JPH07291718A - Magnesite-chrome refractory brick - Google Patents

Abstract

PURPOSE:To provide a magnesite-chrome refractory, which is a magnesite- chrome refractory for secondary refining obtained by efficiently utilizing a magnesite-chrome brick chip of a control waste and attempts high corrosion resistance of a matrix and high durability by making uniformly dense. CONSTITUTION:The magnesia constituting 50-80wt.% in total weigh of the refractory is composed of 10-70wt.% pulverized material of the magnesite-chrome refractory chip after used for smelting and refining vessel and having <=1mm particle diameter and the balance the magnesia clinker having >=1mm particle diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magrophilic refractory brick to which a crushed product of magrophilic refractory brick is added.

[0002]

2. Description of the Related Art Magnesium brick is used as a refractory lining for secondary refining vessels in steel processes.

This magchromic brick is obtained by directly bonding a chrome ore having a very small amount of SiO ₂ and a magnesia clinker (calcined magnesia) by high temperature calcination.

In recent years, the importance of the secondary refining process has increased with the strictness of steel varieties and the increase of high-grade steels, and the content of its operation is to increase the basicity of slag, increase the treatment temperature, and other refractory linings. On the other hand, it becomes severer and it is required to improve the durability of maguro brick.

The maguro brick used as the lining of the secondary refining vessel is worn by the following mechanism.

Slag infiltration into brick structure Dissolution of magnesia or chrome ore that composes bricks into slag → Melt loss After the binding force between the constituent particles of the brick is reduced, erosion is caused by recirculation force → Erosion slag infiltrated layer and raw brick Due to the difference in physical properties of the infiltrated layer due to repeated thermal cycles → Structural spall

Among these wear mechanisms, it is widely known that the slag infiltration and the structural spall associated therewith occupy a large specific gravity as a cause of wear.

Slag infiltration causing this structural spall
To control bricks, aiming for the densification of bricks and optimizing the granularity
, High pressure molding, Cr ₂O₃Fine powder addition, secondary spinel
Ultra-high temperature firing and the like aiming at generation are carried out. Also oxidation
Also known is the method of mixing chromium powder to accelerate sintering.
(Japanese Patent Publication No. 57-57428, etc.).

However, even by these means, the porosity is 12 to 14%, and there is room for improvement.

Therefore, as one of the methods for densifying the brick structure, a method of adding metallic chromium powder and firing it has been disclosed (JP-A-62-207757).

[0011]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method proposed in Japanese Patent No. 7757 utilizes the fact that the melting point is lowered by mixing a high melting point (about 2300 ° C.) chromium oxide powder with a metallic chromium powder (melting point 1830 ° C.), thereby promoting sintering, It is said that bricks can be densified (porosity 11%).

However, the eutectic point of both is still high at 1660 ° C., which is not sufficient from the viewpoint of densification of the brick structure. Further, there is a concern that uneven firing is likely to occur.

That is, the peripheral portion of the brick is sufficiently fired to have a dense structure, but metallic chromium remains unfired in the central portion and the structure is not densified.

Its corrosion resistance is about half that of the dense part around the brick where sintering has advanced.

In addition, since it is difficult to uniformly mix the metal chromium powder during kneading, the effect of adding the metal chromium is not sufficiently exerted, and it is difficult to uniformly densify the entire brick structure. Therefore, it is not possible to ensure sufficient durability of the brick as a whole.

The above has described the problems in the use of magrophilic refractory bricks. In addition, since the dismantling waste after use of maguro refractory bricks becomes a management waste material due to environmental problems, there is an urgent need to establish an effective method of utilizing the waste material (waste material).

As one of the effective utilization methods, demolition scraps after removing the adhered slag are crushed to obtain the same particle size (0.01 to 15 mm) as that of the raw material of 0.01 to 15 mm magnesia clinker for the refractory brick. It was considered to replace a part or all of the used post-use crushed product.

[0018] A magrophilic refractory brick having a wide particle size distribution and containing a pulverized product of a used pulverized refractory refractory brick contains a very large amount of a slag infiltration layer (including slag) mixed from the pulverized product, Due to the quality of the bricks, the durability against melting, erosion and structural spalls deteriorated significantly, and they could not be used.

The present invention provides a magrolithic refractory brick which solves the above-mentioned conventional problems.

[0020]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is 50 to 8% of the total weight of a brick.
10% to 70% of the magnesia occupying 0 wt% is a crushed product of magcrophilic refractory bricks having a particle size of less than 1 mm, and the remaining 90 to 30% is a magnesia refractory brick composed of 1 mm or more magnesia clinker. is there.

