JPS63158381A - Reflux pipe for vacuum degasifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention is a vacuum degassing device that suppresses mechanical wear due to initial spall and molten steel flow caused by current insufficient preheating, and extends its service life. This relates to a reflux tube.

(Prior art) Conventionally, in vacuum degassing equipment such as RH, it is the reflux pipe that is subject to wear and tear from the flow of molten steel, and currently the main cause of disposal of the lower layer is the reflux pipe bricks. This is due to the small amount remaining.

The inner periphery of this ♀ flow tube is constructed by arranging 20 large bricks in a circle and stacking them in 2 stages, 93 stages, and t stages with mortar.

(Problems to be Solved by the Invention) The lower layer of the vacuum degasser including the reflux tube is usually preheated to Ir0CPC~/700°C before use. However, the temperature of molten steel is still 50060~g00°C
There is a temperature difference, and when molten steel is poured immediately after the start of RE operation,
The thermal shock causes initial spalling on the working surface of the reflux pipe bricks.

Currently, there is no sufficient method to suppress the initial spall caused by heat pumping, which reduces the service life of the return pipe and requires intermediate repair work such as press-fit repair, which causes a decrease in the operating rate of the vacuum degassing equipment. It becomes. Furthermore, due to the increase in the temperature of molten steel due to the extension of RH operation time and the introduction of oxygen blowing operation, the conventional reflux pipe structure is no longer able to adequately cope with the severe melting loss.

The object of the present invention is to provide a reflux tube for a vacuum degassing device that eliminates the problems of conventional pipes, suppresses mechanical wear due to initial spall and melt flow, and extends its service life.

(Means for solving interlayer points) In order to achieve this object, the present invention has the following configuration.

That is, the present invention provides an io-s on the inner circumferential surface (molten steel passing surface) of the reflux pipe whose inner circumferential portion is made of refractory brickwork.
OW 7 Now, it is characterized by being coated with a monolithic refractory having residual expandability. The monolithic refractories with residual expansibility used here include sillimanite with residual expansibility - sillimanite group minerals such as andalusite and kyanite, and the remainder is made of highly refractory powder such as alumina and alumina as a binder. Preferably, it contains cement.

The reason for using a large, amorphous material with residual expansibility is to expand the coating layer to compress the refractory bricks and suppress the initial spalling of the refractory bricks. It also has the meaning of suppressing flaking caused by wear of the molten steel flow.

In addition, when sillimanite group minerals are used, these minerals form crystals with low thermal conductivity such as mullite due to the heat of molten steel, which prevents the coated refractory bricks from receiving direct thermal shock from the molten steel. This is to do so.

The coating method for the above-mentioned monolithic refractories can be done by troweling, hand coating, spraying, casting, etc., but the reason why the coating thickness is /QMH~jOff is that the coating effect is sufficient at /QM11 or less. Thank you very much, jQm
If the temperature exceeds s, the inner hole of the reflux pipe becomes narrow, which not only affects the flow rate of the molten steel, but also causes peeling of the monolithic refractory due to an increase in the frictional force of the molten steel flow.

(Example /,) A monolithic refractory of NO, / shown in the table was coated with a thickness of 3Qmtg by casting on the brick surface of the inner peripheral part of the reflux pipe of a 7OtmRH type vacuum degasser.

(Example A 2) Initial installation of monolithic refractories f, l OMM thickness shown in MO2 in the table was performed on the brick surface of the inner peripheral part of the reflux pipe of a 7Q IRH type vacuum degassing device different from Example/. went.

(Effect of the invention) When the construction according to Example/ was put to practical use,
In the case of conventional uncoated monolithic refractories, the total service life after 7 press-fit repairs is about 2 o th, compared to 2 oth without any repairs! The service life was 01A.

In addition, in the case of Embodiment 2, while the conventional method usually requires press-fit repairs every JQth and has a total service life of 5ooth, according to Embodiment 2 of the present invention, there is no press-fit repair and the total service life is 50th.
A durability of 3Qtk was obtained.

This invention improves the durability of the refractory brick by coating the surface of the refractory brick with a monolithic refractory with residual expandability, thereby suppressing the initial spalling of the refractory brick and the mechanical wear caused by the flow of molten steel. t- exerts and produces a soaking effect.

Patent Dehaton Tokyo Kaguri Co., Ltd. −“−Hi’Ikujo 1

Claims (1)

[Claims] 1. A reflux tube for a vacuum degassing device, characterized in that the inner periphery of the reflux tube is made of refractory brickwork, and the inner periphery of the reflux tube is coated with a monolithic refractory having residual expansion properties.