JPH05311319A - Centrifugally cast roll and its production - Google Patents

Abstract

PURPOSE:To provide a centrifugally cast roll combining wear resistance, crack resistance and toughness. CONSTITUTION:The centrifugally cast roll can be prepared by integrally bonding while fusing an external layer material having a composition consisting of 1.0-3.5% C, <=2.0% Si, <=2.0% Mn, <=12.0% Cr, <=8.0% Mo, 3.0-10.0% V, 0.6-7.0% Nb, and the balance Fe with inevitable impurities and a shaft core material of ductile cast iron having a composition consisting of 2.8-3.8% C, 2.0-3.0% Si, 0.3-1.0% Mn, <=0.1% P, <=0.04% S, 0.3-2.0% Ni, <=1.5% Cr, <=1.0% Mo, and the balance Fe with inevitable impurities.

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 which has abrasion resistance, crack resistance and toughness and is suitable for use as a rolling roll and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a hot rolling roll required to have wear resistance is a composite roll consisting of an outer layer and an inner layer, and a high Cr cast iron or Ni grain cast iron in which cementite type carbide is crystallized as an outer layer material. The inner layer material is manufactured by centrifugal force casting method using gray cast iron or ductile cast iron with good toughness.

However, due to severer rolling conditions and demand for improved productivity in rolling, it is required to provide rolling rolls having further wear resistance and crack resistance.

Under such circumstances, for example, Japanese Patent Laid-Open No. 60-124
No. 407 and Japanese Patent Laid-Open No. 61-177355 propose to use high V cast iron as an outer layer material of a conventional centrifugal casting roll.

[0005]

However, in the rolling roll using high V cast iron as the outer layer material of the centrifugal force casting roll, V carbide having a small specific gravity is segregated by centrifugal separation,
The characteristics in the outer layer of the roll become uneven in the thickness direction. This tendency is remarkable as the outer layer thickness of the large roll increases, and there is a problem that the roll cannot be used as a practical roll.

Incidentally, Japanese Unexamined Patent Publication (Kokai) No. 58-87249 and Japanese Unexamined Patent Publication (Kokai) No. 1-96355 propose roll materials to which cast steel and cast iron which are highly alloyed like high speed steel are applied. However,
Japanese Patent Laid-Open No. 58-87249 is intended for shrink-fitting or assembling rolls, and slippage between the outer layer and the shaft material that occurs during rolling poses a problem. Further, Japanese Patent Application Laid-Open No. 1-96355 can only be applied to a special manufacturing method other than the centrifugal force casting method such as a special cast overlay method, which causes problems in productivity and economy.

That is, when a rolling roll is manufactured, it is possible to remarkably improve the wear resistance by adding a large amount of V to the outer layer of the rolling roll, but the productivity and the economical efficiency are most excellent at the time of manufacturing the composite roll. However, when the centrifugal casting method which is generally carried out is adopted, there is a problem in that the segregation of carbides occurs due to the centrifugal separation and predetermined characteristics cannot be obtained uniformly.

The present invention uses an outer layer material having uniform wear resistance and crack resistance that 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. At the same time, it is an object of the present invention to provide a centrifugally cast roll in which the toughest ductile cast iron among cast iron-based materials is used for the shaft core material, and the outer layer material and the shaft core material are completely metallurgically bonded and integrated. ..

[0009]

The present invention according to claim 1 is a centrifugally cast roll comprising an outer layer material and a ductile cast iron mandrel fused and integrated with the outer layer material. Material: C: 1.0-3.5%, Si: 2.0% or less, Mn: 2.0% or less, Cr: 12.0% or less, Mo: 8.0% or less, V: 3.0-
10.0%, Nb: 0.6-7.0%, balance Fe and unavoidable impurities, and the mandrel is 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
.About.2.0%, Cr: 1.5% or less, Mo: 1.0% or less, and the balance Fe and unavoidable impurities.

According to a second aspect of the present invention, there is provided a centrifugal casting roll comprising an outer layer material and a shaft core material of ductile cast iron fused and integrated with the outer layer material, wherein the outer layer material is C: 1.0. ~ 3.5%, Si: 2.0% or less, Mn: 2.0% or less, Cr: 12.0% or less, Mo: 8.0% or less, V: 3.0 ~
10.0%, Nb: 0.6 to 7.0%, Ni: 8.0% or less, C
o: contains at least one selected from 10.0% or less, and the balance Fe and unavoidable impurities, and the shaft core material is C: 2.8 to 3.8%, Si: 2.0 to 3.0%, Mn: 0.3 ~
1.0%, P: 0.1% or less, S: 0.04% or less, Ni: 0.3
.About.2.0%, Cr: 1.5% or less, Mo: 1.0% or less, and the balance Fe and unavoidable impurities.

