JPS6310013A - Dull roll for cold rolling - Google Patents

Abstract

PURPOSE:To improve the wear resistance of a dull roll by comprising the micro configuration of a rough surface of recesses, embossed parts, and flat parts and specifying the area ratio of the flat parts. CONSTITUTION:Embossed parts 2 having a nearly uniform height around recesses 1 on the surface of a roll 3 are pressed onto the surface of a steel stock 7 by a strong pressure. By that pressing, local plastic material flows are generated in the vicinity of the surface of the stock 7 whose material is softer than that of the roll 3, so that the metal of the stock 7 flows into the recesses 1 of the roll 3 to form a rough surface. In that time, the top surfaces of the steel sheet metal embossed inside the recesses 1 become flat faces 8 being unchanged as the initial steel sheet surface. Surface parts 9 of the stock 7 pressed against flat parts 6 outside the embossed parts 2 between adjacent recesses 1 do not change and become flat faces 9. Then, the height of the flat faces 8 is higher than or equal to that of the flat faces 9. The flat parts 6 (nonmachined) are very effective for the wear resistance of a dull roll, so that the area ratio of the parts 6 is made to be 0.2 or more.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a dull roll used as a work roll of a cold rolling mill, and in particular specifies the microscopic form constituting the rough surface, and The present invention relates to a dull roll with improved wear resistance by specifying the area ratio of the flat part that constitutes a part of the shape.

[Prior Art] In general, in belt cold rolling, a dull roll subjected to dull processing is used as a work roll of the final stand of a tandem rolling mill. The surface roughness Ra of this dull roll is set to about 2.0 to 4.0 μm. This is to stabilize the rolled shape.

Further, annealing is performed after cold rolling, and there are two types of annealing: batch annealing and continuous annealing, which are appropriately selected depending on conditions such as the steel type. In batch annealing, the copper strip is annealed in a coiled state, so the steel strips may stick together due to seizure. As a means to prevent this adhesion, dulling the steel strip using the dull roll is effective. In continuous annealing, the length of the steel strip bus in the looper and annealing furnace is long, and therefore the copper strip tends to meander; however, forming dowels in the copper strip is effective in preventing the meandering.

Conventional dull rolls have a rough peripheral surface formed by shot blasting or electrical discharge machining.

Shot blasting is a process in which hard particles such as iron powder are projected onto the circumferential surface of a roll after grinding and polishing to create fine uneven impressions, and electric discharge machining is a process in which a roll is placed opposite the circumferential surface of the roll. A spark discharge is generated between the roller and the electrode, thereby creating fine irregularities on the circumferential surface of the roll.

[Problems to be Solved by the Invention] However, in the job-dplast processing, the grid is mechanically collided with the roll circumferential surface to plastically deform the roll circumferential surface and create unevenness. Although it is work hardened, the convex part has an acute angle and the peak area is small, so the convex part wears quickly during cold rolling.
Therefore, there is a problem that the plate surface roughness after rolling also decreases.

Also, depending on electrical discharge machining, the area of the peak of the convex part can be made relatively large, but the roll surface has a molten layer and a tempered layer, and therefore the roll surface has low hardness, resulting in severe roll wear during rolling. There is also a problem.

Therefore, as a solution to this problem, the Japanese Patent Laid-Open No. 5
There have been disclosed products subjected to sub-zero treatment as described in Japanese Patent Application Laid-open No. 1-456143, and products provided with a nitrided layer as described in Japanese Patent Application Laid-Open No. 55-19403. There are disadvantages such as increased process steps.

The object of the present invention is to solve these problems and provide a dull roll that has excellent wear resistance and is easy to manufacture.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the dull roll of the present invention has the following features: (C) a raised part raised along the edge of the recessed part of (C) a flat part outside the raised part of said mountain);
(2) and the area ratio of the flat portion of (C) was set to 0.2 or more.

[Effect]

The bulges around the recesses on the surface of the dull roll are pressed against the surface of the steel plate to be rolled with strong pressure, and this causes local plastic flow of the material near the surface of the steel plate, which is softer than the material of the dull roll. The metal of the steel plate flows into the recesses, forming a rough surface on the steel plate.

At this time, the peak surface of the steel sheet metal that rose inside the recess becomes a flat surface as it is on the original steel sheet surface, and the part of the steel sheet surface that is pressed against the flat part of the dull roll remains a flat surface, and the former's flat surface remains flat. The surface may be higher than or the same height as the latter flat surface.

If the above-mentioned rolling is continued, the wear progresses at the raised portion where the pressure on the steel plate is highest.
Since the surface of the flat part of the dull roll is the same as the circumferential surface of the roll in a ground or polished state before being dulled,
Each part of this flat part comes into contact with the steel plate with uniform pressure, and therefore the flat part is in a state where it is difficult to wear. For this reason, after the wear of the raised portion progresses and its surface reaches the same height as the flat portion, the wear of the dull roll rapidly decreases.

