Ladle mgo-c refractory and manufacturing method therefor

Abstract

The present invention relates to a ladle MgO-C refractory applied to a reduction process of iron oxide, and a manufacturing method therefor, the MgO-C refractory having an inorganic binder precursor infiltrated into the interface of MgO-C particles in order to prevent thermal and mechanical property deterioration of the refractory due to MgO-C degradation caused by carbon oxidation, thereby maintaining high strength and having low thermal expansion during actual operation.

Description

MGO-C refractory for ladle and its manufacturing method

[0001] The present invention relates to a method for improving the strength and thermal expansion coefficient of MgO-C refractories applied to a reduction process of iron oxide, and to a composition of MgO-C refractories having high strength and thermal shock resistance even at high temperatures and a method for manufacturing the same by applying an inorganic binder precursor to generate an inorganic binder at the interface of MgO-C particles in order to control the deterioration of the properties of the refractories due to deterioration of MgO-C during the iron-making process.

[0002]

[0003] In the steel industry, MgO-C bricks are widely used as refractory materials with excellent thermal, chemical, and mechanical properties for ladles. These properties are due to the unique properties of MgO and C as well as their complementary combination. MgO has a high melting point (T m= 2852℃) shows high heat resistance, but its high thermal expansion coefficient reduces thermal shock resistance, which causes exfoliation damage. Therefore, the addition of graphite compensates for the shortcomings of MgO by providing low thermal expansion and high thermal conductivity, thereby improving thermal shock resistance. In addition, graphite has low wettability, so it shows excellent chemical stability against slag. Therefore, many attempts have been made to maximize the benefits of graphite addition, such as varying the form of graphite or controlling the amount. However, the graphite in MgO-C refractories is very vulnerable to oxidation, so damage by erosion or corrosion is serious, and structural destruction of the refractory easily occurs in actual application due to slag penetration and pore formation. Therefore, to prevent this oxidation phenomenon, it is common to add an antioxidant that is highly reactive with oxygen to MgO-C refractories. The added antioxidants include metals / alloys such as Al, Al / Mg alloys, carbides such as B4C and SiC, and borides such as CaB6 and ZrB2, which have stronger oxidizing properties than graphite. Theoretically, this means that graphite does not react with oxygen until the antioxidant is significantly oxidized. However, in actual operation, graphite reacts with oxygen even when the antioxidant has not significantly oxidized. This is an unavoidable phenomenon because the pores within the MgO-C refractory do not allow the antioxidant to effectively inhibit graphite oxidation in real-world conditions. Therefore, methods to improve graphite oxidation have been studied. Graphite resistance was improved by coating the graphite surface with a metal precursor, specifically an aluminum precursor. Al-coated graphite exhibits higher oxidation resistance due to the barrier effect of the aluminum layer formed on the graphite surface. Therefore, during the coating process, the coating agent must be uniformly coated on the graphite surface to achieve a sufficient coating effect. However, prolonged exposure to high temperatures has been problematic because graphite oxidation is not effectively inhibited, significantly degrading the mechanical properties of the refractory.Therefore, the present invention is not intended to suppress oxidation of graphite by using an antioxidant or modifying the surface of graphite, but rather to introduce a substance that compensates for oxidation of graphite even if it occurs, thereby overcoming the deterioration of the properties of MgO-C refractory due to oxidation of graphite.

[0004]

[0005] The purpose of the present invention is to apply an inorganic binder to prevent erosion of the refractory caused by oxidation of graphite present in MgO-C refractories used in a ladle and structural destruction of the refractory caused by slag penetration and pore creation, thereby improving the deterioration of the properties of the refractory caused by oxidation of graphite.

[0006] The purpose of the present invention is to establish the type and composition of an inorganic binder and to provide a method for manufacturing an MgO-C refractory using the same.

[0007] The applied inorganic binder is used in a liquid form to effectively penetrate between the particles of the refractory, and improves the mechanical properties of the refractory by generating an inorganic reactant at the interface of the refractory particles due to a sol-gel reaction, which inhibits the penetration of molten metal and slag into the refractory, thereby reducing the destruction of the refractory.

