Method for producing low-carbon mgO-c refractory

Abstract

The application provides a preparation method of low-carbon MgO-C refractory material, and the method comprises the following steps: performing light calcination treatment on magnesite micro powder to obtain light calcined magnesia powder; adding 1-10wt% of alpha-Al2O3 micro powder into the light calcined magnesia powder and then performing ball milling treatment to obtain mixed powder; performing first machine pressing forming on the mixed powder to obtain a green body; drying and high-temperature treating the green body and then cooling to room temperature to obtain magnesia refractory raw material containing intergranular spinel; then performing crushing treatment to obtain magnesia particles and magnesia fine powder with different particle sizes; uniformly mixing the magnesia particles, the magnesia fine powder, flake graphite and an antioxidant as refractory material raw material, adding phenolic resin and then mixing in a mixing machine, performing second machine pressing forming and solidification treatment on the mixture formed by the mixing to obtain low-carbon MgO-C refractory material. The low-carbon MgO-C refractory material prepared from the raw material has excellent oxidation resistance and service life under a high-temperature low-oxygen partial pressure atmosphere, and is beneficial to the smelting of special steel / alloy.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of refractory materials, in particular to a preparation method of low-carbon MgO-C refractory material. BACKGROUND

[0002] Refractory materials are directly applied to high-temperature industrial production processes in various fields of the national economy such as steel, non-ferrous, cement, glass, ceramics and chemical industry, machinery, electric power and the like, and are essential basic materials to ensure the operation and technical development of the above industries. Low-carbon MgO-C refractory material has excellent thermal shock resistance and slag corrosion resistance, and is widely used in various high-temperature industrial refractory materials. The service performance and service life of the low-carbon MgO-C refractory material are directly related to the normal operation of the high-temperature industry and the final quality of the product.

[0003] C in the low-carbon MgO-C refractory material is easily oxidized indirectly by reacting with MgO at high temperature. In particular, under the condition of low oxygen partial pressure refining, the starting temperature of the reaction between MgO and C is further reduced, and the oxidation of MgO-C refractory material is more serious, which limits the application of MgO-C refractory material in high-temperature low-oxygen partial pressure refining environment. The existing methods for improving the oxidation resistance of low-carbon MgO-C refractory material include adding antioxidants and coating antioxidant coatings, but the existing antioxidant measures have problems such as complex coating process, difficult control of coating uniformity and strength, and high cost of antioxidants. In addition, the existing low-carbon MgO-C refractory material still has unsatisfactory oxidation resistance and mechanical properties, which need to be improved. SUMMARY

[0004] The application provides a preparation method of low-carbon MgO-C refractory material, which comprises the following steps:

[0005] Light calcination treatment is performed on magnesite powder to obtain light calcined magnesia powder, and 1-10wt% of alpha-Al2O3 powder is added to the light calcined magnesia powder for ball milling treatment to obtain mixed powder;

[0006] The mixed powder is subjected to first machine pressing forming to obtain a green body, and then the green body is dried and subjected to high-temperature treatment and then cooled to room temperature to obtain magnesia refractory raw material containing intergranular spinel;

[0007] The magnesia refractory raw material containing intergranular spinel is subjected to crushing treatment to obtain magnesia particles and magnesia fine powder with different particle sizes;

[0008] 60-75wt% of the magnesia particles, 20-35wt% of the magnesia fine powder, 1-5wt% of flake graphite and 1-4wt% of antioxidant are uniformly mixed as refractory material raw material, phenolic resin is added to the refractory material raw material, and the mixture is mixed in a mixer, the mixed mixture is subjected to second machine pressing forming and solidification treatment to obtain low-carbon MgO-C refractory material.

[0009] Further, the mass fraction of the phenolic resin is 1-3wt% of the raw material of the refractory.

[0010] Further, the light treatment is at 800-1000℃ for 2-5h.

[0011] Further, the mass fraction of MgO in the magnesite micro-powder is greater than 45wt%, and the average particle size is 1-10μm.

[0012] Further, the alumina is α-Al2O3 micro-powder, and the purity of the α-Al2O3 micro-powder is greater than 99wt%, and the average particle size is 1-5μm.

