CN114195529A - High-strength magnesium refractory mortar for refining steel ladle - Google Patents

High-strength magnesium refractory mortar for refining steel ladle Download PDF

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CN114195529A
CN114195529A CN202010978581.1A CN202010978581A CN114195529A CN 114195529 A CN114195529 A CN 114195529A CN 202010978581 A CN202010978581 A CN 202010978581A CN 114195529 A CN114195529 A CN 114195529A
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refractory mortar
strength
equal
magnesia
refining
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CN114195529B (en
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甘菲芳
舒友亮
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/66—Monolithic refractories or refractory mortars, including those whether or not containing clay
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
    • B22D41/02—Linings
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Abstract

The invention relates to high-strength magnesium refractory mortar for a refining ladle, which comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of magnesia alumina spinel fine powder and active alpha-Al2O33-8% of micro powder and SiO20.5-3% of micro powder and 1-5% of magnesium aluminate gel powder; and 0.2-0.6% of sodium hexametaphosphate and 1-5% of carboxymethyl cellulose are added. The invention has good bonding strength, still has high strength, high temperature resistance and erosion resistance under the conditions of ladle refining process and high temperature, and solves the problem that brick joints are most easily eroded in the application of the ladle.

Description

High-strength magnesium refractory mortar for refining steel ladle
Technical Field
The invention relates to refining ladle refractory mortar, in particular to high-strength magnesium refractory mortar suitable for building refining ladle refractory bricks.
Background
High quality steel is usually refined from molten steel and must be contained in a refining ladle. The ladle working lining is mostly built by refractory bricks, and the commonly used refractory bricks comprise magnesia carbon bricks, alumina-magnesia carbon bricks, magnesia-alumina carbon bricks, corundum prefabricated bricks and alumina-magnesia prefabricated bricks. The refractory bricks are bonded by refractory mortar to form a complete ladle lining, if the performance of the refractory mortar is poor, refractory brick seams in the refining process become the weakest link, the brick seams are firstly eroded by scouring, the ladle wall bricks are expanded, and the refractory bricks fall off, which is an important reason for the penetration of molten steel into the working lining or the leakage of a ladle.
Chinese patent CN105601305A discloses a novel magnesia refractory fire clay and a preparation process thereof, wherein the fire clay can be used for building magnesia carbon bricks, magnesia bricks and the like, and the fire clay adopts 1000 parts of magnesia fine powder (less than 1 mm) and 6-15 parts of solid sintering agent. In order to have good strength, dextrin and borax are used as solid sintering agents, so that the problem of insufficient strength of the fire clay at high temperature caused by the fact that brine is used as a binding agent in the prior art is solved. The strength test results show that: the compressive strength was 4MPa at 110 ℃ for 24 hours and 18MPa at 800 ℃ for 3 hours. However, the borax adopted by the fire clay is a low-melting-point sintering agent, which may cause the high-temperature resistance of the fire clay to be reduced, and is not beneficial to corrosion resistance.
Chinese patent CN1074202A discloses a magnesia refractory slurry which takes magnesia as a main raw material and magnesium sulfate as a bonding agent, has higher high-temperature bonding strength, can be used for magnesia, magnesia-alumina and magnesia-chrome refractory bricks of a steelmaking high-temperature refining furnace kiln, and overcomes the defect of low use temperature of the prior fire clay. The magnesia refractory slurry adopts 100 parts of magnesia (less than 0.088 mm), 2.5-24 parts of magnesium sulfate and 0.5-5.0 parts of composite additive. The strength test results show that: the flexural strength of the adhesive is 5.9-5.2 MPa after being multiplied by 12 hours at 110 ℃, and the flexural strength of the adhesive is 2.66-4.68 MPa after being multiplied by 3 hours at 1500 ℃. However, magnesium sulfate has a melting point of 865 ℃ and is a low-melting phase, and the hydrolysis product of magnesium sulfate is sulfuric acid H2SO4Can react with metal and metal oxide in the material to generate hydrogen and water, so that the brick body is expanded, and is not beneficial to building the alumina-magnesia-carbon brick or magnesia-carbon brick of the refining ladle.
