JPH07124726A - Mold for centrifugal casting - Google Patents

Abstract

PURPOSE:To manufacture a roll for rolling having sound outer shell, particularly the outer shell without casting defect by arranging a sublimation shield body at a boundary part between a metallic mold part and a sand mold part. CONSTITUTION:Molten metal for outer shell cast to form the outer shell layer 7 is passed through the inner surface of the metallic mold part 1 and collided to a disk-like sublimation shield body 8. In the case the sublimation shield body 8 is made of a paper of corrugated cardboard, etc., the cast molten metal is not stuck to the paper and instantially fluidized on the paper surface and not invaded into the paper surface. Therefore, the molten metal receives the centrifugal action of the mold rotated at high speed during instantial fluidizing on the paper for several tens of sec and turns over on the disk-like sublimation shield body 8 and twins onto the inner surface of the metallic mold part 1. Further, it is prevented to develop the casting flash and the sticking caused by the contact of the molten metal with the sand mold part 2. Then, in the case the sublimation shield body 8 is plate-like paper, the body is perfectly burnt within about one min and burnt off and lost and harmful gas is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved centrifugal casting mold for a cylindrical or cylindrical body, and more particularly to a centrifugal casting mold capable of preventing the occurrence of casting defects in the outer shell layer of a rolling roll.

[0002]

2. Description of the Related Art Centrifugal casting of a cylinder or a cylindrical body is a casting method in which a molten metal is cast into a mold which is rotating at a high speed and the molten metal is solidified to produce a product. The product has a diameter of 20.
Cylindrical solid products or hollow sleeve products (rolling rolls and cast iron pipes) of various sizes ranging from small size of about 0 mm to large size of 1000 mm or more are manufactured.

However, in connection with the casting of the molten metal in the centrifugal casting method, the occurrence of casting defects has not been completely eliminated in relation to the structure of the mold, the casting method and the like.
Therefore, various improved techniques related to the centrifugal casting method have been proposed. For example, Japanese Utility Model Publication No. 4-80650 discloses a mold for centrifugal casting of a two-layer pipe in which the components of the outer layer and the inner layer are different from each other, and describes a mold in which a liner is fitted to the inner surface on the inner layer casting side of the mold. This liner prevents local remelting of the outer layer by pouring the molten metal for the inner layer directly onto the outer layer that has already been cast and solidified when the molten metal for the inner layer is cast. It is intended to prevent it.

Further, in Japanese Unexamined Patent Publication No. 4-190952, uneven coating of a coating material on the inner peripheral wall of the die (in a die for producing a small diameter tube, a nozzle for applying the coating material is sufficiently inserted into the die). Centrifugal casting method has been proposed to prevent seizure due to (due to difficulty). That is, a seizure prevention sheet having a ceramic paper as a suitable example is adhered to the inner peripheral wall of a die for centrifugal casting, a coating material is applied to the inner peripheral surface of the seizure prevention sheet, and then the die is driven and rotated. Meanwhile, the molten metal is cast into the mold. To prevent seizure, a seizure prevention sheet that covers the inner peripheral wall of the mold is mainly used, and a coating material is used to supplement it, so that the seizure phenomenon does not occur so much that the coating condition of the coating material is not significantly affected. This is for avoidance.

Based on the same inventive idea as described in the above-mentioned Japanese Patent Laid-Open No. 4-190952, a mold for centrifugal casting is provided with an outer mold made of metal and an inner mold made of paperboard fitted and held in the outer mold. Has been proposed, a centrifugal casting method has been proposed in which a mold casting material is applied to the inner peripheral surface of the inner mold, and then the molten metal is cast into the mold while driving and rotating the centrifugal casting mold. No. 190953). Furthermore, if the paperboard is used as it is, the molten metal may be burned on the inner peripheral wall of the mold during casting, and the quality of the product may deteriorate, or the mold may not be used immediately. There has also been proposed a centrifugal casting mold in which the prepared paperboard is fitted and held as an inner mold (Japanese Patent Laid-Open No. 4-190954). These are proposals for preventing casting defects such as seizure in relation to the molten metal and the coating material applied to the inner surface of the mold.

FIG. 3 schematically shows an example of a conventional centrifugal casting mold for producing a composite roll, which is composed of an outer shell layer and a core material. Sand mold parts 2 and 3 are provided at both ends of a mold part 1 whose inner surface is coated, and end covers 4 and 5 are fixed to the outer sides thereof. The end cover 5 has an opening at its center so that the molten metal can be poured into the cavity 6 in the direction of arrow A when the molten outer shell layer is cast. This mold is placed in an inclined or horizontal or vertical state, and the molten metal is cast while being rotated at a high speed.

