JPH02280907A - Rolling roll for dull working - Google Patents

Abstract

PURPOSE:To work a dull pattern on the surface of a steel plate, to improve the roll life and to impart an excellent surface treating property to the dull worked steel plate by providing very small projecting part having a specific width and height on the surface of the rolling roll. CONSTITUTION:The relation between the width W1(mm) and the height H1(mm) of the very small projecting part on the rolling roll surface for working dull pattern on the steel plate is set to W1<2>>=0.08(mm). By this method, the life of the roll for dull working on the steel surface is prolonged, the process reduction is obtained due to decrease of the roll consumption unit and decrease of the roll exchange, and further the excellent surface treating property of the dull worked steel plate is obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a rolling roll for dulling the surface of a steel plate, for example, a cold rolled steel plate, which has particularly excellent wear resistance and is most suitable for the surface of a steel plate. The present invention relates to a rolling roll that can be subjected to dull processing with desirable properties and a manufacturing method thereof.

(Conventional technology) Steel sheets are used in a wide range of fields, such as the exterior of home appliances and office equipment, but cold-rolled i+mFi is particularly easy to work with and is relatively inexpensive, so it is used as an exterior material for automobiles, etc. Used in large quantities.

There are various properties required of these steel plates, but in addition to material requirements, requests for surface properties have recently become more important.For example, the beauty of the steel plate surface, press workability, etc. , Specifically, it is largely influenced by the roughness of the surface.In general, the surface of a steel sheet is smooth (low roughness), and has a beautiful luster characteristic of metals.However, in terms of press workability and other aspects, It is necessary to have an appropriate degree of roughness, and the surface of the steel plate is often given a predetermined roughness by creating minute irregularities, which is generally called dulling. This dulling is usually done by applying a roughening process (dulling) to the surface of the work roll used for the final rolling of the steel plate, such as temper rolling, and transferring this to the surface of the steel plate by pressure. .

The shot blasting method and the electric discharge machining method are commonly used as methods for machining irregularities on the surface of the work roll (hereinafter referred to as the rolling roll).
The laser beam machining method introduced in the above publication is being put into practical use. This method is a technology in which a laser beam is modulated by a chopper blade, focused on the roll surface by a lens, the roll material is melted, and processing auxiliary gas is sprayed to flow and solidify the molten metal, forming unevenness. be. As shown in FIG. 1, the crater formed on the surface of the roll has a ring-shaped bulge (convex portion) around the periphery and is concave in the center. As shown in Fig. 4, this raised part is
The metal melted by laser irradiation is discharged from the molten pool by processing auxiliary gas and rapidly solidified.0 In normal cold rolling roll materials, the M weave in the raised area becomes a structure with a large amount of retained austenite due to the extremely short cooling time. ,
It is softer than the base metal.

Figure 2 schematically shows the surface of a steel plate (hereinafter referred to as a laser dull steel plate) that has been temper-rolled with a roll dulled by a laser as described above (hereinafter referred to as a laser dull roll). , (a) is a plan view, and (b) is a sectional view taken along the line B-R of (a). However, if the center part 2 is slightly convex or flat, the unevenness of the roller rod (the unevenness of the roll is reversed) is formed.

Laserdal steel plate has a relatively flat surface on the central plateau of the crater and the outside of the crater, and has small waviness, so it has excellent image clarity after painting (clear mapping and no distortion). . On the other hand, from the viewpoint of press workability of steel sheets, simply ensuring a flat surface is likely to cause seizure, and it can act as a trap site for oil pools and metal powder during press work.
It is necessary to have an appropriate recess. Compared to the Schottdal method, Laserdal steel plates can create larger and deeper recesses regularly, so even though the area ratio of the recesses is small, the recesses are the same or better than Schottdal steel plates. Press formability can be obtained.

In the laser dull method described above, by adjusting the shape and arrangement of the unevenness (collectively referred to as an uneven pattern or dull pattern) during laser processing of a roll, it is possible to considerably control the flatness of the steel plate rolled by the roll. Therefore, it is an excellent technique for manufacturing steel plates, etc., which have excellent coating clarity and workability.

