JPS63290609A - Composite sleeve for rolling roll and its manufacture - Google Patents

Abstract

PURPOSE:To secure wear and seizure resistances required for an outer layer and to secure a toughness required for an inner layer as to a composite sleeve for a rolling roll, by using steel materials for an inner layer and cast iron materials for an outer layer. CONSTITUTION:The material for the outer layer is constituted of cast iron system such as a ductile cast iron, nickel grain cast iron, high chromium cast iron to secure wear resistance and seizure resistance required for the outer layer. On the other hand, for the inner layer material to be constituted of a steel system such as nodular graphite cast iron, the toughness required of the inner layer is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite sleeve for rolls used in hot rolling, cold rolling, etc., and a method for manufacturing the same.

[Conventional technology] In recent years, rolling technology has progressed with the aim of making continuous hot rolling, improving productivity, and improving the quality of rolls. Along with this, rolling rolls are often used under harsh conditions, and various improvements have been made. has been done. In addition, the quality required for rolled III products has become higher, and accordingly, the quality required for rolling rolls has also become stricter.

Therefore, conventionally, studies on the material of rolling rolls, adoption of composite sleeves to strengthen rolling rolls, and techniques for further strengthening the inner layer of composite sleeves have been proposed. No. 59-11857,
Japanese Patent Publication No. 59-20417, Japanese Patent Publication No. 55-1588H, Japanese Patent Publication No. 0-281810, etc. propose techniques for inner-layer toughened composite sleeves. In these conventional composite sleeves, when the outer layer is made of ductile cast iron, nickel grain cast iron, or high chromium cast iron, the inner layer material is made of ordinary cast iron, ductile cast iron, etc. to ensure soundness near the boundary between the inner and outer layers. Cast iron material will be used.

According to the above-mentioned conventional composite sleeve for rolling rolls, 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 ensured.

[Problems to be Solved by the Invention] However, in the above conventional composite sleeve for rolling rolls, when the outer layer material is made of cast iron material, the inner layer material is also made of cast iron material for the above-mentioned reasons. There are difficulties in ensuring high toughness. Here, in a composite sleeve, rolling load, thermal stress during rolling, and residual stress from sleeve manufacturing act on the inner layer as tensile stress, so the inner layer material needs to be strong enough to withstand the inner layer tensile stress. Ru. Therefore, when a conventional composite sleeve is subjected to high-load rolling, if the inner layer is made of a cast iron material such as ordinary cast iron or ductile cast iron, there is concern about the toughness of the inner layer.

The present invention has excellent wear resistance and seizure resistance for the outer layer,
Regarding the inner layer, the object is to provide a composite sleeve for rolling rolls with excellent toughness.

[Problems to be Solved by the Invention] The composite sleeve for rolls according to the present invention is a composite sleeve for rolls in which the inner layer material and the outer layer material are each made of different materials, wherein the inner layer material is a copper-based material, and the outer layer material is a copper-based material. is made of cast iron material.

The method for manufacturing a composite sleeve for rolling rolls according to the present invention includes:
In a method for manufacturing a composite sleeve for a rolling roll in which the outer layer molten metal is poured and then the inner layer molten metal is poured by centrifugal casting, the outer layer molten metal is made of cast iron, and after the outer layer molten metal is cast to form an outer shell layer, the above-mentioned molten metal is cast. The inner layer molten metal is made of steel, and when the inner layer molten metal is cast, a predetermined amount of the inner surface of the outer shell layer is melted by the inner layer molten metal, and the outer layer material is mixed into the inner layer and welded and integrated.

[Function] According to the present invention, since the outer layer material is made of cast iron material 1 such as ductile cast iron, nickel grain cast iron, and high chromium cast iron, it has the wear resistance and seizure resistance required for the outer layer. Secured. On the other hand, since the inner layer material is made of a copper-based material such as spherical graphite m, the toughness required for the inner layer is ensured.

By the way, in the composite sleeve for rolling rolls of the present invention, the solidification start temperature of the outer layer material, such as ductile cast iron or nickel grain cast iron, is around 1200°C, or the solidification start temperature of high chromium cast iron is around 1300°C. On the other hand, the solidification start temperature of the inner layer material is around 1450℃,
In addition to the large solidification onset temperature difference between the two layers, the solidification onset temperature of the inner layer material is higher than that of the outer layer material, so when using the conventional manufacturing method, the boundary between the inner and outer layers as shown in Figure 1. A phenomenon in which nests were easily formed was observed.

