JPS6333164A - Continuous casting method using heating mold - Google Patents

Abstract

PURPOSE:To keep the heat balance and to obtain a cast billet having good surface quality by making the temp. near outlet of a mold for continuous casting drawing as water-cooling the cast billet from molten metal in the mold, heated electrically at the melting point of casting metal or more, within the controlling range by cooling water quantity control. CONSTITUTION:In the continuous casting drawing as cooling 5 the cast billet 3 from the molten metal 4 in the mold 2 heated electrically at the melting point of casting metal or more, the temp. near the outlet of mold 2 is kept at within the controlling temp. range, for example, in case of copper casting, 1,060-1,080 deg.C controlling temp. range, by controlling the cooling water 5 quantity. In this case, the boundary face 1 of solidification becomes to projecting-like at the prescribed position, and so in case of becoming recess-like for the boundary face 1 by decreasing the cooling water 5 and advancing the boundary face 1, development of friction skin breakage 6 with the mold 2 caused by decentering of the cast billet 3 is prevented and the surface of case billet makes to good quality.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heated mold continuous casting method (hereinafter abbreviated as OCC method), and is particularly aimed at improving and stabilizing the quality of the ingot.

(Prior art and problems to be solved by the invention) OC
Method C is a method in which the cast metal is supplied into a mold that is heated to a temperature above the melting point of the cast metal using electric heating, and the ingot that is pulled out of the mold is cooled with water to continuously solidify the molten metal that comes into contact with the ingot within the mold. , temperature control of heated molds is the most important control item in order to obtain high quality ingots. However, even if the mold temperature is controlled with high precision, the quality of the ingot will deteriorate if other conditions become unstable. Among such disturbance factors, fluctuations in the amount of cooling water have a particularly large effect.

Industrial water is generally used as cooling water, but the water supply pressure varies depending on the amount used by other industrial equipment, and the amount of water changes accordingly. In the OCC method, the quality of the ingot is significantly reduced by reducing the amount of cooling water by about 5% of the predetermined amount of water. This change in cooling water is, for example, 2j! This is a change of 0.1 f/min for a flow rate of 0.1 f/min, and at present, this degree of variation is unavoidable industrially.

In the conventional OCC method, the temperature of the heated mold is detected by a thermocouple inserted approximately in the center of the mold wall thickness, and the temperature of the heated mold is detected by the PI of the temperature controller.
Highly accurate control is performed using D control. However, the decrease in cooling water disrupts the heat balance and causes defects such as minute cracks on the surface of the ingot. The reason for this is that when casting is performed under stable conditions, when the amount of cooling water decreases, the cooling capacity decreases, and the solidification interface in the mold moves toward the mold outlet side (forward). On the other hand, the temperature of the mold increases due to the heat of the molten metal because the amount of molten metal in the mold increases by the movement of the solidification interface. Here, the temperature controller automatically reduces the power supplied to the heating element to keep the mold temperature constant, and returns the mold temperature to the initial temperature (set temperature). During this process, minute cracks occur on the surface of the ingot. In other words, under stable conditions, the solidification interface (1) is flat or convex as shown in Figure 2, and the mold (2) and ingot (3) are connected through the molten metal (4). Due to the lubrication effect of the molten metal and (4), no scraping occurs, resulting in a high quality ingot (3)
is obtained.

In the top view, (5) indicates cooling water. On the other hand, when the cooling water decreases, as shown in FIG. 3, the solidification interface (1) moves forward and the temperature of the mold (2) increases. At this point, the heat balance is maintained, but at this point the temperature controller is activated and lowers the temperature of the mold (2) to the set value, causing the heat balance to collapse and the solidification interface (which was almost flat) to 1) becomes concave. At this time, due to slight eccentricity between the ingot (3) and the mold (2), friction occurs between the two, resulting in skin breakage (6).

In this way, even if only the temperature control of the mold is made highly accurate, it will not be effective unless fluctuations in the amount of cooling water are suppressed.

