JPH09141409A - Metallic mold for centrifugal casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that defective products are produced since the defective parts such as shrinkage hole, segregation of impurities is liable to concentrate near the center part of the metallic mold in the metallic mold for centrifugal casting to form a casting tube by casting molten metal into the inner part, and to efficiently use a material by positively forming the defective part at the end parts of the casting products thereby cutting only the end parts thereof. SOLUTION: The thickness of the cylindrical metallic mold body 1 in the metallic mold for centrifugal casting to form the casting tube by casting the molten metal in the inner part is changed so as to be gradually thickened from one end part 1a side to the other end part 1b side of the metallic mold body 1. Further, an outer cylinder 2 is fitted externally to the metallic mold body 1 while holding a gap G and the one end part 1a of the metallic mold body 1 is formed with a sand mold S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal casting mold for casting a molten metal inside to form a casting pipe.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned centrifugal casting mold has a casting portion whose wall thickness is constant in the lengthwise direction, and at the same temperature, heat is released from the casting mold to the outside and casting is performed. The heat absorption from the metal to the mold was approximately equal over the entire length of the mold.

[0003]

DISCLOSURE OF THE INVENTION In the above-mentioned conventional centrifugal casting mold, at the end of the mold, heat is dissipated from the opening of the end of the mold, which results in a difference in heat dissipation of the cast metal. As the temperature of the cast metal at the end of the mold decreases faster and the temperature becomes lower than the inside, the final solidification position moves toward the center of the mold, and defects such as shrinkage cavities and segregation of impurities are generated in this final solidification. There is a tendency to concentrate on the position, and in order to remove such defects, it was necessary to cut the inner surface over the entire length of the casting pipe, casting with a large excess of thickness, and at the same time the depth of the defects However, there is a problem in that the occurrence of defective products is induced when the depth becomes abnormally deep. In order to solve this problem, as shown in FIG. 5 (a), the diameter of the casting surface of the die on the casting side is expanded, and a thick wall portion 8a is formed on the casting side of the cast casting pipe 8. The molten metal pool formed in this portion is used as the final solidification portion 9, and the inner surface of the casting pipe corresponding to the depth of that portion is deleted to the position of the one-dot chain line shown in FIG. 5B to remove the defective portion. Although the outer surface of the expanded diameter portion has been removed, there are many removed portions and much material is wasted. Therefore, an object of the present invention is to solve the above problems,
Centrifugal casting enables the defective parts to be positively formed at the ends of the cast product, cutting out only that end, thereby eliminating waste of material and at the same time enabling stable quality centrifugal cast products to be supplied. It is in the place of providing molds.

[0004]