[0013] Further, the magnesite includes magnesite particles and magnesite micro-powder, and the gradation of the magnesite particles is: 3-2mm is 23-32wt%, 2-1mm is 21-25wt%, 1-0.088mm is 16-18wt%, and the particle size of the magnesite fine powder is less than or equal to 0.088mm.

[0014] Further, the antioxidant is at least one of aluminum powder and silicon powder, and the particle size is less than or equal to 0.088mm.

[0015] Further, the graphite is flake graphite, and the particle size of the flake graphite is less than or equal to 0.149mm.

[0016] Further, the drying and high-temperature treatment is drying at 110-200℃ for 24-48h, and holding at 1550-1700℃ for 1-5h; and the solidification treatment is holding at 150-240℃ for 24h.

[0017] Further, the forming pressure in the first time of the machine-press forming treatment is 50-100MPa, and the forming pressure in the second time of the machine-press forming treatment is 150-250MPa.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The alpha-Al2O3 micropowder can react with MgO in magnesite and generate spinel phase between the crystals, and the migration of the intergranular spinel to the grain boundary has a pinning effect in the sintering process, the grain boundary migration is inhibited, the pores on the grain boundary are eliminated, which can significantly reduce the porosity of magnesite refractory raw material and improve the relative density of magnesite refractory raw material. At the same time, part of the MgO is consumed due to the generation of spinel phase, so that the oxygen vacancy content in the magnesite refractory raw material is reduced, and the active oxygen content such as superoxide free radical is greatly reduced. Therefore, after the introduction of alpha-Al2O3 micropowder, the magnesite refractory raw material has lower superoxide free radical content, which ensures the integrity of the phenolic resin network structure, and can significantly reduce the oxidation corrosion rate of MgO-C refractory material.

[0020] The magnesite refractory raw material containing intergranular spinel prepared by the present application can significantly reduce the porosity and oxidation activity of low-carbon MgO-C refractory material, inhibit the oxidation process of low-carbon MgO-C refractory material under high-temperature and low-oxygen partial pressure atmosphere conditions, improve the oxidation resistance, mechanical properties and service life of low-carbon MgO-C refractory material under high-temperature and low-oxygen partial pressure atmosphere conditions, and is beneficial to the smelting of special steel / alloy. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flowchart of the preparation method of the low-carbon MgO-C refractory material of the present application;

[0022] Figure 2 is an SEM image of the low-carbon MgO-C refractory material of the present application; DETAILED DESCRIPTION

[0023] The present application will be further described below in combination with specific embodiments:

[0024] Example 1

[0025] Figure 1 is a flowchart of the preparation method of the low-carbon MgO-C refractory material provided by the present application, as Figure 1 shown, the method comprises the following steps:

[0026] The magnesite micropowder is subjected to light calcination treatment to obtain light calcined magnesia powder, and 1-10wt% of alpha-Al2O3 micropowder is added to the light calcined magnesia powder and then subjected to ball milling treatment to obtain a mixed powder;

[0027] The mixed powder is subjected to first machine pressing forming to obtain a green body, and then the green body is subjected to drying and high-temperature treatment and then cooled to room temperature to obtain a magnesite refractory raw material containing intergranular spinel;

[0028] The magnesite refractory raw material containing intergranular spinel is subjected to crushing treatment to obtain magnesia particles and magnesia fine powder with different particle sizes;

[0029] 60-75wt% of the magnesia particles, 20-35wt% of the magnesia fine powder, 1-5wt% of flake graphite and 1-4wt% of antioxidant are mixed uniformly as the raw material of refractory, and after adding phenolic resin in the raw material of refractory, the mixture is mixed in a mixing machine, and the mixture formed by the mixing is subjected to second machine pressing forming and curing treatment, thereby obtaining the low-carbon MgO-C refractory material.

[0030] It should be noted that the intergranular spinel has a pinning effect on the migration of grain boundaries, the migration of grain boundaries is inhibited, the pores on the grain boundaries are eliminated, which can significantly reduce the porosity of magnesia refractory raw material and improve the relative density of magnesia refractory raw material.

