JP6477362B2 - Mill for rolling metal sheets - Google Patents

Description

The present invention relates to a metal sheet rolling mill .

  For cold rolling of a metal plate where surface quality is important, a small-diameter work roll having a diameter of 150 mm or less, which is relatively easy to control the load during rolling, is used. For this work roll material, steel materials such as die steel and high-speed steel whose surface hardness is increased by heat treatment are frequently used.

  Patent Document 1 describes a technique of providing a hard ceramic film layer such as TiN on the surface of a work roll in order to improve wear resistance.

JP-A-4-253511

  When rolling a metal plate repeatedly with a work roll, an adherent may adhere to the roll surface. Such unevenness of the adherend is transferred to the material to be rolled and becomes a surface defect of the material to be rolled, so that the surface quality is deteriorated. Such a problem becomes apparent in applications where high surface properties are required. In addition, since the adherend on the surface of the work roll is also transferred to the intermediate roll or the backup roll, it is necessary to clean or replace these rolls, which may significantly impair the productivity. For this reason, it is necessary to prevent adhesion of the adherend to the roll surface.

  As a result of examining the surface of the work roll used for rolling a pure nickel metal plate in detail, the present inventors have found that most of the adhered products are mainly composed of nickel. That is, it has been found that the cause of the adherend is mainly a component in the material to be rolled. And while there are few these deposits, it does not become a problem in particular, However, The said problem becomes obvious when the adhesion thing becomes large gradually. As a coping method, if the rolling reduction during rolling is reduced, the amount of elements contained in the material to be rolled can be reduced on the roll surface, and the problem of deterioration of the surface properties due to adhesives is less likely to occur. . However, the number of rolling passes increases and production efficiency is inevitably lowered.

  The above mechanism is not limited to the rolling roll of pure nickel metal plate, but is the same for the rolling roll of pure titanium metal plate and titanium alloy plate. The main component of the adherend formed on the work roll is titanium. there were.

  In Patent Document 1, no consideration is given to prevention of adhesion of adherents.

The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a metal sheet rolling mill capable of preventing adhesion of the work roll surface.

  The inventors divided a work roll (forged steel, no surface treatment) used for rolling a pure nickel plate, and analyzed the surface state with a SEM-EDS apparatus. As shown in FIG. 1, this work roll is a 6-stage mill work roll 4 configured with an intermediate roll 2 and a backup roll 3. In the 6-stage mill, the workpiece 1 of a pure nickel plate is rolled by passing between a pair of work rolls 4 and 4 installed at a predetermined interval. As shown in FIG. 2, the work roll 4 includes, for example, a roll part 4a at the center, a small diameter part 4b at both outer sides thereof, and a large diameter part 4c at both ends, and a work (not shown) at the central part of the roll part 4a. There is a sliding portion 4d. As a result of observing the test material obtained by cutting the rolling center portion, the rolling end portion, and the like with respect to the sliding portion 4d, the present inventors have found that a Ni adherend is attached to the roll surface, and the surface layer of the adherend Fe and Cr were also observed. Depending on the position of the roll in the barrel direction, an agglomerated material having a maximum thickness of about 5 μm was observed.

  Therefore, it was found that the adherend adhered to the work roll surface was Ni of the material to be rolled. Moreover, about the observed Fe and Cr, it is estimated that the component derived from the backup roll or the intermediate roll is transferred to the work roll.

That is, there is a possibility that the backup roll or the intermediate roll is worn under the sliding condition, and the wear powder is transferred to the work roll and aggregates and adheres on the work roll surface. The production line is not only cold-rolled with a pure nickel plate but also cold-rolled with a SUS steel plate or the like. At this time, the work roll is changed depending on the type of the material to be rolled, but common parts such as the intermediate roll and the backup roll are not changed. Therefore, before cold rolling of pure nickel plate, when such SUS steel is cast is cold, Fe from SUS steel, elements intermediate rolls, such as Cr, remained the rolling apparatus such as a back-up roll, it It may be transferred to the work roll, aggregated on the work roll surface, and adhered.

