Technical field

[0001]

　The present invention relates to a magnesia carbon brick and its manufacturing method is used, such as molten metal container or refining furnace.

BACKGROUND

[0002]

　Magnesia carbon brick will generally contain scaly graphite as a carbon source, but the problem and the heat loss due to dissipation heat of the high molten metal thermal conductivity for containing flake graphite, there is a carbon pickup problems. Further, when used in an oxidizing atmosphere, such as a converter and secondary refining facility, by dissolution of the slag component is infiltrated aggregate is accelerated pores formed due to the loss of graphite due to oxidation, corrosion resistance insufficient to become a problem also.

[0003]

　From these viewpoints, it is desirable that the magnesia carbon brick containing no flake graphite and containing no flake graphite, a problem that spalling resistance is lowered.

[0004]

　Therefore, it means for suppressing the lowering of the spalling resistance due to that it does not contain the flake graphite have been proposed. For example, Patent Document 1, as an alternative carbon source vein graphite, organic binder, pitch, and method of using carbon black alone or in combination is proposed, by this approach, while have a dense texture under the high temperature does not proceed excessively sintered even if it has been used for a long time (suppress high elastic modulus), there is a good spalling resistance can be maintained. Then, in Example 9, a phenol resin as a binder, 1 wt% pitch, magnesia alumina refractory brick is disclosed containing no flake graphite carbon black was added 1% by weight. However, according to our studies, there is a problem that cracks and breakage due to spalling occurs when used at such even RH degassing furnace by applying this technique of Patent Document 1 simply magnesia carbon bricks I understood it.

[0005]

　Further, Patent Document 2, the particle size 10μm ultra 500μm or smaller particles of magnesia-based in the raw material accounts for 20 to 50% by weight of the refractory raw material formulation, and fine portions of the magnesia in the raw material, particularly 10μm or less part, who or less is not used is described as preferable from the viewpoint of spalling resistance.

[0006]

　Furthermore, Patent Document 3, the refractory raw material formulation, the mass ratio of the particle diameter 1mm or magnesia particles amount 1.27 or more 2.58 or less with respect to the magnesia particles of size less than 1mm, and magnesia and graphite magnesia carbon bricks are disclosed amount of graphite in the total amount is 10 mass% or less. And Patent Document 3 have been described that below. That is, "the magnesia carbon bricks, because compared to typical magnesia carbon brick containing many coarse particles, is excellent spalling resistance despite a small amount of graphite blended. However, the amount of graphite blended is, for example, 6 If mass% less, such as less may spalling resistance is insufficient depending on the operational conditions. in such a case, blending the pitch or carbon black having a softening point of 70 ° C. or higher 370 ° C. or less it is preferable to. these materials have the effect of improving spalling resistance of the magnesia carbon bricks. is not particularly limited as to its amount, in total amount of these raw materials, the refractory raw material formulation in outer percentage to the total amount of magnesia and graphite is preferably not more than 4 mass% to 0.5 mass%. "

[0007]

　These Patent Documents 2 and 3, although both examples containing graphite refractory raw material formulation, the graphite by refractory raw material formulation present inventors have simply excluding the graphite from these refractory raw material formulation It was prepared the unburned magnesia brick containing no, spalling resistance and corrosion resistance was insufficient.

CITATION

Patent Document

[0008]

Patent Document 1: JP-A-11-322405 Patent Publication
Patent Document 2: JP 2007-182337 Patent Publication
Patent Document 3: JP 2013-72090 JP

Summary of the Invention

Problems that the Invention is to Solve

[0009]

　An object of the present invention is to provide not contain graphite, yet which is excellent magnesia carbon bricks and a manufacturing method thereof spalling resistance and corrosion resistance.

Means for Solving the Problems

[0010]

　The present inventors have in refractory raw material formulation of magnesia carbon brick containing no graphite, pitch and / or carbon black, as well as used in a specific range of aluminum and / or aluminum alloy, moreover, particle size less than 0.075mm than 1mm by the mass ratio of magnesia having a particle size of less than 1mm 5mm or more relative to magnesia and 1.66 or 2.34 or less was found that satisfies the densification and low elastic modulus after the heat treatment at the same time. The present inventors have found that the magnesia carbon bricks can be obtained having excellent spalling resistance and corrosion resistance in actual furnace used.

