JP2601746B2 - Centrifugal casting sleeve roll and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sleeve roll made of centrifugal casting which has both abrasion resistance, crack resistance and toughness and is suitable for use as a roll for rolling and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, for example, a roll of a universal mill for an H-section steel is made of a high-hardness material such as a special adamite steel, an alloy ductile cast iron or a nickel grain cast iron as an outer layer material, and has an excellent toughness as an inner layer material. Composite sleeves using spheroidal graphite steel or ductile cast iron are frequently used.

[0003] The composite sleeve is generally cast by a known centrifugal casting, subjected to a predetermined heat treatment and machining, set by shrink-fitting on a shaft, and is generally made into a pair of assembly rolls.

[0004] In recent years, in view of severer rolling conditions and a demand for improved productivity in rolling, it has been demanded to provide a roll for rolling having more wear resistance, crack resistance and toughness.

[0005]

However, the outer layer material of the composite sleeve is limited in terms of wear resistance, especially for long-term continuous use such as the required level on the rolling side and chance-free. The reality is that the role is a bottleneck for the future concept of. Therefore, there is a demand for the development of an outer layer material which is much more excellent in performance than the current material which can meet such demands.

[0006] Also, with regard to the inner layer material, various restrictions such as insufficient strength and difficulty in rolling a thin-walled size for high-load rolling such as width-variable roll rolling in H-section steel rolling are difficult. Have to be forced.

Under such circumstances, for example, Japanese Patent Application Laid-Open No. 60-124
No. 407 and JP-A-61-177355 propose the use of high-V cast iron as the outer layer material of a conventional centrifugal casting roll. However, in a rolling roll using high-V cast iron as an outer layer material of a centrifugal casting roll, V carbide having a low specific gravity is centrifuged, and characteristics in the outer layer of the roll become uneven in the thickness direction. This tendency is remarkable as the thickness of the outer layer of a large roll increases, and there is a problem that the roll cannot be used as a practical roll.

[0008] JP-A-58-87249 and JP-A-1-96355 propose a rolled material using cast steel or cast iron which is made of a high alloy like high speed steel. However, JP 58
-87249 is intended for small diameter castings that do not rely on centrifugal casting, and is not a problem. Also, JP-A-1-96355 discloses that
Only special manufacturing methods other than the special casting overlay method and the centrifugal force casting method can be applied, and there is a problem in terms of productivity and economy.

[0009] That is, in the production of a rolling roll, it is possible to significantly improve wear resistance by incorporating a large amount of V in the outer layer of the roll, but the most excellent productivity and economical efficiency during the production of a composite roll. However, when a generally used centrifugal casting method is employed, there is a problem that carbides are centrifuged and predetermined characteristics cannot be obtained uniformly.

The present invention uses an outer layer material having uniform wear resistance and crack resistance which does not cause segregation even under the action of centrifugal force by optimizing the alloy components forming the outer layer and limiting the carbide composition. It is another object of the present invention to provide a centrifugally cast sleeve roll in which a highly tough graphite steel is used for an inner layer material, and an outer layer and an inner layer are completely metallurgically bonded to be integrated.

[0011]

According to a first aspect of the present invention, there is provided a sleeve roll made of centrifugal casting comprising an outer layer material and an inner layer material of graphite steel welded and integrated with the outer layer material. Material: C: 1.0-3.5%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 3.0 to 12.0% , Mo: 2.0 to 8.0% ,
V: 3.0 to 10.0%, Nb: 0.6 to 7.0%, and the balance consists of Fe and unavoidable impurities.
The following formulas (1) and (2) are satisfied: V + 1.8Nb ≦ 7.5C−6.0% (1) 0.2 ≦ Nb / V ≦ 0.8.・ (2) The inner layer material is: C: 1.0 to 2.0%, Si: 1.6 to 2.4%, M
n: 0.2 to 1.0%, P: 0.05% or less, S: 0.03% or less, Ni: 0.
7% or less, Cr: 3.5% or less, Mo: 0.03 to 3.0% , the balance being Fe and unavoidable impurities , and the mixing ratio of the outer layer to the inner layer is restricted to the range of 5 to 35%. It is something that has been done.

