CN114195529B - High-strength magnesia refractory mortar for refining ladle - Google Patents

High-strength magnesia refractory mortar for refining ladle Download PDF

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CN114195529B
CN114195529B CN202010978581.1A CN202010978581A CN114195529B CN 114195529 B CN114195529 B CN 114195529B CN 202010978581 A CN202010978581 A CN 202010978581A CN 114195529 B CN114195529 B CN 114195529B
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magnesia
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refractory
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strength
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CN114195529A (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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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • 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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    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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Abstract

The invention relates to high-strength magnesia refractory mortar for refining steel ladles, which comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of aluminum magnesium spinel fine powder and active alpha-Al 2 O 3 3 to 8 percent of micro powder and SiO 2 0.5 to 3 percent of micro powder and 1 to 5 percent of magnesium aluminate gel powder; sodium hexametaphosphate +0.2-0.6% and carboxymethyl cellulose +1-5%. The invention has good bonding strength, still has high strength, high temperature resistance and scouring resistance under the ladle refining process and high temperature condition, and solves the problem that the brick joint is most easily corroded in the ladle application.

Description

High-strength magnesia refractory mortar for refining ladle
Technical Field
The invention relates to a refining ladle refractory mortar, in particular to a high-strength magnesia refractory mortar suitable for building a refining ladle refractory brick.
Background
High quality steel is typically refined from molten steel and must be contained in a refining ladle. The steel ladle working lining is mostly built by refractory bricks, and commonly used refractory bricks comprise magnesia carbon bricks, aluminum magnesia carbon bricks, magnesia alumina carbon bricks, corundum prefabricated bricks and aluminum magnesium prefabricated bricks. The refractory bricks are bound by refractory clay to form a complete packing, if the performance of the refractory clay is poor, the refractory brick joints become the weakest link in the refining process, the brick joints are firstly eroded away by scouring, and the expansion of the packing wall bricks and the falling of the refractory bricks are important reasons for causing the infiltration of molten steel into the working lining or the steel ladle leakage accident.
Chinese patent CN105601305A discloses a novel magnesia refractory mortar and a preparation process thereof, wherein the mortar can be used for building magnesia carbon bricks, magnesia bricks and the like, and 1000 parts of magnesia fine powder (< 1 mm) and 6-15 parts of solid sintering agent are adopted. In order to have good strength, dextrin and borax are used as solid sintering agents, so that the problem that strength of fireclay is insufficient at high temperature due to the fact that brine is used as a bonding agent in the past is solved. The results obtained by the strength test are: the compressive strength after 110 ℃ for 24 hours is 4MPa, and the compressive strength after 800 ℃ for 3 hours is 18MPa. However, borax used in 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 unfavorable for corrosion resistance.
Chinese patent CN1074202A discloses 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-chromia refractory bricks of a steelmaking high-temperature refining furnace and overcomes the defect of low use temperature of the prior fireclay. The magnesia refractory slurry adopts magnesia (< 0.088)mm) 100 parts, magnesium sulfate 2.5-24 parts, and composite additive 0.5-5.0 parts. The results obtained by the strength test are: the flexural bond strength after 110 ℃ for 12 hours is 5.9-5.2 MPa, and the flexural bond strength after 1500 ℃ for 3 hours is 2.66-4.68 MPa. However, magnesium sulfate has a melting point of 865 ℃ and is in a low-melting phase, and the hydrolysis product of magnesium sulfate has sulfuric acid H 2 SO 4 Can react with metal and metal oxide in the material to generate hydrogen and water, so that the brick body is inflated, and the aluminium magnesia carbon brick or magnesia carbon brick for building the refining ladle is not beneficial.
Chinese patent CN101224986a describes a normal temperature high strength refractory slurry for dry quenching ovens, which mainly comprises silicon carbide, silicon nitride, dense corundum, mullite, alumina micropowder, refractory clay, and a composite additive comprising aluminum sulfate and an aluminum silica sol as binder. The fire-resistant slurry changes the condition of no strength of the same kind of fire slurry before baking, has higher normal temperature strength, and greatly improves the integrity of the fire-resistant masonry. The performance index detection result comprises: the flexural bond strength is 1.25-3.57 MPa after 1 day at normal temperature, and the flexural bond strength is 11.02-12.03 MPa after 1000 ℃. The refractory mortar is high-quality mortar with high bonding strength, but the use temperature is low, and the chemical property of the material does not meet the corrosion resistance requirement of a high-temperature kiln of a steel mill.
Therefore, development of refractory clay suitable for steelmaking process conditions and specific high-temperature furnaces is needed 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 clay for refining ladle, which has good bonding strength, still has high strength, high temperature resistance and scouring resistance under the ladle refining process and high temperature conditions, and solves the problem that brick joints are most easily corroded in ladle application.
