JP2594865B2 - Centrifugal casting roll and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugally cast roll having both abrasion resistance, crack resistance and toughness and 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 Conventionally, a roll for hot rolling which requires abrasion resistance is a composite roll composed of an outer layer and an inner layer. The inner layer material is manufactured by a centrifugal casting method using gray cast iron or ductile cast iron having good toughness.

[0003] However, due to the severer rolling conditions and the demand for improved productivity in rolling, there is a demand for a roll for rolling having more wear resistance and crack resistance.

[0004] Under such circumstances, for example, Japanese Patent 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.

[0005]

However, in a rolling roll using high-V cast iron as an outer layer material of a centrifugal casting roll, V carbide having a small specific gravity segregates due to centrifugal separation.
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.

Incidentally, Japanese Patent Application Laid-Open Nos. 58-87249 and 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-A-58-87249 is directed to shrink-fitting or assembling rolls, and there is a problem of slippage between the outer layer and the shaft material during rolling. Japanese Patent Application Laid-Open No. 1-96355 can apply only a special manufacturing method other than the centrifugal force casting method such as a special casting overlaying method, and has problems in productivity and economy.

[0007] That is, in the production of a rolling roll, it is possible to significantly improve the wear resistance by incorporating a large amount of V in the outer layer of the roll, but the most excellent productivity and economical efficiency in the production of a composite roll. If the centrifugal casting method generally used is adopted, there is a problem that segregation of carbides occurs due to centrifugal separation 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. Aiming to provide a centrifugally cast roll made by integrating the outer layer material and the shaft core material completely metallurgically using the toughest ductile cast iron among cast iron materials as the shaft core material. .

[0009]

According to a first aspect of the present invention, there is provided a centrifugally cast roll comprising an outer layer material and a ductile cast iron core material 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%. Tomo When contained, consisting of the balance 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) Material: C: 2.8 to 3.8%, Si: 2.0 to 3.0%, Mn: 0.3 to 1.0%, P: 0.1% or less, S: 0.
04% or less, Ni: 0.3 to 2.0%, Cr: 1.5% or less, Mo:
Containing 0.03 to 1.0 percent, it consists balance of Fe and unavoidable impurities, axial
In this case, the mixing ratio of the exterior to the steel is restricted to the range of 5 to 35% .

According to a second aspect of the present invention, there is provided a centrifugally cast roll comprising an outer layer material and a ductile cast iron core material welded and integrated with the outer layer material, wherein the outer layer material comprises: 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 selected from the group consisting of Fe and inevitable impurities, and satisfying the following formulas (1) and (2).
Adding, V + 1.8Nb ≦ 7.5C-6.0 % ... (1) 0.2 ≦ Nb / V ≦ 0.8 ... (2) the mandrel material, C: 2.8~3.8%, Si: 2.0-3.0%, Mn: 0.3-1.0%, P: 0.1% or less, S: 0.
04% or less, Ni: 0.3 to 2.0%, Cr: 1.5% or less, Mo:
Containing 0.03 to 1.0 percent, it consists balance of Fe and unavoidable impurities, axial
The outer layer mixing ratio is restricted to the range of 5 to 35% .

According to a third aspect of the present invention, there is provided a centrifugally cast roll comprising an outer layer material and a ductile cast iron core material 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
Satisfies the following equations (1) and (2): V + 1.8Nb ≦ 7.5C-6.0%
(1) 0.2 ≦ Nb V ≦ 0.8 ...
(2) The shaft core material is: C: 2.8 to 3.8%, Si: 2.0 to 3.0%, Mn: 0.3 to 1.0%, P: 0.1% or less, S: 0.
04% or less, Ni: 0.3 to 2.0%, Cr: 1.5% or less, Mo:
Containing 0.03 to 1.0 percent, it consists balance of Fe and unavoidable impurities, axial
In this case, the mixing ratio of the exterior to the steel is restricted to the range of 5 to 35% .

[0012]

[0013]

[0014]

[Action]

 (A) Reasons for limiting alloy elements in outer layer materials

C: 1.0 to 3.5% C is an essential element for forming a hard carbide for improving 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 .
With that, hardenability of the base, improving the temper softening resistance, 2.0% or more essential element for strengthening the matrix structure 必
It is important , however, that if the content exceeds 8.0%, the crack resistance decreases, so 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 the heat resistance is saturated, so the upper limit is made 10.0% from the viewpoint of economy.

[0022] Cu: 2.0% or less Cu strengthens the matrix structure, will be added to improve the high-temperature hardness, 2. If it exceeds 0%, the surface properties of the roll are deteriorated, and the wear resistance and crack resistance are reduced . Therefore, the upper limit is made 2.0% .