[0008]

[0009] In order to achieve the above-mentioned purpose, the present invention can provide a method for manufacturing a MgO-C refractory for a ladle having high strength and high thermal shock resistance by performing the following process.

[0010]

[0011] The method for manufacturing an MgO-C refractory of the present invention may include the steps of: mixing MgO powder, graphite, and an antioxidant to prepare a mixture; mixing an organic curing agent into the mixture and kneading it; aging the kneaded mixture; molding the aged mixture to prepare a molded article; curing the manufactured molded article; immersing the cured molded article in a liquid inorganic binder precursor; drying the immersed molded article; and heat-treating the dried molded article.

[0012] In one embodiment of the present invention, after the step of manufacturing the molded body, a CIP (Cold Isostatic Pressing) process step may be further included before the step of hardening the manufactured molded body.

[0013] In one embodiment of the present invention, the drying step may be drying the immersed molded body at 80 to 120°C for 20 to 28 hours.

[0014] In one embodiment of the present invention, the heat treatment step may be to heat treat the dried molded body at 1000 to 1600°C for 1 to 3 hours.

[0015] In one embodiment of the present invention, the liquid inorganic binder precursor may be liquid and may be at least one selected from the group consisting of a silica precursor, a sodium precursor, and an aluminum precursor.

[0016] In one embodiment of the present invention, the weight ratio of the silica precursor, sodium precursor, and aluminum precursor may be 1:1:1 to 6:1:1.

[0017] In one embodiment of the present invention, after the drying step, the inorganic product may be converted from a liquid phase to a solid phase by a sol-gel reaction.

[0018]

[0019] In addition, the present invention provides a MgO-C refractory for a ladle manufactured according to the above manufacturing method.

[0020] In one embodiment of the present invention, the MgO-C refractory may include MgO powder, graphite, an antioxidant, and an inorganic binder.

[0021] The above inorganic binder may include at least one selected from the group consisting of silica, sodium silicate, sodium aluminate, mullite, and sodium aluminosilicate.

[0022]

[0023] The manufacturing method of the present invention can manufacture a MgO-C refractory for a ladle having high mechanical strength and low thermal expansion coefficient by allowing an inorganic binder precursor to exist between pores and particles in the refractory.

[0024] According to the present invention, the introduction of the above-mentioned inorganic binder precursor suppresses changes in the thermal expansion coefficient and thermal shock resistance of the refractory due to oxidation of graphite. In other words, erosion of the MgO-C refractory and infiltration of slag can be effectively prevented despite the oxidation reaction of graphite.

[0025] According to the present invention, a liquid inorganic binder precursor is applied to enable effective penetration into the interior of MgO-C refractory.

[0026] According to the present invention, the life of MgO-C refractories is increased by the production of inorganic products having high melting points by conversion of inorganic binder precursors at actual operating temperatures.

[0027] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0028]

[0029] Figure 1 is a schematic diagram of the manufacturing process of MgO-C refractory for a ladle.

[0030] Figure 2 shows the TGA results of a resol-type phenol resin, which is an organic curing agent.

[0031] Figure 3 shows the shape after the drying step of the inorganic binder precursor.

[0032] Figure 4 shows the shape after the heat treatment step of the inorganic binder precursor.

[0033] Figure 5 shows the SEM and EDS results of the MgO-C refractory manufactured by Comparative Example 2.

[0034] Figure 6 shows the SEM and EDS results of the MgO-C refractory manufactured by Example 1.

[0035] Figure 7 shows the SEM and EDS results of the MgO-C refractory manufactured by Example 2.

[0036] Figure 8 shows the SEM and EDS results of the MgO-C refractory manufactured by Example 3.

[0037] Figure 9 shows the SEM and EDS results of the MgO-C refractory manufactured by Example 4.

[0038] Figure 10 shows the XRD results of MgO-C refractories manufactured by Comparative Examples 3 to 6 and Comparative Example 1.

[0039] Figure 11 shows the XRD results of MgO-C refractories manufactured according to Examples 1 to 4 and Comparative Example 2.