[0031] The traditional magnesia refractory raw material contains a certain amount of active oxygen such as superoxide radical, which is easy to react with C and be oxidized under high temperature and low oxygen partial pressure atmosphere, which can cause premature oxidation and erosion of MgO-C refractory material. The reaction activity in service is closely related to the material density, grain boundary composition, and oxygen vacancy content in the material. Oxygen vacancies can provide effective electron orbits to combine with oxygen-containing small molecules, promote the transfer of electrons from the electron orbits of Mg to oxygen, and form superoxide radicals. The unpaired electrons on the outer orbit of superoxide radical are easy to transfer, and at the same time, the network structure of phenolic resin is destroyed, so the magnesia refractory raw material with higher content of superoxide radical has higher reaction activity.

[0032] In the embodiment, the magnesite powder is subjected to light burning treatment to obtain light burned magnesia powder, and the light burned magnesia powder is mixed with alumina, and sequentially subjected to ball milling treatment, machine pressing forming treatment, drying treatment and annealing treatment to obtain magnesia refractory raw material containing intergranular spinel, and the magnesia refractory raw material containing intergranular spinel is subjected to crushing treatment to obtain magnesia with different particle sizes.

[0033] The alumina is α-Al2O3 powder, and the purity of the α-Al2O3 powder is greater than 99wt%, and the average particle size is 1-5μm; the present application introduces α-Al2O3 powder, which can react with MgO in magnesite and generate spinel phase between the crystals, and in the sintering process, the intergranular spinel has a pinning effect on the migration of grain boundaries, the migration of grain boundaries is inhibited, the pores on the grain boundaries are eliminated, which can significantly reduce the porosity of magnesia refractory raw material and improve the relative density of magnesia refractory raw material. At the same time, part of the MgO is consumed due to the generation of spinel phase, so that the oxygen vacancy content in the magnesia refractory raw material is reduced, and the content of active oxygen such as superoxide radical is greatly reduced. Therefore, after introducing the α-Al2O3 powder, the magnesia refractory raw material has lower content of superoxide radical, which ensures the integrity of the network structure of phenolic resin, and can significantly reduce the oxidation and erosion rate of MgO-C refractory material.

[0034] Figure 2It is the SEM diagram of the low-carbon MgO-C refractory provided by the application, and it can be seen from the diagram that the spinel (MA) and magnesium oxide (MgO) are uniformly distributed, and there is no stacking problem, based on which the oxidation activity of the low-carbon MgO-C refractory can be reduced, and the refractory performance thereof is ensured.

[0035] The low-carbon MgO-C refractory material prepared by using the magnesia refractory raw material containing intergranular spinel prepared by the application can significantly reduce the porosity and oxidation activity of the low-carbon MgO-C refractory material, inhibit the oxidation process of the low-carbon MgO-C refractory material under the condition of high-temperature low-oxygen partial pressure atmosphere, improve the oxidation resistance, mechanical properties and service life of the low-carbon MgO-C refractory material under the condition of high-temperature low-oxygen partial pressure atmosphere, and is beneficial to the smelting of special steel / alloy.

[0036] The magnesia refractory raw material containing intergranular spinel prepared by the application is detected as follows:

[0037] Bulk density: 3.40-3.58 g / cm 3 ;

[0038] True density: 3.50-3.65 g / cm 3 ;

[0039] Apparent porosity: 1.0-4.0%;

[0040] Closed porosity: 1.0-4.5%;

[0041] Relative density: 93%-98%;

[0042] Superoxide radical content: (2.6-3.8) x 10 -5 mol / g;

[0043] The long-life low-carbon MgO-C refractory material prepared from the magnesia refractory raw material under the condition of high-temperature low-oxygen partial pressure atmosphere has a weight loss rate of 2-6% after being kept at 1450 DEG C for 1 h under low-oxygen pressure atmosphere.

[0044] Example 2

[0045] To avoid repetition, the materials involved in Example 2 are described as follows, and the subsequent examples will not be described again.