However, since the amount of steel sheet metal flowing into the recesses increases in accordance with the amount of wear on the raised portions, changes in the roughness of the steel sheet surface are suppressed to a small extent, and stable roughness can be obtained.

In addition, if the area ratio of the flat part of the dull roll is less than 0.2, the wear of the roll becomes severe and the reduction rate of the roughness of the copper plate becomes extremely high. However, the dull roll of this invention has an area ratio of the flat part of Since it is set to 0.2 or more, the wear resistance is maintained at a high level.

〔Example〕

Examples of the dull roll according to the present invention will be described below.
This will be explained with reference to the drawings.

(1) Regarding forming a dull roll using a laser, first, a high-density energy source such as a laser is used to dull the work roll of the final stand to form a dull roll.

That is, while rotating the roll, laser pulses are sequentially projected onto the surface of the roll, and the laser energy regularly melts the roll surface to form four regular crater-shaped parts. This situation is shown in Figure 1, where 1
is a crater-shaped recess formed on the surface of the roll 3, and around the recess 1, molten roll base metal rises in a ring shape from the surface of the roll 3 to form a raised portion 2. The inner wall layer of the concave portion l including this raised portion 2 serves as a heat affected zone 5 with respect to the roll base material composite fiber 4.

The metal heated by the laser instantaneously turns into metal vapor due to the large irradiation energy density, and the vapor pressure generated at this time blows off the molten metal on the roll surface to form the recess 1, and the blown molten metal is re-fixed around the recess 1, forming a ring-shaped raised portion 2 along the edge of the recess 1. Therefore, compared to forming a rough surface by electric discharge machining, the machining speed is faster, there are fewer heat-affected zones, and the raised portion 2 is cooled quickly so that it does not soften much.

The roughness of the surface of the roll 3 thus formed is shown in FIGS. 2 and 3. As is clear from these figures, the outer part of the raised part 2 between the adjacent recessed parts 1 remains the original roll surface and becomes a flat part 6.

Here, the distance between adjacent recesses 1 is determined by controlling the frequency of the laser pulse in relation to the rotational speed of the roll in the rotational direction of the roll, and by controlling the frequency of the laser pulse in relation to the rotational speed of the roll in the axial direction of the roll. This can be adjusted by controlling the pitch of moving the laser irradiation position in the roll axis direction.

The above description has been made regarding the case where a laser is used as the high-density energy source, but the same applies to the case where other high-density energy sources such as plasma or electron beams are used.

Note that the dull roll has been dulled using a high-density energy source, but the dull roll of this invention is characterized by its structure, and the manufacturing method described above is only a typical manufacturing method. Therefore, the present invention provides the above-mentioned recess 1. Swelling part 2. As long as it is a dull roll in which the flat portion 6 is formed, rolls manufactured by other methods are not excluded. In addition, the raised portion 2
is ring-shaped, but this raised portion 2 also includes one in which a part of the ring is interrupted and the entire ring is not continuous.

(2) Regarding dull rotation transfer to a steel plate by cold rolling, a work roll subjected to dull processing as described above,
By performing rolling using the final stand of a tandem rolling mill, the dowels of the rolls are transferred to the surface of the steel sheet, and a rough surface is formed on the surface of the steel sheet.

If we microscopically observe the surface of the steel plate during this process, as shown in FIG. As a result, local plastic flow of the material occurs near the surface of the steel plate 7, which is softer than the material of the roll 3, and the metal of the steel plate 7 flows into the recess 1 of the roll 3, forming a rough surface. At this time, the top surface 8 of the steel sheet metal raised inside the recess l becomes a flat surface with the original surface of the steel sheet, and is also pressed against the flat part 6 on the outside of the raised part 2 between the adjacent recesses 1 on the roll 3. The portion 9 of the steel plate surface that has been removed remains a flat surface, and the former flat surface 8 is higher than or has the same height as the latter flat surface 9.

However, as the rolling continues, wear progresses in the heat-affected areas 5, especially in the raised areas 2. This is schematically shown in Fig. 5, and as the rolling length increases, the profiles of the roll 3 and the steel plate 7 change as shown in Fig. 5(a).
5(1)), and finally the raised portion 2 disappears as shown in FIG. 5(C).

By the way, dull rolls are manufactured by hardening and polishing the rolls, and then subjecting them to dull processing. Therefore, in the dull roll of the present invention, since the surface of the flat portion 6 is the surface of the original roll, it is less likely to wear out. Therefore, when rolling continues and the state shown in FIG. 5(C) is reached, the wear decreases rapidly. Furthermore, even if the raised portion 2 disappears, the amount of steel plate 7 flowing into the inner side of the recess l increases, so the change in the plate surface roughness is not so great compared to the state shown in Figure 5 (al (bl), so the raised portion A stable roughness can be obtained regardless of whether the portion 2 is worn out.

