Magnesium-zirconium coating and preparation method thereof

Abstract

The invention discloses a magnesium-zirconium coating and a preparation method thereof. The magnesium-zirconium coating mainly comprises 54-65% of aggregate, 25-36% of powder, 4-7% of an additive and 1-4% of a binding agent, in addition, an additive accounting for 0.1-1% of the total weight of the raw materials is added; the aggregate 54-65% is composed of 12-18% of waste magnesia-zirconia bricks smaller than or equal to 3 mm, 22-29% of regenerated magnesia smaller than or equal to 3 mm and 20-27% of electric smelting skin sand smaller than or equal to 3 mm; and 25-36% of powder is composed of 13-18% of waste magnesia-zirconia bricks with the particle size being smaller than or equal to 0.037 mm, 8-13% of regenerated magnesia with the particle size being smaller than or equal to 0.088 mm and 2-8% of electric smelting skin sand with the particle size being smaller than or equal to All the raw materials are added into a forced stirrer to be stirred and mixed, then tap water accounting for 5-10% of the total weight of all the raw materials is added, forced stirring continues, and after the coating material is in a paste shape, discharging is conducted for use. The magnesium-zirconium coating prepared by the invention can form good bonding strength with bricks at both low temperature and high temperature, has good erosion resistance, and can completely meet the construction requirements and operation requirements of high-temperature kilns.

Description

I. Technical Field:

[0001] The present invention belongs to the technical field of refractory materials, and particularly relates to a magnesia-zirconia ramming mass for nickel-boron alloy electric arc furnaces and a preparation method thereof. II. Background Art:

[0002] For high-temperature furnaces in non-ferrous metal smelting, such as DC direct current electric arc furnaces for nickel-boron alloy smelting, magnesia-zirconia bricks with good erosion resistance are mostly used as working linings. During the brick laying process, due to the circular structure of the furnace body of the electric arc furnace and the wedge shape of the bricks, the hot surface in contact with the alloy melt after laying will be uneven. Generally, a ramming mass is used for ramming to form a relatively smooth inner wall of the furnace lining. On the one hand, the ramming mass fills the unevenness formed by the brick surface and the gaps between bricks in the furnace, playing a role of "levelling" the inner wall surface of the furnace, making the pouring of the alloy melt more smooth; on the other hand, during the high-temperature smelting process, the ramming mass forms a bonding strength with the bricks outward and a reaction layer with the alloy melt inward, preventing the melt from leaking and eroding outward and improving the service life of the furnace lining. Therefore, the ramming mass has a great impact on the production efficiency and safety of nickel-boron alloys.

[0003] During the long-term use of high-temperature furnaces in non-ferrous metal smelting using magnesia-zirconia bricks as working linings, a large amount of used bricks are generated, which are piled up all year round to form solid waste. Conventional magnesia-zirconia ramming masses have relatively low high-temperature bonding strength. When the high-temperature melt is poured out of the electric arc furnace, the ramming mass is prone to massive spalling and mixing into the alloy, which has a negative impact on the production efficiency and quality of nickel-boron alloys. The spalling of the coating layer will also cause the melt to penetrate into the brick layer, accelerating the erosion of the bricks, and thus greatly reducing the service life of the furnace. III. Summary of the Invention:

[0004] The technical problem to be solved by the present invention is: aiming at the technical problems that due to the relatively low high-temperature bonding strength of the existing magnesia-zirconia ramming mass, when the high-temperature melt is poured out of the electric arc furnace, the ramming mass is prone to massive spalling and mixing into the alloy, which has a negative impact on the production efficiency and quality of nickel-boron alloys, and the spalling of the coating layer will also cause the melt to penetrate into the brick layer, accelerating the erosion of the bricks, and thus greatly reducing the service life of the furnace, etc., the present invention provides a new magnesia-zirconia ramming mass and a preparation method thereof. The technical solution of the present invention uses waste magnesia-zirconia bricks, recycled magnesia sand and fused bauxite as the main raw materials, and adds an appropriate amount of water during construction to prepare a magnesia-zirconia ramming mass. The magnesia-zirconia ramming mass of the product of the present invention can form good bonding strength with bricks at both low and high temperatures, and at the same time has good erosion resistance, and can fully meet the construction requirements and operation requirements of high-temperature furnaces.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is:

[0006] The present invention provides a magnesia - zirconia ramming mix. In terms of mass percentage, the magnesia - zirconia ramming mix mainly consists of 54 - 65% aggregate, 25 - 36% powder, 4 - 7% additive, and 1 - 4% binder; in addition, an admixture accounting for 0.1 - 1% of the total weight of various raw materials is added.