[0046] The MgO content in the magnesite is >45 wt%, and the average particle size is 1-10 um.

[0047] The content of α-Al2O3 in the α-Al2O3 micropowder is >99 wt%, and the average particle size is 1-5 um.

[0048] The particle size of the magnesia fine powder is ≤0.088mm.

[0049] The particle size of the magnesia fine powder is ≤0.088mm.

[0050] The particle size of the flake graphite is ≤0.149mm.

[0051] The antioxidant is at least one of Al powder and Si powder, and the particle size is ≤0.088mm.

[0052] In the embodiment, the magnesite powder is heated at 800-900℃ for 2-3h to obtain light-burned magnesia powder; 1-4wt% of α-Al2O3 powder is added to the light-burned magnesia powder, and the mixture is uniformly mixed in a planetary ball mill to obtain a mixed powder;

[0053] The mixed powder is formed by machine pressing under 50-80MPa to obtain a green body; the green body is dried at 110-150℃ for 24-36h, and then heated at 1550-1650℃ for 1-3h and cooled to room temperature to obtain magnesia refractory raw material containing intergranular spinel; the magnesia refractory raw material containing intergranular spinel is crushed to obtain magnesia particles and magnesia fine powder with different particle sizes;

[0054] 60-65wt% of the magnesia particles, 25-30wt% of the magnesia fine powder, 2-4wt% of the flake graphite, 2-4wt% of the antioxidant, and 2-3wt% of the phenolic resin are uniformly mixed and then mixed in a mixer; the mixed material is formed by machine pressing under a forming pressure of 150-200MPa, and then cured by heat treatment at 150-200℃ for 24h to obtain low-carbon MgO-C refractory material.

[0055] The magnesia refractory raw material containing intergranular spinel prepared in the embodiment is detected to obtain the following experimental parameters:

[0056] Bulk density: 3.40-3.45g / cm 3 ;

[0057] True density: 3.50-3.54g / cm 3 ;

[0058] Apparent porosity: 2.5-4.0%;

[0059] Closed porosity: 3.5-4.5%;

[0060] Relative density: 93%-94%;

[0061] Superoxide radical content: (2.6-3)×10 -5mol / g;

[0062] The weight loss rate of the low-carbon MgO-C refractory material prepared from this magnesia refractory raw material is 3-5% after being kept at 1450℃ for 1 hour in a low oxygen pressure atmosphere.

[0063] Example 3

[0064] In this embodiment, magnesite powder is kept at 800-900℃ for 3-5 hours to obtain lightly calcined magnesia powder; then 4-8 wt% of α-Al2O3 powder is added to the lightly calcined magnesia powder and mixed in a planetary ball mill to obtain a mixed powder.

[0065] The mixed powder is machine-pressed at 75–100 MPa to obtain a green body; then the green body is dried at 150–200℃ for 36–48 h, held at 1550–1650℃ for 3–5 h, and cooled to room temperature to obtain a magnesia refractory material containing intergranular spinel; the magnesia refractory material containing intergranular spinel is crushed to obtain magnesia particles and magnesia fine powder of different particle sizes;

[0066] 60-65 wt% magnesia particles, 30-35 wt% fine magnesia powder, 3-5 wt% flake graphite, and 1-3 wt% antioxidant are mixed evenly, and then 2-3 wt% phenolic resin is added to the above raw materials and the mixture is kneaded in a mixer. The mixed material is then machine-pressed under a molding pressure of 150-200 MPa, and then cured at 200-240℃ for 24 hours to obtain low-carbon MgO-C refractory material.

[0067] The magnesia refractory raw material containing intergranular spinel prepared in this embodiment was tested and the following experimental parameters were obtained:

[0068] Bulk density: 3.43~3.48 g / cm³ 3 ;

[0069] True density: 3.52~3.57 g / cm³ 3 ;

[0070] Apparent porosity: 2.0–3.0%;

[0071] Porosity: 3.0–4.0%;

[0072] Relative density: 94%–96%;

[0073] Superoxide radical content: (3~3.4)×10 -5 mol / g;

[0074] The low-carbon MgO-C refractory material prepared from this magnesia refractory raw material has a weight loss rate of 4.5-6% after being kept at 1450℃ for 1 hour in a low oxygen pressure atmosphere.

