JPH10195598A - Rolling roll material and roll for hot rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the yield of productivity and the surface quality of a rolled product by suppressing the generation of seizure in a rolling roll. SOLUTION: This rolling roll material is the one having a compsn. contg., by weight, 1.5 to 2.0% C, 0.5 to 2.0% Si, 0.5 to 2.0% Mn, 4.0 to 6.0% Cr, 1.5 to 6.0% Mo, 2.0 to 5.0% W, 2.0 to 5.0% V, 1.0 to 10.0% Co, <=0.05% P, <=0.05% S, and the balance Fe with inevitable impurities. The roll for hot-rolling is the one in which the rolling material having this compsn. is cast under melting, is thereafter subjected to grinding and is produced into a roll shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll material to be used as a roll material for rolling a steel material, and to a hot rolling roll formed from the material.

[0002]

2. Description of the Related Art In recent years, in the field of rolling of steel products, for example, in a hot continuous rolling process of steel sheets, a high-speed (high-speed steel) material is used for a work roll for the purpose of high speed, large rolling reduction and improvement of a unit roll. Are starting to use.

A roll made of this high-speed material has abrasion resistance several times as long as that of a conventional roll due to precipitation of carbide having extremely high hardness. However, in the case of rolling of a material that is easily seized during rolling, for example, stainless steel, seizure flaws are apt to occur, so that the roll must be replaced and the high-speed roll does not fully enjoy its inherent performance. doing.

Conventionally, work roll materials used for thin sheet hot rolling include, for example, a wear-resistant cast iron roll material disclosed in JP-A-2-88745, a hot-rolling roll disclosed in JP-A-2-285047, and the like. Forged rolls for hot rolling are disclosed in Japanese Unexamined Patent Publication No. 3-53041, all of which have been developed from the viewpoint of wear resistance and heat crack resistance.
There is no mention of the burn-in problem. In addition, Japanese Unexamined Patent Application Publication No.
Japanese Unexamined Patent Publication (Kokai) No.-68378 discloses a composite roll material having excellent seizure resistance. However, although it is shown that the friction coefficient is reduced by increasing the amount of P added, the seizure resistance is improved. No mention is made of the mechanism of occurrence and prevention of the problem, and no fundamental problem has been solved.

[0005]

In order to improve the life of the rolling roll, it is necessary to suppress seizure.
No technology has been found concerning the effect of alloying components on the seizure of the roll material, and there is no drastic measure.

The present invention relates to a roll material capable of realizing an improvement in seizure resistance by suppressing the occurrence of seizure in a high-speed steel material or the like, and a hot rolled material using the same. It is intended to provide a roll for use.

[0007]

According to the first aspect of the present invention, C: 1.5-2.0% Si: 0.5-2.0% Mn: 0.5-2.0% by weight. % Cr: 4.0 to 6.0% Mo: 1.5 to 6.0% W: 2.0 to 5.0% V: 2.0 to 5.0% Co: 1.0 to 10.0% % P: 0.05% or less S: 0.05% or less A roll material comprising the balance of Fe and unavoidable impurities. Claim 2 is obtained by melting and casting the roll material according to claim 1. And a roll for hot rolling characterized by being manufactured into a roll by grinding.

[0008] In the present invention, by adjusting the amount of carbides precipitated on the rolling roll, the occurrence of seizure of the rolling roll is prevented, thereby improving the unit consumption and productivity of the roll and improving the surface properties of the rolled product. And so on.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various experiments on conventionally known high-speed steel materials and the like in order to improve wear resistance and seizure resistance. As a result, seizure of the high-speed steel occurs at the base structure in the roll structure, that is, at a place other than the carbide, and the amount of the carbide is Cr, M
It has been found that it depends on the amounts of alloy components such as o, W and V. Based on this finding, the present invention is characterized in that, in addition to Cr, Mo, W, and V, Co is contained as an essential component in an appropriate amount based on this finding, and the amount of carbide is controlled to prevent the occurrence of seizure. And

Hereinafter, the present invention will be described in detail. First, the component composition of the roll material of the present invention will be described. C
Is M ₇ C, which combines with Cr, Mo, W, and V and has high hardness
_3. Form carbides of M ₆ C and MC type to improve the wear resistance of the roll material. For that purpose, it is necessary to contain 1.5% or more. However, if the content exceeds 2.0%, the fracture toughness of the roll material deteriorates.