[0007] The 54 - 65% aggregate consists of 12 - 18% waste magnesia - zirconia bricks with a particle size of ≤3 mm, 22 - 29% recycled magnesia sand with a particle size of ≤3 mm, and 20 - 27% fused bauxite sand with a particle size of ≤3 mm.

[0008] The 25 - 36% powder consists of 13 - 18% waste magnesia - zirconia bricks with a particle size of ≤0.037 mm, 8 - 13% recycled magnesia sand with a particle size of ≤0.088 mm, and 2 - 8% fused bauxite sand with a particle size of ≤0.088 mm.

[0009] For the above - mentioned magnesia - zirconia ramming mix, the waste magnesia - zirconia bricks have a MgO content of ≥70% and a ZrO2 + HfO2 content of ≥11%; the waste magnesia - zirconia bricks are directly crushed from used - recycled magnesia - zirconia bricks into waste magnesia - zirconia bricks with a particle size of ≤3 mm and waste magnesia - zirconia bricks with a particle size of ≤0.037 mm.

[0010] For the above - mentioned magnesia - zirconia ramming mix, the recycled magnesia sand has a MgO content of ≥95%, a SiO2 content of ≤2%, an Fe2O3 content of ≤1.5%, and a CaO content of ≤2%; the recycled magnesia sand is obtained by successively classifying and sorting, removing the working layer, crushing, soaking and cleaning, drying, cooling, secondary crushing, and screening of used - recycled magnesia bricks, to obtain recycled magnesia sand with a particle size of ≤3 mm and recycled magnesia sand with a particle size of ≤0.088 mm.

[0011] For the above - mentioned magnesia - zirconia ramming mix, the fused bauxite sand has a MgO content of ≥96%, a SiO2 content of ≤0.7%, an Fe2O3 content of ≤1.0%, and a CaO content of ≤2.5%.

[0012] For the above - mentioned magnesia - zirconia ramming mix, the additive consists of silica fume, nano - silica fume, and Guangxi white clay.

[0013] For the above - mentioned magnesia - zirconia ramming mix, the mass ratio of silica fume, nano - silica fume, and Guangxi white clay is 1 - 2:1 - 2:2 - 3.

[0014] For the above - mentioned magnesia - zirconia ramming mix, the binder consists of sodium tripolyphosphate, sodium hexametaphosphate, industrial glucose, carboxymethyl cellulose, and dextrin.

[0015] For the above - mentioned magnesia - zirconia ramming mix, the mass ratio of sodium tripolyphosphate, sodium hexametaphosphate, industrial glucose, carboxymethyl cellulose, and dextrin is 5 - 7:5 - 7:8 - 12:3 - 7:3 - 7.

[0016] According to the above-mentioned magnesia-zirconia ramming mix, the admixture is an explosion-proof fiber composed of polyethylene, polypropylene and polyester fiber (the mixing mass ratio between the polyethylene, polypropylene and polyester fiber is 2:1:1).

[0017] In addition, a preparation method of magnesia-zirconia ramming mix is provided. The preparation method includes the following steps:

[0018] a. Weigh various raw materials according to the proportion of the above-mentioned magnesia-zirconia ramming mix;

[0019] b. Add the weighed aggregate, powder, additive, binder and admixture into a forced mixer for mixing, stir and mix for 5 - 10 minutes, then add tap water accounting for 5 - 10% of the total weight of various raw materials, and continue to forcefully stir for 5 - 8 minutes. Wait until the ramming mix becomes a mud paste and discharge it for standby.

[0020] The positive and beneficial effects of the present invention:

[0021] 1. By preparing the magnesia-zirconia ramming mix through the technical solution of the present invention, the high-temperature bonding strength of the ramming mix can be effectively improved, preventing blocky shedding. At the same time, it has good erosion resistance, can protect refractory bricks and extend the service life of the kiln.