The invention is realized in the following way:
the high-strength magnesia refractory mortar for the refining ladle comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of aluminum magnesium spinel fine powder and active alpha-Al 2 O 3 3 to 8 percent of micro powder and SiO 2 Micro powder 0.5-3% and aluminate1 to 5 percent of magnesium gel powder; sodium hexametaphosphate +0.2-0.6% and carboxymethyl cellulose +1-5%.
The MgO content of the magnesia is more than or equal to 96 percent.
The particle size distribution of the magnesite requires: the granularity is more than or equal to 0.2mm and less than 5%, and the granularity is less than or equal to 0.074mm and less than 20%.
The magnesia is sintered magnesia or fused magnesia.
The active alpha-Al 2 O 3 Al of micropowder 2 O 3 The content is more than or equal to 98 percent.
The active alpha-Al 2 O 3 The fineness of the micro powder is less than or equal to 1.5 mu m.
The SiO is 2 SiO of the micropowder 2 The content is more than or equal to 95 percent.
The SiO is 2 The fineness of the micro powder is less than or equal to 0.6 mu m.
MgO and Al of the magnesium aluminate gel powder 2 O 3 The total content is more than or equal to 85 percent.
The fineness of the magnesium aluminate gel powder is less than or equal to 0.074mm.
The high-strength magnesia refractory mortar for the refining ladle has the advantages that MgO in magnesia is taken as a main component and various fine powder is added from the chemical composition, the bonding performance of various refractory bricks (mainly relating to magnesia, aluminum and aluminum magnesia refractory bricks) for the masonry refining ladle is good, the strength is high, the high-temperature molten steel scouring resistance is good, the content of low-melting matters in the composition is less, the high-temperature resistance is good, the chemical composition is reasonable, the erosion resistance to high-temperature molten steel and alkaline slag is good, and meanwhile, the high-strength magnesia refractory mortar has good sintering property, compactness and molten slag permeability at high temperature. Aluminum magnesium spinel (MgO.Al) 2 O 3 ) The fine powder has good high temperature resistance, slag resistance and molten steel resistance superior to those of magnesia, and the erosion resistance and penetration resistance of the alumina magnesia spinel which is partially pre-synthesized can be enhanced at the initial stage of using the refractory clay. SiO (SiO) 2 The micropowder can react with MgO to form magnesium silicate hydrate (MgO.SiO) 2 .H 2 O) can increase the strength of the refractory clay at low temperature, can prevent the hydration of magnesia, and can reduce the water adding amount of the refractory clay, so that the refractory clay is sticky and has better construction performance. SiO (SiO) 2 The micropowder can also be mixed with MgO and MgO.SiO in the slag 2 Conversion to high melting forsterite 2MgO.SiO 2 And the phase ensures good erosion resistance of the refractory mortar. The magnesium aluminate gel powder is prepared from MgO and Al 2 O 3 As a main component, the ceramic solid bonding sintering agent can provide good cementing property after being added with water, is beneficial to improving the cementing property of various refractory bricks, can not generate low-melting phase matters at high temperature, and can strengthen the ceramic bonding of refractory clay.
Secondly, the grain size of the raw materials is controlled, so that better performance of the refractory mortar is obtained, and particularly, the using 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-Al 2 O 3 The fineness of the micro powder is controlled to be less than or equal to 1.5 mu m, so that alpha-Al 2 O 3 The micropowder reacts with MgO in the refractory clay in situ in the high-temperature application process to generate aluminum-magnesium spinel, so that the refractory clay is densified, shrinkage is reduced, the corrosion resistance is excellent, and simultaneously the alpha-Al 2 O 3 SiO in micropowder and refractory mortar 2 The micropowder reacts to form mullite (3 Al) 2 O 3 .2SiO 2 ) The mullite phase has good thermal shock property, so that the refractory clay is not easy to crack.
In addition, sodium hexametaphosphate is used as a water reducer, 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 enough construction time of the refractory mortar is ensured. The carboxymethyl cellulose plays a role in retaining water in the refractory clay, so that the refractory clay has enough construction kneading time in masonry, and the full masonry joint is ensured.
Compared with the prior art, the invention has the following beneficial effects: the adhesive property of the steel ladle refractory brick is better; the steel has better strength and 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 the refractory brick joints are obviously improved by the better permeation resistance, the steel ladle refractory accident is reduced, and the whole service life and the safety of the steel ladle are improved.
Detailed Description
The invention will be further illustrated with reference to specific examples.
