JPH0651205B2 - Hottrante Bull Roller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a roller used for a hot run table of hot rolling equipment, and more particularly to a roller used in a cooling zone (wet zone) after a header after finish rolling. Regarding suitable rollers.

<Prior art> Conventional steel, ordinary cast iron, and Cr-Mo steel are used for the conventional hot run table roller.The long tube obtained by casting these molten metals by the centrifugal force casting method is subjected to surface heat treatment. Various types of processing such as padding were performed to form an integral sleeve, which was fixed to the roller shaft to form a roller.

In recent years, in order to improve wear resistance, a high wear resistant composite roller having a composite of metal and ceramic particles as an outer layer has been realized.

<Problems to be solved by the invention> The conventional metal hot run table roller described above is intended to improve wear resistance by utilizing hardness due to carbides and a hardened structure. Wear resistance is insufficient, and Cr-Mo steel has excellent wear resistance,
All of them are inferior in corrosion resistance, and have problems such as inferior corrosion resistance in use in the wet zone using cooling water.

In addition, since the long one-piece sleeve is fixed to the roller shaft, it has a large unit weight, requires a large amount of driving energy, and is disadvantageous in terms of running cost.

Furthermore, the thickness of the above-mentioned one-piece sleeve cannot usually be increased due to the limitation of the roller diameter, so that centrifugal force casting of a thin long tube which is difficult to manufacture has been forced.

On the other hand, in a roller having a composite of metal and ceramic particles as an outer layer, a metal mixed with ceramics is selectively worn away, and problems such as chipping off of ceramic particles occur, and when used in the wet zone, corrosion of the metal part is caused. It's a problem. However, the problem can be solved by using a high alloy material in which the metal portion is excellent in wear resistance and corrosion resistance, but a new problem of high cost arises.

<Means for Solving the Problems> The present invention has been made for the purpose of solving the above problems, and a technical means thereof is a sleeve comprising an outer ceramic layer and an inner metal layer, The ceramic outer layer is composed of a dense first outer layer portion and a second outer layer portion in which pores are impregnated with a metal, and the metal material impregnated in the second outer layer portion is metallurgically continuous with the inner metal layer, In addition, a plurality of ceramic-metal composite sleeves satisfying the conditions of outer diameter / ceramic outer layer thickness <8.0, ceramic outer layer thickness / metal inner layer thickness> 1.5 are fixed to the roller shaft at intervals. This is the point.

<Example> Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a hot run table roller 1 of the present invention,
A plurality of ceramics-metal composite sleeves 2 are fixed to the roller shaft 7 at a predetermined interval.

The sleeve 2 comprises a ceramic outer layer 3 and a metal inner layer 6, and the ceramic outer layer 3 has a dense first outer layer portion 4 formed by densely sintering ceramic particles, and the first outer layer portion 4.
And the second outer layer portion 5 formed by impregnating the pores of the ceramic layer, which is sintered with a certain porosity, with a metal. The metal material with which the portion 5 is impregnated is metallurgically continuous with the metal inner layer 6.

Ceramics include metal oxides, silicides, nitrides,
There are metal carbides, borides, etc., and when molding the ceramic outer layer, that is, the cylindrical ceramic molded body, for example, at the time of powder compaction of ceramic powder particles, the dense first outer layer portion corresponds to fine particles densely and the second outer layer The part corresponding to the part adjusts the mixing ratio of the thermoplastic binder in which the ceramic particles are mixed, increases the particle size of the ceramic particles,
Further, by compacting the compacting pressure to reduce the compacting pressure and firing, a compact for the outer layer having a dense surface layer portion and a certain degree of porosity can be obtained.

In this case, it is appropriate that the dense first outer layer portion has a porosity of 0 to 5%, and since this ceramic layer is a used layer, there is no reaction between water and metal, which is a cause of corrosion, and therefore the surface portion is corroded. No cracks, such as cracks, are generated, and accordingly, great resistance is exerted to wear due to chipping and the like of the surface portion.

Furthermore, since the thermal conductivity is low, the resistance against thermal shock from the hot coil is large.

