A refractory material for the tapping hole of a high-temperature electric furnace and its preparation method

Abstract

The present invention relates to the field of refractory materials, specifically to a refractory material for the tapping hole of a high-temperature electric furnace and a preparation method thereof. Calculated by weight parts, it includes: 80-100 parts of magnesite, 20-40 parts of tabular corundum, 0.1-0.5 parts of calcium chloride, 1-3 parts of boric acid, 5-15 parts of composite carbon raw material, 1-5 parts of antioxidant, and 5-10 parts of binder. The composite carbon raw material includes expanded graphite and graphene coated on the surfaces of the magnesite and tabular corundum. The refractory material prepared by the present invention has good mechanical properties and excellent antioxidant and thermal shock resistance.

Description

Technical Field

[0001] The present invention relates to the field of refractories, and particularly to a refractory for the tapping hole of a high-temperature electric furnace and a preparation method thereof. Background Art

[0002] The iron and steel industry is one of the important pillar industries of the national economy. Since the 1970s, the iron and steel industry has made rapid progress, strongly supporting the rapid development of industries such as manufacturing, construction, and consumer goods. At the same time, new requirements have also been put forward for refractories. MgO and Al2O3 have relatively high melting points and strong erosion resistance, and are important materials for making the tapping holes of blast furnaces. However, due to the relatively high thermal expansion coefficients of MgO and Al2O3, the thermal shock resistance of MgO and Al2O3 is poor, and the service life is reduced. Graphite has excellent properties such as poor wettability of molten slag, small linear expansion coefficient, and good thermal conductivity. Making graphite into carbon-containing refractories can significantly improve the slag erosion resistance and thermal shock stability of refractories. However, in a high-temperature oxidation atmosphere, graphite is easily oxidized and forms pores, which will lead to a decrease in the mechanical properties of refractories. Summary of the Invention

[0003] Object of the Invention: Aiming at the above technical problems, the present invention provides a refractory for the tapping hole of a high-temperature electric furnace and a preparation method thereof.

[0004] The technical solution adopted is as follows:

[0005] A refractory for the tapping hole of a high-temperature electric furnace, in parts by weight, includes:

[0006] 80-100 parts of magnesite, 20-40 parts of tabular corundum, 0.1-0.5 part of calcium chloride, 1-3 parts of boric acid, 5-15 parts of composite carbonaceous raw material, 1-5 parts of antioxidant, and 5-10 parts of binder;

[0007] The composite carbonaceous raw material includes expanded graphite and graphene coated on the surfaces of the magnesite and tabular corundum.

[0008] Further, the weight ratio of the expanded graphite to the graphene is 5-10:0.01-1.

[0009] Further, the surface of the expanded graphite is coated with TaC and / or HfC.

[0010] Further, the antioxidant is silicon carbide powder and / or aluminum-silicon composite powder.

[0011] Further, the binder is a composition of silica sol and / or titanium sol and an organic resin.

[0012] Further, the weight percentage of the organic resin in the binder is ≥90%.

[0013] Further, the organic resin is a silicone-modified phenolic resin.

[0014] Further, the preparation method of the silicone-modified phenolic resin is as follows:

[0015] Mix phenol, silicone resin, and formaldehyde, heat up to 85 - 95 °C, stir for 30 - 60 min, add an alkaline catalyst, continue to react for 60 - 120 min, then heat up to 120 - 140 °C and distill until no liquid distillate comes out, then cool down to 40 - 50 °C. The obtained light yellow viscous product can be adjusted in viscosity with ethanol.

[0016] Further, the alkaline catalyst is sodium hydroxide and / or potassium hydroxide.

[0017] The present invention also provides a preparation method of a refractory material for the tapping hole of a high-temperature electric furnace:

[0018] Using expanded graphite, Ta, and / or Hf as raw materials, after fully grinding and mixing evenly, load them into a crucible. Place the crucible in a self-propagating high-temperature furnace, seal and evacuate, then fill with argon to normal pressure, ignite. Grind the obtained product to get the first component. Deposit a graphene layer on the surface of the magnesia and tabular corundum to get the second component. Mix the first component, the second component, calcium chloride, boric acid, an antioxidant, and a binder evenly, and press them into shape. When pressing, first pressurize to 100 - 120 MPa, then hold the pressure for 10 - 30 s and then release the pressure, and finally pressurize to 100 - 120 MPa again. After drying the obtained green body, sinter it at 1400 - 1500 °C for 2 - 4 h.