[0040] Figure 12 shows the XRD results after drying of the inorganic binder precursor applied to Comparative Examples 3 to 4.

[0041] Figure 13 shows the XRD results after heat treatment at 1400°C of the inorganic binder precursor applied to Comparative Example 3 and Example 4.

[0042] Figure 14 is a graph showing the fracture strength of MgO-C refractories manufactured as comparative examples and examples.

[0043] Figure 15 is a graph showing the thermal expansion coefficient of MgO-C refractories manufactured in Examples 1 to 4 and Comparative Example 2.

[0044]

[0045] The terms used in this specification have been selected from widely used, current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should not be defined simply as names, but rather based on their inherent meanings and the overall content of the present invention.

[0046] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0047] Numerical ranges are inclusive of the numbers defined in the ranges above. Every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if that lower numerical limitation were explicitly stated. Every minimum numerical limitation given throughout this specification includes every higher numerical limitation, as if that higher numerical limitation were explicitly stated. Every numerical limitation given throughout this specification will include every better numerical range within that broader numerical range, as if that narrower numerical limitation were explicitly stated.

[0048]

[0049] Hereinafter, the present invention will be described in detail.

[0050]

[0051] As shown in Fig. 1, the method for manufacturing a MgO-C refractory for a ladle of the present invention may include a step of mixing MgO powder, graphite, and an antioxidant to prepare a mixture; a step of mixing an organic curing agent into the mixture and kneading it; a step of aging the kneaded mixture; a step of molding the aged mixture to prepare a molded article; a step of curing the molded article; a step of immersing the cured molded article in a liquid inorganic binder precursor; a step of drying the immersed molded article; and a step of heat-treating the dried molded article.

[0052] The above MgO powder can be used by mixing one or two or more particles having a size of 0.0075 to 5 mm.

[0053] The above graphite may be added alone or in combination as impression graphite and expanded graphite.

[0054] The above antioxidant may be at least one selected from Al, Si, Cr, Mn, Co, and Mo. Most preferably, the antioxidant may be Al and Si.

[0055] The above organic curing agent may be selected from phenol resin, epoxy resin, melamine resin, urea resin, alkyd resin, silicone resin or mixtures thereof, and hexamethylenetetramine, diethylene triamine (DETA), triethylenetetramine (TETA), etc. may be used to improve curing.

[0056] In one embodiment of the present invention, a resol-type phenolic resin may be used as the organic curing agent. The TGA results of the resol-type phenolic resin are shown in Fig. 2. The resol-type phenolic resin self-cures at approximately 176°C, but may be cured at 250°C for one hour to maximize the curing effect.

[0057] The step of preparing the above mixture may be to prepare the mixture by mixing at 30 to 50 rpm for 20 to 60 minutes.

[0058] The step of preparing the above mixture may be to prepare the mixture by mixing 15 to 25 parts by weight of graphite and 2 to 5 parts by weight of an antioxidant with respect to 100 parts by weight of the MgO. In addition, 3 to 6 parts by weight of an organic curing agent may be added with respect to 100 parts by weight of the mixture prepared above.

[0059] The above mixing step may be mixing at 30 to 50 rpm for 20 to 60 minutes at 15 to 25°C.

[0060] The above aging step is a step to maximize the curing of the organic curing agent and can be performed at a temperature of 15 to 25°C for 20 to 28 hours. At this time, the aging time cannot be limited as it varies depending on the amount of raw material powder.

[0061] The step of manufacturing the above molded body can manufacture the molded body by uniaxially or biaxially pressing the aged mixture.

[0062] After the step of manufacturing the molded body, a CIP (Cold Isostatic Pressing) process step may be further included before the step of hardening the manufactured molded body.

[0063] The above-mentioned curing step may be to cure the manufactured molded body at a temperature of 80 to 300°C for 1 to 4 hours. At this time, the curing temperature varies depending on the type of curing agent and must be lower than the decomposition temperature of the curing agent.

[0064]

[0065] Next, in the immersing step, the liquid inorganic binder precursor may be at least one selected from the group consisting of a silica precursor, a sodium precursor, and an aluminum precursor.