According to a second aspect of the present invention, there is provided a centrifugal casting sleeve roll comprising an outer layer material and an inner layer material of graphite steel welded and integrated with the outer layer material, wherein the outer layer material is C: 1. 0.0 to 3.5%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 3.0 to 12.0% , Mo: 2.0 to 8.0% ,
V: 3.0 to 10.0%, Nb: 0.6 to 7.0%, further contains at least one selected from Ni: 8.0% or less, Co: 10.0% or less, The balance consists of Fe and unavoidable impurities and satisfies the following equations (1) and (2)
And, V + 1.8Nb ≦ 7.5C-6.0 % ··· (1) 0.2 ≦ Nb / V ≦ 0.8 ··· (2) the inner layer material, C: 1.0 to 2. 0%, S1: 1.6 to 2.4%, M
n: 0.2 to 1.0%, P: 0.05% or less, S: 0.03% or less, N1: 0.
7% or less, Cr: 3.5% or less, Mo: 0.03 to 3.0% , the balance being Fe and unavoidable impurities , and the mixing ratio of the outer layer to the inner layer is restricted to the range of 5 to 35%. It is something that has been done.

According to a third aspect of the present invention, there is provided a sleeve roll made of centrifugal casting comprising an outer layer material and an inner layer material of graphite steel welded and integrated with the outer layer material, wherein the outer layer material comprises: C: 1 0.0 to 3.5%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 3.0 to 12.0% , Mo: 2.0 to 8.0% ,
V: 3.0 to 10.0%, Nb: 0.6 to 7.0%, Ni: 8.0% or less, Co: 10.0% or less, Cu:
2.0% or less, Ti: 2.0% or less, Zr: 2.0% or less , B: One or more selected from 0.1% or less, with the balance Fe and unavoidable Tomo and consisting of impurities
The following formulas (1) and (2) are satisfied: V + 1.8Nb ≦ 7.5C−6.0% (1) 0.2 ≦ Nb / V ≦ 0.8 (2) ) The inner layer material is: C: 1.0 to 2.0%, Si: 1.6 to 2.4%, M
n: 0.2 to 1.0%, P: 0.05% or less, S: 0.03% or less, Ni: 0.
7% or less, Cr: 3.5% or less, Mo: 0.03 to 3.0% , the balance being Fe and unavoidable impurities , and the mixing ratio of the outer layer to the inner layer is restricted to the range of 5 to 35%. It is something that has been done.

[0014]

[0015]

[0016]

[Action]

(A) Reasons for limiting alloy elements in outer layer material C: 1.0 to 3.5% C is an essential element for forming hard carbide which improves the wear resistance of the outer layer material of the roll, and is required to be 1.0% or more.
%, Crack resistance is significantly reduced.
3.5%.

Si: 2.0% or less Si is added as a deoxidizing agent and an element necessary for ensuring castability, but if it exceeds 2.0%, crack resistance is reduced, so the upper limit is made 2.0%.

Mn: 2.0% or less Mn is required in the same manner as the above Si, but if it exceeds 2.0%, the crack resistance is reduced, so that it is not preferable that the upper limit is 2.0%.
And

Cr: 3.0 to 12.0% Cr forms a carbide and is essential for improving wear resistance.
The element is required to be 3.0% or more, but if it exceeds 12.0%, the wear resistance deteriorates when V and Nb, which is the object of the present invention, is added, so the upper limit is made 12.0%.

Mo: 2.0-8.0% Mo forms carbides like Cr and improves wear resistance .
2.0% or more is an essential element for improving the hardenability and temper softening resistance of the matrix, and is effective for strengthening the matrix structure. , The upper limit is set to 8.0%.

Ni: 8.0% or less, Co: 10.0% or less Ni is added to improve hardenability and strengthen the base structure. However, if it exceeds 8.0%, an unstable structure such as the presence of residual γ is formed. Therefore, it is not preferable, and the upper limit is set to 8.0%.

