JP3358664B2 - Composite roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite roll for rolling steel or the like.

[0002]

2. Description of the Related Art A composite roll is formed by welding a solid inner layer (shaft core) formed of a tough material to an outer layer, which is a rolling use layer formed of a wear-resistant material, or an outer layer 1 shown in FIG. And an inner layer 2 with an intermediate layer 3 interposed. As shown in FIG. 2, the cylindrical roll is also called a sleeve roll, and is usually fixed to a roll shaft by shrink fitting or the like, assembled, and subjected to rolling. The intermediate layer 3
Is formed to prevent high alloying elements from being mixed into the inner layer 2 from the outer layer 1 when the outer layer 1 and the inner layer 2 are directly welded, and to prevent deterioration of the toughness of the inner layer.

Hitherto, as disclosed in JP-B-58-30382 and JP-B-61-16415, high chromium cast iron containing 10 to 25% of Cr has been known as an outer layer material having excellent wear resistance. Graphite-crystallized high chromium cast iron with improved seizure resistance is used.

[0004]

In recent years, rolling conditions have become severe, and higher wear resistance has been required.
For this reason, as mentioned in the above publication, one or two kinds of Nb and V are added to high chromium cast iron or graphite crystallization high chromium cast iron in total of 2% or less, and the fine carbides are generated as crystal nuclei. As a result, the structure is refined and densified, thereby improving the abrasion resistance. However, in reality, it cannot be said that the demand for improvement in wear resistance is sufficiently satisfied.

On the other hand, in order to greatly improve the wear resistance in steel rolling, it is considered that a large amount of W should be added to the material. However, since the outer layer of the composite roll is mainly cast by centrifugal casting, there is a problem that W separates due to a difference in specific gravity, segregation occurs in a circumferential direction, and it is difficult to obtain a uniform material. The present invention has been made in view of the above problems, and an object of the present invention is to provide a composite roll such as a steel roll having excellent wear resistance and an outer layer of a uniform material.

[0006]

According to the present invention, there is provided a composite roll comprising:
An outer layer formed of a wear-resistant cast iron material, an intermediate layer welded to the inner peripheral surface of the outer layer, and an inner layer welded to the inner peripheral surface of the intermediate layer. In the composite roll formed by casting , the outer layer has a chemical composition of 1.0 to 3.0% by weight, Si: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and Cr: 3.0 to 10.0% by weight. Mo: 0.1 to 9.0%; W: 1.5 to 10.0%; V, Nb: one or two of a total of 3.0 to 10.0%; B: 0.01 to 0.50%; and the balance substantially consisting of Fe. Chemical composition in weight%, C: 1.0-2.5%, Si: 0.2-3.0%, Mn: 0.2-1.5%, Ni: 4.0% or less, Cr: 4.0% or less, Mo: 4.0% or less, W, V , Nb, B in total of 12% or less, and the balance substantially consisting of Fe, and the inner layer is formed of flake graphite cast iron, spheroidal graphite cast iron or graphite steel. Characterized Rukoto (claim 1).

Further, the composite roll of the present invention comprises an outer layer formed of a wear-resistant cast iron material, an intermediate layer welded to the inner peripheral surface of the outer layer, and an inner layer welded to the inner peripheral surface of the intermediate layer. Become
In addition, in the composite roll in which the outer layer and the intermediate layer are centrifugally cast , the outer layer has a chemical composition by weight of C: 1.0 to 3.0%, Si: 0.1 to 2.0%, Mn: 0.1 to 2.0%, Cr. : 3.0 to 10.0%, Mo: 0.1 to 9.0%, W: 1.5 to 10.0%, V, Nb: 3.0 to 10.0% in total of one or two, Al, Ti, Zr: 0.01 to 0.50% each One or more kinds, B: 0.01 to 0.50% and the balance substantially consisting of Fe, wherein the intermediate layer has a chemical composition by weight%, C: 1.0 to 2.5%, Si: 0.2 to 3.0%, Mn: 0.2 1.5%, Ni: 4.0% or less, Cr: 4.0% or less, Mo: 4.0% or less, total of W, V, Nb, Al, Ti, Zr, B: 12% or less, and balance substantially consisting of Fe The inner layer is made of flaky graphite cast iron, spheroidal graphite cast iron or graphite steel (Claim 2) .