According to a third aspect of the present invention, there is provided a centrifugal casting roll comprising an outer layer material and a shaft core material of ductile cast iron fused and integrated with the outer layer material, wherein the outer layer material is C: 1.0. ~ 3.5%, Si: 2.0% or less, Mn: 2.0% or less, Cr: 12.0% or less, Mo: 8.0% or less, V: 3.0 ~
10.0%, Nb: 0.6 to 7.0%, Ni: 8.0% or less, C
o: 10.0% or less, Cu: 2.0% or less, Ti: 2.0% or less, Zr: 2.0% or less, W: 1.0% or less, B: 0.1% or less, and one or more kinds selected from them are contained. , The balance Fe and unavoidable impurities, and the axial 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
.About.2.0%, Cr: 1.5% or less, Mo: 1.0% or less, and the balance Fe and unavoidable impurities.

The present invention according to claim 4 provides claims 1 to 3.
In the present invention according to any one of the above, further outer layer material is
The equations (1) and (2) are satisfied. V + 1.8 Nb ≤ 7.5 C-6.0% (1) 0.2 ≤ Nb / V ≤ 0.8 (2)

The present invention according to claim 5 provides the invention according to any one of claims 1 to 4.
In manufacturing the centrifugally cast roll described in any one of 1 to 3, the ratio of the outer layer mixed into the shaft core is regulated within the range of 5 to 35%.

[0014]

[Action]

 (A) Reasons for limiting alloying elements in the outer layer material

C: 1.0 to 3.5% C is an essential element for forming a hard carbide which improves the wear resistance of the outer layer material of the roll, and is required to be 1.0% or more.
%, The crack resistance will drop significantly, so the upper limit is
3.5%

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

Mn: 2.0% or less Mn is required as in the case of Si, but if it exceeds 2.0%, crack resistance is deteriorated, which is not preferable and the upper limit is 2.0%.
And

Cr: 12.0% or less Cr forms an carbide and is an effective element for improving wear resistance, but if it exceeds 12.0%, when V and Nb, which are the objects of the present invention, are added. The wear resistance deteriorates, so the upper limit is 12.0%.

Mo: 8.0% or less Mo forms a carbide like Cr and is effective in improving wear resistance, and is also effective in improving the hardenability and temper softening resistance of the matrix and strengthening the matrix structure. However, if it exceeds 8.0%, the crack resistance decreases, so the upper limit is made 8.0%.

Ni: 8.0% or less, Co: 10.0% or less Ni is added to improve hardenability and strengthen the matrix structure, but 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 8.0%.

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

Cu: 2.0% or less, W: 1.0% or less Both Cu and W are added to strengthen the matrix structure and improve high temperature hardness, but if Cu exceeds 2.0%, the surface properties of the roll deteriorate. At the same time, the upper limit is set to 2.0% in order to reduce wear resistance and crack resistance, and W is an element having a large specific gravity, and if added in excess, it promotes segregation of V-based carbide due to centrifugation, so the upper limit is set to 1.0%.

Ti: 2.0% or less, Zr: 2.0% or less,
B: 0.1% or less Ti, Zr, and B are added in order to suppress the formation of coarse eutectic carbides and improve wear resistance and crack resistance, but when Ti and Zr exceed 2.0%, V and Nb The upper limit is 2.0 because it deteriorates the shape of the composite carbide and conversely reduces wear resistance.
%, And if B exceeds 0.1%, it segregates at the grain boundaries to reduce 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 combined additions and content limiting conditions are the greatest features of the present invention.

V is a hard MC that is most effective in improving wear resistance
Or, it is an essential element for forming M ₄ C ₃ carbide, and 3.0% or more is necessary to exert its effect.
%, The crack resistance is lowered and manufacturing problems occur, so the upper limit is made 10.0%.

Nb, like V, is a hard MC effective for wear resistance.
Formed carbides are formed, but if added alone, they become coarse lumpy carbides and their effect cannot be obtained, and crack resistance becomes a problem.