[0022] 2. The technical solution of the present invention uses waste magnesia-zirconia bricks, recycled magnesia sand and fused crust sand as the main raw materials, realizing the recycling of waste resources, turning waste into treasure, reducing resource consumption and carbon emissions in the raw material preparation process, reducing environmental pollution, and being beneficial to environmental protection.

[0023] 3. By using the technical solution of the present invention to prepare the magnesia-zirconia ramming mix, the production cost is reduced, the economic benefit of the enterprise is improved, and it has a broad market application prospect.

[0024] 4. It can be proved by the test results of the prepared magnesia-zirconia ramming mix in the examples that the flexural strength in the test reflects the bonding performance at different temperatures. The greater the strength, the stronger the bonding between the ramming layer and the brick. At low temperatures such as 110°C and 600°C, the strength is close, mainly relying on the bonding effect of the binder. The strength at high temperatures is improved because the ramming mix of the present invention and the brick form good sintering strength at high temperatures. The improvement in performance of the magnesia-zirconia ramming mix prepared by the present invention is mainly reflected in the obvious improvement of the bonding strength between the ramming mix and the brick at high temperatures, avoiding the physical exfoliation that may occur in the ramming layer under the scouring of the melt.

[0025] In summary, the present invention has remarkable economic and social benefits. IV. Specific implementation manners:

[0026] The following further elaborates the present invention in combination with examples, but does not limit the scope of protection of the technical solution of the present invention.

[0027] In the following examples, the waste magnesia-zirconia bricks used have a MgO content of ≥ 70% and a ZrO2 + HfO2 content of ≥ 11%. The waste magnesia-zirconia bricks are directly crushed from recycled used magnesia-zirconia bricks into waste magnesia-zirconia bricks with a particle size of ≤ 3 mm and waste magnesia-zirconia bricks of ≤ 0.037 mm. The recycled magnesia sand has a MgO content of ≥ 95%, a SiO2 content of ≤ 2%, an Fe2O3 content of ≤ 1.5%, and a CaO content of ≤ 2%. The recycled magnesia sand is obtained by successively classifying and sorting, removing the working layer, crushing, soaking and cleaning, drying, cooling, secondary crushing, and screening of recycled magnesia bricks used, to obtain recycled magnesia sand of ≤ 3 mm and recycled magnesia sand of ≤ 0.088 mm. The fused skin sand has a MgO content of ≥ 96%, a SiO2 content of ≤ 0.7%, an Fe2O3 content of ≤ 1.0%, and a CaO content of ≤ 2.5%.

[0028] Example 1:

[0029] The magnesia-zirconia ramming mix of the present invention, expressed in mass percentage, is composed of 58% aggregate, 34% powder, 5% additive, and 3% binder; in addition, an admixture accounting for 0.15% of the total weight of various raw materials is added;

[0030] The 58% aggregate is composed of 15% waste magnesia-zirconia bricks of ≤ 3 mm, 23% recycled magnesia sand of ≤ 3 mm, and 20% fused skin sand of ≤ 3 mm;

[0031] The 34% powder is composed of 14% waste magnesia-zirconia bricks of ≤ 0.037 mm, 12% recycled magnesia sand of ≤ 0.088 mm, and 8% fused skin sand of ≤ 0.088 mm.

[0032] Expressed in mass percentage, the 5% additive is composed of 1% silica fume, 1% nano-silica fume, and 3% Guangxi white clay; the 3% binder is composed of 0.5% sodium tripolyphosphate, 0.5% sodium hexametaphosphate, 1% industrial glucose, 0.3% carboxymethyl cellulose, and 0.7% dextrin; the admixture is an explosion-proof fiber formed by mixing polyethylene, polypropylene, and polyester fiber (the mixing mass ratio between polyethylene, polypropylene, and polyester fiber is 2:1:1).