Therefore, when manufacturing the composite sleeve for rolling rolls of the present invention, when the inner layer molten metal made of copper-based material is poured into the outer layer formed by solidifying the cast iron-based material, the inner surface of the outer layer is melted in an appropriate amount by the inner layer molten metal. By mixing the outer layer material into the inner layer, it was possible to prevent the occurrence of middle-east defects at the boundary between the L2 and inner and outer layers, and to integrate the inner and outer layers by welding.

That is, according to the present invention, it is possible to obtain a composite sleeve for a rolling roll whose outer layer has excellent wear resistance and seizure resistance, and whose inner layer has excellent toughness.

[Example] Preferred examples of the composite sleeve for rolling rolls according to the present invention include: (1) a composite sleeve using ductile cast iron as the outer layer material and spheroidal graphite steel as the inner layer material; (2) a composite sleeve using nickel grain cast iron as the outer layer material and inner layer material. Composite sleeves made of spheroidal graphite steel as the material; Composite sleeves made of high chromium cast iron as the outer layer material and spheroidal graphite steel as the inner layer material.

The components of each of the above materials and the preferred ranges of their compositions will be explained below.

■Ductile cast iron C: 2.8-3.7wt%...C is 2.8wt% (
If the content is less than 3.7%, the graphite content will be too small and the characteristics of the ductile cast iron roll material cannot be fully demonstrated.On the other hand, if the content exceeds 3.7%, it will become brittle. Specified in the range of ~3.7%.

Si: 1.2 to 2.6%...When Si is less than 1.2%, the amount of graphite decreases and the material becomes hard and brittle. On the other hand, 2.6%
If the graphite content exceeds this amount, the amount of graphite becomes too large and becomes soft, resulting in a decrease in wear resistance.

Mn: 0.3 to 1.0%...Mn is effective in suppressing the harm caused by S, but if it is less than 0.3%, the effect is not sufficient, and if it exceeds 1.0%, it will deteriorate the material. 0 as it makes it brittle.
．． It is specified in the range of 3 to 1.0%.

P: 0.1% or less... P increases the fluidity of the molten metal, but it makes the material brittle, so it should be kept at 0.1% or less.

S: 0.04% or less... S inhibits the spheroidization of graphite, so it needs to be kept low, and is set to 0.04% or less.

Xi: 0.3 to 3.0%...Ni promotes graphitization and increases base hardness, but if it is less than 0.3%, the effect is insufficient, and if it is contained in excess of 3.0% When this happens, retained austenite increases and hardness becomes difficult to increase.

Cr: 0.8% or less...Or is an element that promotes the crystallization of cementite, and if it is contained in excess of 0.8%, the amount of cementite increases and becomes brittle, which is undesirable, so 0.8% The following shall apply.

Mo: 1.0% or less: No has the effect of increasing base hardness, but if it exceeds 1.0%, it becomes brittle and is also uneconomical, so it is set to 1.0% or less.

Mg: 0.02-0.1%...Mg is an element necessary for spheroidizing graphite, but if its content is less than 0.02%, it has no effect; If it exceeds 0.0, casting defects are likely to occur due to Mg dross, etc.
It is specified in the range of 2 to 0.1%.

■Nickel grain cast iron C: 2.7 to 3.6%... If C is less than 2.7%, the characteristics of the nickel grain cast iron roll material, which has a small amount of graphite, cannot be fully exhibited.On the other hand, 3. If the content exceeds 6%, the content becomes brittle, so the content is specified in the range of 2.7 to 3.6%.

Si: 0.5 to 1.2%...If Si is less than 0.5%, the amount of graphite decreases, making it hard and brittle. On the other hand, 1.
If it exceeds 2%, the amount of graphite becomes too large and becomes soft, resulting in decreased wear resistance, so it is specified within the range of 0.5 to 1.2%.

Mn: 0.3 to 1.0% - If Mn is less than 0.3%, a white iron layer is formed on the surface of the roll body, causing hot cracking during as-casting. On the other hand, if it exceeds 1.0%, the shape of the carbide 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 makes the material brittle, so it should be 0.2% or less.