  On the other hand, according to the technique described in Patent Document 1, the present inventors formed a TiN layer on the surface of the work roll and rolled the pure nickel metal plate, and the work roll used for rolling was the same as described above. When the surface state was analyzed with a SEM-EDS apparatus, adhesion of nickel to the work roll was confirmed. This is because TiN has high hardness and is excellent in terms of wear resistance, but the friction coefficient is as high as 0.6 to 0.8, and the component derived from the material to be rolled adheres during rolling (sliding). It is thought that. For this reason, in order to maintain the surface properties of the material to be rolled, reduction of rolling load, reduction of rolling speed, etc. are unavoidable, and deterioration of production efficiency is inevitable.

  In addition, Ni of a to-be-rolled material has chemical affinity with the Ti particle | grains which comprise TiN also at room temperature vicinity, It is thought that it is especially easy to adhere.

  Accordingly, the present inventors have studied a surface treatment method that has high hardness, sufficient durability, a low friction coefficient, and that does not cause adhesion of components derived from the material to be rolled. We focused on like carbon (hereinafter referred to as “DLC”). DLC is an amorphous material in which diamond bonds and graphite bonds are mixed. Since DLC has an amorphous structure, it has no crystal grain boundaries and has a very smooth surface compared to a hard film such as TiN. The friction coefficient of DLC depends on the diamond bond / graphite bond ratio, but it is within 0.20 even if it is high, and is much lower than the conventional hard protective film represented by TiN. In particular, nickel and DLC are considered to be a major reason that they are chemically incompatible.

The present invention has been accomplished based on the above findings, and the gist of the metal plate rolling mill below.

(1) A mill used to roll a metal plate containing at least one selected from Ni, Ti and Cr, the mill comprising at least a work roll, an intermediate roll and a backup roll, work rolls, said intermediate rolls and said backup rolls, on its surface, provided with a diamond-like carbon coating layer of amorphous structure diamond bonds and graphite bond are mixed, the mill metal plate rolling.

(2) The metal plate rolling mill according to (1), wherein a friction coefficient of the surface of the diamond like carbon coating layer is 0.2 or less.

(3) The metal plate rolling mill according to (1) or (2), wherein the diamond-like carbon coating layer has a thickness of 1 to 10 μm.

(4) The diamond like carbon coating layer is a crystal ratio of a carbon compound having a diamond type crystal structure and a carbon compound having a graphite type crystal structure, and a ratio of the carbon compound having the diamond type crystal structure is 60 to 80%. there, the (1) to one of the metal plates for rolling mill (3).

According to the present invention, adhesion of the work roll surface can be prevented. Thus, particularly useful as mill metal plate rolling.

The figure which shows the example of an apparatus structure of a 6-stage mill. The figure which shows the example of a work roll. Sectional photograph (scanning electron microscope image) of the work roll of Invention Example 1. The figure which compared the friction coefficient in an Example. The photograph which shows the surface state of the work roll and rolled material in an Example. (a) Surface state of the work roll of Comparative Example 1, (b) Surface state of the work roll of Invention Example 1, and (c) Surface state of the material to be rolled rolled using the work roll of Invention Example 1.

The present invention contains one or more selected Ni, Ti and Cr, the present invention relates to mill used to roll the metal plate. The roll used in the mill of the present invention can prevent such adhesion even when a metal plate containing an element that easily adheres to the roll surface is rolled. Examples of the metal plate containing one or more selected from Ni, Ti and Cr include pure Ni, pure Ti, Ti alloy, and stainless steel. The present invention can be applied to all rolls related to rolling, such as the intermediate roll 2 and the backup roll 3, in addition to the work roll 1 shown in FIG. However, it is preferable to apply to the work roll 1 in direct contact with the material to be rolled (work).