The feature of the present invention for the above object is that the wall thickness of the cylindrical mold body gradually increases from one end side to the other end side of the mold body. Is changed (corresponding to claim 1). In this way, by changing the wall thickness of the mold, the heat absorption amount of the mold when the molten metal is cast into the mold can be positionally changed in the longitudinal direction of the mold. The heat absorption amount can be gradually increased from one end side to the other end side of the mold body. Therefore, when the molten metal is cast into the mold body, the cooling rate of the cast metal can be made larger on the other end side than on the one end side,
You. Therefore, when the molten metal is cast into the mold body from the one end side, the temperature gradient of the cast metal, which is gradually lowered from the one end side to the other end side, is further expanded. Thus, the solidification direction of the cast metal can be biased from the other end side to the one end side. As a result of directional solidification in this way, the final solidification position can be localized at the one end without changing the thickness of the cast product, and the defective portion is positively formed at the one end. Therefore, by cutting off the one end, only the sound part of the casting pipe can be left.
Therefore, the inner surface cutting for removing the defects of the cast product is not necessary, and the processing amount of the cast product can be extremely small, and at the same time, the cutting amount can be extremely small, so that the waste of the material can be omitted. The wall thickness of the mold body may be linearly changed in the lengthwise direction of the mold body (corresponding to claim 2). In addition to the simple shape, the cooling rate can be gently changed to give the cast metal a gentle temperature gradient. As a result, the solidification directions of the cast metal can be substantially aligned, and the final solidification position can be surely localized at the one end. Therefore, the excised portion can be shortened. Further, it is also preferable to form the outer surface of the mold body with a paraboloid of revolution (corresponding to claim 3).
Since the cross-section area of the die body exhibits a constant change in its longitudinal direction, the cooling rate, and hence the temperature gradient of the cast metal, can be made substantially constant. As a result, it is possible to manufacture a substantially homogeneous cast pipe while allowing directional solidification.
Further, it is more preferable that the outer cylinder is externally fitted (corresponding to claim 4) to the mold body while keeping a space. By doing so, it becomes easier to maintain the balance of the mold, and the present invention can be carried out without modifying the conventional centrifugal casting apparatus. Further, the gap may be configured so as to be gradually narrowed from the one end side to the other end side (corresponding to claim 5), and in this case, the heat insulating effect of the gap is obtained. It is possible to have a gradient that gradually decreases from the one end side to the other end side, and to have a change in heat absorption amount in the longitudinal direction of the mold body when the molten metal is cast into the mold body. You can As a result, the above effect can be obtained without increasing the difference in outer diameter between the one end and the other end of the mold body. In addition, the void may be configured to linearly change in the length direction of the mold body (corresponding to claim 6), and in this case, it can be combined with a mold body having a simple shape. The above effect can be obtained with an outer cylinder having a simple shape. As a result, it is possible to further improve the balance of the molds, and it is possible to obtain a casting pipe that has the desired directional solidification with a simple structure. Furthermore, it is more preferable that the one end of the mold body is formed by a sand mold (corresponding to claim 7). By doing so, it is possible to solidify the cast metal also with directivity in the pipe axis direction, and to form a molten metal pool at the one end formed by the sand mold, and further secure at the one end. Impurities can be captured. As a result, in addition to the above respective effects, a further effect that the material of the cast pipe can be improved is brought about.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a vertical sectional view of a mold of the present invention. The mold is composed of an outer cylinder 2 and a mold body 1 which is fitted in the outer cylinder 2 with a gap G therebetween. The inner peripheral surface of the mold body 1 has a central portion at both ends. A disc-shaped weir 4 having a circular opening is provided. The outer cylinder 2 is formed by processing the inner surface of a normal die into a tapered surface with one end having a small diameter and the other end having a large diameter, and has the same outer peripheral surface shape as a normal die. And has a diameter-expanded portion 3 parallel to the outer circumference thereof. The expanded diameter portion 3 is in contact with a support driving roller of the rotary drive table and is rotationally supported when the die is used. The mold body 1 has a cylindrical inner peripheral surface forming a mold surface, and an outer peripheral surface formed into a tapered surface having a small diameter on one end 1a side and a large diameter on the other end 1b side, The outer peripheral surfaces of both ends are joined to the outer cylinder 2 with the annular heat insulating coupling piece 5 interposed.
The other end portion 1b is fitted and fixed to the other end side of the outer cylinder 2 so as to coincide with the other end portion 1b. The mold body 1 is formed to have a length shorter than that of the outer cylinder 2, and extends from the one end portion 1 a of the mold body 1 to one end of the outer cylinder 2 and is continuous with the inner peripheral surface of the cylindrical shape. A sand mold S that forms the mold surface is formed. This sand mold S is the one end portion 1 of the mold body 1.
It is formed in place of the shortened portion of a. The inner diameter of the mold body 1, that is, the inner diameter of the mold surface is 400 mm.
And the wall thickness of the one end 1a of the mold body 1 is 30
mm and the thickness of the other end 1b is 70 mm, the outer diameter of the one end 1a is 460 mm, and the other end 1 is
The outer diameter of b is 540 mm. And the outer cylinder 2
Has an outer diameter of 600 mm, an inner diameter on one end side of 470 mm, and an inner diameter on the other end side of 545 mm. Therefore, the gap G
Is 2.5 mm on the side of the other end 1b and 5 mm on the side of the one end 1a, and the width of the gap G is larger on the side of the one end 1a than on the side of the other end 1b. . As a result of casting using this mold, the inner surface has a very smooth property, and the impurity layer on the inner surface in the thickness direction is about 8% of the wall thickness in the normal direction, while it is about 6%. I was able to. Although the final solidified layer was formed in the sand mold S, the inclination of the casting crystal was not known from the other end 1b side of the mold body 1 toward the one end 1a. The casting conditions were determined such that the weight was 30 mm in wall thickness, the material was low carbon steel, and the molten steel temperature during casting was 1600 ° C. The minimum width of the gap G is 2.5 mm because it is thicker than the thermal expansion margin and the thickness of the heat transfer boundary layer. The relation between the width of the gap G and the heat transfer coefficient of the gap G is shown in FIG. This is for easy understanding, and the void effect can be obtained even with a void thickness less than this.

