Magnesia gunning mix with Al and Ti intermetallic compound as high temperature main binding phase and its preparation method

Abstract

The application discloses a magnesia gunning mix with Al and Ti intermetallic compound as a high-temperature main bonding phase and a preparation method thereof. The magnesia gunning mix is used in an environment at 1500-1800 DEG C, and a generated bonding phase in situ is mainly composed of Al-Ti intermetallic compound. The magnesia gunning mix is mainly composed of refractory aggregate, powder and anhydrous carbonaceous organic binder; the refractory aggregate is composed of medium-grade magnesia, silicon carbide and amorphous carbon; and the refractory powder is composed of fused magnesia, calcined alumina powder, white corundum powder, silicon carbide powder, amorphous carbon powder and Al and Ti containing composite fine powder. The Al and Ti containing composite fine powder is mixed and treated with the calcined alumina powder to obtain a composite metal powder; the aggregate and part of the binder are mixed and ground, then the remaining powder, the composite metal powder and the remaining binder are added to continue mixing and grinding; and the obtained mix is sequentially subjected to material storage and extrusion molding to obtain a magnesia-carbon gunning mix block for a submerged arc furnace. The Al-Ti metal system is introduced to successfully construct a high-temperature bonding phase mainly composed of Al-Ti intermetallic compound in the magnesia gunning mix, and the comprehensive performance of the material is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of monolithic refractory materials for metallurgy, specifically to a magnesia-based taphole clay for use in the tapping / slag opening of submerged arc furnaces (including ferroalloy furnaces, calcium carbide furnaces, yellow phosphorus furnaces, etc.) and its preparation method. In particular, it relates to a high-performance magnesia-based taphole clay using Al and Ti intermetallic compounds as the high-temperature main bonding phase and its preparation method, i.e., a magnesia-based taphole clay with Al and Ti intermetallic compounds as the high-temperature main bonding phase and its preparation method. Background Technology

[0002] Submerged arc furnaces are used to produce ferroalloys, calcium carbide, yellow phosphorus, and industrial silicon. The operating conditions at the tapping / slag opening are harsh, requiring the taphole clay to withstand the scouring of high-temperature molten metal (1500–1800℃), alkaline slag erosion, and frequent tapping and plugging operations. Magnesia-carbon refractories are considered ideal for tapping submerged arc furnaces due to the high melting point (2800℃) of magnesia (MgO) and its strong resistance to alkaline slag erosion. Furthermore, the use of magnesia-carbon refractories in the slag / tap area has become mainstream.

[0003] However, the main technical bottlenecks of traditional magnesia gunning mud are: 1) Difficulty in sintering: Pure MgO is difficult to fully sinter and densify at the tapping temperature of an electric arc furnace, resulting in a loose structure and insufficient resistance to erosion; 2) Poor thermal shock stability: Magnesia has a large coefficient of thermal expansion, and is prone to cracking or even peeling when the temperature changes rapidly; 3) Single bonding phase: The carbon bond formed after the carbonization of traditional binders (such as tar and resin) is easily oxidized at high temperatures, while ceramic bonds (such as magnesium aluminum spinel) have high formation temperature and high brittleness.

[0004] Metallic Al and Ti can react under a high-temperature reducing atmosphere to form various high-melting-point intermetallic compounds, such as TiAl3 (melting point 1340℃), TiAl (melting point 1460℃), and Ti3Al (melting point 1600℃). These compounds possess both metallic and covalent bond characteristics, exhibiting high hardness, high melting point, and fracture toughness superior to pure ceramics. Introducing them into magnesia-based gunning mud can form a reinforcing framework within the matrix, thus solving the aforementioned problems. Summary of the Invention

[0005] The technical problem this invention aims to solve is: addressing the combined issues of existing magnesia-based gunning clay, such as difficulty in sintering and densification, insufficient high-temperature strength, poor thermal shock resistance, and poor durability. This invention provides a magnesia-based gunning clay with Al and Ti intermetallic compounds as the main high-temperature bonding phases and its preparation method. The technical solution of this invention generates a reinforcing phase through in-situ reaction, thereby significantly improving the service performance of the magnesia-based gunning clay.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a magnesium-based gunning mud with Al and Ti intermetallic compounds as the main high-temperature bonding phases. When the magnesium-based gunning mud is used in an environment of 1500-1800℃, the bonding phase generated in situ is mainly composed of Al-Ti intermetallic compounds.