S: 0.06% or less...S is not a necessary element in roll manufacturing, but is treated as an impurity, therefore 0.0
6% or less.

Ni: 1.3 to 4.6%...Ni increases base hardness, but if it is less than 1.3%, the effect is not sufficient.
If the content exceeds 4.8%, the amount of retained austenite only increases and the as-cast hardness decreases, so it is 1.3 to 4.6%.
%.

Cr: 0.9 to 2.1%...Cr is a carbide-forming element, and together with C, contributes to improving wear resistance. 0.93
If the content is less than 2.1%, the effect will not be sufficient, and if it exceeds 2.1%, the amount of cementite will increase and become brittle, so the content is specified in the range of 0.8 to 2.1%.

Mo: 1.0% or less...No has the effect of increasing base hardness, but if it exceeds 1.0%, it becomes brittle and uneconomical, so it is set to 1.0% or less.

I) The high chromium cast iron outer layer shall contain 10 to 20% Or in order to have the desired characteristics as a high chromium roll. That is, the crystallization of Cr carbide necessary to maintain sufficient wear resistance is insufficient when the Or content is less than 10%.
In addition, in order to have sufficient roughness resistance, if the Or content exceeds 20%, too much Cr will be dissolved in the matrix, which tends to form riostenite and ferrite, resulting in a decrease in thermal conductivity. This is because it is harmful.

Regarding the high chromium cast iron of the outer layer, the components other than Or are not particularly limited, but as in the case of conventional high chromium rolls, C2, about 0 to 3.2%, Si 0.5 to
It usually contains about 1.5%, Mo about 0.3 to 4%, and in addition, Xi 1.5% or less, Nb 1.0
% or less, (1) may contain about 1.0% or less.

■ Spheroidal graphite steel C: 1.0 to 2.0%...C melts into the matrix to ensure strength and produces carbides effective for wear resistance. In addition, some of it becomes graphite and contributes to the north-south resistance to heat cracking. However, if the C content is less than 1.0%, the above effects cannot be obtained, while if it exceeds 2.0%, the graphite tends to lose its spherical shape, resulting in deterioration of toughness. Therefore, C should be within the range of 1.0 to 2.0%.

Si + 1.0 to 3.0%...Sl is an element effective in crystallizing the graphite mentioned above, but when the content is 1.0% to 3.0%...
．． If it is less than 0%, the effect cannot be expected, and on the other hand, if it is 3.0%,
If the Si content exceeds 1.0 to 3.0%, the Si dissolved in the ferrite will deteriorate the toughness of the material.
Within the range of %.

Mn'+ 0.2-1.0%...Mn is known as an element that improves hardenability, and while maximizing this effect, if too much is present, segregation to grain boundaries will deteriorate toughness. In consideration of this, the range is set to 0.2 to 1.0%.

P: 0.1% or less... P increases the fluidity of the molten metal, but it also makes the material brittle and causes casting defects, so the lower the content, the better, and 0.1% or less. do.

S: 0.1% or less...Similar to P, S causes weakening of the material and casting defects, so the content is desirably as low as possible, and is set to 0.1% or less.

Ni: 0.1 to 1.0%...Ni is effective in ensuring strength and toughness, but if it is less than 0.1%, the effect is insufficient, and if it exceeds 1.0%, the effect is insufficient. Since the effect is almost saturated and the cost increases, the content is set to a necessary and sufficient O91 to 1.0%.

Cr: 0.1-1.0%...Cr contributes to strengthening the base, but less than 0.1% has no effect, while 1.0%
%, it becomes difficult for graphite to crystallize and the toughness deteriorates. Therefore, it was set at 0.1 to 1.0%.

Mo: 0.1 to 1.0%...Mo increases toughness similarly to Xi. However, if it is less than 0.1%, it has no effect; on the other hand, 1. Even if it exceeds Q%, the increase in effect will be small compared to the rate of increase in the amount added. Therefore, considering economic efficiency, the content was set to 0.1 to 1.0%.

Thus, the composite sleeve for mill rolls of the present invention is manufactured as follows.

■Outer layer molten metal made of ductile cast iron, nickel grain cast iron, high chromium cast iron, etc. is centrifugally cast to form an outer shell layer (hollow outer layer).