Co is added to stabilize the structure at a high temperature, but if it exceeds 10.0%, the effect of improving heat resistance is saturated, so the upper limit is made 10.0% from the viewpoint of economy.

Cu: 2.0% or less Cu is added to strengthen the base structure and improve the high-temperature hardness. However, if Cu exceeds 2.0%, the surface properties of the roll are deteriorated and the wear resistance and The upper limit is set to 2.0% to reduce crack resistance .

Ti: 2.0% or less, Zr: 2.0% or less, B: 0.1% or less Both Ti, Zr and B are added to suppress the formation of coarse eutectic carbides and to improve wear resistance and crack resistance. However, if the content of Ti and Zr exceeds 2.0%, the shape of the V, Nb composite carbide deteriorates, and conversely, the wear resistance decreases.
If B exceeds 0.1%, B segregates at the grain boundary and lowers crack resistance, so the upper limit is made 0.1%.

V: 3.0-10.0%, Nb: 0.6-7.0% V, Nb is the most important essential element in the present invention,
These complex additions and content limiting conditions are the most important features of the present invention.

V is a hard MC which is most effective for improving abrasion resistance.
Or an essential element for forming M ₄ C ₃ carbide, and it is necessary to have 3.0% or more to exhibit its effect.
%, Crack resistance deteriorates and production problems occur, so the upper limit is made 10.0%.

Nb is a hard MC which is effective for abrasion resistance like V.
Formed carbides are formed, but if they are added alone, they become coarse bulky carbides, and not only the effect cannot be obtained, but also crack resistance becomes a problem.

In the outer layer material of the present invention, the above-mentioned N
It is not always necessary to contain i, Co, Cu, Ti, Zr, W, and B.

Further, in the outer layer material of the present invention, V and Nb
Relationship with the amount of C on the base metal hardness when compounding is added,
And the relationship between the maximum wear depth in the thermal shock test and the Nb / V content ratio Nb / V in the outer layer and the inner layer due to the carbide distribution in the ring material cast by centrifugal force. 1 to 4 and FIGS. 5 to 8 respectively.

From FIG. 1 to FIG. 4, in order to obtain the required hardness Hs of 75 or more as a roll for wear-resistant hot rolling, V + 1.8 N
It became clear that it was necessary to satisfy b ≦ 7.5 C-6.0 (%).

The experiment shown in FIG. 1 shows that Si: 0.5%, Mn:
0.5%, Cr: 6.8%, Mo: 3.2%, C,
A 25 mm Y / block cast from a molten metal with varied V and Nb was subjected to a 1000 ° C. normalizing process and a 550 ° C. tempering sample. The experiment of FIG. 2 was performed with 0.5% Si and 0.5% Mn.
25mmY cast from 5%, Ni: 2.7%, Cr: 7.2%, Mo: 3.5%, and molten C, V, Nb
Using a sample subjected to a 1000 ° C. normalizing treatment and a 550 ° C. tempering treatment for the block, the experiment in FIG.
%, Mn: 0.4%, Ni: 1.5%, Cr: 5.7%, M
O: 2.8%, Co: 3.2%, 1050 for a 25 mm Y-block cast from a molten metal with varied C, V, Nb.
The samples in FIG. 4 were subjected to a normalizing process at 550 ° C. and a tempering process at 550 ° C.
r: 6.0%, Mo: 3.2%, Co: 4.1%,
Samples obtained by quenching at 1050 ° C. and tempering at 550 ° C. for a 25 mm Y-block cast from a molten metal having varied C, V, and Nb were used.

5 to 8 that a uniform outer layer material can be obtained even when manufactured by the centrifugal casting method, and that 0.2 ≦ Nb / V ≦ 0.8 is satisfied in order not to impair the crack resistance. It became clear that we needed to do that.

