JPH1171628A - Composite rolling roll excellent in thermal shock resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite rolling roll excellent in thermal shock resistance and wear resistance. SOLUTION: In a composite rolling roll in which an inside ring part cast and joined to an outside ring part composed of tungsten carbide base cemented carbide is composed of a spherical graphite cast iron, the outside ring part is composed of tungsten carbide base cemented carbide contg., as bonding phase forming components, 5 to 27% Co, 2 to 12% Ni, 0.3 to 3% Cr, and the balance WC as dispersed phase forming components, and the inside ring part is composed of the spherical graphite cast iron having a compsn. contg. 3 to 4.5% C, 1.5 to 4.5% Si, 0.1 to 2% Mn, 0.02 to 0.2% Mg, and the balance Fe with inevitable impurities, and in which spherical graphite with a core structure having a core part formed at the time of casting and a peripheral part precipitated at the time of heat treatment is dispersed into a matrix essentially consisting of mixed phases of any of pearlitic phases, bainitic phases and martensitic phases with ferritic phases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite rolling roll having excellent thermal shock resistance.

[0002]

2. Description of the Related Art Conventionally, steel, copper alloy and Al
A composite rolling roll is known as a structural member of a rolling device for non-ferrous alloys such as alloys. Further, as a composite rolling roll, for example, as described in Japanese Patent Publication No. 6-99776, the outer ring portion is made of a tungsten carbide-based cemented carbide (hereinafter simply referred to as cemented carbide), Is known in which an inner ring portion cast and bonded to a cast iron is made of spheroidal graphite cast iron.

[0003]

On the other hand, in recent years, high performance and high output of a rolling mill have been remarkable, and with this,
The rolling speed and the rolling ratio tend to increase further, and when the rolling speed and the rolling ratio increase in this way, the contact between the surface portion of the rolling roll and the rolled material is naturally intermittent, so the rolling roll is more severe. Although it is subjected to repeated thermal shocks, in the case of the above-mentioned conventional composite rolling rolls, under such severe operating conditions, cracks are likely to occur due to insufficient thermal shock resistance.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of researching to develop a composite rolling roll having excellent thermal shock resistance, the outer ring portion was formed by weight% (hereinafter,% indicates weight%), and both formed a binder phase. As components, Co: 5 to 27%, Ni: 2 to 12%, Cr: 0.3 to 3%, and the balance is substantially tungsten carbide (hereinafter referred to as WC) as a dispersed phase forming component. C: 3 to 4.5%, Si: 1.5 to 4.5%, Mn: 0.1 to 2%, Mg: 0 .02 to 0.2%, and optionally Mo, Cu, Cr, V,
One or more of W, Sn, and Sb:
0.1 to 5%, and the remainder is cast with a molten metal having a composition consisting of Fe and inevitable impurities, and is made of spheroidal graphite cast iron having a structure in which spheroidal graphite is dispersed and distributed in a base material mainly composed of a pearlite phase. A composite rolling roll formed by joining the formed inner ring portions is formed, and then, the resulting composite rolling roll is heated at a temperature of 450 ° C. or higher and a temperature not higher than the solidus of the spheroidal graphite cast iron. When the heat treatment is repeated, cooling is performed, a ferrite phase is formed on the base material of the spheroidal graphite cast iron constituting the inner ring portion, and the base material becomes a mixed phase mainly composed of a pearlite phase and a ferrite phase, and is formed at the time of casting. The graphite precipitates around the periphery of the spheroidal graphite, and as a result, a spheroidal graphite having a cored structure with the spheroidal graphite generated at the time of casting as the core and the graphite precipitated by the heat treatment as the periphery is formed. As described above, spherical graphite having a cored structure of spherical graphite in which graphite is deposited around the periphery of spherical graphite generated at the time of casting is dispersed in a base material in which the inner ring portion is mainly composed of a pearlite phase and a ferrite phase. Combined rolling rolls made of cast iron, combined with the fact that the outer ring portion is made of a cemented carbide having the above composition, has excellent thermal shock resistance, and can be used for high-speed rolling and rolling at a large rolling ratio. It does not crack, exhibits excellent performance over a long period of time, and further performs austempering treatment and tempering treatment on this composite rolling roll to make the pearlite phase of the base material of spheroidal graphite cast iron constituting the inner ring part. Transform into bainite phase or martensite phase, and make the matrix mainly bainite phase and ferrite phase or martensite phase and ferrite phase respectively. When tissue is of even more strength to obtain a finding that will be improved.

