JP2586873B2 - Hot rolled ceramics rollers and rolls - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guide roller and a rolling roll used in a hot rolling line for producing a steel bar, a steel pipe, and the like, and more particularly, to a method using a silicon nitride material having predetermined characteristics. The present invention relates to a guide roller and a rolling roll.

[0002]

2. Description of the Related Art Conventionally, guide rollers and rolling rolls (hereinafter referred to as "rollers") used in a hot rolling line for producing steel bars and steel pipes.
Both the guide roller and the rolling roll are abbreviated as “roller”. ) Was mainly made of metal. However, there is a problem that the metal roller is intensely worn, has a short life, and has insufficient heat resistance, so that the metal roller comes into contact with the material to be rolled and is easily burned. Furthermore, the mounting and replacement of the rollers were not easy due to the heavy weight. Therefore, in recent years, development of ceramic rollers utilizing the excellent properties of ceramics such as abrasion resistance, heat resistance and light weight has been actively carried out.

For example, Japanese Patent Application Laid-Open No. Sho 62-104616 discloses that at least a contact surface with a material to be rolled is formed of a dense silicon nitride ceramic having a porosity of 1% or less, and the surface roughness of the contact surface is reduced. A guide roller for rolling, characterized in that the rolling force is 6 _S or less, is disclosed. The roller is designed to limit the roughness of the contact surface with the material to be rolled to prevent the material to be rolled from adhering to the roller. Further, in order to use a silicon nitride material as a structural material of the roller, it is important to improve the strength, and various attempts have been made to improve these characteristics.

[0004]

However, in the above-mentioned conventional ceramic roller, although the improvement in preventing the material to be rolled from adhering to the roller is recognized, the strength of the roller itself (particularly, the strength of the roller itself, particularly However, there is a problem that the roller may be damaged by use for a relatively short time. Even when the roller is made of a material with improved strength, the abrasion resistance cannot be said to be sufficient yet, and the high-temperature abrasion resistance considering the life of the roller has been further improved. There was room for

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a ceramic roller having excellent thermal shock resistance and abrasion resistance and having an extended product life. Is to provide.

[0006]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above problems, and as a result, has found that the above problems can be solved by using a silicon nitride material having a predetermined Vickers hardness, and has completed the present invention. I came to. Therefore, the hot-rolled ceramic roller of the present invention is a ceramic roller used in a hot rolling line,
It is characterized by being constituted by using a silicon nitride material having a Vickers hardness at 9.0C of 9.0 GPa or more.

[0007]

In the present invention, the Vickers hardness of the silicon nitride material used for producing the roller is controlled so as to have a value of 9.0 GPa or more in a temperature range of 800 ° C. or more. This characteristic condition is obtained by the present inventor inspecting the physical properties of various materials by various measuring methods, and comparing and examining the obtained results with the results obtained by testing on actual rolling lines. It is a finding.

The details of the fact that the roller can be improved in thermal shock resistance, abrasion resistance and product life by controlling to the above characteristic conditions are not known at present, but can be inferred as follows. That is, hot rolling, especially 80
Under the conditions of hot rolling at a high temperature of 0 ° C. or higher,
It can be considered that the wear resistance and thermal shock resistance of the roller do not depend only on the friction coefficient (surface roughness) of the roller surface, but rather are governed by the hardness of the roller itself.

It is to be noted that, while maintaining a good product life of the roller, excellent wear resistance and excellent wear resistance under more severe rolling conditions (for example, increasing the temperature of the material to be rolled or increasing the feed speed thereof). In order to maintain the thermal shock resistance, the Vickers hardness is set to 10.0 GP at 1000 ° C.
It is preferable to control to a or more. However, this condition is the same as the above Vickers hardness condition (9.0 GP at 800 ° C.).
a) is not limited at all, and the above-mentioned Vickers hardness conditions are usually sufficient.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. (Examples 1 to 6) A molding raw material obtained by adding and mixing a sintering aid to silicon nitride powder was molded into a cylindrical shape by rubber press molding. The obtained molded body was cut using a lathe, and processed into a near-net shape in consideration of firing shrinkage and a cutting allowance after firing into the final shape of the target roller.
At this time, a groove for guiding the material to be rolled was provided on the outer peripheral portion of the roller.

