JPH0323046A - Centrifugal casting method and centrifugal casting apparatus used thereto - Google Patents

Abstract

PURPOSE:To reduce amplitude of vibration of a mold, to prevent the damage and to obtain a solidified body having high quality by automatically and gradually reducing number of revolution of the mold axially rotated with the prescribed deceleration since the time when molten steel poured therein starts to solidify. CONSTITUTION:The cylindrical shaped mold 1 is horizontally set on two pairs of supporting bases 3 composed of supporting column 3a and supporting roll 3b as freely fitting/removing. This mold 1 is axially rotated through a shaft 5 and the above supporting roll 3b with a motor 4. After applying parting agent on the inner wall of mold 1, the molten metal is poured therein from a tundish 6. This molten metal forms molten metal layer 7 on the inner wall of mold 1 with centrifugal force and solidified with cooling from the outer part. In the above centrifugal casting method, since the time when the above molten metal starts to solidify, by controlling the motor 4 with the prescribed program, the revolutional velocity of the mold 1 is reduced with the prescribed deceleration. By this method, it is restrained that the vibration of mold 1 is amplified by jumping-up of the solidified body in the mold 1 and the damage of mold 1 is prevented and the product having high quality without crack and abnormal solidified structure, etc., is cast.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a centrifugal casting method and a centrifugal casting apparatus used therein. (Conventional technology) The centrifugal casting method improves quality. It is widely used as a pipe manufacturing technology with excellent features in terms of productivity and economy. This centrifugal casting method is generally carried out using a centrifugal casting apparatus as illustrated in FIG. In the figure, a long cylindrical mold 1 is removably placed on four support stands 3 on which a ground 2 is installed. The support stand 3 includes pillars 3a. 3a and the support roll 3b located therebetween, and between support stands that support the mold 1 in front and behind,
A single shaft 5 connected to a rotary power machine 4 such as a motor is inserted. When operating this apparatus, first, the mold 1 is heated to a predetermined temperature in a heating furnace, and then taken out and placed on the support roll 3b of the support stand 3. Then, the rotational power l14 is activated. The rotational force through the shaft 5 causes the support roll 3b to rotate, thereby causing the mold 1 to rotate around its axis. The rotational speed of the mold 1 is increased, and at a predetermined point, a mold release agent is applied to the hollow inner surface of the mold 1 using a mold release agent coating device (not shown). After that, the rotation speed of mold 1 is further increased to put the device into standby mode for pouring. Then, molten metal is poured into the hollow interior of the mold 1 from the dan dish 6. The poured molten metal forms a molten metal layer 7 of a predetermined thickness by the action of centrifugal force, covering the already formed mold release agent layer. The rotational speed of the mold 1 at this time is determined by the coefficient of friction between the molten metal and the inner wall of the mold (the surface coated with the release agent), and the viscosity of the molten metal. It can be determined appropriately by considering various factors such as pouring speed. Next, while rotating the mold 1, a water shower is applied to the outer periphery of the mold 1 to cool the molten metal layer 7. The molten metal layer 7 solidifies as it cools. The formed solidified structure generally consists of chill crystals in the outermost layer (at the interface with the inner wall of the mold), then columnar products extending in the radial direction of the mold, and free crystals in the inner layer.

Finally, after the molten metal layer has completely cooled (completely solidified), the operation of the rotary motor 4 is stopped, the rotation of the mold 1 is stopped, and the tubular cast product is taken out and made into a product. (Problems to be Solved by the Invention) By the way, in the above-described centrifugal casting method, the molten metal poured into the mold contracts in the radial direction of the mold during the solidification process. Therefore, as the molten metal solidifies, the clearance between the outermost surface of the solidified body and the inner wall of the mold increases. Therefore, if the rotation speed of the mold is not reduced during the solidification process, the solidified material will begin to dance within the mold, amplifying the vibration of the mold, resulting in adverse effects on quality such as cracking and the formation of abnormal solidified structures, as well as on the mold and supporting parts. This can lead to serious damage. For this reason, first, during the solidification process, the operator observes the vibration state of the mold and, depending on the state, manually reduces the mold rotation speed in stages. ．． However, such work is subject to individual variations among workers and relies on the experience and intuition of workers, so it may cause variations in the quality W (solidified structure, etc.) of the resulting product. There are many. The object of the present invention is to provide a centrifugal casting method that solves these problems and enables stable operation and, therefore, casting of products with stable quality, and an apparatus used therefor. (Means for Solving the Problems) In order to achieve the above object, in the present invention, molten gold is poured into a mold that rotates, and from the time when the molten metal begins to solidify, a predetermined deceleration rate is applied. There is provided a centrifugal casting method characterized in that the number of rotations of the mold is automatically gradually reduced, and the mold into which the molten metal is poured is rotated on a rotating support roll connected to a rotary motor. The centrifugal casting device is equipped with a program mechanism for operating the rotary power machine so that the number of revolutions of the mold gradually decreases during the solidification process of the poured molten metal. A centrifugal casting device is provided. The method of the present invention is the same as the conventional method, except that the mold rotation speed is gradually reduced based on the commands of a pre-installed program during the solidification process of the molten metal.

