[0001] The present invention relates to a mud material used for
filling the taphole of a blast furnace.
Background
[0002] The taphole portion of a blast furnace is subjected to
severe refractory wear caused by high heat and abrasion from the discharge of molten iron slag, and in many cases, there is a problem of a rise in temperature due to refractory wear at the taphole lower portion as the furnace ages.
A conventional technique (refer to Patent Literature 1, for example) is known in which a titania raw material is added to the mud material to produce TiC and TiN, which have viscosity, to protect the refractory at the taphole lower portion.
[0003] However, the mud material undergoes excessive sintering
due to production of TiC and TiN, and the excessive sintering imparts a higher strength to the mud material, resulting in the problem of difficulty in opening a hole.
Citation List Patent Literature

[0004] Patent Literature 1: Japanese Patent Application
Publication No. S64-39310
Summary
Technical Problem
[0005] An object of the present invention is to provide a mud
material that can suppress the difficulty in opening a hole while
protecting the taphole lower portion of a blast furnace.
Solution to Problem
[0006] According to one aspect of the present invention, the
following mud material is provided.
A mud material for filling the taphole of a blast furnace containing a refractory raw material and a binder, the mud material containing 3% to 20% by mass inclusive of a titania raw material with a grain size less than 0.3 mm and 3% to 15% by mass inclusive of a carbon raw material with a grain size less than 10 µm in 100% by mass of the refractory raw material.
Advantageous Effects of Invention
[0007] The mud material according to the present invention
contains 3% to 20% by mass inclusive of a titania raw material with a grain size less than 0.3 mm in 100% by mass of the refractory raw material, and therefore TiC and TiN are efficiently produced from

the titania raw material (TiO2). The TiC and TiN have viscosity, and therefore protect the refractory at the taphole lower portion.
The mud material according to the present invention also contains 3% to 15% by mass inclusive of a carbon raw material with a grain size less than 10 µm in 100% by mass of the refractory raw material. The ultrafine powder of a carbon raw material with a grain size less than 10 µm has an extremely large specific surface area and a carbon raw material has a high melting point. Therefore, the aforementioned excessive sintering and difficulty in opening a hole can be suppressed by including the titania raw material.
Furthermore, since the mud material contains the ultrafine powder of the carbon raw material with a grain size less than 10 µm, an effect is exhibited in which a reaction with the TiO2 easily produces TiC. This TiC protects the refractory at the taphole lower portion.
Description of Embodiments
[0008] Containing a refractory raw material and a binder
similar to a conventional mud material, the mud material according to the present invention is characterized in containing 3% to 20% by mass inclusive of a titania raw material with a grain size less than 0.3 mm and 3% to 15% by mass inclusive of a carbon raw material with a grain size less than 10 µm in 100% by mass of the refractory raw material. The mud material according to the present invention thereby suppresses the difficulty in opening a hole with the taphole

lower portion of the blast furnace being protected as described
above.
[0009] The grain size of the titania raw material is restricted
to less than 0.3 mm in order to enhance the reactivity of the titania
raw material (TiO2) so as to efficiently produce TiC and TiN from
the titania raw material (TiO2).
If the content of the titania raw material with a grain size less than 0.3 mm is less than 3% by mass, TiC and TiN are not adequately produced and the function of protecting the refractory at the taphole lower portion is not obtained. In contrast, if the content of the titania raw material with a grain size less than 0.3 mm exceeds 20% by mass, the aforementioned excessive sintering is caused by the titania raw material and it is difficult to open a hole. The content of the titania raw material with a grain size less than 0.3 mm is favorably 8% to 15% by mass inclusive.
[0010] The term titania raw material refers to titania (TiO2)
or a refractory raw material containing titania and generally having a TiO2 content of at least 60% by mass. However, the price of the titania raw material becomes higher as the TiO2 content becomes higher, and thus the TiO2 content of the titania raw material is favorably 60% to 90% by mass inclusive from the perspective of reducing costs and is more favorably 80% to 90% by mass when the effects are taken into consideration.
There are natural and artificial titanium raw materials, and titania raw materials can be classified as rutile or anatase