The high-strength magnesia refractory mortar for the refining ladle comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of aluminum magnesium spinel fine powder and active alpha-Al 2 O 3 3 to 8 percent of micro powder and SiO 2 0.5 to 3 percent of micro powder and 1 to 5 percent of magnesium aluminate gel powder; sodium hexametaphosphate +0.2-0.6% and carboxymethyl cellulose +1-5%. The chemical components of the refractory clay are mainly MgO, and the refractory clay has good binding property, high strength and high-temperature molten steel scouring resistance for various refractory bricks, is low in content of low-melting matters in the composition, has good high-temperature resistance, has more reasonable chemical components of the refractory clay, 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 magnesia is sintered magnesia or fused magnesia, the MgO content of which is more than or equal to 96 percent, and the granularity distribution of the magnesia requires: the granularity is more than or equal to 0.2mm and less than 5%, and the granularity is less than or equal to 0.074mm and less than 20%. The refractory mortar is filled in the brick joints, critical granularity is not too large, the refractory mortar is packed most closely as much as possible, compaction is ensured, in addition, the refractory mortar needs to be added with water before construction application, if the granularity of magnesia is too fine, the refractory mortar is easy to hydrate, so that the magnesia is controlled within a reasonable proportion and range, and the stability of the refractory mortar is maintained.
The aluminum magnesium spinel fine powder has good high temperature resistance, slag resistance and molten steel resistance are superior to those of magnesia, and the erosion resistance and penetration resistance of the added partially pre-synthesized aluminum magnesium spinel can be enhanced at the initial stage of using the refractory clay. In the using process, the invention is alpha-Al 2 O 3 The micro powder and MgO which is the main component in the refractory clay also generate new aluminum magnesium spinel, so that the refractory clay has excellent erosion resistance.
Preferably, the active alpha-Al 2 O 3 Al of micropowder 2 O 3 The content is more than or equal to 98 percent, and the fineness is less than or equal to 1.5 mu m. Since the reactivity of the alumina micropowder is mainly expressed in fineness, if the fineness of the alumina micropowder is more than 3umActivated sintering of refractory clay and Al 2 O 3 The reaction rate with MgO is much reduced. And the fineness is controlled to be less than or equal to 1.5um of alpha-Al 2 O 3 The micropowder can react with MgO in situ in the refractory mortar to produce magnesia-alumina spinel (MgO Al) in the high temperature application process 2 O 3 ) The refractory clay is densified, and shrinkage of the refractory clay is reduced. At the same time due to alpha-Al 2 O 3 The micro powder has good activity and can also be used for mixing with SiO in refractory clay 2 The micropowder reacts to form mullite (3 Al) 2 O 3 .2SiO 2 ) The mullite has good phase thermal shock property, so that the refractory clay is not easy to crack.
Preferably, the SiO 2 SiO of the micropowder 2 The content is more than or equal to 95 percent, and the fineness is less than or equal to 0.6 mu m. SiO (SiO) 2 The micro powder can react with MgO which is the main component in the refractory mortar to generate MgO.SiO 2. H 2 O combines to form magnesium silicate hydrate, which increases the strength of the fire clay at low temperature, can prevent the hydration of magnesia, reduces the water adding amount of the fire clay, and ensures that the fire clay is sticky and has better workability. But if SiO 2 The excessive addition of the micro powder can cause the reduction of the high temperature resistance of the magnesia refractory mortar, so that the addition amount is controlled to be not more than 3 percent. In addition, siO 2 The micropowder can also be mixed with MgO in MgO and slag to obtain MgO.SiO in MgO slag 2 Conversion to high melting forsterite 2MgO.SiO 2 And the phase ensures good erosion resistance of the refractory mortar. The specific chemical reaction equation is as follows:
SiO 2 +2MgO----2MgO.SiO 2
MgO.SiO 2 +MgO----2MgO.SiO 2
preferably, mgO and Al of the magnesium aluminate gel powder 2 O 3 The sum of the contents is more than or equal to 85 percent, and the fineness of the magnesium aluminate gel powder is less than or equal to 0.074mm. The magnesium aluminate gel powder is a ceramic fixing and combining sintering agent, has good cementing property after being added with water, and is very beneficial to bonding various refractory bricks. In addition, the magnesium aluminate gel powder does not generate low-melting phases at high temperature, and can effectively strengthen the ceramic bonding of the refractory clay. Therefore, the magnesium aluminate gel powder is beneficial to improving the strength and the bonding performance of the refractory mortar, and avoids the prior art of resisting the fireThe fireclay contains the defect of low-melting point sintering binder. In addition, the existing part of refractory clay adopts liquid sol, but the field environment temperature of a steel mill is high, and the liquid sol is easy to fail and is not beneficial to storage, so the magnesium aluminate gel powder adopted by the invention can avoid the problem.
