JP3044568B2 - Magnesia clinker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention has excellent slag erosion resistance and is suitable as a raw material for refractory for converters such as refractories for steelmaking furnaces, particularly magnesia carbon bricks. Clinker (especially seawater magnesia clinker).

The clinker referred to in the present invention generally refers to one in which a portion having a low melting point of a component is melted by firing and the whole is solidified to form a lump.

[Problems to be solved by conventional technology and invention]

Recent developments in steelmaking technology have been remarkable. The refractories and raw materials used for them have also been increasingly upgraded in response to this development. For this reason, since it is expensive as a source of magnesia as a raw material of a steelmaking furnace refractory, particularly a raw material of a mag carbon brick, electrofused magnesia, which has not been conventionally used, has been used in severe parts. Inexpensive sintered magnesia (especially seawater magnesia clinker) which can replace electrofused magnesia is eagerly desired.

It is said that a magnesia clinker suitable as a raw material for the mag-carbon brick is preferably a magnesia having a large crystal diameter, a high bulk specific gravity, a high MgO purity, and a high CaO / SiO ₂ ratio. Therefore, magnesia clinkers having these compositions and physical properties have been used alone or in combination with electrofused magnesia as raw materials for mag carbon bricks.

Conventionally, so-called electro-fused magnesia is known as a large crystal, high-bulk specific gravity magnesia, which is obtained by completely melting a magnesia clinker or the like by electroheating and then solidifying. But,
Since the production of electrofused magnesia is small and expensive, research and development of a magnesia clinker to replace electrofused magnesia have been conducted. However, unlike electrofused magnesia, in the clinker formed by firing, trace amounts of impurities and pores inevitably remain at the magnesia crystal grain boundaries, causing densification and alienation of crystal growth.

In general, clinker is manufactured by molding magnesium hydroxide produced by the reaction of slaked lime with seawater or brine, calcining magnesium hydroxide once at a temperature of 600 to 1,000 ° C, or calcining natural magnesite. The powdered and lightly-baked magnesia obtained by molding is molded and then fired at a high temperature of 1,900 ° C. or more. The magnesia clinker thus obtained has a crystal diameter of 20 to 40 μm,
The bulk specific gravity was 3.40 g / cc or less.

Fe as a method to increase the crystal diameter of magnesia clinker
There are methods of adding a large amount of ₂ O ₃ and SiO ₂ and using magnesite containing them as a raw material, but all of these methods have low purity and low bulk specific gravity.

As a method of increasing the crystal diameter of the magnesia clinker and at the same time, increasing the bulk specific gravity, there are a method of high purification and a method of adding an additive such as ZrO ₂ .

How to increase the MgO is hydrated magnesia fired at once 800～1,400 ° C., except for calcium oxide, and a method of removing B ₂ O ₃ methods and advance sea water to re-fired in a special resin is proposed I have. However, both have the drawback that the manufacturing process becomes complicated and the manufacturing cost increases significantly.

As a method using an additive, a method of adding ZrO ₂ disclosed in JP-B-60-44262 or JP-A-61-8365.
There is a method of simultaneously adding ZrO ₂ and magnesia crystal disclosed in Japanese Patent No. Even refractories using these as raw materials have not completely satisfied the recent demand for high quality. There are many papers on the effect of adding Mn ₂ O ₃ , NiO, and TiO ₂ , but these are limited to low-temperature baking using ultra-high-purity reagents as magnesium sources, and have a bulk specific gravity (relative density). ), But those having a large crystal diameter have not been obtained.

An object of the present invention is to provide a magnesia clinker suitable for a raw material for a refractory for a steelmaking furnace, particularly a magnesia carbon refractory having excellent erosion resistance.

[Means for solving the problem]

The present invention has been made in view of the above-mentioned object, and as a result of intensive studies on the development of an excellent magnesia clinker, the present invention has been achieved.

