JPH0765226B2 - Method for producing Cr-plated roll for rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an improvement in a method for producing a Cr plating roll for rolling.

[Conventional technology and its problems]

In the rolling of non-plating rolls, since the rolls have flaws at the edge portions of the rolled material, rolling is generally performed in the order of narrow-width to narrow-width, which is called narrow-down.

On the other hand, even when rolling with chrome-plated rolls, which have high wear resistance, if a large amount of material with the same width is rolled at a point when the roll roughness wear at the initial stage of use is fast, a large degree of roughness will occur on the rolls in the threaded and non-threaded areas. A difference occurs. For this reason, when a steel sheet exceeding this width is rolled, an edge mark-like gloss difference occurs,
It becomes an obstacle to schedule-free (width-free) rolling.

The present invention has been made in order to solve the above problems, in the manufacturing process of the Cr plating roll for rolling, by performing the roll surface treatment, to reduce the roll initial wear rate, easy schedule-free rolling The purpose is to

[Means for solving problems]

 The present invention will be described in detail below.

The present inventors have devised the present invention as to whether the difference in roughness of the roll surface occurs in the early stage of use of Cr-mekki roll, because the peeling of a large number of roughness peaks present on the roll surface is the cause.

That is, as shown in FIG. 2, the roughness pattern of the surface of the Cr plating roll has many roughness peaks on the roll surface side, and these peaks are peeled off at the beginning of use, so that the roughness of the roll is extremely worn. Fast. Therefore, as described above, a large difference in roughness occurs between rolls in the threaded portion and the non-threaded portion due to mass rolling of the same width material, and edge mark-like gloss difference occurs in the schedule-free rolling.

Therefore, the present inventors considered that if the roughness peak portion of the surface of the Cr plating roll was smoothed from the beginning, the initial wear rate during use of the roll could be reduced.

Generally, the metal material of the object to be plated has a surface different from the internal structure / structure of the material (1) by machining (cutting, polishing, impact, forging, drawing) as shown in FIG. There is a processed layer (3) in a state, and between the processed layer (3) and the material (1) is a diffusion layer (2) in which these structures are mixed. Although the thickness of the processed layer (3) varies depending on the processing history and is not uniform, the thickness (Bailby layer) generated by ordinary polishing is Å unit. Further, on the processing layer (3), there is an oxide layer (4) formed on the surface when the material is exposed to the air, and on top of that, rust and extremely fine soot adhered to the surface of the metal material. There is a layer (5) of smatt which consists of a powder of the form. The outermost layer has a dirt layer (6) which is an adhesion layer of dust, oil and fat scattered in the air, machine oil used for processing, and rust preventive oil applied to prevent rust. .

Therefore, in the manufacturing process of normal Cr metallurgy,
After effectively removing the dirt layer (6) by a degreasing process,
After washing with water, the rust / smut layer (5) and the oxide layer (4) are removed by an etching process. In such an etching process, the roll surface is slightly dissolved by electrolyzing the roll in a solution of chromic anhydride and sulfuric acid (chromium plating solution), and the plating adhesion in the subsequent Cr plating treatment step is improved. Although it is intended to improve the processed layer (3) and the diffusion layer (2) below the layer (4), these are the metals themselves and need not be removed, and in the case of a smooth surface the surface Is not actively removed because it may be roughened (however, since the processed layer (3) is eventually removed, it is called etching).

The present invention, particularly the etching step is performed at a high current density and / or for a long time in the above steps performed before the Cr plating treatment, and in the roll surface to be the electrode, in the peak portion of the roughness which becomes the strongest of the electrolytic action. , Not only the oxide layer (4) and the workpiece layer (3) but also the diffusion layer (2) and part of the material (1) are removed, and the roughness peak is smoothed as shown in FIG. , And then Cr plating was performed.

Next, the inventors of the present invention conducted an experiment to compare the roughness wear of Cr metallurgy produced by a normal method and Cr metallurgical roll whose surface roughness was lowered during the etching process. For each of these rolls, a forged steel roll having a diameter of 530 mm was used, and the thickness of each plating was set to 8 μm, and the roughness Rz of the Cr plating roll by the usual method was set to 17 μm. On the other hand, in the etching process before plating, the surface roughness is
Cr Electrolytic treatment is performed to reduce roughness Rz of Metsukeru by 5%, 20% and 30%, and then Cr with a thickness of 8 μm.
The matted ones were used for the experiments with the usual Cr metkilol. Furthermore, annealed mild steel was used as the material to be rolled, and the wet pressure was adjusted at an elongation of 0.5 to 1.5%.

