JP2010075978A - Manufacturing method of composite roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a composite roll which generates homogenous casting of the inside layer molten metal onto the outside layer without causing localized erosion on the inside surface of the outer layer even if molten metal stream is shaken, when molten metal for the inside layer is poured from above to the inside of the outside layer formed by a centrifugal casting method. <P>SOLUTION: The manufacturing method of the composite roll includes a first process and a second process. The first process comprises the steps of: placing a casting mold in a horizontal or tilted posture on a mold supporting roller of the centrifugal casting machine: pouring the outside layer molten metal into the casting mold keeping the mold rotating around its center axis; and forming the outside layer of roll barrel by the centrifugal casting method. The second process comprises the steps of: placing the mold with the formed outside layer on a rotation table with its center axis vertical; and pouring the inside layer molten metal from above to the inside of the outside layer while rotating the rotation table around its rotational center. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for efficiently producing a composite roll having different components of inner and outer layers of a roll body using a centrifugal casting machine, and more particularly to a method for producing a composite roll used for rolling steel.
Here, the inner layer of the roll body part means the roll shaft part excluding the surface part, while the outer layer of the roll body part means the surface part. The outer layer is composed of one layer or a plurality of layers.

As is well known, as a characteristic of a roll used for rolling a metal such as steel, the surface portion of the roll body portion is excellent in wear resistance, while the inner roll shaft portion needs to have high toughness. For this reason, it is common practice to produce composite rolls using different components in the inner and outer layers of the roll body using a centrifugal casting machine (Patent Documents 1, 2, 3, 4, etc.).
When both the inner and outer layers of the roll body are formed by centrifugal casting, for example, the outer layer molten metal L1 is first poured into the mold while rotating the mold 1 shown in FIG. 6A around the center 1a. The outer layer W1 is formed, and then the inner layer molten metal is poured inside to form an inner layer that is a roll shaft portion.

  The method adjusts the rotational speed of the mold 1 to adjust the centrifugal force, and further adjusts the inclination angle of the mold for each part such as the surface of the roll body, the inner roll shaft, and both roll necks. (Patent Documents 2, 3, and 4). In FIG. 6A, 23 is a centrifugal force applying motor, 2 and 3 are mold support members of a centrifugal casting machine, 2a and 3a are mold support rollers, 5 is a ladle, and 6 is a pouring funnel mounted on the mold 1. Respectively. A known tilt type centrifugal casting machine is used to adjust the tilt angle of the mold.

  In FIG. 7, the characteristic view of the composite roll which formed the outer layer of the roll trunk | drum part with the centrifugal casting method using the centrifugal casting machine was shown. In this case, since the high hardness outer layer W1 is not sufficiently melted into the inner layer molten metal that becomes the low hardness inner layer W3, the hardness of the inner layer W3 rapidly increases toward the outer layer W1. It is known that when such a composite roll is subjected to rolling, the outer layer is easily peeled off during use.

  Therefore, Patent Document 1 discloses a manufacturing method for manufacturing a composite roll having excellent spalling resistance. The manufacturing method described in Patent Document 1 uses the centrifugal casting machine shown in FIG. 6 (a), the first step of forming the outer layer W1 of the roll body portion by the centrifugal casting method, and FIG. 6 (b). As described above, the second step of pouring the inner layer molten metal L3 from below with the mold 1 placed in a tub and with the mold 1 stationary is provided. In FIG. 6 (b), 21 indicates a lower pouring pipe connection port provided in the mold 1, and the inner layer molten metal L 3 is poured into the mold 1 from here. The molten metal lower pouring pipe 24 is connected to the lower pouring pipe connection port 21 for use. The mold 1 is provided with a molten metal discharge port 22.

According to this two-step manufacturing method, as shown in FIG. 8, the outer layer W1 of the roll body can be sufficiently dissolved in the inner layer molten metal poured into the inner side, and the inner and outer layers of the roll body can be A composite roll formed by metallurgically welding can be obtained.
JP-A-56-99065 JP 60-216960 A JP 56-168954 JP 57-91864 A

However, the manufacturing method of the composite roll of patent document 1 is the length exceeding the roll full length (the length of a roll trunk | drum and the length of the roll neck part of the both sides) from the inner layer molten metal L3 below from the 2nd process. Therefore, there is a disadvantage that the production efficiency is inferior because it is necessary to pour the molten metal through the molten metal lower pouring tube 24.
On the other hand, as shown in FIG. 4A, if the second step of pouring the inner layer molten metal L3 from above is used, an upper pouring funnel 7 having a nozzle having an opening formed on the lower side is used. Therefore, it becomes possible to produce a composite roll efficiently.

