A chromium-free magnesium-aluminum spinel unburned brick for RH refining furnace and preparation method thereof

Abstract

The invention discloses a chrome-free magnesium aluminum spinel unburned brick for RH refining furnace and a preparation method thereof, belonging to the technical field of metallurgy and refractory materials. The chrome-free magnesium aluminum spinel unburned brick is made of 20-25 parts of 98 ordinary fused magnesia sand with a particle size of 3-5 mm, 25-35 parts of 98 ordinary fused magnesia sand with a particle size of 1-3 mm, 20-25 parts of 98 ordinary fused magnesia sand with a particle size of 0-1 mm, 2-10 parts of 98 ordinary fused magnesia sand with a particle size of ≤0.074 mm, 8-12 parts of sintered aluminum magnesium spinel with a particle size of ≤0.074 mm, 5-8 parts of yttrium oxide stabilized hafnium oxide ceramic binder, 2-3 parts of binder, and is made through the steps of mixing, machine pressing, drying, etc. The present invention avoids the addition of metal aluminum powder, does not generate volume expansion during use, and the yttria-stabilized hafnia ceramic binder forms a hafnia-yttria ceramic structure during use, so that a developed organizational structure is formed inside the chrome-free magnesium-aluminum spinel unfired brick to obtain a dense sintered body. Therefore, the prepared chrome-free magnesium-aluminum spinel unfired brick has excellent slag erosion resistance, thermal shock resistance and high temperature performance.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy and refractory materials, and more particularly to a chromium-free magnesia-alumina spinel unburned brick for RH refining furnace and a preparation method thereof. Background Art

[0002] RH system equipment is a kind of molten steel secondary refining process equipment used to produce high-quality steel. The entire molten steel metallurgical reaction is carried out in a vacuum tank with a refractory lining. In the past few decades, ultra-high temperature fired magnesia-chrome refractory materials have been almost the only refractory materials for RH vacuum smelting equipment linings around the world.

[0003] However, under high temperature and alkaline conditions, Cr 2 O 3 Refractory materials are exposed to oxidizing atmospheres such as Na 2 O.K 2 O or CaO and other strong alkaline oxides coexist, Cr 3+ Can be oxidized to Cr 6+ Cr 6+ It is a carcinogen, harmful to the human body and easily soluble in water; and Cr 2 O 3 It can also exist in gas phase and be discharged into the air with flue gas during production and use, polluting the air environment; in addition, K 2 CrO 4 、CaCrO 4 It is easily soluble in water. Cr in the remaining bricks after use 6+ It will dissolve in rainwater and seep into the ground, causing water pollution. Therefore, in recent years, the development of chrome-free refractory materials has received widespread attention. The chrome-free magnesia-alumina spinel bricks for the lining of RH refining furnaces are basically divided into high-temperature fired bricks and unfired bricks. Magnesia-alumina spinel high-temperature fired bricks are fired refractory products fired at a high temperature of about 1700°C. They have high energy consumption and are restricted by the main raw materials of fused magnesia sand and magnesia-alumina spinel. It is not easy to fully sinter the brick body and obtain a developed organizational structure. Although magnesia-alumina spinel unfired bricks have the advantages of simple process and low energy consumption, they also face the problem that it is difficult for the bricks to form good bonding strength at the use temperature (about 1600-1650°C).

[0004] At present, in order to make the magnesium aluminum spinel unfired brick form good brick sintering strength at the use temperature (about 1600-1650℃), a certain amount of metal aluminum powder is added, such as patent CN111763076A. Although metal aluminum powder forms a liquid phase at 600-800℃, it can promote the sintering of bricks. However, the addition of aluminum powder has the following disadvantages: 1. Metal aluminum powder is flammable and explosive during the mixing process, which is dangerous. 2. Metal aluminum is an active metal, which is easily oxidized at high temperature to form Al 2 O 3, this Al 2 O 3 It has high fineness and high activity. It will react with MgO in the brick to form magnesia-alumina spinel. The process is accompanied by a volume expansion of about 7%, causing a loose structure, reducing the volume density of the unfired brick, increasing the porosity, and making it difficult to obtain a sintered body with good strength and density. When the RH refining furnace is refining molten steel, the molten steel circulation scouring, slag erosion, and sudden temperature changes will cause the damage of refractory bricks, resulting in the unfired bricks being offline at a young age.