according to the crystal form. The use of a natural rutile titania raw material is favorable from the aspects of economy and supply stability. According to the grain size, a rutile titania raw material is called, for example, rutile sand if the grain size is, for example, 1 mm or less, of which rutile sand with a grain size of 0.1 mm or less is called rutile flour. Rutile flour is highly reactive due to the ultra-fine grains, and when used as a titania raw material, rutile flour (TiO2) efficiently produces TiC and TiN. From this aspect, rutile flour with a small grain size is favorable, an average grain size of 30 µm or less being favorable.
[0011] The term average grain size refers to the volume average
particle diameter, which is equivalent to the median cumulative value (D50) of the cumulative curve measured with a laser diffraction-scattering particle size analyzer.
The grain size of the raw material particles being less than
d means that the raw material particles are of such a size as to pass
through a sieve with a mesh size of d stipulated in JIS Z 8801, and
the grain size of the raw material particles being at least d means
that the particles are of such a size as to not pass through the sieve.
[0012] The grain size of the carbon raw material is restricted
to less than 10 µm in order to suppress excessive sintering as described above, and in order to enhance the reactivity with the titania raw material (TiO2) so as to efficiently produce TiC.
If the content of the carbon raw material with a grain size less than 10 µm is less than 3% by mass, excessive sintering cannot

be suppressed and not enough TiC is produced to obtain the function
of protecting the refractory at the taphole lower portion. In
contrast, if the content of the carbon raw material with a grain size
less than 10 µm exceeds 15% by mass, the amount of the binder needed
for suitable kneading increases, and a compact mud material cannot
be obtained. The content of the carbon raw material with a grain
size less than 10 µm is favorably 7% to 13% by mass inclusive.
[0013] As a carbon raw material with a grain size less than 10
µm, carbon black may typically be used. Coke (e.g., that with a grain
size less than 1 mm) can also be used as the carbon raw material in
the mud material according to the present invention, but because coke
is porous, the amount of the binder needed for suitable kneading
increases when a large amount of coke is used, and a compact mud
material cannot be obtained. Accordingly, the amount (content) of
coke used is favorably less than 15% by mass and is more favorably
less than 5% by mass in 100% by mass of the refractory raw material.
[0014] The mud material according to the present invention
favorably contains 3% to 50% by mass inclusive of a silicon nitride raw material with a grain size less than 0.3 mm in 100% by mass of the refractory raw material. With such content, the N in the silicon nitride raw material and the Ti in the titania raw material react to produce TiN. The TiN provides a function for further protecting the refractory of the taphole lower portion.
As the silicon nitride raw material, one or more selected from, for example, silicon mononitride (SiN) and ferrosilicon nitride

(Si3N4Fe) may be used. Between these, ferrosilicon nitride is preferable. That is because the Fe component in the ferrosilicon nitride promotes a reaction that produces SiC bonds. However, if there is too much of the Fe component content in the ferrosilicon nitride, the effect of the reaction promotion may become excessive, resulting instead in a reduction in the amount of SiC produced. Therefore, the ferrosilicon nitride favorably has at least 70% by mass of Si3N4 and the remainder is primarily Fe.
[0015] The mud material according to the present invention may
contain, besides the titania raw material, the carbon raw material and the silicon nitride raw material, other refractory raw materials such as an aluminum oxide raw material, an aluminum silicate raw material (pyrophyllite), a silicon carbide raw material, clay, and metal powder as in a general mud material.
[0016] The mud material according to the present invention is
obtained by kneading a refractory raw material such as described above with a binder. Examples of the binder include a tar and a resin. Examples of the tar include a coal tar, a petroleum tar, a wood tar, a shale tar, an asphalt and a pitch. Examples of the resin include novolac and resole phenolic resins and a furan resin. If a resin, especially a thermoplastic novolac phenolic resin, is used, it is preferable to also use a curing agent such as hexamethylenetetramine. A tar and a resin may also be used in combination.
The amount of binder added is, for example, favorably 10% to 20% by mass inclusive as an outer percentage to 100% by mass of the

refractory raw material, and more favorably 12% to 17% by mass inclusive.
[0017] Table 1 lists mixtures and evaluation results of mud
materials according to examples according to the present invention
and comparative examples. In Table 1, the "titanium raw material
(less than 0.3 mm)" is rutile flour, the "carbon raw material (less
than 10 µm)" is carbon black, and the "silicon nitride raw material
(less than 0.3 mm)" is ferrosilicon nitride. "Other" is an aluminum
oxide raw material, an aluminum silicate raw material (pyrophyllite),
a silicon carbide raw material, a clay and a coke. The content of
the coke in 100% by mass of the refractory raw material is less than
5% by mass in each example. The grain size of the coke is less than
1 mm, but almost none is less than 10 µm, and since there is no effect
on the content of the "carbon raw material (less than 10 µm)", the
content of the "carbon raw material (less than 10 µm)" in Table 1
indicates the content of the carbon black. The "binder" in Table
1 is a tar, the added amount of which is indicated with the outer
mass percentage to 100% by mass of the refractory raw material.
[0018] For each example, the function for protecting the
refractory at the taphole lower portion (hereinafter referred to as the "protection functionality"), the hole opening property and the bending strength were evaluated, and an overall evaluation was made on the basis of the evaluation results. The mud materials of examples 1 and 2 and comparative example 1 were used in an actual machine test.

