JPH0669577B2 - Composite sleeve for rolling roll and method of manufacturing the same - Google Patents

Description

The present invention relates to a composite sleeve for rolling rolls used in hot rolling, cold rolling, etc., and a method for producing the same.

[Prior Art] In recent years, rolling technology has advanced with the goal of continuous hot rolling, productivity improvement, quality improvement, etc., and along with that, rolling rolls are often used under severe conditions and various improvements have been made. Has been done. In addition, the quality requirements for rolled products have become higher, and the quality requirements for rolling rolls have become more stringent.

Therefore, conventionally, there have been proposed techniques for studying the material of the rolling roll, adopting a composite sleeve for strengthening the rolling roll, and further strengthening the inner layer of the composite sleeve. For example, Japanese Patent Publication Nos. 59-11657 and 5
9-20417, Japanese Patent Publication No. 55-158808, Japanese Patent Publication No. 60-261610 and the like have proposed techniques for an inner layer toughened composite sleeve. In these conventional composite sleeves, when the outer layer is made of ductile cast iron or nickel grain cast iron, as its inner layer material, in order to ensure soundness in the vicinity of the inner and outer layer boundaries,
Cast iron-based materials such as ordinary cast iron and ductile cast iron will be used.

According to the above-described conventional composite roll sleeve, since the outer layer material is made of the cast iron material, the wear resistance and seizure resistance required for the outer layer can be secured.

However, in the above-described conventional rolling roll composite sleeve, when the outer layer material is a cast iron-based material, the inner layer material is also a cast iron-based material for the above-mentioned reason, so it is difficult to secure high toughness in the inner layer. There is. Here, in the composite sleeve, rolling load, thermal stress during rolling, and residual stress associated with sleeve production act on the inner layer as tensile stress, so the inner layer material must be tough enough to withstand the inner layer tensile stress. It Therefore, when the conventional composite sleeve is subjected to high load rolling, if the inner layer material is made of cast iron-based material such as ordinary cast iron or ductile cast iron, there is a concern about the toughness of the inner layer.

However, JP-A-58-55552 discloses a composite sleeve in which the outer layer material is high chromium cast iron, the inner layer material is spheroidal graphite steel, and the intermediate layer is interposed between the outer layer material and the inner layer material.
Here, the intermediate layer is provided in order to prevent Cr in the high chromium outer layer material from mixing and diffusing at the time of casting the inner layer material and deteriorating the toughness of the inner layer material due to the high Cr content.
According to this composite sleeve, since the outer layer material is made of a cast iron material, the wear resistance and seizure resistance required for the outer layer can be secured. Further, since the inner layer material is formed of spheroidal graphite steel, it is possible to secure a certain degree of toughness in the inner layer.

[Problems to be Solved by the Invention] However, in the above-described conventional rolling roll composite sleeve, even if the outer layer material is made of cast iron-based material and the inner layer material is made of spheroidal graphite steel, the intermediate layer Is provided,
Since the volume of the intermediate layer is relatively small, the mixing ratio of the outer layer material into the intermediate layer becomes excessively large, and the toughness of the intermediate layer is greatly impaired. Therefore, in a horizontal sleeve roll for H-shaped steel rolling and the like, it is difficult to secure a certain roll strength due to the strength deterioration of the intermediate layer between the inner and outer layers. Therefore,
In the prior art, there is a limit in providing a composite sleeve having higher inner / outer layer boundary strength and inner layer strength, which is required in accordance with severer rolling conditions.

It is an object of the present invention to provide a composite sleeve for a rolling roll which has excellent wear resistance and seizure resistance for the outer layer and excellent toughness for the inner layer while ensuring the soundness in the vicinity of the boundary between the inner and outer layers. .