In FIGS. 5 to 8, "wear ratio (inner layer / outer layer)" means a wear amount (Iw) of a test piece taken from the inner layer side of the ring material and a wear amount of a test piece taken from the outer layer side. (Iw / Ow) with respect to (Ow), and the “thermal shock crack maximum depth” is the maximum crack depth generated in the thermal shock test.

The experiment of FIG. 5 shows that C: 2.5%, Si:
0.5%, Mn: 0.5%, Cr: 6.5%, Mo: 3.5%,
A 100-mm thick ring sample obtained by centrifugal casting (140 G) a molten metal containing V: 5.4% and Nb: 0-8.0%, and subjected to 1000 ° C. normalizing treatment and 550 ° C. tempering treatment. The experiment shown in FIG. 6 was performed using C: 2.7% and Si: 0.6%.
%, Mn: 0.5%, Ni: 3.2%, Cr: 7.4%, M
o: A ring sample with a thickness of 100 mm obtained by centrifugal casting (140 G) a molten metal containing 3.7%, V: 5.8%, and Nb: 0 to 7.5% was subjected to 1000 ° C normalizing treatment and 550 ° C tempering. Using the treated sample, the experiment of FIG.
%, Si: 0.4%, Mn: 0.5%, Ni: 0.5%, C
r: 5.5%, Mo: 3.2%, V: 5.4%, Co: 5.2
%, Nb: 0 to 7.2%.
0 G) For a ring sample with a thickness of 100 mm obtained by
Using the samples which were subjected to 50 ° C. normalizing treatment and 550 ° C. tempering treatment, the experiment of FIG. 8 shows that C: 2.2%, Si: 0.3%, M
n: 0.4%, Cr: 6.0%, Mo: 3.2%, V: 5.1
%, Co: 4.1%, Nb: 0 to 6.0%, a 100 mm thick ring sample obtained by centrifugal casting (140 G) of a molten metal, which was quenched at 1050 ° C. and tempered at 550 ° C. Was used.

In the abrasion test, the mating material was heated to 800 ° C. by a sliding disk method of a 190 mm x 15 mating material and a 50 mm x 10 mating material and pressed against the sample at 800 rpm with a load of 100 kgf. At a slip rate of 3.9%, and the wear loss after 120 minutes was measured.

The thermal shock test was conducted by pressing a 55 × 40 × 15 plate test piece against a roller rotating at 1200 rpm under a load of 150 kgf and a contact time of 15 s. The crack length was measured.

Further, as the heat treatment conditions for the outer layer material of the present invention, after austenitizing at 1000 to 1150 ° C., controlled cooling is performed so that the structure after cooling becomes bainite. Therefore, the cooling conditions differ depending on the composition, shape, and size of the target roll material. 1 to 4 and 5 to 5 described above.
In the experiment of FIG. 8, since the size of the material to be heat-treated is small, both normalizing (air cooling after austenitizing) and quenching (quenching after austenitizing) are possible.
In addition, tempering is performed by selecting the optimal conditions in the range of 500 to 600 ° C.

(B) Reasons for Restriction of Alloy Elements in Inner Layer Material In the composite roll, it is essential to mix the inner layer side of the outer layer and the inner layer in order to metallurgically bond the outer layer and the inner layer. However, the outer layer should not be mixed excessively until the excellent toughness function of the inner layer is impaired. For this reason, it is extremely necessary to select the casting conditions and keep the mixing ratio of the outer layer in the inner layer portion (the weight% of the outer layer material mixed in the inner layer material with respect to the weight of the entire inner layer material melt) in an appropriate range. is important. In the present invention, it has been found that it is optimal to regulate this range to 5 to 35%. That is, if it is 5% or less, the dense segregation layer of C and Si formed on the innermost surface of the outer layer by centrifugal force separation remains without being completely washed, so that the soundness of the boundary layer cannot be secured. On the other hand, if it exceeds 35%, a large amount of Cr and C, which particularly deteriorate the properties of the inner graphite steel, is mixed in the outer layer components, and the inner layer structure after solidification becomes a high C-Cr system,
This leads to poor graphite shape of the inner layer and significant whitening of iron, resulting in reduced functions.