[0011]

　That is, according to the present invention, a method of manufacturing magnesia carbon bricks from the following (1) magnesia carbon bricks and (7) (8) is provided.
　(1) after the addition of the organic binder in the refractory raw material formulation by kneading molding, a magnesia carbon brick obtained by heat-treating,
　refractory raw material formulation, the pitch and / or carbon black in total 0.1 more mass% 2.0 mass% or less, aluminum and / or aluminum alloy in a total amount of 0.1 mass% to 1.0 mass%, particle size of the magnesia is less than 0.075 mm 3.0 mass% or more 10 .0 wt% or less, and a particle size contained 5mm less magnesia than 0.075mm 87.0 mass% or more 96.0% by mass or less, and the particle size particle size for magnesia less 1mm than 0.075mm the mass ratio of 5mm less magnesia than 1mm is at 1.66 or more 2.34 or less, containing no graphite, apparent porosity after heat treatment for 3 hours under 1400 ° C. reducing atmosphere 8. % Or less magnesia carbon brick is.
　(2) In the refractory raw material formulation, magnesia carbon brick according to the combination of pitch and carbon black (1).
　(3) In the refractory raw material formulation, magnesia carbon brick according to the pitch and / or carbon black is not more than 1.4 mass% to 0.2 mass% in total (1) or (2).
　(4) refractory in the raw material formulation, aluminum and / or aluminum alloy is not more than 0.7 mass% to 0.1 mass% in total (1) to (3) magnesia carbon according to any one of brick.
　(5) In the refractory raw material formulation, the mass ratio of the particle diameter is less than 5mm particle size 1mm or more with respect to 1mm less magnesia than 0.075mm magnesia is 1.85 or more 2.20 or less (1) to (4 magnesia carbon brick according to any one of).
　(6) In the refractory raw material formulation, according to any one of silicon was used aluminum and / or in a total amount of aluminum alloy 0.2 wt% to 1.0 wt% or less (1) to (5) of magnesia carbon bricks.
　(7) the pitch and / or carbon black in a total amount of 0.1 mass% to 2.0 mass%, aluminum and / or aluminum alloy in a total amount of 0.1 mass% to 1.0 mass%, grain diameter less than 10 wt% 3 wt% or more less than the magnesia 0.075 mm, and a particle size contained 5mm less magnesia than 0.075 mm 87.0 wt% or more 96.0% by mass or less, and the particle size particle size for 1mm less magnesia than 0.075mm is at a weight ratio of magnesia of less than 5mm than 1mm is 1.66 or more 2.34 or less, the refractory raw material formulation containing no graphite, by adding an organic binder kneaded after molding, a heat treatment method for producing a magnesia carbon brick.

[0012]

　Note that the particle size referred to in the present invention refers to a sieve size when separated sieved with a sieve of refractory raw material particles, for example, magnesia having a particle size of less than 0.075 mm, the sieve 0 by magnesia to pass through a sieve of .075Mm, the particle size 0.075mm or magnesia, sieve is that of magnesia which does not pass through the sieve of 0.075mm.

[0013]

　The following describes the structure of features refractory raw material formulation is the invention.

[0014]

　Pitch and / or carbon black, 2.0 wt% or less than 0.1 wt% to the brick and low elastic modulus to improve the spalling resistance, preferably from 0.2 wt% to 1.4 wt% used in the following. Pitch and / or carbon black becomes insufficient spalling resistance improvement is less than 0.1 wt%, more than 2.0% by mass, the porosity is for corrosion resistance decreases high.

[0015]

　Incidentally, spalling resistance and corrosion resistance of the brick in the present invention was evaluated by measurement of the apparent porosity and the acoustic velocity elastic modulus after heat treatment for 3 hours under 1400 ° C. reducing atmosphere. Apparent porosity and the acoustic velocity modulus of bricks described below is a measurement of the following heat treatment for 3 hours both under a 1400 ° C. reducing atmosphere. Further, apparent porosity simply porosity, acoustic velocity modulus referred simply to as a modulus.

