JPH04243981A - Refractory for casting execution of silicon carbide - Google Patents

Abstract

PURPOSE:To provide corrosion resistance and spalling resistance and to improve durability by blending silicon carbide with silicon, alumina and carbon in a given weight ratio. CONSTITUTION:40-90 wt.% silicon carbide is blended with 1-5wt.% silicon having 5-150mum average particle diameter and the rest of 3-45wt.% alumina and 1-5 wt.% carbon in a ratio of carbon/silicon of <=3/7 to give a mixture. Then the mixture is optionally incorporated with a binder such as alumina cement and a dispersant such as condensed phosphate to produce refractory for casting execution of silicon carbide.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide refractory for pouring construction that has excellent slag resistance and spalling resistance.

0002

2. Description of the Related Art Casting refractories have become the mainstream of monolithic refractories because of their ease of construction. For example, the conventionally common material for pouring refractories used for the fireproof coating of blast furnace tap troughs, linings of pig iron mixer cars, and lances for hot metal pretreatment is alumina-silicon carbide-carbonaceous. For example, JP-A-6
The material disclosed in Publication No. 2-148378 is mainly made of a high alumina refractory material, to which 5 to 35% by weight of silicon carbide, appropriate amounts of pitch, silicon, etc. are added. Unexamined Japanese Patent Publication 1973
The material of Publication No. 32112 is alumina-silicon carbide-carbon, and silicon nitride, silicon alone or a mixture thereof accounts for 20 to 40% by weight of the fine powder portion.

0003

[Problem to be solved by the invention] In the steel industry, blast furnaces are becoming larger in order to pursue efficient productivity, and as a result of this rise in tapping temperature, the conditions for using refractories have become stricter. There is. As a result, the conventional refractory materials do not have sufficient service life.

0004

[Means for solving the problem] The above-mentioned Japanese Patent Application Laid-Open No. 62-14
The material disclosed in Publication No. 8378 has a silicon carbide content of 35% or less by weight. According to experiments conducted by the present inventors, it was found that since silicon carbide is a refractory raw material with low thermal expansion, its low content is the cause of poor spalling resistance. On the other hand, although the material disclosed in JP-A-48-32112 was found to be effective in improving corrosion resistance, due to the addition of large amounts of silicon nitride and silicon, sintering progressed abnormally at high temperatures, leading to cracking and cracking. This is the cause of frequent peeling.

[0005] The present invention provides a refractory for pouring construction that has both spall resistance and corrosion resistance, and exhibits sufficient durability even under recent severe usage conditions. In the present invention, silicon carbide is 40 to 90% and silicon 1 is 1% by weight.
This is a silicon carbide refractory for pouring work, characterized in that it consists of ~5%, the balance is alumina and carbon, and has a carbon/silicon ratio of 3/7 or less.

The present invention will be explained in more detail below. In addition, the unit % indicating the proportion of the compounds and additives shown below is
All percentages are by weight. In order to obtain spall resistance, it is necessary to use a material with low thermal expansion. The present invention solves this problem by containing 40% or more of silicon carbide, which is a refractory raw material with low thermal expansion. Silicon carbide has a coefficient of thermal expansion that is approximately half that of alumina. By incorporating more silicon carbide than conventional materials, spall resistance is improved.

It has been found that addition of silicon is effective in improving corrosion resistance. The Si component of silicon combines with oxygen in the air on the working surface of the refractory, and the Si component
It becomes a highly viscous body of O2. It is thought that this is to protect the working surface of the refractory from attack by corrosive agents such as slag. However, this effect of improving corrosion resistance is only exhibited by limiting the carbon/silicon ratio in the entire composition to 3/7 or less. Si, which is a silicon component, reacts in a gas phase reaction as follows.

[0008]

[Chemical formula 1]

[0009] Si in silicon and C in carbon produce SiC (β-SiC whiskers) through this reaction, and Si decreases accordingly, but in this case, Si and C react by 1 mol each, so When the carbon/silicon ratio is less than 3/7 and the amount of C is increased, Si decreases due to the formation of SiC. As a result, the amount of SiO2 produced, which has the role of protecting the working surface of refractories from attack by corrosive agents such as slag, is also reduced.
The effect of improving corrosion resistance cannot be obtained.

