JPH10277719A - Metallic mold for centrifugal casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the invasion of molten metal into holes and the spattering of molten metal from the holes and also, the gas defect with gas venting effect of the holes by arranging many small holes penetrated in the radial direction of a cylindrical metallic mold and having specific range of diameter in a specific length from the inner surface of the metallic mold wall. SOLUTION: The diameter of the small hole 3 arranged so as to penetrate in the radial direction on the metallic mold wall 2, is adjusted to in the range of 0.5-3 mm to the length of 3 mm from the inner peripheral surface 2a of the metallic mold wall 2 toward the outer peripheral side. The small holes 3 can be arranged on the whole body or a part of the metallic body 1 and is desirable to arrange in the mutual interval of 50-250 mm. It is desirable that the diameter of the small hole is set to be large to >=3 mm at the part exceeding 3 mm from the inner peripheral surface 2a of the small hole 3 and at the time of remachining the inner surface of the metallic mold 1, the small hole can be closed by screwing a bolt, etc., so that cutting oil does not spout to the outer part from the small hole 3. The shape of the small hole 3 can be used as the straight or the tapered state in the diameter range of 0.3-3 mm. By this constitution, the inexpensive metallic mold for centrifugal casting is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal centrifugal casting mold used for centrifugal casting of steel pipes, cast iron pipes and the like.

[0002]

2. Description of the Related Art Conventionally, a centrifugal casting method in which a molten metal is poured into a rotating mold and a casting tube is manufactured by the action of centrifugal force can provide a product with accurate dimensions and high density. It is also applied to non-ferrous alloys.

[0003] In such a centrifugal casting method, defects are liable to occur in the obtained cast tube due to gas generated from the molten metal, the coating film, the mold surface and the like during casting. These gas defects are concentrated on the outer peripheral surface of the casting tube, and therefore, there is a problem that a casting tube satisfying the required quality cannot be manufactured or the yield is remarkably reduced.

In particular, in a horizontal centrifugal casting method in which a casting mold is installed horizontally or slightly inclined, gas generated at the time of casting passes through the molten metal and is discharged to the inner surface side, or There is no choice but to release to the end face side after passing through the coating layer. For this reason, there has been a defect that the gas is not sufficiently released, and gas defects are easily generated.

[0005]

As a method for eliminating the occurrence of gas defects in such centrifugal casting, it is conceivable to form a gas vent hole in a mold. However, when a hole is provided in a mold that rotates at a high speed, there is a major disadvantage that the molten metal passes through the hole and scatters outside due to centrifugal force applied to the molten metal. In addition, there are problems that the molten metal invading the holes hinders the effect of degassing and makes it impossible to pull out the casting tube from the mold.

Therefore, as described in Japanese Patent Application Laid-Open No. 53-94220, a metal screw having a vertical groove for gas discharge is attached to a hole formed in a mold, or a gas-permeable porous material is used. It has been proposed to screw refractories. Further, Japanese Patent Publication No. 54-44647 discloses that after filling a vent for venting with a slurry containing a refractory powder, it is dried and then filled with a gas-permeable filling. Further, Japanese Patent Application Laid-Open No. 54-143730 proposes that a gas vent hole is closed by thermal spraying of metal or ceramics to provide air permeability.

However, any of the above-mentioned methods is a method of refilling the hole formed in the mold by some means, and as a result, the effect of degassing is not sufficient, and the generation of gas defects is completely eliminated. It was difficult. In addition, the number of steps of backfilling the holes formed in the mold is increased, so that the operation is complicated and there is a problem that the cost of the centrifugally cast tube is increased.

The present invention has been made in view of such a conventional situation,
There is no need to backfill the gas vent holes drilled in the mold,
It is an object of the present invention to provide an inexpensive centrifugal casting mold that can prevent molten metal from entering a hole or scattering from a hole and can eliminate generation of gas defects by a sufficient gas releasing effect.

[0009]

In order to achieve the above object, a centrifugal casting mold provided by the present invention has a large number of small holes penetrating a cylindrical mold wall in a radial direction. The diameter is 0.5 to 3 m from the inner peripheral surface of the mold wall to the length of 3 mm.
m.

[0010] In the centrifugal casting mold of the present invention, the small holes may be provided in the whole or a part of the mold, and the small holes are preferably arranged at an interval of 50 to 250 mm. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, by improving the shape of the small holes provided in the mold, the molten metal can enter the small holes without refilling the small holes with some kind of filler as in the prior art. It does not drip or splatter out of the small holes. In addition, since the gas generated at the time of casting easily passes through the small holes and is discharged to the outside, a sound product without gas defects on the outer surface of the centrifugally cast tube can be obtained.