Chinese patent CN101224986A describes a normal temperature high strength refractory mortar for a dry quenching furnace, which mainly comprises silicon carbide, silicon nitride, dense corundum, mullite, alumina micro powder, refractory clay, and a composite additive containing aluminum sulfate and aluminum-silicon sol as a binding agent. The refractory mortar changes the situation that similar fire clay has no strength before being baked, has higher normal temperature strength, and greatly improves the integrity of the refractory masonry. The performance index detection result comprises the following steps: the flexural bonding strength of the adhesive is 1.25-3.57 MPa after 1 day at normal temperature, and the flexural bonding strength of the adhesive is 11.02-12.03 MPa after 1000 ℃. The refractory mortar is high-quality fire clay with high bonding strength, but the use temperature is low, and the chemical properties of the material also do not meet the anti-corrosion requirement of a high-temperature furnace kiln of a steel mill.
Therefore, it is necessary to develop a refractory mortar suitable for steel-making process conditions and specific high-temperature furnaces and kilns to meet the performance requirements of high strength, high temperature resistance, scouring resistance and the like.
Disclosure of Invention
The invention aims to provide high-strength magnesia refractory mortar for refined steel ladles, which has good bonding strength, still has high strength, high temperature resistance and scouring resistance under the refining process and high temperature condition of the steel ladles and solves the problem that brick joints are most easily eroded in the application of the steel ladles.
The invention is realized by the following steps:
the high-strength magnesium refractory mortar for the refining ladle comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of magnesia alumina spinel fine powder and active alpha-Al2O33-8% of micro powder and SiO20.5-3% of micro powder and 1-5% of magnesium aluminate gel powder; and 0.2-0.6% of sodium hexametaphosphate and 1-5% of carboxymethyl cellulose are added.
The MgO content of the magnesite is more than or equal to 96 percent.
The particle size distribution requirement of the magnesite is as follows: the granularity is more than or equal to 0.2mm and less than 5 percent, and the granularity is less than or equal to 0.074mm and less than 20 percent.
The magnesite is sintered magnesite or fused magnesite.
The active alpha-Al2O3Micronized Al2O3The content is more than or equal to 98 percent.
The active alpha-Al2O3The fineness of the micro powder is less than or equal to 1.5 mu m.
The SiO2Micronized SiO2The content is more than or equal to 95 percent.
The SiO2The fineness of the micro powder is less than or equal to 0.6 mu m.
MgO and Al of the magnesium aluminate gel powder2O3The total content is more than or equal to 85 percent.
The fineness of the magnesium aluminate gel powder is less than or equal to 0.074 mm.
The invention relates to a high-strength magnesia refractory mortar for a refined steel ladle, which is prepared by adding various fine powder micro-powders into MgO in magnesia mainly according to the chemical compositionThe refractory bricks for various masonry refining ladles (mainly relating to magnesium, aluminum and aluminum-magnesium refractory bricks) have the advantages of good bonding property, high strength, good high-temperature molten steel scouring resistance, few low-melting substances in compositions, good high-temperature resistance, reasonable chemical components, good erosion resistance to high-temperature molten steel and alkaline slag, and good sintering property, compactness and molten slag permeability resistance at high temperature. Magnesium aluminate spinel (MgO. Al)2O3) The fine powder has good high temperature resistance, the slag resistance and the molten steel penetration resistance are better than those of magnesia, and the erosion resistance and the penetration resistance of the refractory mortar can be enhanced by adding part of the presynthesized aluminum-magnesium spinel at the initial use stage. SiO 22The micropowder can react with MgO to produce magnesium silicate hydrate (MgO2.H2O), can increase the intensity of fire clay at low temperature, also can prevent the hydration of magnesia, can also reduce the water yield that adds of fire clay for the fire clay is thick, and the workability is better. SiO 22The micropowder can also be mixed with MgO and MgO-SiO in slag2Conversion to forsterite 2mgo2And the refractory mortar is ensured to have good erosion resistance. The magnesium aluminate gel powder is made of MgO and Al2O3As a ceramic solid bonding sintering agent, the ceramic solid bonding sintering agent can provide good cementation property after being added with water, is beneficial to improving the caking property of various refractory bricks, can not generate low-melting phase substances at high temperature, and can strengthen the ceramic bonding of refractory clay.