[0019] The beneficial effects of the present invention:

[0020] The present invention provides a refractory material for a high-temperature electric furnace tapping hole. The composite carbon raw material comprises expanded graphite and graphene coated on the surface of the magnesia sand and the plate-shaped corundum. The expanded graphite can be regarded as composed of countless graphene nanosheets superimposed on each other, and can form a carbon network structure in the refractory material, and generate pull-out, bridging and other mechanisms to further improve the mechanical properties of the refractory material. After being coated with TaC and / or HfC, the oxidation of the expanded graphite is effectively slowed down, the surface roughness is improved, and the interface bonding strength with the matrix material is increased. The introduction of graphene can not only block pores and gaps, but also improve the density of the refractory material. degree, and can also absorb and release thermal stress to improve thermal shock resistance. The binder contains organic silicon and inorganic silicon, which can optimize the performance and structure of pyrolytic carbon, increase the residual carbon rate, promote the formation of ceramic phase, and significantly improve the various properties of refractory materials. Calcium chloride, as an ionic inorganic salt, can react with alumina at high temperature to generate CA6, which plays a reinforcing role. Boric acid can eliminate the harm of sodium oxide in plate-like corundum, inhibit the increase of alumina grains, and can also react with calcium chloride to generate calcium borate, thereby improving the performance of refractory materials. The refractory material prepared by the present invention has good mechanical properties and excellent antioxidant and thermal shock resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the SEM image of the refractory material prepared in Example 1. DETAILED DESCRIPTION

[0022] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. The techniques not mentioned in the present invention are all referenced to the prior art. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0023] Embodiment 1:

[0024] A method for preparing refractory material for high-temperature electric furnace tap hole:

[0025] Take 75g of expanded graphite (150μm) and 18.1g of Ta powder (25μm), grind and mix thoroughly, and then pile them tightly in a crucible. Then put the crucible in a self-propagating high-temperature furnace, seal the self-propagating high-temperature furnace, evacuate it, and then fill it with argon to make the interior reach normal pressure. Use tungsten wire to heat and ignite the mixture. The gray-black product obtained is ground and recorded as the first component. Magnesium sand (45μm, w (MgO) %≥99%)900g, plate-shaped corundum(45μm, w (Al2O3)(with a purity of ≥99%) 300 g is placed on a clean quartz boat and put into the heating area of the sliding rail furnace in the chemical vapor deposition system. After evacuation and three times of argon cleaning to ensure an oxygen-free environment, argon is first introduced to make the pressure in the quartz tube normal, and then the atmosphere is adjusted to a mixed gas of hydrogen and argon (volume ratio 1:1). The flow rate of the mixed gas is 20 cm 3 / min. It starts to be heated at a rate of 10 °C / min to 1000 °C, and then a mixed gas of hydrogen and methane (volume ratio 2:1) is introduced. The flow rate of the mixed gas is 30 cm 3 / min. After maintaining for 60 min, argon with a flow rate of 150 cm 3 / min is introduced to cool down to room temperature, and magnesite and tabular corundum with graphene deposited on the surface can be obtained. By comparing the weights before and after, the weight of the deposited graphene is 0.8 g, which is recorded as the second component. The first component, the second component, 2.5 g of calcium chloride, 20 g of boric acid, 30 g of silicon carbide powder, 10 g of silica sol (average particle size 11 nm, pH = 9.8, solid content 30%), and 90 g of organosilicon-modified phenolic resin are mixed evenly and pressed into shape. When pressing, first pressurize to 120 MPa, then hold the pressure for 20 s and then relieve the pressure, and finally pressurize to 100 MPa. The obtained green body is dried at 180 °C for 10 h and then sintered at 1480 °C for 3 h.

[0026] Among them, the preparation method of the organosilicon-modified phenolic resin is as follows:

[0027] 109.2 g of phenol, 2.12 g of methylphenyl silicone resin, and 81 g of formaldehyde are mixed and heated to 95 °C and stirred for 60 min. 2.5 g of sodium hydroxide is added and the reaction continues for 100 min, then it is heated to 140 °C and distilled until no liquid distillate comes out, and then cooled to 50 °C. The obtained light yellow viscous product is adjusted to a viscosity of ≤6×10 -3 Pa·s with ethanol.