[0008] According to the above-mentioned magnesia-based gunning compound with Al and Ti intermetallic compounds as the main high-temperature bonding phase, expressed in parts by weight, the magnesia-based gunning compound mainly consists of 40-45 parts of refractory aggregate, 40-45 parts of refractory powder, and 10-20 parts of anhydrous carbonaceous organic binder.

[0009] The refractory aggregate is composed of 15-20 parts of medium-grade magnesia (0.074-3mm), 1-10 parts of silicon carbide (0.074-1mm), and 5-15 parts of amorphous carbon (0.074-0.7mm).

[0010] The refractory powder is composed of 5-15 parts of fused magnesia (<0.074mm), 1-8 parts of calcined alumina powder (<0.044mm), 1-8 parts of white corundum powder (<0.044mm), 1-8 parts of silicon carbide powder (<0.074mm), 1-5 parts of amorphous carbon powder (<0.044mm), and 5-15 parts of Al and Ti composite fine powder (<0.074mm).

[0011] According to the above-mentioned magnesium-based gunning mud with Al and Ti intermetallic compounds as the high-temperature main bonding phase, the anhydrous carbonaceous organic binder is prepared by polycondensation reaction of sugar polyol and furfural, with a moisture content of <1.5%, residual carbon of 35-40%, volatilization at 200℃ of 15-20%, and viscosity at 50℃ of 600-650 mPa·s.

[0012] According to the above-mentioned magnesium-based clay with Al and Ti intermetallic compounds as the main high-temperature bonding phase, the sugar polyol is obtained by dehydrating maltitol syrup during maltitol production, and its main component is maltitol, with a maltitol concentration ≥95% and a moisture content <1.5%.

[0013] According to the above-mentioned magnesium-based gunning mud with Al and Ti intermetallic compounds as the main high-temperature bonding phases, the Al-Ti composite fine powder is formed by pre-mechanically alloying aluminum-containing fine powder and titanium-containing fine powder (in which some aluminum and titanium have formed a pre-alloyed layer).

[0014] According to the above-mentioned magnesium-based gunning mud with Al and Ti intermetallic compounds as the main high-temperature bonding phases, the aluminum-containing fine powder is a fine powder rich in aluminum collected during the pretreatment process of white-edge aluminum foil in the aluminum recycling process of waste lithium batteries. Its Al content is >90.0%, loss on ignition is <1.0%, Al2O3 content is 6.0-8.0%, and particle size is <0.074mm and >90%. The titanium-containing fine powder is a fine powder collected during the crushing and pulverizing process of sponge titanium processing into titanium ingots. Its Ti content is >95.0% and particle size is <0.074mm and >90%.

[0015] In addition, a method for preparing magnesian gunning mud with Al and Ti intermetallic compounds as the main high-temperature bonding phases is provided, comprising the following steps:

[0016] 1) First, weigh out all the raw materials according to the raw material composition of the magnesium-based gunning clay as described in claim 2;

[0017] 2) The Al and Ti composite fine powder is mixed with calcined alumina powder (placed in a high-speed mixer) to coat the surface of the metal powder with an alumina isolation layer, thereby obtaining composite metal powder;

[0018] 3) Add 78-82% of the total amount of anhydrous carbonaceous organic binder to the refractory aggregate and mix and grind it (in an oil-heated roller mill) to make the surface of the particles uniformly wetted.

[0019] 4) Then add the remaining powder and the composite metal powder obtained in step 2), and continue mixing and grinding;

[0020] 5) Next, add the remaining anhydrous carbonaceous organic binder and continue mixing until the mud has a bright cross-section, uniform texture, and good plasticity.

[0021] 6) The mud obtained from mixing and grinding (placed in a sealed container) is then allowed to settle;

[0022] 7) The trapped mud (sent into a mud extruder) is extruded into magnesia-carbon mud blocks for electric arc furnaces.

[0023] According to the above method for preparing magnesium-based gunning mud with Al and Ti intermetallic compounds as the high-temperature main bonding phase, the processing time in step 2) is 15-30 min; the mixing and rolling in step 3) is 5-10 min at 60-80℃; the mixing and rolling time in step 4) is 10-15 min; and the continued mixing and rolling time in step 5) is 10-15 min.

[0024] According to the above method for preparing magnesium-based gunning mud with Al and Ti intermetallic compounds as the main high-temperature bonding phases, the accumulator in step 6) is accumulating at 15–35°C for 24–48 hours.

[0025] The core of this invention lies in utilizing the high reactivity of Al and Ti metals at high temperatures. Under the thermal gradient at the tapping / slag opening of the submerged arc furnace, Al, with its lower melting point (660℃), melts first, wetting surrounding particles and activating the interface. As the temperature rises above 1000℃, Ti undergoes solid-liquid or solid-solid reactions with Al, generating dispersed Al-Ti intermetallic compounds. These compounds fill the spaces between magnesia clay particles, forming a network or dendritic bonded structure.