As shown in FIG. 3, the roll 4 used in the mill for rolling a metal plate of the present invention includes a diamond-like carbon coating layer 40 on the surface of the roll portion 4a. That is, the roll part 4 a is composed of the diamond-like carbon coating layer 40 and the base part 41. The diamond-like carbon (DLC) coating layer 40 has an amorphous structure in which diamond bonds (cubic crystals, sp3 bonds) and graphite bonds (hexagonal crystals, sp2 bonds) are mixed. For this reason, DLC has a high hardness similar to that of cemented carbide, and has a low friction coefficient at each stage as compared with a metal oxide film such as alumina, a metal carbide film such as TiC, and a metal nitride film such as TiN. High lubricity.

  The friction coefficient on the surface of the diamond-like carbon coating layer is preferably 0.2 or less in order to prevent adhesion of Ni, Ti, Cr and the like. More preferred is 0.15 or less, and further preferred is 0.1 or less.

  The composition of the DLC coating layer is not particularly limited. Therefore, the ratio of the graphite bond abundance sp2 and the diamond bond abundance sp3 (sp3 / sp2) may be 0.60 to 0.80 in terms of crystal ratio.

  The thickness of the DLC coating layer is preferably 1 μm or more in order to ensure the function as a hard protective film. On the other hand, if the DLC coating layer is too thick, the tensile stress applied to the interface between the DLC coating layer and the base material portion becomes too strong based on the “lever principle”, and the DLC coating layer is removed from the base material portion. May peel off. Such a situation is likely to occur particularly when the shear stress during rolling exceeds a predetermined value, such as in high-load rolling. For this reason, it is preferable that the thickness of a DLC coating layer shall be 10 micrometers or less.

  The high lubricity of DLC can be quantitatively grasped by using a low coefficient of friction as an index. And because of the low coefficient of friction, the graphite that constitutes DLC has a tortoiseshell-like layered structure and exhibits extremely strong bonds (covalent bonds, also referred to as σ bonds) in the same layer, while the interlayer (tortoiseshell) In the upper and lower surfaces, the bond remains weak (Van der Waals force, also called π bond). For this reason, when the latter bonding force is less than the shear stress applied to the DLC surface, a slip phenomenon between layers (slip on the order of several Å) occurs relatively easily, and the bond is dissociated. As a result, high lubricity of the DLC coating film layer can be obtained.

  Then, since shear stress always acts on the work roll surface during rolling, the DLC is worn, and the DLC does not peel off even in a rolling environment, and the film must be formed under the remaining conditions. If the lower limit value of the film forming conditions is a DLC thickness of 1 μm or more, at least the intended production process (rolling total length of the steel sheet) can be processed.

In addition, the thickness of a DLC coating layer can be adjusted with the time which exposes the base-material part of a roll in the film-forming apparatus. Here, for example, when the DLC film is formed on the base material portion using the physical vapor deposition method (PVD method), the film forming temperature may exceed the tempering temperature of the steel material constituting the base material portion. Even if the film formation temperature exceeds the tempering temperature, there is no particular problem if the film formation time is short. However, if the film formation time is too long, the steel material constituting the base material part of the roll will be inside the film formation apparatus. There is a risk of unexpected softening as a result of tempering. In this respect, if the thickness of the DLC coating layer is 10 μm or less, the film can be formed in a relatively short time, so even if the film forming temperature is high, the influence on the base material of the roll should be made small enough to be ignored Can do. In addition, since the DLC coating layer has a low heat-resistant temperature, the roll used in the mill of the present invention is not suitable for hot rolling but is suitable for warm rolling or cold rolling.