The present invention has been made based on the above research results, wherein the outer ring portion is made of cemented carbide, and the inner ring portion cast and joined to the outer ring portion is made of spheroidal graphite cast iron. In the composite rolling roll
Each of the outer ring portions contains, as a binding phase forming component, Co: 5 to 27%, Ni: 2 to 12%, and Cr: 0.3 to 3%, with the balance being substantially a dispersed phase forming component. WC as
And the inner ring portion is composed of C: 3 to 4.5%, Si: 1.5 to 4.5%, Mn: 0.1 to 2%, and Mg: 0. .02 to 0.2%, and if necessary, Mo, Cu, Cr,
One or more of V, W, Sn, and Sb: 0.1 to 5%, the balance being Fe and unavoidable impurities, and a pearlite phase, a bainite phase, and Any one of the martensite phases and a base material mainly composed of a mixed phase of a ferrite phase are dispersed with a cored structure of spherical graphite, and the cored structure of spherical graphite is formed by heat treatment with a core portion formed at the time of casting. The present invention is characterized by a composite rolling roll having excellent thermal shock resistance and made of spheroidal graphite cast iron having a structure composed of a peripheral portion that is sometimes precipitated.

In manufacturing the composite rolling roll of the present invention, (a) the inner surface of the outer ring portion is preheated to a temperature of 600 ° C. or more before casting of the molten spheroidal graphite cast iron; The molten metal cast by the method of, for example, discarding the molten metal and preheating the entire mold including the outer ring portion, (c) setting the casting temperature of the spheroidal graphite cast iron molten metal to 1450 ° C. or more, and the like to the inner surface of the outer ring portion. At the interface of the molten metal for more than 10 seconds to cause interdiffusion between the outer ring and the outer ring, so that it is released over a width of 0.2 mm or more at the joint interface between the two rings. When graphite is deposited, the adhesion between the outer ring portion and the inner ring portion is further improved.

Next, the reason why the compositions of the cemented carbide and the spheroidal graphite cast iron constituting the outer ring portion and the inner ring portion of the composite rolling roll of the present invention are limited as described above will be described. (A) Cemented carbide (a) Co The Co component has the effect of improving sinterability and forming a binder phase to improve toughness. Cannot be obtained. On the other hand, if the content exceeds 27%, the abrasion resistance rapidly decreases. Therefore, the content is 5 to 27%, preferably 1%.
It was determined as 0 to 20%.

(B) Ni The Ni component improves sinterability in the same manner as the Co component.
o forms a binder phase by forming a solid solution in o to improve toughness, and also has an effect of improving oxidation resistance and corrosion resistance in the presence of a Cr component. However, if the content is less than 2%, desired oxidation resistance is obtained. The effect of improving the resistance and corrosion resistance is not obtained. On the other hand, if the content exceeds 12%, the impact resistance decreases, so the content is set to 2 to 12%, preferably 5 to 10%. Was.

(C) Cr The Cr component forms a binder phase by forming a solid solution with Ni in Co and, as described above, has the effect of improving oxidation resistance and corrosion resistance in the presence of the Ni component. If the content is less than 0.3%, a desired effect cannot be obtained in the above-mentioned action. On the other hand, if the content exceeds 3%, Cr carbide is precipitated and the toughness is reduced. 0.3
３3%, desirably 0.9 to 2.4%.

(B) Spheroidal graphite cast iron (a) In the C component, a cored spheroidal graphite is formed to improve the thermal shock resistance, and a pearlite phase, bainite phase or martensite phase of the base is formed. However, if the content is less than 3%, the desired effect cannot be obtained, while the content is 4.5%.
%, The ratio of the spheroidal graphite to the base material becomes too large and the strength rapidly decreases. Therefore, the content is determined to be 3 to 4.5%, preferably 3.2 to 4%. .

(B) Si The Si component not only promotes the production of spheroidal graphite but also improves the castability (castability of the molten metal). When the content exceeds 4.5%, the ferrite phase of the base material becomes a brittle silicon ferrite phase, and the strength and impact resistance are reduced. It was determined to be 1.5 to 4.5%, preferably 1.7 to 3%.