Therefore, it is necessary to regulate the mixing ratio of the outer layer within the range of 5 to 35%, and to select the chemical composition of the molten metal so that the composition of the inner layer after solidification satisfies the following range in consideration of the resulting increase in components. There is.

C: 1.0 to 2.0% In the case of graphite steel, C has the effect of dissolving in the matrix to secure the strength, and has the effect of suppressing the occurrence of shrinkage cavities and gas defects while being partially graphite. 1.0% C content
If the content is less than 2.0%, the effect is insufficient. On the other hand, if the content is more than 2.0%, since C is also a carbide-forming element, the amount of carbide increases and the toughness deteriorates. Therefore, C is defined as 1.0 to 2.0%.

Si: 1.6 to 2.4% Si has the effect of crystallizing graphite, but 1.6% to 2.4%.
If it is less than 2.4%, the effect cannot be expected. If it exceeds 2.4%, the Si dissolved in the ferrite deteriorates the material strength.

Mn: 0.2% to 1.0% Mn has the effect of improving the material strength, but considering that segregation to the grain boundary when the content is too large deteriorates the toughness,
The range is 0.2% to 1.0%.

P: 0.05% or less P increases the fluidity of the molten metal, but the lower the better, to make the material brittle, the more preferable it is 0.05% or less.

S: 0.03% or less S, like P, makes the material brittle, so the lower the content, the better, the content being 0.03% or less.

Ni: 0.7% or less Ni is effective in securing strength and toughness, but if it exceeds 0.7%, the cost increases, so a necessary and sufficient 0.7% is required.
It was as follows.

Cr: 3.5% or less It is desirable that Cr is low in order to degrade the toughness, but Cr cannot be completely prevented from being mixed in the outer layer. Therefore, the Cr content in the molten metal before casting should be less than 1.0%. 3.5% in total with Cr% that has been redissolved and diffused in
It is as follows.

[0047] Mo: 0.03~3.0% Mo is there an important element in terms of similarly toughness security and Ni
If less than 0.03%, the effect is insufficient and 0.03%
%, But if it exceeds 3.0%, no effect is obtained for the added amount. Therefore, the content is set to 3.0% or less in consideration of economy.

Also, Al, Ti, Zr, etc. are used as deoxidizing agents.
0.1% or less can be used.

When the inner layer composition after solidification satisfies the above range, the function of the graphite steel used as the inner layer material can be obtained. In the present invention, however, the inclusion of V and Nb mixed from the outer layer causes Compared to general graphite steel,
There is an advantage that the mechanical properties are further improved.

This is because the formation of carbides is suppressed by keeping the inner layer structure after solidification within the above range.
V, which has a crystal grain refining action and is an element for improving hardenability
This is because a fine bainite matrix structure with a very small amount of carbides can be obtained by high-temperature heat treatment due to appropriate amounts of Nb and Nb.

By this effect, it is possible to use it for higher load rolling than before, and it is possible to make the thickness of the inner layer thinner. This advantage is extremely advantageous, for example, when rolling a product having a large flange leg length in H-section steel rolling. The roll used for rolling the product requires a large outer layer thickness, so the inner layer thickness becomes thinner, which involves a risk of breakage. Therefore, in the conventional practical roll, a steel-based, for example, adamite-made integral roll has been generally used instead of the composite type. For this reason, early roll replacement has been forced due to the occurrence of roll wear and seizure.

In the case of the roll according to the present invention, since the inner layer strength is significantly higher than that of the conventional roll, the function as a composite roll can be provided for the rolling of the product.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A centrifugally cast sleeve roll according to the present invention comprises:
It has the configuration described in detail above, and a method of manufacturing this roll will be described with reference to an example shown in FIG.

First, after the molten metal for forming the outer layer 1 is cast in a metal mold 10 which is rotated on a centrifugal force casting machine and has a refractory coated on the inner surface, the inner surface of the outer layer 1 is left uncoated. The inner layer 2 is cast during solidification and the outer layer 1 and the inner layer 2 are completely metallurgically joined to form an integral sleeve-type roll. After the casting of the inner layer 2, the rotation is continued, and the process is stopped after the outer layer 1 and the inner layer 2 are completely solidified.

