JPS60145962A - Brick for embedding low heat conductivity blast furnace stave - 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 [Field of Industrial Application] The present invention relates to improvements in bricks for embedding blast furnace staves.

[Technical background of the invention]

Bricks for embedding blast furnace staves are required to have the same alkali resistance, water resistance, oxidation resistance, and abrasion resistance as ordinary blast furnace wall bricks.
In addition to having limited conductivity, it is also required to have high spalling resistance against thermal shock during stave casting and high compressive strength against shrinkage of the metal during solidification.

Conventionally, β-5iC bonded silicon carbide bricks made by adding metal silicon to SiC and fired for reduction, and silicon nitride bonded silicon carbide bricks fired for nitriding have been used for blast furnace walls, but the thermal conductivity is 20 to 10 Kca. It has a high I/mh'C and is not suitable as a brick for embedding staves.

In addition, (α + β) alumina + spinel + carboxylic brick has a low thermal conductivity of 7 Kcal/ml + °C (although it meets the requirements from a thermal conductivity point of view, 1!'101 N
It is not possible to impart alkalinity, high wear resistance, and high spalling resistance.

As described above, conventional blast furnace bricks are insufficient as bricks for stave embedding, and solving this problem has been an urgent technical issue for stave cooling type blast furnaces.

[Purpose of the invention]

An object of the present invention is to provide a brick that has high alkali resistance, high abrasion resistance, high spalling resistance, and low thermal conductivity sufficient for use as a brick for embedding a stave in a stave cooling type blast furnace.

[Structure of the invention]

The stave embedding brick according to the present invention is Si3N4
It is made by kneading and molding a powder-based compound, then nitriding and firing, and has a low thermal conductivity of 7 Kcal/mh°C or less.

Si3N+ is one of the high-strength materials for fine ceramics that has recently attracted attention, and various types have been reported, ranging from dense sintered bodies with almost no pores to those with several tens of percent porosity. The SIB N/raw material used in the present invention must have an open porosity of 25 to 45% in view of the balance between strength and thermal conductivity of the final product. If it is less than 25%, the thermal conductivity of the product will be high, and if it exceeds 45%, the product will not have sufficient strength.

Next, regarding the amount of SiB N÷ added, in order to reduce the thermal conductivity of the product brick to 7 Kcal/mh'C or less, 30% by weight or more is required. 35 to 60% by weight is desirable.

Also, in the present invention, spalling resistance.

SiC is added for the purpose of imparting alkali resistance and wear resistance. The amount added needs to be 40% by weight or less because if it exceeds 40% by weight, the thermal conductivity will not be less than 7 kca'l/mh''C.

Metallic silicon, ferrosilicon, or a mixture of both is added to develop strength. The amount added is 5% by weight
If it is less than 7 Kcal/mh'C, the thermal conductivity will not be lower than 7 Kcal/mh'C, and the strength will not be sufficiently developed and the wear resistance will decrease. Moreover, if it exceeds 30% by weight, nitriding will not be completed completely and free silicon will remain, causing a problem in that the oxidation resistance against water vapor will decrease.

As the binder added to the compound, binders with high carbonization yield such as phenol resin and molasses can be used, but decarburization during nitriding and firing becomes difficult.
When nitriding is performed without decarburization, the reaction of Si+C-βSiC starts at a lower temperature than the reaction of 3Si + 2N 2-5i3N÷, so after β-3iC is generated, Si3
The generation of N÷ occurs. When β-5iC is generated, it becomes difficult to reduce the thermal conductivity to 7 Kcal/mh'C or less, and in order to reduce the thermal conductivity to 7'Kcal/mh'C or less, the amount of SiB N+ added must be increased. This would reduce the effectiveness of the addition of Sla +44. Furthermore, when β-3iC is generated, the number of 5iBN4 bonds decreases, resulting in a decrease in strength and a tendency for wear resistance to decrease. Therefore, in order to reduce the production reaction of β-3iC and increase the effect of the addition of Si3N, a binder with a carbonization yield of 30% or less, preferably 10% or less, such as PV
It is desirable to use a binder with a low carbonization yield, such as A (polyvinyl alcohol) or vinyl acetate. When such a binder with a low carbonization yield is used, it is possible to nitride and sinter it without decarburizing it (it can be nitrided and fired as is).This allows one manufacturing step to be omitted, saving energy and simplifying equipment, as well as reducing the cost of intermediate products. 9) Benefits include preventing damage to the product.

〔Example〕

The following examples show the benefits of the present invention.

After adding a binder to the mixture shown in the attached table and kneading it, it was press-molded into the shape of a brick for embedding a blast furnace stave and fired to produce bricks within the scope of the present invention (Examples 1 to 11) and comparative bricks ( Comparative Examples 1 to 11) were created.

Under the firing conditions shown in the same table, nitriding firing was performed at 1450°C in an N2 atmosphere by flowing N2 gas from room temperature without any decarburization treatment, and reduction firing was performed by firing bricks in a coke breeze. embed 1450
It was fired at ℃.

The properties of each manufactured brick are shown in the middle row of the attached table.

A stave cooler was manufactured using 100111i1 of each brick, and hot metal at 1550°C was poured into it to examine the occurrence of cracks. Examples and Comparative Example 1 where no cracks occurred
and 6 (Comparative Examples 2 and 5 were used in an actual furnace) were embedded in the same blast furnace. In the comparative example, spalling occurred after one year of use, and when it was taken out and observed, it was found that there was significant wear and tear. On the other hand, when the bricks of each example of the present invention were similarly observed after two years, no abnormalities were observed.

From the above examples, it can be seen that the nitrided silicon-carbon silicon brick of the present invention, especially the brick using a binder with a low carbonization yield, has optimal properties as a brick for embedding a blast furnace stave, and can be used in an actual furnace. It can be seen that it has been used and has shown good results.

Claims (1)

[Claims] 1. 30 to 95% by weight of Si3N4 powder with an open porosity of 25 to 45%, and sic! 9JO~40% by weight,
Adding a binder to a composition consisting of 5 to 30% by weight of metal silicon powder, ferrosilicon powder, or a mixed powder of both;
Kneaded, molded, then nitrided and fired at 200°C
The thermal conductivity at 7 Kcal/ml+'c
A brick for use in embedding a blast furnace stave with low thermal conductivity, characterized by: 2. Polyvinyl alcohol as a binder for the formulation;
The low thermal conductivity brick for embedding in a blast furnace stave according to claim 1, characterized in that a binder with a low carbonization yield such as vinyl acetate is used.