JPS61126951A - Preheating method of nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To preheat uniformly the entire part of a nozzle for continuous casting while preventing the failure thereof by winding a heat insulating material to the proper point around the nozzle and heating electrically the nozzle. CONSTITUTION:Electrodes 11, 12 are respectively attached to the upper and lower parts of the immersion nozzle 10 for continuous casting. The circumferential part of such nozzle 10, except the part where the sectional area is smaller than the sectional area of the other part, for example, the part of a discharge nozzle 14, is wound and coated with the heat insulating material 15 such as 'Kaowool(R)'. The heat loss by the radiant convection at the other part can be suppressed when the nozzle 10 is electrically heated in this state. The kind and thickness of the material 15 are adjusted in this preheating method, by which the difference between the heat loss near the discharge hole 14 and the heat loss of the part wound with the material 15 is eliminated. The difference in the calorific value owing to a difference in the sectional area of the nozzle 10 is eliminated and the uniform heating is executed by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuous casting nozzle such as a submerged nozzle or a long nozzle that generates resistance heat when energized.

[Conventional technology]

If the continuous casting nozzle mentioned above is not sufficiently preheated before being installed in a ladle or tandy shell, it will not be able to withstand the thermal shock caused by the molten metal passing through the nozzle, causing cracks and
causing damage.

Conventionally, as one of the methods for performing the above preheating, Japanese Patent Application Laid-open No. 49-
As described in Japanese Patent No. 110538, there is a method of energizing a continuous casting nozzle and heating it by resistance heat generation.
The same method is shown in FIG.

1.2 indicates the electrodes attached to the upper and lower parts of the immersion nozzle 3, 4 indicates the power source, and the heating of the immersion nozzle 3 is as follows:
This is carried out by passing an electric current in the longitudinal direction of the immersion nozzle 3 and heating it with electricity.

“This method does not take much time to raise the temperature;
Also, since the temperature of the immersed nozzle 3 can be raised at the place of use, there is an advantage that there is no need to move the immersed nozzle.

[Problem that the invention seeks to solve]

However, in this conventional method, the vicinity of the discharge hole 5 provided at the bottom of the immersion nozzle 3 has a small cross-sectional area and high resistance, so it is heated more intensively than other parts, and the immersion nozzle 3 The immersion nozzle 3 may not be heated uniformly, and the immersion nozzle 3 may be damaged.

An object of the present invention is to provide a method for preheating a continuous casting nozzle that can uniformly heat the entire immersed nozzle with electricity and reliably prevent damage to the immersed nozzle.

Measures for Solving Problem c] In order to solve the above problem, in the present invention, a heat insulating material such as Kao wool is used around the continuous casting nozzle, except for the part where the cross-sectional area is smaller than other parts. The entire nozzle is heated uniformly by winding the material and then heating the nozzle with electricity.

〔Example〕

Hereinafter, means for solving the above problems will be specifically explained based on the embodiment shown in the attached drawings.

In FIG. 1, IO is an immersed nozzle, and the immersed nozzle 10 has t-poles 11 and 12 at its upper and lower parts, respectively.
A power source 13 is provided between the electrodes 11 and 12. Moreover, 14 is a discharge hole provided at the lower part of the immersion nozzle 10.

This embodiment is characterized in that, during electrical heating, except for the portion of the discharge hole 14 where the cross-sectional area is small, the other portions are previously wrapped and covered with a heat insulating material 15 such as Kao wool.

In addition, in FIG. 1, only the straight part is shown, but the upper enlarged diameter part shown by the dotted line can also be wound and covered.

With this configuration, when electricity is applied, heat loss due to radiation convection in other parts can be suppressed.

Further, since the vicinity of the discharge hole 14 is directly exposed to the atmosphere, heat loss due to radiation and convection is greater than that in the area around which the heat insulating material I5 is wrapped.

If this difference in heat loss is made equal to the difference in heat generation amount due to the difference in cross-sectional area, uniform heating becomes possible.

The difference in heat loss can be easily adjusted by changing the type and thickness of the heat insulating material 15.

[Confirmation of heat retention effect]

In order to confirm the heat retaining effect of the heat insulating material 15, the following conditions (1) and (2) were set to calculate the temperature rise.

■ Prepare the samples shown in Figures 2 (a) and (b). The sample in FIG. 2(a) is an immersion nozzle 20 made of alumina graphite (hereinafter referred to as AGf), with an inner diameter of 70Il.
ll, and is molded into a cylindrical shape with an outer diameter of 120+os. The sample in FIG. 2(b) is the immersion nozzle 20 of the above AGf.
It is assumed that a heat insulating material 214:4 made of Kao wool is attached to the outer circumferential surface of the body, and its outer diameter is set to 17011-.

When calculated under the conditions shown in Table 1 and Table 2, assuming that the inner hole is adiabatic, the temperature of the samples in Figures 2 (a) and (b) is approximately 800°C approximately 18 minutes after illumination. and 1200°C, which is 400°C.
There is a temperature difference of more than ℃. This shows that the heat retaining effect of the heat insulating material is remarkable.

〔Effect of the invention〕

As described above, the present invention can uniformly preheat the entire continuous casting nozzle, and can effectively prevent cracking and breakage of the nozzle.

[Brief explanation of drawings]

FIG. 1 shows a cross section of a continuous casting nozzle to which the method of preheating a continuous casting nozzle according to the present invention is applied, 211 (a)
), (b) is a perspective view of a sample used for calculating the heat retention effect, and FIG. 3 is an explanatory diagram of a conventional preheating method. In the figure, 10: Immersion nozzle 11.11t pole 13; Power supply 14: Discharge hole 15: Insulating material patent applicant Masu Kobori (one idiot), representative of Shizaki Ceramics Co., Ltd. Figure 1 (a) Figure 3 Figure 2 (b)

Claims (1)

[Claims] 1. Wrap heat insulating material such as Kao wool around the nozzle for continuous casting, except for the nozzle part where the cross-sectional area is smaller than other parts, and then heat the entire nozzle uniformly by passing electricity through the nozzle and generating heat. How to preheat a continuous casting nozzle.