[Means and effects for solving the problems] In view of this, the present invention has been developed as a result of various studies, and it is possible to stably produce high-quality ingots without causing defects in the ingots even if the cooling water fluctuates. In this method, the cast metal is supplied into a mold that is maintained at a temperature higher than the melting point of the cast metal, and the ingot that is pulled out of the mold is water-cooled to continuously cool the molten metal that comes into contact with the ingot within the mold. In the casting method that solidifies the metal, the mold is maintained at a temperature above the melting point of the cast metal by electric heating, the temperature near the mold outlet is detected, and the amount of cooling water for the ingot is controlled so that this temperature is within the controlled temperature range. It is characterized by:

In the present invention, the mold temperature is not automatically controlled as described above, but electric power is heated, for example, electric power is supplied to a heating element for heating the mold, and the electric power is maintained so that the temperature of the mold is higher than the melting point of the cast metal.

The temperature of the mold is set at a temperature downstream of the outlet, for example, 10.
The temperature of the mold is controlled within a temperature range that allows high-quality ingots to be obtained. Mold temperature changes due to changes in cooling water,
When this temperature changes within the controlled temperature range, maintain this state (do not adjust the increase or decrease of the cooling water), and adjust the cooling water base when the mold temperature is outside the controlled temperature range or is about to go outside the controlled temperature range. It is something to do.

To adjust the control temperature range and amount of cooling water, determine the relationship between ingot quality and ingot temperature and the relationship between water amount and mold temperature for the cast metal in advance, and then manage the mold temperature simply by controlling the amount of cooling water. Can be done.

〔Example〕

An oxygen-free copper (OFC) ingot with a diameter of 15 m was produced by the OCC method. The power supplied to the heating element for mold heating is constant (1,
5-), insert a thermocouple at 10711111 behind the mold outlet, cool the ingot with water, and cast at a casting speed of 150 m/min. Control temperature range and amount of cooling water to obtain a high quality ingot. We investigated the relationship between

As a result, as shown in Figure 1, the control temperature range is 1060~
The temperature is 1080°C, and the amount of cooling water at that time is 1.5 to 2.
It can be seen that it is sufficient to control within the range of Of/min.

Therefore, the temperature at the mold outlet was set at 1060 to 1080°C, and the temperature at the mold outlet was adjusted by adjusting the amount of cooling water.

That is, casting is started with a cooling water amount of approximately 1.7 g/min, and then the temperature at the mold outlet changes due to fluctuations in water pressure, but if this temperature change is within the range of 1060 to 1080°C, the cooling water can be increased or decreased. If the temperature at the mold outlet drops to 1060℃ or around 1060℃ without adjustment, reduce the cooling water amount by 1.
．． 51/min, and when the mold outlet temperature rises to 1080℃ or around 1080℃, the cooling water flow rate is reduced to 2.01/min.
increased to n. As a result, no skin breakage was observed on the surface of the obtained high-quality ingot.

(Effects of the Invention) As described above, the present invention provides remarkable industrial effects, such as being able to stably obtain high-quality ingots for a long time without requiring precise control equipment.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the relationship between the mold outlet temperature and the amount of cooling water in the present invention, Figs. 2 and 3 show the casting state in the OCC method, and Fig. 2 shows the stable casting state,
The figure shows unstable casting conditions. 1. Solidification interface 2. Mold 3, ingot 4. Molten metal 5, cooling water 6. Skin rupture Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A casting method in which the cast metal is supplied into a mold held at a temperature above the melting point of the cast metal, the ingot pulled out from the mold is water-cooled, and the molten metal that comes into contact with the ingot in the mold is continuously solidified.The mold is heated by electricity. A heating mold continuous casting method characterized by maintaining the temperature at or above the melting point of the cast metal, detecting the temperature near the mold outlet, and controlling the amount of cooling water for the ingot so that this temperature is within the controlled temperature range.