[0008]

The outer layer of the composite roll of the present invention is made of Cr, M
o, W, Nb, V, B, Fe and C, while Cr, M
o, W, V, Nb, Al, Ti, Zr, B, Fe and C are present in the matrix with a high-hardness composite carbide in the matrix, so that the hardness at ordinary and high temperatures is improved, and the wear resistance is improved. Improve dramatically. For this reason, in order to ensure the same life as conventional high chromium cast iron, etc., the outer layer thickness may be as thin as about 80 mm or less, that is, about 80% of the conventional thickness. The amount of outer layer material contained in a large amount can be reduced. Further, the outer layer is subjected to a quenching heat treatment to give high hardness, similarly to high chromium cast iron or the like. At this time, the outer layer material according to the present invention has a high hardness and a high residual stress as compared with a high chromium cast iron or the like.However, since the outer layer can be thinned, the residual stress can be suppressed low, and the accident resistance is improved. Can be improved. Also, the casting thickness is 80mm
Since it can be thinned to a degree or less, rapid solidification can be performed, macrosegregation is less likely to occur, and a microstructure is formed, thereby further improving wear resistance. On the other hand, even when the outer layer is formed to be thick, since the mass W is suppressed to 10% or less,
Even when the outer layer is formed by centrifugal casting, in which segregation is relatively easy to occur, macro segregation is unlikely to occur, and the uniformity of the structure is excellent.

In the composite roll of the present invention , since the intermediate layer is formed between the outer layer and the inner layer by the high-carbon cast steel having a specific composition, the high alloy component of the outer layer is mixed into the inner layer to deteriorate the toughness. Can be prevented. Further, since the boundary between the intermediate layer and the inner layer is made of a low alloy, the formation of a carbide layer is suppressed, and the boundary strength can be improved. In addition, during the austenite heat treatment of the outer layer, it is possible to prevent the temperature of the inner layer from rising, while preventing the toughness of the inner layer material from deteriorating.
Only the outer layer can be heated to a high temperature of 1100 ° C. or higher.
In the intermediate layer composition of the present invention, martensitic transformation does not occur or hardly occurs when the outer layer is quenched.
Therefore, even if the outer layer is subjected to a quenching heat treatment, no excessive residual stress is generated, and the accident resistance is excellent.

Further, since the inner layer is formed of flaky graphite cast iron, spheroidal graphite cast iron or graphite steel, that is, a steel material in which graphite is crystallized, the Young's modulus can be reduced to about 19,000 kg / mm ² or less. The flattening of the roll absorbs the load and improves the accident resistance. Further, the residual stress at the time of heat treatment of the outer layer can be reduced by the low-temperature strain relief annealing. In addition, it has excellent heat conductivity and heat dissipation, and can prevent thermal deformation of the roll during rolling. In addition, since it has good toughness, it can withstand a shocking rolling torque.

[0011]

First, the reasons for limiting the chemical composition of the wear-resistant cast iron used for the outer layer of the composite roll of the present invention will be described. Hereinafter, all units of the components are% by weight. C: 1.0 to 3.0% C mainly combines with Fe and Cr to form an M ₇ C ₃ type high-hardness composite carbide, and Cr, Mo, V, N
Combined with b and W, it also forms high hardness composite carbides such as MC type, M ₆ C type and M ₂ C type. In order to form this high hardness composite carbide, C% of 1.0% or more is required. Meanwhile, 3.0
%, The amount of carbides increases and the material becomes brittle and the crack resistance deteriorates. Therefore, the content of C is set to 3.0% or less. Si: 0.1-2.0% Si is an element necessary for securing the flowability of the molten metal because the material of the present invention is a cast alloy.
About 0.1% is inevitably contained. However, if it exceeds 2.0%, the toughness is reduced, which is not preferable. Mn: 0.1 to 2.0% Mn increases the hardening ability and combines with S to form MnS, preventing embrittlement due to S. At the same time, about 0.1% is unavoidably contained from the raw materials used. . However, if it exceeds 2.0%, the toughness is reduced, which is not preferable. Cr: 3.0-10.0% Cr combines with C together with Fe, Mo, V, Nb, and W,
It forms high hardness composite carbides and contributes to improvement of wear resistance at high temperatures. In addition, a part of the alloy dissolves in the matrix to improve quenchability and wear resistance. If it is less than 3.0%, these effects are small, and improvement in wear resistance cannot be expected. On the other hand, 10.0
%, It is not preferable because toughness is deteriorated. Mo: 0.1 ~9.0% Mo is Fe, Cr, V, Nb, and readily bind with C together with W, formed mainly M ₇ C ₃ type M ₆ C-type, the M ₂ C type composite carbide, room temperature and high temperature Increases hardness and contributes to improvement of wear resistance. Mo exerts its effect when added in a small amount compared to W. At this time, if it is less than 0.1%, the desired wear resistance cannot be obtained, while if it exceeds 9.0%, the toughness decreases, which is not preferable. W: 1.5 to 10.0% Similarly, W easily combines with C together with Fe, Cr, Mo, V, and Nb to form a composite carbide, and increases the hardness at ordinary and high temperatures to contribute to the improvement of wear resistance. If it is less than 1.5%, the desired wear resistance cannot be obtained, while if it exceeds 10.0%, the toughness decreases and the heat crack resistance deteriorates. In addition, at the time of centrifugal casting, macro segregation is easily generated. Therefore, the content is set to 10.0% or less. V, Nb: 3.0 to 10.0% in total of one or two kinds V, like Nb, easily combines with C together with Fe, Cr, Mo, and W to form mainly MC type composite carbide, and at room temperature and high temperature Increases hardness and contributes to improvement of wear resistance.
Further, since the MC-type composite carbide is formed in a branch shape in the thickness direction, it suppresses plastic deformation of the matrix and contributes to improvement of mechanical properties and crack resistance. Such an effect is unlikely to appear unless one or more of the two are added and 3.0% or more is added. However, if the addition amount exceeds 10.0%, the toughness is reduced, and at the time of centrifugal casting, macro segregation is easily generated. Therefore, the content is set to 10.0% or less. B: 0.01 to 0.50% B combines with oxygen in the molten metal and exhibits a deoxidizing effect. In addition, the effect of refining the solidification structure with the generated oxide as the nucleus,
And the effect of increasing the hardenability by B dissolved in the matrix. In the case of a casting having a large mass such as a rolling roll, it may be difficult to increase the cooling temperature, but it is easy to obtain a quenched structure due to an increase in hardenability. If it is less than 0.01, such an effect is not sufficient, while if it exceeds 0.50%, the material becomes brittle, which is not preferable.