FIG. 10 shows a centrifugally cast sleeve roll according to the present invention, in which the hollow portion of the inner layer 2 is set in the arbor 3 by shrink fitting and used.

(Experimental Example 1) (See Tables 1 to 3) Rolls having a product body diameter of 880 mm, an inner diameter of 524 mm, and a width of 420 mm were manufactured.

(1) As an outer layer, a molten metal having a thickness of 100 mm was cast at a casting temperature of 1500 ° C. into a mold rotating on a centrifugal casting machine.

(2) 22 minutes after the start of the casting of the outer layer, a 115 mm thick wall was cast at 1470 ° C. as an inner layer molten metal in a rotary mold.

(3) After 60 minutes from the start of casting the outer layer, the outer layer and the inner layer are completely solidified. (4) Then, stand the mold vertically and slowly cool it to room temperature.

(5) After cooling completely, the roll was taken out of the mold, and after heat treatment and machining, it was shrink-fitted to the arbor to obtain a roll of the final product.

As a result of ultrasonic inspection and cutting inspection of the roll body, the thickness of the outer layer was 70 mm due to the casting of the inner layer, the thickness of the inner layer was 135 mm, and the Cr content was 1.2 to 1.8.
%Met. Then, the outer layer and the inner layer were completely bonded to each other, and organizational continuity was recognized.

Table 1 shows the chemical compositions of the outer layer and the inner layer at the molten metal stage.

[0063]

[Table 1]

The chemical composition after solidification of the outer and inner layers of the roll cast with the composition shown in Table 1 is as shown in Table 2.

[0065]

[Table 2]

Table 3 shows the mechanical properties of the inner layer of the roll of the present invention in comparison with those of the conventional roll of the same size.

[0067]

[Table 3]

In the rolls of the present invention having the compositions shown in Tables 1 and 2, the alloy components forming the outer layer were optimized and the carbide composition was limited, so that segregation did not occur even under the action of centrifugal force. Using an outer layer material with uniform crack resistance and crack resistance, and using a tough graphite steel for the inner layer material, the outer layer and the inner layer are completely metallurgically bonded to form a centrifugally cast sleeve roll. be able to.

(Experimental Example 2) (See Tables 4 to 6) Rolls having a product body diameter of φ1060 mm, an inner diameter of 550 mm, and a width of 460 mm were manufactured.

(1) A molten metal having a thickness of 210 mm as an outer layer was cast at a casting temperature of 1505 ° C. into a mold rotating on a centrifugal casting machine.

(2) 48 minutes after the start of casting of the outer layer, a 100 mm-thick wall was cast at 1480 ° C. as an inner layer molten metal in a rotary mold.

(3) 100 minutes after the start of casting the outer layer, the outer layer and the inner layer are completely solidified. (4) After the roll was completely cooled, the roll was taken out of the mold, and after heat treatment and machining, shrink-fitting was performed on the arbor to obtain a roll of the final product.

As a result of ultrasonic inspection and cutting inspection of the roll body, the thickness of the outer layer was 180 mm due to the casting of the inner layer, the thickness of the inner layer was 85 mm, and the Cr content was 0.7 to 0.94%.
Met. Then, the outer layer and the inner layer were completely bonded to each other, and organizational continuity was recognized.

Table 4 shows the chemical compositions of the outer layer and the inner layer at the molten metal stage.

[0075]

[Table 4]

The chemical composition after solidification of the outer and inner layers of the roll cast with the composition shown in Table 4 is as shown in Table 5.

[0077]

[Table 5]

Table 6 shows the mechanical properties of the inner layer of the roll of the present invention in comparison with those of the conventional roll of the same size.

