JPS59107947A - Electromolten magnesia clinker - 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 The present invention provides electrofused magnesia clinker 1, particularly an electrofused magnesia clinker used as a raw material for refractories used in steelmaking furnaces, etc., which has a large periclase grain size and a grain boundary phase. This invention relates to an electrofused magnesia clinker characterized by high high temperature strength and corrosion resistance.

In recent years, advances in steelmaking technology have been remarkable, and as a result, extremely harsh conditions have been imposed on refractory materials used in steelmaking furnaces and other furnace equipment, such as high-temperature tapping and extended molten steel processing times. It came to be.

Steelmaking and refining furnaces 2 For example, in converters, electric furnaces, vacuum degassing equipment, and ladles, various basic refractories, especially magnesia carbon bricks of various compositions, are increasingly used depending on the conditions of use. ing. As a measure to improve the durability of magnesia carbon bricks, it is effective to increase the periclase grain size of the magnesia clinker used, and to increase the melting point of the periclase grain boundary phase to improve high-temperature strength and corrosion resistance. Are known.

Magnesia clinker can be roughly divided into sintered clinker and fused clinker. Since it is generally difficult to obtain a clinker with a periclase particle size of 11007z or more by sintering, it is common to produce a clinker with a large periclase particle size by electrofusion.

Conventionally, seawater magnesia clinker has been frequently used as a raw material for electrofused magnesia clinker.

Generally, seawater magnesia clinker with an MgO content of 98% or more has a high CaO/SiO2 weight ratio, and fused clinker made from this as a raw material has a large periclase particle size.
The periclase grain boundary phase also has a high melting point and has high corrosion resistance against ordinary converter slag, but it has the disadvantage of increasing cost.

On the other hand, magnesia clinker 2, which can be produced by a simpler process than seawater magnesia clinker, for example, magnesia clinker made from naturally abundant magnesite, generally has a low MgO content and has periclase grain boundaries. Because the weight ratio of CaO/S i 02 in the phase is low, clinker obtained by melting this has the disadvantage that although the periclase particle size is large, it is inferior in high temperature strength and corrosion resistance. Figure 1 is a graph of corrosion resistance showing this. C
When changing the aO/SiO2 weight ratio, MgO
The relationship between the corrosion resistance of fused magnesia containing molten magnesia in weight percent with respect to converter slag is shown, and the corrosion resistance when CaO/SiO2 is 0.3 is expressed as an index of 100. It is clear from the $1 diagram that corrosion resistance is improved by increasing CaO/SiO2.

The present invention aims to improve the characteristics of a magnesia clinker that can be easily and inexpensively produced. purpose.

The electrofused magnesia clinker targeted by the present invention is MgO
The content is 90 to 98% by weight.

Electrofused magnesia with MgO content exceeding 98% by weight is
A high-quality product can be produced by melting seawater magnesia clinker using a conventional method, which is different from the purpose of the present invention, which utilizes low-purity magnesia.

On the other hand, if the Mg6 content is less than 90% by weight,
It can no longer be called a magnesia clinker, and when it is used as a raw material for refractories, its characteristics as a magnesia clinker cannot be fully utilized. For example, when a large amount of CaO is contained, there is a problem that the digestibility of the resulting clinker decreases.

Furthermore, when a large amount of A L203 is contained, the corrosion resistance against slag containing a large amount of iron oxide, for example, normal steelmaking slag, decreases. Since the high fire resistance and high corrosion resistance of magnesia clinker are impaired even when other components are included, it is an essential condition for magnesia clinker that the MgO content is 90% by weight or more.

In order to achieve the above object, the present inventors added MgO from 90 to
As a result of various studies on ways to improve the properties of magnesia clinker by adding small amounts of additives to electrofused magnesia clinker containing 98% by weight, we found that the Ct203 content and CaO/SiO2 weight ratio in the clinker were appropriately controlled. It has been found that this is effective for increasing the periclase particle size of the electrofused clinker and improving its high temperature strength and corrosion resistance.

The present invention was completed as a result of repeated research based on the above-mentioned knowledge, and in an electrofused magnesia clinker containing 90 to 98% by weight of MgO, CaO/Si
The present invention relates to an electrofused magnesia clinker characterized in that the weight ratio of Cr02 and Cr203 weight% satisfy the following formula (1).

