JPS5850945B2 - Refractory material for blast furnace gutter vibration molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lining material for a tap trough attached to a blast furnace, and more particularly, to a refractory material for vibratory molding of a blast furnace trough that has excellent corrosion resistance and wear resistance against hot metal slag.

In recent years, blast furnaces have become larger, operating temperatures have become higher, and the amount of slag has increased due to increased operating temperatures and pressures. Significant chemical erosion.

Therefore, when the lining material of the gutter is eroded beyond a certain level, tapping of the blast furnace is stopped, and the lining material is completely replaced or partially repaired each time.

Therefore, there is a demand for the development of highly durable refractory materials in order to reduce the number of replacements and repairs mentioned above and increase the amount of iron tapped by increasing the durability of the lining material.

Most conventional refractory materials for tap runners use alumina, synthetic mullite, chamotte, etc. as aggregates, and are generally made by adding silicon carbide and graphite to the fine grains and adding clay, etc. as a binder. The interior is lined with this fireproof material by stamping.

When stamped refractory material is actually used as a tap runner, a vortex of falling molten pig iron and slag during tapping occurs at the point where the molten pig iron and slag fall, and the refractory material is always subject to mechanical and chemical damage. The refractory material is severely eroded locally by erosion, and even though other parts are still usable, the entire gutter material must be replaced or the number of partial repairs must be increased.

In addition, in stamping, the refractory material is successively tamped down using an air rammer, etc., and the inner lining is compacted, so the surface is well compacted, but the overall compaction is poor, and in addition, layered cracks occur in the direction perpendicular to the pressing direction. It is easy to occur, and the construction has drawbacks such as heavy labor and high-temperature work that continues for a long time.

A vibration molding construction method has been developed that solves these drawbacks at once, and is rapidly coming into use.

The above construction method is an application of the principle of the vibrating acid type method, in which the refractory material exhibits fluidity when vibration is applied while applying appropriate pressure to the molded inner frame that can be compressed.The fluidized refractory material is then molded. As the inner frame sinks, the molding progresses into the desired shape, and when the vibrations are stopped, the refractory material immediately solidifies, and the molded inner frame is removed, completing the construction.

As mentioned above, the present invention relates to a refractory material for blast furnace gutter vibration molding used in the recently developed vibration molding method, and its features include 70 to 90% alumina, 7 to 20% silicon carbide, and carbon by weight. A binder is added to a mixture consisting of 1 to 5% metallic silicon or 2 to 5% silicon nitride and 7 to 20% of alumina fine powder of 48 mesh or less in the alumina to improve corrosion resistance, wear resistance, and thixotropy. This is a refractory material for vibration molding with improved heat resistance.

In the present invention, the alumina used as aggregate is high purity sintered alumina and fused alumina.

In particular, the alumina of 48 mesh or less used in the matrix part is suitable for electric melting of neutral and high-purity dust.

If the total amount of alumina added is less than 70%, corrosion resistance and wear resistance will decrease when used as a refractory material for a tap trough.

If it is 90% or more, the hot strength becomes small.

The inventors compared the corrosion resistance of fused alumina with the composition shown in Table 1 and silicon carbide against hot metal and molten slag using a drum-type rotary erosion test, and as a result, they confirmed that alumina has higher corrosion resistance.

In addition, when the matrix part is composed of silicon carbide and carbon, the matrix part is eroded faster than the aggregate part.
The remaining aggregate portion cannot but fall off without fully demonstrating its corrosion resistance.

In order to eliminate this phenomenon, the corrosion resistance of the matrix portion was improved by adding fine alumina powder of 48 mesh or less in a range of 7 to 20%.

As mentioned above, the corrosion resistance of the matrix part has been improved by the limited use of alumina fine powder, but in order to further maintain a uniform balance of the entire refractory material, it is necessary to increase the hot strength of the matrix part, and in this case metal silicon or nitride Silicon was added in an amount of 2 to 5% based on the total amount to improve its uniformity.

In addition, alumina fine powder of 48 mesh or less in alumina
From the addition of ~20%, a desirable thixotropy as a refractory material for vibration molding was developed, and an appropriate flow state was obtained for gutters, which generally have a large shape, making construction extremely easy.

If the alumina particles with a mesh size of 48 or less in the alumina are less than 7%, no improvement in the corrosion resistance of the matrix part can be expected, and if the content exceeds 20% by weight, the sinterability will decrease, resulting in a decrease in mechanical strength. This will advance the melting loss.

Silicon carbide has high corrosion resistance, high thermal conductivity, and low expansion properties, and at the same time, has the property of being difficult to wet with hot metal and molten slag.

It is important for refractory materials used in tap runners to have the property of not being easily wetted by hot metal and slag.This property prevents penetration of hot metal and slag, especially hot metal, into the refractory material, and prevents changes and deterioration of the internal structure of the refractory material. This results in improved corrosion resistance.

Considering the above properties, the results of experimental studies show that the optimum amount of silicon carbide added in alumina-silicon carbide refractory material is 7 to 20.
% by weight.

If the silicon carbide content is less than 7% by weight, the effect of adding calories is small.
If it is 0% by weight or more, corrosion resistance will decrease.