That is, the present invention comprises: a) 0.05 to 2.0 wt% of at least one selected from Mn ₂ O ₃ , NiO, TiO ₂ , BeO, Nb ₂ O ₅ , b) MgO purity of 97.0 wt% or more , c) the content of CaO is not more than 2.0 wt%, d) the content of SiO ₂ is below 0.4 wt%, e) the content of B ₂ O ₃ is not more than 0.1wt%, f) MgO , CaO, SiO ₂ , B ₂ O ₃ content of impurities other than 2.0 wt
G) Bulk specific gravity and apparent porosity are 3.45 g / cc or more, respectively.
And h) a magnesia clinker characterized in that the average crystal diameter of magnesia is 80 μm or more.

Mn ₂ O _3, NiO in the present invention has the effect of _{TiO 2, BeO, Nb 2 O} 5 is to improve the resistance to erosion of the refractories, the amount of addition is 0.05 to 2.
0 wt%. That is, if the content is less than 0.05% by weight, the effect of addition is not observed.

In the present invention, in order to improve the erosion resistance of the refractory, the purity of MgO needs to be 97.0 wt% or more,
t% or more is preferable. CaO is 2.0wt% or less, 0.01-1.8wt%
Is preferred. SiO ₂ must be 0.4 wt% or less, 0.3
wt% or less is preferred. B ₂ O ₃ needs to be 0.1 wt% or less, and preferably 0.01 to 0.06 wt% or less. Furthermore, MgO, CaO,
The content of impurities other than SiO ₂ and B ₂ O ₃ needs to be 2.0 wt% or less, and it is particularly preferable that both Al ₂ O ₃ and Fe ₂ O ₃ are 0.1 wt% or less. Refractories using the magnesia clinker as a raw material in the above range exhibit high corrosion resistance. A refractory using a magnesia clinker having a composition in the other range as a raw material has poor corrosion resistance and is not practical.

In the present invention, it is known that increasing the density of the raw material clinker greatly contributes to improving the corrosion resistance of the refractory. Also in the present invention, a refractory using a magnesia clinker having a bulk specific gravity of 3.45 g / cc or more and an apparent porosity of 2.5 Vol or less exhibits excellent erosion resistance.

In the present invention, the crystal diameter of magnesia needs to be 80 μm or more, and preferably 100 μm or more.
A refractory using a magnesia clinker having a crystal diameter of 80 μm or less has poor corrosion resistance and is not practical.

The bulk specific gravity, apparent porosity, and crystal size of the magnesia clinker obtained in the present invention are respectively the Japan Society for the Promotion of Science
Gakushin Method 2: `` A method for measuring the apparent porosity, apparent specific gravity and bulk specific gravity of magnesia clinker '' proposed by the 124 Committee and Gakushin Method 2: `` Measurement of the size of periclase in magnesia clinker and its recording method ".

The chemical analysis of magnesium hydroxide and magnesia clinker was measured according to Gakushin method 1: "Chemical analysis method of magnesia clinker".

That is, the bulk specific gravity and apparent porosity of the magnesia clinker are measured as follows.

Crush the whole particle size of magnesia clinker, 3.36 ~ 2.00
Choose a particle size of mm and weigh accurately about 15 g. (W ₁ g) A magnesia clinker sample was placed in a 1 mm wire mesh basket, the beaker containing the basket was placed in a desiccator, the pressure was reduced for about 1 hour, and then white kerosene was removed from the separating funnel into the beaker. Insert until it is full. afterwards
Exhaust for 20 minutes.

After evacuating, remove the beaker from the desiccator, and further remove the basket containing the sample from the beaker,
Accurately weigh in oil. (W ₂ g) Take out the sample from the basket, remove the oil adhering to the surface without excess and deficiency, and measure the weight quickly. (W
₃ g) Calculation Here, W ₄ : weight of the basket alone in oil ρ: specific gravity of white kerosene The average crystal diameter was measured as follows.

Take 5 grains of about 7mm, cut into almost half and embed in resin.

While observing the surface-polished sample with a reflection microscope, three average portions are selected, and the length of the crystal in the vertical direction and the length in the horizontal direction are measured for the observer.

This length is defined as the crystal diameter, and their average value is defined as the average crystal diameter.

 The analysis of the chemical composition was performed as follows.

