JP2000343193A - Centrifugal casting method and casting speed indicating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a casting with fine structure and uniform quality across entire thickness direction by making the casting speed of a thick portion as a specific range and inclining a ladle from data of the molten metal remaining quantity in the ladle and the casting speed. SOLUTION: In this centrifugal casting, casting speed is set to be 7-40 kg/see. It is preferable that a thick portion of at least 10 mm or more from the inner face of a centrifugal casting mold is cast at the casting speed of 7-40 kg/see. At that time, a computer 2 is installed in a control chamber 21. The computer 2 stores the measuring data inputted via a receiving device 3 at given time intervals by a processing program, and outputs the data to a display 5 in real time. Additionally, the required molten metal volume and the ladle metal remaining quantity against the casting elapsed time are computed at given time intervals from a preset data such as the casting speed inputted from a keyboard 4. The results are stored as the indication data and displayed on the display 5. The ladle 11 is inclined by the indication data so as to keep a given casting speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal casting method capable of obtaining a uniform fine structure throughout a casting layer, and a casting speed indicating device used for carrying out the method.

[0002]

2. Description of the Related Art Centrifugal casting is a method suitable for casting cylindrical castings such as pipes and outer layers of rolling rolls. The centrifugal casting method is generally performed by casting the molten metal in the ladle into a rotating centrifugal casting mold through a pouring gutter by tilting a ladle. Yes, the casting speed depends on the experience and intuition of the operator.
The casting speed was high at about kg / sec.

[0003]

However, as the thickness of the casting increases, the molten metal cast into the centrifugal casting mold becomes
In the vicinity of the inner surface of the mold, the layer is rapidly cooled and solidified by heat removal by the mold to become a layer having fine crystal grains, and also in the vicinity of the inner surface of the molten layer, a relatively fine structure is formed by cooling to the atmosphere. Since the intermediate portion hardly dissipates heat and delays solidification, crystal grains are likely to become large or segregate. For this reason, 70 to 100 kg is required from the beginning of casting to the end of casting.
/ Sec, it is difficult to obtain uniform physical properties along the radial direction. For example, in the outer layer of the roll, as the surface wears, a rough surface or uneven wear occurs on the roll surface. Is transferred to the material to be rolled, and the quality is impaired.

[0004] The present invention has been made in view of such a problem, and is intended for a thick cylindrical casting (roll, roller).
A centrifugal casting method capable of obtaining a uniform casting with a fine structure over the entire wall thickness by setting a casting speed (low speed casting) of 7 to 40 kg / sec and a method for easily performing the casting method An object is to provide an auxiliary device (a casting speed indicating device).

[0005]

According to a first aspect of the present invention, there is provided a centrifugal casting method comprising: casting a molten metal in a ladle into a centrifugal casting mold;
The casting speed is 7 to 40 kg / sec. The centrifugal casting method according to claim 2 is characterized in that a thick portion of at least 10 mm or more is cast from the inner surface of the centrifugal casting mold at a casting speed of 7 to 40 kg / sec.

Furthermore, the centrifugal casting method according to claim 3 is characterized in that a thick portion of at least 50 mm or more is cast from the inner surface of the centrifugal casting mold at a casting speed of 7 to 40 kg / sec. It is. Further, the casting speed display device according to claim 4 is a measuring means for measuring the remaining amount of the molten metal in the ladle, and stores the measurement data outputted from the measuring means and is inputted from the casting speed setting device. The computer calculates the remaining amount of the molten metal in the ladle with respect to the elapsed casting time based on the speed data obtained, and stores the instruction data obtained by the operation, and displays the instruction data and the measurement data output from the computer. And a display.

According to the present invention, the casting speed from the start of casting to the end of casting is 70 to 40 kg / sec.
The speed should be reduced to c. Thus, when the casting speed is reduced, the temperature of the molten metal in the ladle gradually decreases due to spontaneous release,
Low temperature molten metal is sequentially supplied into a centrifugal casting mold. Therefore, since the supply amount per unit time is small and the low-temperature molten metal is supplied, the melt supplied to the inner peripheral surface of the already solidified casting layer is rapidly cooled and solidified, and the casting layer having a fine structure is continuously formed. Can be grown.