[0026] The raw material ratio of the magnesia-based gunning mud of this invention follows the following principle: the Al / Ti mass ratio is controlled at 1.2–2.8:1. When the Al / Ti ratio is high, it tends to form an aluminum-rich TiAl3 phase, which has a lower formation temperature and is beneficial for early strength development; when the Al / Ti ratio is low, it tends to form TiAl or TiAl3 phases, which have better high-temperature stability. By adjusting the ratio, the performance matching of different temperature ranges can be optimized.

[0027] The role of adding calcined alumina powder in the technical solution of this invention is that fine Al2O3 not only participates in spinelization reaction, but also adsorbs on the surface of metal powder during the mixing and grinding process, preventing premature oxidation and agglomeration.

[0028] The positive and beneficial effects of this invention are:

[0029] 1. Formation of a high-temperature reinforced skeleton: The magnesia gunning clay prepared by this invention generates high-melting-point Al-Ti intermetallic compounds (such as TiAl3, TiAl, etc.) in situ at service temperatures of 1500–1800℃, forming a composite structure of "particles + intermetallic compound bridging". This structure significantly improves the high-temperature flexural strength and resistance to melt erosion of the magnesia gunning clay; compared with conventional magnesia gunning clay, the high-temperature flexural strength can be increased by more than 50%.

[0030] 2. Improved sintering density: The liquid phase formed after the melting of metallic Al in the technical solution of this invention promotes particle rearrangement and sintering densification, reduces the sintering temperature of magnesia materials, and enables the taphole clay to achieve a high density at the tapping temperature of the submerged arc furnace.

[0031] 3. Optimized thermal shock stability: The intermetallic compound formed by the magnesium gunning clay of this invention at a service temperature of 1500-1800℃ has a certain plastic deformation capacity, which can absorb and buffer the thermal stress caused by rapid temperature changes and effectively inhibit crack propagation; thus, the thermal shock stability of the magnesium gunning clay prepared by this invention is 2-3 times higher than that of traditional gunning clay.

[0032] 4. Enhanced resistance to slag erosion: The dense intermetallic compound layer formed by the magnesium gunning clay at the service temperature of 1500-1800℃ in this invention blocks the penetration path of molten slag into the gunning clay. At the same time, the magnesium gunning clay matrix has a natural resistance to alkaline slag erosion. The synergistic effect of the two significantly extends the service life of the gunning clay.

[0033] 5. Adjustable opening performance: By adjusting the Al / Ti ratio and the total amount of metal powder, the technical solution of this invention can control the amount of intermetallic compounds generated, their distribution morphology and brittleness, so that the prepared magnesium-based stemming mud can open the iron mouth within a specified time, and the drill bit wear can be kept within a reasonable range, achieving a performance balance of "high temperature strengthening and low temperature drillability". Detailed Implementation

[0034] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solution of the present invention.

[0035] Example 1:

[0036] The present invention is a magnesia-based gun mortar with Al and Ti intermetallic compounds as the main high-temperature bonding phases, which, expressed in parts by weight, consists of 45 parts of refractory aggregate, 45 parts of refractory powder and 10 parts of anhydrous carbonaceous organic binder.

[0037] The refractory aggregate consists of 10 parts of medium-grade magnesia (3-1mm), 10 parts of medium-grade magnesia (1-0.074mm), 10 parts of silicon carbide (0.074-1mm), and 15 parts of amorphous carbon (0.074-0.7mm).

[0038] The refractory powder is composed of 15 parts of fused magnesia with a particle size of <0.074mm, 6 parts of calcined alumina powder with a particle size of <0.044mm, 5 parts of white corundum powder with a particle size of <0.044mm, 5 parts of silicon carbide powder with a particle size of <0.074mm, 3 parts of amorphous carbon powder with a particle size of <0.044mm, and 11 parts of Al and Ti composite fine powder with a particle size of <0.074mm; among the 11 parts of Al and Ti composite fine powder, there are 7 parts of 200-mesh aluminum fine powder and 4 parts of 200-mesh titanium fine powder.

[0039] The aluminum-containing fine powder is a fine powder rich in aluminum collected during the pretreatment process of white-edge aluminum foil in the aluminum recycling process of waste lithium batteries. Its Al content is >90.0%, loss on ignition <1.0%, Al2O3 content is 6.0-8.0%, and particle size <0.074mm >90%. The titanium-containing fine powder is a fine powder collected during the crushing and pulverizing stage of titanium ingot processing from sponge titanium. Its Ti content is >95.0%, and particle size <0.074mm >90%.

