JPS62114754A - Apparatus for producing slab and ingot having fine crystal structure - Google Patents

Abstract

PURPOSE:To obtain a slab and ingot having fine crystal structure by detecting the molten metal surface temp. in a casting mold and controlling said temp. so as to be kept within the range between the liquidus line temp. and solidus line temp. of a material to be cast. CONSTITUTION:The opposed parts of electrodes 11 are melted by the heat of an arc 13 and drop in the form of liquid drops 14 when electric current is supplied to the electrodes 11. A sensor 15 detects the molten metal surface temp. in the casting mold 12 and after the detection signal thereof is calibrated by a signal processor 16, the output signal thereof is fed to a temp. control device 17. The temp. control device 17 increases the current to be supplied from a current supply device 18 to the electrodes 11 to increase the arc temp. between the electrodes 11 when the molten metal surface temp. in the casting mold 12 is lower than the solidus line. The melting speed of the liquid drops 14 is thereby increased and the molten metal surface temp. is increased. On the other hand, said device decreases the current value between the electrodes 11 when the molten metal surface temp. rises higher then the liquidus line. The melting speed of the liquid drops 14 is thereby decreased and the molten metal surface temp. is decreased. The molten metal surface temp. in the casting mold 12 is thereby maintained within the range between the solidus line temp. and liquidus line temp. of the material. The slab having the fine crystal grains is thus stably obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a manufacturing apparatus for manufacturing slabs and ingots having a fine crystal structure by drop casting technology.

[Prior Art] Usually, slabs or ingots, which are intermediate materials for gold i-products, are manufactured by pouring molten metal into a continuous casting mold or an ingot mold and solidifying it. However, in these conventional techniques, completely molten metal is cast into a mold, so the produced slab or ingot has a relatively large crystal grain size in its solidified structure. For this reason, when applying a reduction to the slab etc. in order to ensure mechanical properties, if a large reduction is applied, cracks will occur in the slab etc.

Therefore, it is necessary to apply the reduction blade in multiple times, but this requires a long processing time and also requires a large amount of energy, resulting in high processing costs.

The sensitivity to cracking due to the coarsening of the crystal grain size of the solidified structure is particularly noticeable in Ni-based ultra-super heat-resistant alloys, and the manufacturing process becomes extremely complicated when manufacturing this type of alloy. .

In order to eliminate the drawbacks of such general casting technology, VADER (Vacuum ArcDoubt) has recently been developed.
le E 1ectrode Remelting
A dropping casting technique called the vacuum arc two-electrode melting method has been proposed (Japanese Patent Application Laid-Open No. 165271/1983). In this VADER method, as shown in Fig. 4, a pair of electrodes 1 made of metal having the same composition as the slab to be manufactured
An arc 2 is formed between them, melting the opposite ends of the electrodes 1. The droplets 4 of the molten metal fall into the mold 3, are cooled and solidified by the mold 3, and a slab 5 is manufactured.

In this VADER method, the molten metal droplet 4 is slightly cooled while falling from the electrode 1 into the mold 3, and becomes a semi-molten state. Therefore, the half-7fJ molten metal 6 in the mold 3 solidifies in a state where the solid-liquid coexistence phase exists uniformly, so that the crystal grain size of the solidified structure of the slab 5 is small.

[Problem to be Solved by the Invention 1] However, in the conventional technology, various problems occur due to the instability of the supply speed of droplets into the mold. That is, if the droplet supply rate is slow, microporosity increases in the slab, making it impossible to obtain a healthy slab or ingot. on the other hand,
If the droplet supply rate is too fast, the crystal grains of the slab will become coarse, which will cause drawbacks to common casting techniques.

This invention was made in view of the above circumstances, and by detecting the temperature of the meniscus in the mold and controlling the surface temperature to an appropriate R condition based on this detection result, a healthy mold free of microporosity is created. It is an object of the present invention to provide an apparatus for manufacturing slabs and ingots having a fine crystal structure that can obtain internal quality.