In the outer layer material of the present invention, the above 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 hardness of the base metal when adding
And the results of examining the relationship between the outer layer, the hot wear ratio between the shaft cores, the maximum depth of cracks in the thermal shock test, and the Nb, V content ratio Nb / V due to the carbide distribution of the centrifugally cast ring material. Are shown in FIGS. 1 to 4 and 5 to 8, respectively.

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

In the experiment of FIG. 1, Si: 0.5%, Mn:
0.5%, Cr: 6.8%, Mo: 3.2%, C,
A sample of 25 mm Y / block obtained by casting a molten metal in which V and Nb were changed was subjected to a normalizing treatment at 1000 ° C and a tempering treatment at 550 ° C. In the experiment of Fig. 2, Si: 0.5%, Mn: 0.
25mmY containing a molten metal containing 5%, Ni: 2.7%, Cr: 7.2%, Mo: 3.5% and varying C, V, Nb.
-For the block, the sample subjected to 1000 ° C normalizing treatment and 550 ° C tempering treatment was used.
%, Mn: 0.4%, Ni: 1.5%, Cr: 5.7%, M
1050 for a 25 mm Y-block cast from a melt containing o: 2.8% and Co: 3.2% and varying C, V and Nb.
Using a sample that has been subjected to a ℃ normalizing treatment and a 550 ℃ tempering treatment, the experiment of FIG. 4 shows that Si: 0.3%, Mn: 0.4%, C
Contains r: 6.0%, Mo: 3.2%, Co: 4.1%,
A 25 mm Y-block obtained by casting a molten metal having different C, V, and Nb was subjected to 1050 ° C. quenching treatment and 550 ° C. tempering treatment.

Further, in order to obtain a uniform outer layer material even when manufactured by the centrifugal casting method from FIGS. 5 to 8 and not to impair crack resistance, 0.2 ≦ Nb / V ≦
It became clear that it is necessary to satisfy 0.8.

5 to 8, "wear ratio (axial core / outer layer)" means the wear amount (Iw) of the test piece taken from the axial center side of the ring material and the test piece taken from the outer layer side. It is the ratio (Iw / Ow) to the amount of wear (Ow), and the "maximum depth of thermal shock crack" is the maximum depth of cracks generated in the thermal shock test.

In the experiment of FIG. 5, C: 2.5%, Si:
0.5%, Mn: 0.5%, Cr: 6.5%, Mo: 3.5%,
V: 5.4%, Nb: 0 to 8.0% molten metal centrifugally cast (140 G) to obtain a ring sample with a wall thickness of 100 mm, which was subjected to normalizing treatment at 1000 ° C and tempering treatment at 550 ° C In the experiment of FIG. 6, C: 2.7%, Si: 0.6
%, Mn: 0.5%, Ni: 3.2%, Cr: 7.4%, M
A ring sample with a wall thickness of 100 mm obtained by centrifugal casting (140 G) of a molten metal containing o: 3.7%, V: 5.8% and Nb: 0 to 7.5% was tempered at 1000 ° C and tempered at 550 ° C. 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: 0-7.2% melt containing centrifugal force (14
0) The ring sample with a wall thickness of 100 mm obtained by
Using a sample that has been subjected to a 50 ° C. normalization treatment and a 550 ° C. tempering process, 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: 0-6.0% molten metal was centrifugally cast (140 G) to obtain a ring sample with a wall thickness of 100 mm, which was quenched at 1050 ° C and tempered at 550 ° C. Was used.

A wear test was conducted by heating the mating material to 800 ° C. by the sliding wear method of a two-disc disc of a mating material of φ190 × 15 and a test material of φ50 × 10, and pressing the test material at 800 rpm under a pressure of 100 kgf. Rotation was performed at a slip rate of 3.9%, and the wear loss after 120 minutes was measured.

The thermal shock test was carried out by pressing a 55 × 40 × 15 plate-shaped test piece against a roller rotating at 1200 rpm under the conditions of a load of 150 kgf and a contact time of 15 s, and the test piece was generated. The crack length was measured.

Further, as the heat treatment conditions applied to 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 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 (rapid cooling after austenizing) are possible.
In addition, tempering is performed by selecting the optimum conditions in the range of 500 to 600 ° C.