[0040] The anhydrous carbonaceous organic binder is prepared by polycondensation reaction of carbohydrate polyols and furfural, with a moisture content of <1.5%, residual carbon content of 35-40%, volatility of 15-20% at 200℃, and viscosity of 600-650 mPa·s at 50℃; the carbohydrate polyol is obtained by dehydration of maltitol syrup during maltitol production, and its main component is maltitol, with a maltitol concentration of ≥95% and a moisture content of <1.5%.

[0041] Example 2:

[0042] This invention uses Al and Ti intermetallic compounds as the main high-temperature bonding phases in a magnesium-based gun clay, which is basically the same as Example 1, except that:

[0043] Of the 11 parts of the Al and Ti composite fine powder, 6.6 parts are 200-mesh aluminum fine powder and 4.4 parts are 200-mesh titanium fine powder.

[0044] The detailed steps of the preparation method of magnesian gunning mud with Al and Ti intermetallic compounds as the high-temperature main bonding phases described in Examples 1-2 of this invention are as follows:

[0045] 1) First, weigh out all the raw materials according to the raw material composition of the magnesium-based gunning clay described in any of Examples 1-2;

[0046] 2) Place the Al and Ti composite fine powder and calcined alumina powder in a high-speed mixer and process them at 800 rpm for 20 minutes to coat the surface of the metal powder with an alumina isolation layer to obtain composite metal powder;

[0047] 3) Place all kinds of refractory aggregates in an oil-heated roller mill and heat them to 65°C. Then add 80% of the total amount of anhydrous carbonaceous organic binder and mix for 6 minutes to make the surface of the particles evenly wetted.

[0048] 4) Then add the remaining powder and the composite metal powder obtained in step 2), and continue mixing and grinding for 15 minutes;

[0049] 5) Next, add the remaining anhydrous carbonaceous organic binder and continue mixing and grinding at 70°C for 15 minutes until the mud has a bright cross-section, uniform texture, and good plasticity.

[0050] 6) Place the mud obtained from mixing and grinding in a sealed container and allow it to stand at 25°C for 24 hours;

[0051] 7) The trapped mud is extruded into φ120mm mud segments using a vacuum mud extruder, which is the magnesium carbonaceous gunning mud for electric arc furnaces.

[0052] The magnesia-carbon taphole clay prepared in Example 1 was tested after being heat-treated with carbon at 1500℃ for 3 hours. The apparent porosity was 13.2%, the bulk density was 2.48 g / cm³, the room temperature compressive strength was 32.3 MPa, and the high temperature flexural strength (1450℃) was 9.8 MPa. The slag erosion resistance test (static crucible method, ferronickel slag from ferroelectric furnace, 1500℃ for 2 hours) showed an erosion depth of 2.1 mm, which was significantly better than the control sample (conventional magnesia taphole clay, erosion depth 4.8 mm). XRD analysis showed that the main crystalline phase in the matrix was periclase, and the bonding phase was mainly TiAl3 and a small amount of TiAl. No obvious metallic elemental residues were detected.

[0053] The magnesium-carbon taphole clay for electric arc furnaces prepared in Example 2, after being fired at 1500℃, showed a slight increase in high-temperature flexural strength to 10.4 MPa, but a slight decrease in the opening drilling speed. This indicates that the proportion of TiAl phase generated increased, the brittleness decreased slightly, and the toughness improved.

[0054] Comparative Example 1:

[0055] It is basically the same as Example 1, except that: no titanium fine powder is added, only 11 parts of aluminum fine powder are added (the total amount of metal remains unchanged).

[0056] Performance testing of the magnesium-carbon taphole clay for submerged arc furnaces prepared using Comparative Example 1: After firing at 1500℃, the high-temperature flexural strength was only 5.6 MPa. SEM observation showed that no obvious intermetallic compound reinforcing phase was formed, and Al mainly existed in the form of alumina or spinel.

[0057] Industrial application trials:

[0058] The magnesium taphole clay prepared in Example 1 of this invention was subjected to an industrial test on a 25.5 MVA silicon-manganese alloy submerged arc furnace. The results showed that the tapping time was extended from an average of 90 minutes to 120 minutes; the taphole clay consumption was reduced by about 25%; the taphole opening was smooth, with no stuck drill or difficulty in opening; the taphole channel was stable, with no clay or slag leakage accidents.