Secondly, the granularity of the raw materials is controlled, so that better performance of the refractory mortar is facilitated to be obtained, and particularly, the use fineness of the magnesia is controlled in a reasonable proportion and range, so that the stability of the refractory mortar can be maintained; active alpha-Al2O3The fineness of the micro powder is controlled to be less than or equal to 1.5 mu m, so that alpha-Al2O3The micro powder and MgO in the refractory mortar react in situ to generate the magnesia-alumina spinel in the high-temperature application process, so that the refractory mortar is densified, the shrinkage is reduced, the erosion resistance is excellent, and simultaneously, the alpha-Al2O3SiO in micropowder and refractory mortar2Micro powder reaction to produce mullite (3 Al)2O3.2SiO2) The mullite phase has good thermal shock property, so that the refractory mortar is not easy to crack.
In addition, sodium hexametaphosphate is used as a water reducing agent, a stable complex can be formed to wrap the surface of MgO particles, a retarding effect is achieved, the hydration rate of the refractory mortar can be effectively adjusted, the hardening speed of the refractory mortar is controllable, and the sufficient construction time of the refractory mortar is ensured. The carboxymethyl cellulose plays a role in water retention in the refractory mortar, so that the refractory mortar has enough construction kneading time during building, and full building joints are ensured.
Compared with the prior art, the invention has the following beneficial effects: the adhesive has better adhesive property to various refractory bricks used for the steel ladle; the alloy has better strength and good high-temperature resistance in each temperature stage, and can resist the erosion of molten steel and slag; the shrinkage is small, the compactness is good, the weak links of refractory brick seams are obviously improved due to better anti-permeability performance, steel ladle refractory accidents are reduced, and the overall service life and safety of the steel ladle are improved.
Detailed Description
The present invention will be further described with reference to the following specific examples.
The high-strength magnesium refractory mortar for the refining ladle comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of magnesia alumina spinel fine powder and active alpha-Al2O33-8% of micro powder and SiO20.5-3% of micro powder and 1-5% of magnesium aluminate gel powder; and 0.2-0.6% of sodium hexametaphosphate and 1-5% of carboxymethyl cellulose are added. As various refractory bricks for building refined steel ladles mainly relate to magnesium, aluminum and magnesium-aluminum refractory bricks, the service temperature exceeds 1600 ℃, the chemical components of the refractory mortar of the invention mainly comprise MgO, the refractory mortar has good bonding performance, high strength and good high-temperature molten steel scouring resistance for various refractory bricks, and the compositions have few low-melting matters and good high-temperature resistance, and the refractory mortar has more reasonable chemical components, good molten steel and alkaline slag erosion resistance at high temperature, good sintering property and good compactness and can effectively resist the penetration of molten slag.
Preferably, the magnesite is sintered magnesite or fused magnesite, the MgO content of the magnesite is more than or equal to 96%, and the granularity distribution requirement of the magnesite is as follows: the granularity is more than or equal to 0.2mm and less than 5 percent, and the granularity is less than or equal to 0.074mm and less than 20 percent. Because the refractory mortar is filled in brick joints, the critical granularity is not too large, the refractory mortar is closest to be stacked to ensure compactness, and in addition, water needs to be added into the refractory mortar before construction application, and if the granularity of the magnesia is too fine, the magnesia is easy to hydrate, so that the magnesia is controlled in a reasonable proportion and range, and the stability of the refractory mortar is favorably maintained.
The fine powder of the aluminum-magnesium spinel has good high temperature resistance, the slag resistance and the molten steel penetration resistance are superior to those of magnesia, and the erosion resistance and the penetration resistance of the aluminum-magnesium spinel added with part of pre-synthesized aluminum-magnesium spinel can be enhanced at the initial use stage of the refractory mortar. In the using process of the invention, alpha-Al2O3The main component MgO in the micro powder and the refractory mortar also generates new magnesia alumina spinel, so that the refractory mortar has excellent erosion resistance.