[0033] The preparation method of the magnesia-zirconia ramming mix of Example 1 of the present invention is as follows in detail:

[0034] a. Weigh various raw materials according to the mixing ratio of the magnesia-zirconia ramming mix described in Example 1;

[0035] b. Add the weighed aggregate, powder, additive, binder, and admixture into a forced mixer for mixing. Stir and mix for 8 minutes, then add tap water accounting for 7% of the total weight of various raw materials, and continue forced stirring for 6 minutes. Wait until the ramming mix becomes a mud paste and discharge it for standby.

[0036] The prepared daub is subjected to daub construction operation, and then the daub is sampled for testing: the bulk density after drying at 110°C for 24 hours is 2.30 g / cm 3 , the bulk density after heat treatment at 600°C for 3 hours is 2.39 g / cm 3 , the bulk density after heat treatment at 1200°C for 3 hours is 2.43 g / cm 3 ; the bulk density after heat treatment at 1400°C for 3 hours is 2.50 g / cm 3 .

[0037] The magnesia-zirconia brick is cut into specimens of 40×40×60 mm. The daub prepared in Example 1 is used to bond the brick specimens, and the flexural strength of the bonded specimens is measured after heat treatment at the corresponding temperature. The flexural strength after drying at 110°C for 24 hours is 2.1 MPa; the flexural strength after heat treatment at 600°C for 3 hours is 1.5 MPa; the flexural strength after heat treatment at 1200°C for 3 hours is 3.4 MPa; the flexural strength after heat treatment at 1400°C for 3 hours is 5.1 MPa.

[0038] Example 2:

[0039] The magnesia-zirconia daub of the present invention is composed of 60% aggregate, 32% powder, 4.8% additive and 3.2% binder in terms of mass percentage; in addition, an admixture accounting for 0.2% of the total weight of various raw materials is added;

[0040] The 60% aggregate consists of 16% waste magnesia-zirconia brick with a size of ≤3 mm, 24% recycled magnesia sand with a size of ≤3 mm and 20% fused bauxite sand with a size of ≤3 mm;

[0041] The 32% powder consists of 15% waste magnesia-zirconia brick with a size of ≤0.037 mm, 12% recycled magnesia sand with a size of ≤0.088 mm and 5% fused bauxite sand with a size of ≤0.088 mm.

[0042] In terms of mass percentage, the 4.8% additive consists of 1.3% silica fume, 1.3% nano-silica fume and 2.2% Guangxi white clay; the 3.2% binder consists of 0.5% sodium tripolyphosphate, 0.7% sodium hexametaphosphate, 1% industrial glucose, 0.7% carboxymethyl cellulose and 0.3% dextrin; the admixture is an explosion-proof fiber composed of a mixture of polyethylene, polypropylene and polyester fiber (the mixing mass ratio between polyethylene, polypropylene and polyester fiber is 2:1:1).

[0043] The preparation method of the magnesia-zirconia daub in Example 2 of the present invention is the same as that in Example 1.

[0044] The daub prepared in Example 2 is subjected to daub construction operation, and then the daub is sampled for testing: the bulk density after drying at 110°C for 24 hours is 2.34 g / cm 3, the bulk density is 2.38 g / cm³ after heat treatment at 600 °C for 3 h 3 , the bulk density is 2.46 g / cm³ after heat treatment at 1200 °C for 3 h 3 ; the bulk density is 2.53 g / cm³ after heat treatment at 1400 °C for 3 h 3 .

[0045] The magnesia-zirconia brick was cut into specimens of 40×40×60 mm. The coating material prepared in Example 2 was used to bond the brick specimens, and the flexural strength of the bonded specimens was measured after heat treatment at the corresponding temperature. The flexural strength was 2.3 MPa after drying at 110 °C for 24 h; 1.8 MPa after heat treatment at 600 °C for 3 h; 4.4 MPa after heat treatment at 1200 °C for 3 h; 5.9 MPa after heat treatment at 1400 °C for 3 h.

[0046] Example 3:

[0047] The magnesia-zirconia coating material of the present invention is composed of 62% aggregate, 30% powder, 4.6% additive and 3.4% binder by mass percentage; in addition, an admixture accounting for 0.3% of the total weight of various raw materials is added;

[0048] The 62% aggregate consists of 17% waste magnesia-zirconia brick with a size of ≤3 mm, 25% recycled magnesia sand with a size of ≤3 mm and 20% fused bauxite sand with a size of ≤3 mm;

[0049] The 30% powder consists of 16% waste magnesia-zirconia brick with a size of ≤0.037 mm, 12% recycled magnesia sand with a size of ≤0.088 mm and 2% fused bauxite sand with a size of ≤0.088 mm.