(C) Mn The Mn component has an effect of stabilizing the formation of the base pearlite phase during casting (if the formation of the pearlite phase becomes unstable, the formation of the ferrite phase in the heat treatment in the subsequent step is also unstable). However, it is difficult to obtain a desired tissue stably), but if the content is less than 0.1%, the desired effect cannot be obtained in the above-mentioned action, while the content exceeds 2%. And the toughness is reduced, the content is 0.1
２2%, preferably 0.2-1%.

(D) Mg The Mg component has the effect of spheroidizing graphite and thereby improving the strength. However, if the content is less than 0.02%, the desired effect cannot be obtained. Content 0.2
%, The crystallization of graphite is suppressed, and chilling occurs to cause embrittlement.
0.2%, preferably 0.03-0.1%.

(E) Mo, Cu, V, W, Sn, and Sb These components have an effect of further stabilizing the formation of a pearlite phase during casting (hereinafter, these are collectively referred to as “structure stabilizing components”). ) Is contained as necessary, but if the content is less than 0.1%, the desired effect cannot be obtained in the above-mentioned action, while if the content exceeds 5%, the toughness is reduced. The content is reduced to 0.1 to 5
%, Desirably 0.3 to 2%.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a composite rolling row according to the present invention will be described.
Examples will be specifically described with reference to examples. As raw material powder,
WC powder having an average particle diameter of 1 to 5 μm, Cr
_Three C _Two Powder, Co powder, and Ni powder
The raw material powder was blended into the blending composition shown in Table 1 and
For 72 hours, and after drying, 1 ton / cm
^Two Press molding into a ring-shaped green compact with the pressure of
To a predetermined temperature in the range of 1300 to 1500 ° C. in vacuum
Sintering under the condition of holding for 1 hour, substantially the above composition
It is made of cemented carbide having the same composition and has an outer diameter of:
It has dimensions of 50 mm x inside diameter: 34 mm x width: 10 mm
The outer ring portions A to E were respectively manufactured. On the other hand, usually
The component sets shown in Table 2 were obtained using
Of molten spheroidal graphite cast iron for inner ring parts a to p
And adjust the melt to the combination shown in Table 3.
The above outer ring part was used as a mold, and this was preheated to 750 ° C.
It is cast in a heated state, cooled, and the inner ring portions a to p are removed.
Formed integrally with each of the outer ring portions AE
After that, the inner ring part is machined,
1, the shape shown in a schematic perspective view, that is, the inner diameter: 18 m
m, one side surface of the inner ring part and the outer phosphorus of the above dimensions
The inner ring part is made flush with one side surface of the ring part.
Of the outer ring portion from the other side surface of the outer ring portion.
5 mm protruding, this protrusion has an outer diameter of 34 mm,
Width on the other side of the inner ring portion: 6 mm x depth:
1.3mm diametric key groove facing the opposite position
Comparative composite rolling by finishing in two locations
Rolls 1 to 16 were manufactured. In addition, the comparative composite rolling mill
In all of the rules 1 to 16,
The spheroidal graphite cast iron of the ring is made of
It had a structure in which spheroidal graphite was dispersed and distributed in the ground.

Next, as shown in Table 3, the comparative composite rolling rolls 1 to 16 were heated to 950 ° C. at a heating rate of 100 ° C./hr, and held at this heating temperature for 2 hours.
One cycle of cooling at a cooling rate of 100 ° C./hr to 50 ° C.
The composite rolling rolls 1 to 16 of the present invention were respectively manufactured by subjecting to heat treatment in which cooling was repeated three cycles. Therefore, each of the composite rolls 1 to 16 of the present invention has the same shape and dimensions as those of the comparative composite rolls 1 to 16. The resulting composite rolling rolls 1 to 16 of the present invention have a spherical core of a cored structure consisting of a core and a peripheral portion, each of which has a spherical graphite cast iron of an inner ring portion on a base material mainly composed of a pearlite phase and a ferrite phase. It had a structure in which graphite was dispersed and distributed. Further, the roll is selected from the above-described composite rolling rolls 1 to 16 of the present invention, and (a) 900
C. for 1 hour, then immersed in 320 ° C. salt bath and quenched.
Hold for a while, take out and air-cooled austempering,
(B) After holding at 900 ° C. for 1 hour, immersing and quenching in 200 ° C. oil, holding for 1 minute, taking out and subjecting to air-cooled marquenching treatment, and subjecting to any of the heat treatments (a) and (b) above. As shown in Table 3, the structure of the base material of the spheroidal graphite cast iron constituting the inner ring portion was a bainite phase and a ferrite phase, or a martensite phase and a ferrite phase.

