JPH06191928A - Magnesia-chromium brick - Google Patents

Abstract

PURPOSE:To attain remarkable improvement of corrosion resistance which is not obtained from conventional magnesia.chromium bricks. CONSTITUTION:Electrofused Cr2O3 clinker fine powder having 3-44mum particle diameter and >=99% Cr2O3 content is added to a conventional magnesia.chromium brick component. The resultant magnesia.chromium brick is excellent in corrosion resistance and slag resistance and gives large improvement effect in a furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the properties of magnesia chrome bricks.

[0002]

2. Description of the Related Art Magnesia chrome (hereinafter referred to as magkuro)
Brick is generally used in secondary refining furnaces because of its high hot strength and good corrosion resistance. It has a long history, and there are various kinds of semi-ribbon bricks that use electro-melting raw materials such as magcro direct bond obtained by mixing seawater magnesia clinker and natural chrome ore and firing.

In recent years, there has been a demand for higher performance due to the stricter conditions of use and the need for improved durability. Current material is direct addition of natural chromium ore, or is in principal the addition of a sintering-fused clinker mixed with magnesia, other components in natural chrome ore especially _{SiO 2, Al 2 O 3,} Fe 2 O 3 It is mixed in as a flux, which is a factor that reduces its corrosion resistance. As a countermeasure, it is common to add Cr ₂ O ₃ having a purity of 99% or more.
In the case of refractory bricks, it is considered that the limit is about 5% by weight due to the grain size composition, since the range is almost the μm range. Therefore, it is the actual situation that a maguro that sufficiently satisfies the above needs has not appeared.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to greatly improve the corrosion resistance which cannot be obtained by the conventional magro bricks.

[0005]

In the present invention, it is possible to add Cr ₂ O ₃ of high purity more than ever before in order to improve the properties of magcro bricks, especially the corrosion resistance or slag penetration resistance. The Cr ₂ O ₃ composition has a high resistance to slag and is useful, but in the purity of 99% or more, it is generally present as chromium oxide in a particle size of 1 to 3 μm. On the other hand, it is theoretically considered that the fine powder portion of the matrix is appropriate in the range of 20 to 30% as the particle size constitution of the refractory, and further, 10%, that is, about 3% of the ultrafine powder of 5 μm or less is appropriate. (Refer to FIG. 1) If added in excess of that, the manufacturing aspect, particularly the tightness during press molding, is poor, and as a result the physical properties of the brick are deteriorated. However, in order to greatly improve the corrosion resistance as compared with the conventional product, it is preferable to add more Cr ₂ O ₃ with high purity to this fine powder region. Therefore, this Cr ₂ O ₃
As a method having a particle size that does not exist at present, it was invented that the large particle size clinker was once produced, adjusted to an appropriate particle size, and added. If a chromium oxide raw material is melted at a melting point or higher in an electric melting furnace and cooled to form a lump, it can be handled in the same manner as a general electromelting clinker, that is, crushed and sized. The commercially available chromium oxide having a particle size composition of about 1 to 3 μm is arranged in the fine powder region, and the present fused Cr ₂ is present in the particle region of 3 μm or more.
When O ₃ is added, the Cr ₂ O ₃ composition can be filled in the matrix portion that controls the corrosion resistance. However, excessive use of high-melting-point, refractory-sintering, high-purity Cr ₂ O ₃ can prevent bonding on the contrary and lead to deterioration in physical properties of the bricks, so caution must be exercised. In general, the upper limit of the fine powder is 44 μm, so in the present invention, the upper limit is set to 3 μm to 44 μm.

[0006]

[Example] A typical magcro semi-ribbon brick was manufactured and compared with a conventional product in an actual furnace. The composition is shown in Table 1. The specified raw materials were blended and mixed, a bittern binder was added, press-molded, and fired at a high temperature of 1800 ° C.

[0007]

[Table 1]

[0008]

The product of the present invention is excellent in corrosion resistance and slag penetration resistance, and a great improvement effect was obtained in an actual furnace.

(Actual furnace test conditions) -AOD furnace-Capacity: 20T-Separated part: Tuyere side slag line 15 to 25 steps-Comparison brick: Conventional product and product of this invention-Use result Use 230ch Comparison of residual thickness (Original brick thickness 500 mm) Conventional product Inventive product ・ Residual thickness (mm) 75 145 ・ Melt rate (mm / ch) 1,85 1,54 ・ Slag permeation thickness (mm) 45 23 Corrosion resistance is the rate of melt loss It was decreased by 17%, the slag penetration thickness was reduced to about half, and a great improvement could be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a filling mixture distribution.

Claims (1)

[Claims] A magnesia chrome brick, characterized in that a fine powder of electro-melted Cr ₂ O ₃ clinker having a particle size of 3 to 44 μm and a Cr ₂ O ₃ content of 99% or more is added.