  The DLC coating layer is formed directly or via a buffer film on the surface of the base of the roll using a dry film forming method such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). Can do. With the recent development of film forming apparatus technology, in addition to an ultra-high hardness film with a controlled hydrogen content, a hard film in which chromium, silicon, etc. are incorporated into a matrix as hard particles has been put into practical use. The processing conditions of the PVD method or the CVD method may be in accordance with well-known and conventional conditions as long as the steel material structure after the heat treatment of the steel material constituting the base portion of the roll and the steel material structure are not impaired. It is not limited. For example, an arc ion plating method is preferable for PVD, and a plasma CVD method is preferable for CVD in order to form a DLC film uniformly and uniformly on the entire surface of the roll circumference.

  Here, the chemical composition of the base material portion is not particularly limited as long as it has a predetermined mechanical performance (surface hardness: 800 or more in Hv, surface roughness: about 0.06 in Ra), For example, in the JIS standard, SKD series, SKH series, and the like are listed as the steel material classification.

  In order to confirm the effect of the present invention, a forged steel work roll (Comparative Example 1), a super steel work roll (Comparative Example 2), and a work roll provided with a DLC coating layer on the surface of a forged steel base material (the present invention) Example 1) was prepared, and pure nickel foil (plate thickness 0.2 mm, plate width 600 mm, nickel purity ≧ 99.5%) was rolled up to a plate thickness of 0.1 mm in a 6-stage mill shown in FIG. Rolling (number of passes: 1 pass, rolling load: 70 to 80 ton total rolling length: 10,000 m) was performed, and the surface properties of the material to be rolled were confirmed. In addition, the shape of the work roll was the shape shown in FIG. 2, the body length of the roll part was 1,000 mm, and the diameter of the roll part was 80 mm.

  The work roll of Example 1 of the present invention has a DLC coating layer having a composition of ta-C: H type (hydrogenated tetrahedral amorphous carbon), in which the surface of the work roll made of forged steel is inserted into a plasma CVD film forming apparatus. A film was formed. The DLC coating layer had a thickness of 1.3 μm and a friction coefficient of 0.140. The ratio (sp3 / sp2) was 75%. As shown in FIG. 3, a uniform DLC coating layer was formed on the surface of the work roll of Example 1 of the present invention.

  As shown in FIG. 4, the friction coefficient calculated from the load value and the friction force during rolling is 0.14 for the forged steel work roll of Comparative Example 1 and 0.16 for the cemented carbide work roll of Comparative Example 2. In contrast, the DLC-coated forged steel work roll of Example 1 of the present invention had an extremely low value of 0.07.

  As shown in FIG. 5, adhesion is noticeable in the forged steel work roll of Comparative Example 1 (see FIG. 5 (a)), but adhesion is not confirmed in the DLC-coated forged steel work roll of Invention Example 1 (FIG. 5). (Refer to (b)), and no surface defect occurred in the rolled pure nickel foil (see FIG. 5 (c)).

According to the present invention, adhesion of the work roll surface can be prevented. Thus, particularly useful as mill metal plate rolling.

1 Work 2 Intermediate roll 3 Backup roll 4 Work roll 4a Roll part 4b Small diameter part 4c Large diameter part 4d Sliding part 40 Diamond-like carbon coating layer 41 Base material part

Claims (4)

A mill used to roll a metal plate, containing one or more selected from Ni, Ti and Cr,
The mill includes at least a work roll, an intermediate roll, and a backup roll,
The work roll, the intermediate roll, and the backup roll include a diamond-like carbon coating layer having an amorphous structure in which diamond bonds and graphite bonds are mixed on the surface thereof.
Mill for rolling metal sheets. The friction coefficient of the diamond-like carbon coating layer surface is 0.2 or less,
The metal sheet rolling mill according to claim 1. The diamond-like carbon coating layer has a thickness of 1 to 10 μm.
The metal plate rolling mill according to claim 1 or 2. The diamond-like carbon coating layer has a crystal ratio of a carbon compound having a diamond-type crystal structure and a carbon compound having a graphite-type crystal structure, and a ratio of the carbon compound having the diamond-type crystal structure is 60 to 80%. any metal plate rolling mill from claim 1 to 3.