[Means for Solving the Problems] The rolling roll composite sleeve according to the present invention is a rolling roll composite sleeve in which the inner layer material and the outer layer material are different from each other, and the inner layer material is spherical graphite steel and the outer layer material is Ductile cast iron or nickel grain cast iron, the outer layer material is mixed and welded into the inner layer, and the outer layer material mixture ratio of the outer layer material weight mixed in the inner layer to the total inner layer molten metal weight is as follows: It is a composite sleeve for rolling rolls as described above.

Mixing rate when outer layer material is ductile cast iron and inner layer material is spheroidal graphite steel: 10-40% Mixing rate when outer layer material is nickel-glen cast iron and inner layer material is spheroidal graphite steel: 10-40% The method for manufacturing such a composite sleeve for a rolling roll,
In a method for manufacturing a rolling roll composite sleeve in which the outer layer molten metal is cast by centrifugal casting and then the inner layer molten metal is cast, the outer layer molten metal is ductile cast iron or nickel grain cast iron, and the outer layer molten metal is cast to form an outer shell layer. After that, the inner layer molten metal is made of spheroidal graphite steel, and when the inner layer molten metal is cast, a predetermined amount of the outer shell layer inner surface is melted by the inner layer molten metal, and the outer layer material is mixed in the inner layer by a manufacturing method for fusion-bonding. According to the present invention, there is provided a method of manufacturing a composite sleeve for a rolling roll, in which the mixing ratio of the outer layer material mixed with the inner layer relative to the total weight of the inner layer molten metal is as follows.

Mixing ratio when outer layer material is ductile cast iron and inner layer material is spheroidal graphite steel: 10-40% Mixing rate when outer layer material is nickel glen cast iron and inner layer material is spheroidal graphite steel: 10-40% [Action] The present inventors, when adopting spheroidal graphite steel as the inner layer material,
Even if the alloy components (Cr, Ni, etc.) of the outer layer material are mixed in the inner layer material,
Since the volume of the inner layer material is relatively large, the mixing ratio of the outer layer material to the inner layer can be set to a relatively low value of 10 to 40%, and as a result, the strength of the spheroidal graphite steel of the inner layer is hardly reduced. Found.

Therefore, the present inventor deliberately removed the intermediate layer which was provided in the prior art to prevent the mixture of the components of the outer layer material into the inner layer material, and when the intermediate layer was provided, the volume of the intermediate layer was relatively small. Therefore, the mixing ratio of the outer layer material to the middle layer becomes excessive,
As a result, it was decided to solve the problem of roll strength reduction due to a large loss of the toughness of the intermediate layer between the inner layer and the outer layer in a horizontal sleeve roll for H-shaped steel rolling or the like.

Therefore, the fact that the intermediate layer is not provided in the present invention is not based on the fact that it is not necessary to prevent the diffusion of the Cr content in the outer layer material into the inner layer material, and eliminates the harmful effects of providing the intermediate layer. It is based on new knowledge that it is necessary to do so and that the mixing ratio of the outer layer material to the inner layer can be suppressed to be low without providing the intermediate layer.

On the other hand, in the present invention, the outer layer material of ductile cast iron (solidification start temperature 1220 ° C, solidification end temperature 1100 ° C), nickel glen cast iron (solidification start temperature 1250 ° C, solidification end temperature 1100 ° C),
Spheroidal graphite steel (solidification start temperature 1420 ℃, solidification end temperature 1320
C.), the solidification start temperature and the solidification end temperature are as high as about 200 ° C., and the solidification start temperature of the inner layer material is higher than that of the inner layer material, so simply omitting the intermediate layer from the above, As shown in FIG. 1, a phenomenon was observed that contractions were likely to occur at the boundary between the inner and outer layers.

Therefore, when manufacturing the composite sleeve for a rolling roll of the present invention, when the inner layer molten metal made of spheroidal graphite steel is cast into the outer layer formed by solidification of ductile cast iron or nickel grain cast iron, the outer layer inner surface is appropriate as the inner layer molten metal. It is decided that the inner layer and the outer layer are welded and integrated by preventing the generation of the nest-like defects at the boundary portion of the inner and outer layers by allowing the outer layer material to be mixed into the inner layer after being melted.