[0007]

In order to form the outer shell layer 7, the initial outer shell layer melt cast in the cavity 6 in the mold by the casting nozzle (not shown) in the direction of arrow A is When it passes through the inner surface of the mold part 1 and comes into contact with the sand mold part 2 as shown by an arrow B, it instantly forms a casting burr, which is a thin solidified film having a thickness of several millimeters, on the surface of the sand mold part 2 and sand grains. Insertion occurs between them, causing seizure. Most of the molten metal passes through the surface of the sand mold portion 2 as it is, and collides with the end cover 4. The colliding molten metal is pushed by the momentum of the molten metal that is pushed in one after another, and is also subjected to the influence of the centrifugal force to be flipped along the surface of the sand mold portion 2 as shown by an arrow B while the inner surface of the mold portion 1 is being inverted. The outer shell layer 7 is formed on the inner surface of the mold while trying to synchronize with the rotation of the mold. A part of the molten metal, which has been turned over and directed toward the pouring port side, comes into contact with the sand mold portion 3 and similarly forms a casting burr. The molten metal that moves in this manner synchronizes with the rotation of the mold with the passage of time, the reciprocating movement of the molten metal disappears, and solidification proceeds while synchronizing with the centrifugal force to form the outer shell layer 7.

The solidified material of the molten metal which has been caused by the above-mentioned casting burr and seizure with sand grains is re-melted by the molten metal which is successively squeezed and entrains impurities such as sand grains to form the outer shell layer
However, there is a problem in that it solidifies as it is in the molten metal that forms the slag and causes casting defects such as cavities and inclusion of foreign matter.

Among the materials for forming the outer shell layer 7, a rolling roll made of high alloy cast iron mainly used as a finishing second stage roll of a steel plate rolling machine has casting defects such as a blowhole and a foreign material bite. When it occurs, it increases the basic unit of the rolling roll and deteriorates the quality of the coil that is the material to be rolled. On the other hand, since steel sheets in recent years tend to be upgraded, the requirements for rolling rolls are becoming more and more stringent, and the soundness of the outer shell layer needs to be higher than ever.

The present invention solves the above problems existing in the prior art and provides a centrifugal casting mold capable of producing a rolling roll having a sound outer shell layer, particularly an outer shell layer having no casting defect. The purpose is to do.

[0011]

In order to achieve the above object, the inventors of the present invention, when casting the molten metal forming the outer shell layer, do not instantly contact the molten metal at the initial stage of casting with the sand mold,
Moreover, the present invention has been achieved as a result of various researches on means for winding the inner surface of the mold rotating at high speed.

That is, according to the present invention, in a centrifugal casting mold having a sand mold part at an end of a mold part used for casting a cylinder or a cylindrical body, a fugitive shield is provided at a boundary part between the mold part and the sand mold part. It is a centrifugal casting mold provided. The fugitive shield has a disk shape with its central portion closed or open. It should be noted that the one in which the central part of the fugitive shield is in an open state (donut shape) makes it possible to insert the casting nozzle into the cavity when it is provided mainly on the casting port side of the molten metal. There is no problem if you use a small opening on the side.

[0013]

EXAMPLES AND OPERATION The centrifugal casting mold of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of an embodiment of a centrifugal casting mold of the present invention used for producing a rolling composite roll (solid roll) composed of an outer shell layer and a core material. FIG. 2 is a vertical sectional view of another embodiment of the centrifugal casting mold of the present invention, which is used for manufacturing a hollow sleeve roll. In the centrifugal casting mold shown in FIG. 1, a cavity 6 is formed in the mold by a mold part 1 having both ends opened, sand mold parts 2 and 3 connected to the both ends, and end covers 4 and 5. The inner surfaces of the sand mold parts 2 and 3 are formed into R (curved surface) because they form the shaft part of the solid roll in a later step.

Reference numerals 8 and 9 denote disc-shaped vanishing shields in which the cavity in the centrifugal casting mold is mounted in a closed state, which is the main constituent element of the present invention and which is the outer shell of the inner surface of the mold part 1. Layer 7
Is attached to the end portion that forms the mold, that is, the boundary portion between the mold portion 1 and the sand mold portions 2 and 3. This attachment is adhered to the boundary surfaces 21 and 31 of the sand mold portions 2 and 3 with glue or the like. As the quality of the paste, a commercially available ordinary paste can be applied sufficiently, and the bonded disc-shaped disappearing shield does not peel off. The vanishing shield 9 disposed on the casting port side is formed with an opening (donut shape) at the center in order to insert the casting nozzle into the cavity 6 during casting.

The molten outer shell layer cast to form the outer shell layer 7 passes through the inner surface of the mold part 1 (usually coated with a coating material of 2 to 3 mm), and as shown in FIG. It collides with the disc-shaped disappearing shield 8 shown. When the disappearing shield 8 is made of paper such as corrugated cardboard, the cast molten metal does not adhere to the paper and instantaneously flows on the paper surface and does not cause insertion into the paper surface. For this reason, the molten metal is subjected to the centrifugal force of the mold rotating at a high speed while instantaneously flowing for several tens of seconds on the paper surface, and is inverted on the disk-shaped disappearing shield 8 to be turned over to the mold part. Wrap around the inner surface of 1. It is a problem of the operation of the molten metal flow within a very short time of several tens of seconds.
It is possible to prevent the molten metal from coming into contact with the sand mold portion 2 to cause casting burrs and seizure. When the fugitive shield is a plate-shaped paper, it completely burns and burns to disappear within about 1 minute, and no harmful gas is generated.