[0028] Example 2:

[0029] A preparation method of refractory materials for the tapping hole of a high-temperature electric furnace:

[0030] 75 g of expanded graphite (150 μm) and 18.1 g of Ta powder (25 μm) are taken, ground and mixed evenly, and then tightly packed and loaded into a crucible. Then the crucible is placed in a self-propagating high-temperature furnace. After the self-propagating high-temperature furnace is sealed, it is evacuated and then filled with argon to make the internal pressure normal. The mixture is ignited by tungsten wire heating. The obtained gray-black product is ground and recorded as the first component. 1000 g of magnesite (45 μm, w (MgO) %≥99%) and tabular corundum (45 μm, w (Al2O3)%≥99%)400g was placed on a clean quartz boat and put into the heating area of ​​the slide rail furnace of the chemical vapor deposition system. After vacuuming and argon cleaning three times to ensure an oxygen-free environment, argon was first introduced to make the quartz tube at normal pressure, and then the atmosphere was adjusted to a mixed gas of hydrogen and argon (volume ratio of 1:1), and the flow rate of the mixed gas was 20cm 3 / min, and then heated to 1000℃ at a rate of 10℃ / min, and then introduced a mixed gas of hydrogen and methane (volume ratio of 2:1) with a flow rate of 30cm 3 / min, maintain for 60min and then pass 150cm 3 / min of argon gas to room temperature to obtain magnesia and plate-shaped corundum with graphene deposited on the surface. By comparing the weights before and after, the weight of the deposited graphene is 0.8g, which is recorded as the second component. The first component, the second component, 5g of calcium chloride, 30g of boric acid, 50g of silicon carbide powder, 10g of silica sol (average particle size 11nm, pH=9.8, solid content 30%), and 90g of organic silicon modified phenolic resin are mixed evenly and pressed into shape. During pressing, the pressure is first increased to 120MPa, and then the pressure is released after maintaining for 30s, and finally the pressure is increased to 120MPa again. The resulting rough blank is dried at 180℃ for 10h, and then sintered at 1500℃ for 3h.

[0031] Wherein, the preparation method of the organosilicon-modified phenolic resin is the same as that in Example 1.

[0032] Embodiment 3:

[0033] A method for preparing refractory material for high-temperature electric furnace tap hole:

[0034] Take 75g of expanded graphite (150μm) and 18.1g of Ta powder (25μm), grind and mix thoroughly, and then pile them tightly in a crucible. Then put the crucible in a self-propagating high-temperature furnace, seal the self-propagating high-temperature furnace, evacuate it, and then fill it with argon to make the interior reach normal pressure. Use tungsten wire to heat and ignite the mixture. The gray-black product obtained is ground and recorded as the first component. Magnesium sand (45μm, w (MgO) %≥99%)800g, plate-shaped corundum(45μm, w (Al2O3) %≥99%) 200g was placed on a clean quartz boat and put into the heating area of ​​the slide rail furnace of the chemical vapor deposition system. After vacuuming and argon cleaning three times to ensure an oxygen-free environment, argon was first introduced to make the quartz tube at normal pressure, and then the atmosphere was adjusted to a mixed gas of hydrogen and argon (volume ratio of 1:1), and the flow rate of the mixed gas was 20cm 3 / min, and then heated to 1000℃ at a rate of 10℃ / min, and then introduced a mixed gas of hydrogen and methane (volume ratio of 2:1) with a flow rate of 30cm 3 / min, keep it for 60 min and then introduce argon at 150 cm 3 / min to cool it down to room temperature, and then magnesite and tabular corundum with graphene deposited on the surface can be obtained. By comparing the weights before and after, the weight of the deposited graphene is 0.8 g, which is recorded as the second component. Mix the first component, the second component, 1 g of calcium chloride, 10 g of boric acid, 10 g of silicon carbide powder, 10 g of silica sol (average particle size 11 nm, pH = 9.8, solid content 30%), and 90 g of organosilicon-modified phenolic resin evenly, and press them into shape. When pressing, first pressurize to 100 MPa, then keep the pressure for 10 s and then release the pressure, and finally pressurize to 100 MPa again. After the obtained green body is dried at 180 °C for 10 h, it is sintered at 1400 °C for 2 h.

[0035] Among them, the preparation method of the organosilicon-modified phenolic resin is the same as that in Example 1.

[0036] Comparative Example 1:

[0037] It is basically the same as Example 1, except that calcium chloride is not added.

[0038] Comparative Example 2:

[0039] It is basically the same as Example 1, except that boric acid is not added.

[0040] Comparative Example 3:

[0041] It is basically the same as Example 1, except that TaC does not coat the surface of the expanded graphite.

[0042] Comparative Example 4:

[0043] It is basically the same as Example 1, except that graphene is not deposited on the surface of magnesite and tabular corundum.

[0044] Comparative Example 5:

[0045] It is basically the same as Example 1, except that commercially available phenolic resin (Xiangteng XT-101) is used instead of the organosilicon-modified phenolic resin.