[0066] The silica precursor may include one or more compounds selected from the group consisting of silicate precursors, siloxane precursors, and silane precursors. In one embodiment of the present invention, the silica precursor may be TEOS (tetraethyl orthosilicate).

[0067] The above sodium precursor may be a sodium alkoxide. In one embodiment of the present invention, the sodium precursor may be NaOMe (sodium methoxide).

[0068] The above aluminum precursor may include one or more compounds selected from the group consisting of aluminum alkoxides, aluminum hydroxide compounds, and aluminum salt compounds. In one embodiment of the present invention, the aluminum precursor may be AlOEt (aluminum ethoxide).

[0069]

[0070] In one embodiment of the present invention, the inorganic binder precursor may include TEOS, NaOMe, and AlOEt. In addition, the ratio of TEOS, NaOMe, and AlOEt may be 1:1:1 to 6:1:1.

[0071] The shape of the above inorganic binder precursor can be converted into an amorphous glassy phase or a crystalline phase (powder) after the heat treatment step depending on the content of TEOS.

[0072] For example, if the inorganic binder precursor is TEOS, it can be converted into a white crystalline phase (powder) after the heat treatment step. If the inorganic binder precursor is TEOS and NaOMe, it can be converted into an amorphous glassy phase after the heat treatment step. If the inorganic binder precursor is TEOS, NaOMe, and AlOEt and the ratio of each component is 5:1:1, it can be converted into an amorphous glassy phase after the heat treatment step. If the inorganic binder precursor is TEOS, NaOMe, and AlOEt and the ratio of each component is 1:1:1, it can be converted into a white crystalline phase (powder) after the heat treatment step.

[0073] That is, the strength of the MgO-C refractory can be affected depending on the content of the TEOS. In this regard, Fig. 4 shows the shape of the inorganic binder converted after the heat treatment step of the inorganic binder precursor.

[0074] The immersion process of the above-mentioned inorganic binder precursor can be performed repeatedly, but it is preferable to immerse it once or twice.

[0075]

[0076] Next, the above-mentioned hardened molded body is subjected to evaporation of water and alcohol at 80 to 120 o It may be dried for 20 to 28 hours at C.

[0077] In the above liquid inorganic binder precursor, in the drying step, the sol-gel reaction occurs and H2O and ROH generated in the sol-gel reaction are removed.

[0078] In the above drying step, the silica precursor can form a Si-OR structure through Si-OH to form a Si-O-Si chain structure (silica) by a sol-gel reaction.

[0079] In the above drying step, the sodium precursor can be converted into Na2CO3 by reacting with CO2 in the atmosphere via Na-OH through a hydrolysis reaction.

[0080] In the above drying step, the aluminum precursor can form an Al-OH structure through a hydrolysis reaction.

[0081] Therefore, through the drying step, the inorganic binder precursor can be converted into one or more solid inorganic products selected from the group consisting of silica, sodium carbonate, and aluminum hydroxide.

[0082]

[0083] The above liquid inorganic binder precursor can be converted into a solid inorganic product through a sol-gel reaction after the drying step. The converted solid inorganic product can improve the thermal and mechanical properties of MgO-C refractories. In this regard, the converted solid inorganic product is illustrated in FIG. 3.

[0084]

[0085] The above liquid inorganic binder precursor and the converted solid inorganic product can be positioned between the pores of the refractory and the MgO, graphite, and antioxidant powder particles.

[0086]

[0087] Next, the dried molded body may be heat treated at 1000 to 1600°C for 1 to 3 hours.

[0088] The above-mentioned converted solid inorganic product can be heat treated at an actual operating temperature of 1000 to 1600°C to form an amorphous or crystalline solid solution, thereby further improving the properties of the refractory.