[0075] Example 4

[0076] In this embodiment, magnesite powder is kept at 900-1000℃ for 2-3 hours to obtain lightly calcined magnesia powder; then 1-4 wt% of α-Al2O3 powder is added to the lightly calcined magnesia powder and mixed in a planetary ball mill to obtain a mixed powder.

[0077] The mixed powder is machine-pressed at 50-80 MPa to obtain a green body; then the green body is dried at 110-150℃ for 24-36 h, held at 1550-1650℃ for 1-5 h, and cooled to room temperature to obtain a magnesia refractory material containing intergranular spinel; the magnesia refractory material containing intergranular spinel is crushed to obtain magnesia particles and magnesia fine powder of different particle sizes;

[0078] 70-75 wt% magnesia particles, 20-25 wt% fine magnesia powder, 1-3 wt% flake graphite, and 2-4 wt% antioxidant are mixed evenly, and then 1-2 wt% phenolic resin is added to the above raw materials and the mixture is kneaded in a mixer. The mixed material is then machine-pressed under a molding pressure of 200-250 MPa, and then cured at 200-240℃ for 24 hours to obtain low-carbon MgO-C refractory material.

[0079] The magnesia refractory raw material containing intergranular spinel prepared in this embodiment was tested and the following experimental parameters were obtained:

[0080] Bulk density: 3.46~3.51 g / cm³ 3 ;

[0081] True density: 3.55~3.60 g / cm³ 3 ;

[0082] Apparent porosity: 1.5–3%;

[0083] Porosity: 2.5–3.5%;

[0084] Relative density: 95%–96%;

[0085] Superoxide radical content: (2.8~3.4)×10 -5 mol / g;

[0086] The low-carbon MgO-C refractory material prepared from this magnesia refractory raw material has a weight loss rate of 2-3.5% after being kept at 1450℃ for 1 hour in a low oxygen pressure atmosphere.

[0087] Example 5

[0088] In this embodiment, magnesite powder is heated at 900-1000℃ for 2-3 hours to obtain lightly calcined magnesia powder; then 4-8 wt% of α-Al2O3 powder is added to the lightly calcined magnesia powder and mixed in a planetary ball mill to obtain a mixed powder.

[0089] The mixed powder is machine-pressed under 50-80 MPa to obtain a green body; then the green body is dried at 110-150℃ for 36-48 h, held at 1600-1700℃ for 1-3 h, and cooled to room temperature to obtain a magnesia refractory material containing intergranular spinel; the magnesia refractory material containing intergranular spinel is crushed to obtain magnesia particles and magnesia fine powder of different particle sizes;

[0090] 65-70 wt% magnesia particles, 20-25 wt% fine magnesia powder, 2-4 wt% flake graphite, and 2-4 wt% antioxidant are mixed evenly, and then 1-2 wt% phenolic resin is added to the above raw materials and the mixture is kneaded in a mixer. The mixed material is then machine-pressed under a molding pressure of 200-250 MPa, and then cured at 200-240℃ for 24 hours to obtain low-carbon MgO-C refractory material.

[0091] The magnesia refractory raw material containing intergranular spinel prepared in this embodiment was tested and the following experimental parameters were obtained:

[0092] Bulk density: 3.49~3.55g / cm³ 3 ;

[0093] True density: 3.58~3.63g / cm³ 3 ;

[0094] Apparent porosity: 1-2%;

[0095] Porosity: 2.0–3.0%;

[0096] Relative density: 96%–97%;

[0097] Superoxide radical content: (3.2~3.6)×10 -5 mol / g;

[0098] The low-carbon MgO-C refractory material prepared from this magnesia refractory raw material has a weight loss rate of 3-4.5% after being kept at 1450℃ for 1 hour in a low oxygen pressure atmosphere.