[0005] Therefore, providing a chromium-free magnesium-aluminum spinel unfired brick without adding metallic aluminum powder and having excellent resistance to slag erosion, thermal shock resistance and high temperature performance and a preparation method thereof is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of the above, the object of the present invention is to provide a chromium-free magnesia-alumina spinel unfired brick for RH refining furnace containing yttria-stabilized hafnia ceramic binder and a preparation method thereof, which will not undergo volume expansion at the use temperature (about 1600-1650°C), and can form a hafnium oxide-yttria oxide ceramic structure inside, and has the characteristics of excellent resistance to slag erosion, excellent thermal shock resistance and excellent high temperature performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The invention discloses a chrome-free magnesium-aluminum spinel unburned brick for an RH refining furnace, which is prepared from the following raw materials in parts by mass: 20-25 parts of 98% common fused magnesia sand with a particle size of 3-5 mm, 25-35 parts of 98% common fused magnesia sand with a particle size of 1-3 mm, 20-25 parts of 98% common fused magnesia sand with a particle size of 0-1 mm, 2-10 parts of 98% common fused magnesia sand with a particle size of ≤0.074 mm, 8-12 parts of sintered aluminum-magnesium spinel with a particle size of ≤0.074 mm, 5-8 parts of yttria-stabilized hafnium oxide ceramic binder, and 2-3 parts of a binder.

[0009] The beneficial effect is that the present invention replaces the metal aluminum powder with the yttrium oxide stabilized hafnium oxide ceramic binder, which is not only safer in production, but also does not cause the reaction of the molten oxidized metal aluminum powder with MgO in the brick blank during high-temperature use, thereby not causing 7% volume expansion, not causing the volume density of the unfired brick to decrease, and the apparent porosity to increase, and molten steel and steel slag are not easy to penetrate and corrode the magnesium-aluminum spinel brick along the pore channel. Moreover, due to the use of the yttrium oxide stabilized hafnium oxide ceramic binder, the prepared magnesium-aluminum spinel brick will produce ceramic bonding when used at high temperature, and the permanent line of the brick blank at 1550℃*3h changes very little, and the brick blank has good volume density and apparent porosity. At the same time, the yttrium oxide stabilized hafnium oxide ceramic binder can also block the penetration and erosion channels of the molten steel and steel slag of the brick blank, thereby improving the RH chrome-free magnesium spinel brick's resistance to penetration and erosion of molten steel and steel slag.

[0010] The yttria-stabilized hafnium oxide ceramic binder comprises yttria powder and hafnium oxide powder; the mass ratio of the yttria powder to the hafnium oxide powder is 10-20:80-90.

[0011] The yttria-stabilized hafnium oxide ceramic binder also includes aluminum oxide powder; the mass ratio of the aluminum oxide powder, yttria powder and hafnium oxide powder is 5-15:10-15:75-80.

[0012] The preparation method of the yttria-stabilized hafnium oxide ceramic binder is as follows: raw materials are put into an alumina-lined ball mill according to a certain proportion, and dry-milled for 5 to 8 hours.

[0013] Its beneficial effects are: the yttria-stabilized hafnium oxide ceramic binder will form a hafnium oxide-yttria ceramic structure during use, and the alumina powder, as a sintering agent for the yttria-stabilized hafnium oxide, will enhance the activity of yttria and hafnium oxide, promote the formation of the hafnium oxide-yttria ceramic structure, and form a developed organizational structure in the RH chrome-free magnesium-aluminum spinel unfired brick to obtain a dense sintered body. The high-temperature thermal strength of the RH chrome-free magnesium-aluminum spinel brick is increased, thereby improving the RH chrome-free magnesium-aluminum spinel brick's resistance to molten steel scouring and thermal shock stability under sudden temperature changes.

[0014] The binder is liquid phenolic resin.