However, silicon carbide reacts with alkaline earth metal oxides in the slag.

Furthermore, since the viscosity of the slag is low, silicon carbide alone is not sufficient to prevent the slag from penetrating into the refractory material, so it is necessary to add a carbon component to further prevent the slag from penetrating.

Carbon with advanced graphitization has the disadvantage of becoming brittle to oxidation when heated in an oxidizing atmosphere, while carbon with volatile content has the advantage of increasing the strength of the structure by forming carbon bonds during the heating process.

Therefore, after various studies on carbon with volatile content, it was found that the optimum effect of preventing penetration of slag is when added in the range of 1 to 5%.If it is less than 1%, the addition effect is not sufficient, and if it is added more than 5%, corrosion resistance is improved. On the contrary, it decreases.

Metallic silicon or silicon nitride, which constitutes the matrix like silicon carbide, carbon, and fused alumina, is 2 to 5% in order to improve the strength and wear resistance of silicon carbide, graphite, and fused alumina at high temperatures. If the amount of additive D is less than 2%, no wear erosion effect can be obtained, and if it is more than 5%, not only is it expensive, but the effect is proportional to the amount of additive P. It is not economically advisable to do so.

The present invention will be described below with reference to Examples.

Examples Table 1 shows the chemical compositions of the raw materials used in the products of the present invention and comparative products.

Further, Table 2 shows the blending ratios of the products of the present invention, comparative products, and conventional products, and Table 3 shows the physical properties of each of the various blends.

Among the measured values in Table 3, the apparent specific gravity, bulk specific gravity, and porosity are those obtained by firing in air at 110°C for 24 hours, and at 700°C.
The specimens fired for 5 hours and those fired at 1400° C. for 1 hour were cut with a cutter into a shape measuring 40 mm long x 80 mm wide x 30 mm high, and each sample was measured.

The bending strength shows the value when hot, and the bending strength is 40 x 1
A specimen was prepared with a size of 60 x 30 mm and heated to 700℃.
The specimens that had been heated and held for 5 hours and those that had been heated and held for 1400 x 1 hour were strained with a span of 100 threads and measured while still in the hot state.

Corrosion resistance was tested using a rotating drum erosion test method, in which a total of 8 specimens (2 each of the present invention) and 18 comparative and conventional products of the same size (2 each) were combined into a drum body and lined. Blast furnace pig iron and blast furnace slag are contained in it at a weight ratio of 2.
: Pour a predetermined amount in Step 1, dissolve, and discharge the melt after 30 minutes.

After discharging, the same amount and the same weight ratio were added and dissolved again, and the same operation as the first was repeated four times for a total of 6 hours, and then the entire amount was taken out and the dimensions of erosion were measured.

The physical property values in Table 3 indicate the amount of corrosion as an index, and the smaller the value, the better the corrosion resistance.

The product of the present invention, which is made by mixing raw materials with the composition shown in Table 1 at the mixing ratio shown in Table 2, has a thickness of /16.1 to /164, and the comparative product has a flatness of 5 to /1.
When the compound No. 67 is put into an outer frame separately provided for the large gutter of a blast furnace, and an inner frame equipped with a vibrator and a weight is placed in the outer frame, the vibrator is activated. Degeneration occurs,
The refractory was in a fluid state favorable to by-products, and the inner frame sank.

In particular, when comparing //61 to /16.4 to Kuzu 5 to Kuzu 7, the inner frame sinks by 1 even though the moisture content, load, and shape are the same.
It was about 0% faster.

After confirming that the inner frames had sunk to the specified position, the vibration was stopped, each inner frame was removed and air-dried for 24 hours. /6.
4 and scrap 5 to polished 7 were alternately lined and tapped, the result was approximately 45,000 tons of iron passing through without repair, and the remaining dimensions were also relatively large. Although no melting damage was observed except for the areas where the slag eddies were intense, the remaining dimensions of comparative products/V) 5 to 467, which were laminated alternately in the same area, were small.

If the entire surface had been lined with the steel sheets of the present invention from 1 to 164, it would have been possible to pass through 50,000 tons of iron.

In addition, the unrepaired pig iron capacity of the conventional product due to stamp construction is approximately 35
,000 tons, and the corrosion damage was considerably advanced.Comparing this, the refractory material for vibration molding of the present invention has significantly improved corrosion resistance by improving the I-IJ rack part to the same level as aggregate. It has increased.

That is, by using the fireproofing material of the present invention, it is expected that the lifespan will be extended by about 20% or more compared to conventional stamped fireproofing materials, and the construction time will be about 1/10th. The number of man-hours can be reduced to 115,
The material costs and labor costs required for repairing the blast furnace tap trough can be significantly reduced.

In addition, from the viewpoint of the working environment, the time required for high-temperature work in front of the furnace is shortened, and the effect is significant and effective.

The erosion ratio is shown as an index. The smaller number is Shows high corrosion resistance.

Claims (1)

[Claims] 1 70-90% alumina and 7-20% silicon carbide by weight
%, carbon 1-5%, metallic silicon or silicon nitride 2-5%
%, and a binder is added to a mixture containing 7 to 20% of alumina fine powder of 48 mesh or less in the alumina.