[0050] The 4.6% additive consists of 1.0% silica fume, 1.6% nano-silica fume and 2.0% Guangxi white clay by mass percentage; the 3.4% binder consists of 0.7% sodium tripolyphosphate, 0.7% sodium hexametaphosphate, 1% industrial glucose, 0.5% carboxymethyl cellulose and 0.5% dextrin; the admixture is an explosion-proof fiber composed of polyethylene, polypropylene and polyester fiber (the mixing mass ratio between polyethylene, polypropylene and polyester fiber is 2:1:1).

[0051] The preparation method of the magnesia-zirconia coating material in Example 3 of the present invention is the same as that in Example 1.

[0052] The coating material prepared in Example 3 was subjected to coating construction operation, and then the coating material was sampled for testing: the bulk density was 2.36 g / cm³ after drying at 110 °C for 24 h 3 , the bulk density is 2.43 g / cm³ after heat treatment at 600 °C for 3 h 3 , the bulk density is 2.49 g / cm³ after heat treatment at 1200 °C for 3 h 3; The bulk density after heat treatment at 1400°C for 3 hours is 2.53 g / cm 3 .

[0053] The magnesia-zirconia brick was cut into specimens of 40×40×60 mm. The brick specimens were bonded with the coating material, and the flexural strength of the bonded specimens was measured after heat treatment at the corresponding temperature. The flexural strength after drying at 110°C for 24 hours was 2.9 MPa; the flexural strength after heat treatment at 600°C for 3 hours was 1.6 MPa; the flexural strength after heat treatment at 1200°C for 3 hours was 4.1 MPa; the flexural strength after heat treatment at 1400°C for 3 hours was 5.5 MPa.

[0054] Comparative example:

[0055] A magnesia-zirconia coating material, expressed in mass percentage, consists of 60% aggregate, 32% powder, 5% additive, and 3% binder; in addition, an admixture accounting for 0.2% of the total weight of the four raw materials was added.

[0056] The 60% aggregate consists of 40% high-purity magnesia sand with a particle size of ≤3 mm and 20% fused magnesia sand with a particle size of ≤3 mm;

[0057] The 32% powder consists of 12% high-purity magnesia sand with a particle size of ≤0.088 mm, 10% fused magnesia sand with a particle size of ≤0.088 mm, and 10% magnesia-zirconia powder with a particle size of ≤0.037 mm;

[0058] The 5.0% additive consists of 1.0% silica fume, 1.0% nano-silica fume, and 3.0% Guangxi white clay; the 3.0% binder consists of 0.3% sodium tripolyphosphate, 0.7% sodium hexametaphosphate, 1% industrial glucose, 0.5% carboxymethyl cellulose, and 0.5% dextrin; the admixture is an explosion-proof fiber composed of polyethylene, polypropylene, and polyester fiber.

[0059] The high-purity magnesia sand used has a MgO content of ≥96.5%, SiO2 ≤0.9%, Fe2O3 ≤0.7%, and CaO ≤1.5%; the fused magnesia sand has a MgO content of ≥97.1%, SiO2 ≤0.7%, Fe2O3 ≤0.7%, and CaO ≤0.9%; the magnesia-zirconia powder has a MgO content of ≥4%, ZrO2 + HfO2 ≥94%, SiO2 ≤0.4%, and Fe2O3 ≤0.4%

[0060] The preparation method of the magnesia-zirconia coating material in the comparative example is the same as that in Example 1.

[0061] The coating material prepared in the comparative example was subjected to coating construction operations, and then the coating material was sampled for testing: the bulk density after drying at 110°C for 24 hours was 2.41 g / cm 3 , and the bulk density after heat treatment at 600°C for 3 hours was 2.47 g / cm 3, the bulk density is 2.53 g / cm³ after heat treatment at 1200°C for 3 h 3 ; the bulk density is 2.55 g / cm³ after heat treatment at 1400°C for 3 h 3 .