The wear-resistant cast iron material of the outer layer according to the present invention includes, in addition to the above alloy components, Al, Ti, Zr having the following composition range.
And those containing one or more of the above. Al, Ti, Zr: 0.01 to 0.50% each Al, Ti, and Zr generate oxides in the molten metal, reduce the oxygen content in the molten metal, improve the soundness of the product, and generate the oxides. Acts as a crystal nucleus, which is effective in refining the solidified structure. If it is less than 0.01%, this effect is not sufficient. On the other hand, if it exceeds 0.50%, it remains as inclusions and is not preferable. In addition, Al, Ti,
In the present invention, Zr is mainly added for the purpose of improving wear resistance by making the casting structure finer, and is not simply added for the purpose of degassing.

The wear-resistant cast iron material of the outer layer of the present invention is formed of the above alloy components and the balance of Fe and impurities. still,
P and S are inevitably mixed in from the raw materials, but are preferably as small as possible because they make the material brittle. P: 0.2% or less, S: 0.1%
It is better to stop below. Next, the inner layer material of the composite roll of the present invention will be described. As the inner layer material, a material in which graphite is crystallized for the following reason, specifically, flaky graphite cast iron (F
C), spheroidal graphite cast iron (abbreviated as DCI), and graphite steel (abbreviated as SGS). Reason for using graphite crystallized material When rolling is used, the occurrence of overload condition (for example, biting of two plates) is inevitable, but the Young's modulus of the outer layer material is 21000.
Since it is as high as 223000 kg / mm ² , a large stress is generated in the outer layer material. Young's modulus of the middle layer is 20000-23000kgf / mm
² , but because the layer thickness is relatively thin, about 25-30 mm,
If the Young's modulus of the inner layer material to be composited is low, the load can be absorbed by the inner layer material by flattening the roll at the time of overload.

Therefore, lowering the Young's modulus of the inner layer material increases safety during use. In order to obtain a Young's modulus of less than 20000 kg / mm ² , the inner layer material must be crystallized graphite. Because the outer layer material contains a special alloy and is hardened by tempering secondary hardening,
Generally, the material is difficult to remove the residual stress. For this reason, when the outer layer material is cured and heat-treated on the composite roll, a compression stress is generated in the outer layer and a tensile stress is generated in the inner layer due to expansion due to transformation of the outer layer material. If the tensile stress of the inner layer material becomes excessive, breakage of the inner layer and breakage at the boundary between the intermediate layer and the inner layer occur, leading to roll breakage.