Si is contained in an amount of 0.5 to 2.0% as a deoxidizing element and as an element for securing the fluidity of the molten metal at the time of casting.

Mn is combined with S and precipitated uniformly in the form of MnS in the grains, and is contained in an amount of 0.5% or more in order to eliminate the harmfulness of S. However, if the content exceeds 2.0%, segregation occurs at the grain boundaries of the roll material and the toughness is reduced. Therefore, the content of Mn is set to 0.5 to 2.0%.

[0013] Cr combines with C to form an M ₇ C ₃ type carbide and improves the wear resistance and seizure resistance of the roll material. This effect appears from 4% or more. However, if added in excess of 6%, the amount of carbide generated becomes excessive and the toughness of the roll material is reduced, so the amount is set to 4 to 6%.

Mo bonds to C and precipitates as a high-hardness M ₆ C-type carbide, thereby improving the wear resistance and seizure resistance of the roll material. In addition, a part of the solid solution is dissolved in the matrix, thereby increasing the high-temperature strength of the roll material. For that purpose, it is necessary to add Mo by 1.5% or more. On the other hand, if added in an amount of 6% or more, the toughness of the roll material decreases, so the amount of addition is set to 1.5 to 6%.

W forms an M ₆ C-type carbide similarly to Mo, and therefore improves the wear resistance and seizure resistance of the roll material. Furthermore, it has the effect of increasing the high-temperature strength of the roll material by forming a solid solution in the matrix similarly to Mo. for that purpose,
W must be added at 2.0% or more. On the other hand, 5.0%
If added, the toughness of the roll material decreases, so the amount of addition is set to 2.0 to 5.0%.

V combines with C to form MC type carbide. The MC type carbide has a higher hardness than the M ₆ C and M ₇ C ₃ type carbides, and is added to improve the wear resistance of the roll material. In addition, there is also an effect of preventing seizure of the roll material due to the generation of the carbide. These effects appear from 2.0% or more, but if added to 5.0% or more, the toughness of the roll material is reduced. Therefore, the added amount is set to 2.0% to 5.0%.

Since Co is a Group VIII element like iron, it easily forms a solid solution in the matrix structure, and also increases the high-temperature strength of the roll material and improves the wear resistance. This effect appears from 1% or more, but the effect is saturated even if added at 10% or more. Therefore, the addition amount is set to 1% to 10%.

Since P and S are harmful elements to the roll material, each of them is limited to 0.05% or less.

The roll material can be formed into a roll by performing a forming process such as grinding after the melt casting, and manufacturing it into a roll. This roll material has the general characteristics as a roll, but is characterized mainly by having the characteristic of suppressing seizure occurring during rolling, and also for cold rolling. Although it can be used, it exerts its properties more sufficiently for hot rolling where seizure at high temperatures becomes a problem.

[0020]

EXAMPLES As Example 1 of the present invention, a hot rolling test was first performed on a comparative roll material having the composition shown in Table 1 (all by weight%) and a roll material according to the present invention, and the amount of wear and seizure-induced slip Rate and fracture toughness values were investigated.

[0021]

[Table 1]

A rolling device 3 for rotating a disk-shaped heating piece 1 and a disk-shaped roll test piece 2 in contact with each other as shown in FIG. 1 and a disk-shaped heating piece 1 and a roll test piece 2 are surrounded. High frequency induction heating coil 4 for heating
And a cooling device 5 for cooling the disk-shaped test piece, and a disk-to-disk type hot rolling tester equipped with a radiation thermometer 6 for measuring the temperature of the disk-shaped roll test piece. The investigative rate was investigated. The hot abrasion test conditions at this time were as follows: the maximum contact pressure between the two disks was about 24 kgf / mm ² , the peripheral speed (rotation speed) of the roll test piece was 700 rpm, and the slip ratio between the two disks (( Speed-roll test piece peripheral speed) / heated test piece peripheral speed × 100
%) Was 4.4%. The temperature of the heated piece corresponding to the rolled material was 950 ° C., and the temperature of the roll material test piece was 60 ° C.
The sample was rotated at 0 ° C. for 5000 revolutions, and the abrasion amount of the roll test piece was measured.