[0021]

The inventors of the present invention have made various methods for effectively utilizing the scraps of magrophilic refractory bricks and for uniformly densifying the matrix part that is subjected to slag infiltration for the purpose of improving the durability of the magrophilic refractory bricks. investigated.

After the molten steel refining vessel (secondary refining vessel) has been used, the slag adhering to the working surface is removed from the debris from the refractory bricks, and the jaw crusher, roll crusher, hammer mill, cutter mill, fret mill, impeller mill are used. It was crushed by a crusher such as.

The crushed product thus obtained was further classified after removing the invading metal by magnetic separation.

As a result of investigating each particle size after classification, the part which is mainly composed of the matrix part and which has undergone slag infiltration is
Since the cold strength is increased due to the adhesive effect of the slag and it is difficult to crush, it was hardly crushed to less than 1 mm.

The crushed product having a size of less than 1 mm is produced mainly from an aggregate portion which is hardly infiltrated with slag and slightly Ca
Fine slag powder containing O and Al ₂ O ₃ as main components was mixed.

Further, results of examining the mineral composition for 1mm less than the ground product, magnesia Pericles, composite spinel _{(MgO · Al 2 O 3,} MgO · Fe 2 O 3) and Pic runner chromite (MgO · Cr ₂ O ₃ ).

Before use, the 50 mm portion from the working surface side is removed before crushing the scraped refractory bricks, and then the crushed product having a particle size of less than 1 mm is slag-infiltrated into the matrix part after crushing. The mixture of can be prevented more.

Further, in order to prevent the slag-infiltrated matrix portion from being mixed, it is desirable to remove a portion of 100 mm from the working surface side.

The matrix of magchromic refractory brick is
It is composed by sintering raw material powder of 1 mm or less, and it aims to suppress slag infiltration by densification of this part and improve corrosion resistance by making MgO secondary spinel and picrochromite. It is being carried out.

Here, in order to form a matrix portion corresponding to conventional bricks, a crushed product of magrophilic refractory bricks of less than 1 mm, which already contains spinel and picrochromite, is made of magnesia which accounts for 50 to 80 wt% of the total brick weight. 10 mm to 70% of quality raw material added particle size 1 mm
By substituting the magnesia clinker of less than 1 and making a brick by a conventional manufacturing method (molding → baking), a matrix layer having excellent corrosion resistance could be formed.

Further, in the above-mentioned mag-chromic refractory bricks prepared by using a crushed product of mag-chromic refractory bricks having a particle size of less than 1 mm, since slag fine powder containing CaO and Al ₂ O ₃ as main components is slightly mixed, Liquid phase sintering occurred at the initial stage of firing, and uniform densification of the matrix portion could be achieved.

In addition, the pore morphology of the brick was such that the open pores causing the slag infiltration disappeared and almost all became closed pores, and the slag infiltration resistance was improved. However, the porosity is 10% to 11
%, And the decrease in heat resistant spalling property was not caused.

Further, CaO, which contributed to the uniform densification of the matrix, is solid-dissolved in the magnesia clinker of 1 mm or more, and Al ₂ O ₃ reacts with the magnesia clinker of 1 mm or more to be spinelized, and finally at a high temperature. There was no slag composition grain boundary segregation that reduced the strength.

In the brick of the present invention, the spinelization and the picrochromite conversion of the magnesia of the matrix part have been already completed before firing, and the liquid layer sintering of the matrix is possible at 1700 ° C. It was possible to create a magrophilic refractory brick that has excellent durability even when the conventional ultrahigh temperature (1800 ° C) is lowered by 100 ° C. Further, there was no problem even if the metallic chromium powder was added in an amount of 2% or less.

On the other hand, the amount of magnesia clinker of 1 mm or more in the magnesia raw material occupying 50 to 80% by weight of the total brick is reduced, and more than 70% of the crushed crushed product of magurophilic refractory bricks is added to the brick brick. The densification progressed and the heat-resistant spalling property deteriorated, and it could not be used.

Next, the amount of magnesia clinker of 1 mm or more in the magnesia raw material occupying 50 to 80 wt% of the total brick is increased, and less than 10% of the crushed product of magurophilic refractory brick is added to the brick. The matrix portion could not be sufficiently densified, and the matrix was subjected to slag infiltration more than conventional bricks and could not be used.

Further, 10 to 70% is a crushed product of magrophilic refractory bricks of less than 1 mm, and the remaining 90 to 30% is 1 mm.
When the ratio of the magnesia raw material composed of the above-mentioned magnesia clinker to the total goodwill was less than 50% and the amount of chromium ore was increased, it was easily eroded by the high basicity slag and could not be used.