0.3-0.15+[. a0]/[Si. 2])2<
[Ct20s] ≦ 2.0-0.65 ([CaO] / [Sioz
)”7・・・・・・・・・・・・・・・(1>In the above formula, [ ] is the component content expressed in 11 weight.

If the Ct203 content in the clinker is increased, the dihedral angle at which the periclase grains contact each other increases, and the low melting point layer at the grain boundary becomes distributed in spots, which improves the hot strength and corrosion resistance of Tallin force. improves. But C? 203
If the content is too high, picrochromite (MgO・Ct
20z) etc., the growth of periclase grains is suppressed, and as a result, a fused magnesia clinker with a large periclase grain size cannot be obtained. Therefore, Cao/5i02
If the weight ratio is low, add more Cr203,
It is necessary to make the distribution of the low melting point grain boundary phase as spot-like as possible.

When the CaO/SiO2 weight ratio is high, the grain boundary phase also has a relatively high melting point, so there is no need to add a large amount of Cr203 to make the grain boundary phase into spots, but rather to promote periclase grain growth. , Ct201 content is preferably relatively low.

On the other hand, looking at the relationship between the Ca O/S I O2 weight ratio and the periclase particle size after melting, Cab/Si○.

As the weight ratio increases, C is added to the periclase grain boundaries during the cooling process.
Since aO-based compounds are easily generated, periclase grain growth tends to be suppressed.

Furthermore, if too much Cr203 is added to magnesia with a high CaO/S i02 weight ratio, Ca0-Cr2O is produced.

This produces low melting point compounds in the system, and corrosion resistance decreases.

The excellent characteristics of the electrofused magnesia clinker of the present invention will be explained by giving more specific examples.

In order to clarify the differences in the properties of the electrofused magnesia clinker obtained depending on the chemical composition of the raw materials, electrofused clinkers with various chemical compositions were manufactured.

Periclese average particle size and Cf of the produced electrofused clinker
Figure 2 shows the relationship between the '203 content and the CaO/Sio2 weight ratio as a parameter. As is clear from FIG. 2, there is a remarkable tendency for periclase grain growth to be suppressed as the Ct203 content increases, regardless of the Cao/5inzJi ratio. Also, C
a O/S i The higher the O2 weight ratio, the more Cr203
The suppression of grain growth becomes remarkable.

Next, the relationship between the Ct203 content in the electrofused clinker and the corrosion resistance is shown in FIG. 3 using the CaO/SiO2 weight ratio as a parameter. When the Cab/5i02 weight ratio is low, the corrosion resistance is markedly improved by adding Cr203;
a O/S i As the O2 weight ratio increases, Cr
The effect of adding Cr202 becomes small, and when the CaO/SiO2 weight ratio exceeds 5, the effect of adding Cr203 is hardly recognized.

From the above, the CaO/SiO2 weight ratio and Cr2O.

It was confirmed that a magnesia clinker having a large periclase particle size and high corrosion resistance can be obtained by adjusting the weight % to a range that satisfies the above formula (1), and the effectiveness of the present invention is clearly demonstrated.

[Brief explanation of drawings]

Figure 1 shows that when the cao/SiO weight ratio is changed, M
A graph showing the relationship between the corrosion resistance of fused magnesia containing 95% by weight of gO to converter slag, and FIG. 2 shows the Ct20! FIG. 3 is a graph showing the relationship between the content and the average periclase particle size, and FIG. 3 is a graph showing the relationship between the Cy203 content in fused magnesia containing 95% by weight of MgO and the corrosion resistance against converter slag. Patent Applicant Kawasaki Steel Corporation Mitsubishi Mining Cement Co., Ltd. Representative Patent Attorney Yoshio Kosugi Figure 1 Cr2O3@tH amount (wt '10) Figure 3 C "203 content (wt '10)

Claims (1)

[Claims] I An electrofused magnesia clinker containing 90 to 98% by weight of MgO, characterized in that the CaO/SiO2 weight ratio and Cr203% by weight satisfy the following formula: , 3-0.15 ([.ao
] / [S i Oz ] )2< [Cy20g
] ≦ 2.0-0.65 ([CaO] / [Sioz
)0°7 However, in the above formula, [ ] is the component content expressed in weight%.