The porosity of the second outer layer portion impregnated with metal is preferably gradually increased from the surface layer portion and is preferably 40 to 60% at the interface with the inner layer. By doing so, the pores are impregnated with metal. The ceramic outer layer retains excellent heat insulation properties, as well as has improved strength and toughness, and the gradual increase of the impregnated metal makes it possible to smooth the change of the material and avoid troubles such as peeling.

However, even if the porosity increases discontinuously, there is practically no problem as long as the porosity does not exceed 40 to 60%.

As a general method for producing a porous ceramic molded body, there is known a method of impregnating urethane foam having a network skeleton with a ceramics slurry, followed by drying and firing the dried molded body. The same method can be used to form For example, a dense layer of ceramic powder is further molded and fired on the outer surface of a cylindrical molded body obtained by impregnating the urethane foam with a ceramics slurry and drying.

The metal impregnation (permeation) and the molding of the metal inner layer into the ceramic outer layer molded body thus obtained can be easily performed by centrifugal casting.

For example, as shown in FIG. 2, the ceramic outer layer molded body 3a is placed in a centrifugal casting mold 8 with a refractory material 9 and a band 1.
Fixing with 0, 10 and rotating the mold 8 in this state, the casting material molten metal for pouring into the pores of the ceramic outer layer molded body is poured into the ceramic outer layer molded body using the gutter 11.
Pour into 3a. At this time, it is desirable to provide spaces 12, 12 as much as possible so that both end surfaces of the molded body 3a come into contact with the cast molten metal. This is because the end surface portion is rapidly solidified by cooling and it is difficult to obtain the required penetration into the ceramics.

Further, as a means for assisting penetration, it is desirable to preheat the ceramic outer layer molded body 3a to 400 to 1200 ° C.
At this time, preheating in an inert gas is also an effective means in order to prevent deterioration such as oxidation due to preheating. In addition, the preheating also has an effect of preventing cracking of the ceramic outer layer molded body 3a due to thermal shock generated by casting and cracking prevention due to difference in shrinkage between the two after casting.

Regarding the number of mold rotations in centrifugal casting, a larger GNo. And a higher casting temperature promotes permeation. Generally G
The number is about G20 to G200, but of course G200 or more is preferable because it can increase the penetration.

The casting molten metal can be made of ordinary cast iron because the sleeve surface layer portion (first outer layer portion) is a dense ceramic layer and the metal does not directly serve as a use layer, and in terms of strength and toughness, ductile cast iron, high-grade cast iron, Cast steel etc. can be selected. High-grade cast iron is superior in terms of permeability. Of course, it is possible to use other ferrous materials or non-ferrous materials in some cases.

The casting amount is an amount sufficient to fill the pores of the second outer layer portion and form the inner layer, and of course the finishing allowance of the inner layer will be taken into consideration.

By casting as described above, the metal material with which the second outer layer portion is impregnated and the metal inner layer are metallurgically continuous.

In addition, the material with good permeability such as the high-grade cast iron is first
The amount that is impregnated into the outer layer or a little extra is cast, and then a material with high strength, such as adamite,
If graphite cast steel or the like is cast, the penetration and mechanical strength can be easily achieved, and the metal inner layer and the impregnated metal material are metallurgically continuous.

Next, the dimensional relationship of the sleeve according to the present invention will be described. In the present invention, the outer diameter / ceramics outer layer thickness <8.0 ceramics outer layer thickness / metal inner layer thickness> 1.5 is limited. As a result, cracks due to thermal expansion and contraction of the ceramic outer layer can be suppressed. The coefficient of thermal expansion of ceramics is 4
× 10 ^-6 1 / ℃ The thermal expansion coefficient of metal is about 12 × 10 ^-6 1 / ℃, and the expansion of the ceramic when the molten metal is impregnated from the inner surface of the ceramic is about 1 × 10 ^-3 (0.1%). Ceramic ceramics, which have a small plastic deformation and a low thermal shock resistance, require careful attention to cracks during rapid heating. The same applies to the shrinkage process during solidification and cooling after the molten metal is impregnated.

As one of the means, it is conceivable to reduce the stress generated in the ceramics by making the thickness of the ceramics layer sufficiently larger than the metal layer pressure and at the same time increasing the thickness of the ceramics layer with respect to the outer diameter.