(Problems to be Solved by the Invention) When attempting to control the flatness of the steel plate being rolled by adjusting the uneven pattern on the roll surface as described above, the crater build-up (hereinafter referred to as micro-convex portion) of the roll occurs. It is undesirable for the shape to change due to friction or plastic deformation during rolling. However, when transferring by rolling, pressure is concentrated on minute convexities, and as mentioned above, the metal structure of those parts is soft. Therefore, with laser dull rolls, as the amount of rolling increases, the minute protrusions wear out, so even if the same roll is used, the surface properties of the rolls manufactured will inevitably change. , requiring frequent roll replacement.

Furthermore, the deep and steep recesses that characterize the surface shape of laser dull steel sheets tend to make it difficult to remove oils and fats that have entered the inside even during degreasing treatment for surface cleaning.

This causes problems such as not enough chemical conversion crystals being obtained in the chemical conversion treatment following the degreasing process, and insufficient plating thickness at the bottom of the recess in the plating process.

An object of the present invention is to provide a dulling roll that can withstand long-term use without collapsing in its uneven pattern, and that prevents the uneven pattern on the surface of a steel sheet rolled by the roll from becoming extremely steep and prevents chemical formation (e.g. It is an object of the present invention to provide a rolling roll having an excellent surface quality (the ability to form a phosphate film as a coating base).

(Means for Solving the Problems) The present inventors have developed a surface unevenness pattern (
As a result of detailed investigation into the dull pattern), its durability, and the chemical formability of steel sheets rolled with such rolls, we found that
The following findings were obtained. That is, the lack of durability of the dull pattern and the poor chemical formation of the laser dull steel sheet are both caused by the steep shape of the raised portion on the roll surface. In order to solve these problems, regarding dull durability,
It is effective to reduce the surface pressure when the raised part is pressed into the steel plate during rolling, and for chemical formation, it is desirable that the concave shape of the steel plate be a smooth basin shape, and in order to obtain this desired shape. It was confirmed that the width and height of the bulges (microscopic protrusions) on the roll surface can be kept within a predetermined range.

Here, the present invention relates to a rolling roll for dulling the surface of a steel plate, which has a width W of minute protrusions on the surface, (-
m) and height H1 (mm), Wl''/H1≧0.
08 (girin)" is the gist of the roll.

(Function) Hereinafter, the present invention will be described in detail using a cold-rolled steel plate, which is the most typical type of steel plate, as an example.

The aforementioned Laser Dull Steel Sheet has a number of uniform plastic deformation phenomena occurring at the same time, as each crater bulge (microscopic convexity) formed on the roll surface by laser processing is pushed into the steel sheet by rolling. As a result, uniform dents are regularly formed in the steel plate (see Figure 2). Therefore, the durability of the roll is
It is thought that this is controlled by the stress state when the minute convex portion is pressed into the steel plate.

Figure 3 is an enlarged view of one of the craters on the surface of the laser processing roll shown in Figure 1, where (a) is a plan view and (b) is a cross section taken along line B-B of (a). It is a diagram. This figure is an almost accurate reproduction of the unevenness of an actual laser dull roll, but the cross-sectional curve near the convex part (A) is
As shown in FIG. 3(C), it can be expressed as y-Hlsin(gx/W+)...■. However, Wl : Width of the convex part (-1) Hl : Height of the convex part (-) 0≦×≦W1 Therefore, if the minimum radius of curvature at the tip of the convex part is ρ, then ρ
By differentiating the dx''0 equation and substituting X=- into it, we get 1 πtH1 ρ Wl'' πtHI.

On the other hand, the stress P at the tip of the convex part during rolling of a steel plate is A/
Since it is proportional to ρ@ (A and - are constants), by adjusting the value of ρ, it is possible to control the stress applied to the tip of the protrusion, and in turn, it should be possible to control the durability (wear resistance) of the protrusion. However, it is difficult to directly control the radius of curvature of the tip of the convex portion that is instantaneously melted and solidified by the laser beam. Therefore, the inventors thought that it is appropriate to use (Wl''/H,) as a parameter in controlling ρ. In order to clarify the relationship, rolls with various sizes of Wl and Hl were manufactured by the method described later, and after rolling a cold-rolled steel plate of 500 mm with respect to the initial convex height Hl. As a result of investigating the ratio (H,''/H-) of the raised height H,+'' of the roll convex portion, it was found that excellent durability was obtained when (Wl''/H1)≧0.08 (as). I found out.