CaO, SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ , Mn ₂ O ₃ , NiO, TiO ₂ , BeO, Nb ₂
Analysis of O ₅ was carried out as follows.

The sample reduced by the two-way separator is finely pulverized by a desk mill to about 10 μm or less.

Approximately 1 g is accurately measured and dissolved by heating with hydrochloric acid.
Dilute to.

Each element is quantified using an argon plasma emission spectrometer. Expressed in terms of oxide.

MgO was expressed as a difference from the above-described oxide-converted value of an element other than MgO.

In addition, the amount of erosion calculated from the thickness of the brick piece before and after the test is represented by the value of Comparative Example 2 as 100. The thickness of the brick piece was measured at three places with a vernier caliper, and expressed as an average value. The amount of erosion is represented by the following equation.

Amount of erosion = thickness of brick piece before test-thickness of brick piece after test Example The present invention will be described in detail below with reference to examples.

Examples 1 to 5 The chemical composition is MgO = 67.0 wt%, CaO = 0.68 wt% in terms of oxide.
%, SiO ₂ = 0.14 wt%, Fe ₂ O ₃ = 0.04 wt%, Al ₂ O ₃ = 0.04 wt%,
Magnesium hydroxide with B ₂ O ₃ = 0.04 wt%
Mn ₂ was added to the light-burned magnesia obtained by maintaining the temperature at 0 ° C for 3 hours.
O ₃ , NiO, TiO ₂ , BeO, Nb ₂ O ₅ each 0.5wt% to MgO
And mixed by a mixer. It was press-molded at a pressure of ² ton / cm ² to obtain a pellet (10 mmφ, 5 mmH), and this pellet was kept at a maximum temperature of 2,000 ° C. for 1 hour in an oxygen-propane furnace. Table 1 shows the bulk specific gravity, apparent porosity, average crystal diameter and chemical composition of the thus obtained magnesia clinker.

Next, using the obtained magnesia clinker as a raw material, a piece of mag-carbon brick was prepared under the experimental conditions shown in Table 2, and a slab erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

Examples 6 to 10 The chemical composition is MgO = 67.0 wt%, CaO = 0.10 wt% in terms of oxide.
%, SiO ₂ = 0.14 wt%, Fe ₂ O ₃ = 0.04 wt%, Al ₂ O ₃ = 0.04 wt%,
Magnesium hydroxide with B ₂ O ₃ = 0.04 wt%
Mn ₂ was added to the light-burned magnesia obtained by maintaining the temperature at 0 ° C for 3 hours.
Any one of O ₃ , NiO, TiO ₂ , BeO, Nb ₂ O ₅ for MgO
0.5 wt% was added and mixed by a mixer. 2ton /
A pellet (10 mmφ, 5 mmH) was obtained by pressure molding at a pressure of cm ^{2, and} the pellet was subjected to a maximum temperature of 2,000 in an oxygen-propane furnace.
C. for 1 hour. Table 1 shows the bulk specific gravity, apparent porosity, average crystal diameter and chemical composition of the thus obtained magnesia clinker.

Next, using the obtained magnesia clinker as a raw material,
Mag carbon brick pieces were prepared under the experimental conditions shown in Table 2,
A slag erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

Examples 11 to 12 Magnesium hydroxide used in Examples 6 to 10 was heated in an electric furnace.
BeO was added to the lightly-baked magnesia obtained by holding at 950 ° C for 3 hours.
Was added to MgO in an amount of 0.2 wt% and 1.0 wt%, and mixed by a mixer. It was press-molded at a pressure of ² ton / cm ² to obtain a pellet (10 mmφ, 5 mmH).
It was kept at a maximum temperature of 2,000 ° C. for 1 hour in a propane furnace. Table 1 shows the bulk specific gravity, apparent porosity, average crystal diameter and chemical composition of the thus obtained magnesia clinker.