To prevent breakage, the composite roll may be subjected to strain relief annealing to release the residual stress of the inner layer material. However, high-temperature strain relief annealing exceeding 600 ° C. causes a decrease in hardness of the outer layer. Therefore, it is necessary to release the residual stress of the inner layer material by low-temperature strain relief annealing. For this purpose, the inner layer material is preferably made of graphite crystallized. In the case of the present invention, the purpose of low-temperature strain relief annealing can be achieved by tempering heat treatment of the outer layer. The roll is rolled material (1000
(Around ℃). In order to prevent thermal deformation of the roll and maintain a predetermined shape, the heat radiation must be good. Therefore, the inner layer must have good heat conduction. Therefore, a graphite crystallized material is suitable as the inner layer material. The neck of the roll must be strong enough to withstand the bending force and motor torque. Since there are shocking loads, toughness is important as well as strength. By crystallizing graphite, the toughness can be improved.

Next, the characteristics and preferred compositions (unit: wt%) of various inner layer materials forming the inner layer of the composite roll will be described. As described above, the inner layer needs to contain graphite, but when the outer layer and the inner layer are welded, mixing of the high alloy component of the outer layer necessarily occurs. It is necessary to determine the composition in consideration of this point. (1) In the case of FC FC has good castability and Young's modulus of 10,000 to 15,000 kg /
Since it is as low as ² mm2 and the form of graphite is flaky, it is easy to remove residual stress and has high thermal conductivity. Also, the workability is good, and when used as the inner layer material of the hollow roll, the inner surface processing is easy. However, since the strength is limited to about 30 kg / mm ² , it is not suitable for a composite roll used under a condition of a large rolling load. The solid phase line of FC having the following composition is 1130
~ 1170 ° C.

Preferred examples of the composition and reasons for the limitation are shown below. C: 2.5 to 4.0% C is necessary for crystallizing graphite, and if less than 2.5%, the amount of graphite is small. On the other hand, if it exceeds 4.0%, the amount of graphite becomes excessive and the strength decreases. Si: 0.8 to 2.5% Si acts to promote crystallization of graphite, and if it is less than 0.8%, graphitization is insufficient. On the other hand, if it exceeds 2.5%, the base becomes brittle.

Mn: 0.2-1.5% Mn has the effect of strengthening the matrix and preventing harm of S. 0.2
%, The effect can hardly be expected. on the other hand,
If it exceeds 1.5%, the material becomes brittle. P, S: each 0.2% or less P and S are impurities, and therefore the smaller the better, the better. Since the low-concentration one is expensive, the content of about 0.01% or more will be unavoidable in consideration of economy.

Ni: 3.0% or less Ni is effective for graphitization and strengthening the matrix.
%, The untransformed structure tends to remain and the strength is deteriorated. Cr and Mo: 2.0% or less each Cr and Mo have a strengthening effect on the matrix, but too much inhibits graphitization. To strengthen the base, it is desirable to contain 0.1% or more. On the other hand, in order to prevent the inhibition of graphitization, it is necessary to keep the content to 2.0% or less, including the amount mixed from the outer layer.

The total of W, V and Nb is 4.0% or less. These elements are inevitably mixed from the outer layer. W, V, N
b has no effect of improving the inner layer material. Therefore, these elements are interpreted as impurities and are allowed up to 4% as long as the mechanical properties of the inner layer material are not deteriorated. In addition, A
Since l, Ti, Zr, and B are contained, these elements are inevitably mixed into the inner layer via the intermediate layer, but are trace amounts, so that there is almost no problem in the material. FC is substantially formed of Fe in addition to the above components. The composition range of the molten metal before welding to the intermediate layer, that is, before casting is shown below. The molten metal composition is such that the inner layer composition after welding,
The amount is determined in consideration of the amount of components mixed in from the intermediate layer.

C: 2.5 to 4.0%, Si: 0.8 to 2.5%, Mn: 0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less, Mo: 2.0% or less, balance substantially in the case of Fe (2) DCI DCI has good castability and Young's modulus of 15,000 to 19000 kg
/ Mm ² and a large amount of graphite. Furthermore, since the form of the graphite is spherical unlike FC, it has excellent strength and toughness. Also, the workability is good. Therefore, it is suitable as an inner layer material. As disclosed in JP-B-59-52930 and JP-B-59-52931, after heating and holding in the ferrite-austenite coexisting temperature range (780 to 900 ° C), quenching is performed at 200 to 800 ° C / Hr. Then, the base structure becomes a two-phase mixed structure of ferrite and pearlite by the heat treatment for turning austenite into fine pearlite. This structure is particularly excellent in crack propagation and residual stress removing effect.
The heat treatment for forming the two-phase mixed structure may be performed as a heat treatment before the heat treatment for curing the outer layer of the composite roll. The solidus of DCI having the following composition is 1130 to 1170 ° C.