Next, another embodiment of the invention will be described. <1> It is also effective to form the outer surface of the mold body with a paraboloid of revolution as shown in FIG. This shape is a linear distribution of the heat absorption of the mold body in the longitudinal direction.
In addition, it is possible to increase sequentially from one end side of the mold body to the other end side. Further, when the distribution of the heat absorption amount of the mold body is made non-linear, the outer surface shape may be designed in accordance with the distribution. <2> In the above embodiment, one end side of the mold body was replaced with a sand mold, but the entire length may be formed by the mold body,
If a sufficient space is provided between the outer cylinder and the outer cylinder, almost the same result can be obtained. As shown in FIG. 3, the same effect can be obtained even if the voids are uniform. <3> In the previous embodiment, the outer cylinder is provided, but the mold body may be provided with a portion adapted to the rotation support mechanism as in the expanded diameter portion. In this case, in order to prevent an increase in heat absorption of the expanded diameter portion 3, the heat retaining portion A composed of a void continuous in the circumferential direction.
Is effective in causing directional solidification.
The outer cylinder is effective for making the weight distribution of the mold in the longitudinal direction substantially uniform.

[0007]

As a result of the above, according to the present invention, it is possible to supply a centrifugally cast product of stable quality while eliminating waste of material.

[0008] In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view illustrating an embodiment of a centrifugal casting mold of the present invention.

FIG. 2 is a schematic vertical sectional view for explaining another embodiment of the centrifugal casting mold of the present invention.

FIG. 3 is a schematic vertical sectional view for explaining another embodiment of the centrifugal casting mold of the present invention.

FIG. 4 is a schematic vertical sectional view for explaining another embodiment of the centrifugal casting mold of the present invention.

FIG. 5 is a schematic vertical sectional view for explaining a conventional centrifugal casting mold.

[Explanation of symbols]

 1 Mold Main Body 1a One End of Mold Main Body 1b Other End of Mold Main Body 2 Outer Cylinder G Gap S Sand Mold

Claims (7)

[Claims] 1. A centrifugal casting mold for casting a molten metal inside to form a casting pipe, wherein the wall thickness of a cylindrical mold body (1) is the same as that of the mold body (1). A centrifugal casting mold in which the thickness gradually changes from the one end (1a) side to the other end (1b) side. 2. The mold for centrifugal casting according to claim 1, wherein the wall thickness of the mold body (1) is changed linearly in the length direction of the mold body (1). 3. The mold for centrifugal casting according to claim 1, wherein the outer surface of the mold body (1) is formed with a paraboloid of revolution. 4. A mold for centrifugal casting, wherein an outer cylinder (2) is fitted onto the mold body (1) according to any one of claims 1 to 3 while keeping a gap (G). 5. The end portion (1a) is defined by the gap (G).
The centrifugal casting mold according to claim 4, wherein the mold is changed so as to become gradually narrower from the side to the other end (1b) side. 6. The mold body (1) is provided with the gap (G).
The centrifugal casting mold according to claim 5, wherein the mold is linearly changed in the length direction. 7. The one end (1) of the mold body (1)
The centrifugal casting mold according to any one of claims 4 to 6, wherein a) is formed by a sand mold (S).