[0015] The present invention also aims to provide a method for preparing chromium-free magnesia-alumina spinel unburned bricks for RH refining furnace, and the preparation method is as follows:

[0016] According to the mass proportion, 98 ordinary fused magnesia with a particle size of 3-5mm, 98 ordinary fused magnesia with a particle size of 1-3mm, 98 ordinary fused magnesia with a particle size of 0-1mm, 98 ordinary fused magnesia with a particle size ≤0.074mm, sintered alumina-magnesia spinel with a particle size ≤0.074mm, and yttria-stabilized hafnium oxide ceramic binder are weighed, mixed, and put into a planetary high-speed mixer for low-speed mixing; then the binder is added and high-speed mixing is performed to obtain mud; the obtained mud is formed by machine pressure and dried to obtain the chromium-free magnesia-alumina spinel unfired brick.

[0017] The low-speed mixing speed is 60 rpm, the time is 3 to 6 minutes; the high-speed mixing speed is 120 rpm, the time is 20 to 30 minutes, and the temperature is 40 to 55°C.

[0018] The molding pressure of the machine pressing is 850-1500 KN, and the pressing is performed 7-10 times. The obtained brick has a compressive strength of 100-105 MPa and a bulk density of 3.18-3.20 g / cm 3 .

[0019] The drying temperature is 180-200° C., and the drying time is 10-12 hours.

[0020] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a chromium-free magnesia-alumina spinel unburned brick for RH refining furnace and a preparation method thereof, which produces the following beneficial effects through the use of yttrium oxide stabilized hafnium oxide ceramic binder:

[0021] (1) The present invention replaces the metal aluminum powder in the raw material of the chrome-free magnesium aluminum spinel unfired brick in the prior art with a yttria-stabilized hafnium oxide ceramic binder, thereby avoiding the volume expansion caused by the metal aluminum powder, increasing the volume density, reducing the porosity, and closing the penetration and erosion channels of molten steel and steel slag. At the same time, yttria-stabilized hafnium oxide forms a hafnium oxide-yttria oxide ceramic structure, so that a developed organizational structure is formed in the chrome-free magnesium aluminum spinel unfired brick, a dense sintered body is obtained, and the high-temperature thermal strength of the RH chrome-free magnesium aluminum spinel unfired brick is increased, thereby improving its resistance to molten steel scouring and thermal shock stability under temperature changes.

[0022] (2) During use, yttrium oxide and hafnium oxide react with the infiltrated slag to generate a complex high-temperature phase, which inhibits the reaction penetration of the slag. In addition, due to the absorption of CaO in the slag, the alkalinity of the slag is reduced, the viscosity of the slag is increased, and the wetting angle between the slag and the brick body is increased, thereby increasing the viscous flow resistance of the slag penetration, inhibiting the penetration of the slag, thereby improving the RH chrome-free magnesia-alumina spinel brick's resistance to slag erosion and penetration.

[0023] (3) The chrome-free magnesium-aluminum spinel unfired brick of the present invention has excellent resistance to slag erosion, excellent thermal shock resistance, and excellent high-temperature performance. Its 1600°C static crucible method slag resistance test erosion index is 3% to 8%, and its permeability index is 5 to 10%; its flexural strength in the hot state at 1600°C*30min is 25 to 38Mpa; its residual compressive strength after 10 times of air rapid cooling at 1100°C*20min is 65 to 85Mpa; and its permanent linear change after heating at 1550°C*3h is 0.2% to 0.45%.

[0024] (4) The chromium-free magnesium-aluminum spinel unfired bricks prepared by the present invention have a long average lifespan in practical applications, can improve the utilization rate of the RH refining furnace, and reduce the average cost. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The embodiment of the present invention discloses a chromium-free magnesium-aluminum spinel unburned brick for RH refining furnace and a preparation method thereof. The raw material requirements are as follows:

[0027] Among them, 98 ordinary fused magnesia of all particle sizes requires MgO content> 98%, SiO 2 Content <1.0%, the rest is impurities. 2 O 3 The content is 76% to 78%, the MgO content is 18% to 22%, and the remainder is impurities. The binder is liquid phenolic resin, and the requirements are residual carbon value ≥ 40%, moisture ≤ 3.0%, and viscosity 16000cp to 19000cp. The purity of alumina powder is > 99%, and the particle size is 2 to 3μm; the purity of yttrium oxide powder is > 99%, and the particle size is 45μm; the purity of hafnium oxide powder is > 99%, and the particle size is 45μm. Metal aluminum powder with a particle size of ≤ 0.074mm requires a purity of ≥ 98%.