Next, the composite rolling roll 1 of the present invention will be described.
After heating to 800 ° C. with a burner, immediately after immersion and quenching in water as one cycle, an accelerated thermal shock test of repeatedly performing this was performed on the outer ring portion constituting the same. The number of cycles until the occurrence of cracks observed with the naked eye was measured.
Table 3 shows the measurement results.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

From the results shown in Table 3, all of the composite rolling rolls 1 to 16 of the present invention show much higher thermal shock resistance than the comparative composite rolling rolls 1 to 16 in the accelerated thermal shock test. This is the structure of the spheroidal graphite cast iron constituting the inner ring part of the composite rolling roll, that is, one of the pearlite phase, bainite phase, and martensite phase, and a base mainly composed of a mixed phase of ferrite phase,
In contrast to the structure in which cored spherical graphite is dispersed and distributed, the other is apparently caused by the structure in which ordinary spherical graphite is dispersed and distributed in a base material mainly composed of a pearlite phase. It is. As described above, the composite rolling roll of the present invention has excellent thermal shock resistance,
In addition, since it has excellent abrasion resistance, it can sufficiently respond to a further increase in the rolling speed and the rolling reduction accompanying the high performance and high output of the rolling mill.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing the shape of a composite rolling roll manufactured in an example.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Naoshi Yamashita, Inventor 1528 Nakashinda, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Inside of Gifu Works, Mitsubishi Materials Corporation (72) Inventor Koichi Mabuchi Kobe-cho, Anpachi-gun, Gifu Prefecture 1528 Nakaiden, Yokoi Mitsubishi Materials Corporation Gifu Works (72) Inventor Noriyuki Kakehashi Kobe-cho, Yahachi-gun, Gifu Prefecture 1528 Nakashinda Yokoi Corporation Gifu Works Mitsubishi Materials Corporation (72) Inventor Kisho Miwa Gifu 1528 Nakashinden, Yokoi, Kobe-cho, Anpachi-gun, Prefecture Mitsubishi Materials Corporation

Claims (2)

[Claims] 1. A composite rolling roll in which an outer ring portion is made of a tungsten carbide-based cemented carbide, and an inner ring portion cast and joined to the outer ring portion is made of spheroidal graphite cast iron. % By weight, each containing 5 to 27% of Co, 2 to 12% of Ni, and 0.3 to 3% of Cr as the binder phase forming component, and the remainder substantially as the dispersed phase forming component. The inner ring portion is also made of a tungsten carbide-based cemented carbide having a composition of tungsten carbide, and the above-mentioned inner ring portion is also in the same weight%, C: 3 to 4.5%, Si: 1.5 to 4.5%, Mn: 0.1 to 2%, Mg: 0.02 to 0.2%, the balance being Fe and inevitable impurities, and any one of a pearlite phase, a bainite phase, and a martensite phase And ferrite phase Mixed phases into a green body made mainly, spherical graphite cored structure is dispersed distribution,
The cored structure of the spheroidal graphite, a core generated during casting,
A composite roll having excellent thermal shock resistance, comprising a spheroidal graphite cast iron having a structure comprising a peripheral portion precipitated during heat treatment. 2. A composite rolling roll in which an outer ring portion is formed of a tungsten carbide-based cemented carbide, and an inner ring portion cast and joined to the outer ring portion is formed of spheroidal graphite cast iron. % By weight, each containing 5 to 27% of Co, 2 to 12% of Ni, and 0.3 to 3% of Cr as the binder phase forming component, and the remainder substantially as the dispersed phase forming component. The inner ring portion is also made of a tungsten carbide-based cemented carbide having a composition of tungsten carbide, and the above-mentioned inner ring portion is also in the same weight%, C: 3 to 4.5%, Si: 1.5 to 4.5%, Mn: 0.1 to 2%, Mg: 0.02 to 0.2%, and one or more of Mo, Cu, Cr, V, W, Sn, and Sb: 0. 1-5%, with the balance being Fe and inevitable impurities And a pearlite phase, a bainite phase, and a martensite phase, and a base material mainly composed of a mixed phase of a ferrite phase, a cored structure of spherical graphite is dispersed and distributed, and the cored structure is Wherein the spheroidal graphite comprises a spheroidal graphite cast iron having a structure consisting of a core portion formed during casting and a peripheral portion precipitated during heat treatment.