Preferred examples of the composition and the reasons for limitation are shown below. C: 2.5 to 4.0%, Si: 1.3 to 3.5%, Mn: 0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less, Mo: 2.0% or less , W, V, Nb: 4% or less in total, Mg: 0.02-0.1
%, The balance is essentially the reason for limiting the components other than FeSi and Mg to FC
Therefore, these two components will be described.

Si is a graphitization promoting element. DCI contains Mg for spheroidizing graphite. Since Mg is a strong graphitization inhibiting element, 1.3% or more of Si is required to achieve graphitization in the presence of Mg. On the other hand, if it exceeds 3.5%, the matrix becomes brittle, a large amount of ferrite is precipitated, and the strength decreases. Mg has a function of spheroidizing graphite. To obtain the effect, 0.02% or more is required. On the other hand, if it exceeds 0.1%, graphitization is inhibited and casting defects are easily generated.

A preferred melt composition of DCI before welding to the outer layer is shown below. C: 2.5 to 4.0%, Si: 1.3 to 3.5%, Mn: 0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less, Mo: 2.0% or less Mg: 0.02 to 0.1%, balance substantially in the case of Fe (3) SGS SGS has a high Young's modulus of 17,000 to 20,000 kg / mm ² and a small amount of graphite, so that residual stress is relatively difficult to remove. Further, the castability is not very good, and a large feeder or the like is required. However, it has excellent strength of 40 kg / mm ² or more and is excellent in toughness, so it is most suitable for rolls used under severe operating conditions in which a large bender load is applied. In addition, the solidus line (in the case of SGS having the following composition) is 1
Since the temperature is 170 to 1250 ° C., which is higher than FC and DCI, there is an advantage that the outer layer hardly deteriorates in the heat treatment for austenitizing.

Preferred examples of the composition and reasons for the limitation are shown below. C: 1.0 to 2.3%, Si: 0.5 to 3.0%, Mn: 0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less, Mo: 2.0% or less , W, V, and Nb are 4.0% or less in total, and the balance is substantially the same as that of FC except for Fe C and Si. Therefore, these two components will be described.

C is necessary for crystallizing graphite.
If it is less than 1.0%, crystallization of graphite hardly occurs. Meanwhile, 2.3%
If it exceeds, the graphite shape is broken and the strength is reduced. Si is necessary for graphitization. If it is less than 0.5%, crystallization of graphite becomes difficult, while if it exceeds 3.0%, the matrix becomes brittle.
A preferred melt composition of SGS before welding to the outer layer is exemplified below. C: 1.0 to 2.3%, Si: 0.5 to 3.0%, Mn: 0.2 to 1.5%, P: 0.2% or less, S: 0.2% or less, Ni: 3.0% or less, Cr: 2.0% or less, Mo: 2.0% or less Next, the intermediate layer will be described. The intermediate layer is formed for the purpose of reducing the mixing of the alloy component of the outer layer into the inner layer.
A strength of about mm ² or more is required. If the strength is insufficient,
The boundary between the outer layer and the intermediate layer breaks, and the outer layer peels off. Therefore, the intermediate layer needs to be made of a material having high strength even if a large amount of alloy components are mixed in from the outer layer. For this reason, a high carbon cast steel (abbreviated as AD) having the following composition is suitable as the intermediate layer material. Hereinafter, the composition of the intermediate layer material according to the present invention and the reasons for limitation will be described. C: 1.0 to 2.5% C contributes to strength improvement, but if it is less than 1.0%, the freezing point increases, and welding tends to be insufficient. On the other hand, if it exceeds 2.5%, the amount of carbide becomes excessive and the material becomes brittle. Si: 0.2 to 3.0% Si has a function of accelerating degassing and a function of improving flowability of molten metal.
If it is less than 0.2%, such effects cannot be expected, while 3.0%
If it exceeds, the material becomes brittle. In the high Si region, crystallization of graphite may be observed depending on the Ni content, but there is no problem with the material. Mn: 0.2 to 1.5% Mn is limited to the above range for the same reason as the ductile cast iron as the inner layer material. Ni: 4.0% or less Ni has the effect of strengthening the material. However, when the content exceeds 4.0%, the effect is saturated and an untransformed structure is apt to be generated, and the strength is deteriorated. Cr and Mo: 4.0% or less each Cr and Mo have an effect of strengthening the material. But 4.0
%, The mechanical properties deteriorate rather.

