mirror surface to the steel plate surface during temper rolling, which greatly improves the reflectivity and sharpness after painting. .

〔The invention's effect〕

As described above, according to the present invention, the effects shown in Tables 1 and 2 below can be obtained.

Table 1 shows the values measured by a drigon meter, which is one of the evaluation methods for reflectivity and sharpness, that is, DOI (Distinctness).
of image) values are compared among various dull processing methods.

This comparison was made with samples aligned with the same level of average roughness Ra, but this example increased by 5 points compared to the conventional shot blast method and discharge energy method,
Further, it is shown that even in the same laser energy method, in the case of using a roll whose surface is polished after hard chrome plating as in this embodiment, it is superior to the conventional laser energy method by 2 points.

Table 2 is a comparison of the above processing methods according to the length of the steel sheet rolled by the work roll replacement due to wear of the dull in temper rolling, but the method according to the present invention is compared with the conventional example. Indicates a 12-fold extension of life.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a work roll surface processed by the method of the present invention, FIG. 2 is a view showing a cross section and a plane characteristic of a roll surface according to a conventional example, and FIG. 3 is a work roll surface according to a conventional example. It is a figure which shows the hardness of. 1 ... Crater-shaped minute recesses, 3 ... Chrome plating layer, 4 ... Work roll

Claims (3)

[Claims] 1. In a work roll for cold rolling or temper rolling of a steel sheet, after the surface of the work roll is hard chrome plated, the plated surface has a center line average roughness of R.
A method for producing a dull roll for rolling a steel sheet, which comprises performing a polishing process so that a ≦ 0.3 μm, and then forming a crater-shaped minute recess on the plated surface by high-density energy radiation. 2. The hard chrome plating thickness after polishing of the plated surface is in the range of 5 μm to 100 μm, and the crater-shaped minute recesses formed on the plated surface by high-density energy radiation have a diameter of 10 μm. 〜500 μm, depth is in the range of 3 μm to 50 μm.
A method for producing a dull roll for rolling a steel sheet according to the item. 3. The method for manufacturing a dull roll for rolling steel sheet according to claim 1 or 2, wherein the high-density energy emission is performed by a laser.