That is, when the outer diameter / ceramics thickness exceeds 8.0, the stress acting on the ceramic cross section increases and there is a problem of cracking.

Further, when the ceramic thickness / metal thickness <1.5, the generated thermal stress becomes large, which causes a crack problem.

In other words, the safety of the ceramic outer layer itself against thermal expansion and contraction, and the safety of the ceramic outer layer and the metal inner layer whose expansion coefficient greatly differs from each other are taken into consideration.

The ceramic-metal composite sleeve has been described above. However, as described above, the present invention is one in which a plurality of the sleeves are fixed to the roller shaft by a fixing means such as shrink fit to form a hot run table roller. Since it has the ceramic outer layer and the short sleeves are arranged at intervals, the unit weight is small and the driving energy is small.

Next, specific examples of the present invention will be shown.

The manufactured product is a hot run table roller with a body diameter of 310φ and a body length of 1800 (mm). A ceramic-metal composite sleeve with an outer diameter of 310φ, an inner diameter of 200φ, and an axial length of 200 (mm) is a roller made of S35C material of 200φ. Shrink on the shaft.

(1) Ceramics Outer Layer Molded Body An A ₂ O ₃ molded body having an outer diameter of 310 φ, an inner diameter of 230 φ, a wall thickness of 40 t and a length of 250 (mm) was used. The porosity of the molded body is
The inner surface gradually increases to 3 to 50%.

(2) Casting The A ₂ O ₃ compact was set on the inner surface of the die for centrifugal casting, and then the compact was preheated. (800 ° C.) The above mold was rotated at G80, and in that state, 30 kg of molten cast iron having the composition shown in the following table (corresponding to the amount of the second outer layer impregnated and the metal inner layer molding having a wall thickness of 20 mm) was cast at 1300 ° C.

(3) Post-casting treatment After solidification of the metal inner layer, remove the sleeve from the mold and remove both ends by 25 mm.
It was cut.

(4) Shrink fit After cutting the inner surface of the sleeve, four shrink fit rollers were formed on a roller shaft of S35C having an outer diameter of 200φ at a shrink fit ratio of 6/10000.

(5) Investigation results As a result of disassembling the roller and examining the sleeve cross section, the ceramic outer layer and the metal inner layer were in good contact with each other, and the second outer layer portion of the ceramic was also well impregnated with metal.

<Effects of the Invention> As described above, the hot run table roller of the present invention has excellent corrosion resistance and wear resistance because it has the first outer layer portion of the dense ceramics layer, and therefore also has excellent corrosion wear resistance. In addition, it has excellent heat resistance and heat insulation properties and has a large resistance to thermal shock. Furthermore, by impregnating the second outer layer portion of the ceramic outer layer with a metal, strength and toughness are improved, and The diameter and thickness of the outer ceramic layer and the thickness of the inner metal layer are relatively limited to ensure safety against thermal expansion and contraction. In addition, the short sleeves are placed at intervals to achieve weight reduction and energy saving. Although it is a very excellent roller as a roller used in the cooling zone of a hot run table, it can also be used in other departments such as a slab conveying roller before finish rolling. The business value is enormous.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a hot run table roller of the present invention, and FIG. 2 is a schematic sectional view showing a method for manufacturing a ceramic-metal composite sleeve according to the hot run table roller of the present invention. 1 ... Hot run table roller, 2 ... Ceramics-metal composite sleeve, 3 ... Ceramics outer layer, 3a ...
... Ceramics outer layer molded body, 4 ... First outer layer portion, 5 ...
... second outer layer portion, 6 ... metal inner layer, 7 ... roller shaft.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-127957 (JP, A) JP-A-60-146514 (JP, A) JP-A-60-247450 (JP, A)

Claims (1)

[Claims] 1. A sleeve comprising a ceramic outer layer and a metal inner layer, wherein the ceramic outer layer comprises a dense first outer layer portion and a second outer layer portion in which pores are impregnated with a metal, and A ceramic material in which the metal material with which the outer layer is impregnated is metallurgically continuous with the metal inner layer and satisfies the conditions of outer diameter / ceramic outer layer thickness <8.0, ceramic outer layer thickness / metal inner layer thickness> 1.5. A hot run table roller comprising a plurality of metal composite sleeves fixed to a roller shaft at intervals.