[0079]

[Table 6]

Even in the case of the rolls of the present invention having the compositions shown in Tables 4 and 5, by optimizing the alloy components forming the outer layer and limiting the carbide composition, wear resistance which does not cause segregation even under the action of centrifugal force is obtained. Using an outer layer material with uniform crack resistance and crack resistance, and using a tough graphite steel for the inner layer material, the outer layer and the inner layer are completely metallurgically bonded to form a centrifugally cast sleeve roll. be able to.

(Experimental Example 3) (See Tables 7 to 9) Rolls having a product body diameter of 1060 mm, an inner diameter of 550 mm, and a width of 460 mm were manufactured.

(1) As an outer layer, a molten metal having a thickness of 150 mm was cast at a casting temperature of 1510 ° C. into a mold rotating on a centrifugal casting machine.

(2) Thirty-two minutes after the start of casting the outer layer, an inner layer molten metal having a thickness of 160 mm was cast at 1490 ° C. in a rotary mold.

(3) After 100 minutes from the start of casting the outer layer, the outer layer and the inner layer are completely solidified. (4) After the roll was completely cooled, the roll was taken out of the mold, and after heat treatment and machining, shrink-fitting was performed on the arbor to obtain a roll of the final product.

As a result of ultrasonic inspection and cutting inspection of the roll body, the thickness of the outer layer was 120 mm due to the casting of the inner layer, the thickness of the inner layer was 128 mm, and the Cr content was 1.33 to 1.85.
%Met. Then, the outer layer and the inner layer were bonded to each other, and organizational continuity was recognized.

Table 7 shows the chemical compositions of the outer layer and the inner layer at the molten metal stage.

[0087]

[Table 7]

The chemical composition after solidification of the outer layer and the inner layer of the roll cast with the composition shown in Table 7 is as shown in Table 8.

[0089]

[Table 8]

Table 9 shows the mechanical properties of the inner layer of the roll of the present invention in comparison with those of the conventional roll of the same size.

[0091]

[Table 9]

In the rolls of the present invention having the compositions shown in Tables 7 and 8, the alloy components forming the outer layer were optimized and the carbide composition was limited, so that segregation did not occur even under the action of centrifugal force. Using an outer layer material with uniform crack resistance and crack resistance, and using a tough graphite steel for the inner layer material, the outer layer and the inner layer are completely metallurgically bonded to form a centrifugally cast sleeve roll. be able to.

[0093]

As described above, according to the present invention, the wear resistance and the crack resistance which do not cause segregation even under the action of centrifugal force are improved by optimizing the alloy component forming the outer layer and limiting the carbide composition. It is possible to provide a centrifugally cast sleeve roll in which a uniform outer layer material is used, a tough graphite steel is used for the inner layer material, and the outer layer and the inner layer are completely metallurgically bonded and integrated.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing the influence of a composite addition amount of V and Nb and a C amount on a base metal hardness.

FIG. 2 is a graph showing the effect of the composite addition amount of V and Nb and the C amount on base metal hardness.

FIG. 3 is a graph showing the effect of the composite addition amount of V and Nb and the C amount on the base metal hardness.

FIG. 4 is a graph showing the effect of the composite addition amount of V and Nb and the C amount on the base metal hardness.

FIG. 5 is a graph showing a hot wear ratio between an outer layer and an inner layer caused by a carbide distribution of a centrifugally cast ring material, and a content ratio Nb of Nb and V on a maximum crack depth in a thermal shock test.
FIG. 3 is a diagram showing the effect of / V.

FIG. 6 shows the hot wear ratio between the outer layer and the inner layer due to the carbide distribution of the ring material cast by centrifugal force, and the content ratio Nb of Nb and V on the maximum crack depth in the thermal shock test.
FIG. 3 is a diagram showing the effect of / V.

FIG. 7 shows the hot wear ratio between the outer layer and the inner layer caused by the carbide distribution of the ring material cast by centrifugal force, and the content ratio Nb of Nb and V on the maximum crack depth in the thermal shock test.
FIG. 3 is a diagram showing the effect of / V.

FIG. 8 shows the hot wear ratio between the outer layer and the inner layer caused by the carbide distribution of the centrifugally cast ring material, and the content ratio Nb of Nb and V on the maximum crack depth in the thermal shock test.
FIG. 3 is a diagram showing the effect of / V.