[0028] Example 1

[0029] Alumina powder, yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 5:15:80. After the materials were dry-milled in the ball mill for 6 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0030] Take 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 6.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 5 parts of yttria-stabilized hafnium oxide ceramic binder by mass, mix them, put them into a planetary high-speed mixer, and mix them at a speed of 60rpm for 5min; then add 2.5 parts of binder, mix them at a speed of 120rpm for 25min, and the temperature is 40℃ to obtain mud; take the obtained mud and form it under high pressure through an electric hydraulic brick press, the forming pressure is 850KN, and it is pressed 10 times, and the obtained brick has a compressive strength of 100Mpa and a volume density of 3.18g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0031] Example 2

[0032] Alumina powder, yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 5:15:80. After the materials were dry-milled in the ball mill for 6 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0033] Take 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 3.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 8 parts of yttria-stabilized hafnium oxide ceramic binder by mass, mix them, put them into a planetary high-speed mixer, and mix them at a speed of 60rpm for 5min; then add 2.5 parts of binder, mix them at a speed of 120rpm for 25min, and the temperature is 55℃ to obtain mud; take the obtained mud and high-pressure mold it through an electric hydraulic brick press, the molding pressure is 1500KN, and it is pressed 7 times. The obtained brick has a compressive strength of 105Mpa and a bulk density of 3.20g / cm 3 . Drying in a drying kiln at 200°C for 10 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0034] Example 3

[0035] Alumina powder, yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 5:15:80. After the materials were dry-milled in the ball mill for 5 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0036] Take 20 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 35 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 20 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 6.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 6 parts of yttria-stabilized hafnium oxide ceramic binder by mass, mix them, put them into a planetary high-speed mixer, and mix them at a speed of 60rpm for 5min; then add 2.5 parts of binder, mix them at a speed of 120rpm for 25min, and the temperature is 50℃ to obtain mud; take the obtained mud and high-pressure mold it through an electric hydraulic brick press, the molding pressure is 1000KN, and it is pressed 7 times. The obtained brick has a compressive strength of 103Mpa and a bulk density of 3.19g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0037] Example 4

[0038] Alumina powder, yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 5:15:80. After the materials were dry-milled in the ball mill for 8 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0039] According to the mass proportion, 25 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 25 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 25 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 5.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 7 parts of yttria-stabilized hafnium oxide ceramic binder were mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of the binder were added, and mixed at a speed of 120rpm for 25min, at a temperature of 45°C, to obtain mud; the obtained mud was taken and high-pressure formed by an electric hydraulic brick press, the forming pressure was 900KN, and it was pressed 10 times, and the obtained brick had a compressive strength of 101Mpa and a bulk density of 3.19g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0040] Example 5

[0041] Alumina micropowder, yttrium oxide powder and hafnium oxide powder are put into an alumina-lined ball mill in a mass ratio of 10:15:75. After the materials are dry-milled in the ball mill for 7 hours, yttrium oxide-stabilized hafnium oxide ceramic binder is obtained.

[0042] According to the mass proportion, 25 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 25 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 25 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 5.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 7 parts of yttria-stabilized hafnium oxide ceramic binder are mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of binder are added, and mixed at a speed of 120rpm for 25min, and the temperature is 45°C to obtain mud; the obtained mud is taken and high-pressure molded by an electric hydraulic brick press, the molding pressure is 900KN, and it is pressed 10 times, and the obtained brick has a compressive strength of 102Mpa and a volume density of 3.19g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0043] Example 6