The evaluation methods for the evaluation items are as follows. [0019] Protection Functionality>
The amount of produced TiC and TiN (the sum total) contributing to the protection functionality was measured using the peak intensity of X-ray diffraction, the peak intensity of comparative example 3 being used as an index of 100. The larger the index value, the more TiC and TiN that were produced and the better the protection functionality. [0020]
After pressure-molding the mud material with a pressure of 7 MPa to 50 mm in diameter and 50 mm in height, the result was placed in a sheath, coke flour was packed between the molded body and the sheath, and reduction heating was carried out at 1200°C. After the mud material test sample was thus heat-treated, the center was cut through vertically with a drill 10 mm in diameter using a drilling type surface strength tester, the cutting rate (mm/min) was measured and the hole opening property was evaluated. The faster the cutting rate, the better the hole opening property was evaluated. [0021]
The mud material was molded into a form 40 mm × 40 mm × 160 mm with a pressure of approximately 7 MPa, the result was sintered for three hours at 1200°C, and then the bending strength was measured at room temperature in accordance with JIS R 2575. In general, the higher the bending strength of the mud material, the better the

effect of preventing molten iron leakage and the like when the taphole is blocked.
[0022]
Evaluations were made on the three levels of ® (superior), o
(good), and x (poor) according to the following standards: ® (superior): A protection functionality (index) of at least 100, a hole opening property (mm/min) of at least 90, and a bending strength (MPa) of at least 4.
O (good): A protection functionality (index) of at least 100, a hole opening property (mm/min) of at least 70 and less than 90, and a
bending strength (MPa) of at least 3 and less than 4.
x (poor): A protection functionality (index) of less than 100, a hole opening property (mm/min) of less than 70, or a bending strength
(MPa) of less than 3.

[0024] As listed in Table 1, examples 1 to 9 within the scope according to the present invention each had an overall evaluation of ® (excellent) or o (good). Among these examples, examples 1, 6 and 7 each had carbon raw material (less than 10 µm) and titania raw material (less than 0.3 mm) content within the abovementioned favorable scope and a silicon nitride raw material (less than 0.3 mm) of 3% to 50% by mass inclusive, and was particularly favorable with an overall evaluation of ® (excellent).
[0025] Comparative example 1 had little titania raw material (less than 0.3 mm) content, and with little TiC and TiN produced, was evaluated as not obtaining adequate protection functionality. Comparative example 2 had a lot of titania raw material (less than 0.3 mm) content, and with excessive sintering occurring due to the titania raw material, the hole opening property was greatly reduced.
[0026] Comparative example 3 had little carbon raw material (less than 10 µm) content, excessive sintering was not suppressed, and the hole opening property was greatly reduced. Additionally, the amount of binder needed for suitable kneading increased, so that a compact could not be obtained and the bending strength dropped. Comparative example 4 had a lot of carbon raw material (less than 10 µm) content, the amount of the binder needed for suitable kneading increased, a compact mud material was not obtained, and the bending strength dropped.

[0027] In the results of the actual machine test, there was little titania raw material (less than 0.3 mm) content and the
furnace bottom temperature rose to 426°C in comparative example 1, but in examples 1 and 2 of the present invention, the furnace bottom temperature was curbed to no more than 300°C.

WE CLAIM
1. A mud material for filling a taphole of a blast furnace
containing a refractory raw material and a binder, the mud material comprising:
3% to 20% by mass inclusive of a titania raw material with a grain size less than 0. 3 mm and 3% to 15% by mass inclusive of a carbon raw material with a grain size less than 10 urn in 100% by mass of the refractory raw material.
2. The mud material according to claim 1, further comprising 3% to 50% by mass inclusive of a silicon nitride raw material with a grain size less than 0.3 mm in 100% by mass of the refractory raw material.
3. The mud material according to claim 1 or 2, wherein the titania raw material is rutile flour.