[0016]

　1.0 mass% 0.1 mass% or more for the aluminum and / or densification of aluminum alloy structure and antioxidant in refractory raw material formulation of the present invention hereinafter, 0.7 mass preferably at least 0.1 wt% % used in the following. When aluminum and / or aluminum alloy is more than 1.0 mass%, the expansion further by the reaction of aluminum when using aluminum and / or aluminum alloy melt, high becomes corrosion resistance porosity for pores caused by volatile non enough to become. Becomes insufficient densification effect of tissue in aluminum and / or aluminum alloy is less than 0.1 wt%, corrosion resistance decreases porosity is increased. The densification effect of tissue is more prominently expressed by applying, for example, fine aluminum with a particle size less than 0.075mm and / or an aluminum alloy.

[0017]

　Refractory raw material formulation of the present invention do not contain graphite, in particular compounding carbon source powder is small, filling property at the time of molding for sliding ineffective the raw material particles at the time of molding by graphite is deteriorated. Therefore, magnesia having a particle size of less than 0.075mm further filling property at the time of molding is significantly affects the sintering properties in use, it controls the amount is very important. That is, in the refractory raw material formulation, the magnesia is less than 3.0% by weight having a particle size of less than 0.075mm increased porosity for voids in the tissue of brick is sufficiently filled. The porosity is increased by lowering the filling property after molding and magnesia having a particle size of less than 0.075mm exceeds 10.0 mass%, yet high sinterability for will contain much fine powder, the elastic modulus increases. Further, less than the particle size 0.075 mm 5 mm magnesia is used in 96.0% by mass or less 87.0 mass% or more in order to have sufficient corrosion resistance.

[0018]

　The weight ratio of magnesia having a particle size of less than 1mm 5mm or more relative to magnesia having a particle size of less than 0.075mm than 1mm of refractory raw material formulation (magnesia having a particle size of less than 1mm 5mm or more mass / particle size 1mm less magnesia than 0.075mm mass) is by 1.66 or more 2.34 or less, it becomes low porosity and low modulus, a low porosity and low elasticity than by further 1.85 or more 2.20 or less . This mass ratio is too high porosity and modulus is less than 1.66, more than 2.34 when the porosity is too high. Although higher modulus when tissue is densified in general, the present inventors have found that in a mass ratio of the in the range of 1.66 or more 2.34 or less and densification and low elastic modulus of the tissue it was the knowledge that can be satisfied at the same time.

[0019]

　As described above, magnesia carbon brick of the present invention is apparent porosity after heat treatment for 3 hours under 1400 ° C. reducing atmosphere to tissue becomes dense it is 8.0% or less. For this reason the magnesia carbon bricks excellent remarkably in corrosion resistance.

[0020]

　The refractory raw material formulation of the present invention can be added to silicon (metal Si) aiming densification effect of further tissue. The amount added of aluminum and / or in a total amount of aluminum alloy 0.2 wt% to 1.0 wt% or less, the silicon alone is sufficient below 0.5 wt%. Densifying effect of the tissue by applying a fine silicon of size less than 0.045mm is more prominently expressed. No more excessive addition increases the generation amount of TeiTorubutsu in magnesia carbon brick, reduces the useful cause corrosion decrease.

Effect of the invention

[0021]

　Magnesia carbon brick of the present invention do not contain graphite, yet is excellent in spalling resistance and corrosion resistance, it can be used without problems in a converter furnace and secondary refining facilities. As a result, it is possible to suppress the heat loss and carbon pickup, it is possible to improve the durability of the furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]

[Figure 1] shows the relationship between the apparent porosity after heat treatment for 3 hours at corrosion resistance and under 1400 ° C. reducing atmosphere magnesia carbon brick.