Although silicon greatly improves slag resistance, it also reduces spall resistance by promoting sintering strength. Therefore, in the present invention, the reduction in spalling resistance is improved by increasing the proportion of silicon carbide to 40 to 90%, and then silicon is added. If the silicon carbide content is less than 40%, the spalling resistance will be insufficient when the proportion of silicon increases. If the silicon carbide content exceeds 90%, the proportion of other components that provide the basic characteristics of the pourable material, such as fluidity, hardenability, and corrosion resistance, decreases, which is not preferable.

The alumina raw material is one or more selected from, for example, fused alumina, calcined alumina, bauxite, sillimanite, sillimanite, kyanite, synthetic mullite, andalusite, and waxite. Carbon is one or more types selected from phosphorous graphite, earthy graphite, coke, pitch, pitch coke, carbon black, and the like.

The present invention is no different from conventional cast refractories in that it uses alumina, carbon and silicon carbide as its basic composition. In this compounding composition, the present invention limits silicon carbide to 40 to 90%, and silicon 1 to 90%.
Contain 5%. Furthermore, the carbon/silicon ratio is increased to 3/
Make it 7 or less. The proportion of alumina and carbon occupies the balance of silicon carbide and silicon, respectively, for example, alumina 3~
45%, carbon 1-5%. The silicon used preferably has an average particle size of 5 to 150 μm. If the proportion is less than 1%, there is no effect of improving corrosion resistance, and if it exceeds 15%, spalling resistance decreases due to oversintering.

[0013] The carbon/silicon ratio is set to 3/7 or less. As mentioned above, if it exceeds 3/7, corrosion resistance is poor. The lower limit is, for example, 1/15. The addition of appropriate amounts of binders, dispersants, and, if necessary, fibers, metal powder, foaming agents, etc., is the same as with conventional materials. Binders include alumina cement, phosphate, silicic acid, phosphate glass, etc. Dispersants include, for example, condensed phosphates, carboxylates, lignin sulfonates, and the like.

[0014]

[Examples] Table 1 shows the compositions of Examples of the present invention and Comparative Examples. The test results will also be shown at the same time.

[0015]

[Table 1]

[0016] Adding 6% of construction moisture to each formulation,
The kneaded material was poured on a vibrating table with an excitation force of 2 G for 15 seconds, and after curing, it was heated and dried at 110° C. for 24 hours to obtain a test piece.

The test method is as follows. Spalling resistance: One side of a 120 x 60 x 50 mm test piece was inserted into an electric furnace at 1200°C, and after heating for 30 minutes,
This was taken out and cooled with water, and when cooled to room temperature, the operation of inserting it into the electric furnace for 30 minutes was repeated 10 times. Then, the number of times until peeling occurred was investigated.

Compressive strength: Measured after firing a 40 x 40 x 16 mm test piece at 1500°C for 3 hours in a reducing atmosphere. Corrosion resistance: Trapezoidal columnar test pieces with a trapezoidal cross section perpendicular to the length direction with an upper side of 65 mm and a length of 120 mm were laminated together in a drum, blast furnace slag was used as the erosion material, and the specimen was heated at 1500°C with an oxygen-propane heat source. Repeated 6 times for 1 hour. The erosion size was expressed as an index with the erosion size of Comparative Example 1 as 100. The smaller the value, the better the corrosion resistance. Actual machine test: Some of the examples and comparative examples were applied to the lining of the slag line part of the blast furnace gutter, and the service life was measured. As shown in the test results shown in the table, all the materials of the present invention are excellent in corrosion resistance, spalling resistance, and actual machine testing.

[0019]

[Effects of the Invention] As the present invention has both corrosion resistance and spalling resistance as described above, its durability is significantly improved compared to conventional materials. In the steel industry, the usage conditions for refractories are becoming increasingly strict due to the increase in the size of blast furnaces, and the value of the refractory of the present invention, which has excellent durability, is extremely high.

Claims (1)

[Claims] Claim 1: Silicon carbide is contained in a weight ratio of 40 to 40%.
A refractory made of silicon carbide for pouring work, characterized in that the silicon carbide-based refractory is made of 90% silicon, 1 to 5% silicon, and the balance is alumina and carbon, and has a carbon/silicon ratio of 3/7 or less.