That is, as shown in FIG.
The diameter of the small hole 3 penetrating through the mold wall 2 in the radial direction is set in a range of 0.5 to 3 mm from the inner peripheral surface 2a of the mold wall 2 to a length of 3 mm on the outer peripheral side. Adjust within. Therefore, if the diameter of the small hole 3 is within a range of 0.5 to 3 mm in a portion from the inner circumferential surface 2a of the mold wall 2 to the outer circumferential side to 3 mm, the diameter of the small hole 3 may be constant or change. good.

The portion of the small hole 3 exceeding 3 mm from the inner peripheral surface 2a has a diameter of 3 mm so that the hole can be easily drilled.
It is possible to set larger than above. Also, in the centrifugal casting mold, the inner surface of the mold 1 may be re-cut after casting. In this case, the inner peripheral surface 2a of the small hole 3 should be cut from the small hole 3 so that the cutting oil does not blow out from the small hole 3 to the outside. It is preferable to cut a screw into a portion exceeding 3 mm and screw a bolt or the like so that the small hole 3 can be closed.

Specifically, the shape of the small hole will be described with reference to FIGS. First, FIG. 2 shows a straight small hole 3. The diameter of the small hole 3 is from 0.5 mm to 3 mm from the diameter a on the inner peripheral surface 2a of the mold wall 2 to the diameter b on the outer peripheral surface 2b. Is constant within the range. The small hole 3 in FIG. 3 is tapered, and its diameter gradually increases from the inner peripheral surface 2a to the outer peripheral surface 2b. In this case, the diameter a at the inner peripheral surface 2a and the inner peripheral surface 2a
It suffices that the diameter from the length to 3 mm is within the range of 0.5 to 3 mm.

FIG. 4 shows a shape combining a straight and a taper, and FIG. 5 shows a shape combining straight holes having different diameters. In these cases, the diameter a of the inner peripheral surface 2a is in the range of 0.5 to 3 mm, and the length c of the small hole portion 3a having this constant diameter is 3 mm or more from the inner peripheral surface 2a. is required. As long as this condition is satisfied, the diameter b at the outer peripheral surface 2b (that is, the diameter b of the enlarged hole portion 3b) is not particularly limited.

Further, the small hole shown in FIGS. 6 and 7 has a shape in which a connection hole portion 3c whose diameter gradually increases is provided between the small hole portion 3a and the enlarged hole portion 3b shown in FIG. 6 has a straight funnel shape in FIG. 6, whereas in FIG. 7, the funnel shape has a curved surface. Also in the case of these shapes, the diameter a on the inner peripheral surface 2a is 0.5 to 0.5.
The length c of the small hole portion 3a within the range of 3 mm is
It suffices that the distance from a is 3 mm or more, and the shape and dimensions of the other parts are not particularly limited.

In the present invention, the shape and dimensions of the small holes provided in the mold are limited as described above for the following reasons. That is, if the diameter of the small holes is less than 0.5 mm, the degassing is not sufficiently performed, and even if the interval between the small holes is reduced and the number of the small holes is increased, generation of gas defects cannot be avoided. Also,
At present, a technique for drilling a small hole having a diameter of 0.5 mm or less is not common, and drilling such a small hole is economically disadvantageous. On the other hand, if the diameter of the small hole exceeds 3 mm, the molten metal easily penetrates into the small hole, thereby hindering the effect of degassing, and furthermore, there is a danger that the molten metal may scatter outside from the small hole. Therefore, in this case, it becomes difficult to pull out the casting tube from the mold, and gas defects occur on the surface of the obtained casting tube.

Furthermore, at the same time that the diameter of the small hole satisfies the above condition, at least 3 m from the inner circumferential surface of the mold wall to the outer circumferential direction.
For length m, the diameter must be kept in the range of 0.5 to 3 mm. That is, the diameter of the small hole on the inner peripheral surface is
Even if it is within the range of 0.5 to 3 mm, it is 3 mm from the inner peripheral surface.
If the diameter is larger than 3 mm within 3 mm, the intrusion or scattering of the molten metal is likely to occur, and a sound cast tube without gas defects cannot be obtained. In addition, since deeply piercing a small hole having a diameter of 3 mm or less leads to an increase in cost, from this point, it is preferable to increase the diameter of the small hole in a portion exceeding 3 mm from the inner peripheral surface.