[0044] Alumina powder, yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 15:10:75. After the materials were dry-milled in the ball mill for 6 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0045] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 3.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 8 parts of yttria-stabilized hafnium oxide ceramic binder were mixed and put into a planetary high-speed mixer and mixed at a speed of 60rpm for 5min; then 2.5 parts of binder were added, mixed at a speed of 120rpm for 25min, and the temperature was 55°C to obtain mud; the obtained mud was taken and high-pressure formed by an electric hydraulic brick press, the forming pressure was 1500KN, and it was pressed 7 times, and the obtained brick had a compressive strength of 104Mpa and a bulk density of 3.20g / cm 3 . Drying in a drying kiln at 200°C for 10 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0046] Example 7

[0047] Yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 20:80. After the materials were dry-milled in the ball mill for 6 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0048] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 6.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 5 parts of yttria-stabilized hafnium oxide ceramic binder were mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of binder were added, and mixed at a speed of 120rpm for 25min, at a temperature of 45°C, to obtain mud; the obtained mud was taken and high-pressure formed by an electric hydraulic brick press, with a forming pressure of 850KN, and pressed 10 times, and the obtained brick had a compressive strength of 100Mpa and a volume density of 3.18g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0049] Example 8

[0050] Yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 10:90. After the materials were dry-milled in the ball mill for 7 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0051] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 6.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 5 parts of yttria-stabilized hafnium oxide ceramic binder were mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of binder were added, and mixed at a speed of 120rpm for 25min, and the temperature was 45°C to obtain mud; the obtained mud was taken and high-pressure formed by an electric hydraulic brick press, the forming pressure was 950KN, and it was pressed 10 times, and the obtained brick had a compressive strength of 102Mpa and a volume density of 3.19g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0052] Example 9

[0053] Yttrium oxide powder and hafnium oxide powder were put into an alumina-lined ball mill in a mass ratio of 15:85. After the materials were dry-milled in the ball mill for 6 hours, yttrium oxide-stabilized hafnium oxide ceramic binder was obtained.

[0054] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 6.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 5 parts of yttria-stabilized hafnium oxide ceramic binder were mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of binder were added, and mixed at a speed of 120rpm for 25min, at a temperature of 45°C, to obtain mud; the obtained mud was taken and high-pressure formed by an electric hydraulic brick press, the forming pressure was 1000KN, and it was pressed 7 times, and the obtained brick had a compressive strength of 103Mpa and a bulk density of 3.19g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0055] In order to better reflect the excellent performance of the present application, a comparative example is set up, and the raw material requirements in the comparative example are the same as those in the embodiment.

[0056] Comparative Example 1

[0057] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 9.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 2 parts of metal aluminum powder with a particle size ≤0.074mm were mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of a binder were added, and mixed at a speed of 120rpm for 25min at a temperature of 40°C to obtain a mud material; the obtained mud material was taken and formed by high pressure through an electric hydraulic brick press, with a forming pressure of 850KN, and pressed 10 times, and the obtained brick had a compressive strength of 99Mpa and a bulk density of 3.18g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0058] Comparative Example 2

[0059] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 7.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 4 parts of metal aluminum powder with a particle size ≤0.074mm were mixed and put into a planetary high-speed mixer and mixed at a speed of 60rpm for 5min; then 2.5 parts of a binder were added, mixed at a speed of 120rpm for 25min, and the temperature was 55°C to obtain a mud material; the obtained mud material was taken and high-pressure formed by an electric hydraulic brick press, the forming pressure was 1500KN, and it was pressed 7 times, and the obtained brick had a compressive strength of 104Mpa and a bulk density of 3.19g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0060] Comparative Example 3

[0061] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 6.5 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, 10 parts of sintered aluminum magnesium spinel with a particle size ≤0.074mm, and 5 parts of metal aluminum powder with a particle size ≤0.074mm were mixed and put into a planetary high-speed mixer, and mixed at a speed of 60rpm for 5min; then 2.5 parts of a binder were added, and mixed at a speed of 120rpm for 25min at a temperature of 40°C to obtain a mud material; the obtained mud material was taken and high-pressure formed by an electric hydraulic brick press, the forming pressure was 900KN, and it was pressed 10 times, and the obtained brick had a compressive strength of 101Mpa and a volume density of 3.18g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0062] Comparative Example 4