Here, FIG. 4A shows a state in which the molten metal flow 10 flowing down does not shake when the inner layer molten metal L3 is poured from above, and FIG. 5A shows the molten metal flow 11 flowing down. It showed a state with shake. Moreover, in FIG.4 (b) and FIG.5 (b), the penetration state to the inner layer molten metal L3 was each shown typically.
If there is a fixed fluctuation in the molten metal flow 11 that flows down, as shown in FIG. 5 (b), the amount of melt loss at the portion where the inner layer molten metal L3 hits locally becomes excessive, and the molten metal flows on the surface of the roll body. Damaged part 12 occurs. As a result, the inner surface of the roll body formed by centrifugal casting (the outer layer W1 or the intermediate layer W2 formed inside thereof) is not uniformly melted into the inner layer molten metal L3. When such a composite roll is subjected to rolling, the roll life is shortened.

  Therefore, in view of the above-mentioned problems of the prior art, the present invention provides a local area inside the outer layer even when there is a fluctuation in the molten metal flow when pouring the inner layer molten metal from the top inside the outer layer formed by the centrifugal casting method. Provided is a method for producing a composite roll that does not cause a specific melting point and causes uniform melting of the outer layer into the molten inner layer.

As a result of intensive studies on a method for efficiently producing a composite roll having different components in the inner and outer layers of the roll body, the present inventor has poured the inner layer molten metal into the inner side of the outer layer formed by centrifugal casting by pouring the upper layer. In doing so, it was found that the above-mentioned problems could be solved if the second step having the following configuration was made, and the present invention was made based on this finding.
That is, the present invention is as follows.
1. In manufacturing a composite roll made by melting the outer layer of the roll body into the inner layer molten metal poured into the inside, and metallurgically welding the inner and outer layers of the roll body,
The mold is placed horizontally or inclined on the mold support roller of the centrifugal casting machine, and the outer layer melt is poured into the mold while rotating the mold around the center, and the outer layer of the roll body is formed by the centrifugal casting method. In the first step, the mold on which the outer layer is formed is placed on a turntable with its center vertical, and then the inner layer melt is placed inside the outer layer while rotating the turntable around the rotation center. A method for producing a composite roll, comprising a second step of pouring hot water from above.
2. 2. The method for producing a composite roll according to claim 1, wherein in the first step, molten intermediate layer is poured inside the outer layer, and the intermediate layer is formed by centrifugal casting.

  According to the present invention, when pouring the inner layer molten metal from the top to the inner side of the outer layer formed by the centrifugal casting method, even if the inner layer molten metal has a fluctuation, no local melting point is generated on the inner side of the outer layer. The outer layer is uniformly melted into the inner layer molten metal. For this reason, it is difficult to cause peeling between the inner and outer layers of the roll body, and a method for efficiently producing a composite roll having a long life can be realized.

Hereinafter, the method of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view of a centrifugal casting machine suitable for use in the first step of the method of the present invention, and FIG. 2 is a front view of a mold laying and rotating apparatus suitable for use in the second step of the method of the present invention.
(About the first step)
In the first step of the method of the present invention, it is preferable to form the outer layer having the intermediate layer by centrifugal casting using the centrifugal casting machine shown in FIG. In this centrifugal casting machine, the mold inclination angle θ formed by the horizontal direction and the center 1a of the mold 1 can be adjusted. When forming the outer layer and the intermediate layer, θ = 0 or 0 <θ <90 ° Adjust with. However, the present invention is not limited to this, and a centrifugal casting machine in which the mold inclination angle θ is fixed to a predetermined angle may be used.

  The inclined centrifugal casting machine is provided with a mold support roller 4a that is in contact with the lower side surface of the inclined mold 1 and receives a thrust force. A mold support roller 4a that is in contact with the lower side surface of the inclined mold 1 is rotatably supported by the mold support member 4 and is mounted on a bed (not shown). Similarly, the mold support rollers 2 a and 3 a that are in contact with the outer peripheral surface of the mold 1 are also mounted on the bed via the mold support members 2 and 3. In addition, a ladle 5 that can maintain the temperature of the molten metal at a predetermined temperature, a centrifugal force application motor, and the like are provided as in the horizontal centrifugal casting machine shown in FIG.

In FIG. 1, L <b> 1 is an outer layer molten metal that is first poured into the mold, and is maintained at a predetermined temperature in the ladle 5. The pouring funnel 6 that receives the molten metal from the ladle 5 is provided in the opening on the upper side surface of the inclined mold 1 so as to be movable in the axial direction.
The outer layer molten metal L1 held at a predetermined temperature in the ladle 5 is poured into the mold 1 through the funnel 6 for pouring while rotating the mold 1 around the center 1a, and the outer layer W1 of the roll body portion. Is formed by centrifugal casting. After forming the outer layer W1 in this manner, the process may proceed to a second process described later, or the intermediate layer W2 may be further formed by a centrifugal casting machine before proceeding to the second process. In this case, after the ladle 5 filled with the molten intermediate layer for forming the intermediate layer W2 is conveyed to the centrifugal casting machine, the molten intermediate layer is poured into the inner side of the outer layer W1 in the same manner.