The interval between the small holes is preferably 50 to 250 mm. If the distance between the small holes exceeds 250 mm, the effect of degassing is reduced irrespective of the diameter, and gas defects are likely to occur. Conversely, if the interval between the small holes is narrower than 50 mm, the degassing effect is no longer improved, and the cost increases as the number of small holes increases, which is not preferable. Further, since the occurrence of gas defects varies depending on the material of the steel or non-ferrous alloy to be centrifugally cast, the interval between the small holes may be determined in the range of 50 to 250 mm according to the material. In other words, when casting a metal that does not easily generate gas defects due to easy gas discharge, the installation interval of the small holes is increased, and conversely, for a metal that easily generates gas defects, the installation interval is reduced.

Further, in a metal in which gas defects are easily generated,
Since gas defects occur in the entire casting tube obtained by centrifugal casting, it is difficult to eliminate gas defects unless small holes are arranged in the entire die. However, in the case of a metal in which gas defects are unlikely to occur, it is sufficient to dispose the small holes only in places where the gas defects are likely to occur, generally, at both ends of the mold. It is possible to suppress the occurrence.

Incidentally, the material and dimensions of the centrifugal casting mold in the present invention are not particularly limited, and can be appropriately selected according to the casting tube to be manufactured as in the conventional case. Further, the specific method and conditions of the centrifugal casting are not particularly limited, and can be appropriately selected according to the material of the casting tube to be manufactured as usual.

[0022]

EXAMPLE Using a mold having an inner diameter of 180 mm, an outer diameter of 500 mm, and a length of 3000 mm, a number of small holes were drilled in this mold, and a centrifugally cast tube having a thickness of 11 mm was manufactured by horizontal centrifugal casting. As a comparative example, a centrifugally cast tube was manufactured in the same manner as described above except that the small holes were not provided. In addition, the material of the manufactured casting pipe was three types shown in the following Table 1.

[0023]

TABLE 1 Material C Si Mn Ni Cr Co W P S Fe Cast iron 3.71 1.82 0.55 0.02 0.08 0.01 0.01 0.12 0.080 balance alloys A 0.71 of chemical group formed of cast tube Casting tube (wt%) 0.70 0.53 33.14 0.09 5.02 0.01 0.010 0.009 balance Alloy B 0.28 0.55 0.63 48.24 35.32 0.24 14.26 0.009 0.010 balance Note: Alloy A in the table is Fe-Ni-Co alloy, and Alloy B is Fe-Ni-Cr alloy.

In the mold having the small holes, all the small holes have the shape shown in FIG. 5, and the diameter a of the small hole portion 3a on the inner peripheral surface side of the small hole portion 3a where the constant diameter a is continuous. Inner peripheral surface 2a
, And the installation interval of the small hole portion 3a were changed as shown in Table 2 below. The “range” in Table 2
Column indicates the installation range of the small hole, and “whole” indicates the entire mold,
“Partially” means that small holes were provided only within a range of 500 mm from both ends of the mold.

At the time of centrifugal casting, a silica-based coating film was formed on the inner peripheral surface of each of the above-described molds as usual, and then attached to a horizontal centrifugal casting apparatus. On the other hand, 200 kg of each alloy material in Table 1 was melted in the air in a high-frequency induction furnace, and the molten metal was injected into a mold preheated to 200 to 250 ° C.
Centrifugal casting was performed by rotating the mold at a rotation speed of 1000 rpm. The temperature of pouring each molten metal into the mold was 1400 ° C. for cast iron, Fe—Ni—Co alloy and Fe—Ni—C
The temperature was set to 1500 ° C. for the r alloy.

With respect to each of the centrifugally cast tubes manufactured as described above, the state of occurrence of gas defects was evaluated in the same manner as in the prior art. That is, the presence / absence and amount of gas defects on the outer peripheral surface were confirmed by a penetration test, and the presence / absence of gas leakage from the gas defects was measured by an airtight test. The results are shown in Table 2 below.

