JPS6018619B2 - Vibration molded refractories for tundish lining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibratory molded refractory for tundish tensioning.

A tundish used in continuous casting of molten steel is an intermediate container that temporarily receives molten steel before it enters a mold and distributes and discharges the molten steel to the mold from a nozzle provided therein, and is lined with a refractory.

As a refractory lining method, the vibration molding method, which can greatly reduce construction time, has been adopted instead of the conventional brickwork method. The refractory materials used in the vibration molding method are generally refractory materials such as pyrite-zircon, pyrite-chamotte zircon, or high alumina, but they do not have sufficient durability. Furthermore, there is a strong demand for a fireproof material with excellent durability.

In addition, basic materials such as dolomite and magnesia have been tried, but although they improve corrosion resistance, they have poor spalling resistance, and as a result, they have not been able to improve durability. The object of the present invention is to obtain a vibration-molded refractory for lining dish dishes that has both corrosion resistance and spall resistance.

The present inventor first learned that the corrosion resistance of a high alumina raw material can be improved by adding chromite. The graph in FIG. 1 shows the relationship between the weight ratio of high alumina raw material and chromium ore and the corrosion resistance index. The corrosion resistance index in this graph is set to 100 for a single high alumina raw material, and the smaller the value, the higher the corrosion resistance.

The inventor of the present invention was not satisfied with the above results, and since the present refractory is used in vibration molding, he conducted research in order to obtain close packing during molding by improving thixotropy.

Thixotropy can be improved by increasing peptizing properties, so adding a large amount of water or peptizing agent is sufficient.However, on the other hand, these additions may affect the shape retention and porosity of the refractory after molding. This results in negative effects such as, and a decrease in durability. Therefore, in the present invention, the PH of the refractory is
The above problem was solved by increasing the solvability through adjustment. That is, when alumina of 350 mesh or less and chromium ore of 1 side or less were kneaded with varying pH values and the viscosity at each pH value was measured intuitively, the results shown in FIG. 2 were obtained. In this graph, the wider the interval between the shaded areas, the lower the viscosity. The present invention was developed by paying attention to the above-mentioned facts.By weight, the high alumina raw material is 74 to 25%, and the chromite is 30 to 69%.
%, sodium silicate 1 to 3%, the particle size of 44r or less of the chromite is reduced to 10% or less, and the overall pH of the composition is 10 to 13. It is.

High alumina raw materials are effective components with high refractory and corrosion resistance, such as fused or fused alumina, sillimanite,
Used singly or in combination of two or more of synthetic mullite, bauxite, etc.

The percentage in the total formulation is that of the additive. Based on the relationship between the addition ratio of aluminum ore and sodium silicate, it is 74 to 25%. The chromium ore is used to increase the corrosion resistance of this refractory, and Masinrock chromium, Transpar chromium, Nippon chromium, etc. can be used, and the addition ratio is 30 to 69%. Below this, the corrosion resistance will decrease, and above it, the corrosion resistance will increase. However, spalling resistance decreases. Preferably it is 50-60%. This chromium ore is used in coarse and fine grains, but if a large amount of fine grains are used, overprinting may occur and peeling may occur.
The grain size of the powder should be less than 10%.

In addition, if 44r- is set to 10% or more, Mg ions and Ca ions in the chromite tend to bleed out, making it difficult to adjust the pH, which is one of the features of the present invention. Sodium silicate has a role as a binder, and the amount added is 1 to 3%. If it is less than that, the shape retention after construction will be insufficient, and if it is more than that, the corrosion resistance of the matrix will be reduced, and the spalling resistance due to oversintering will be reduced. This may cause a decrease in

As shown in Figure 2, the pH value is 10~10 for high alumina raw materials.
13 Chromium ore 10 or more tends to dissolve well, so the overall mixture is preferably 10 to 13, and most preferably 11 to 12.

NaOH, KOH, LiOH can be used as a means of adjusting the PH value.
To measure the oPH value obtained by adding an alkali source such as the following, the mixture was diluted to a ratio of 1 part water to 5 parts water using a glass electrode type PH measuring device.

Next, examples of the present invention will be given, and at the same time, experimental examples that do not belong to the present invention and conventional examples will be given for comparison, and the physical property values for each will be shown. Among the physical property values, the apparent density, bulk specific gravity, bending strength, and compressive strength of each compound were 160×
Pour into a 40 x 40 fence mold, and from the bottom of this mold 36
After applying vibration for 3 minutes with a vibrator of 00 VPm and acceleration of 80, the test piece was dried at 110 q0 for 2 hours and the resulting test piece was measured according to the JIS method.

For the rotational erosion test, a shape of (64 x 114) The converter slag was heated to 1,600℃ using an oxygen-LP gas flame, and the converter slag was heated to 30℃.
The eroded dimensions were measured after the converter slag was replaced every 30 minutes and the process was repeated four times.
The spall test was carried out by heating a test piece to 1700 oo
The sample was charged into a mold test electric furnace for 15 minutes, then removed and air-cooled repeatedly, and the sharpness and drop were observed with the naked eye.

For example, the occurrence of sharpness 1 indicates that the sharpness occurred after one rapid heating, and 〈50〉 indicates that the sharpness occurred after 5 times. Table 1 Chemical analysis of raw materials Table 2 Breakdown of formulations and their physical properties (All formulation ratios are expressed in weight %, figures in parentheses are multiplications) Among the formulations shown in Table 2 above, The refractories of Examples 1, 2, and 3 and the conventional example were used in a continuous casting tundish (opening part 1400) manufactured by Company A.
×3600VPm×bottom 1200×length 8000 fence)
A practical test was carried out by vibration molding using the core sinking method using 20 machines, 7200 VPm x 8 machines.

Test stripes As is clear from Tables 2 and 3 above, the vibration-molded refractory for tundish lining of the present invention has significantly superior corrosion resistance and spalling resistance compared to conventional refractories, and therefore has industrial value. is extremely high.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the weight ratio of the high alumina cost raw material and chromium ore and the corrosion resistance index, and FIG. 2 is a graph showing the measurement results of viscosity at different pH values. Next/Figure O 2

Claims (1)

[Claims] 1. By weight, 74 to 25% of high alumina raw material, 30 to 69% of chromite, and 1 to 3% of sodium silicate, reducing the particle size of 44μ or less of the chromite to 10% or less, and reducing the pH of the entire composition. It is characterized by being adjusted to 10 to 13,
Vibration-molded refractories for lining of tannedies.