[0089]

[0090] Conventional ladle-type MgO-C refractories are manufactured by adding graphite to MgO, which has high wear resistance, to provide a low coefficient of thermal expansion. However, the thermal and mechanical properties of the refractories deteriorate due to oxidation of graphite at high temperatures (>1300°C) during operation by molten metal. Therefore, in the present invention, an inorganic binder precursor is introduced into the refractory to manufacture MgO-C refractories that maintain a low coefficient of thermal expansion and high mechanical strength even when the graphite is oxidized. The applied inorganic binder precursor restrains the stress applied to the refractory, prevents slag penetration, and prevents refractory erosion. Therefore, in order to effectively realize the property improvement by the added inorganic binder precursor, the inorganic binder precursor must be located at the MgO particle interface. Therefore, the inorganic binder precursor is applied in a liquid state to increase the immersion efficiency between the MgO particles. Therefore, when a solid precursor is applied, the solid precursor can be dissolved and used by using an acid, base, alcohol, etc. as a solvent.

[0091]

[0092] In addition, the present invention provides a MgO-C refractory for a ladle manufactured according to the above manufacturing method.

[0093]

[0094] The above MgO-C refractory may include MgO powder, graphite, an antioxidant, and an inorganic binder. The inorganic binder may include at least one selected from the group consisting of silica, sodium silicate, sodium aluminate, mullite, and sodium aluminosilicate.

[0095]

[0096] Hereinafter, with reference to the attached drawings, the composition and manufacturing method of the MgO-C refractory for a ladle according to a preferred embodiment of the present invention will be described in detail.

[0097]

[0098] [Comparative Example 1]

[0099] Comparative Examples 1 and 2 are general MgO-C refractory manufacturing processes without applying an inorganic binder precursor.

[0100] First, 1 mm MgO powder, 140 μm fine graphite, and Al and Si as antioxidants were prepared. In addition, phenolic resin (Resol resin, CB-8052) was prepared as an organic curing agent. Each of the powder raw materials was placed in a tumbler mixer at 2.4 parts by weight of Al, 1.2 parts by weight of Si, and 18 parts by weight of fine graphite relative to 100 parts by weight of the MgO, and mixed for 30 minutes at 40 rpm to prepare a mixture. Then, 4 parts by weight of phenolic resin relative to 100 parts by weight of the mixture was added to a Hobart mixer, and the mixture was kneaded at 20°C for 30 minutes at 40 rpm. The kneaded mixture was aged at 20°C for 24 hours, and then molded by uniaxial pressing at 240 MPa. Thereafter, it was cured at 250°C for 2 hours to prepare the MgO-C refractory of Comparative Example 1.

[0101]

[0102] [Comparative Example 2]

[0103] In Comparative Example 2, the MgO-C refractory manufactured in Comparative Example 1 was heat-treated at 1400°C for 3 hours.

[0104]

[0105] [Comparative Example 3]

[0106] 1 mm MgO powder, 140 μm fine graphite, Al and Si as antioxidants, and phenolic resin (Resol resin, CB-8052) as an organic curing agent were prepared. Each of the powder raw materials was placed in a Turbula mixer at 2.4 parts by weight of Al, 1.2 parts by weight of Si, and 18 parts by weight of fine graphite relative to 100 parts by weight of the MgO, and mixed for 30 minutes at 40 rpm to prepare a mixture. Then, 4 parts by weight of phenolic resin relative to 100 parts by weight of the mixture was added to a Hobart mixer, and kneaded at 20°C for 30 minutes at 40 rpm. The kneaded mixture was aged at 20°C for 24 hours, then uniaxially pressed at 240 MPa to mold. Afterwards, it was cured at 250°C for 2 hours, and then immersed in a liquid inorganic binder precursor TEOS (tetraethyl orthosilicate). And, by drying at 100℃ for 24 hours, MgO-C refractory of Comparative Example 3 was manufactured.

[0107]

[0108] [Comparative Example 4]

[0109] Comparative Example 4 was carried out using the same process as Comparative Example 3, but an inorganic binder precursor containing TEOS and NaOMe mixed in a molar ratio of 5:1 was used as the liquid inorganic binder precursor. The MgO-C refractory of Comparative Example 4 was manufactured using the same process as above.

[0110]

[0111] [Comparative Example 5]

[0112] Comparative Example 5 was conducted using the same process as Comparative Example 3, but used an inorganic binder precursor in which TEOS, NaOMe, and AlOEt were mixed in a molar ratio of 5:1:1 as the liquid inorganic binder precursor. The MgO-C refractory of Comparative Example 5 was manufactured using the same process as above.