DESCRIPTION OF THE INVENTION

[0023]

　Magnesia for use in refractory raw material formulation in the present invention may be either fused magnesia and sintered magnesia, these may be used in combination. Its is not particularly limited composition, in order to obtain a higher corrosion resistance can be used a high magnesia MgO purity, such as MgO purity of 96% or more, and more may be 98% or more.

[0024]

　Pitch and carbon black is used to improve the spalling resistance, it can be used without problems as long as it is generally used, such as magnesia carbon brick. The pitch can be also be used as a liquid dissolved in a solvent in the powder.

[0025]

　Aluminum, aluminum alloys and silicon, intended for use in order to densify the improved so Moreover tissue oxidation resistance, can be used without problems as long as it is generally used, such as magnesia carbon brick.

[0026]

　Magnesia, used without adversely pitch and / or carbon black, aluminum and / or aluminum alloy, and in addition to silicon, the adverse effect if the raw material to 5 mass% or less, which is generally used as a raw material for magnesia carbon bricks can do. Specifically, aluminum, metals other than aluminum alloys and silicon, fiber, and glass.

[0027]

　Magnesia carbon brick of the present invention can be manufactured by the manufacturing method of the common magnesia carbon bricks. That is, magnesia carbon brick of the present invention, after molding and kneaded with addition of organic binder to refractory raw material formulation described above can be obtained by heat treatment.

[0028]

　The organic binder, the organic binder used in the conventional magnesia carbon bricks can be used, for example, a furan resin or a phenol resin can be used. Further, the organic binder, liquid dissolved in a powder or a suitable solvent, any further liquid and powder combination can also be used in the form. Kneading, methods and conditions for molding and heat treatment is also according to the method of manufacturing the common magnesia carbon bricks. For example, the heat treatment temperature may be 150 ~ 400 ℃.

[0029]

　Magnesia carbon brick of the present invention thus obtained has a converter, an electric furnace, ladle, can be used as a lining material for molten metal treatment furnace such as a vacuum degassing furnace, in particular carbon pickup is a problem It is suitable for use in a vacuum degassing furnace, such as RH made.
Example

[0030]

　A phenolic resin as an organic binder to a refractory raw material formulation shown in Table 1 by adding an appropriate amount and kneaded, after molding into a shape of 230 mm × 114 mm × 100 mm by an oil press, a heat treatment for 5 hours maintained at a maximum temperature of 250 ° C. (drying treatment) It was applied. With measuring the apparent porosity and the acoustic velocity modulus now cut out a sample for measuring physical properties were evaluated corrosion resistance.

[0031]

[Table 1]

[0032]

　In the measurement of the apparent porosity fills sample shape 50 × 50 × 50 mm in coke breeze, heated up to 1400 ° C. in an electric furnace, then cooled naturally and held for 3 hours. Thereafter, the solvent was measured according to JIS R 2205 and kerosene. The higher the porosity is low, brick is dense, it is determined that effective corrosion resistance improvement.

[0033]

　In the measurement of the sound velocity modulus fills sample shape 20 × 20 × 80 mm in coke breeze as with the measurement of the apparent porosity, the temperature was raised to 1400 ° C. in an electric furnace, then cooled naturally to 3 hours . Thereafter, determined by measuring the molded during unpressurized direction of the sound velocity of the sample, was judged to be good spalling resistance modulus below 72 GPa.

[0034]

　The corrosion resistance was evaluated by the rotation erosion test. The rotary corrosion test, lined inner surface of the drum having a horizontal axis of rotation in test bricks, slag poured, heated and allowed to erode the brick surface. Heat source of oxygen - a propane burner, test temperature 1700 ° C., the slag composition CaO: 30 wt%, SiO 2 : 30 wt%, Al 2 O 3 : 20 wt%, FeO + Fe 2 O 3 : a 20 mass%, discharge of slag, was repeated 10 times put on every 30 minutes. After the test, the dimensions of the maximum erosion of the brick (Zansun brick) were measured and displayed in the corrosion resistance index is 100 to Zansun brick "Comparative Example 1" described in Table 1. The corrosion resistance index shows the superiority of the corrosion resistance as those numerical increases.