Further, even when a part of the molten metal moved while being wound around the inner surface of the die part 1 reaches the doughnut-shaped disappearing shield 9 mounted on the casting side, it is similar to the above-described operation of the molten metal flow. However, since the molten metal that has reached the casting side is already in tune with the rotation of the mold, collision is not a strong force. Of course, the disappearing shield 9 also burns and disappears. I mentioned the paper dissipative shield as an example,
It may be a material capable of instantaneously blocking the cast molten metal and burning and disappearing, for example, a wood board such as a plywood board or a thin mild steel plate. Further, paper quality may be sprayed or applied on the surfaces of the sand molds 2 and 3 to form a disappearing shield.
However, it is dangerous to use a substance that emits harmful gas or an explosive substance. Further, it is not preferable to change the composition of the molten metal.

In another embodiment of the centrifugal casting mold of the present invention shown in FIG. 2, the overall structure of the mold is almost the same as that of FIG. However, since it can be used for sleeve roll production,
Since the shaft portion is not required, the inner surface shape of the sand mold portions 2 and 3 is not formed to be R (curved surface). The relationship between the operation of the flow of the cast molten metal and the disappearance shields 8 and 9 is the same as that described in FIG.

[0018]

[Table 1]

(Example 1) Using a mold having an inner diameter of 785 mm and a body length of 2700 mm, the outer shell molten metal having the composition of the present invention shown in Table 1 was cast into a centrifugal casting mold shown in FIG.
A molten metal amount of 4500 kg was cast at 0 ° C., and pouring was performed while paying attention so as not to cause a tab of the molten metal or a turbulent flow during casting. The mold rotation speed was 120 G (about 600 rpm). Further, the thickness of the paper disk-shaped disappearing shield was 4 mm. After casting, after a lapse of a predetermined time, the mold was disassembled, and a ring-shaped sample having a thickness of 15 mm and a depth of 50 mm was cut and sampled from both ends of the body of the as-cast roll, and as a result of macroscopic inspection and macro etching, no abnormality was found. I was not able to admit. Moreover, the outer periphery of the as-cast roll body was cut and the ultrasonic internal flaw detection was performed, but no abnormality was found in the outer shell layer.

(Comparative Example 1) The outer shell molten metal having the composition of the conventional example shown in Table 1 was cast under the same conditions as in Example 1 and poured into the conventional centrifugal casting mold shown in FIG. As in Example 1, the mold was disassembled after a predetermined time had passed, and the same inspection was performed.
A large number of casting defects, which are considered to be caused by re-melting of casting burrs such as burrs and scratches and seizure, were detected within 15 to 20 mm from the surface of the as-cast roll.

(Example 2) The outer shell molten metal having the composition of the present invention shown in Table 1 was poured into the centrifugal casting mold shown in Fig. 2 under the same casting conditions as in Example 1. As a result of the same examination as in Example 1, no abnormality was found.

As can be understood from the above description, in the present invention, the initial molten metal cast is subjected to centrifugal force without instantaneous contact with the sand mold portion, particularly the sand mold portion on the melt casting direction side. The outer shell layer is formed by wrapping around the inner surface of the mold while reversing from the surface of the disappearing shield while synchronizing with each other, so that no casting burrs or seizure with sand is generated, and casting defects such as blowholes or foreign matter entrapment occur. It is possible to form a shell layer without

[0023]

INDUSTRIAL APPLICABILITY The present invention prevents the molten metal at the initial stage of casting from contacting the sand mold portion instantaneously by the flow operation of the molten metal peculiar to the centrifugal casting method of a cylinder or a cylindrical body, so that a rolling roll having no casting defect can be obtained. An outer shell layer can be produced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of a centrifugal casting mold for producing a rolling composite roll according to the present invention.

FIG. 2 is a vertical cross-sectional view of another embodiment of a centrifugal casting mold for producing a sleeve roll according to the present invention.

FIG. 3 is a vertical cross-sectional view of an example of a centrifugal casting mold for producing a conventional rolling composite roll.

[Explanation of symbols]

 1 Mold part 2 Sand mold part 3 Sand mold part 4 End cover 5 End cover 6 Cavity 7 Outer shell layer 8 Disappearing shield 9 Disappearing shield 21 Sand mold part boundary surface 31 Sand mold part boundary surface A Casting of molten metal Direction B Molten metal movement direction

Claims (2)

[Claims] 1. A centrifugal casting mold having a sand mold part at an end of a mold part used for casting a cylinder or a cylindrical body, wherein a fugitive shield is provided at a boundary part between the mold part and the sand mold part. A mold for centrifugal casting characterized by: 2. The disappearing shield has a disk shape whose central portion is in a closed state or an open state.
The described centrifugal casting mold.