[0113]

[0114] [Comparative Example 6]

[0115] Comparative Example 6 was carried out using the same process as Comparative Example 3, but an inorganic binder precursor containing TEOS, NaOMe, and AlOEt mixed in a molar ratio of 1:1:1 was used as the liquid inorganic binder precursor. The MgO-C refractory of Comparative Example 6 was manufactured using the same process as above.

[0116]

[0117] [Example 1]

[0118] The MgO-C refractory of Comparative Example 3 was heat-treated at 1400°C for 3 hours to produce the MgO-C refractory of Example 1.

[0119]

[0120] [Example 2]

[0121] The MgO-C refractory of Comparative Example 4 was heat-treated at 1400°C for 3 hours to produce the MgO-C refractory of Example 2.

[0122]

[0123] [Example 3]

[0124] The MgO-C refractory of Comparative Example 5 was heat-treated at 1400°C for 3 hours to produce the MgO-C refractory of Example 3.

[0125]

[0126] [Example 4]

[0127] The MgO-C refractory of Comparative Example 6 was heat-treated at 1400°C for 3 hours to produce the MgO-C refractory of Example 4.

[0128]

[0129] Table 1 below shows the composition ratio of the inorganic binder precursor applied to comparative examples and examples.

[0130]

[0131] Example Example Example Example Example Comparative Example Component 12341TEOS1551-NaOMe-111-AlOEt--11- Unit: Molar Ratio Comparative Preliminary Comparative Preliminary Comparative Preliminary Comparative Example Component 23456TEOS-1551NaOMe--111AlOEt---11 Unit: Molar Ratio

[0132]

[0133] Below, the various experimental methods and results performed for the comparative examples and examples described above are described.

[0134]

[0135] [Experimental Example 1]

[0136] The microstructure and composition of MgO-C refractories were analyzed using SEM and EDS measurements.

[0137] As a result, it can be seen that the MgO-C refractory manufactured by Comparative Example 2 has a small content of Al and Si located between the particles. This is shown in Fig. 5.

[0138] Additionally, the MgO-C refractories manufactured by Examples 1 and 2 contained more Si between the MgO particles compared to Comparative Example 2.

[0139] Likewise, it was found that the Al content in Examples 3 and 4 also increased compared to Comparative Example 2. This is because the liquid inorganic binder precursor formed a solid product and solid solution between the MgO particles through drying and heat treatment steps. This is shown in Figures 6 to 9.

[0140]

[0141] [Experimental Example 2]

[0142] XRD analysis of MgO-C refractories was performed. As a result of analyzing the MgO-C refractories manufactured in Comparative Examples 3 to 6 and Comparative Example 1, peaks of C due to MgO, antioxidants Al, Si, and graphite were detected. However, due to the penetration of a small amount of inorganic binder precursor in Comparative Examples 3 to 6, the intensity of the peak of the inorganic product was too small, making analysis difficult. This is shown in Fig. 10.

[0143] Similarly, the MgO-C refractories manufactured in Examples 1 to 4 and Comparative Example 2 were analyzed, and the graphite peak disappeared due to carbon oxidation in the XRD results of Fig. 10. In addition, as mentioned in Fig. 10, peak analysis of a solid solution using an inorganic binder precursor was difficult, so in Experimental Example 3, XRD was measured by drying and heat-treating only the inorganic binder precursor. This is shown in Fig. 11.

[0144]

[0145] [Experimental Example 3]

[0146] XRD analysis was performed after drying of the inorganic binder precursor applied in Comparative Examples 3 to 6.

[0147] As a result, in all cases of Comparative Examples 3 to 5, an amorphous peak was detected, and in Comparative Examples 4 and 5, the peak shifted to the right compared to amorphous SiO2 due to mixing of inorganic reactants after hydrolysis of NaOMe and AlOEt into amorphous SiO2.