(B) Reasons for Limiting Alloying Elements in Shaft Core Material In the composite roll, in order to metallurgically bond the outer layer and the shaft core material, it is essential to mix the inner surface side of the outer layer and the shaft core material. However, the outer layer should not be excessively mixed until the excellent toughness, which is the function of the mandrel, is impaired.
For this reason, select casting conditions and keep the mixing ratio of the outer layer to the shaft core material (weight ratio of the weight of the outer layer material mixed in the shaft core material to the total weight of the shaft core material) within 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 dense segregation layer of C and Si formed on the innermost surface of the outer layer by centrifugal separation remains without being completely washed, the soundness of the boundary layer cannot be ensured. On the other hand, if it exceeds 35%, a large amount of Cr and C among the components of the outer layer, which particularly deteriorate the characteristics of the shaft core material, are mixed in, and the composition of the shaft core material after solidification becomes a high C-Cr system. This leads to poor graphite shape and marked whitening, and its function declines.

Therefore, the mixing ratio of the outer layer is regulated within the above range of 5 to 35%, and the chemical composition of the molten metal should be controlled so that the composition of the mandrel after coagulation satisfies the following range in consideration of the increase in the components. You have to choose.

C: 2.8 to 3.8% When C is less than 2.8%, the amount of graphite is small, and the material characteristics as ductile cast iron cannot be sufficiently exhibited. On the other hand, 3.
Since it becomes brittle when contained in excess of 8%, 2.8-3.8
Specify in the range of%.

Si: 2.0 to 3.0% When Si is less than 2.0%, the amount of graphite becomes small and a large amount of cementite precipitates, so that it becomes hard and brittle. On the other hand, 3.0
%, The amount of graphite becomes too large and the strength deteriorates. Therefore, the content is specified in the range of 2.0 to 3.0%.

Mn: 0.3 to 1.0% Mn is effective in suppressing the damage of S, but if it is less than 0.3%, the effect is not sufficient, and if it exceeds 1.0%,
Since it deteriorates the material, 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 makes the material fragile, so P is 0.1% or less.

S: 0.04% or less S inhibits the spheroidization of graphite, so it is necessary to keep it low, so S is 0.04% or less.

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

Cr: 1.5% or less As for Cr, the Cr in the outer layer is redissolved and diffused in the shaft core material, and if the content exceeds 1.5%, the material strength deteriorates. The Cr content should be less than 1.0% and, as a result, the total amount of Cr content which is redissolved and diffused from the outer layer is 1.5% or less.

Mo: 1.0% or less Mo has the effect of increasing the matrix hardness, but if it exceeds 1.0%, it becomes brittle and uneconomical. Therefore, it is set to 1.0% or less.

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 present invention, V and N mixed from the outer layer are obtained.
By containing b, there is an advantage that mechanical properties are further improved as compared with general ductile cast iron as a composite roll shaft core.

This is because in addition to suppressing the formation of carbides by keeping the axial core composition after solidification within the above range,
V which has a grain refining effect and is a hardenability improving element
And Nb are contained in appropriate amounts, and a fine bainite matrix structure with extremely few carbides can be obtained by high temperature heat treatment. In the case of the roll of the present invention, due to this effect, it can be used for higher load rolling than ever.

[0049]

EXAMPLE A centrifugally cast roll according to the present invention has the above-described structure, and a method for 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 into a metal mold whose inner surface is coated with a refractory material by rotating on a centrifugal casting machine, the outer layer 1 is completely solidified and then the mold is cast. Is erected vertically, the shaft core material 2 is cast from the upper part, and the outer layer 1 and the shaft core material 2 are completely metallurgically bonded to form an integral roll. Even if the outer layer 1 is not completely solidified, the shaft core material 2 may be cast by an appropriate method in which the inner surface is partially unsolidified and they are horizontal or inclined.

(Experimental Example 1) (See Tables 1 to 3) A roll having a product body diameter of φ820 mm, a body length of 2000 mm and a total length of 4800 mm was manufactured.

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

(2) The outer layer completely solidifies 30 minutes after the casting of the outer layer is started. (3) After that, the mold is erected straight, and ductile cast iron as a shaft core material is cast from the upper part at 1410 ° C. to completely fill the mold, press it, and cover it with a heat insulating material.

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

As a result of ultrasonic flaw detection and cutting examination of the roll body, the thickness of the outer layer was 88 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 and were structurally continuous. The sex was recognized.

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

[0057]

[Table 1]

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

[0059]

[Table 2]

The mechanical properties of the shaft core of the roll of the present invention are shown in Table 3 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, by optimizing the alloy components forming the outer layer and limiting the carbide composition, wear resistance that does not cause segregation or the like even under the action of centrifugal force. In addition to using an outer layer material with uniform cracking resistance and crack resistance, the toughest ductile cast iron among cast iron materials is used for the shaft core material, and the outer layer material and the shaft core material are completely metallurgically combined to form one body. It can be a roll made by centrifugal casting.