At that time, the inner peripheral surface of the outer layer W1 formed by the solidification of the outer layer molten metal first poured into the mold 1 is melted and mixed by the molten intermediate layer poured later (that is, The melting of the inner peripheral surface of the outer layer W1 into the molten intermediate layer is referred to as the melting of the outer layer).
The melt of the intermediate layer maintained at a predetermined temperature is supplied while adjusting the centrifugal force and time applied to the mold 1 with a centrifugal force applying motor so that the outer layer is uniformly melted. About the centrifugal force and time which are added to the casting_mold | template 1, it can be set as the conditions described in patent document 2, for example.

The state when uniform penetration of the outer layer W1 occurs is schematically shown in FIG. The composite roll in which the outer layer is uniformly melted is less likely to cause casting defects between the outer layer W1 and the intermediate layer W2 formed inside thereof.
In this way, in the first step, the intermediate layer melt is poured inside the outer layer W1, and the intermediate layer W2 is formed by centrifugal casting. When the inner and outer layers of the roll body are welded metallurgically, The intermediate layer W2 is preferable because it can be sufficiently melted and the inner and outer layers of the roll body can be welded more strongly metallurgically.
(About the second step)
In the second step of the method of the present invention, it is preferable that the inner layer molten metal L3 is poured from above by using the mold laying and rotating apparatus shown in FIG. 2 to form the inner layer as the roll shaft portion.

The mold culvert placing rotation device includes an upper pouring funnel 7 provided with a nozzle having an opening on the lower side, a turntable 8 having a rotation center 8a, and a pair of mold support rollers 9. .
The upper pouring funnel 7 is used by being inserted into the opening on the upper surface of the mold 1 instead of the pouring funnel 6 used in the first step, and the outer layer W1 and the outer layer W1 are formed on the turntable 8 by centrifugal casting. In some cases, the mold 1 in which the intermediate layer W2 is formed is placed on the inside with the center 1a being vertical.

The mold 1 is rotated by rotating the turntable 8 around the rotation center 8a. Further, the pair of mold support rollers 9 support the mold 1 so that the center 1a of the mold 1 placed on the wall and the rotation center 8a of the turntable 8 coincide with each other, and are positioned on the upper side in FIG. It is made to contact the peripheral surface of the casting_mold | template which forms a roll neck part.
The upper pouring funnel 7 is loosely fitted to the mold 1 and is supported so that it does not rotate even when the mold 1 rotates as the turntable 8 rotates.

  Therefore, during the pouring of the inner layer molten metal L3, a constant fluctuation occurs in the molten metal flow 11, so that the molten metal flow gradually rises by the inner layer molten metal L3 flowing down and reaches the roll neck located on the upper side. 11 locally hits the inside of the surface of the roll body formed by centrifugal casting (see FIG. 5A). As shown in FIG. 5 (b), the melted portion 12 where the molten metal flow 11 hits becomes excessive, resulting in a melted portion 12 and poor penetration of the outer layer or the intermediate layer.

In order to prevent this poor penetration, in the second step of the method of the present invention, a mold in which the intermediate layer W2 is preferably formed on the inner side of the outer layer W1 by the centrifugal casting method using the mold laying and rotating apparatus shown in FIG. 1 is placed on the turntable 8 with its center 1a vertical, and then the inner layer melt L3 is poured from above into the intermediate layer W2 while rotating the turntable 8 around the turn center 8a.
When pouring the inner layer molten metal L3 from above, even if the molten metal flow sways, the inner surface molten metal L3 that flows down is at least until the surface of the molten metal reaches the roll neck located on the upper side. Since the mold 1 placed on the wall is rotated, the molten metal flow swayed in a fixed direction is uniformly applied in the circumferential direction.

  Therefore, the local melted portion 12 as shown in FIG. 5B does not occur, and uniform melting occurs inside the outer layer W1 or inside the intermediate layer W2. As a result, it is difficult for peeling to occur between the inner and outer layers of the roll body, and a long-life composite roll can be efficiently produced. FIG. 3C schematically shows a state when the intermediate layer W2 is uniformly melted.

A work roll for a hot finish rolling mill having an outer layer and an inner layer having the composition shown in Table 1 and having a roll body diameter of 680 mm, a body length of 1500 mm, and a total length of 3600 mm was produced by the method of the present invention.
On the inclined centrifugal caster, the outer layer melt with an injection temperature of 1410 ° C. is poured while rotating the mold with a centrifugal force of 130 G as a gravity multiple to form an outer layer with a wall thickness of 80 mm, and then the outer layer melt injection starts 18 minutes later, an intermediate layer melt corresponding to a thickness of 50 mm was poured. At that time, the mold was rotated so that a centrifugal force of 130 G was applied to the outer layer by a multiple of gravity, and the rotation was continued for about 20 minutes after the molten intermediate layer was poured. The mold inclination angle θ was 20 °.

