JPH02204354A - Refractory - Google Patents

Abstract

PURPOSE:To obtain a refractory having corrosion resistance, wear resistance and thermal spalling resistance by constituting aggregate of such raw material particles that fine cracks are allowed to exist in the inside by exerting thermal stress. CONSTITUTION:Fine cracks are allowed to exist in the inside of raw material particles by previously exerting thermal stress. These raw material particles having the fine cracks are utilized as one part or total quantities of aggregate which consists of the coarse and intermediate particles of refractory having a particle structure in a range of fine particles from the coarse particles. Thereby propagation of a crack 3 resulting from thermal stress in refractory is progressed through the matrix 2 made of the fine particles and absorbed by the aggregate 1 and distance of propagation is made long. When the thermal stress is weak, this thermal stress is absorbed in refractory. Therefore such refractory obtained that corrosion resistance and wear resistance are equipped and also thermal spalling resistance is equipped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a refractory used in industrial furnaces and the like, and particularly to a refractory having improved thermal shock resistance.

[Conventional technology and its issues]

As is well known, refractories are subject to wear and tear due to three major causes of damage: melting, abrasion, and thermal spalling, and the ultimate challenge in this field is to obtain refractories that are excellent in all of these areas. This is a goal, but in reality it is impossible. For example, when MgO fired bricks are imparted with properties that are resistant to melting damage, they are significantly inferior in heat spalling resistance, and their lifespan is shortened due to peeling and wear. In the case of carbon-containing bricks such as Mg0-C, whose usage has been increasing recently, it can be said that the refractories have come one step closer to achieving this goal, but there are still strong concerns from users regarding their total service life. It is an undeniable fact that there is dissatisfaction.

Furthermore, as disclosed in Japanese Patent Publication No. 57-27058, there is a method of applying cold stress to the refractory itself to improve its heat spalling resistance. Although satisfactory results have been obtained with this method, it is still unsatisfactory due to the recent situation in which large-scale processing and high-temperature processing are required. The reason for this is that cracks are generated in the refractory matrix itself, and a decrease in corrosion resistance and abrasion resistance is unavoidable.

The present invention was proposed in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a refractory having corrosion resistance, abrasion resistance, and heat spalling resistance.

[Means to solve the problem]

In order to achieve the above object, the present invention uses part or all of the raw material grains, which have been subjected to thermal stress in advance so as to have minute cracks inside, as the aggregate.

[For production]

The particle structure of all refractories ranges from coarse particles to fine particles, and the coarse to medium particles, which are called aggregate, are especially
It can be said that it only contributes to some extent to the improvement in corrosion resistance that accompanies the improvement in density, and hardly contributes to strength (wear resistance) or heat spalling resistance. On the other hand, the matrix composed of fine particles is involved in all three elements: corrosion resistance, abrasion resistance, and spalling resistance. In other words, if the matrix is porous and has weak bonds, it will naturally have poor corrosion resistance and wear resistance, and the generation of thermal stress will not originate from the aggregate in the refractory, but from the thermal gradient of the matrix. Considering what happens from , it can be said that the configuration state of the matrix controls the above three elements.

It is clear that if the matrix is strengthened to improve corrosion resistance and abrasion resistance, the heat spalling resistance will deteriorate, but this heat spalling resistance has a significant effect on corrosion resistance and abrasion resistance. It is also affected by the condition of the aggregate, which does not affect most of the time.

That is, as shown in Fig. 1, the crack 3 propagates in the refractory due to thermal stress, penetrates the matrix 2, becomes a large crack, and finally peels off. As such, the aggregate particles 1 remain as they are without cracking unless a very large thermal stress is applied to them. This indicates that cracks that normally propagate within the matrix 2 bend at the aggregate and selectively propagate only through the matrix. Of course, this crack 3
The shorter the propagation distance, the more cracks in the refractory3
It is clear that this leads to faster peeling.

Here, if internal cracks are made to exist in the aggregate 1 in advance and the cracks 3 due to new thermal stress propagated from the matrix 2 are absorbed, the propagation distance becomes longer as shown in Fig. 3. If the thermal stress is weak, the thermal stress will be absorbed within the refractory.

Here, it is clear that it is preferable that the amount and size of microscopic clumps contained in the aggregate grains be as large as possible and as small as possible, but it is impossible to generate them using mechanical stress. Thermal stress is used because it is relatively easy to control.

That is, in most cases, refractory raw materials are crushed and sized before use, and although the grains break when mechanically crushed, cracks cannot remain within the grains. On the other hand, when aggregate particles before use are heated to a certain temperature and then cooled, many microcracks that cannot be seen with the naked eye occur within the aggregate particles depending on the magnitude of the temperature difference at that time.

Therefore, the amount and size of cracks can be controlled by controlling the temperature difference between heating and cooling, and heat treatment can be performed depending on the purpose. In addition, the amount of aggregate containing the microcracks contained in the refractory is sufficient to impart the necessary spalling resistance to the refractory, but of course, the entire amount can be replaced with the particles. There is no problem. It goes without saying that the present invention can be applied to all existing refractories and raw material grains for the above reasons.

C Example] The present invention will be illustrated by examples.

The basic formulation was carried out in the following example.

Here, the composition of the Mg0 grains used is It is.

Among the particles used in the basic formulation, 5 to 1 m, 1 to 0.
Each of the 5rr+rn grains was prepared in advance with a temperature difference of 50%.
The process was carried out in a small rotary kiln 10 as shown in FIG. 4, which has a temperature of 0 to 700°C. These particles do not show any cracks or the like, but when observed under a microscope, they are several μm thick.
It was observed that tens to hundreds of wide cracks were present in one particle.

When the specific gravity was measured, it was found to be 3.27, which was found to be almost unchanged from before the treatment. The treated aggregate was replaced with the basic mixture and mixed in a roll mixer in the usual manner, and then molded into a shape of 65 x 114 x 230 mm. The molding pressure was 800 kgf/cm2.

After that, it was dried at 110°C for 24 hours, and then dried at 1700°C for 10 hours.
Fired for hr. The physical properties of this brick are shown in Table 1 as Example 3.

In addition, 40w of Mg05-1mm in the formulation of the implementation product ■
Table 1 shows the physical properties of Example 2, in which only t% was treated powder and the rest was untreated powder, and the following steps were the same as in Example 1.

Furthermore, bricks were made using the untreated grains according to the basic formulation, and their physical properties are shown in Table 1 as a comparative example.

Table 1 (Physical property values) As is clear from Table 1, although the specific gravity, bending strength (abrasion resistance), and corrosion resistance of the processed products ■ and ■ are comparable to conventional products, they have poor heat spalling resistance. It's extremely good.

〔Effect of the invention〕

Since the brick according to the present invention applies thermal stress only to the aggregate, it exhibits excellent heat spalling resistance and can be applied to any industrial furnace.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are diagrams showing the propagation of cracks in the refractory, and FIG. 4 is a diagram showing the manufacturing process of raw material grains used in the refractory of the present invention.

Claims (1)

[Scope of Claims] [1] A refractory characterized by using part or all of the raw material grains, which have been subjected to thermal stress in advance to form microcracks therein, as aggregate.