At this time, in the present invention, as a result of earnest research as shown in FIGS. 4 and 5, when the outer layer material is ductile cast iron and the inner layer material is spheroidal graphite steel, the outer layer material is mixed into the inner layer. When the outer layer material is nickel grain cast iron and the inner layer material is spheroidal graphite steel, the mixing ratio of the outer layer material to the inner layer is kept to 10 to 40%. That is,
The present invention makes it possible to secure the inner layer strength by setting it to 40% or less (see FIG. 5), while preventing the occurrence of defects at the boundary portion of the inner and outer layers (see FIG. 4) by setting it to 10% or more. It is what

As described above, the present invention intentionally removes the intermediate layer,
By limiting the mixing ratio of the outer layer material to the inner layer as described in the claims, it is possible to secure the desired strength of the inner layer and fusion and integration of the boundary portion of the inner and outer layers. That is, the present invention is remarkably remarkable in its novel peculiarity and action for that purpose.

As described above, according to the present invention, while ensuring the soundness in the vicinity of the boundary between the inner and outer layers, the outer layer is made of ductile cast iron or nickel grain cast iron and is excellent in wear resistance and seizure resistance, and the strength of the inner layer is improved. It is possible to obtain a composite sleeve for a rolling roll having excellent toughness by using the spheroidal graphite steel that is used.

[Example] A composite sleeve for a rolling roll according to the present invention comprises ductile cast iron as an outer layer material, spheroidal graphite steel as an inner layer material, nickel glen cast iron as an outer layer material, and spheroidal graphite steel as an inner layer material. It is a composite sleeve adopted.

Hereinafter, components of each of the above materials and a suitable range of the composition thereof will be described.

Ductile cast iron C: 2.8 to 3.7 wt% ... If C is less than 2.8 wt% (hereinafter simply referred to as%), the amount of graphite becomes small, and the characteristics as a ductile cast iron roll material cannot be fully exhibited. On the other hand, 3.
2.8 to 3.7% because if it exceeds 7%, it becomes brittle.
Specified in the range of.

Si: 1.2 to 2.6% ... If Si is less than 1.2%, the amount of graphite becomes small and the material becomes hard and brittle. On the other hand, if it exceeds 2.6%, the amount of graphite becomes too large and it becomes soft and wear resistance decreases, so 1.
Specify within the range of 2 to 2.6%.

Mn: 0.3-1.0% ... Mn is effective in suppressing the harm of S
If it is less than 0.3%, the effect is not sufficient, and if it exceeds 1.0%, the material is embrittled, so 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 brittle, so 0.1% or less.

S: 0.04% or less ... Since S hinders the spheroidization of graphite, it must be suppressed to a low level, and is 0.04% or less.

Ni: 0.3-3.0% ... Ni promotes graphitization and raises the hardness of the matrix, but if it is less than 0.3%, its effect is insufficient.
If it is contained in excess of%, the retained austenite increases and it becomes difficult to increase the hardness.

Cr: 0.8% or less ... Cr is an element that promotes crystallization of cementite, and if it exceeds 0.8%, the amount of cementite increases and it becomes brittle, which is not preferable, so it is set to 0.8% or less.

Mo: 1.0% or less ... Mo has the effect of increasing the hardness of the base,
If it exceeds 1.0%, it becomes brittle and uneconomical.
1.0% or less.

Mg: 0.02 to 0.1% ... Mg is an element necessary for spheroidizing graphite, but if its content is less than 0.02%, it is not effective, and if it exceeds 0.1%, casting defects occur due to Mg dross. Since it is easy to do so, specify in the range of 0.02 to 0.1%.

Nickel Glen Cast Iron C: 2.7-3.6% ... If the C content is less than 2.7%, the amount of graphite will be too small to fully exhibit the characteristics of the nickel grain cast iron roll material. On the other hand, if more than 3.6% is contained, it becomes brittle, so it is specified in the range of 2.7 to 3.6%.