[0062] The magnesia-zirconia brick was cut into specimens of 40×40×60 mm, and the brick specimens were bonded with the coating material. After heat treatment at the corresponding temperature, the flexural strength of the bonded specimens was measured. The flexural strength was 2.3 MPa after drying at 110°C for 24 h; 1.4 MPa after heat treatment at 600°C for 3 h; 2.3 MPa after heat treatment at 1200°C for 3 h; and 3.1 MPa after heat treatment at 1400°C for 3 h.

Claims

1. A magnesia-zirconia ramming mix, characterized in that: In terms of mass percentage, the magnesia-zirconia ramming mix mainly consists of 54 - 65% aggregate, 25 - 36% powder, 4 - 7% additive, and 1 - 4% binder; in addition, an admixture accounting for 0.1 - 1% of the total weight of all raw materials is added. The 54 - 65% aggregate consists of 12 - 18% waste magnesia-zirconia bricks with a particle size of ≤3 mm, 22 - 29% recycled magnesia sand with a particle size of ≤3 mm, and 20 - 27% fused bauxite sand with a particle size of ≤3 mm. The 25 - 36% powder consists of 13 - 18% waste magnesia-zirconia bricks with a particle size of ≤0.037 mm, 8 - 13% recycled magnesia sand with a particle size of ≤0.088 mm, and 2 - 8% fused bauxite sand with a particle size of ≤0.088 mm.

2. The magnesia-zirconia ramming mix according to claim 1, characterized in that: The waste magnesia-zirconia bricks have an MgO content of ≥70% and ZrO2 + HfO2 ≥11%; the waste magnesia-zirconia bricks are directly crushed from recycled used magnesia-zirconia bricks into waste magnesia-zirconia bricks with a particle size of ≤3 mm and waste magnesia-zirconia bricks with a particle size of ≤0.037 mm.

3. The magnesia-zirconia ramming mix according to claim 1, characterized in that: The recycled magnesia sand has an MgO content of ≥95%, SiO2 ≤2%, Fe2O3 ≤1.5%, and CaO ≤2%; the recycled magnesia sand is obtained by classifying and sorting recycled used magnesia bricks, removing the working layer, crushing, soaking and cleaning, drying, cooling, secondary crushing, and screening, to obtain recycled magnesia sand with a particle size of ≤3 mm and recycled magnesia sand with a particle size of ≤0.088 mm.

4. The magnesia-zirconia ramming mix according to claim 1, characterized in that: The fused bauxite sand has an MgO content of ≥96%, SiO2 ≤0.7%, Fe2O3 ≤1.0%, and CaO ≤2.5%.

5. The magnesia-zirconia ramming mix according to claim 1, characterized in that: The additive consists of silica fume, nano-silica fume, and Guangxi white clay.

6. The magnesia-zirconia ramming mix according to claim 5, characterized in that: The mass ratio among the silica fume, nano-silica fume, and Guangxi white clay is 1 - 2:1 - 2:2 - 3.

7. The magnesia-zirconia ramming mix according to claim 1, characterized in that: The binder consists of sodium tripolyphosphate, sodium hexametaphosphate, industrial glucose, carboxymethyl cellulose, and dextrin.

8. The magnesia-zirconia ramming mix according to claim 7, characterized in that: The mass ratio among the sodium tripolyphosphate, sodium hexametaphosphate, industrial glucose, carboxymethyl cellulose, and dextrin is 5 - 7:5 - 7:8 - 12:3 - 7:3 - 7.

9. The magnesia-zirconia ramming mix according to claim 1, characterized in that: The admixture is an explosion-proof fiber mixed by polyethylene, polypropylene, and polyester fiber.

10. A preparation method of a magnesia-zirconia ramming mix, characterized in that, The preparation method includes the following steps: a. Weigh various raw materials according to the mixing ratio of the magnesia-zirconia ramming mix described in Claim 1. b. Add the weighed aggregate, powder, additive, binder, and admixture into a forced mixer for mixing. Stir for 5 - 10 minutes, then add tap water accounting for 5 - 10% of the total weight of all raw materials, and continue to stir forcibly for 5 - 8 minutes. Wait until the ramming mix becomes a mud paste and discharge it for standby.