Preferably, the active α -Al2O3Micronized Al2O3The content is more than or equal to 98 percent, and the fineness is less than or equal to 1.5 mu m. Because the reaction activity of the alumina micro powder is mainly reflected on the fineness of the alumina micro powder, if the fineness of the alumina micro powder is more than 3um, the refractory mortar is activated and sintered and Al is added2O3The reaction rate with MgO is much reduced. And the fineness is controlled to be less than or equal to 1.5um2O3The micro powder can react with MgO which is the main component in the refractory mortar in situ to generate magnesia-alumina spinel (MgO2O3) So as to densify the refractory mortar and reduce the shrinkage of the refractory mortar. Meanwhile, due to alpha-Al2O3The micro powder has good activity and can be mixed with SiO in the refractory mortar2Micro powder reaction to produce mullite (3 Al)2O3.2SiO2) And the mullite phase has good thermal shock property, so that the refractory mortar is not easy to crack.
Preferably, the SiO2Micronized SiO2The content is more than or equal to 95 percent, and the fineness is less than or equal to 0.6 mu m. SiO 22The micro powder can react with MgO which is the main component in the refractory mortar to generate MgO2.H2And O is combined to form a magnesium silicate hydrate, so that the strength of the refractory mortar at low temperature is improved, the hydration of magnesia can be prevented, the water adding amount of the refractory mortar is reduced, the refractory mortar is viscous, and the construction performance is better. But if SiO2If the addition amount of the micro powder is too much, the high temperature resistance of the magnesium refractory mortar is reduced, so that the addition amount of the micro powder is controlled to be not more than 3%. In addition, SiO2The micro powder can also be mixed with MgO and MgO in slag in the application process2Conversion to forsterite 2mgo2And the refractory mortar is ensured to have good erosion resistance. The specific chemical reaction equation is as follows:
SiO2+2MgO----2MgO.SiO2
MgO.SiO2+MgO----2MgO.SiO2
preferably, MgO and Al of the magnesium aluminate gel powder2O3The total content is more than or equal to 85 percent, and the fineness of the magnesium aluminate gel powder is less than or equal to 0.074 mm. The magnesium aluminate gel powder is a ceramic fixed combination sintering agent, has good cementation property after being added with water, and is very beneficial to bonding various refractory bricks. In addition, the magnesium aluminate gel powder does not produce low-melting phase at high temperature, and can effectively strengthen the ceramic combination of the refractory mortar. Therefore, the magnesium aluminate gel powder is beneficial to improving the strength and the bonding property of the refractory mortar, and the defect that the refractory mortar contains a low-melting-point sintering bonding agent in the prior art is overcome. In addition, the existing part of refractory mortar adopts liquid sol, but the temperature of the site environment of a steel mill is high, and the liquid sol is easy to lose efficacy and is not beneficial to storage, so the problem can be avoided by adopting the magnesium aluminate gel powder.
In the invention, sodium hexametaphosphate is added as a water reducing agent. A large amount of water needs to be added before the construction application of the refractory mortar, and on the premise of ensuring the construction performance, the smaller the water addition amount is, the better the refractory mortar is, so that the compactness and the strength of the refractory mortar are better. Therefore, a water reducing agent is required to be added to reduce the water adding amount in construction, and common water reducing agents are polyphosphate and polycarboxylate. However, the invention is the magnesia refractory mortar which contains MgO2.H2The research on the hydration product of the O system shows that the polycarboxylic acid water reducing agent in the system has no influence on the control of the hydration speed of the magnesium refractory mortar, and the sodium hexametaphosphate as the water reducing agent can adjust the hydration rate of the material, mainly because the sodium hexametaphosphate is Mg2+The complexing agent can form a stable complex to wrap the surface of the MgO particles, so that the retarding effect is realized, a better water reducing effect is realized, the hardening speed of the refractory mortar is controllable, and the sufficient construction time of the refractory mortar is ensured.