W, V, Nb, B: 12% or less in total, W, V, Nb, B, Al, Ti, Zr: 12% or less in total These elements have little effect on improving the material of the intermediate layer. However, contamination from the outer layer is inevitable. Up to 12% is allowed as long as the mechanical properties of the intermediate layer material are not deteriorated. In addition, W, V, Nb, B or W, V, N
b, Al, Ti, Zr, because it contains B, these elements coming inevitably into the intermediate layer. In addition to the components described above, the remainder of the intermediate layer material is substantially formed of Fe. still,
P and S are impurities and are preferably as small as possible because they make the material brittle. In the present invention, as in the case of the inner layer material, both are 0.2%
It is better to stop below.

The composition of the molten metal before welding to the outer layer is determined in consideration of the amount of components mixed in from the outer layer so that the composition of the molten metal becomes the composition of the intermediate layer after welding. In the present invention, since an intermediate layer of 1.0 to 2.5% C is provided between the outer layer and the inner layer (axial portion), it is possible to prevent harmful alloy elements from directly mixing into the inner layer from the outer layer to the inner layer during welding. In addition to significant suppression, the following effects are obtained. During the quenching heat treatment of the outer layer, it is better to heat the outer layer to 1100 ° C or more for austenitizing heat treatment, but even if the outer layer is heated to 1100 ° C or more, heat transfer to the inner layer is performed through the intermediate layer. By adjusting the amount of heat, the temperature of the inner layer can be easily suppressed to 1100 ° C. or lower, and the inner layer can be prevented from being melted.

The intermediate layer is made of Cr, M by welding with the outer layer.
Although the concentrations of o, W, and V are high, these elements are still kept lower than the outer layer, so that the outer layer and the intermediate layer are welded more than when the outer layer and the inner layer are directly welded. Welding the inner layer can lower the alloy concentration at the welded portion of the inner layer. Therefore, when the intermediate layer is provided, a carbide layer is not easily formed at the boundary with the inner layer, and the boundary strength can be improved. Composite roll of the present invention, when a solid-like roll, after the outer layer and the intermediate layer is cast centrifugal force, the inner layer (axial center) is left cast therein. In the case of a sleeve roll, the inner layer is also centrifugally cast following the outer layer and the intermediate layer.

FIG. 3 shows a horizontal centrifugal casting apparatus.
The centrifugal casting mold 4 is rotatably supported by rotating rollers 5, 5, and the molten metal is cast into the mold 4 from the dam 6 via a pouring gutter 7. Numeral 8 denotes a sand mold for hot water. To cast a solid composite roll, first, the molten outer layer material is cast into a rotating mold 4, and after it is solidified, the molten intermediate layer material is cast on the inner peripheral surface of the outer layer 1, and the intermediate layer 3 is melted. Is centrifugally cast. Thereafter, a mold 4 having an outer layer 1 and an intermediate layer 3 therein.
The upper mold and the lower mold for forming the shaft core are connected to each other to form a stationary mold, and the inner layer material melt may be cast therein. In the horizontal centrifugal casting apparatus, since each part of the molten metal cast in the mold moves up and down every time the mold rotates, there is a variation in G, and vibration is caused by eccentricity and scratches of the rollers and the mold. It is easy to occur and the components in the cast outer layer material melt are easy to move. For this reason, when casting a thick outer layer, segregation is likely to occur due to the movement of the components. Therefore, it is usually preferable to cast at a relatively low temperature at a solidification start temperature of about + 70 ° C. or less. However, since the outer layer material according to the present invention is a highly wear-resistant material, it is hard to be worn, and the outer layer may be relatively thin, and is rapidly cooled by a mold until the casting thickness is about 80 mm (preferably 55 to 70 mm). Therefore, there is almost no risk of segregation even if the casting is performed at a temperature higher than the above temperature. The thickness of the outer layer of the product is 50 mm considering the melting allowance of the intermediate layer of 20 mm and the processing allowance of 10 mm.
(Preferably 25 to 40 mm).

FIG. 4 shows a vertical centrifugal casting apparatus.
An upper mold 12 and a lower mold 13 are assembled at the upper and lower ends of a centrifugal casting mold 11, and the mold is mechanically fixed concentrically to a rotating base 14. For this reason, the outer layer material molten metal 16 cast into the mold through the weir 15 and ascended and adhered to the inner surface of the mold 11 by the action of centrifugal force is less susceptible to fluctuations in G and vibration. Therefore, if vertical centrifugal casting is used, segregation is unlikely to occur even when casting a thick outer layer, so that casting can be performed at a higher temperature, which is effective in improving workability and preventing casting defects due to inclusion of foreign matter. It is. It is needless to say that only the centrifugal force casting mold 11 is fixed to the base 14, and after the outer layer and the intermediate layer are cast, the upper mold and the lower mold are assembled, and the shaft core portion is cast by standing.