[0035]

　Example 3 Example 1, which has a content of magnesia having a particle size of less than 0.075mm of refractory raw material formulation varied in the range of the present invention, any apparent porosity is low, corrosion resistance is low good modulus of elasticity.

[0036]

　In contrast, Comparative Example 1 is magnesia having a particle size of less than 0.075mm is below 1.0 wt% and the lower limit value, apparent porosity since voids becomes insufficient filling is increased, the corrosion resistance is lowered. Comparative Example 2 is lower than the magnesia to less than the particle size 0.075 mm 5 mm 85.0% by weight and the lower limit value, the filling property after molding is decreased apparent porosity is lowered corrosion resistance increased. Comparative Example 3 is lower than 83.5 mass% and the lower limit value of 5mm less magnesia or particle size 0.075mm with magnesia having a particle size of less than 0.075mm exceeds the upper limit value at 15.0 wt%, after formation corrosion resistance is lowered by filling property is lowered apparent porosity of rise. Moreover, sinterability is high since it contains many fines of less than a particle size 0.075 mm, the elastic modulus becomes high.

[0037]

　Example 4 Example 8 is for the weight ratio of magnesia having a particle size of less than 1mm 5mm or more relative to magnesia less than the particle size 0.075 mm 1mm was varied within the scope of the present invention, any apparent porosity rate the corrosion resistance was good low modulus are properly kept low. Further Example 8 from Example 4 because of the addition of silicon, the porosity was further reduced. That is, the mass ratio of the to compare Examples 2 and 6 of the same degree, towards the Example 6 with the addition of silicon, with improved corrosion resistance and reduced apparent porosity. In Examples 4 and 8, the weight ratio of said have deviated from the preferred range as 1.66,2.34 (1.85 or 2.20 or less), the porosity as compared with Examples 5-7 It rose slightly.

[0038]

　In contrast, Comparative Example 4 is the mass ratio of the decreases corrosion resistance higher 1.30 and porosity is below the lower limit, the elastic modulus was considerably increased. Comparative Example 5 weight ratio of 2.61 and an upper limit value above and has porosity of the can is considerably increased corrosion resistance was reduced.

[0039]

　Example 9 Example 12 is for changing the amount of pitch and / or carbon black within the scope of the present invention, corrosion resistance low apparent porosity was good, which is lower elastic modulus . In Examples 10 1% by weight of carbon black only, than Example 11 but is obtained by adding only pitch 1 wt%, with the carbon black and the pitch of Example 6 was added each 0.5 wt% also, which is higher slightly porosity is high modulus of elasticity. However Example 10 Example By 11, the silicon is added 0.2 wt%, to suppress the increase of the porosity.

[0040]

　In contrast, Comparative Example 6 are those with no added carbon black and pitch, the elastic modulus was considerably increased. Comparative Example 7 has exceeded the upper limit of the total amount of the added amount of carbon black and a pitch of 2.3 wt% and the present invention, the corrosion resistance porosity increases sharply decreased.

[0041]

　Example 16 Example 13 is for the amount of aluminum added was varied within the scope of the present invention, also improves the corrosion resistance low apparent porosity, which is lower elastic modulus. Note that implementation was added 0.7 wt% of aluminum and silicon in a total amount Example 6, has improved corrosion resistance in low porosity than Example 15 with the addition of aluminum only 0.7 wt%. In Examples 16 deviates from the preferred range amount of aluminum and 1.0 wt% (0.1 wt% to 0.7 wt% or less), porosity as compared with Examples 13-15 It was slightly elevated.

[0042]

　In contrast, Comparative Example 8 without addition of aluminum tissue was reduced high becomes corrosion resistance apparent porosity because it is not densified. Comparative Example 9 in which the addition amount of aluminum exceeds the upper limit of 1.2 wt% and the present invention is the corrosion resistance is lowered becomes high porosity, also increased elastic modulus.

[0043]

　Example 17 is obtained by addition of boron carbide and silicon as 0.2% by weight and the antioxidant 0.2 wt%, Example 18, silicon 0.2 wt% and Al-Mg alloy (Al-containing the amount 50% by weight) and boron carbide as an antioxidant was prepared by adding respectively 0.5 wt%, as compared with example 5, the reduction of further porosity, improvement in corrosion resistance was achieved.