(Experimental Example 2) (See Tables 4 to 6) A roll having a product barrel diameter of 680 mm, a barrel length of 1500 mm and a total length of 3400 mm was manufactured.

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

(2) The outer layer is completely solidified 27 minutes after the casting of the outer layer is started. (3) After that, the mold is erected vertically, and ductile cast iron as a shaft core material is cast at 1410 ° C. from the upper part to completely fill the mold, raise it, and cover it with a heat insulating material.

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

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 the casting of the shaft core material, and the outer layer and the shaft core material were completely bonded to each other and structurally continuous. The sex was recognized.

Table 4 shows the chemical compositions of the outer layer and the mandrel in the molten metal stage.

[0069]

[Table 4]

The chemical composition after solidification of the outer layer and the shaft 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 shaft core of the roll of the present invention in comparison with that of the conventional roll of the same size.
Is like.

[0073]

[Table 6]

Even in 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, segregation resistance does not occur even under the action of centrifugal force. In addition to using an outer layer material with uniform cracking resistance and crack resistance, the toughest ductile cast iron among cast iron materials is used for the shaft core material, and the outer layer material and the shaft core material are completely metallurgically combined to form one body. It can be a roll made by centrifugal casting.

(Experimental Example 3) (See Tables 7 to 9) A roll having a product cylinder diameter of φ820 mm, a cylinder length of 2000 mm and a total length of 4800 mm was manufactured.

(1) A molten metal having a wall thickness of 100 mm was cast as an outer layer at a casting temperature of 1500 ° C. in 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) After that, the mold is erected straight, and ductile cast iron as a shaft core material is cast from the upper part at 1410 ° C. to completely fill the mold, press it, and cover it with a heat insulating material.

(4) After being completely cooled, the roll was taken out from the mold, heat-treated and machined to obtain a final product roll.

As a result of ultrasonic flaw detection and cutting examination 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 and were structurally continuous. The sex was recognized.

Table 7 shows the chemical compositions of the outer layer and the mandrel 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]

The mechanical properties of the shaft core of the roll of the present invention are shown in Table 9 in comparison with those of the conventional roll of the same size.

[0085]

[Table 9]

Even in 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, segregation etc. will not occur even under the action of centrifugal force. In addition to using an outer layer material with uniform cracking resistance and crack resistance, the toughest ductile cast iron among cast iron materials is used for the shaft core material, and the outer layer material and the shaft core material are completely metallurgically combined to form one body. It can be a roll made by centrifugal casting.

(Experimental Example 4) (See Tables 10 to 12) A roll having a product cylinder diameter of φ820 mm, a cylinder length of 2000 mm and a total length of 4800 mm was manufactured.

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

(2) The outer layer is completely solidified 30 minutes after the casting of the outer layer is started. (3) After that, the mold is erected vertically, and ductile cast iron as a shaft core material is cast at 1410 ° C. from the upper part to completely fill the mold, raise it, and cover it with a heat insulating material.

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

As a result of ultrasonic flaw detection and cutting examination 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 and were structurally continuous. The sex was recognized.

Table 10 shows the chemical compositions of the outer layer and the mandrel at the molten metal stage.

[0093]

[Table 10]

Table 11 shows the chemical composition of the outer layer of the roll cast with the composition shown in Table 10 above and the shaft core portion after solidification.

[0095]

[Table 11]

Table 1 shows the mechanical properties of the shaft core of the roll of the present invention in comparison with that of the conventional roll of the same size.
It is like 2.

[0097]

[Table 12]

Even in the rolls of the present invention having the compositions shown in Tables 10 and 11, by optimizing the alloy components forming the outer layer and limiting the carbide composition, segregation etc. will not occur even under the action of centrifugal force. In addition to using an outer layer material with uniform cracking resistance and crack resistance, the toughest ductile cast iron among cast iron materials is used for the shaft core material, and the outer layer material and the shaft core material are completely metallurgically combined to form one body. It can be a roll made by centrifugal casting.

[0099]

As described above, according to the present invention, by optimizing the alloying components forming the outer layer and limiting the carbide composition, wear resistance and crack resistance which do not cause segregation even under the action of centrifugal force. In addition to using a uniform outer layer material, the shaft core material uses the toughest ductile cast iron among cast iron-based materials,
It is possible to obtain a centrifugal casting roll in which the outer layer material and the shaft core material are completely metallurgically bonded together.