As a result of the above pressure adjustment, the results shown in FIG. 4 were obtained.
This figure shows the relationship between the pressure adjustment distance and the roll surface roughness.
The reduction rate of surface roughness due to etching is 5% to 20% in Rz
When changed to, the decrease in the roll surface roughness at the beginning of use of the roll becomes gentle. Due to the gradual decrease in roughness, even if a large amount of the same width material is rolled at the initial stage of roll use, the difference in roll roughness between the threaded portion and the threaded portion is more than that of the chrome plated roll. Less. However, if the rate of decrease in surface roughness due to etching is 20% or less, no effect on roll life is observed. Whether it is hot rolling, cold strong reduction rolling, or cold light reduction rolling (pressure adjustment), the rolling roll has a surface property (for example, texture, roughness) of the material to be rolled within a predetermined range. To be within
It is necessary to maintain the surface of the rolling roll for roughness within a predetermined range from the initial rolling stage to the latter rolling stage regardless of the timing. Especially in case of temper rolling for cold-rolled steel sheet, it should have appropriate roughness in terms of pressability, paintability, image clarity after coating, plating ability, and transportability after pressing (load collapse, scratch prevention). In addition, the predetermined range is defined. For this reason, the roll roughness before plating and the roughness as a plating layer by Cr plating are adjusted to a predetermined value in advance (of course, in the case of the adjustment of the etching of the present invention, it is also taken into consideration. become). However, when the reduction rate of the surface roughness due to the above-mentioned etching reaches 30%, the range of roughness tolerance of a predetermined range is narrowed to start the use (initial use). Even if the effect of lowering the roughness is obtained, since the usable tolerance is narrow, the roll life is shortened. In addition, the rate of decrease in surface roughness due to etching is 5
If it is less than%, the roughness decreases rapidly at the beginning of roll use, and the object of the present invention cannot be achieved.

Therefore, in the method of the present invention, a Cr plating solution consisting of chromic anhydride and sulfuric acid is used in the etching step, and the roll is used as an anode to carry out an electrolytic treatment for reducing the roll surface roughness by Rz from 5 to 20% from the initial roughness. The basic feature is that after the plating, Cr plating is performed.

[Action]

As described above, in the Cr plating roll manufacturing method for rolling, the present invention aims at smoothing only the roll roughness peak and reduces the roll initial wear rate, whereby the rolling strip portion and non-passing strip portion are rolled. It reduces the occurrence of roughness difference.

〔Example〕

 Specific examples of the present invention will be described below.

● Example 1. First, the present inventors have found that the reduction ratio of the surface roughness due to etching is Rz in the case of using the Cr-Metroll produced by the usual method.
The following experiment was carried out using Cr-metakilol produced so as to have a concentration of 15%. For both rolls, a forged steel roll having a diameter of 530 mm and a roll roughness Rz before plating of 12 μm is used. Among them, the Cr plating by the normal method is directly Cr-plated (plating thickness 8 μm). In contrast,
The other roll consists of chromic anhydride and sulfuric acid in the etching process before plating, as shown in FIG.
Inside the electrolytic cell (10) filled with Cr plating solution, suspend the hook (1
The roll (12) suspended by 1) was immersed as an anode, and the electrode plate (13) was placed around it as a cathode to perform electrolytic treatment. At that time, the chromic acid anhydride and the sulfuric acid in the used beetle solution were 250 g / 10 g / 10 g / liquid temperature and 48 ° C., respectively. Further, as the electrolytic treatment condition, the integrated current amount (current density × time) was set to about (270 A / dm ² ) · min. After the etching treatment, Cr plating (plating thickness 8 μm) was performed. For reference, roll surface roughness
When Rz is set to 16 μm, in order to reduce this by 5 to 20%, 50 to 500 g / preferably 200 to 300 g / chromic anhydride and 0.5 to 10% of the amount of chromic anhydride, preferably 1 to 8
% Sulfuric acid, and the electrolytic treatment may be performed in a Cr plating solution at a temperature of 35 to 60 ° C. so that the cumulative current amount is about (40 to 500 A / dm ² ) min. And using these rolls, the elongation rate is 0.
Approximately 10 parts of wide annealed mild steel with wet pressure adjustment of 5 to 1.5%
It was rolled 0 km. With regard to the roll subjected to the above-mentioned etching treatment, rolling of about 50 Km was continued for the same width material.

FIGS. 6 (a) and 6 (b) show changes in the roll surface roughness near the plate edge of each roll after the above rolling. The roll surface roughness pattern of the Cr mesh roll manufactured by the normal method shown in FIG. 3A is such that the roughness Rz on the roll end side is 9 μm and the roughness on the roll center side is centered on the edge mark E attached by the contact of the plate edge. Rz was 7.5 μm.
On the other hand, the roughness pattern of the Cr metallurgical roll that has been subjected to the treatment to reduce the surface roughness by 15% shown in Fig. 6 (b) shows that the roll end side and the roll center side are in spite of the long pressure adjusting distance. The roughness Rz of both of them was 7 μm.