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 improve wear resistance and crack resistance. However, if Ti and Zr exceed 2.0%, V, Nb The upper limit is 2.0 because the shape of the composite carbide deteriorates and 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 also 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.

Incidentally, 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,
Of the relationship between the outer layer caused by the carbide distribution of the ring material cast by centrifugal force and the wear ratio between the outer layer and the shaft core, the maximum crack depth in the thermal shock test and the Nb / V content ratio Nb / V. Are shown in FIGS. 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 of 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, it is possible to obtain a uniform outer layer material even when manufactured by the centrifugal casting method, and to ensure that the crack resistance is not impaired: 0.2 ≦ Nb / V ≦
It became clear that it was necessary to satisfy 0.8.

In FIG. 5 to FIG. 8, the "wear ratio (axial core / outer layer)" means the amount of wear (Iw) of the test piece taken from the axis side of the ring material and the test piece taken from the outer layer side. It is the ratio (Iw / Ow) with respect to the amount of wear (Ow), and the “maximum thermal shock crack 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 two-disk sliding wear method of a mating material of φ190 × 15 and a mating material of φ50 × 10, and the test material was pressed 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 Limiting Alloy Elements in Shaft Core In a composite roll, it is essential to mix the shaft core with the inner surface of the outer layer in order to metallurgically bond the outer layer and the shaft core. However, the outer layer must not be mixed excessively until the excellent toughness, which is a function of the shaft core material, is impaired.
For this reason, the casting conditions are selected and the mixing ratio of the outer layer to the shaft core material (weight% of the weight of the outer layer material mixed into the shaft core material with respect to the total weight of the shaft core material) is maintained in an appropriate range. Is extremely important. In the present invention, it has been found that it is optimal to regulate this range to 5 to 35%. That is, below 5%,
Since the thick segregated layer of C and Si formed on the innermost surface of the outer layer by centrifugal force remains without being completely washed, the soundness of the boundary layer cannot be ensured. On the other hand, if the content exceeds 35%, a large amount of Cr and C, which particularly deteriorate the properties of the shaft core material, is mixed in the outer layer components, and the shaft core material composition after solidification becomes a high C-Cr type. This leads to poor graphite shape and remarkable white iron, and its function is reduced.

Therefore, the mixing ratio of the outer layer is regulated in the range of 5 to 35%, and the chemical composition of the molten metal is adjusted so that the composition of the core material after solidification satisfies the following range in consideration of an increase in the composition. You have to choose.

C: 2.8 to 3.8% If C is less than 2.8%, the amount of graphite decreases, and the material properties as ductile cast iron cannot be sufficiently exhibited. Meanwhile, 3.
If it exceeds 8%, it will be fragile, so 2.8 to 3.8
%.

Si: 2.0 to 3.0% If the content of Si is less than 2.0%, the amount of graphite decreases and a large amount of cementite precipitates, so that it is hard and brittle. Meanwhile, 3.0
%, The amount of graphite becomes excessively large and the strength is deteriorated. Therefore, it is specified in the range of 2.0 to 3.0%.

Mn: 0.3 to 1.0% Mn is effective in suppressing the harm of S, but if it is less than 0.3%, its effect is not sufficient.
Since the material deteriorates, it is specified in the range of 0.3% to 1.0%.

P: 0.1% or less P increases the fluidity of the molten metal, but is made 0.1% or less because the material becomes brittle.

S: 0.04% or less S must be kept low because it inhibits spheroidization of graphite.

Ni: 0.3 to 2.0% Ni promotes graphitization, but if it is less than 0.3%, its effect is insufficient, and if it exceeds 2.0%, there is no significant effect. Therefore, it is specified in the range of 0.3 to 2.0%.

Cr: 1.5% or less In the case of Cr, the outer layer of Cr re-dissolves and diffuses in the shaft core material, and if its content exceeds 1.5%, the material strength deteriorates. The Cr content is set to less than 1.0%, and as a result, the total of the Cr content and the Cr content re-dissolved and diffused from the outer layer is set to 1.5% or less.

[0046] Mo: 0.03 to 1.0% Mo has the effect of increasing the base hardness, 0.03%
Is insufficient, the effect is less than, becomes brittle if it exceeds 1.0%, also because some uneconomical, 0.03 to 1.0
% .

When the composition of the inner layer after solidification satisfies the above range, the function of the ductile cast iron used as the shaft core material can be obtained. In the case of the present invention, V and N mixed from the outer layer are used.
By containing b, there is an advantage that the mechanical properties are further improved as compared with general ductile cast iron as a composite roll shaft core.