As mentioned above, if the width and height of the minute protrusions formed on the roll surface are adjusted, the radius of curvature ρ at the tip of the protrusion becomes large, which not only improves wear resistance but also increases the The surface properties of the rolled steel sheet are also improved.

That is, the cross-sectional shape of the recess of the steel plate to which the smoothly raised dull shape of the roll is transferred also becomes smooth, resulting in improved degreasing properties. The quality of the degreasing treatment affects the chemical formability of the next step. Therefore, we investigated the relationship between the concave shape and the chemical formability of the steel plates that were trial rolled using rolls with various convex tip curvatures manufactured in the tests described above.

The chemical conversion property was evaluated using a SEM (scanning electron microscope) after a chemical conversion treatment was carried out in accordance with the usual painting pretreatment process of performing a zinc phosphate treatment after a degreasing process.

In addition, chemical conversion coating M (phosphate coating) is used as a base for painting.
It is preferable that there is no unevenness in appearance and that the surface is densely covered with microscopically fine phosphate crystals.Therefore, the chemical conversion properties were evaluated based on the degree of coverage and the size of crystal grains.

From the results of this investigation, the following conclusions were drawn. That is, the second
Figure (C) is an enlarged view of the concave portion in Figure (b).
Here, if Wl + width of dent (definition) h,: depth of dent (mm), the steel plate with (w, ”/h+)≧0.1 (-1) is particularly susceptible to chemical formation. Excellent, but usually 0
．． If it is 08 or higher, there is no problem with the quality of the electrodeposition coating in the next step.

Steep concave shapes do not allow sufficient degreasing within a limited time, so oils such as rust preventive oil are carried into the chemical conversion treatment process, and the chemical liquid and the steel plate surface cannot come into sufficient contact, resulting in formation of chemical crystals. It becomes coarse and sketchy. However, in a steel plate having a concave shape that satisfies the above formula, the concavity has a smooth cross-sectional curve, and degreasing progresses easily.

The shape of the concave portion of the steel plate is the reversed shape of the convex portion of the roll and transferred thereto. Since the transfer rate changes depending on the rolling reduction rate, the sizes of the concave and convex parts are not the same, but the relationship (Wl''/H1)ζ(wt''/h+) holds.Therefore, the above-mentioned W+''/H+ The shape of the concave part of the steel plate rolled with a roll whose is 0.08 or more is
It satisfies the relationship (W, "/h,)≧0.08, and has excellent chemical conversion treatment properties.

Next, a method for manufacturing the mill roll of the present invention will be described.

FIG. 4 conceptually shows how the surface of the roll is textured with a laser beam. The metal melted by the laser beam is removed from the molten pool by the processing auxiliary gas, and solidifies in a bulge around it. Oxygen is usually used as a processing auxiliary gas, but in that case, (
As shown in a), a violent oxidation reaction occurs in the molten pool, and the molten metal is expelled to the surroundings, forming a ring-shaped bulge. However, according to the test results of the present inventors, if an inert gas is used as the processing auxiliary gas, the bulge will be biased to one side and the shape will be a smooth crescent-shaped mountain, as shown in Figure 4(b). Becomes a department. The radius of curvature of the peak portion becomes large, and a convex portion satisfying the relationship (wt”/U+)≧0.08 (mm) can be easily obtained.

In conventional laser dull processing, in order to process rolls with higher efficiency, high bulges can be obtained by using oxygen as a processing auxiliary gas and inducing a combustion reaction in the molten metal by laser irradiation, as described above. is being carried out. When oxygen is used as the machining auxiliary gas, as mentioned above, the shape of the raised part becomes ring-shaped, resulting in Wl being small compared to H2, the radius of curvature of the tip decreasing, and good durability not being obtained. On the other hand, if an inert gas is used as the processing auxiliary gas, the oxidation reaction will not occur in the bulge formation process by laser dull processing mentioned above, and the molten metal will not be spread around, but will be melted only by the dynamic pressure of the gas. Since the gas is discharged from the pond, the gas is blown along the direction, forming uneven bulges and L-bent parts, resulting in a smooth bulge with a large radius of curvature at the tip.