[0027]

TABLE 2 whether 1 * Cast iron material diameter a length c interval range defect occurrence leakage between the shape of the casting tube ostium Installation penetrant leak test sample - - - - defects often leaks often 2 * Alloy A----Very much Very much 3 * Alloy B----Somewhat slightly 4 * Alloy A 3.5mm 10mm 200mm whole Very much very much 5 * Alloy A 2.0mm 10mm 300mm whole slightly generated slightly Yes 6 Cast iron 1.5mm 10mm 200mm Overall No defect No leak 7 Alloy A 3.0mm 10mm 200mm Overall No defect No leak 8 Alloy A 2.5mm 10mm 200mm Overall No defect No leak 9 Alloy A 1.5mm 10mm 200mm Overall No defect No leak 10 Alloy A 0.5mm 10mm 150mm Overall No defect No leakage 11 Alloy A 1.5mm 10mm 250mm Overall No defect No leakage 12 Alloy A 1.5mm 5mm 200mm Overall No defect No leakage 13 Alloy A 1.5mm 150mm 200mm Overall No defect No leakage 14 Alloy B 1.5 mm 10mm 200mm Part No defect No leakage (Note) Samples marked with * in the table are comparative examples.

As can be seen from the above results, in Samples 1 to 3 of Comparative Examples using a mold having no small holes, many gas defects were generated, gas leakage was large due to an airtight test, and a sound product was obtained. I couldn't get it. Especially Fe-Ni-C
In Sample 2 in which the o-alloy was cast, generation of gas defects was extremely large.

The diameter a on the inner peripheral surface side of the small hole is set to 3.5.
In sample 4 of the comparative example using a mold having a size as large as mm, the molten metal penetrated into the small holes due to the centrifugal force and hindered the effect of degassing. Gas defects occurred frequently, and it was difficult to remove the product from the mold.

On the other hand, the centrifugally cast tubes of Samples 6 to 14 using the mold according to the present invention were free from gas defects and gas leaks, and all were sound products. Further, there was almost no intrusion of the molten metal into the small holes, and the product was easily pulled out from the mold. In particular, Fe-N
Since the i-Cr alloy is a material that does not easily generate gas defects, it was possible to eliminate the generation of gas defects only by providing small holes at both ends of a mold where gas defects are likely to occur.

However, the diameter of the small hole on the inner peripheral surface is in the range of 0.5 to 3 mm and the length from the inner peripheral surface is 3 m.
m, the casting tube is made of a Fe-Ni-Co alloy in which gas defects are apt to occur, so that in Sample 5, in which the interval between the small holes was increased to 300 mm, The generation of some gas defects was observed between the small holes.

[0032]

According to the present invention, the molten metal does not enter into the small holes formed in the mold or scatter outside from the small holes, and the gas passes through the small holes of the mold. Since the gas is reliably discharged to the outside, a sound centrifugally cast pipe having almost no gas defects can be obtained.

Moreover, since it is not necessary to fill back the small holes formed in the mold with a filler or the like as in the prior art, the manufacture of the mold is simple, and therefore, the centrifugal casting tube is extremely efficient at low cost. Can be cast.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a specific example of a mold having a small hole according to the present invention.

FIG. 2 is a cross-sectional view showing a specific shape of a small hole provided in a mold according to the present invention.

FIG. 3 is a cross-sectional view showing a specific shape of a small hole provided in a mold according to the present invention.

FIG. 4 is a cross-sectional view showing a specific shape of a small hole provided in a mold according to the present invention.

FIG. 5 is a sectional view showing a specific shape of a small hole provided in a mold according to the present invention.

FIG. 6 is a sectional view showing a specific shape of a small hole provided in a mold according to the present invention.

FIG. 7 is a sectional view showing a specific shape of a small hole provided in a mold according to the present invention.

[Description of Signs] 1 Mold 2 Mold wall 2a Inner peripheral surface 2b Outer peripheral surface 3 Small hole 3a Small hole portion 3b Enlarged hole portion 3c Connection hole portion a Diameter at inner peripheral surface b Diameter at outer peripheral surface c Small hole Length of

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshiro Ito 1860, Shimotsuruma-cho, Yamato-shi, Kanagawa Prefecture Inside Taihei Metal Industry Co., Ltd. (72) Inventor Tatsuhiko Kobayashi 2-1 Shiraishi-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa-ken Nippon Casting Co., Ltd. (72) Inventor Takuo Handa 2-1 Shiraishi-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Nippon Casting Co., Ltd. (72) Yutaka Matsumura 2-1 Shiraishi-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Nihon Casting Co., Ltd.

Claims (2)

[Claims] 1. A large number of small holes penetrating a cylindrical mold wall in a radial direction, and the diameter of the small holes is 3 mm from the inner peripheral surface of the mold wall.
A centrifugal casting mold having a length of 0.5 mm to 3 mm. 2. The centrifugal casting mold according to claim 1, wherein the small holes are provided at intervals of 50 to 250 mm on the whole or a part of the mold.