[0148] In Comparative Example 6, a peak was observed in which amorphous SiO2 and inorganic reactants were mixed after hydrolysis of NaOMe and AlOEt due to the high content of NaOMe and AlOEt. This is shown in Figure 12.

[0149]

[0150] [Experimental Example 4]

[0151] XRD analysis was performed after heat treatment of the inorganic binder precursors applied in Examples 1 to 4. As a result, Examples 2 and 3 transformed into an amorphous glass phase after heat treatment, and XRD analysis could not be performed. This is shown in Fig. 4.

[0152] Meanwhile, Example 1 showed a phase change to cristobalite after heat treatment, and Example 4 detected a large amount of nepherine and albeite, which are solid solutions of SiO2, Na2CO3, and Al(OH)2, after heat treatment. This is shown in Fig. 13.

[0153]

[0154] [Experimental Example 5]

[0155] As a result of measuring the fracture strength of MgO-C refractories, as shown in Fig. 14, it was found that the addition of an inorganic binder precursor significantly increased the fracture strength of the refractory. This is because the inorganic binder precursor exists between the MgO-C particles, which compensates for the disadvantage of graphite oxidation. In addition, it was found that even with the same inorganic binder precursor component, the formation of a crystalline phase had a greater effect on the improvement of the fracture strength than the amorphous phase (Examples 3 and 4 compared to Comparative Examples 5 and 6). In addition, the fracture strength was significantly increased after drying due to the reaction between the inorganic products formed after heat treatment.

[0156]

[0157] [Experimental Example 6]

[0158] As a result of measuring the coefficient of thermal expansion of MgO-C refractories, as shown in Fig. 15, it was found that the coefficient of thermal expansion of MgO-C refractories was drastically reduced by the introduction of an inorganic binder precursor. Therefore, it is possible to manufacture a ladle-use MgO-C refractory with a reduced coefficient of thermal expansion and a 10-fold increase in rupture strength by adding an inorganic binder precursor.

[0159]

[0160] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. A step of preparing a mixture by mixing MgO powder, graphite and an antioxidant; A step of mixing and kneading an organic curing agent into the above mixture; A step of aging the above-mentioned mixed mixture; A step of forming the aged mixture to produce a molded body; A step of hardening the manufactured molded body; A step of immersing the above-mentioned hardened molded body into a liquid inorganic binder precursor; A step of drying the above immersed molded body; and A method for manufacturing a MgO-C refractory for a ladle, characterized by including a step of heat-treating the dried molded body.

2. In paragraph 1, The above drying step is, A method for manufacturing a MgO-C refractory for a ladle, characterized in that the immersed molded body is dried at 80 to 120°C for 20 to 28 hours.

3. In paragraph 1, The above heat treatment step is, A method for manufacturing a MgO-C refractory for a ladle, characterized in that the dried molded body is heat treated at 1000 to 1600°C for 1 to 3 hours.

4. In paragraph 1, A method for manufacturing a MgO-C refractory for a ladle, characterized in that it may further include a CIP (Cold Isostatic Pressing) process step after the step of manufacturing the above-mentioned molded body.

5. In paragraph 1, The above-mentioned inorganic binder precursor is in liquid form, A method for manufacturing a MgO-C refractory for a ladle, characterized in that at least one precursor is selected from the group consisting of a silica precursor, a sodium precursor, and an aluminum precursor.

6. In paragraph 5, A method for manufacturing a ladle-use MgO-C refractory, characterized in that the weight ratio of the silica precursor, sodium precursor and aluminum precursor is 1:1:1 to 6:1:

1.

7. In paragraph 1, The above-mentioned inorganic binder precursor is, A method for manufacturing a MgO-C refractory for a ladle, characterized in that the solid inorganic product is converted from a liquid phase by a sol-gel reaction after the drying step.

8. MgO-C refractory for ladle, characterized by being manufactured by the manufacturing method of Article 1 9. MgO-C refractory for ladle characterized by containing MgO powder, graphite, antioxidant and inorganic binder 10. In paragraph 9, MgO-C refractory characterized in that the above inorganic binder comprises at least one selected from the group consisting of silica, sodium silicate, sodium aluminate, mullite and sodium aluminosilicate.

Images