In this case, the solidification rate of the molten metal poured into the mold changes depending on the type and amount of molten metal poured. Therefore, a program is created so that the manner in which the mold rotational speed is gradually decreased is changed depending on the type m and t of the poured molten metal. Normally, the rotation speed of the mold gradually decreases to follow the solidification speed of the molten metal.
A program operation may be performed to slow down the rotational speed of the mold approximately linearly.

In order to carry out such a program operation, the apparatus of the present invention, in the apparatus shown in FIG. It is sufficient to incorporate a program mechanism that issues a command to reduce the rotation speed. The program mechanism that issues commands to the rotary power machine includes a series of mold revolutions LIl from the startup of the device (start of centrifugal casting operation) to the end of device operation (@end of production).
According to this program, the rotational power f
You can also activate i4. (Function) According to the method of the present invention, the rotational speed of the mold is automatically reduced to follow the solidification speed of the molten metal, so the amplification of mold vibrations due to solidification contraction of the molten metal is reduced, and therefore the device At the same time, the degree of damage to the machine is reduced, and the operation is automated, eliminating the uncertainty of relying on the operator's intuition and experience. In addition, since the solidification of the molten metal progresses as the mold rotational speed gradually decreases, the solidification process is no longer subject to discontinuous external forces that accompany gradual changes in the mold rotational speed.
As a result, the quality of the resulting product is also stabilized. (Example) Below, a case will be described in which a steel pipe is manufactured using the centrifugal casting apparatus shown in Fig. 1. In FIG. 1, a rotary power machine 4 is configured to be able to change its rotational speed in response to commands from a program that rotates a mold 1 in a pattern as shown in FIG. In this embodiment, first, when preparation for pouring is completed (A), reloading is started to operate the rotary power machine 4, and its rotation is transmitted from the support roller 3b to the mold 1. Mold 1
gradually increases the rotation speed linearly until it reaches point B (5~20r).
Reach p-. Wait at this rotational speed to uniformly heat the mold 1 and support roller 3b. After that, the rotation speed of the mold 1 is changed from point C to point D (400 to 600 r), which is the rotation speed of pouring molten steel.
p■). The generated G at this time is 80G. Next, while maintaining this rotation speed, turn the tundish 6.
Pour a predetermined amount of molten steel into mold 1. By showering water on the outside of the mold l, the molten steel begins to cool and solidify from point E. Thereafter, by operating the rotary motor 4 based on the commands of the program, the rotational speed of the mold 1 is linearly decreased over a predetermined period of time, and G is increased to 2 during pouring.
Reduce it to 0-50%. After point F, the rotation speed of the mold 1 is maintained until the appropriate mold removal time, and then at point G, the rotation speed is linearly reduced and the rotation of the mold is stopped. 4. ? In the programming device, no amplification of mold vibration was observed during the E-F and F→G processes. In addition, the quality of the solidified structure of the obtained steel pipe was also good. (Effects of the Invention) As is clear from the above explanation, according to the method of the present invention, there is no need for manual operations that rely on the operator's intuition and experience as in the past. The mold automatically reduces its rotation speed. Therefore, the amplification of mold vibration is reduced and the risk of damage to the equipment is also reduced. In addition, the solidified structure of the obtained product is good and has little variation, making it possible to stabilize its quality. The apparatus of the present invention requires only a program for changing the rotational speed of the rotary power machine in a conventional centrifugal casting apparatus to be installed in a predetermined pattern, so that the burden on the equipment is small.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway side sectional view schematically showing the centrifugal casting device;
FIG. 2 is an example of a program pattern incorporated into the device of the present invention.

Claims (2)

[Claims] (1) A centrifugal casting method characterized by pouring molten metal into a axially rotating mold, and automatically gradually reducing the number of revolutions of the mold at a predetermined deceleration speed from the time the molten metal begins to solidify. . (2) In a centrifugal casting apparatus in which a mold into which molten metal is poured is rotatably mounted on a support roll that is connected to a rotary power machine and rotates, during the solidification process of the poured molten metal, A centrifugal casting apparatus characterized in that a program mechanism for operating the rotary power machine so that the rotational speed of the mold gradually decreases is incorporated.