JPS63238959A - Coating material for tundish - Google Patents

Abstract

PURPOSE:To have excellent erosion resistance and permeability to eliminate deformation and explosion and to facilitate the treatment by using porous magnesia clinker having the specific range of apparent porocity as aggregate in coating material and adding the suitable quantity of a binder to this. CONSTITUTION:The porous magnesia clinker having 30-90% apparent porocity is used as the aggregate and the binder suitably selected among inorganic binder of cement kind, phosphate, etc., or organic binder having heat curing property or self curing property, is added. This coating material has excellent erosion resistance and permeability and prevents bulging or explosion at the time of heating to dry. As the specific gravity is small, dripping is prevented at the time of coating-work and by prevention of sintering with the lining material caused by the heat insulation and by peeling from the lining material caused by remarkable volume expansion, at the time of removing the metal, the peeling is facilitated. By these characteristics, the working time is shortened, and the working ratio of a tundish is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a basic coating material for tundishes.

(Prior art) In continuous steel casting, the inner surface of the tundish located between the ladle and the mold is usually lined with a coating material with a thickness of about 5 to 30 mm. The coating material is provided for the purpose of removing the base metal adhering to the surface of the coating material by removing it each time the tundish is used, thereby preventing molten steel contamination.

Therefore, conventionally used coating materials include, for example, JP-A-59-57969 and JP-A-60-1.
As described in Publication No. 80978, it is composed of an aggregate mainly composed of magnesia clinker, to which binders such as silicates and phosphates, and appropriate amounts of organic or inorganic fibers are added. It is applied by troweling or spraying. Incidentally, the magnesia clinker used in the above is dense with an apparent porosity of about 1.5 to 8%, as in the case of general refractories.

The addition of inorganic fibers such as asbestos or organic fibers such as polyester to the coating material creates a path for water vapor during heating and drying, which prevents the coating material from blistering or exploding, and prevents it from adhering to the lining. It also has the effect of improving sex.

(Problem to be solved by the invention) However, according to the above-mentioned conventional technology, when fibers are added in large amounts, they become pill-like and are difficult to separate. Couldn't get enough. In addition, since the coating material adds about 15 to 20-t% of water during construction, its viscosity is low (and it easily drips during construction, resulting in poor workability. Furthermore, the coating material must be replaced with a new one each time the tundish is used. It had to be replaced, but the sintering made it difficult to strip and remove from the lining.

As described above, conventionally known coating materials tend to sag during application and are not easy to peel off from the lining each time the tundish is used, which leads to time-consuming application of the coating material and, in turn, to the tundish operation. This was also the cause of the decline in the rate.

The present invention has been devised in view of the above-mentioned problems, and uses highly porous magnesia clinker, contrary to conventional wisdom, to achieve a highly desirable and completely unexpected coating material for tundishes. They discovered that it is possible to obtain effects that were not previously available, and have completed the present invention.

(Means for solving problems) The configuration of the present invention will be explained below.

That is, the gist of the present invention is a coating for a tundish, which is made of porous magnesia clinker with an apparent porosity of 30 to 90% as an aggregate, and an appropriate amount of a binder added thereto. It's in the material.

Here, in the present invention, the porous magnesia clinker used has not been used in refractories that come into contact with molten metal, but it is known as an aggregate for insulation materials and can be obtained from commercial products. Apparent porosity of 30~
The reason why it is limited to 90% is that if it is less than 30%, it will become dense and the desired effect will not be obtained, and if it exceeds 90%, the corrosion resistance will be poor.The apparent porosity is preferably 50 to 7.
It is 0%. Further, the proportion of MgO component in this clinker is preferably 80 wt % or more from the viewpoint of corrosion resistance and cavity cleaning. The particle size is not particularly different from that of conventional coating materials, and may be adjusted as appropriate to coarse, medium, or fine particles.

Furthermore, the binder added in the present invention includes cements,
One or more binders may be selected and used as appropriate from inorganic binders such as phosphates and silicates, and thermosetting or self-hardening organic binders. Determine the amount.

Other additives for tundish coating materials include:
For example, silica flour, clay, slaked lime, air bubble entraining agents, fibers, etc. may be added. In particular, as fibers, for example, vinylon fiber,
It is possible to add organic fibers such as polyester fibers, cotton, pulp paper, and beaten waste paper, or inorganic fibers such as asbestos, sepiolite, and magnesia fibers, and the amount added is, for example, 5 wt% or less, preferably 0.05 to 3 wt. %. As mentioned above, fibers are effective in preventing explosions and improving adhesion, but when applying the coating material of the present invention by spraying, the addition of fibers can improve adhesion by adding fibers to conventional aggregate. Significant improvement compared to additives. As a result of using porous magnesia clinker with a low specific gravity as the aggregate, the difference in specific gravity between the aggregate and fibers is reduced, unlike conventional coating materials. This is thought to be because the specific gravity separation that accompanies this is almost eliminated.