As described above, in the Cr plating roll manufactured by the method of the present invention, the difference in roll roughness between the threaded portion and the non-threaded portion is reduced.

Example 2 Further, the present inventors used a plurality of forged steel rolls having a diameter of 530 mm and a pre-etching roll roughness Rz of 17 μm, and some of them were subjected to the Cr plating treatment (mesh thickness 8 μm) as they were. Cr metallurgy produced by the above method, and the other ones have high current density and long time electrolytic treatment in the etching process before plating, and have surface roughness of 3%, 5%, 10%, respectively.
Wet pressure control was performed at an elongation rate of 0.5 to 1.5% by using a Cr plating roller which was reduced by 15%, 20%, 25% and 30%, and was then subjected to Cr plating treatment (mesh thickness 8 μm). . At that time, annealed mild steel was used as the material to be rolled, and the pressure regulating distance was 20
It was set to 0 km.

FIG. 7 is a graph showing the roughness of each roll surface (roll center portion) after the pressure adjustment and the edge mark generation state of the material to be rolled. According to the figure, a visible edge mark is generated on the rolled material that is pressure-controlled by the Cr plating roller manufactured by the normal method and the Cr plating roller whose surface roughness is reduced by 3%. On the other hand, the surface roughness is 5%, 1
With Cr plated rolls with 0%, 15% and 20% reduction, although the surface roughness after rolling is almost unchanged from that of the above rolls, edge marks are generated in the rolled material by these rolls. There is no. Also, the surface roughness is 25
% And 30% lower Cr plated rolls, the rolled material rolled by this does not generate edge marks as well, but the surface roughness of the roll is reduced, if used as it is It can be seen that the life of the roll comes earlier than that of the above roll.

〔The invention's effect〕

As described above, according to the method for producing a Cr plated roll for rolling of the present invention for smoothing the peak of the surface roughness, the initial wear rate of the roll produced by the method is reduced, and the strip is rolled. The difference in roll roughness between the strip portion and the non-passing plate portion is reduced, which has the excellent effect of facilitating the execution of schedule-free rolling. Therefore, by carrying out the schedule-free rolling, there are various advantages such as not only the relaxation of the rolling process regulation but also the improvement of the rolling mill operating rate and the reduction of the roll processing cost due to the reduction of the number of roll combinations.

[Brief description of drawings]

FIG. 1 is an enlarged surface view showing a roll surface roughness pattern of Cr metallurgical roll manufactured by the method of the present invention, and FIG. 2 is a surface enlarged view showing a roll surface roughness pattern of Cr metallurgical roll manufactured by a conventional method. FIG. 3 is a partially enlarged view showing the layer structure near the surface of the metal material, FIG. 4 is a graph showing the relationship between the pressure adjusting distance and the roll surface roughness in the experiment carried out when the invention was devised, and FIG. 6 (a) and 6 (b) are explanatory views showing the state of the electrolytic treatment performed during the etching step, and FIG. 6 (a) and FIG. 6 (b) are the vicinity of the plate edge after the pressure regulation of the Cr metallurgy produced by the method of the present invention and the Cr metallurgy produced by the ordinary method. Surface enlarged view showing a roll surface roughness pattern of, Figure 7 is a roll surface roughness after pressure adjustment of the Cr plating work roll manufactured by the method of the present invention and the Cr plating work roll manufactured by another method, Cover Is a graph showing the Etsujimaku occurrence of rolled material. In the figure, (1) is a material, (2) is a diffusion layer, (3) is a processed layer, (4) is an oxide layer, (5) is a rust / smut layer, and (6) is a dirt layer, (10) is an electrolytic cell, (11) is a suspender, (12) is a roll, and (13) is an electrode plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigemitsu Yamada 1-24 Kaminita, Toyonaka City, Osaka Prefecture (72) Inventor Takatoshi Nakano 4012 Itozakicho, Mihara City, Hiroshima Prefecture

Claims (1)

[Claims] 1. A method for producing a Cr-plated roll for rolling, which comprises degreasing, washing with water and etching before plating, wherein a Cr plating solution consisting of chromic anhydride and sulfuric acid is used in the etching step, and the roll surface is roughened using the roll as an anode. After performing electrolytic treatment to reduce the degree of Rz by 5 to 20% from the initial roughness,
A method for producing a Cr-plated roll for rolling, which comprises Cr-plating.