In addition, in terms of formability, laser dull steel sheets have
If the area and depth of the recessed portion is extremely small, it will not function as a trap site for oil pools and fine metal powder during press processing, and mold galling will occur easily (the inventors of the present invention Dull processing was performed under the following laser processing conditions by changing only the processing auxiliary gas, and the resulting ring-shaped and crescent-shaped craters were trial rolled into steel plates, and the press formability and paint clarity were investigated. As a result, it was confirmed that even if the convex part of the roll was crescent-shaped, it had the same properties as a steel sheet rolled with a conventional roll having a ring-shaped convex part.

An inert gas such as nitrogen or argon is preferable as a processing auxiliary gas to obtain a crescent-shaped crater, but
When the laser irradiation energy is not extremely large, (W12/H1) gradually increases as the oxygen partial pressure decreases. According to the experimental results, the oxygen content is 25 vol.
If the inert gas is 1% or less, (W,”/H1)≧0
．． A shape of the convex portion satisfying 08 can be obtained. Thus, for example, air may be used as a processing auxiliary gas.

(Example) A laser dull roll was produced under the following conditions, and its convex shape (W12/H+) and wear resistance (H,'''/■-),
and the concave shape (wl) of the steel plate rolled by those rolls.
”/h+), image clarity, chemical conversion properties, and processability.

■ Roll material: JIS 5UJ-2 steel ■ Roll processing method; A Laser dull processing (processing auxiliary gas...oxygen) B
Laser dull processing (processing auxiliary gas: nitrogen or a mixed gas of nitrogen and oxygen) However, laser dull processing uses a carbon dioxide laser oscillator with an output of 2KH, and a chopper with a frequency of 10KIz.
A pulsed beam was oscillated, and this was focused on the roll surface by a lens. The processing auxiliary gas has an inner diameter of l at the beam focal point.
It was sprayed from a -φ nozzle.

■ Steel plate: JIS331G 5PCIIS material, plate thickness ll-■ Rolling conditions: One pass of temper rolling was performed at a rolling reduction of 0.8%.

[F] Wear resistance test conditions] The roll surface roughness (three-dimensional profile) was measured immediately after laser dulling and after the above steel plate was rolled, and the height of each minute convexity was determined by H-51. - ratio (I
ll"/H1@). 90% or more was considered good.

■ Test conditions for sharpness: Similar to the painting of automobile exterior panels, cationic electrodeposition coating (20 μm), intermediate coating (35 μm tin), and top coating (35 μm) were applied after dipping.
The sharpness of the painted plate coated with μ-) was evaluated using a PG gauge (manufactured by Nippon Color Research Institute). Both the chemical agent and the paint are commercially available for automobiles.

■ Test conditions for chemical conversion: After degreasing by immersion in a commercially available automotive degreaser for 2 minutes, immersion in an immersion zinc phosphate treatment agent for 2 minutes, washing with water and drying, SEM
The state of zinc phosphate crystals was observed and evaluated. The evaluation was made as "x" if the chemical crystals were coarse or had a slit to which no crystals were attached, and "O" if the product was good.

■ Test conditions for press workability: Evaluation was performed using the limit drawing ratio (LDR) in a cylindrical drawing test. A rating of 2.2 or higher was considered good.

The above results are summarized in Table 1.

From Table 1, (w12 /Ht )≧0.08・(Peng■
) The roll of the present invention that satisfies the conditions has excellent wear resistance,
Furthermore, it can be seen that the steel plate rolled with the rolls has good chemical formability.

(Effects of the Invention) The present invention extends the life of rolls for dulling the surface of steel plates, and produces great benefits such as reducing the unit consumption of rolls and shortening the process by reducing the number of roll changes. Moreover, the cold-rolled steel sheets, hot-rolled steel sheets, plated steel sheets, etc. that have been dulled using the rolls of the present invention have excellent surface treatment properties in chemical pretreatment for painting bases and the like.

[Brief explanation of drawings]

Figure 1 is an enlarged schematic diagram of the surface of a laser dull roll. Figure 2 is an enlarged schematic diagram of the surface layer of a dull steel plate rolled by a laser dull roll. -B
FIG. Figure 3 is an enlarged view of one of the craters on the surface of the laser processing roll shown in Figure 1, where (a) is a plan view and (b) is a cross section taken along line B-B of (a). Figure, (C) is (b)
This figure shows an approximate cross-sectional curve near the convex part.

Claims (1)

[Claims] A rolling roll for dulling the surface of a steel plate,
The width W_1 (mm) and height H_1 (
mm) has the following relationship. W_1^2/H_1≧0.08 (mm)