[Means for Solving the Problems] The apparatus for manufacturing slabs and ingots having a fine crystal structure according to the present invention includes a mold, a pair of electrodes, and an arc formed between the electrodes to melt the electrodes. An arc forming means for dropping the droplets into the mold, a temperature detecting means for measuring the level of the molten metal in the mold, and a liquid phase I of the material to be cast based on the detection result of the temperature detecting means. ! hot water temperature TL) and solidus temperature (
T8).

[Function] In this invention, the temperature of the molten metal in the mold is detected by the temperature detection means, and the temperature of the molten metal is adjusted by the control means to the liquidus temperature (T) and the solidus temperature (T8) of the material to be cast. It is controlled to fall within the range between . FIG. 2 is a graph showing the results of investigating the internal quality and solidification structure of slabs produced by variously changing the melting conditions and solidification conditions (mold dimensions). The horizontal axis represents the temperature of the hot water inside the mold, and the vertical axis represents the microporosity index and grain size index.

As is clear from Fig. 2, microporosity increases when the temperature of the hot water in the mold falls below the solidus line (T8), and conversely, when the hot water level rises above the liquidus line (TL), solidification occurs. The crystal grains of the structure become coarser. From this, in order to produce sound slabs, etc., it is necessary to change the surface temperature between the solidus temperature (T8) and the liquidus temperature (Tt) of the metal alloy to be cast.
It can be seen that the temperature should be controlled within the optimum temperature range between , ).

For this reason, in the present invention, illumination is performed so that the hot water surface temperature falls within this optimum temperature range.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an apparatus for manufacturing slabs and ingots having a fine crystal structure according to an embodiment of the present invention. A pair of electrodes 11 are installed horizontally facing each other and spaced apart by an appropriate length. A current is supplied to this electrode 11 from a current supply device 18, and the electric current f! An arc 13 is formed between i11. A mold 12 is installed below the electrode 11 , and when the opposing ends of the electrode 11 are melted by an arc 13 , droplets 14 fall into the mold 12 . sensor 15
detects the meniscus (shoulder surface) temperature inside the mold. The detection signal of the sensor 15 is input to a signal processing device M16, and the signal processing device 16 converts the output signal of the sensor 15 into a signal corresponding to the meniscus temperature.

The output signal from the signal processing device 16 is input to the temperature control device 17, and the temperature control device 17 adjusts the current supplied from the current supply device 18 to each electrode 11 based on the meniscus temperature to maintain the meniscus temperature at a predetermined level. Control within range.

Next, the operation of the device configured in this way will be explained. First, a current is supplied to the electrode 11 by the current supply device 18, and an arc 13 is formed.

Then, the opposite end of the electrode 11 melts due to the heat of the arc 13, and drops as a droplet 14. The droplets 14 are slightly cooled while falling, and are cast into the mold 12 in a semi-molten state with a solid phase mixed in the liquid phase. The semi-molten metal 10 in the mold 12 solidifies in a state in which a solid-liquid coexisting phase exists uniformly, so that a slab 9 having a fine crystal structure is obtained. The sensor 15 detects the temperature of the surface inside the mold 12, and the detection signal is sent to the signal processing device l! After being calibrated by 16, its output signal is sent to temperature control device 17.
sent to. Temperature υII! The fl device 17 increases the current supplied from the current supply device 18 to the electrodes 11 to raise the arc temperature between the electrodes 11 when the surface temperature of the liquid in the mold 12 becomes lower than the solidus line (TS). The melting rate of 8114 is increased to increase the shoulder surface temperature. On the other hand, when the surface temperature of the hot water rises and becomes higher than the liquidus line (TL), the current supply device 18 reduces the current value between the electrodes 11, slows down the melting speed of the droplets 14, and lowers the 'a surface temperature. This maintains the shoulder surface temperature within the mold 12 within the range between the solidus temperature (TS) and liquidus temperature (TL) of the material to be cast. According to the method, slabs having fine crystal grains can be stably and easily produced.

Next, a second embodiment of the present invention will be described based on FIG.

This embodiment differs from the first embodiment in that the shoulder surface temperature is controlled by adjusting the temperature of the mold 12. Components that are the same as those in FIG. 1 are designated by the same reference numerals, and their description will be omitted. A heater 20 is wound around the mold 12 and supported by appropriate support means. The heater 20 is connected to a power source 19, and the heater 20 supplied with power from the power source 19 generates resistance and heats the mold 12.