Si: 0.5-1.2% ... If Si is less than 0.5%, the amount of graphite becomes small and the material becomes hard and brittle. On the other hand, if it exceeds 1.2%, the amount of graphite becomes too large and it becomes soft and wear resistance deteriorates.
Specify within the range of 5 to 1.2%.

Mn: 0.3-1.0% ... If Mn is less than 0.3%, a white pig iron layer is formed on the surface of the roll body, which causes hot cracking during as-casting. On the other hand, 1.
If it exceeds 0%, the shape of the carbides becomes coarse and the material becomes brittle, so it is specified in the range of 0.3 to 1.0%.

P: 0.2% or less ... P increases the fluidity of the molten metal but weakens the material.

S: 0.06% or less ... S is handled as an impurity, not an essential element for roll production. Therefore, 0.06% or less.

Ni: 1.3 to 4.6% ... Ni increases the matrix hardness, but if it is less than 1.3%, its effect is not sufficient, and if it exceeds 4.6%, the amount of retained austenite only increases and the as-cast hardness decreases. ~ 4.6%

Cr: 0.9-2.1% ... Cr is a carbide-forming element and contributes to the improvement of wear resistance together with C. If it is less than 0.9%, the effect is not sufficient, and if it exceeds 2.1%, the amount of cementite increases and it becomes brittle, so it is specified in the range of 0.9 to 2.1%.

Mo: 1.0% or less ... Mo has the effect of increasing the hardness of the base,
If it exceeds 1.0%, it becomes brittle and uneconomical, so 1.0
% Or less.

Spheroidal graphite steel C: 1.0 to 2.0% ... C melts into the matrix to secure the strength and forms carbide effective for wear resistance. In addition, a part thereof becomes graphite, which contributes to the improvement of heat crack resistance.
However, if the C content is less than 1.0%, the above effect cannot be obtained, while if it exceeds 2.0%, the graphite tends to become non-spherical, and the toughness deteriorates. Therefore, C is within the range of 1.0 to 2.0%.

Si: 1.0-3.0% ... Si is an element effective for crystallizing the above-mentioned graphite, but if the content is less than 1.0%, its effect cannot be expected, while if it exceeds 3.0%, it is dissolved in ferrite. Si deteriorates the toughness of the material.
Content of 1.0 to 3.0%.

Mn: 0.2-1.0% ... Mn is known as a hardenability improving element, and in addition to maximizing this effect, considering that segregation at the grain boundary when too much deteriorates toughness,
The range is 0.2 to 1.0%.

P: 0.1% or less ... Although P increases the fluidity of the molten metal,
Since the material becomes brittle and causes casting defects, the lower the content, the better. It is 0.1% or less.

S: 0.1% or less ... Since S causes brittleness of material and casting defects like P, it is desirable that the content is as low as possible.
0.1% or less.

Ni: 0.1-1.0% ... Ni is effective for securing strength and toughness, but if it is less than 0.1%, its effect is insufficient and 1.0%.
Even if it exceeds, the effect is almost saturated, and further the cost is increased, so the content is made necessary and sufficient 0.1 to 1.0%.

Cr: 0.1 to 1.0% ... Cr contributes to strengthening the matrix, but if it is less than 0.1%, it has no effect, and if it exceeds 1.0%, it is difficult to crystallize graphite and deteriorates toughness. Therefore, it is set to 0.1 to 1.0%.

Mo: 0.1-1.0% ... Mo increases toughness like Ni.
However, if it is less than 0.1%, there is no effect, while if it exceeds 1.0%, the increase in the effect is small compared to the rate of increase in the amount added. Therefore, considering the economic efficiency, the content should be 0.1%.
~ 1.0%.

Then, the composite sleeve for rolling rolls of the present invention is manufactured as follows.

An outer shell layer (hollow outer layer) is formed by centrifugally casting an outer layer molten metal composed of ductile cast iron and nickel grain cast iron.