The conditions of the hot seizure test are as follows: the maximum contact pressure between the two disks is about 24 kgf / mm ² , the peripheral speed (rotation speed) of the roll test piece is 50 rpm, and the temperature of the heated piece corresponding to the rolled material Was rotated at 950 ° C. and the temperature of the roll material test piece at 600 ° C. for 50 rotations to increase the slip rate until seizure occurred, and evaluated the slip rate at which seizure occurred. The fracture toughness value was measured by a three-point bending test method specified in ASTM-E399. Table 2 shows the results of evaluation of the roll material by these tests.

[0024]

[Table 2]

From Table 2, it can be seen that the roll materials A to F of the present invention are Cr, Mo, W, V in comparison with the comparative examples (comparative roll materials) 1 to 3.
And a larger amount of C compared to Comparative Examples (comparative roll materials) 4 to 6
Since r, Mo, W, and V have appropriate contents, they have excellent wear resistance, seizure resistance, and toughness. Comparative Examples 1 to
Sample No. 3 has low toughness due to low Cr, Mo, W and V contents, but is inferior in wear resistance and seizure resistance. Comparative Example 4
Nos. 6 to 6 are low in toughness due to high Cr, Mo, W, and V contents, and inferior in wear resistance and seizure resistance. Comparative Example 7 is superior in seizure resistance, but inferior in wear resistance and toughness, because the P and S amounts are larger than those of the inventive roll materials A to F. Comparative Example 8 shows that M was smaller than that of the inventive roll materials A to F.
It contains a large amount of n and has excellent seizure resistance, but is inferior in wear resistance and toughness. Comparative Example 9 is excellent in seizure resistance because it contains a large amount of C, but is inferior in wear resistance and toughness.

Next, as a second embodiment, a pair of upper and lower work rolls WU and WL and a pair of forged steel backup rolls B abutting on the outside of the work rolls as shown in FIG.
The roll of the present invention obtained by grinding the roll material according to claim 1, which is cast into a roll shape in a 1/8 size single stand experimental hot rolling mill 7 of a real machine consisting of U and BL. Rolls WU, WL) and the rolling rolls (work rolls WU, WL) of the comparative example were incorporated into a hot rolling test using stainless steel. The same material as in Example 1 was used for the rolling roll, and the component composition was the same as in Table 1. In addition, rolling conditions refer to the hot rolling conditions of the actual machine,
Assuming that seizure easily occurs, the wear amount of the rolling roll and the occurrence of seizure were investigated.

The amount of wear of the rolling roll (work roll) is:
The rolling depth was evaluated by the wear depth at the center of the body length, and the seizure was evaluated by visual observation of the surface condition. A mark attached over the entire surface in the circumferential direction of the roll was represented by x. Table 3 shows the evaluation results after the rolling experiment. As a result of the evaluation,
When rolling with the rolling roll material of the present invention, compared to when rolling with the rolling roll of the comparative example, the occurrence of seizure is suppressed,
It was confirmed that the amount of wear was small.

[0028]

[Table 3]

[0029]

By using a roll made of the above composition of the present invention and performing hot rolling on the basis of this, it is possible to improve the wear resistance and to suppress seizure, thereby extending the life of the roll. In addition, the basic unit of roll, productivity, and surface properties of a rolled product can be significantly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a tester for evaluating the hot wear resistance and seizure resistance of a roll material of the present invention.

FIG. 2 is a schematic explanatory view showing an arrangement of an experimental hot rolling mill in an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating piece 2 Test piece 3 Rolling device 4 Heating coil 5 Cooling device 6 Radiation thermometer 7 Experimental rolling mill WU, WL Work roll BU, BL Backup roll S Steel plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fuyasu Yamamoto 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Corporation Technology Development Division (72) Inventor Shuichi Hamazuki 20-1 Shintomi, Futtsu City, Chiba Prefecture New Nippon Steel Corporation Technology Development Division

Claims (2)

[Claims] C: 1.5 to 2.0% Si: 0.5 to 2.0% Mn: 0.5 to 2.0% Cr: 4.0 to 6.0% Mo by weight% : 1.5 to 6.0% W: 2.0 to 5.0% V: 2.0 to 5.0% Co: 1.0 to 10.0% P: 0.05% or less S: 0. Rolling roll material characterized by being not more than 05%, the balance being Fe and unavoidable impurities. 2. A hot rolling roll produced by subjecting the roll material according to claim 1 to melt casting, followed by grinding to produce a roll.