[0063] According to the mass proportion, 23 parts of 98 ordinary fused magnesia with a particle size of 3-5mm, 30 parts of 98 ordinary fused magnesia with a particle size of 1-3mm, 23 parts of 98 ordinary fused magnesia with a particle size of 0-1mm, 10 parts of 98 ordinary fused magnesia with a particle size ≤0.074mm, and 11.5 parts of sintered alumina-magnesium spinel with a particle size ≤0.074mm were mixed and put into a planetary high-speed mixer and mixed at a speed of 60rpm for 5min; then 2.5 parts of a binder were added, mixed at a speed of 120rpm for 25min, and the temperature was 40°C to obtain a mud material; the obtained mud material was taken and high-pressure molded by an electric hydraulic brick press, the molding pressure was 1000KN, and it was pressed 10 times, and the obtained brick had a compressive strength of 104Mpa and a bulk density of 3.20g / cm 3 . Drying in a drying kiln at 180°C for 12 hours will give chromium-free magnesium-aluminum spinel unfired bricks.

[0064] Performance test:

[0065] The hot flexural strength (Mpa) test was carried out according to GB / T 3002-2004, the slag erosion resistance test was carried out according to GB / T 8931-2007, the thermal shock performance test was carried out according to YB / T 376.1-1995, the compressive strength test was carried out according to GB / T5072-2008, and the permanent linear change test after heating at 1550℃*3h was carried out according to GB / T 5988-2007. The test results are shown in Tables 1 and 2.

[0066] Table 1 Test data of chromium-free magnesium-aluminum spinel unburned bricks for finished products of RH refining furnace in Examples 1-9

[0067]

[0068] Table 2 Comparative Examples 1-4 Finished RH Refining Furnace Chrome-free Magnesium Aluminum Spinel Unburned Brick Test Data

[0069]

[0070]

[0071] By comparing the data in Table 1 and Table 2, it can be seen that the chrome-free magnesium aluminum spinel unfired brick without adding metal aluminum powder is not easy to sinter, and its slag erosion resistance and permeability, thermal shock resistance and high temperature performance are relatively poor. After adding metal aluminum powder, its slag erosion resistance and permeability, thermal shock resistance and high temperature performance are improved, but its 1550℃*3h permanent line change rate increases, indicating that it will have a large volume expansion during use. After replacing the metal aluminum powder with yttria-stabilized hafnium oxide ceramic binder, its slag erosion resistance and permeability, thermal shock resistance and high temperature performance are further improved, and the 1550℃*3h heating permanent line change has a significant decrease, even lower than the group without adding metal aluminum powder. The reason is that the use of yttria-stabilized hafnium oxide ceramic binder avoids the volume expansion caused by metal aluminum powder, increases the volume density, reduces the porosity, and closes the penetration and erosion channels of molten steel and steel slag. At the same time, yttrium oxide stabilizes hafnium oxide to form a hafnium oxide-yttrium oxide ceramic structure, so that a developed organizational structure is formed in the chrome-free magnesium aluminum spinel unfired brick, and a dense sintered body is obtained, which increases the high-temperature thermal strength of the RH chrome-free magnesium aluminum spinel unfired brick, thereby improving its resistance to molten steel scouring and thermal shock stability under sudden temperature changes. In addition, the performance of the yttrium oxide stabilized hafnium oxide ceramic binder raw material will be further improved after adding alumina powder, because alumina powder, as a sintering agent for yttrium oxide stabilized hafnium oxide, can improve the activity of yttrium oxide and hafnium oxide.

[0072] Practical application experiment:

[0073] RH chromium-free magnesia-alumina spinel unburned bricks were prepared according to the raw material ratios in the above Example 2 and applied to a 180-ton RH refining furnace of a branch of Anshan Iron and Steel Company for testing.