The composite roll of the present invention, after casting as an outer layer of the roll, cools the entire roll from a quenching temperature (austenitizing temperature) to a temperature range of 400 to 650 ° C. by 150 ° C./hr.
By quenching at the above cooling rate, a good quenched structure can be obtained. Tempering may be performed once or several times at a temperature of 500 to 600 ° C. The outer layer material according to the present invention,
Mo, which dissolved in the matrix during the austenitizing heat treatment,
W, V, Nb, etc. are precipitated as fine carbides by the tempering heat treatment and cause a tempering secondary hardening phenomenon, so that they have excellent high-temperature hardness.

The composite roll of the present invention may be any of hot rolled and cold rolled rolls, such as a roll for rolling equipment and a pinch roll for ancillary equipment or a roller for conveying rolled material.
Applied to rolls and rollers that require abrasion resistance.
The rolled material includes not only steel and non-ferrous metals but also non-metals. Next, specific examples of the present invention will be described. (1) The melt of the outer layer material shown in Table 1 is centrifugally cast into a centrifugal casting mold having an inner diameter of φ810 mm, and after the outer layer is completely solidified, the melt of the intermediate layer shown in the table is centrifugally cast. And the intermediate layer were welded. Casting thickness is outer layer 65mm, middle layer 30mm
And Examples are samples No. 1 and No. 2, and the outer layer material of No. 3 conventional example is a high chromium cast iron material having improved wear resistance. The composition unit in the table is% by weight, and the balance is substantially Fe. (2) Wait until the intermediate layer is completely solidified, stop the rotation of the mold, stand the mold with the outer layer and the intermediate layer inside vertically, and connect the upper mold and lower mold at both ends. The inner layer material (shaft core material) shown in the same table was also cast into the interior.

[0034]

[Table 1]

(3) After the cast composite roll is roughly processed, the roll of the embodiment is uniformly preheated to 600 ° C., and then the rolls are horizontally opposed to each other as shown in FIG. It was rotatably supported between gas burners 21 arranged in parallel at a pitch of 250 mm along the axial direction, and the surface of the outer layer was heated while rotating the rolls. Outer layer surface temperature is 1165
Heating was stopped when the temperature in the center of the inner layer reached 870 ° C. The time required for heating was 250 minutes. From the heat conduction temperature data, in this case, the temperature near the inner peripheral surface was estimated to be 970 ° C. On the other hand, with respect to a conventional roll, the entire roll was kept at 1050 ° C. for 5 hours to austenite. (4) For the rolls of the embodiment and the conventional example,
After stopping the heating, spray water cooling was immediately performed, and the roll surface temperature was rapidly cooled to 500 ° C., and then allowed to cool to room temperature. Then 5
The tempering heat treatment maintained at 50 ° C. for 20 hours was repeated twice.
The outer layer surface hardness after the heat treatment was as shown in Table 2 below.
From the table, it can be seen that the outer layer of the example has remarkably improved hardness and excellent abrasion resistance as compared with that of the conventional example. When the oxidation state of the outer layer surface was observed, the thickness of the oxide layer was about 0.5 mm in the example,
In the conventional example, it was remarkably about 3.0 mm.

[0036]

[Table 2]

(5) After finishing the body surface, the welding condition was confirmed by an ultrasonic flaw detection test. As a result, the welding was good for all rolls. Next, the roll body was cut, and the outer layer cross section was visually observed .
No segregation of components was observed in any of the rolls Nos. 1 and 2 . Table 3 shows the results of analyzing the components at the center of the thickness of the intermediate layer and at the center of the inner layer (axial portion).
From the table, it can be seen that the mixing amount of the outer layer high alloy component in the inner layer is extremely small in both the example and the conventional example.

[0038]

[Table 3]

(6) Table 4 shows the results of taking tensile test specimens from the inner layer of each sample and conducting a tensile test. From the same table, it can be seen that No. 1 and No. 2 of the example in which the inner layer is DCI have higher strength than No. 3 of the conventional example, and the conventional example has about 20% deterioration compared to the example. Is recognized.