FIG. 9 is a schematic view showing a method for producing the roll of the present invention.

FIG. 10 is a schematic view showing a roll of the present invention.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiro Kataoka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (56) References JP-A-57-101645 (JP, A) JP-A-2-258949 (JP, A) JP-A-2-285047 (JP, A) JP-A-53-25213 (JP, A) JP-A-53-76119 (JP, A)

Claims (3)

(57) [Claims] 1. A centrifugally cast sleeve roll comprising an outer layer material and an inner layer material of graphite steel welded and integrated with the outer layer material, wherein the outer layer material has C: 1.0 to 3.5%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 3.0 to 12.0% , Mo: 2.0 to 8.0% ,
V: 3.0 to 10.0%, Nb: 0.6 to 7.0%, and the balance consists of Fe and unavoidable impurities.
In addition, the following formulas (1) and (2) are satisfied: V + 1.8Nb ≦ 7.5C−6.0% (1) 0.2 ≦ Nb / V ≦ 0.8 (2) ) The inner layer material is: C: 1.0 to 2.0%, Si: 1.6 to 2.4%, M
n: 0.2 to 1.0%, P: 0.05% or less, S: 0.03% or less, Ni: 0.
7% or less, Cr: 3.5% or less, Mo: 0.03 to 3.0% , the balance being Fe and unavoidable impurities , and the mixing ratio of the outer layer to the inner layer is restricted to the range of 5 to 35%. A centrifugal casting sleeve roll characterized by being made. 2. A centrifugally cast sleeve roll comprising an outer layer material and an inner layer material of graphite steel welded and integrated with the outer layer material, wherein the outer layer material has a C content of 1.0 to 3.5%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 3.0 to 12.0% , Mo: 2.0 to 8.0% ,
V: 3.0 to 10.0%, Nb: 0.6 to 7.0%, further contains at least one selected from Ni: 8.0% or less, Co: 10.0% or less, The balance consists of Fe and unavoidable impurities and satisfies the following equations (1) and (2)
And, V + 1.8Nb ≦ 7.5C-6.0 % ··· (1) 0.2 ≦ Nb / V ≦ 0.8 ··· (2) the inner layer material, C: 1.0 to 2. 0%, S1: 1.6 to 2.4%, M
n: 0.2 to 1.0%, P: 0.05% or less, S: 0.03% or less, Ni: 0.
7% or less, Cr: 3.5% or less, Mo: 0.03 to 3.0% , the balance being Fe and unavoidable impurities , and the mixing ratio of the outer layer to the inner layer is restricted to the range of 5 to 35%. A centrifugal casting sleeve roll characterized by being made. 3. A centrifugally cast sleeve roll comprising an outer layer material and an inner layer material of graphite steel welded and integrated with the outer layer material, wherein the outer layer material has C: 1.0 to 3.5%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 3 . 0 to 12.0% , Mo: 2.0 to 8.0% ,
V: 3.0 to 10.0%, Nb: 0.6 to 7.0%, Ni: 8.0% or less, Co: 10.0% or less, Cu:
2.0% or less, Ti: 2.0% or less, Zr: 2.0% or less , B: One or more selected from 0.1% or less, with the balance Fe and unavoidable Tomo and consisting of impurities
The following formulas (1) and (2) are satisfied: V + 1.8Nb ≦ 7.5C−6.0% (1) 0.2 ≦ Nb / V ≦ 0.8 (2) ) The inner layer material is: C: 1.0 to 2.0%, S1: 1.6 to 2.4%, M
n: 0.2 to 1.0%, P: 0.05% or less, S: 0.03% or less, N1: 0.
7% or less, Cr: 3.5% or less, Mo: 0.03 to 3.0% , the balance being Fe and unavoidable impurities , and the mixing ratio of the outer layer to the inner layer is restricted to the range of 5 to 35%. A centrifugal casting sleeve roll characterized by being made.