This is because, by keeping the core composition after solidification within the above range, the formation of carbides can be suppressed.
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. In the case of the roll of the present invention, this effect allows the roll to be used for higher-load rolling than before.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A centrifugally cast roll according to the present invention has the above-described structure, and a method of manufacturing this roll will be described with reference to an example shown in FIG.

First, after the molten metal to form the outer layer 1 is cast into a metal mold having an inner surface coated with a refractory material by rotating on a centrifugal casting machine, the outer layer 1 is completely solidified. And the shaft core 2 is cast from above, and the outer layer 1 and the shaft core 2 are completely metallurgically bonded to form an integral roll. Even if the outer layer 1 does not completely solidify, the shaft core material 2 may be cast by an appropriate method in which the inner surface is partially solidified in a horizontal or inclined manner.

(Experimental Example 1) (See Tables 1 to 3) Rolls having a product body diameter of 820 mm, a body length of 2,000 mm, and a total length of 4800 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) The outer layer is completely solidified 30 minutes after the casting of the outer layer is started. (3) Then, the mold is set upright and ductile cast iron as a shaft core material is cast from above at 1410 ° C., and the mold is completely filled, heated and covered with a heat insulating material.

(4) After complete cooling, the roll was taken out of the mold, heat-treated and machined 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 88 mm due to casting of the shaft core material. Sex was observed.

Table 1 shows the chemical composition of the outer layer and the shaft core material at the molten metal stage.

[0057]

[Table 1]

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

[0059]

[Table 2]

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

[0061]

[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 are optimized and the carbide composition is limited so that segregation does not occur even under the action of centrifugal force. In addition to using an outer layer material with uniformity and crack resistance, the core material is made of ductile cast iron, which is the strongest cast iron material, and the outer layer material and the shaft material are completely metallurgically bonded to form an integral body. Centrifugally cast roll.

(Experimental Example 2) (See Tables 4 to 6) Rolls having a product body diameter of 680 mm, a body length of 1500 mm, and a total length of 3400 mm were produced.

(1) As an outer layer, a molten metal having a thickness of 80 mm was cast at a casting temperature of 1500 ° C. into a mold rotating on a centrifugal casting machine.

(2) The outer layer is completely solidified 27 minutes after the start of casting the outer layer. (3) Then, the mold is set up vertically, and ductile cast iron as a shaft core material is cast at 1410 ° C. from above, and the mold is completely filled, heated, and covered with a heat insulating material.

(4) After complete cooling, the roll was taken out of the mold, heat-treated and machined to obtain a roll of the final product.

As a result of ultrasonic flaw detection and cutting inspection of the roll body, the thickness of the outer layer was 69 mm due to casting of the shaft core material, and the outer layer and the shaft core material were completely bonded to each other. Sex was observed.

Table 4 shows the chemical composition of the outer layer and the shaft core material at the molten metal stage.

[0069]

[Table 4]

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

[0071]

[Table 5]

Table 6 shows the mechanical properties of the core of the roll of the present invention in comparison with those of the conventional roll of the same size.
It is like.

[0073]

[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. In addition to using an outer layer material with uniformity and crack resistance, the core material is made of ductile cast iron, which is the strongest cast iron material, and the outer layer material and the shaft material are completely metallurgically bonded to form an integral body. Centrifugally cast roll.

(Experimental Example 3) (See Tables 7 to 9) Rolls having a product body diameter of 820 mm, a body length of 2,000 mm, and a total length of 4800 mm were produced.

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

(2) The outer layer is completely solidified 30 minutes after the start of casting the outer layer. (3) Then, the mold is set upright and ductile cast iron as a shaft core material is cast from above at 1410 ° C., and the mold is completely filled, heated and covered with a heat insulating material.

(4) After complete cooling, the roll was taken out of the mold, heat-treated and machined 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 89 mm due to the casting of the shaft core material, and the outer layer and the shaft core material were completely bonded to each other. Sex was observed.

Table 7 shows the chemical composition of the outer layer and the shaft core material at the molten metal stage.

[0081]

[Table 7]

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

[0083]

[Table 8]

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

[0085]

[Table 9]

Even in the case of the rolls of the present invention having the compositions shown in Tables 7 and 8, 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. In addition to using an outer layer material with uniformity and crack resistance, the core material is made of ductile cast iron, which is the strongest cast iron material, and the outer layer material and the shaft material are completely metallurgically bonded to form an integral body. Centrifugally cast roll.

(Experimental Example 4) (See Tables 10 to 12) Rolls having a product body diameter of 820 mm, a body length of 2,000 mm, and a total length of 4800 mm were produced.