In the invention, the carboxymethyl cellulose is added to play a role in retaining water in the refractory mortar, so that the refractory mortar has enough construction kneading time during building, and full building joints are ensured.
The preparation method of the high-strength magnesia refractory mortar for the refining ladle comprises the following steps: weighing the raw materials and the additive according to the weight percentage, adding water into the mixture, fully and uniformly stirring the mixture in a stirrer, and packaging and bagging the mixture to obtain the finished product of the refractory mortar.
Table 1 shows the specific weight percentages (wt%) of the starting materials of examples 1-5.
TABLE 1
Figure 493313DEST_PATH_IMAGE001
In the embodiments 1 to 5, the raw materials and the additives in the table 1 are mixed into slurry, the slurry is bonded on the refractory brick for the ladle, and the physical and chemical properties and related technical indexes of the refractory mortar are tested according to the national or industrial refractory material test method. Specifically, the bonding rupture strength is tested according to the GB/T22459.4 method, the linear change rate after burning is tested according to the GB/T5988 method, the refractoriness is tested according to the GB/T7322 method, and the chemical composition analysis is tested according to the GB/T5069 method.
Table 2 shows the specific physical and chemical properties and related technical indexes of the refractory mortar of examples 1-5 and comparative examples (the conventional refractory mortar for ladles). Wherein, the bonding rupture strength test adopts the bonding of the ladle magnesia carbon brick.
TABLE 2
Figure 901161DEST_PATH_IMAGE002
As can be seen from Table 2, in examples 1 to 5, the bonding flexural strength is significantly improved at different temperatures, the linear shrinkage is reduced after firing at high temperature, better high-temperature volume stability is shown, the refractoriness is improved to more than 1800 ℃, and the smelting conditions of the refining ladle at ultrahigh temperature can be resisted. Thus, the physicochemical properties of the present invention in all aspects are better exhibited.
The high-strength magnesium refractory mortar for the refining ladle adopts the combination of multiple combination technologies, avoids the sintering bonding agent of low-melting substances, has better bonding performance to various refractory bricks for the ladle, and has better strength at each temperature stage in the application process. The invention has good construction performance, compactness, viscosity and bonding performance after being added with water, and key performances of bonding strength, refractoriness and shrinkage are superior to those of the existing refractory mortar, thereby ensuring that the refractory mortar can provide excellent application effect, improving the integrity of the steel ladle, reducing abnormal phenomena of steel ladle working lining cracks, cold-infiltrated steel and the like, and ensuring the integral service life and safety of the steel ladle.
The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The high-strength magnesia refractory mortar for the refining ladle is characterized in that: the refractory mortar comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of magnesia alumina spinel fine powder and active alpha-Al2O33-8% of micro powder and SiO20.5-3% of micro powder and 1-5% of magnesium aluminate gel powder; and 0.2-0.6% of sodium hexametaphosphate and 1-5% of carboxymethyl cellulose are added.
2. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: the MgO content of the magnesite is more than or equal to 96 percent.
3. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: the particle size distribution requirement of the magnesite is as follows: the granularity is more than or equal to 0.2mm and less than 5 percent, and the granularity is less than or equal to 0.074mm and less than 20 percent.
4. A high strength magnesia refractory mortar for refining ladles according to any one of claims 1 to 3, characterized in that: the magnesite is sintered magnesite or fused magnesite.
5. The method of claim 1The high-strength magnesium refractory mortar for the refining ladle is characterized in that: the active alpha-Al2O3Micronized Al2O3The content is more than or equal to 98 percent.
6. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: the active alpha-Al2O3The fineness of the micro powder is less than or equal to 1.5 mu m.
7. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: the SiO2Micronized SiO2The content is more than or equal to 95 percent.
8. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: the SiO2The fineness of the micro powder is less than or equal to 0.6 mu m.
9. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: MgO and Al of the magnesium aluminate gel powder2O3The total content is more than or equal to 85 percent.
10. The high-strength magnesium refractory mortar for refining ladles according to claim 1, wherein: the fineness of the magnesium aluminate gel powder is less than or equal to 0.074 mm.
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