■Inner layer molten metal made of spheroidal graphite steel, etc. is cast into the above outer layer. At this time, it is necessary to completely weld the outer layer material and the inner layer material, and to eliminate the occurrence of cavities 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 step (■), the inner layer molten metal melts the inner surface of the outer shell layer, and an appropriate amount of the outer layer material is poured into the inner layer on the inner surface of the outer shell layer. If the amount of penetration is small, cavities (defects) will 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 will decrease. It is necessary to perform casting under appropriate casting conditions so that the mixing ratio becomes a value optimized in advance according to the combination of materials for the inner and outer layers.

According to the inventor's findings, some cases where appropriate casting conditions can be satisfied are listed below.

(A) Casting is performed using a heating temperature that is approximately 100°C higher than the solidification temperature determined by the injection temperature and components of the outer layer molten metal.

(B) To prevent defects from occurring at the boundary between the inner and outer layers,
The gravity multiplier (number indicating how many times the centrifugal force is compared to gravity: GNO) during centrifugal casting is set so that GNO≧70 on the inner surface of the outer layer molten metal after pouring the outer layer molten metal (see Figure 2). .

(C) To prevent defects from occurring at the boundary between the inner and outer layers,
The injection thickness of the inner layer molten metal is set to 41)+m or more (see Fig. 3).

(D) In order to ensure 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 into the inner layer is 10 to 10%. If the outer layer material is nickel grain cast iron and the inner layer material is spheroidal graphite steel, the mixing rate of the outer layer material into the inner layer is 10 to 40%. Figure 4.
(Refer to Figure 5), ■ If the outer layer material is high chromium cast iron and the inner layer material is spheroidal graphite steel, casting should be performed with the goal of mixing the outer layer into the inner layer at a rate of 2 to 15% (Figures 6 and 7). (see figure)
.

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

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

■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. Outer diameter 860mmφ
In order to manufacture a sleeve roll material having an inner diameter of 400 mm and a length of 2600 mm by using an outer layer material and an inner layer material having the above composition, centrifugal casting was performed with the outer layer material being solidified to a thickness of 120 mm and the remaining material being a molten inner layer material. The injection temperature at this time is such that the molten metal for the outer layer is 1
The temperature of the molten inner layer material injected into the hollow part after solidification of the outer layer material was 1530°C, and the temperature of the molten outer layer material was 31°C after centrifugal casting.
After a few minutes had elapsed, the molten metal for the inner layer material was injected. The obtained composite sleeve was subjected to post-solidification heat treatment and mechanical processing.
It was subjected to a vertical roll of a universal mill for H-type steel rolling, but
Rolling was carried out smoothly without any accidents. The mixing rate of the outer layer material into the inner layer was 30.3%, and 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. In order to manufacture a sleeve roll material with an outer diameter of 900 Φ, an inner diameter of 460 Φ, and a length of 1800 Φ using the outer layer material and inner layer material of the above composition, after solidifying the outer layer material, 105 snow weight, and the rest the inner layer material molten metal. Centrifugal casting was performed using the following configuration. The injection temperature at this time was 1320° C. for the outer layer material molten metal and 1520° C. for the inner layer material molten metal, and the inner layer material molten metal was injected into the outer layer hollow 21 minutes after centrifugal casting of the outer layer material molten metal. The obtained composite sleeve was subjected to heat treatment after solidification, machined, and subjected to vertical rolls of a universal mill for rolling H-type steel, and was successfully rolled without any accidents. The mixing rate of the outer layer material into the inner layer is 2.
5.4%, and there were no defects near the boundary between the inner and outer layers. Table 3 shows the chemical compositions of the outer layer material made of high chromium cast iron and the inner layer material made of spheroidal graphite steel. Outer diameter 980 φ,
In order to manufacture a sleeve roll material with an inner diameter of 540 mm and a length of 800 mm using the outer layer material and inner layer material having the above composition, centrifugal casting was performed after solidifying the outer layer material for 130 m and leaving the remainder as the molten inner layer material. At this time, the injection temperature was 1420℃ for the outer layer material molten metal.
The temperature of the molten inner layer material was 1,520° C., and the molten inner layer material was injected into the hollow outer layer 34 minutes after centrifugal casting of the molten outer layer material. The obtained composite sleeve was subjected to post-solidification heat treatment, machined, and subjected to horizontal rolls of a universal mill for rolling H-type steel, and was successfully rolled without any accidents. The mixing rate of outer layer material into the inner layer is 3.2.
%, and there were no defects near the boundary between the inner and outer layers.

