JPS6015427B2 - Continuous casting method for cast iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuous casting of cast iron, in which a cast iron rod is manufactured by cooling and drawing hot water in a holding furnace.

Conventionally, the continuous casting method for cast iron as described above involves repeatedly pulling out a cast iron rod from a holding furnace at a constant speed during a drawing period, stopping the drawing operation, and maintaining the stopped state for a waiting period. was there. However, in such a method, the drawing time and waiting time are determined by the worker based on the worker's experience depending on the situation at the time, and therefore the product tends to vary due to individual differences. Further, in such a casting method, one worker must be assigned to each holding furnace, and a large number of workers are required. An object of the present invention is to provide a method for continuous casting of cast iron, which produces uniform product quality and does not require much manpower. In the casting method according to the present invention, one cycle consists of the process of pulling out the cast iron twill from a holding furnace at a constant speed and the waiting process of maintaining this drawn state, and the drawing time and time are determined according to the temperature of the drawn cast iron twill and a predetermined program. First, the drawer drawing process, start drawing process, and steady drawing process are performed in this order, and then, depending on the situation, the high temperature drawing process, low temperature drawing process, and Western hot water drawing process are performed, and at the end of the operation, the final drawing process is performed. Let's do it.

The steady cutting process is carried out when the temperature inside the holding furnace is almost stable, and the drawing time in the drawing process is set to te, which is predetermined according to the material, shape, and dimensions, and the waiting time in the waiting process is similarly set. A predetermined tw is set and this is repeated.

The draw-out process is for pulling out cast iron rods with initial slag at the start of operation, and is performed over a predetermined drawing time T or drawing cycle N, (approximately) as shown in FIGS. 2 and 3. 1
0 to 30 cycles), the drawing time te2 is maintained shorter than te (about 0.5 times) to shorten the stroke of the cast iron rod to be drawn, and the initial waiting time tw, which is sufficiently longer than tw, (approximately 1.5 to 5.0 times), and then decrease the samurai time sequentially for each cycle to increase the waiting time to tw2 (approximately 1.5 W to 2.5 tw) after T, time or N, cycle. ).

The start drawing process is carried out when transitioning from the drawer drawing process to a steady state, and the first half is a predetermined first half start time L or first half start cycle N2, in which the drawing time is changed from plan 2 to tancho next every cycle. Increase T2
After time or N2 cycles, the withdrawal time is set to te and the waiting time is maintained at t, and in the second half, the withdrawal time is maintained at te and the waiting time is maintained at a predetermined second half start time L' or the second half start cycle N2'. time per cycle tw
After L' time or N2' cycles, the power is decreased by 2 and then set to W, after which the steady state is established.

In the high-temperature drawing process, the high-temperature drawing time is set to m5 in order to prevent leakage when the maximum temperature of the drawn cast iron rod becomes, for example, 10°C to 20qo higher than the maximum temperature in the steady state.
Alternatively, during the high temperature drawing cycle N5 (approximately 10 to 30 cycles), the drawing time is maintained at te, but the waiting time is tw5.
(approximately 1.Mw to 3.mw) and sufficiently cooled, and the waiting time is sequentially decreased for each cycle, and after an hour or N5 cycles, the waiting time is returned to the steady state of M.

In the low-temperature drawing process, the drawing time is maintained at te in order to prevent excessive cooling when the maximum temperature of the drawn cast iron rod is lower than the maximum temperature in the steady state by, for example, 100°C to 20°C, but the waiting time tw6 (0. hole w to 0.
The cycle in which the cast iron bar is drawn out is continued in sequence until the maximum temperature of the cast iron rod from which it is drawn is, for example, 10 qo to 20° C. higher than the maximum temperature in the steady state.

The pouring and drawing process is used to prevent the risk of hot water leaking due to a slight rise in hot water temperature and condensation when the amount of hot metal remaining in the holding furnace decreases. During the predetermined pouring and withdrawal time m3 or pouring and withdrawal cycle N3 (approximately 10 to 30 cycles), the withdrawal time is maintained at te, but the waiting time is initially longer than tw.
w3 (approximately 1.Mw to 3.w) and gradually decrease it,
After T3 hours or N3 cycles, the waiting time is returned to the steady state of tw.

In the termination drawing process, the drawing time is set to te4 (1.
P-3. The waiting time is increased to W4 (approximately 3.5 to 6.0 cm), and the public bath is closed and the remaining slag is removed.