[0040]

[Table 4]

[0041]

As described above, in the composite roll of the present invention, the outer layer is formed of Cr, Mo, W, V, Nb, B or C.
Since it is formed of a special cast iron material containing a predetermined amount of r, Mo, W, V, Nb, Al, Ti, Zr, and B , the presence of these high-hardness composite carbides dramatically improves wear resistance. And macro segregation hardly occurs during casting. In addition, since the intermediate layer was formed from a high-carbon cast steel of a specific composition, the incorporation of high alloy components from the outer layer to the inner layer can be significantly reduced, the boundary strength can be improved, and martensitic transformation does not occur. , Little if any
Since it is possible to prevent the inner layer of the melting and strength reduction during austenitizing heat treatment further outer layer without increasing the residual stress. In addition, since the inner layer is made of flake graphite cast iron, spheroidal graphite cast iron or graphite steel, the strength and toughness are good, and the Young's modulus can be considerably lower than that of the outer layer. It is possible to prevent excessive stress from being generated, and it is excellent in safety and accident resistance. Furthermore, since it is excellent in heat dissipation, thermal deformation hardly occurs.

[Brief description of the drawings]

FIG. 1 is a sectional view of a solid composite roll according to the present invention.

FIG. 2 is a sectional view of a sleeve-shaped composite roll according to the present invention.

FIG. 3 is a sectional view of a main part of a horizontal centrifugal casting apparatus.

FIG. 4 is a sectional view of a main part of a vertical centrifugal casting apparatus.

FIG. 5 is a cross-sectional view showing a composite roll outer layer heating state.

[Explanation of symbols]

 1 outer layer 2 inner layer 3 middle layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Okabayashi 64, Nishimukaijima-cho, Amagasaki City, Hyogo Prefecture, Kubota Amagasaki Plant (72) Inventor Hiroyuki Kimura 64, Nishimujimajima-cho, Amagasaki City, Hyogo Prefecture, Kubota Amagasaki Plant ( 72) Inventor Takashi Shikata 64 Nishimukaijima-cho, Amagasaki City, Hyogo Prefecture Inside Kubota Amagasaki Plant (56) References JP-A-2-25205 (JP, A) JP-A-57-57862 (JP, A) JP-A Sho 64-5609 (JP, A) JP-A-59-178110 (JP, A) JP-A-57-100809 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 37/00 -37/10 B21B 27/00

Claims (2)

(57) [Claims] [1 claim] and outer layer formed of a wear cast iron, an intermediate layer deposited on the inner peripheral surface of the outer layer consists of a lining which is welded to the inner circumferential surface of the intermediate layer, and the and the outer layer Middle layer is far
In the composite roll formed by centrifugal force casting , the outer layer has a chemical composition by weight of C: 1.0 to 3.0%, Si: 0.1 to 2.0%, Mn: 0.1 to 2.0%, Cr: 3.0 to 10.0%, Mo: 0.1 to 9.0%, W: 1.5 to 10.0%, V, Nb: one or two of a total of 3.0 to 10.0%, B: 0.01 to 0.50% and the balance substantially consisting of Fe. % By weight, C: 1.0 to 2.5%, Si: 0.2 to 3.0%, Mn: 0.2 to 1.5%, Ni: 4.0% or less, Cr: 4.0% or less, Mo: 4.0% or less, W, V, Nb, B. A composite roll comprising a total of B of 12% or less and a balance substantially of Fe, wherein the inner layer is formed of flake graphite cast iron, spheroidal graphite cast iron or graphite steel. Wherein the outer layer formed of a wear cast iron, Ri Do from an intermediate layer deposited on the inner peripheral surface of the outer layer, the welded inner layer on the inner peripheral surface of the intermediate layer, and the outer layer And the middle layer is far
In the composite roll formed by centrifugal force casting , the outer layer has a chemical composition by weight of C: 1.0 to 3.0%, Si: 0.1 to 2.0%, Mn: 0.1 to 2.0%, Cr: 3.0 to 10.0%, Mo: 0.1 to 9.0%, W: 1.5 to 10.0%, V, Nb: 3.0 to 10.0% in total of one or two kinds, Al, Ti, Zr: one or more of 0.01 to 0.50% each, B: 0.01 to 0.50% and the balance substantially consisting of Fe. The chemical composition of the intermediate layer is% by weight, C: 1.0 to 2.5%, Si: 0.2 to 3.0%, Mn: 0.2 to 1.5%, Ni: 4.0%. In the following, Cr: 4.0% or less, Mo: 4.0% or less, W, V, Nb, Al, Ti, Zr, B in total 12% or less, and the balance substantially consisting of Fe, wherein the inner layer is flake graphite cast iron. , A composite roll formed of spheroidal graphite cast iron or graphite steel.