(1) A molten metal having a thickness of 100 mm as an outer layer was cast at a casting temperature of 1510 ° C. into a mold rotating on a centrifugal casting machine.

(2) The outer layer is completely solidified 30 minutes after the start of casting the outer layer. (3) Then, the mold is set up vertically, and ductile cast iron as a shaft core material is cast at 1410 ° C. from above, and the mold is completely filled, heated, and covered with a heat insulating material.

(4) After complete cooling, the roll was removed from the mold, heat-treated and machined to obtain a roll of the final product.

As a result of ultrasonic flaw detection and cutting inspection of the roll body, the thickness of the outer layer was 89 mm due to casting of the shaft core material. Sex was observed.

Table 10 shows the chemical composition of the outer layer and the shaft core material at the molten metal stage.

[0093]

[Table 10]

The chemical composition after solidification of the outer layer and the core of the roll cast with the composition shown in Table 10 is as shown in Table 11.

[0095]

[Table 11]

Table 1 shows the mechanical properties of the core of the roll of the present invention as compared with those of the conventional roll of the same size.
Like 2.

[0097]

[Table 12]

Even in the case of the rolls of the present invention having the compositions shown in Tables 10 and 11, the alloy components forming the outer layer are optimized and the carbide composition is limited so that segregation does not occur even under the action of centrifugal force. In addition to using an outer layer material with uniformity and crack resistance, the core material is made of ductile cast iron, which is the strongest cast iron material, and the outer layer material and the shaft material are completely metallurgically bonded to form an integral body. Centrifugally cast roll.

[0099]

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 obtained by optimizing the alloy components forming the outer layer and limiting the carbide composition. In addition to using a uniform outer layer material, the toughest ductile cast iron among cast iron materials is used for the shaft core material.
The outer layer material and the shaft core material can be completely metallurgically bonded to obtain an integrated centrifugal casting roll.

[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 view showing a hot wear ratio between an outer layer and a shaft core 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 is a graph showing a hot wear ratio between an outer layer and a shaft core caused by a carbide distribution in 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. 7 is a graph showing a hot wear ratio between an outer layer and a shaft core caused by a carbide distribution of a ring material cast by centrifugal force, 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. 8 is a graph showing a hot wear ratio between an outer layer and a shaft core 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. 9 is a schematic view showing a roll of the present invention.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshihiro Kataoka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. JP-A-5-305312 (JP, A) JP-A-3-53041 (JP, A) JP-A-2-258949 (JP, A)

Claims (3)

(57) [Claims] 1. A centrifugally cast roll comprising an outer layer material and a ductile cast iron shaft core material 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%. Tomo When contained, consisting of the balance 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) Material: C: 2.8 to 3.8%, Si: 2.0 to 3.0%, Mn: 0.3 to 1.0%, P: 0.1% or less, S: 0.
04% or less, Ni: 0.3 to 2.0%, Cr: 1.5% or less, Mo:
Containing 0.03 to 1.0 percent, consists balance of Fe and unavoidable impurities, centrifugal cast roll outer layer mixing ratio of the axial core is characterized by comprising is restricted to a range from 5 to 35%. 2. A centrifugally cast roll comprising an outer layer material and a ductile cast iron shaft core material 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 selected from the group consisting of Fe and unavoidable impurities, and satisfying the following formulas (1) and (2).
Adding, V + 1.8Nb ≦ 7.5C-6.0 % ... (1) 0.2 ≦ Nb / V ≦ 0.8 ... (2) the mandrel material, C: 2.8~3.8%, Si: 2.0-3.0%, Mn: 0.3-1.0%, P: 0.1% or less, S: 0.
04% or less, Ni: 0.3 to 2.0%, Cr: 1.5% or less, Mo:
Containing 0.03 to 1.0 percent, consists balance of Fe and unavoidable impurities, centrifugal cast roll outer layer mixing ratio of the axial core is characterized by comprising is restricted to a range from 5 to 35%. 3. A roll made by centrifugal casting comprising an outer layer material and a ductile cast iron core material 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 being Fe and inevitable 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) Material: C: 2.8 to 3.8%, S1: 2.0 to 3.0%, Mn: 0.3 to 1.0%, P: 0.1% or less, S: 0.
04% or less, N1: 0.3 to 2.0%, Cr: 1.5% or less, Mo:
Containing 0.03 to 1.0 percent, consists balance of Fe and unavoidable impurities, centrifugal cast roll outer layer mixing ratio of the axial core is characterized by comprising is restricted to a range from 5 to 35%.