An inner layer molten metal made of spheroidal graphite steel is cast into the outer layer.
At this time, while completely welding the outer layer material and the inner layer material,
It is necessary to eliminate the formation of nests near the boundary between the inner and outer layers.

Therefore, in the present invention, when the inner layer molten metal is cast into the outer shell layer in the above, the inner layer molten metal melts the inner surface of the outer shell layer, and an appropriate amount of the outer layer material is mixed into the inner layer for welding and integration. To do so. Here, if the amount of penetration on the inner surface of the outer shell layer is small, cavities (defects) occur near the boundary between the inner and outer layers, and if the amount of penetration is too large, the toughness of the inner layer material is reduced. Therefore,
In the above case, it is necessary to perform casting under appropriate casting conditions so that the mixing ratio of the outer layer material into the inner layer is a value optimized in advance according to the combination of the materials of the inner and outer layers. here,
The above-mentioned outer layer material mixing ratio is the weight% of the weight of the outer layer material mixed in the inner layer with respect to the total weight of the inner layer molten metal. And
The total weight of the inner layer molten metal is the weight including the weight of the inner layer molten metal and the weight of the outer layer material dissolved in the inner layer molten metal.

According to the knowledge of the inventor, some of the cases where the proper casting conditions can be satisfied are listed below.

(A) Casting is performed by adopting a heating temperature that exceeds the solidification temperature determined by the injection temperature and the components of the outer layer molten metal by about 100 ° C.

(B) To prevent the occurrence of defects at the boundary between the inner and outer layers,
The gravity multiple during centrifugal casting (numerical value that indicates how much the centrifugal force is multiplied by gravity: GNO) is set so that GNO ≧ 70 on the inner surface of the outer molten metal after casting of the outer molten metal (see Fig. 2). .

(C) To prevent the occurrence of defects at the boundary between the inner and outer layers,
The injection thickness of the inner layer molten metal is 40 mm or more (see Fig. 3).

(D) In order to secure the strength of the inner layer and prevent the occurrence of defects at the boundary between the inner and outer layers, when the outer layer material is ductile cast iron and the inner layer material is spheroidal graphite steel, the mixing ratio of the outer layer material to the inner layer is 10 to 40. % (See Fig. 4 and Fig. 5), the outer layer material is nickel-grain cast iron, and the inner layer material is spheroidal graphite steel.
Casting is aimed at 40% (see Fig. 4 and Fig. 5).

By adopting the above casting conditions (A) to (D),
It is possible to obtain a composite sleeve in which not only the inner layer but also the boundary between the inner and outer layers are significantly improved in mechanical properties, and particularly, tensile strength and impact value are significantly improved.

Hereinafter, the results of specific implementation of the present invention will be described.

Table 1 shows the chemical compositions of the outer layer material made of ductile cast iron and the inner layer material made of spheroidal graphite steel. To produce a sleeve roll material with an outer diameter of 860 mmφ, an inner diameter of 400 mmφ and a length of 2600 mm using the outer layer material and the inner layer material of the above composition, the outer layer material melt thickness 120 m
Centrifugal casting was performed with a structure in which the inner layer material was the molten metal. The injection temperature at this time was 1330 ° C. for the outer layer material melt and 1530 ° C. for the inner layer material melt injected into the hollow portion after solidification of the outer layer material, and after 31 minutes after centrifugal casting of the outer layer material melt, the inner layer material melt Was injected. The obtained composite sleeve is subjected to heat treatment after solidification,
It was machined and used as a vertical roll of a universal mill for H-shaped steel rolling, but it could be smoothly rolled without any accident. The mixing ratio of the outer layer material to the inner layer was 30.3%,
There were no defects near the boundary between the inner and outer layers.