Under these conditions, an intermediate layer in which the outer layer was uniformly melted was formed by a centrifugal casting method. Table 1 shows the components of the outer layer molten metal and the intermediate layer molten metal.
The process up to this point is the same as that of Patent Document 2. Thereafter, in Patent Document 2, the rotational speed of the mold is gradually reduced, and in the process, the remaining portion, that is, the inner layer that is the roll shaft portion, and the roll neck portions on both sides, are the same components as the melt in the intermediate layer of Table 1. The molten metal is poured and formed by centrifugal casting.

  On the other hand, in the method of the present invention, the surface portion of the roll body (= 180 mm, outer layer thickness: 80 mm, intermediate layer thickness: 100 mm) is formed by centrifugal casting, and then the outer layer and the intermediate layer are formed. The inner layer which is the roll shaft part is poured by pouring the inner layer melt from above while rotating the rotating table at a rotation speed of 5 to 30 rpm. And the roll neck part of both sides was also formed. In the method of the present invention, the molten inner layer having the components shown in Table 1 was poured from above into the mold. For comparison, the inner layer melt was poured from above after placing it on a stationary base that does not rotate.

According to the method of the present invention, the inner layer melt causes uniform melting of the intermediate layer, and the inner and outer layers are firmly metallurgically welded through the intermediate layer. In this case, peeling is unlikely to occur between the inner and outer layers of the roll body.
On the other hand, when the inner layer melt was poured from the top after placing it on a stationary base that did not rotate as a comparison, the inner layer melt caused by the inner layer melt became uneven in the circumferential direction. Because of this, there were some rolls that had a shorter life than the rolls produced by the method of the present invention.

  In addition, the composite roll manufactured by the method of Patent Document 2 is also formed by forming an outer layer, an intermediate layer (however, the same component as the inner layer molten metal) and an inner layer that is a roll shaft portion by centrifugal casting, Since it is small and is not sufficiently melted into the inner layer molten metal, when it is used for a work roll of hot finish rolling, its life is shorter than that of the method of the present invention.

It is a front view of a centrifugal casting machine suitable for use in the first step of the method of the present invention. It is a front view of a mold laying and rotating apparatus suitable for use in the second step of the method of the present invention. (A), (b), (c) is sectional drawing which shows typically the effect | action and effect of this invention method. (A), (b) is the longitudinal cross-sectional view which shows the inside of a casting_mold | template when a molten metal flow is normal, when a casting_mold | template is placed in a stationary state, and an inner-layer molten metal is poured from the top, It is the XX sectional drawing. . (A), (b) is the longitudinal cross-sectional view which shows a problem when a molten metal flow fluctuates, when casting an inner layer molten metal from the top with a casting_mold | template standing still, and it is the XX sectional drawing. It is a front view which shows the centrifugal casting machine used for the manufacturing method of the composite roll described in patent document 1, and a bottom pouring casting apparatus. It is a characteristic view of the composite roll which formed the outer layer in the roll trunk | drum using a centrifugal casting machine. It is a characteristic view of the composite roll obtained with the manufacturing method of patent document 1.

Explanation of symbols

θ Mold inclination angle L1 Outer layer melt L2 Middle layer melt L3 Inner layer melt W1 Outer layer W2 Middle layer W3 Inner layer (roll shaft)
DESCRIPTION OF SYMBOLS 1 Mold 1a Center of mold 1 2, 3, 4 Mold support member 2a, 3a, 4a Mold support roller of centrifugal casting machine 5 Ladle 6 Funnel for pouring 7 Funnel for pouring 8 Turntable 8a Rotation center of turntable 8 9 Mold support roller
10, 11 Molten metal flow
12 Melting point
21 Bottom pouring pipe connection port
22 Molten metal outlet
23 Centrifugal force motor
24 Molten pouring tube

Claims (2)

In manufacturing a composite roll made by melting the outer layer of the roll body into the inner layer molten metal poured into the inside, and metallurgically welding the inner and outer layers of the roll body,
The mold is placed horizontally or inclined on the mold support roller of the centrifugal casting machine, and the outer layer melt is poured into the mold while rotating the mold around the center, and the outer layer of the roll body is formed by the centrifugal casting method. In the first step, the mold on which the outer layer is formed is placed on a turntable with its center vertical, and then the inner layer melt is placed inside the outer layer while rotating the turntable around the rotation center. A method for producing a composite roll, comprising a second step of pouring hot water from above.   2. The method for producing a composite roll according to claim 1, wherein in the first step, molten intermediate layer is poured inside the outer layer, and the intermediate layer is formed by centrifugal casting.

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