As described above, the greatest feature of the present invention is the use of porous magnesia clinker, but some of it is used as aggregates such as dense magnesia clinker, lime tallinker, and spinel. There is no problem in replacing it with clinker or the like.

(Function) According to the present invention, since the magnesia clinker itself used as an aggregate is porous, water vapor escapes from the coating layer more easily, and compared to conventional coating materials containing fibers, when heated and dried. The effectiveness of preventing blisters and explosions is also greatly improved. In addition, the inner walls of tundishes are mostly vertical or sloped surfaces, and especially in the case of trowel coating, the aggregate is porous and the weight of the coating material is small, so not only is there almost no dripping, but
Due to the heat insulating properties of porous magnesia clinker, it is less likely to seize with the lining material. It becomes easy to peel off.

(Experiment) Hereinafter, experiments were attempted for each test item regarding the examples of the present invention as well as comparative examples.

Table 1 shows the quality and composition of the magnesia clinker used as aggregate, and Table 2 shows the examples and comparative examples of the present invention and their test results.

The aggregates of the coating materials shown in Table 2 are all 1 to 3.
u+: 30'wt%, 50wt% below 1 dragon, 0.
15 m+a or less: Particle size was adjusted to 20 wt%.

In Table 2, [Test Methods] ■ to ■ are as follows.

〔Test method〕

■About apparent porosity and bulk specific gravity; For spraying, cut out a sample piece from the applied material and
Measured according to 2205.

■About thermal conductivity; For spraying, cut out a sample piece from the applied material and test it at JIS -! at 350℃ or below. ? Measured according to 2618-79.

, ■About line change rate; 1. Heating was performed at 500°C for 3 hours, and the rate of linear change was determined.

″■Situation during heating and drying; After spraying, heating and drying was performed, and the condition of the coating layer surface was examined.

■ Sagging situation during construction; We investigated the state of dripping when applying with a trowel.

■Presence or absence of separation of fibers; After spraying, the uneven distribution of fibers within the coating layer was investigated.

■ Ease of removing base metal; We investigated whether it was easy to peel off the coating layer when removing base metal.

■Corrosion resistance: The state of erosion after use was investigated.

Considering the experimental results shown in Table 2, Examples 11hl to 12 of the present invention all showed good results in each test item. On the other hand, in Comparative Example 1, the apparent porosity was quite large at 78.3%, even though porous magnesia clinker was used as the aggregate, similar to the present invention. Although it gave good results in the test items, it was poor in terms of corrosion resistance. In addition, although Comparative Example 2 added fibers, it used dense magnesia clinker as the aggregate (corresponding to the conventional technology), so it was good only in terms of corrosion resistance. The test items were poor.

These facts indicate that porous magnesia clinker as an aggregate
If you use
Good results were obtained in all test items except corrosion resistance, and in particular, when comparing Comparative Example 2 and Examples 1 to 12 of the present invention, it is clear that the degree of apparent porosity affects the quality of corrosion resistance. This is thought to be a contributing factor.

As described above, in the present invention, the effect of using porous magna shear clinker as the aggregate and setting the apparent porosity within a predetermined range (30 to 90%, preferably 50 to 70%) was well supported.

(Effects of the Invention) According to the coating material for tundishes according to the present invention constructed as described above, firstly, it is not only possible to prevent blisters and explosions during heating and drying after construction, but also the aggregate itself used is porous. Because of its high quality, it has excellent breathability without necessarily adding fibers, and can prevent blisters and explosions even when heated and dried quite rapidly. In addition, the magnesia clinker used is porous and has inherent corrosion resistance, and the tundish coating material has unique usage conditions such that it must be replaced every time the tundish is used to remove bare metal. The problem of decreased corrosion resistance due to this can also be avoided. Furthermore, the use of porous aggregate reduces the specific gravity of the coating material, which prevents it from dripping during construction.The insulation prevents sintering with the lining material, and the significant volumetric expansion prevents bare metal from peeling off from the lining material. This makes it easier to peel off. In addition, the application and stripping of the tundish coating material according to the present invention is a hot operation, and for the above reasons, it is possible to shorten the time required for these operations, and this is not only effective in improving the operating rate of the tundish. First, it is extremely favorable from the viewpoint of working environment.

Claims (1)

[Claims] A coating material for a tundish, characterized in that it is made of porous magnesia clinker with an apparent porosity of 30 to 90% as an aggregate, and an appropriate amount of a binder added thereto.