Table 2 shows the chemical compositions of the outer layer material made of nickel grain cast iron and the inner layer material made of spheroidal graphite steel. Outer diameter 900 mm
In order to manufacture a sleeve roll material of φ, inner diameter of 460 mmφ, and length of 1800 mm with the outer layer material and the inner layer material having the above composition, the outer layer material melt thickness was 105 mm, and the remainder was centrifugal casting with the inner layer material melt. The injection temperature at this time was 1320 ° C. for the outer layer material melt and 1520 ° C. for the inner layer material melt, and 21 minutes after centrifugal casting of the outer layer material melt, the inner layer material melt was injected into the outer layer hollow. The obtained composite sleeve was subjected to heat treatment after solidification, machined, and used as a vertical roll of a universal mill for H-shaped steel rolling, but it could be smoothly rolled without any accident. The mixing ratio of the outer layer material to the inner layer was 25.4%, and there were no defects near the boundary between the inner and outer layers.

That is, as is apparent from each of the above-described examples, an outer layer is formed of ductile cast iron and nickel grain cast iron, and an inner layer is formed of spheroidal graphite steel to form a composite sleeve. A composite sleeve having an outer layer excellent in wear resistance and seizure resistance and an inner layer excellent in toughness, which does not cause a fracture accident even when applied to, was obtained. Therefore, the ductile cast iron roll and the nickel grain cast iron roll can be practically applied to the high load rolling field, and the use results thereof can be improved.

As described above, according to the present invention, a rolling roll having excellent wear resistance and seizure resistance for the outer layer and excellent toughness for the inner layer while ensuring soundness in the vicinity of the boundary between the inner and outer layers. A composite sleeve can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the state of defects generated near the boundary between the inner and outer layers, FIG. 2 is a diagram showing the relationship between the gravity multiple of the inner surface of the outer layer molten metal and the number of defects at the boundary portion, and FIG. 3 is the injection of the inner layer molten metal. FIG. 4 is a diagram showing the relationship between the thickness and the number of defects at the boundary portion, FIG. 4 is a diagram showing the relationship between the mixing ratio of the outer layer material and the number of defects at the boundary portion when the outer layer material is ductile cast iron or nickel grain cast iron, FIG. The figure is a diagram showing the relationship between the mixture ratio of the outer layer material and the toughness of the inner layer when the outer layer material is ductile cast iron or nickel grain cast iron.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-55552 (JP, A) JP-A-61-176409 (JP, A) JP-A-61-176408 (JP, A) JP-B 59- 30484 (JP, B1) JP 60-21003 (JP, B1) JP 53-24371 (JP, B2)

Claims (2)

[Claims] 1. A composite sleeve for rolling rolls, wherein the inner layer material and the outer layer material are made of different materials, the inner layer material is spheroidal graphite steel, the outer layer material is ductile cast iron or nickel grain cast iron, and the outer layer material is mixed in the inner layer. The outer layer material mixed in the inner layer is the outer layer material mixed ratio with respect to the total inner layer molten metal weight,
It is a composite sleeve for rolling rolls. Mixing ratio when the outer layer material is ductile cast iron and inner layer material is spheroidal graphite steel: 10-40% Mixing rate when the outer layer material is nickel grain cast iron and inner layer material is spheroidal graphite steel: 10-40% 2. A method for producing a composite sleeve for a rolling roll, comprising casting an outer layer of molten metal by centrifugal casting followed by casting of an inner layer of molten metal,
The outer layer molten metal is ductile cast iron or nickel glen cast iron, the outer layer molten metal is cast to form an outer shell layer, the inner layer molten metal is spherical graphite steel, and the inner layer molten metal is cast into the outer shell layer. This is a manufacturing method in which the surface is melted by a predetermined amount with the inner layer molten metal, and the outer layer material is mixed into the inner layer by welding, and the outer layer material mixing ratio of the outer layer material weight mixed in the inner layer to the total inner layer molten metal weight is as follows. And a method for manufacturing a composite sleeve for a rolling roll. Mixing ratio when the outer layer material is ductile cast iron and inner layer material is spheroidal graphite steel: 10-40% Mixing rate when the outer layer material is nickel grain cast iron and inner layer material is spheroidal graphite steel: 10-40%