[0059] As can be seen from the above embodiments and comparative examples, this invention successfully constructs a high-temperature bonding phase dominated by Al-Ti intermetallic compounds in magnesia-based gunning mud by introducing an Al-Ti metal system, significantly improving the overall performance of the material. Adjusting the Al / Ti ratio can optimize the matching of strength and toughness within a certain range, adapting to the usage requirements of submerged arc furnaces for smelting different products.

Claims

1. A magnesian gunning clay with Al and Ti intermetallic compounds as the main high-temperature bonding phases, characterized in that: When the magnesium-based gunning clay is used in an environment of 1500–1800℃, the in-situ generated bonding phase is mainly composed of Al-Ti intermetallic compounds.

2. The magnesium-based gunning mud according to claim 1, characterized in that: The magnesia-based gunning compound, expressed in parts by weight, is mainly composed of 40-45 parts of refractory aggregate, 40-45 parts of refractory powder, and 10-20 parts of anhydrous carbonaceous organic binder. The refractory aggregate is composed of 15-20 parts of medium-grade magnesia (0.074-3mm), 1-10 parts of silicon carbide (0.074-1mm), and 5-15 parts of amorphous carbon (0.074-0.7mm). The refractory powder is composed of 5-15 parts of fused magnesia (<0.074mm), 1-8 parts of calcined alumina powder (<0.044mm), 1-8 parts of white corundum powder (<0.044mm), 1-8 parts of silicon carbide powder (<0.074mm), 1-5 parts of amorphous carbon powder (<0.044mm), and 5-15 parts of Al and Ti composite fine powder (<0.074mm).

3. The magnesia-based gunning mud according to claim 2, characterized in that: The anhydrous carbonaceous organic binder is prepared by polycondensation reaction of sugar polyols and furfural, with a moisture content of <1.5%, residual carbon content of 35-40%, volatility of 15-20% at 200℃, and viscosity of 600-650 mPa·s at 50℃.

4. The magnesia-based gunning mud according to claim 3, characterized in that: The polyol is obtained by dehydrating maltitol syrup during maltitol production, and its main component is maltitol. The maltitol concentration is ≥95% and the moisture content is <1.5%.

5. The magnesia-based gunning mud according to claim 2, characterized in that: The Al-Ti composite fine powder is formed by pre-treating aluminum-containing fine powder and titanium-containing fine powder with mechanical alloying.

6. The magnesian gunning clay with Al and Ti intermetallic compounds as the high-temperature main bonding phase according to claim 5, characterized in that: The aluminum-containing fine powder is a fine powder rich in aluminum collected during the pretreatment process of white-edge aluminum foil in the aluminum recycling process of waste lithium batteries. Its Al content is >90.0%, loss on ignition is <1.0%, Al2O3 content is 6.0-8.0%, and particle size is <0.074mm and >90%. The titanium-containing fine powder is a fine powder collected during the crushing and pulverizing process of sponge titanium processing into titanium ingots. Its Ti content is >95.0% and particle size is <0.074mm and >90%.

7. A method for preparing magnesian gunning mud with Al and Ti intermetallic compounds as the main high-temperature bonding phases, characterized in that, Includes the following steps: 1) First, weigh out all the raw materials according to the raw material composition of the magnesium-based gunning clay as described in claim 2; 2) The Al and Ti composite fine powder is mixed with calcined alumina powder to coat the surface of the metal powder with an alumina isolation layer, thereby obtaining composite metal powder; 3) Add 78-82% of the total amount of anhydrous carbonaceous organic binder to the refractory aggregate and mix and grind it to make the surface of the particles uniformly wetted. 4) Then add the remaining powder and the composite metal powder obtained in step 2), and continue mixing and grinding; 5) Next, add the remaining anhydrous carbonaceous organic binder and continue mixing until the mud has a bright cross-section, uniform texture, and good plasticity. 6) The mud obtained from mixing and grinding is then subjected to a conditioning process; 7) Extrude the trapped mud into magnesia-carbon clay blocks for electric arc furnaces.

8. The method for preparing magnesian gunning mud with Al and Ti intermetallic compounds as the high-temperature main bonding phase according to claim 7, characterized in that: The processing time in step 2) is 15-30 min; the mixing and grinding in step 3) is 5-10 min at 60-80℃; the mixing and grinding time in step 4) is 10-15 min; and the continued mixing and grinding time in step 5) is 10-15 min.

9. The method for preparing magnesian gunning mud with Al and Ti intermetallic compounds as the high-temperature main bonding phase according to claim 7, characterized in that: The material being trapped in step 6) is trapped at 15–35°C for 24–48 hours.