[Brief description of drawings]

FIG. 1 is a diagram showing the effect of the combined addition amount of V and Nb and the C amount on the hardness of a base material.

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

FIG. 3 is a diagram showing the influence of the combined addition amount of V and Nb and the C amount on the base metal hardness.

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

FIG. 5 is a hot wear ratio between the outer layer and the shaft core due to the carbide distribution of the centrifugally cast ring material, and the Nb and V content ratio Nb that affects the maximum crack depth in the thermal shock test.
It is a diagram which shows the influence of / V.

FIG. 6 is a hot wear ratio between the outer layer and the shaft core due to the carbide distribution of the centrifugally cast ring material, and the Nb and V content ratio Nb that affects the maximum crack depth in the thermal shock test.
It is a diagram which shows the influence of / V.

FIG. 7 is a hot wear ratio between the outer layer and the shaft core due to the carbide distribution of the centrifugally cast ring material, and the Nb and V content ratio Nb that affects the maximum crack depth in the thermal shock test.
It is a diagram which shows the influence of / V.

FIG. 8 is a hot wear ratio between the outer layer and the shaft core due to the carbide distribution of the centrifugally cast ring material, and the Nb and V content ratio Nb that affects the maximum crack depth in the thermal shock test.
It is a diagram which shows the influence of / V.

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication C22C 37/10 B 38/00 302 E 38/38 (72) Inventor Minoru Maeda Kawasaki, Handa, Aichi Prefecture 1-chome, Kawasaki Steel Co., Ltd., Chita Works (72) Inventor Yoshihiro Kataoka, 1 Kawasaki-machi, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.

Claims (5)

[Claims] 1. A centrifugal casting roll comprising an outer layer material and a shaft core material of ductile cast iron fused and integrated with the outer layer material, wherein the outer layer material is C: 1.0 to 3.5%, Si: 2.0%. Below, Mn: 2.0% or less, Cr: 12.0% or less, Mo: 8.0% or less, V: 3.0-
10.0%, Nb: 0.6-7.0%, balance Fe and unavoidable impurities, the shaft core material is 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
A roll made by centrifugal casting characterized by containing ˜2.0%, Cr: 1.5% or less, Mo: 1.0% or less, and the balance Fe and unavoidable impurities. 2. A centrifugal casting roll comprising an outer layer material and a shaft core material of ductile cast iron fused and integrated with the outer layer material, wherein the outer layer material is C: 1.0 to 3.5%, Si: 2.0%. Below, Mn: 2.0% or less, Cr: 12.0% or less, Mo: 8.0% or less, V: 3.0-
10.0%, Nb: 0.6 to 7.0%, Ni: 8.0% or less, C
o: Contains at least one selected from 10.0% or less,
The balance is Fe and unavoidable impurities, and 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
A roll made by centrifugal casting characterized by containing ˜2.0%, Cr: 1.5% or less, Mo: 1.0% or less, and the balance Fe and unavoidable impurities. 3. A centrifugal casting roll comprising an outer layer material and a shaft core material of ductile cast iron fused and integrated with the outer layer material, wherein the outer layer material is C: 1.0 to 3.5%, Si: 2.0%. Below, Mn: 2.0% or less, Cr: 12.0% or less, Mo: 8.0% or less, V: 3.0-
10.0%, Nb: 0.6 to 7.0%, Ni: 8.0% or less, C
o: 10.0% or less, Cu: 2.0% or less, Ti: 2.0% or less, Zr: 2.0% or less, W: 1.0% or less, B: 0.1% or less, and one or more kinds selected from them are contained. And the balance Fe and unavoidable impurities, and the axial 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
A roll made by centrifugal casting characterized by containing ˜2.0%, Cr: 1.5% or less, Mo: 1.0% or less, and the balance Fe and unavoidable impurities. 4. The centrifugally cast roll according to claim 1, wherein the outer layer material further satisfies the following formulas (1) and (2). V + 1.8 Nb ≤ 7.5 C-6.0% (1) 0.2 ≤ Nb / V ≤ 0.8 (2) 5. When manufacturing the centrifugally cast roll according to any one of claims 1 to 4, the outer layer mixing ratio to the shaft core is set to 5
A method for manufacturing a roll made by centrifugal casting, which is characterized in being regulated in the range of ~ 35%.