[0044]

　Comparative Example 10 and Comparative Example 11, 1.0 wt% of flake graphite, respectively, but contains 3.0 wt%, the porosity was reduced even higher corrosion resistance than any of the examples.

[0045]

　Example and lined with 6 bricks and bricks of Comparative Example 4 in the lower bin wall of RH 350 times (ch) used, and observed to recover brick after use. Brick of Example 6 are used successfully without cracking, erosion rate was 1.1 mm / ch. Brick of Comparative Example 4, cracks peeling occurs, erosion rate was 2.3 mm / ch.

[0046]

　It shows the relationship between the 3-hour apparent porosity after heat treatment in Examples and corrosion resistance and under 1400 ° C. reducing atmosphere magnesia carbon bricks of the comparative example shown in Table 1 in FIG. 1. Magnesia carbon bricks examples it can be seen that a good corrosion resistance becomes apparent porosity of 8.0% or less. Comparative Example In contrast it is seen that the corrosion resistance for apparent porosity except Comparative Example 6 is greater than 8.0% is substantially reduced. Incidentally, there is no practical level spalling resistance for Comparative Example 6 not using carbon black and / or pitch.

The scope of the claims

[Requested item 1]

　After the addition of organic binder to refractory raw material formulation by kneading molding, a magnesia carbon brick obtained by heat-treating,
　refractory raw material formulation, 0.1 wt% of pitch and / or carbon black in a total amount 2.0 wt% or less, aluminum and / or aluminum alloy in a total amount of 0.1 mass% to 1.0 mass%, particle size of the magnesia is less than 0.075 mm 3.0% by mass or more and 10.0 mass % or less, and a particle size contained 5mm less magnesia than 0.075 mm 87.0 wt% or more 96.0% by mass or less, and a particle size of 1mm or more with respect to magnesia having a particle size of less than or more 0.075 mm 1mm 5mm less than the mass ratio of the magnesia is at 1.66 or more 2.34 or less, containing no graphite, apparent porosity after heat treatment for 3 hours under 1400 ° C. reducing atmosphere of 8.0% or Magnesia carbon brick is.

[Requested item 2]

　In the refractory raw material formulation, magnesia carbon brick according to claim 1 in combination with pitch and carbon black.

[Requested item 3]

　In the refractory raw material formulation, the pitch and / or magnesia carbon brick according to claim 1 or 2 carbon black is not more than 1.4 mass% to 0.2 mass% in total.

[Requested item 4]

　In the refractory raw material formulation, aluminum and / or magnesia carbon brick according to any one of claims 1 to 3 the aluminum alloy is not more than 0.7 mass% to 0.1 mass% in total.

[Requested item 5]

　In the refractory raw material formulation, either the particle size is less than 1mm or more 0.075mm particle size for magnesia is less than 5mm above 1mm weight ratio of magnesia of claims 1 to 4 is 1.85 or more 2.20 or less 1 magnesia carbon bricks according to the item.

[Requested item 6]

　In the refractory raw material formulation, silicon aluminum and / or aluminum alloy and magnesia carbon brick according to any one of claims 1 to 5 has been used more than 0.2 mass% 1.0 mass% or less in total of.

[Requested item 7]

　0.1 wt% of pitch and / or carbon black in a total of 2.0 wt% or less, aluminum and / or aluminum alloy in a total amount of 0.1 mass% to 1.0 mass%, particle size 0 magnesia of less than .075Mm 3 wt% to 10 wt% or less, and a particle size contained 5mm less magnesia than 0.075mm 87.0 mass% or more 96.0% by mass or less, and the particle diameter 0.075mm or the mass ratio of the particle diameter is less than 5mm above 1mm magnesia less than 1mm in respect magnesia is at 1.66 or more 2.34 or less, the refractory raw material formulation containing no graphite, kneaded after molding by adding an organic binder , heat treatment, the production method of magnesia carbon bricks.