According to a second aspect of the present invention, at least a thick portion having a thickness of 10 mm or more has a casting speed of 7 to 40 kg / sec.
In claim 3, the thickness of at least 50 mm or more is 7 mm.
The casting speed is about 40 kg / sec. In other words, from the inner surface of the centrifugal casting mold to about 50 mm, preferably up to about 10 mm, a quenching effect can be expected due to the cooling ability of the mold itself, and it is necessary to quickly spread the molten metal on the inner peripheral surface of the mold. The casting speed may be the same as the conventional casting speed, and a fine structure can be obtained even at such a casting speed.

If the thickness exceeds 50 mm, preferably 10 mm, a rapid cooling effect of the mold cannot be expected. Therefore, it is necessary to reduce the casting speed, and the casting speed is set to 7 to 40 kg / sec. If the heat capacity is less than 7 kg / sec, the heat capacity is small, so that solidification may start during casting. On the other hand, if it exceeds 40 kg / sec, the temperature drop of the molten metal in the ladle is small, and the calorie increases with respect to the heat release. For this reason, it is difficult to continuously grow the cast layer, and there is a possibility that crystal grains are coarsened in the cast layer. Further, according to the pouring speed display device according to the fourth aspect, at the time of pouring operation, the operator measures while following the instruction line of the instruction data displayed on the display of the pouring speed instruction device. By performing the tilting operation of the ladle so as to superimpose the measurement data of the remaining amount of molten metal in the ladle output at predetermined time intervals from the means, the casting speed can be easily determined without depending on experience or intuition. Can be secured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a casting speed indicating device for performing a casting operation at a predetermined casting speed when carrying out the centrifugal casting method of the present invention will be described. FIG. 1 is an overall configuration diagram of the casting speed indicating device. In a work place, a hanging scale 1 as an example of a measuring means is hung by a crane or a monorail, and a ladle 11 is mounted on a hook 2 of the hanging scale 1. Hanged. The ladle 11 is provided with a handle 12, and the operator rotates the handle 12 to
The ladle 11 is tilted via the gear mechanism, and the molten metal therein is cast into a centrifugal casting mold.

The hanging balance 1 measures the total weight of the ladle containing the molten metal, and determines the weight of the molten metal in the ladle, which is obtained by subtracting the weight of the ladle itself (tare) from the total weight, as measurement data at a predetermined time interval ( (Approximately 5 times / sec.) To make a call. A computer 2 is installed in the control room 21, and a measurement data receiving device 3 as an input device and a keyboard 4 for setting and inputting a casting speed, a casting outer diameter, a wall thickness, etc. are connected as input devices, and as an output device. CRT display 5 and printer 6
Is connected. In addition, the display 5 is installed in a work place.

The computer 2 stores the measurement data input via the receiving device 3 at predetermined time intervals and outputs the measurement data to the display 5 in real time according to the processing program. In addition, the required amount of molten metal and the remaining amount of the ladle with respect to the elapsed casting time are calculated at predetermined time intervals from setting data such as the casting speed input from the keyboard 4, and the result is stored as instruction data. Then, the instruction data is displayed on the display 5, and the measurement data at the time of starting the casting is matched with the instruction data, and then the measurement data is displayed in real time every moment. Incidentally, the casting start time, measurement data with a time varying predetermined amount, i.e. the difference between D ₂ which are then input to the data D ₁ of the certain point (D ₁ -D ₂₎ is equal to or greater than a predetermined amount when Is recognized inside the computer. Also, these data
The information is displayed on the display 5 and also recorded on the printer 4.

According to the casting speed indicating device, the operator only has to perform the tilting operation of the ladle 11 so as to overlap the measurement data along the indicating line of the indicating data displayed on the display 5. Can be easily ensured. In addition, since the actual casting curve is recorded by the printer 6, it is possible to take a measure against a defect in advance by seeing this record. For example, in the case of the casting curve B as shown in FIG.
It was found that the pouring amount per unit time was remarkably large in the initial stage of casting with respect to the indicator line A, and the mold on the inner surface of the mold was peeled off, and it was predicted that casting defects had occurred. It turns out that it needs to be inspected.