[0074] The specific steps are as follows:

[0075] Masonry: Lay the RH chrome-free magnesium-aluminum spinel unburned bricks in the lower trough of the RH refining furnace according to the number of layers and positions required by the design drawings. Place a 1mm yellow paperboard in the vertical joints of every 10 bricks of the RH chrome-free magnesium-aluminum spinel bricks for the wall;

[0076] Baking: According to the flame length of baking in steel plant, it is divided into low fire 24 hours, medium fire 24 hours and high fire 24 hours, and it can be put into use after a total of 72 hours.

[0077] The high-performance chrome-free magnesium-aluminum spinel unfired brick for RH refining furnace prepared in this embodiment is actually used in the lower tank of a 180-ton RH refining furnace of a branch of Anshan Iron and Steel Co., Ltd., and the average service life is 380 times. The average service life of the chrome-free magnesium-aluminum spinel unfired brick for RH refining furnace in the prior art is 320 times, and the service life of the chrome-free magnesium-aluminum spinel unfired brick for RH refining furnace of the present invention is significantly higher than that of the prior art.

[0078] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A chromium-free magnesia-alumina spinel unburned brick for RH refining furnace, It is characterized in that The invention is prepared from the following raw materials in parts by mass: 20-25 parts of 98% common fused magnesia with a particle size of 3-5 mm, 25-35 parts of 98% common fused magnesia with a particle size of 1-3 mm, 20-25 parts of 98% common fused magnesia with a particle size of 0-1 mm, 2-10 parts of 98% common fused magnesia with a particle size of ≤0.074 mm, 8-12 parts of sintered aluminum magnesium spinel with a particle size of ≤0.074 mm, 5-8 parts of yttria-stabilized hafnium oxide ceramic binder, and 2-3 parts of binder; The raw materials of the yttria-stabilized hafnium oxide ceramic binder are aluminum oxide micropowder, yttria powder and hafnium oxide powder, and the mass ratio is 5-15:10-15:75-80; The preparation method of the yttrium oxide-stabilized hafnium oxide ceramic binder is as follows: the raw materials of the yttrium oxide-stabilized hafnium oxide ceramic binder are put into an alumina-lined ball mill according to a certain proportion, and dry-milled for 5 to 8 hours.

2. The chromium-free magnesia-alumina spinel unburned brick for RH refining furnace according to claim 1, It is characterized in that The 98 ordinary fused magnesia sands of different particle sizes are required to have a MgO content of >98%, SiO 2 Content <1.0%, the remainder is impurities; the Al in the sintered aluminum magnesium spinel 2 O 3 The content is 76%~78%, the MgO content is 18%~22%, and the rest is impurities.

3. The chromium-free magnesia-alumina spinel unburned brick for RH refining furnace according to claim 1, It is characterized in that The binder is liquid phenolic resin.

4. A method for preparing the chromium-free magnesia-alumina spinel unburned brick for RH refining furnace according to claim 1, It is characterized in that The preparation method is as follows: Weigh 98% common fused magnesia with a particle size of 3-5 mm, 98% common fused magnesia with a particle size of 1-3 mm, 98% common fused magnesia with a particle size of 0-1 mm, 98% common fused magnesia with a particle size of ≤0.074 mm, sintered alumina-magnesia spinel with a particle size of ≤0.074 mm, and yttria-stabilized hafnium oxide ceramic binder, mix them, and then knead them at a low speed; after the low-speed kneading is completed, the binder is added and kneaded at a high speed to obtain mud; the obtained mud is formed by machine pressing and dried to obtain the chromium-free magnesia-alumina spinel unfired brick.

5. The method for preparing the chromium-free magnesia-alumina spinel unburned brick for RH refining furnace according to claim 4, It is characterized in that The low-speed mixing speed is 60 rpm, the time is 3-6 min; the high-speed mixing speed is 120 rpm, the time is 20-30 min, and the temperature is 40-55°C.

6. The method for preparing the chromium-free magnesia-alumina spinel unburned brick for RH refining furnace according to claim 4, It is characterized in that The molding pressure of the machine compression molding is 850-1500 KN, and the compression is performed 7-10 times.

7. The method for preparing the chromium-free magnesia-alumina spinel unburned brick for RH refining furnace according to claim 4, It is characterized in that The drying temperature is 180-200° C. and the drying time is 10-12 hours.

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