Sodium hexametaphosphate is added as a water reducing agent in the invention. A large amount of water is needed to be added before the refractory mortar is applied in construction, and on the premise of ensuring the workability, the smaller the water addition amount is, the better the compactness and the strength of the refractory mortar are. Therefore, water reducing agents, commonly used as polyphosphates and polycarboxylates, need to be added to reduce the amount of water added during construction. However, the invention is magnesium refractory clay containing MgO.SiO after construction 2. H 2 O system hydration products, researches show that the polycarboxylate water reducer has no influence on the control of the hydration speed of magnesia refractory mortar in the system, and sodium hexametaphosphate can be used as the water reducer to adjust the hydration speed of materials, mainly because the sodium hexametaphosphate is Mg 2+ The complexing agent can form a stable complex to wrap the surface of MgO particles, so that the retarding effect is achieved, the better water reducing effect is achieved, meanwhile, the hardening speed of the refractory mortar is controllable, and the enough construction time of the refractory mortar is ensured.
According to the invention, the carboxymethyl cellulose is additionally added, and the carboxymethyl cellulose plays a role in retaining water in the refractory clay, so that the refractory clay has enough construction kneading time during masonry, and the full masonry joint is ensured.
The high-strength magnesia refractory mortar for the refining ladle comprises the following concrete preparation method: weighing the raw materials and the additive according to the weight percentage, adding water into the stirrer, fully and uniformly stirring, packaging and bagging to obtain the refractory clay finished product.
Table 1 shows the specific weight percentages (wt%) of the raw materials of examples 1 to 5.
TABLE 1
Examples 1 to 5 were stirred into slurry according to the proportions of the raw materials and the additives shown in table 1, and adhered to refractory bricks for ladles, and physicochemical properties and related technical indexes of the refractory slurry were tested according to the national or industrial refractory material test method. Specifically, the bond flexural strength was tested according to GB/T22459.4 method, the line change rate after firing was tested according to GB/T5988 method, the refractoriness was tested according to GB/T7322 method, and the chemical composition analysis was tested according to GB/T5069 method.
Table 2 shows the specific physicochemical properties and related technical indexes of examples 1 to 5 and comparative examples (existing ladle refractory mortar). Wherein, the bonding breaking strength test adopts ladle magnesia carbon brick bonding.
TABLE 2
As can be seen from Table 2, the bonding flexural strength of examples 1-5 at different temperatures is obviously improved, the line shrinkage after firing at high temperature is reduced, the better high-temperature volume stability is shown, the refractoriness is improved to more than 1800 ℃, and the ultra-high-temperature smelting condition of the refining ladle can be resisted. Thus, the present invention performs better in all aspects of physicochemical properties.
The high-strength magnesia refractory mortar for refining the steel ladle adopts the combination of a plurality of bonding technologies, avoids sintering bonding agents of low-melting matters, has better bonding performance on various refractory bricks for the steel ladle, and has better strength at each temperature stage in the application process. The invention has good construction performance, compactness, viscosity and good bonding performance after adding water, and the key performances of bonding strength, refractoriness and shrinkage are superior to those of the prior refractory clay, thereby ensuring that the refractory clay can provide excellent application effect, improving the integrity of the steel ladle, reducing the abnormal phenomena of cracks of a working lining of the steel ladle, cold steel infiltration and the like, and ensuring the whole service life and safety of the steel ladle.
The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention, therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (2)

1. A high-strength magnesia refractory mortar for refining steel ladles is characterized in that: the refractory clay comprises the following raw materials in percentage by weight: 79-87% of magnesia, 5-10% of aluminum magnesium spinel fine powder and active alpha-Al 2 O 3 3.5 to 8 percent of micro powder and SiO 2 0.5 to 3 percent of micro powder and 1 to 5 percent of magnesium aluminate gel powder; sodium hexametaphosphate +0.2-0.6% and carboxymethyl cellulose +1-5%;
the magnesite is sintered magnesite or fused magnesite, and the granularity distribution of the magnesite requires: less than 5% of granularity more than or equal to 0.2mm and less than 20% of granularity less than or equal to 0.074mm;
MgO and Al of the magnesium aluminate gel powder 2 O 3 The sum of the contents is more than or equal to 85 percent, and the fineness of the magnesium aluminate gel powder is less than or equal to 0.074mm;
the active alpha-Al 2 O 3 Al of micropowder 2 O 3 The content is more than or equal to 98 percent, and the activity alpha-Al 2 O 3 The fineness of the micro powder is less than or equal to 1.5 mu m;
the SiO is 2 SiO of the micropowder 2 The content is more than or equal to 95 percent, siO 2 The fineness of the micro powder is less than or equal to 0.6 mu m.
2. The high-strength magnesia refractory mortar for refining ladles as set forth in claim 1, wherein: the MgO content of the magnesia is more than or equal to 96 percent.
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