In the device configured in this way, the sensor 15 detects the shoulder surface temperature of the semi-molten metal 10 within the mold 12, and the detection signal is sent to the temperature control bag M17 via the signal processing device 16. The temperature control 1iKl device 17 turns on the power supply 19 when the surface temperature of the hot water in the mold 12 becomes lower than the solidus line (TS).
The current applied to the heater 20 is increased to heat the mold 12 and raise the shoulder surface temperature. On the other hand, if the shoulder surface temperature rises above the liquidus (TL), the power supply 19 will stop or reduce the 'trX flow to the heater 20 and stop or reduce the heating of the mold 12 to make the surface easier. lower the temperature. As a result, the temperature of the molten metal in the mold 12 is maintained within the range between the solidus temperature (TS) and the liquidus temperature (TL) of the material to be cast.

Note that this mold may be provided with an electronic cooling means that can be electrically controlled, or a means for cooling the mold by adjusting the flow rate of mold cooling water with a flow j regulating valve may be provided.

Alternatively, the shoulder surface temperature may be controlled within a predetermined range by directly performing high-frequency induction heating on the surface of the semi-molten metal in the mold.

Further, it is also possible to use these various types of surface temperature control means in combination by sliding them in various ways.

Furthermore, although the above-mentioned embodiment relates to a continuous casting apparatus, it is also possible to apply the present invention to an ingot type casting apparatus using a mold with a bottom.

[Effects of the Invention] According to the present invention, it is possible to stably and easily produce slabs, etc., which have little microporosity and have fine crystal grains in the solidified structure, using a drop casting method.

[Brief explanation of drawings]

Fig. 1 shows an apparatus for producing slabs and ingots having a fine crystal structure according to the first embodiment of the present invention, and Fig. 2 shows the mold surface temperature, microporosity index, and crystal grain size. A graph diagram showing the relationship with the index, Figure 3 is the second example of this invention.
FIG. 4 is a schematic diagram showing the basic configuration of the conventional drip casting technique. 9... Slab, 10... Semi-molten metal, 1
1... Electrode, 12... Mold, 13...
...Arc, 14...Droplet, 15...
...Sensor, 16...Signal processing device, 17.2
1...Temperature control m+ device, 18...Current supply device, 1...Power supply, 20...Heater. Applicant's representative Patent attorney Takehiko Suzue Figure 1 TS TL -@type/114th page xq Figure 2 Figure 3 riA 0'4 ↓ Figure 4 1, Indication of case Patent application 1986-254'' + 03 @ 2, Name of the invention: Apparatus for producing slabs and ingots with a fine crystal structure 3; Relationship with the amended case Patent applicant (4, 12) Nippon Kokan Co., Ltd. 4; Agent address: 1 Toranomon, Minato-ku, Tokyo No. 26-5 No. 17a Bill 6, Detailed explanation column of the invention subject to amendment (B) ?・7″“7, Contents of amendment (c) On page 10, line 3 of the specification, “electronic” Delete that.

Claims (4)

[Claims] (1) A mold, a pair of electrodes, an arc forming means for forming an arc between the electrodes to melt the electrodes and causing the droplets to fall into the mold, and a temperature detection means for measuring the temperature of the molten metal surface in the mold. Based on the detection result of the temperature detection means, the liquidus temperature (T_L) and solidus temperature (T_L) of the material to be cast are determined based on the temperature of the molten metal.
A control means for controlling the temperature to fall within a range between S);
An apparatus for manufacturing slabs and ingots having a fine crystal structure. (2) The control means controls the temperature of the molten metal in the mold by controlling the current flowing between the electrodes. Equipment for manufacturing pieces and ingots. (3) The control means controls the temperature of the hot water surface in the mold by adjusting the temperature of the mold. Ingot manufacturing equipment. (4) The control means controls the temperature of the surface of the molten metal in the mold by performing high-frequency induction heating on the surface of the molten metal in the mold. Equipment for manufacturing slabs and ingots with texture.