An apparatus used in one embodiment of the method of this invention is shown in FIG.

Reference numeral 1 denotes a holding furnace in which hot water 2 is stored and heated by a burner.

This holding furnace 1 has a graphite mold 3, and a water cooling jacket 4 is provided around the graphite mold 3. 5 is a roller for pulling out the cast iron twill 6 from the graphite mold 3;
The pressure roller 11 is a pressure cylinder.

Reference numeral 7 denotes a drive unit for the roller 5, which causes the roller 5 to pull out the cast iron rod 6 at a constant speed.

As the drive unit 7, for example, an electric motor, a hydraulic servo motor, etc. can be used. Reference numeral 8 denotes a thermometer, which measures the temperature of the cast iron rod 6 that has been pulled out, and is installed at a position L' indicating the maximum temperature.

This maximum temperature position L is determined depending on the size and material of the cast iron shank 6. Although various thermometers can be used, a two-color radiation thermometer is most desirable. The output signal of this thermometer 8 is supplied to a control section 9 composed of a microcomputer, for example, and the control section 9 also includes te, te2/
Ne, Ni4, tW, tW, /tW, tW2/tW, t
W3/tW, field 4/tw, tw5/W, tw6/tw,
N, or T, N2 or T2, N2' or T2', N3 or T3, and N5 or T5 are set. Furthermore, a rising temperature signal and a lower limit temperature signal are also set. In this embodiment, the control unit 9
Then, te2 is calculated based on te and te2/te, and tw is calculated based on tw and tw, /tw', and the drawer drawing process is performed. During this process, the number of cycles or time is measured by the control unit 9, and when it reaches T or N, the process moves to the start drawing process. This process also measures the number of cycles or time in the same machine as the drawer extraction process, and
When +T2' or N20N2' is reached, a steady state is entered. In addition, in both processes, the upper limit temperature signal and the lower limit temperature signal are interlocked so as not to shift to the high temperature drawing process and the low temperature drawing process. When the output of the radiation thermometer 8 reaches a value equal to or higher than the upper limit temperature signal for 1 second or more in a steady state, a transition is made to the high-temperature drawing process.

During this high-temperature drawing process, if the value exceeds the upper limit temperature signal again for more than 1 second, the waiting time is increased by W x and the operation is continued until the rib signal of the radiation thermometer 8 reaches a value less than the lower limit temperature signal for more than 1 second. .

Further, when the output of the radiation thermometer 8 reaches a value below the lower limit temperature signal for more than 1 second in a steady state, the waiting time is reduced by Mx by 1, and the process shifts to the low-temperature extraction process. The transition from the steady state to the hot water drawing process is performed by the operator sending a signal to the control unit 9. Note that the upper limit temperature signal and the lower limit temperature signal are interlocked during this process as well. The transition to the final drawing process is also carried out by the operator sending a signal to the control section 9. According to this continuous casting method, the waiting time for drawing is controlled depending on the situation according to a program installed in the control unit, so that a product with uniform properties can be obtained.

Furthermore, since the control is performed almost automatically, one person can monitor multiple holding furnaces, reducing the number of manpower required. In the above embodiment, the method of the present invention was applied to horizontally drawn cast iron rods, but it can also be applied to vertically drawn ones.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an apparatus used in the continuous casting method for cast iron according to the present invention, Fig. 2 is a diagram showing changes in each drawing time in the same method, and Fig. 3 is a diagram showing changes in each waiting time in the same method. It is a diagram showing a prone state. 1... Holding furnace, 2... Molten metal, 3... Graphite mold, 5... Roller, 6... Cast iron rod, 7
...Driver, 8...Thermometer. 2 pictures

Claims (1)

[Claims] 1 A method in which a cast iron rod formed by cooling molten metal stored in a holding furnace is pulled out at a constant speed during a drawing time, and this drawing state is maintained for a waiting time, which is repeated as one cycle, and the temperature of the cast iron rod is In a steady state at a predetermined reference temperature, the above-mentioned drawing time and waiting time are in a steady state with predetermined te and tw, and when pouring into the holding furnace, the above-mentioned drawing time is maintained for a predetermined time or a predetermined cycle. The above waiting time is set to tw_2, which is longer than the initial tw, and is sequentially changed to t.
A method for continuous casting of cast iron, which comprises a pouring and drawing process in which the molten metal is gradually reduced to a constant drawing process.