[0046] Comparative Example 6:

[0047] It is basically the same as Example 1, except that commercially available phenolic resin (Xiangteng XT-101) is used instead of the organosilicon-modified phenolic resin and silica sol.

[0048] Performance test:

[0049] Use the refractory materials in Examples 1-3 and Comparative Examples 1-6 of the present invention as specimens for performance testing;

[0050] ①Test the compressive strength and flexural strength of the specimens at room temperature according to national standards (GB / T 5072 - 2008, GB / T 3001 - 2007);

[0051] ②The thermal shock resistance is characterized by measuring the residual rate of compressive strength and the residual rate of flexural strength of the specimens using the cold - hot cycle method. Place the specimens in a muffle furnace and heat them to 1000°C at a heating rate of 5°C / min, then hold for 30 min to make the specimens heat evenly. Then quickly take out the specimens and blow them with cold air for 30 min. After the specimens are completely cooled, it is one thermal cycle. Repeat the above steps 10 times. The calculation formulas for the residual rate of compressive strength and the residual rate of flexural strength are as follows:

[0052] Formula 1: σ1 = A2 / A1 * 100%

[0053] Where: σ1 is the residual rate of compressive strength at room temperature

[0054] A1 is the initial compressive strength at room temperature

[0055] A2 is the compressive strength at room temperature after 10 cold - hot cycles;

[0056] Formula 2: σ2 = B2 / B1 * 100%

[0057] Where: σ2 is the residual rate of flexural strength at room temperature

[0058] B1 is the initial flexural strength at room temperature

[0059] B2 is the flexural strength at room temperature after 10 cold - hot cycles;

[0060] ③The antioxidant specimens are cubic blocks with dimensions of 72 mm × 72 mm × 72 mm. After this specimen is held at 1200°C in air for 3 h and then cooled, observe the cross - section, measure the average oxidation depth (mm) of the specimen using a vernier caliper, and calculate the oxidation area rate (%) of the specimen;

[0061] The test results are shown in Table 1 below:

[0062] Table 1:

[0063]

[0064] As can be seen from Table 1 above, the refractory materials prepared by the present invention have good mechanical properties and excellent antioxidant and thermal shock resistance.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A refractory material for the tapping hole of a high-temperature electric furnace, characterized in that, Comprising, by weight parts: 80 - 100 parts of magnesite, 20 - 40 parts of tabular corundum, 0.1 - 0.5 parts of calcium chloride, 1 - 3 parts of boric acid, 5 - 15 parts of composite carbon raw material, 1 - 5 parts of antioxidant, 5 - 10 parts of binder; The composite carbon raw material includes expanded graphite and graphene coated on the surfaces of the magnesite and tabular corundum; The surface of the expanded graphite is coated with TaC; The binder is a composition of silica sol and / or titania sol and an organic resin; The weight percentage of the organic resin in the binder ≥ 90%; The organic resin is an organosilicon - modified phenolic resin; The preparation method of the organosilicon - modified phenolic resin is as follows: Mix phenol, organosilicon resin, and formaldehyde, heat up to 85 - 95°C and stir for 30 - 60 min, add an alkaline catalyst and continue to react for 60 - 120 min, then heat up to 120 - 140°C and distill until no liquid distillate comes out, then cool down to 40 - 50°C, and adjust the viscosity of the obtained pale yellow viscous product with ethanol; The preparation method of the refractory for the hot metal taphole of the above - mentioned high - temperature electric furnace is specifically as follows: Using expanded graphite and Ta as raw materials, after fully grinding and mixing evenly, charge them into a crucible, place the crucible in a self - propagating high - temperature furnace, seal and evacuate, then fill with argon to normal pressure, ignite, grind the obtained product to get the first component, deposit a graphene layer on the surfaces of the magnesite and tabular corundum to get the second component, mix the first component, the second component with calcium chloride, boric acid, antioxidant, and binder evenly, press into shape, first apply pressure to 100 - 120 MPa during pressing, then hold the pressure for 10 - 30 s and then release the pressure, and finally apply pressure again to 100 - 120 MPa. After drying the obtained green body, sinter it at 1400 - 1500°C for 2 - 4 h.

2. The refractory material for the tapping hole of the high-temperature electric furnace according to claim 1, characterized in that, The weight ratio of the expanded graphite to the graphene is 5 - 10: 0.01-1。 3. The refractory material for the tapping hole of the high-temperature electric furnace according to claim 1, characterized in that, The antioxidant is silicon carbide powder and / or aluminum - silicon composite powder.

4. The refractory material for the tapping hole of the high-temperature electric furnace according to claim 1, characterized in that, The alkaline catalyst is sodium hydroxide and / or potassium hydroxide.

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