In FIG. 1, the ladle 11 is shown to be tilted by an operator's handle operation. However, a driving means such as a servomotor is provided so that the measurement data and the instruction data match according to the instruction line. Feedback control may be performed so that the tilting is performed according to a command from the computer. The casting method of the present invention is more effective for large castings. For example, in the case of an outer layer of a rolling roll, the outer diameter φ40
0 to φ850 mm, body length (length in outer layer axial direction) 1200 to 3
000 mm and a casting thickness of about 50 to 120 mm are good targets.

[0015] The centrifugal casting method can be applied to a mold for centrifugal casting in which the axis of rotation is horizontal or oblique. Hereinafter, specific casting examples will be described.

[0016]

Example 1 φ792 mm × L2700 mm, thickness 1
This is an example of casting of an outer layer of a roll of 00 mm. In both Example 1 and Conventional Example 1, a high-alloy grain cast iron melt having the following composition was melted at 1290 ° C. under G No. It was cast into a centrifugal casting mold rotating at 140. At the time of casting, the pointing device of FIG. 1 was used. FIG. 3 shows the casting results.
A is an instruction line of instruction data obtained by calculation, and B is an actual casting curve. In the first embodiment, the casting speed from the start of casting to the end of casting is 7 to 40 kg / sec. Specifically, as shown in FIG.
Low speed casting of 200 kg / casting time 140 sec) was performed. On the other hand, in Conventional Example 1, high-speed casting at 75 kg / sec was performed.

Molten composition of Example 1 (wt%) C; 3.33, Si; 0.69, Mni; 0.66
P; 0.031, Si; 0.016, Ni; 4.40,
Cr; 1.65, Mo; 0.42, balance Fe Melt composition of conventional example 1 (wt%) C: 3.30, Si; 0.72, Mni; 0.68,
P; 0.032, Si; 0.018, Ni; 4.43,
Cr: 1.68, Mo: 0.45, balance Fe After casting, for Example 1 and Conventional Example 1, the microstructure (50) at a position 25 mm from the casting surface (the inner surface of the mold) was obtained.
Times) was observed.

FIG. 4 shows the first embodiment, and FIG.
In Example 1, the crystal grains of the microstructure were fine, while in Conventional Example 1, the crystal grains were observed to be coarser than in Example 1. Of course, macrosegregation did not occur in the outer layer of Example 1, whereas macrosegregation was observed in some cases in Conventional Example 1.

[0019]

Embodiment 2 φ785 mm × L2100 mm, thickness 1
This is an example of casting of an outer layer of a roll of 00 mm. In both Example 2 and Conventional Example 2, a high-alloy grain cast iron melt having the following composition was melted at 1290 ° C. and G No. It was cast into a centrifugal casting mold rotating at 140. When pouring,
Using the pointing device of FIG. 1, the casting result is shown in FIG. 6, where A is the instruction data (target) obtained by the calculation.
Is the actual casting curve.

In the second embodiment, the casting speed from the start of casting to 6 seconds is set to a high speed casting of 60 kg / sec, and thereafter (at least a thick portion of 10 mm or more) is set to 24 k
g / sec at a low casting speed.
Was performed at a high speed casting speed of 65 kg / sec. Melt composition of Example 2 (wt%) C; 3.35, Si; 0.70, Mni; 0.65
P; 0.025, Si; 0.014, Ni; 4.39,
Cr: 1.65, Mo: 0.39, balance Fe The composition of the molten metal of the second example is the same as that of the first example.

After the casting, the microstructure (50 times) of Example 2 and Conventional Example 2 at a position 25 mm from the casting surface (the inner surface of the mold) was observed. FIG. 7 shows Example 2 and FIG. 8 shows Example 2 of the related art. In Example 2, the crystal grains of the microstructure were fine, whereas in Example 2 of the related art, the crystal grains were coarser than in Example 2. Is observed.

[0022]

Embodiment 3 φ785 mm × L2100 mm, thickness 1
This is an example of casting of an outer layer of a roll of 00 mm. In both Example 3 and Conventional Example 3, a high-alloy grain cast iron melt having the following composition was melted at 1290 ° C. under G No. It was cast into a centrifugal casting mold rotating at 140. At the time of casting, the casting result is shown in FIG. 9 using the pointing device of FIG.
In FIG. 6, A is an instruction line of instruction data obtained by calculation, and B is an actual casting curve.