[0099] Example 6

[0100] In this embodiment, magnesite powder is kept at 900-1000℃ for 3-5 hours to obtain lightly calcined magnesia powder; then 6-10 wt% of α-Al2O3 powder is added to the lightly calcined magnesia powder and mixed in a planetary ball mill to obtain a mixed powder.

[0101] The mixed powder is machine-pressed at 75–100 MPa to obtain a green body; then the green body is dried at 150–200℃ for 36–48 h, held at 1600–1700℃ for 3–5 h, and cooled to room temperature to obtain a magnesia refractory material containing intergranular spinel; the magnesia refractory material containing intergranular spinel is crushed to obtain magnesia particles and magnesia fine powder of different particle sizes;

[0102] 60-65 wt% magnesia particles, 25-30 wt% fine magnesia powder, 3-5 wt% flake graphite, and 1-3 wt% antioxidant are mixed evenly, and then 1-2 wt% phenolic resin is added to the above raw materials and the mixture is kneaded in a mixer. The mixed material is then machine-pressed under a molding pressure of 200-250 MPa, and then cured at 150-200℃ for 24 hours to obtain low-carbon MgO-C refractory material.

[0103] The magnesia refractory raw material containing intergranular spinel prepared in this embodiment was tested and the following experimental parameters were obtained:

[0104] Bulk density: 3.53~3.58 g / cm³ 3 ;

[0105] True density: 3.61~3.65g / cm³ 3 ;

[0106] Apparent porosity: 1–1.5%;

[0107] Porosity: 1.5–2.5%;

[0108] Relative density: 96%–98%;

[0109] Superoxide radical content: (3.4~3.8)×10 -5 mol / g;

[0110] The low-carbon MgO-C refractory material prepared from this magnesia refractory raw material has a weight loss rate of 4-5.5% after being kept at 1450℃ for 1 hour in a low oxygen pressure atmosphere.

[0111] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a low-carbon MgO-C refractory material, characterized in that, Includes the following steps: Magnesite powder is lightly calcined to obtain lightly calcined magnesia powder. 1-10 wt% of α-Al2O3 powder is added to the lightly calcined magnesia powder and then ball-milled to obtain a mixed powder. The mixed powder is first machine-pressed to obtain a green body, and then the green body is dried and treated at high temperature and cooled to room temperature to obtain a magnesia refractory raw material containing intergranular spinel; The magnesia refractory raw material containing intergranular spinel is crushed to obtain magnesia particles and magnesia fine powder of different sizes. 60-75 wt% of the magnesia particles, 20-35 wt% of the magnesia fine powder, 1-5 wt% of flake graphite and 1-4 wt% of antioxidant are mixed evenly as refractory material raw materials. Phenolic resin is added to the refractory material raw materials and then the mixture is mixed in a mixer. The mixture formed by the mixing is subjected to a second machine pressing and curing treatment to obtain low carbon MgO-C refractory material. The light calcination treatment involves holding the material at 800-1000 ℃ for 2-5 hours; the drying and high-temperature treatment involves drying at 110-200 ℃ for 24-48 hours and holding the material at 1550-1700 ℃ for 1-5 hours; and the curing treatment involves holding the material at 150-240 ℃ for 24 hours.

2. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The phenolic resin has a mass fraction of 1 to 3 wt% of the refractory material raw materials.

3. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The magnesite powder contains MgO with a mass fraction greater than 45 wt% and an average particle size of 1~10 μm.

4. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The α-Al2O3 micro powder has a purity greater than 99 wt% and an average particle size of 1~5 μm.

5. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The particle size distribution of the magnesia is as follows: 23-32 wt% for 3-2 mm, 21-25 wt% for 2-1 mm, and 16-18 wt% for 1-0.088 mm. The particle size of the fine magnesia powder is less than or equal to 0.088 mm.

6. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The antioxidant is at least one of aluminum powder and silicon powder, and the particle size is less than or equal to 0.088 mm.

7. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The particle size of the flake graphite is less than or equal to 0.149 mm.

8. The method for preparing low-carbon MgO-C refractory material according to claim 1, characterized in that, The molding pressure during the first machine pressing process is 50~100MPa, and the molding pressure during the second machine pressing process is 150~250MPa.

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