On the other hand, 10 to 70% is a crushed product of magrophilic refractory bricks of less than 1 mm, and the remaining 90 to 30% is 1 mm.
If the ratio of the magnesia raw material composed of the above magnesia clinker to the total brick is higher than 80% and the amount of chromium ore is reduced, the strength of bricks can be sufficiently improved by the reaction of picromchromite at the chromium ore-magnesia raw material interface. In addition, the brick could not be scraped off due to the reflux force during use, and could not be used.

[0039]

EXAMPLES Examples will be described below.

A refractory product to which a crushed product of magchromic refractory bricks of less than 1 mm, which is the newly developed product, was added was experimentally manufactured, and its effect was investigated.

The test conditions and evaluation index are shown below. Test conditions-Large sample size 75 x 114 x 230 mm-Erosion test conditions Method Rotational erosion test time with induction furnace 1850 ° C x 0.5 hours Steel SUS304 slag C / S = 3, CaF2 = 20% addition 400g
× 2 atmospheres Vacuum / Spalling test -Melt loss index After the erosion test, the reduced amount of each sample was measured, and the reduced amount of the sample of reference numeral 1 was standardized to be 100 to obtain the melt loss index. The smaller the melt loss index, the higher the corrosion resistance.

The results are shown in Table 1. The results of the comparative product are shown in Table 2.

Samples 1 to 12 to which the crushed product of magchromic refractory brick waste of less than 1 mm had been added already had a dense matrix portion uniformly formed by the raw material containing spinel and picrochromite. 50-80wt
The corrosion resistance is improved by 10% or more from the conventional bricks 13 to 16 in which 10 to 70% of the magnesia clinker having a particle size of less than 1 mm is added to the magnesia raw material accounting for 10%.

Among the magnesia raw materials occupying 50 to 80 wt% of the total brick weight, the amount of the magnesia clinker of 1 mm or more was reduced, and 70% or more of the ground crushed product of magrophilic refractory bricks of less than 1 mm was added to bricks 17 and 18 to make bricks. The densification progressed, the heat-resistant spall resistance deteriorated, and no improvement in corrosion resistance was observed.

Next, the amount of magnesia clinker of 1 mm or more out of the magnesia raw materials occupying 50 to 80 wt% of the total brick weight is increased, and the bricks with less than 10% of crushed crushed refractory bricks of magchromic bricks of less than 1 mm are added. 20
However, since the brick matrix portion could not be sufficiently densified and slab infiltration could not be sufficiently prevented, no improvement in corrosion resistance was observed.

10 to 70% is a crushed product of magurophilic refractory brick waste of less than 1 mm, and the remaining 90 to 30% is less than 50% of the total magnesia raw material consisting of a magnesia clinker of 1 mm or less in the chromium ore. No improvement in corrosion resistance was observed for the 21,22 bricks with the reduced amount.

On the other hand, 10 to 70% is a crushed product of magrophilic refractory bricks of less than 1 mm, and the remaining 90 to 30% is 1 mm.
The ratio of the magnesia raw material consisting of the above magnesia clinker to the total brick is higher than 80%, and the amount of chromium ore is reduced.
It was not possible to sufficiently improve the strength of the brick due to the reaction of forming picrochromite at the interface of the magnesia raw material, and no improvement in corrosion resistance was observed.

As described above, the refractory material according to the present invention has higher durability than conventional bricks, and can extend the life of the refractory material lined in the secondary refining vessel.

In addition, it is possible to effectively utilize the waste material of magurolithic refractory material and reduce the raw material cost.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

The refractory material of the present invention has a brick weight of 50%.
10 to 70% of magnesia occupying ~ 80 wt%
Consists of a crushed product of magurophilic refractory bricks with a particle size of less than 1 mm, and the remaining 90 to 30% consists of a magnesia clinker of 1 mm or more. Thus, it was possible to obtain a magrolithic refractory brick having excellent corrosion resistance and having a uniformly dense matrix layer without deteriorating other refractory properties.

Further, the refractory material of the present invention is an effective reusable product of the used waste of magurolithic refractory brick, which is a management waste material due to environmental problems.

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[Procedure amendment]

[Submission date] June 1, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

Next, the amount of magnesia clinker of 1 mm or more out of the magnesia raw materials occupying 50 to 80 wt% of the total brick weight is increased, and the bricks with less than 10% of crushed crushed refractory bricks of magchromic bricks of less than 1 mm are added. 20
The brick matrix part cannot be fully densified and
No improvement in corrosion resistance was observed because it was impossible to sufficiently prevent the infiltration.

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Claims (1)

[Claims] 1. 10 to 70% of the magnesia which accounts for 50 to 80 wt% of the total weight of the bricks is made of crushed product of magcrotic refractory bricks after use of a molten steel refining container having a particle size of less than 1 mm, and the remaining 90 to 30% is Magnesium refractory brick made of 1 mm or more magnesia clinker.