In the third embodiment, 23 seconds from the start of casting.
Casting speed up to 65kg / sec high speed casting,
Then (at least 50 mm or more) 42 m in Example 3
The thick portion of m or more was cast at a low speed of 14 kg / sec, while in Conventional Example 3, it was cast at a high speed of 65 kg / sec. Melt composition (wt%) of Example 3 C; 3.33, Si; 0.75, Mni; 0.65
P; 0.033, Si; 0.016, Ni; 4.44,
Cr: 1.66, Mo: 0.40, balance Fe The molten metal composition of the third conventional example is the same as that of the first conventional example.

After casting, the casting surface and the microstructure of Example 3 and Conventional Example 3 are shown in FIGS.
The macro organization is shown in FIGS. 12 and 13, respectively. In Example 3, as shown in FIG. 10, it was observed that the microstructure of the casting surface 40 mm had finer crystal grains than that of Conventional Example 3 (see FIG. 11), while that of Conventional Example 3 was coarse. Example 3 also in the macro organization (see FIG. 12)
No macrosegregation was observed, and macrosegregation was observed in some places in Conventional Example 3 (FIG. 13).

[0025]

As described above in detail, according to the centrifugal casting method according to the present invention, the casting temperature per unit time corresponding to the temperature drop of the molten metal in the ladle and the heat radiation amount during the casting is determined. The cast molten metal can be solidified sequentially and continuously, the structure can be refined and homogenized over the entire thickness range of the casting, and the generation of macrosegregation due to solidification delay can be prevented. be able to. Further, according to the casting speed indicating device of the present invention, by performing the tilting operation of the ladle so as to overlap the measurement data along the instruction line displayed on the display and indicating the remaining amount of the molten metal in the ladle, It is possible to easily secure a predetermined casting speed, and to quantify a casting operation relying on experience and intuition.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a casting speed instruction device.

FIG. 2 is a graph showing a casting result.

FIG. 3 is a graph showing a casting effect of Example 1.

FIG. 4 is a metallographic photograph showing the microstructure of Example 1.

FIG. 5 is a metallographic photograph of a conventional example 1 in comparison with Example 1.

FIG. 6 is a graph showing a casting result of Example 2.

FIG. 7 is a metallographic photograph showing the microstructure of Example 2.

FIG. 8 is a photograph of a metallographic structure of a second conventional example in comparison with the second embodiment.

FIG. 9 is a graph showing the casting result of Example 3.

FIG. 10 is a metallographic photograph showing the microstructure of Example 3.

FIG. 11 is a photograph of the metallographic structure of Conventional Example 3 in comparison with Example 3.

FIG. 12 is a metallographic photograph showing the macrostructure of Example 3.

FIG. 13 is a photograph of the metallographic structure of Conventional Example 3 in comparison with Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measuring means (hanging scale) 2 Computer 5 Display 11 Ladle

Claims (4)

[Claims] 1. A centrifugal casting method in which a molten metal in a ladle is cast into a centrifugal casting mold and centrifugal casting is performed, wherein the casting speed is 7 to 40 kg / sec. 2. A method of casting a molten metal in a ladle into a centrifugal casting mold and performing centrifugal casting, wherein a portion having a thickness of at least 10 mm or more from the inner surface of the centrifugal casting mold is 7 to 40 kg / sec. A centrifugal casting method characterized by casting at a casting speed. 3. A method of casting a molten metal in a ladle into a centrifugal casting mold and performing centrifugal casting, wherein a wall thickness of at least 50 mm or more from the inner surface of the centrifugal casting mold is 7 to 40 kg / sec. A centrifugal casting method characterized by casting at a casting speed. 4. A measuring means for measuring the remaining amount of the molten metal in the ladle, and measuring data outputted from the measuring means,
A computer that calculates the remaining amount of molten metal in the ladle with respect to the elapsed casting time based on the speed data input from the casting speed setting device, and stores instruction data obtained by this calculation,
A display for displaying the instruction data and the measurement data output from the computer.