Next, the obtained cut body was fired in an N ₂ atmosphere, and the obtained sintered body was further cut (finished) to obtain a roller having a final shape and dimensions. Note that the roller having the final shape has an outer diameter of 100 mmφ, an inner diameter of 50 mmφ, a width of 50 mm, and a groove curvature R20.

Then, by changing the kind, amount and sintering temperature of the sintering aid used in the above steps, silicon nitride rollers having different material characteristics (Examples 1 to 6) were obtained. Vickers hardness and JIS R of each roller thus obtained
The four-point bending strength was measured according to 1601, and the obtained results are shown in Table 1. The Vickers hardness is J
It was measured according to IS Z 2244 "Vickers hardness test method". The measurement was carried out at a load of 5 kg and a load holding time of 30 sec after the sample was held at each measurement temperature for 30 minutes to confirm that the sample reached a predetermined temperature. At this time, the measurement was performed in an argon atmosphere to prevent the sample being measured from being oxidized. In addition, using each roller, the rolling conditions such as the temperature of the steel material and the feed rate of the steel material were changed, and an actual machine evaluation test was performed on an actual hot rolling line. .

(Comparative Examples 1 to 6) Measurement of Vickers hardness, 4-point bending strength test and actual machine evaluation test were performed by using a cemented carbide or heat-resistant alloy roller used in a conventional hot rolling apparatus. The results obtained are shown in Tables 1 and 2. here,
Comparative Examples 1 to 4 are rollers made of silicon nitride, and the roller of Comparative Example 3 has a porosity of 1% and a surface roughness of 6 s. Also,
Comparative Example 5 is a roller made of a cemented carbide, and Comparative Example 6 is a roller made of a wear-resistant alloy.

[0014]

[Table 1]

[0015]

[Table 2]

From the results shown in Tables 1 and 2, it can be seen that the rollers of Examples 1 to 6 belonging to the scope of the present invention have excellent performance. That is, when the Vickers hardness at 800 ° C. is low (Comparative Examples 1 to 6), the abrasion of the roller is large,
The dimensions of the material to be rolled gradually increased. In particular, Comparative Example 5
In Nos. And 6, cracks and breaks occurred in the roller, which were transferred to the surface of the material to be rolled (steel), and lost the commercial value of the steel.

When the rolling conditions are severe (when the steel material temperature is high and / or the feed rate is high), the amount of wear may increase as in the fifth embodiment. It can also be seen that it is preferable to increase the Vickers hardness at 1000 ° C. as in Example 6.

The present invention has been described with reference to the embodiments.
The present invention is not limited to these embodiments, and various modifications are possible within the scope of the present invention. For example, the groove provided on the outer peripheral portion of the roller is not always essential. Further, the shape and size of the roller can be appropriately changed according to the rolling device and the like to be used. Furthermore, depending on the rolling conditions, the roller of the present invention can be used not only for hot rolling but also for cold rolling. Furthermore, for example,
In combination with a sleeve member made of a low expansion metal, it is also possible to manufacture a roller using only the outer peripheral portion using the silicon nitride material according to the present invention.

[0019]

As described above, according to the present invention,
Since a silicon nitride material having a predetermined Vickers hardness is used, it is possible to provide a ceramic rolling roll and a guide roller which are excellent in thermal shock resistance and wear resistance and have an extended product life.

Claims (2)

(57) [Claims] 1. A hot-rolled ceramic roller used in a hot-rolling line, comprising a silicon nitride material having a Vickers hardness at 9.0 ° C. of 9.0 GPa or more. 2. Vickers hardness at 1000 ° C. is 1
3. The hot-rolled ceramic roller according to claim 1, wherein the hot-rolled ceramic roller is made of a silicon nitride material of 0.0 GPa or more.