That is, as is clear from the above examples, by forming the outer layer with ductile cast iron, nickel grain cast iron or high chromium cast iron and forming the inner layer with spheroidal graphite steel to form a composite sleeve, it is possible to obtain a composite sleeve for rolling H-shaped steel. A composite sleeve consisting of an outer layer with excellent wear resistance and seizure resistance and an inner layer with excellent toughness, which does not cause breakage accidents even when applied to the roll of a universal mill, was obtained. Therefore, it has become possible to practically apply ductile cast iron rolls, nickel grain cast iron rolls, or high chromium cast iron rolls to the field of high-load rolling, and it has been possible to improve the performance of their use.

[Effects of the Invention] As described above, the present invention provides a composite sleeve for rolling rolls in which the outer layer has excellent wear resistance and seizure resistance, and the inner layer has excellent toughness, and a method for manufacturing the same. Can be done.

[Brief explanation of the drawings] Fig. 1 is a schematic diagram showing the state of defects occurring 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 defect points at the boundary, Figure 3 is a diagram showing the relationship between the injection thickness of the inner layer molten metal and the number of defect points at the boundary, and Figure 4 is a diagram showing the relationship between the mixing ratio of the outer layer material and the number of defect points at the boundary when the outer layer material is ductile cast iron or nickel grain cast iron. Figure 5 is a diagram showing the relationship between the outer layer material content and inner layer toughness when the outer layer material is ductile cast iron or nickel grain cast iron, and Figure 6 is a diagram showing the relationship between the outer layer material and the inner layer toughness when the outer layer material is high chromium cast iron. Fig. 7 is a diagram showing the relationship between the mixing ratio of the outer layer material and the number of boundary defect points in the case where the outer layer material is high chromium cast iron. . Agent Patent Attorney Osamu Shiokawa Oil Temperature 1 Table 2 Table 1 Figure 2 Figure 2 GN□ (gravitational depression) of the inner surface of the outer layer molten metal Figure 3 Injection source of the inner layer molten metal (mm) Figure 4 Injection into the inner layer Figure 5. Temperature of the outer layer material into the inner layer. Ratio of tensile strength to +00゜0 Figure 6.

Claims (6)

[Claims] (1) A composite sleeve for rolling rolls in which the inner layer material and the outer layer material are each made of different materials, wherein the inner layer material is a steel-based material and the outer layer material is a cast iron-based material. (2) A composite sleeve for a rolling roll according to claim 1, wherein the inner layer material is made of spheroidal graphite steel and the outer layer material is made of ductile cast iron. (3) A composite sleeve for a rolling roll according to claim 1, wherein the inner layer material is made of spheroidal graphite steel and the outer layer material is made of nickel grain cast iron. (4) A composite sleeve for rolling rolls according to claim 1, wherein the inner layer material is made of spheroidal graphite steel and the outer layer material is made of high chromium cast iron. (5) In the method for manufacturing a composite sleeve for a rolling roll, in which the outer layer molten metal is poured and the inner layer molten metal is poured by centrifugal casting, the outer layer molten metal is cast iron-based, and the outer layer molten metal is cast to form an outer shell layer. After that, the inner layer molten metal is made of steel, and when the inner layer molten metal is cast, a predetermined amount of the inner surface of the outer shell layer is melted by the inner layer molten metal, and the outer layer material is mixed into the inner layer and welded and integrated. A method for manufacturing a composite sleeve for rolling rolls. (6) In claim 5, the composite for rolling rolls has a mixing ratio of the outer layer material mixed into the inner layer with respect to the weight of the inner layer molten metal as shown in (a) to (c) below. How to make a sleeve. (a) Mixing rate when the outer layer material is ductile cast iron and the inner layer material is spheroidal graphite steel: 10 to 40% (b) Mixing rate when the outer layer material is nickel grain cast iron and the inner layer material is spheroidal graphite steel: 10 ~40% (c) Contamination rate when the outer layer material is high chromium cast iron and the inner layer material is spheroidal graphite steel: 2 to 15%