On the other hand, the roll surface that has been dulled by shot blasting or electric discharge machining has an irregularly rough surface with very few flat areas, so it wears quickly and the surface roughness also decreases. Changes greatly. FIG. 6 schematically shows the wear condition of this roll.

(3) Regarding the area ratio of the flat part of the dull roll, as mentioned above, it was found that the flat part 6 (unprocessed part) is very effective for the wear resistance of the dull roll, but the proportion of this flat part 6 to the whole , that is, how the area ratio affects wear resistance will be explained.

In FIG. 7, the average distance between the centers of the recesses 1 is Sm, (μ
m), the diameter of the concave portion l is d (μm), and the diameter of the raised portion 2 is D (μm), then the area ratio η of the flat portion 6 is calculated by the following formula.

(In the case of Sm≧D) (In the case of Sm<D) By changing the processing conditions in laser dull processing, it is possible to change the area ratio η of the flat portion 6 by changing the above Sm and D. .

Figure 8 shows the results of investigating the relationship between the rolling length and the surface roughness of the rolled copper strip using two levels of area ratio η of the flat portion 6 of 0.2 and 0.5 by laser dulling. There is.

Note that the dotted line also shows the case where dull processing was performed by shot blasting. Both have the same roughness after dulling. From this, it can be understood that in the case of laser dulling, the roll wears out rapidly after rolling starts, and thereafter the roll wear hardly progresses, and the plate surface roughness remains stable. On the other hand, in the case of shot blasting, the rough surface of the dull roll is work hardened, so the amount of wear after the start of rolling is less than that of laser dulling, but even if the rolling length becomes longer, the wear continues as before. I can understand that.

Moreover, FIG. 9 shows the reduction rate of the plate surface roughness when the copper strip is rolled by 10 kn+. As a result, the area ratio of the flat portion 6 is 0.
It can be seen that there is an inflection at 2.

That is, when the area ratio of the flat portion 6 exceeds 0.2, the rate of decrease in roughness of the rolled steel sheet surface becomes low. Therefore, if the area ratio η of the flat portion 6 is set to 0.2 or more, the wear resistance of the dull roll will be improved.

In addition, as mentioned above, the surface roughness Ra of the conventional dull roll
is about 2.0 to 4.0 μm, but since the roll according to the present invention has a regular surface morphology, the surface shape of the steel sheet after rolling also becomes regular, and therefore the surface roughness range can be further expanded.

However, if the diameter is smaller than 1.0 μm, adhesion will occur during batch annealing, and if the diameter is larger than 4.0 μm, the effect will not be as significant, and the required energy will increase, resulting in an economical disadvantage. Degree Ra is 1.0 ~
The thickness is preferably 4.0 μm.

〔Effect of the invention〕

As explained above, according to the present invention, by specifying the microscopic form of the dull roll and the area ratio of the flat part,
A dull roll for cold rolling with excellent wear resistance could be obtained. Furthermore, since this dull roll can be formed by projecting a high-density energy source such as a laser beam, it also has the advantage that its manufacturing method is simple.

[Brief explanation of drawings]

Fig. 1 is an enlarged sectional view of a dull roll showing an embodiment of the present invention, Fig. 2 is a schematic sectional view showing the rough surface profile of the dull roll surface of Fig. 1, and Fig. 3 is a plan view of Fig. 2. , FIG. 4 is a schematic cross-sectional view of the state in which the dull rolls of FIGS. 1 to 3 are used as work rolls for temper rolling, and FIGS. 5(a) and 5('b). Figure 6 (C) is a cross-sectional view showing the relationship between the wear of the raised portion of the dull roll and the change in the rough surface of the steel plate, and Figure 6 (a).
), (b), and (C) are cross-sectional views sequentially showing the wear progress of the dull roll surface that has been dulled by shot blasting and electric discharge machining, respectively, and Fig. 7 is an explanation of the area ratio of the flat part of the dull roll. 8 is a graph showing the relationship between the rolling length and the roughness of the plate surface, and FIG. 9 is a graph showing the relationship between the area ratio of the flat part of the dull roll and the reduction rate of the plate surface roughness. Sm...average distance between centers of peaks, D...average distance between centers of valleys, d...average diameter of top surfaces of peaks, 1...
Concave portion, 2... Raised portion, 3... Roll, 4...
・Base metal structure, 5... Heat affected zone, 6... Flat area, 7.
...Steel plate, 8... Top surface, 9... Flat surface

Claims (1)

[Claims] In cold rolling dull rolls that have a rough peripheral surface and are placed in the final stand or final pass of a cold rolling mill, the microscopic form that constitutes the rough surface is a crater-shaped recess and the edge of this recess. 1. A dull roll for cold rolling, comprising a raised part raised along the ridge and a flat part outside the raised part, and wherein the flat part has an area ratio of 0.2 or more.