Next, using the obtained magnesia clinker as a raw material, a piece of mag carbon brick was prepared under the experimental conditions shown in Table 2, and a slag erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

Example 13 MgO = 67.0 wt%, CaO = 0.67 wt% in terms of oxide composition
%, SiO ₂ = 0.14 wt%, Fe ₂ O ₃ = 0.04 wt%, Al ₂ O ₃ = 0.04 wt%,
Magnesium hydroxide with B ₂ O ₃ = 0.04 wt%
BeO was added to the lightly-baked magnesia obtained by maintaining the temperature at 0 ° C for 3 hours.
0.5 wt% was added to MgO and mixed by a mixer.
It is molded under pressure at a pressure of ² ton / cm ² and pellets (10 mm
φ, 5 mmH), and the pellets were kept at a maximum temperature of 2,000 ° C. for 1 hour in an oxygen-propane furnace. Table 1 shows the bulk specific gravity, apparent porosity, average crystal diameter and chemical composition of the thus obtained magnesia clinker.

Next, using the obtained magnesia clinker as a raw material,
Mag carbon brick pieces were prepared under the experimental conditions shown in Table 2,
A slag erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

Comparative Example 1 Lightly-baked magnesia obtained by holding magnesium hydroxide having the chemical composition used in Examples 1 to 5 at a temperature of 950 ° C. for 3 hours in an electric furnace was molded under pressure at a pressure of ² ton / cm ^2. Pellets (10
mmφ, 5 mmH), and the pellets were kept at a maximum temperature of 2,000 ° C. for 1 hour in an oxygen-propane furnace. The bulk specific gravity, apparent porosity of magnesia clinker thus obtained,
Table 1 shows the average crystal diameter and the chemical composition.

Next, using the obtained magnesia clinker as a raw material, a piece of mag carbon brick was prepared under the experimental conditions shown in Table 2, and a slag erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

Comparative Example 2 Magnesium hydroxide used in Examples 6 to 10 was used in an electric furnace.
Magnesia oxide obtained by holding at 950 ° C for 3 hours
Pellet (10mmφ, 5mmH) by pressure molding with a pressure of n / cm ²
And the pellets were heated in an oxygen-propane furnace at a maximum temperature of 2,000.
It was kept at 0 ° C. for 1 hour. Table 1 shows the bulk specific gravity, apparent porosity, average crystal diameter and chemical composition of the thus obtained magnesia clinker.

Next, using the obtained magnesia clinker as a raw material,
Mag carbon brick pieces were prepared under the experimental conditions shown in Table 2,
A slag erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

Comparative Example 3 Magnesium hydroxide used in Example 2 was placed in an electric furnace at 950.
BeO is added to light-burned magnesia obtained by maintaining the temperature at ℃ for 3 hours.
2.1 wt% was added to gO and mixed by a mixer.
It is molded under pressure at a pressure of ² ton / cm ² and pellets (10 mm
φ, 5 mmH), and the pellets were kept at a maximum temperature of 2,000 ° C. for 1 hour in an oxygen-propane furnace. Table 1 shows the bulk specific gravity, apparent porosity, average crystal diameter and chemical composition of the thus obtained magnesia clinker.

Next, using the obtained magnesia clinker as a raw material,
Mag carbon brick pieces were prepared under the experimental conditions shown in Table 2,
A slag erosion test was performed using a rotary erosion furnace under the experimental conditions shown in Table 2. Table 1 shows the results.

[Effect of the Invention] The use of the magnesia clinker of the present invention showed excellent slag erosion resistance. Thus, the magnesia clinker of the present invention is suitable as a raw material for refractories for steelmaking furnaces such as magcro bricks as well as mag carbon bricks.

Claims (1)

(57) [Claims] 1. a) 0.05 to 2.0 wt% of at least one selected from Mn ₂ O ₃ , NiO, TiO ₂ , BeO, Nb ₂ O ₅ ; b) MgO purity of 97.0 wt% or more; c) the content of CaO is not more than 2.0 wt%, d) the content of SiO ₂ is below 0.4 wt%, e) the content of B ₂ O ₃ is not more than 0.1wt%, f) MgO, The content of impurities other than CaO, SiO ₂ and B ₂ O ₃ is 2.0 wt
G) Bulk specific gravity and apparent porosity are 3.45 g / cc or more, respectively.
And 2.5% by volume or less; h) Magnesia clinker, wherein the average crystal diameter of magnesia is 80 μm or more.